g AmES \l‘llllllllllllsllllill“ 3 1293 010 9783 This is to certify that the thesis entitled PERSISTENCE AND VERTICAL MOVEMENT OF SELECTED PESTICIDES IN MICHIGAN POTATO FIELD presented by Eboua Narcisse Wandan has been accepted towards fulfillment of the requirements for MS degree in Entomology WM Maj rofessor Date 5/11/92 0-7639 MS U is an Affirmative Action/Equal Opportunity Institution MBBARV Mici'sigim State Usfiverslty PLACE IN RETURN BOX to romovo this checkout from your record. TO AVOID FINES Mum on or baton date duo. DATE DUE DATE DUE DATE DUE l r— JJ J + L 7m! l MSU Is An Afflrmathro ActlorVEqual Opportunlty Institution c.mpn3-pj PERSISI‘ENCE AND VERTICAL MOVEMENT OF SELECTED PESTICIDES IN MICHIGAN POTATO FIELD BY EBOUA NARCISSE WANDAN ATHESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Entomology 1992 £7.23 3 677- ABSTRACT '_._L I)! at“ [R] s- u. 1 ill-..“ .' ‘L .1 'P 11 1'95 L W BY EBOUA NARCISSE WANDAN The persistence and movement of pesticides in soil may result in their accumulation over long period of time and cause ground water contamination. A field experiment was designed to study the persistence of two herbicides, metolachlor and metribuzin and an organophosphate insecticide, imidan. The plots consisted of four rows planted with Burbank potatos; all treatments were replicated four times. The soil was sampled four times during the year and analyzed by gas chromatography to determine the concentration of the pesticides in the soil at various depths. No imidan was detected in the soil samples, indicating rapid dissipation. Metolachlor and metrihuzin were detected in all ' the soil samples even before the herbicides were applied. The levels found were low, therefore they should not persist in the soil over long period of time. The results also showed upward and downward movement of the two herbicides in the soil.- Reduction of irrigation may help reduce the potential for ground water contamination. To my uncle Alphonse K. Radio, for challenging me to attain the standard that he himself set to high. ACKNOWLEDGEMENTS I would first like to thank my major professor, Dr Matthew J. Zahik for his support and guidance during this project. His ideas and insights in how to solve problems and importantly how to fix ourselves materials have proven invaluable while his friendship has made me enjoy this cold weather of Michigan. I would like also to thank Drs D. Penner, G. Bird, and R. Hollingworth, for serving on my committee. Certainly The Government of Cote D’Ivoire, The African-American Institute, and Michigan State University deserve credit for allowing me to follow this program and providing me for their financial support. Two very close persons: Agathe Nemako and her Husband Prince deserve more gratitude than I can truly express. I would also like to express my heartfelt appreciation for my lab and office matest Gama], Glenn Dickman, El Hadidi, and Chris Vandervoot, their friendship and thank Bob Shultz for the movies. Most importantly, I would like to thank my mother, father for providing the love, support, and patience that I too often take for granted. They have taught me that success is the result or hard work, diligence and perseverance. Finally and most certainly, I would like to thank my lovely wife Brigitte and my son Miessan-Aka for their patience during the nights spent in the lab and for their love and support. iv TABLE OF CONTENTS LIST OF TABLES . . . . . . . . . . . . . . . . . . . viii Chapter Page I. EAcEGROUND OBJECTIVES . . . . . . . . . . . . 1 A. OR 8 ES . . . . . . . 1 B. BJ OP . . . . . . . . . . 3 II. REVIE' 0! LITERATURE . . . . . . . . . . . . . 4 1- W . . - . . . - 4 1. 8 E OC 8 . . . . . . . . . . . 5 a. EAETITION . . . . . . . . . . . . . . 6 b. AD§OB£I§ON . . . . . . . . . . . . . 6 c C ESQ!!OFF C C C O O O O O O O O O O O O 7 d. V0 ON 2. G 18” o o o . . o . 9 ‘0 O - on C G O o o o o o 9 D. G ON 0 O O O O I O 11 W- . . - . . - . - . - . 12 C. ORHA N ON 8 IC 38 . .13 1. EEIQLAQflLQB . o . . . . . . . . . . . . . 13 2. HEIELEQZIN . . . . . . . . . . . . . . . 14 3 I E 308MB! 0 O C C O O O I O O O O O O O O 16 D. E V OR T NV RONM . . . . . . . . 20 Chapter III. IV. NATERIALS AND.NETEDDS . . . . . . . . . . . 3. EQUIPMENT 0 O O O O O O O O O O O O O c O E!& x I I Q“ METHODS O O O O I I O O O O O 1- BZIBA£1IQ!IAE2_QLBAE!2_QZ_§QIL_§AH2L£§ Eco O O O O C O O C O C O C I O O QQNEIBEAIIOE OF THE PESTICIDES . . . . QALQELAIIQE_QZ_EEEIIQID£§_£QNQE§IEAIIQH RESULTS AND DISCUSSION . . . . . . . . . . . a. A BE 0 EA ENT BT vi Page 20 21 23 25 25 27 27 27 28 28 28 29 29 3O 31 32 32 33 33 33 34 35 36 37 Chapter V. CONCLUSION AND FUTURE RESEARCH . . APPENDIX A--RESULTS OP TEE CNNONATOGEAPNIC ANAL!SESOPSOILSANPLES......... APPENDIX B--CALCULATED NEAN AND STANDARD DEVIATION IRON CNRONATOGRAPNIC DATA . . . . APPENDIX C--PLOTS 01' THE RESULTS . . . . . ”v-1: D--CNRONATOGRANS 01' THE ANALYSES. . LITERATURNCITED............. vii 38 40 Table So LIST OF TABLES Page Name, chemical, and biological properties of metolachlor (adapted from Lebaron et aI., 19833Pesticide Manual, 1983) ............. 17 Name, physical, and biological properties of metribuzin (adapted from Williams, W.M. et al., 1988; Hatzios, K.K., Penner D., 1988; The pesticide Manual, 1983).. . . . . . . .............. 18 Name, physical, and biological properties of phosmet (adapted from The pesticide Manual, 1983) ....................... 19 Initial soil test data ....................................... 25 Average monthly precipitation, irrigation, air temperature, and radiation data for the experiment site ......... . ............ . 26 1989 study management and sampling schedule. Michigan State University Montcalm Experimental Station. ........ . . . . 27 Percent recovery and standard deviation (Std.dev.) of the pesticides ....... 30 Chromatographic conditions for the detection . of the pesticides in soil samples. . ........................ . . . . 31 Al. Concentration of the three pesticides found in soil samples 24 days before treatment (24 DBT). . . ........ . ................ 40 viii Table Page A2. Concentration of the three pesticide found in soil samples 25daysaftertreatment(25DAT) ..... ................ 42 A3. Concentration of the three pesticides found in soil samples 87daysafte'treatment(87DA'I')............... ............. 43 A4. Concentration of the three pesticides found in soil samples 157daysaftertreatment(157DAT).............. ............. 46 B1. Mean concentration of metribuzin measured at different depths in soil sampled before treatment. . . . . . . . . ................. 48 B2. Mean concentration of metolachlor measured at different depths in soil sampled before treatment. . . ....................... 48 B3. Mean concentration of metribuzin measured at different depths in soil sampled 25 days after treatment. . . . . . .............. 49 B4. Mean conwntration of metolachlor measured at different depths in soil sampled 25 days afte- treatment (series 892) ............. 49 B5. Mean concentration of metribuzin measured at different depths in soil sampled 86 days after treatment (series 893) ............. 50 B6. Mean concentration of metolachlor measured at different depths in soil sampled 86 days afte' treatment (series 893). ........... 50 B7. Mean conwntration of metribuzin measured at different depths in soil sampled 153 days after treatment (se'ies 89F) ................ 51 Table Page B8. Mean concentration of metolachlor measured at different depths insoilsampled 153daysafter treatment (series 89F). . . . . . . . . . 51 B9. Metribuzin concentration in soil at diffe'ent sampling period at four soil depths. .................. 52 B10. Metolachlor concentration in soil at diffe'ent sampling pe'iod at four soil deptlns ................... 52 CHAPTER I BACKGROUND OBJECTIVE THE R N F ID The benefits of peticide to mankind have been the control of insects, vectors of disease and to increase the yield of many crops. Thus the use of synthetic organic chenical created great expectation; satisfactory control of pets seened possible. The total pounds of pesticide active ingredients applied on farm increase 170 % between 1964 and 1987, while total acres under cultivation remained relatively constant (US Department of Agriculture, 1984). Herbicide use continue to increase, but insecticide use has stabilized and use patterns have shift away from organochlorine toward organophosphate and carbamate compounds. The total dollar value of the domestic agricultural peticide market is about $4.0 billion (Association, 1987). Cropland treated with peticide was reentiy etimated to be 249 millions acres in the USA and the total amount of peticides applied was 743 millions lb (Pimentel and Levitan, 1986). Some of the cropped soil receive a pre- eme'gence herbicide, fungicide, nematicide, systenic insecticide, post emergence herbicide, one or more post-emergence insecticide or fungicide, and defoliant, all in a single season (Nash, 1967). Annual application rate range from several ounce to several pounds per acre, depending upon the crop and the pest problems in a spedfic fields ('I‘.B. Moorman, 1989). Peticide have been used and are still used against insects that are vectors of the most debilliting diseases which affect mankind such as nnalaria, filariasis , and typhus or against termite that detroy house. Ih‘om the economic standpoint as well as health, pesticide will continue to be vital in the production of food and for the protection of man and animal. Chenieals often 2 do not reach the pest population; 0.1 % of the peticide applied to crops reache the target pets (Pimentel and Levitan, 198$. The leftove' may move through the environment affecting non target organisms in and into the soil, surface water, and air. Thee chenicals create a great concern among general public. Nearly half of farmers in a 1989 nationwide survey by Jeffe-son Davis Associate in Iowa we'e worried that their use of chenicals pose a We to thenselve and to the environment (Michigan Department of Agriculture, 1990). The cost of agricultural products to the consumer could double or triple if peticide use were suddenly te'minated (Caro, J.H., 1976). A complete cessation of peticide use is unlikely, but because of increased chemical costs, a bette understanding of economic thresholds for peticide use and increase awareness about environment contamination, many agriculturalist are becoming more prudent about peticide use. Assesing all these problems is not easy; a benefitlcost analysis have often been used but quantities involved are not easily quantified. With these consideration in mind, diffe'ent management strategle (altenative farming systems) have been proposed. Their managenent strategie seek to enhance and to use biological inteactions rathe' than reduce and suppres then and to exercise prudence use of external inputs. Integrated Pest Managenent (1PM), the most prevalent of thee practice was defined by Jimmy Carte- in its preidential mesage to the congres as "a system approach to reduce pest damage to tolerable levels through a variety of technique, including predators and parasite, genetically reistant hosts, natural environment modifications, and when appropriate, chenical peticide". In other words it is a deign that conducts continued evaluation of pet control procedure that result in a favorable socio-economic environment (George, W. Bird, 1989). Detemining the economic threshold is the difficulty in IPM, because it is not constant. It doen’t always decrease peticide use, rathe' it give more knowledge about pet 3 population and often increase the number of peticide applications because of better knowledge of pet population. (Allen et al., 1987). i The reponsible use of peticide require knowledge of how they are transported, partitioned, detoxified or accumulated in the environment. The unde-standing of thee mechanisne as well as the development of technique such as analytical technique and simulation model will prevent the imposition of regulations that unnecessarily retrict the use of wish peticide. W The first objective of this study was to develop analytical technique (extraction, purification, and chromatography) to dete'mine the reidue of three peticide commonly used in potato production: metolaclnlor (Dual), metribuzin (Sencor), and phosmet (Imidan). The second objective was to study the pe'sistence of thee chenicals unde field conditions. The final objective was to compare the movenent of thee chemicals in soil with regard to soil propertie, to weather, and to their characteristics physical and chenical characteristics. CHAPTER II REVIEW OF H'I'ERA'IURE W Upon the‘r introduction into the environment, peticide are subject to degradation and transfe procese that detemine not only their persistence and fate, but their availability for bioactivity. Figure l. Procese influencing the behavior and fate of herbicides in the environment (Sawhney, B.L. and Brown, K.W., SSSA Special Publication N' 22, 1989) :- S . A. 0“!» c slfi. 5‘ fa Photo- 51'. decomposition . . __ 1 fl .T'lfi—{J “12:; _,... ,.., _. . .. -- 4+ _ ; ; ;., _;.. J. m m ‘ ‘ e um! 11’, “e“ "KIT-KrXT‘ ”M" air. £1. 435.906.) 3' \ ‘ . u ”. 5.6};7) i 4} at? ‘r ' Ion II//// I. / .2 - O O cocoa H OOHQO. 5 Three specific degradation procese serve to break down the peticide and clnange their chenical composition: (1) biological decomposition, (2) chenical decomposition, and (3) photodegradation (Fig 1). Thee procese are due to the action of divese type of organisms living in the soil as well as by the physico-chemical interactions between peticide and the environment. Organic chenicals are transported by five common transport procese that operate at the subsurface environment (Fig 1). Thee procese include the following: 1. Absorption, exudation, and retention by crops and crops reidue; 2. Run off movenent in eithe the dissolve or sorbed state; 3. Sorption and deorption to organic matter, clays and mine-a1 surface; 4. Vapor phase diffusion; and 5. Hydrodynamic transport and dispe-sion as soluble constituents of the aqueous phase. W Sorption proces include absorption, adsorption and partition. It is an important interphase mass- transfer proces that detemine the relative fraction of the organic clnenieal reident in each phase (solid, aqueous, and vapor). The portion ofa compound that is sorbed is thought not to be available for biodegradation, and chenical transformation proceeds at diffeent rate depending on which phase the solute occupy (W she and Mille', 1989). Absorption is the proces by which peticide penetrate through tissue into an organism or into environment mate'ials. Adsorption refe-s to the condensation of vapors or solute on surface or inte-ior pore of solids by physical or chenical bonding. In contrast during partition the organic chennical penetrate into the network of an organic medium by force common to solution clnenodynamie (Boyd, 8., 1991). 6 Adsorption and partition are the procese that govern most the mobility and availability of peticide in soil. In fact, soil is postulated to belnave as a dual sorbent in which the mineral matter functions as a conventional sorbent and the organic matte as a partition medium (Chiou et al., 1985). PARTITION Thepartition uptakeisanalogoustotheettractionofanorganiecompound from water into an organic phase (Chiou, C.T., 1989). It is has been shown to control the uptake of non ionic organic compounds (NOCs) in soil and wate' systen (Chiou et al, 1983). According to this mechanism soil organic matter act as a solubilizing medium for NOCs and is functionally and conceptually like bulk-phase solvent (e.g octanol) in its uptake of NOCs from wate. In soil wate- systens, the nnineral ted as sorbent for NOCs due to strong dipole inte-actions between wate- and mineal surface (Chiou et al., 1985). W 0f the procese influencing the fate and behavior of peticide in soil, adsorption is the most influential and depends on both soil and peticide propertie. The adsorption/deorption proces is an equilibrium proces and controls the concentration in soil solution and thus renove part of the peticide from the field of potential action reulting in reduced bioactivity, in reduced clnenieal degradation, or simply in retarded movenent in and through the soil. Thee are three major type of adsorption: 1) chenical adsorption- due to coulombic force which involve the sharing of electrons between the chenical and the adsorptive surface and is characte'ized by high heats of adsorption; 2) physical adsorption, 7 due to Van de' Waals force which are attractive force between dipole and have low heats of adsorption; and 3) hydrogen bonding, due to bonds between two highly electronegative atoms through the medium of a hydrogen atom (Zahik, 1983). Adsorption depends on both the soil and the peticide propetie. It is usually greatest in the order organic matter > high clnarge clays > low charge clays. Bailey and White (1970) have suggeted that the nature of the functional groups (OH, C0, COOH, and NH), the nature of substituting groups, the steeo position of groups with repect to other functional groups which may enhance or hinde intramolecular bonding, and the preence and magnitude of insaturation in the molecule play an important role on the adsorption and belnavior of peticide chenicals. The frenmdlich equation is the simplet equation that describe adsorption: X = Weight of chenical m = weight of soil C = Concentration of solution at equilibrium n = constant = 1 at normal solutions , k = constant that give the extend of binding. For practical purpose, only the distribution coefficient (Kd) is used to compare adsorption among systens chemical adsorbed( M) Kd= Kg chemical 6 solution ( £119!) we Runoff Iosse are of greater conce'n because of the direct input to wate° bodie 8 and because of the possibilitie of fish killed and the contamination of Mine aquatic specie. Peticide may be transported in runoff from land to aquatic habitats in true solution, as small undissolved particle, bound to eroded soil particle and plant debris or dissolved in hunnic material (Willis, C.H. and Mcdowell, L.L., 1982). Peticide propetie as well as rainfall characteistie, rate and mode of peticide application, soil texture and topography affect the concentration of peticide in runoff. Weber and al. (1980) classified peticide according to their dnennical propertie. The basic peticide are immobile at low Ph and, but can be mobile at high Ph depending on water solubility and structure. acidic peticide are mobile at normal Ph, but the arsenate and phosphate peticide, because of their propensity for soil sorption, are usually immobile. 'Ihe nonionic peticide are usually sorbed to some extent in the soil, but the degree of sorption depends on water solubility, vapor presure and chenical structure. Wauchope (1978) conclude in a long-tem study that (a) wettable powde's produce the highest loose (up to 5% of the amount applied, depending on the slope), (b) water insoluble peticide (usually applied as enulsion) show lease of 15% or less, and (c) wate‘ soluble peticide (usually applied as aqueous solutions) and soil incorporated peticide show losses of 0.5% oriess.'flne ovealllossofpeticide foralldnmicalclasserangedfromOtolSfiofthat applied. W Volatilization is the loss of chenicals from surface in vapor phase. The poteitial for volatilization of a clnennical is related to its inherent vapor presure and wate solubility, but actually the rate will depend more on environmental conditions and all factors that control behavior of the clnenieal at the solid-air interface. 9 Volatilization from soil is difficult to predict because of the many parameters affecting their adsorption, movenent and pe'sistence. It involve deorption of the clnenical from the soil, movenent to the soil surface, and vaporization into the atmosphere (Spence et al., 1973). The potential for loss through volatilization can be etinnated from the physical propetie of the pesticide molecule. Knowledge of vapor pressure and water solubility pernnits calculation of the air/water partition coefficient, and knowledge of the approximate strength of adsorption by soil (Hartley and Graham-Bryce, 1980). In the study of the factors that could affect volatilization of insecticides from soil, Harris and Lichtenstein (1961) found that volatilization increased with increasing soil moisture. They explained this by the fact that insecticide molecule wee displaced from the soil particle by wate- molecule in the air. The found also that rate of volatilization was function of rate of air movenent. Comequently, under field conditions the rate of volatilization of insecticide reidue from the soil may be retarded in areas of dense vegetation cover. W Soil provide an ideal environment for many type of degradative procese. Thesereactionsaffectthefateandbehaviorofpesticide chemicalsintheenvironment. The rate at which a peticide degrade is in part function of its molecular structure. It is influenced by several soil and weathe factors whicln may vary from site to site and from year to year. W Non-biological degradation, is by definition, any decomposition of peticide that 10 doe not involve microbial procese. It involve reactions such as reduction, oxidation, elinnination, substitution, isome'ization, and hydrolysis (Lichtenstein, 1977). For the peticide in the atrnosphee, on foliage or on the soil surface; photodegradation can occur. Photochenical transformation of peticide are chenical procese that occur when enegy in the form of light (usually ultraviolet light) inte‘acts with the peticide molecule. This reaction involve two opeations (Zahik, 1983): 1. absorption of enegy leading to excited state, and 2. transformation of the various electronically excited state to chenical products. The reaction is sometime affected by photosensitizers. Thee sensitize-s can cause increased sensitivity to light by transferring the enegy of light into the receptor clnemicals (Matsumura, 1973). The study of photodegradation of every peticide under actual conditions is not practical, and often impossible, thus two diffeent approache have been used to predict the photoclnenical behavior of such compounds (Zahik, 1985). The first model is a model ecosysteninwhiclnanattenptismadetoincludethevariablelikelytoexistinthe environment under consideration. The second approach is a mathenatical treatment of available data through computer simulation programs. The reults are then compared to actual field conditions. An adequate repreentation of field situation will be to combine both approache. Example of photolysis are those of 4-amino 6-R-3 methyltlnio s- triazin- 5(4H)- one R = phenyl, cyclo, hexyl, te‘t-butyl, isopropyl) in CCL, benzene, metinanol, water or in crystalline state. Thee reactions yield the repective 5-hydroxy-6-R-3- (methyltlnio)-l-2-4- triazin as the major product. The proposed mechanism involve an intramolecular hydrogen abstraction. Minor reactions proceed by route which include deulfuration, and oxidation 11 (Pape and Zahik, 1972b). In the case of organophosphate peticide, Two majors type of photoproducts have been reported: the oxygen analogs where the structural change is the replacenent of a sulfur by oxygen, and products reulting from the cleavage of the PS, P-O, or C-8, C-0 bonds. (Zahik, 1985). The photolysis of phosmet in diethyl ethe- produce only two major insoluble products in low yield when irradiated at >286 nm. The products, N- methylphthalmide and N-methoxymethylphtlnalmide, m the same whethe' the reaction was run in air or under nitrogen. Many minor products we'e obseved but} not identified (Tanabe et al., 1974). Reactions that are involved in the clnennical degradation of peticide are predonninantly oxidation along with hydrolysis and isome'ization. 'Iinee reactions detroy the chenicals and thus progresively and permanently decrease their biological effectivenes. The rate of chenical reactions depend greatly on conditions sucln as tenperature, Ph, and the composition of the medium in which the reactions take place. Example of clnenical degradationns are alkaline hydrolysis of organophosphorus compounds such as malatlnion or adsorption catalyzed of chlorotriazine (Hartley and Graham-Bryce, 1980). For peticide not affected by surface catalysis, degradation nnight be expected to occur predominantly in solution (Hartley and Graham-Bryce). In this case adsorption would retard degradation by renoving the chenical from solution I E TI Firehse and Anderson (1982) have suggeted that tlnree main variable, apart from concentration, contribute to the rate of biodegradation of peticide. 1. The quantity of microorganisms or enzyme systens which have the capacity to degrade 12 the clnenical. 2. The availability of the clnenical to the organisms or enzyme systen reponsible for degradation. 3. The activity level or physiological state of the organisms. The structure of the peticide involved is very important in its attack by soil microorganisms. Introduction of polar groups such as 0H, N11,, NCO, C00,NO, often afford microbial systens a site of attack. The rate of degradation reaction is furthe' modified by ste'ic and electronic factors on neighboring atoms (Helling et al., 1971). Environment conditions and soil factors have great impact on microbial degradation. Warm soil tenpeature, adequate moisture and the preence of organic matter geneally promote microbial activity by providing a suitable environment for microorganisms. For example, the higher the soil tenperature, and soil moisture level accelerated decomposition of the insecticide diazinon and tlnionazin (Getdn, 1968). The same author showed that an increase of soil Ph of 4.3 to 8.1 enhanced the biological breakdown of thiazinon. Soil microorganisms are important in catalyzing many procese sucln as cycling nutrients from soil and fertilize or transfer nutrients directly to crops. 'Ihey nnineralize, oxidize, reduce and immobilize elenents in soil, and influence their solubilitie (Alexander, 1969). 'lhee procese can be influenced by peticide that reacln the soil after application and the reponse of microorganisms depends on tlne rate and method of application, the toxicity and spectrum of activity, and the pesistence and availability of the chenical. l3 Domscln et al. (1983) have shown that peticide affect microorganism population, increase ammonium production and depres nitrification but most of the studie concerning peticide-soil interactions involve pretreated soil that tends to exaggeate the effects of peticide. Depite this fact, long-tem field expeiments have indicated that peticide do not cause critical decline in microbial populations or the procese contributing to soil fe'tility (Cole, M.A., 1976). Metolachlor is an herbicide that provide excellent control of most annual grasse and many broadleaf weeds. The molecular formula of metolachlor, a chloroacetannide hebicide, is C. H. Cl N 0, and appears structurally as shown in Figure 2 (Peticide Manual, 1983). CH3 'fHa /CHCH‘.,_OCH3 O N \COCH2 Cl cnzcn3 Figure 2. Structure of Metoladnlor 14 Its high level of biological activity and deirable clnenical and soil stability (Weber et al., 1981), provide good control of late ge'minating grasse, epecially under conse'vation tillage systen (Lebaron et al., 1983). It is an effective hebicide for control of yellow nutsedge (Cypenrs eculentus L.). Metolaclnlor is used selectively in cotton (Gossypiran Miriam L.), peanuts (Amehn‘s hypogaea L.), corn (Zea mays L. Moencln), potatoe (Solarium tubemsran L.), soybeam (Glycine max L.), and othe- broad-leave crops. (Peticide Manual, 1983). Chloroacetannide are preumed to inhibit plant growth (Ashton and Crafts, 1981), their primary hioclnenlcal mechanism of action is unknown. Metolachlor inhibits the early development of susceptible weed specie (Penner and Hatzios, 1988). The treated seeds of susceptible specie usually ge-minate, but the seedlings eithe do not enege from the soil or energe and exhibit stunted or abnormal growth (Penner and Hatzios, 1988). The basis of selectivity of the chloroacetamide herbicide could be attributed to the ability of reistant plants to metabolize then at a rate sufficient to keep cellular levels of the hebicide bellow that required for growth inhibition (Leharon et al., 1983). Metolaclnlor appears to be most efficiently taken up by roots or cotyledons of grasse, while root absorption is vey important for uptake by many cotyledoneous plants. Translocation of both hebicide in plants is acropetal (Leharon et al., 1983). Metolachlor’s technical information is summarized in Table 1. W Metrihuzin is a heteocyclic basic organic molecule applied as pre-ene-gence or early post energence to control annual grasse and numerous broadleaf weeds, including some hard to control weeds, such as cocklehur, velvetleaf, jimsonweed, sicklepod etc (Peticide 15 Manual, 1983). Metolachlor which molecular structure is C. H,. N. O 8 presents the structure as depicted in Figure 3 (Peticide Manual, 1983). o CH3)3C II \"/\/T\/ 2 N\/ N SCH3 Figure3.Structnn'eofMetribun'n. Metrihuzin is readily taken up by roots and translocated to the shoots and leave of treated plants in the apoplast (Sclnumaclner et al.,l974; Falh and Smith, 1984; Fortino and Splittstoese', 1974). Factors affecting the rate of transpiration, such astenpe-ature, humidity, light intensity, and stomatal ape'ture would also affect the root uptake of metribuzin (Penne- and Hatzios, 1988). The translocation of metribuzin in the apoplast is not exclusive, it readily penetrate the symplasm of roots or leave, but because of inability to retain it for king time, metribuzin leaclned into the apoplast and carried away with the transpiration stream (Penner and Hatzios, 1988). The symptoms of metribuzin toxicity are those of photosynthetic inhibitor (Fedtke, C., 1982), but metribuzin has been reported to intefere with biochenical and physiological procese of plant metabolism, such as nitrogen metabolism an repiration. The biological and physical propertie of metribuzin are summarized by table 2. 16 mm Non systennic acaricide and insecticide used on top fruit (e.g. apple, pears, peache, apricots, and cherrie), citrus, grape, potatoe, and foretry at rate (0.5 - 1,0 kg a.i./kg) such that it is safe for range of predators of mite and theefore useful in integrated pet managenent (The peticide Manual, 1983; The Meek Index, 1983). The molecular structure of phosmet is shown In Figure 3 (The Peticide Manual, 1983). The biological and physical characteistics are summarized by table 3. s CH30\," R CH30 Figure 4. Molecular structure of Phosmet 17 Table 1. Name, chenical, and biological propertie of metolachlor (adapted from Lebaron et al., 1983; Peticide Manual, 1983) PROPERTY DATA or COMthNTS Q Chennical name 2-Chloro-6’ethyl-N-(2-methoxy-l-nnethyl-ethybacet-o- ‘ toluidide Common name Metolaclnlor ; V Trade name Dual Fornnulation DUAL, E.C.(500 or 700 g a.i.ll) i BICEP, Metolaclnlor + Atran’ne (1.5:1) i Appearance Colorles to tan Vapor presure 1.3'10‘ mm Hg at 20'C , Water solubility 530 ppm ‘ Soil photolysis Stable, but degraded about 50 degree 8 days in natural or artificial light Soil half life 7 15-50 days depending on the region Mode of action Possible germination inhibitor Volatilization Relatively non volatile 18 Table 2. Name, physical, and biological propetie of metribuzin (adapted from Williams, W.M. et al., 1988; Hatzios, K.K., Penner D., 1988; The peticide Manual, 1983) PROPERTY DATAor COMMENTS 5 i Chenical name 4-Amino-6—te‘t-butyI-3-methylthio-as-triadn-5(4H)-one J Common name Metribuzine : i TT-ade name SENCOR, SENCOREX, SENCORAL (Baye) % .5 LEXONE (Dupont) a Fornnulation W.P> (350, 500, 700 g a.i.lkg); 1 aqueous suspension(420 g/kg) i : Appearance White, Crystalline solid I I Vapor presure < 10‘mm Hg at 20'C Wate' solubility 1200 ppm at 20‘C LB. 2200 mg/Kg (rat) Soil photolysis 15-50 days depending on the region q Mode of action Photosynthetic inhibitor Volatilization slightly volatile 19 Table 3. Name, physical, and biological propetie of phosmet (adapted from The peticide Manual, 1983). ; PROPERTY DATA or COMMENTS l , Chenical name 0,0—dimethyl S-phtlnalimidomethyl phosphorodithiote " Molecular formula C,, H,, NO. PS, ‘ Phosmet ‘ Common name i Imidan Trade name Imidan W.W. (125 or 500 g a.i.lkg) ' Formulation Imidan 5 Dust (50 g a.i.lkg) Colorles crystalline solid Appearance | 0.997 mm Hg at 30’C ' Vapor presure 22 mgll at 25‘C , Wate solubility 113 mgIKg (rat) . w. Acetylcholineterase inhibitor Mode of action ! Non systenic Activity 9 ,_. 20 W Metolaclnlor is relatively non volatile (1 .2‘10‘ mm Hg), however volatility can cause a nninor loss of metolachlor when applied pre-energence to bare soil or in some conservation tillage situations. Volatilization is influenced by the type of surface to which the hebicide is applied; Parochetti (1978) obseved that while only 0.1% of metolachlor was lost from the soil surface, about 11.5 to 36.6% volatilized from the straw surface of various plant reidue. Under practical field conditions, only 0.6 to 1.4% of applied metolachlor would volatilize from the soils treated witlnin the first 24 hours (Buckhard, 1977). Metolaclnlor is not very strongly adsorbed to soil particle. Buckhard (1978) reported that the fiemdlich adsorption constant (K) for metolaclnlor ranged from 1.54 to 10.0 ug of soil. Reults of the studie of the effect of soil clnenistry on metolachlor adsorption are controvesial. Strek and Webe (1981) reported that metolaclnlor adsorption was strongly correlated with organic matte content and cation exclnange capacity, clay content had little influence. They also found that the soil organic content has little influence, but greater adsorption occurred on montmorillonite clay. Movenent of metolachlor in soil seemed to be mainly influenced by organic matte and/or, clay content. Ohrigawitch et al. (1981) reported les leaclning of metolaclnlor in a Pullman clay loam when compared to an Amarillo fine sandy loam and Patricia fine sandy loam. Although there is evidence of some chenical degradation of metolachor, most of the studie showed that unde' normal conditions of field use, metolachlor and othe' acetanilide hebicide are degraded mainly by nnicrohe. McGahen and Tiedje (1975) found that 21 metolaclnlor was degraded by the soil fungus Chaetomium globosum. Krause et al. (1985) found that an actinomycete strain isolated from soil also metabolized metolachlor. Degradation proceeded via oxidation of the chloroacetyl group. The major metabolite was the oxalic acid de'ivative [ N—( 2’- methoxy - 1 - methylethyl ) - 2 - ethyl - methyl - oxalic acid anilide ] (Guth, 1981). Chen and al. (1987) have shown that transformation included also declnlorination, delnalogenation, dealkylation, hydroxylation, and indoline ring formation. W The mobility of metribuzin in soils is inve'sely related to the soil adsorptive capacity. In geneal metribuzin is relatively mobile in sandy and mine-a1 soils but vey immobile in soils with high organic matte-s . Metribuzin leaching from the zone of soil application is dependent on the amount of rainfall or irrigation that occurs unde field conditions (Slnaron and Stephenson, 1976). It has been shown that Ph has great influence on leaclning of metribuzin (Ladlie et al., 1976). Furthemore they reported that metribuzin leaclning in soils increased with increasing soil pH. It has been shown by (Schmidt, 1973) the existence of high negative correlation of metribuzin phytotoxicity and soil organic matter. It was concluded that the herbicidal inactivation of metribuzin in soils was due to a Ph dependent adsorption of this clnennical to the soil organic matte (Schmidt, 1975). The mechanism involved in adsorption of metribuzin to soil particle is the formation of binding force between the herbicide molecule and soil particle due to electron density of annino groups at C-3 and N-4 positionns of the heterocycllc ring. Most of the studie on metribuzin phototransformation have been conducted 22 primarily under laboratory conditionns rathe' than field conditions. In this case plnotodecomposition in the environment unde practical conditionns is not well unde'stood. Pape and Zabik (1972) have shown that deamination is the major reaction involved in photodecomposition and it yields deamino-metribuzin (D-A) as major metabolic products. Although it is not always easy to distinguish between tine biological and non- biological degradation of a given herbicide in soils , early studies on the fate of metribuzin in soils enphasized the importance of the non-biological degradation of this he'bicide. Reports have shown degradation of metribuzin in soil samples awaiting reidue analysis and stored at -37 'C (40). Only non-biological activity could account for this degradation since little or no biological activity would be expected at this low tenpeature. 101 and 114 have reported a slower degradation in sample from deeper horizons rathe' than in surface soils. This shows that degradation is influenced by soil depth. Since soil components are in vast quantities compared with the hebicide, it degradation should follow a first orde- kinetics. This has been shown by (Hyzak and Zimdahl, 1974) . He showed that the rate of metribuzin and its isopropyl and cyclohexyl analogs in soils unde' field and laboratory conditions appears to be best dee-ibed by first-orde- kinetie. Common metabolite of non-biological degradation of metribuzin are deamino (DA), deketo (DK), and deannino deketo (DADK) metribuzin. A numbe' of reports have denonstrated the importance of microbial activity in the degradation of metribuzin in soils. Ennnigation, ste‘ilization by autoclaving, irradiation by 7 rays, and treatment with microbial inhibitors (Sharon and Stephenson, 1976; Ladlie et al., 1976) have produced marked reductions in the capacity of selected soils to degrade metribuzin. A number of soil bacte'ia, including Auhrobacter and Pseudomnas species as well as soil fungi, sucln as Rhizopusjaponicus and Cunninghamella echiuulata Thaxte- have 23 been reported to rapidly deanninated metamitron, a triazine hebicide with relative structure as metribuzin (Engelhardt and Wallnofe', 1978 ). Metribuzin metabolite that have been detected in soils and are believed to result from microbial degradation include DA, DK, DAAK ( Sharon and Stephenson, 1976 ). Contrary to s-triazine herbicide, the ring of metribuzin or othe' triazinone could be cleaved by soil nnicrobes. Fangelhardt et al. ( 1982 ) has reported the formation of benzoyl formic acid, acetylhydrazone and benzoyl fornnic acid as the result of ring cleavage. Deearboxylation and oxidation can be involved in this degradation and yielded 3-methyl-6-phenyl-l,2,4,5-tetrazine. EHQSMEE Although Phosmet is not intended for use as soil insecticide, some reidue could reacln the soil tlnrough its use on various crops. But as with most organophosphate insecticides, it degraded fairly rapidly in soils. soil Pin and tenth as well as moisture (content seemed to greatly influence the rate of degradation (Menn et al., 1965). Several nnlcroorganisnns have been implicated in the degradation of several organophosphate insecticide. Ahmed and Casida (1958) have shown that the yeast Tandopsis milk, the algae Clnlorclla pynenoidosa, and the bacte'ia Pseudomomfluomcenccs and Mbacillus thiooxidaus metabolized seve‘al dialkyl phenylplnosplnates and phosphorotlnioate. Menn et al. (1965) have shown that Phosmet was more stable in autoclaved soil and tlnat partial detruction of soil microorganisms increased the pe'sistence of phosmet. That could only be explained by microbial activity. Two majors products have been reported in the photolysis of organophosphate: (l). the oxygen analogs whe'e the only structural change is the replacenent of sulfur by oxygen, and (2). products reulting from the cleavage of the P—S, P-O,, or C-0, C-8 bonds 24 (Zabik, 1985). When Phosmet is irradiated at > 286 nm in diethyl ether solution, it produced two majors isolable products: N-methylphthalinnide and N—methoxymethyl phtlnalinnide (Tanabe et all., 1974). CHAPTERIII MATERIALS ANDMETHODS LE L The soil sample analyzed in this study we'e obtained from an ape-iment designed for the study of the leaclning potential of nitrogen fetilize- under a potato field (Joern, 1991). The expe'iment was located at the Michigan State University Montcalm Research Farm. The soil at this area was mapped as a Montcalm-McBride sandy loam complex. Soil characte-istie, and weather as well as irrigation records are shown respectively in Table 4 and 5. The expe'imental deignn selected for this invetigation was a randomized complete block with four replications. Each replication consisted of 0.86 m wide x 15 m long plot. The distance between rows was 0.56 m with approximately 25.4 cm planting distance between seed tube-s. Table 4. Initial soil test data. Bray-1 ---Exchangeab1e--- Organic Year Ph 9 K Ca Mg Matter csc ---------- Kg/ha---------- % 1988 5.6 672 332 806 120 1.9 6 1989 6.2 597 305 853 151 1.7 5 26 The two hebicide, metribuzin (Lexone 75%) and metolaclnlor (Dual 86.4%) were incorporated into the soil at the rate of 0.65 kg/ha and 2.24 kglha respectively. Phosmet (Innidan 50 WP) was applied three time during the year after planting but after energence at the rate of 1.12 kg/ha eacln time. Each sampling consisted of two soil sample (3-5 core 5 en in diamete) taken across the hillofthetwocente' rows ofeacln plotstoadeptlnofl20cm. Eaclncorewasdivided according to the depth. For this study, only depths I (0-15 cm), II (15-30 en), III (30-45 cm), and IV (45-60 cm) were analyzed. Evey Soil sample was nnixed thoroughly and air dried, ground, sieved, and fist stored in cardboard boxe. The soil sample we later transferred into glass bottles and stored at -20 ‘C until laboratory analyse we'e performed. Table 6 summarized the spraying record as well as the soil sampling pe'iods. Table 5. Ave'age monthly precipitation, irrigation, air tenperature, and radiation data for the expe-iment site. Rainfall Irrigation Temperature Month (mm) (mm) (0C) 1989 Mean* 1989 mean* 62 68 -- 7 7 68 66 -- 12 13 June 123 79 -- 19 18 t 59 112 22 21 36 19 19 -- 14 15 * Long-term mean 27 Table 6. 1989 study management and sampling schedule. Hichigan State University Montcalm Experimental Station. Event Pesticides Katribuzin Hetolachlor Imidan Background sample 5/2 5/2 5/2 Treatment 5/26 5/26 6/28-7/6 7/13-8/3 Planting date 5/4 5/4 5/4 Hilling 5/30 1st sample 6/21 6/21 6/21 2nd sample 8/22 8/22 8/22 Harvest 9/21 9/21 9/21 3rd sample 10/29 10/29 10/29 RIAJWHRLKLS QLfiSflARE EgEIflMTIQN All glassware (round and flat-bottomed flasks, separatory funnels, funnels, and chromatographic columns) were washed in soaped hot wate, rinsed with distillate water followed by acetone. The glassware was further placed in a furnace for drying. W Solvents: acetone, acetonitrile, dichloromethane, methanol and hexane wee peticide grade solvents and used as received. Chenieals: reagent grade sodium sulfate (granular, anhydrous ); Florosil-PR grade (60-90 meh) activated at 135 0c for 4 hours before use; Liquid nitrogen. Refeence chenical standards : metribuzin 99.9 %, metolachlor 98.8 %, Phosmet 98.9% were obtained from the U.S. Environment Protection Agency (EPA), Peticide and Industrial Chemicals Repository, Reearch Triangle, N.C. 28 Miscellaneous: glass wool and Whatman cellulose extraction tlnimble 25 mm x 80 mm. W Gas chromatograph Varian Aerograph se-ie 1400, Gas chromatograph Beckman GC-65, Gas clnromatograph double focussing mass spectrometer (Ge/Ms) Jeol AX505, Spectra Physic integrator SP4270, Hewlett Packard integrator 3390A, and rotary evaporator Buchler Instrnnnents, Soxhlet extractor and soxhiet heater GCA/Precision Scientific. W The extraction and liquid-liquid partition procedure wee adapted from Thorton and Stanley (1977). W Eacln soil sample was mixed to homogenized tlne entire sample. A 25 g aliquot of the mixed soil was weighted into an extraction tlnimble. 100 ml of 20 % aqueous methanol was measured into a 125 ml fut-bottomed flask and two boilizers were added. The soxhlet apparatus containing the sample was attaclned to the flask and extracted for 6 hours. The extract was evaporated with a rotary vacuum evaporator until only wate renained (10-20 ml). The wate extract was transferred into a 250 ml separatory funnel with an additional 50 ml of wate. The flask was rinsed with an additional 60 ml of dichloromethane which was added to the separatory funnel. The phase wee allowed to separate and 60 ml of dichlolromethane was added to the separatory funnel which was then shacken for three minutes. The lower phase (diclnloromethane) was drained through a funnel containing anhydrous sulfate and collected into a 300 ml round-bottomed flask. The partition was 29 repeated with two additional 60 ml portions of dichloromethane. Three drops of decyl alcohol was added to the flask and the combined diclnloromethane extracts wee evaporated to nearly drynes on a rotary vacuum evaporator at 35'C. The renaining solvent was renoved with liquid nitrogen. The reidue was dissolved in 3 ml hexane and analyzed by gas chromatography. EEQQYEEX The recovey study was carried out by spiking three portions of 25 g of soil with 2 ml of a mixture containing 2.10 ppm, 2.25 ppm an 2.0 ppm of metribudn, metolachlor, and innidan repectively. The soils wee left 24 hours to allow binding of peticide molecule to the soil particle. Then the above procedure for extraction and partition wee used . The recove'ie wee 86%, 90.33% and 84.33% for metribuzin, metolachlor, and imidan as shown by the tble 8. W The detection of the two hebicide metolaclnlor and metribudn in soil sample was peformed by using a gas clnromatograph equipped with 'H foil electron-capture detector. The following conditions summarized by table 8 wee used for the analyse. Column : DB-S fused silica capillary column (30 m x 0.5 mm i.d.) with 0.5 pm phase tlnicknes. Oven : isothemal tenpeature 150 'C. Injector : tenpeature 190 ‘C. Detector : tenpeature 210 'C. Carrie gas : helium at the presure of 140 Kpa. 30 Integrator : 3390A Hewlett Packard The insecticide Imidan conwntration was quantified with a flame photometric detector (FPD) at the phosphorus mode. The following chromatographic conditions summarized by table 8 wee enployed. Column : DB-1301 megabore capillary column (30 m x 0.53 mm i.d.), film tlnickness 1.0 pm. Oven : tenpeature 170 ‘C. Injector : tenpeature 190 'C. Detector : tenpeature 210 ‘C. Carrie gas : Helium at a flow rate of 20 cc/min. Gas flow : Air at 120 cclmin and hydrogen at 150 cclmin. Integrator : Spectra Physie SP4270. W Gas Chromatography-Mass Spectrometry (GC/MS) Jeol AX505 was used for confirmation of peticide identification. Capillary column DB-l 30 m x 0.25 mm LB. with 0.25 am phase tlnickness was used. The detection was made by using Electron Capture/Negative Chenieal Ionization (ECNCI). Table 8. Percent recovery and standard deviation (Std.dev.) of the pesticides. % RECOVERY enema B§____LPLICAT 0N LEAN M l 2 3 Metribuzin 87 86 85 86.00 1.53 Metolachlor 9O 89 92 90.33 1.53 Imidan 86 84 83 84.33 1.53 31 Table 9. Chromatographic conditions for the detection of the pesticides in soil samples. CEROH.TYPE DETECTOR COLUMN TYPE TEMPERATURE ('C) Oven Inj. Det. Varian aerograph 'H DB-S fused capillary 150 190 210 Series 1400 30 m x 0.25 mm i.d. 0.25p phase thickness J&W Scientific Beckman GC-65 FPD DB-1301 wide bore 170 190 210 30 m x 0.53 mm i.d. 1.0 phase thickness J&W Scientific Jeol AXSOS ECNI DB-1 capillary 180 30 m x 0.25 mm i.d. . 0.25um phase thickness TT ‘F N E N Quantification of peticide wee based on peak heights. Diffeent concentrations of standard solutions wee innjected and calculation of the peticide in a sample was accomplished by use of the following equation whee reponse for unknown is compared to the reponse for a known quantity in a standard solution: sanple areax std..inj. (ng) x final vol (1271) std area xwt of sample(g) sample inj(p.1) FEWT: CHAPTERIV REUL'IS AND DISCUSSION The concentration of the three peticide was monitored by analydng soil sample using gas clnromatography (GC). An Electron capture detector (ECD) was used to detect metribufin and metolaclnlor. The limit of detection for both compounds was 0.01 ppm. The soil sample had been concentrated from 25 g to 3 ml, theefore the real minimum detectable quantity in the soil should be 0.0012 ppm. The retention time wee 5.64 min for metribuzin and 8.89 min for metolachlor as shown by the clnromatogranns in Figure D3. A Flame photometric detector (FPD) was used for the identification of phosmet. The minimum detectable limit was 0.4 ppm. The detectable linnit was theefore 0.048 ppm and the retention time was 6.62 min (fig D1). The reults of the analyse are reported in appendice A and B and plotted in appendix C. was The expeiment was etabiished as a randomized block deign with 4 replications. Treatment was repreented by the depth. Each replication was sampled 5 time simultaneously. Heteogeneous variance within samming date witlnin subsample for eacln replication wee found using Bartlett’s tet. This can be explained by heteogeneity in the peticide applications. Duncan’s multiple range tet was enployed to detemine the significance of reidue level diffeence between depths and between peiod of sampling at 32 33 the significance level of 0.05. The reults are shown on the graphics (Appendix C). IMIDM! This chenical was not detected in any of the soil sample. Its concentration in tine soil is cetainly below the detection limit of the chromatographic systen. Most of the .chromatograms as illustrated in Figure D1 and D2 showed a peak at 5.64 nnin which is diffeent from the retention time for Innidan. This peak can be seen in the standard solutionns many days afte their preparation. This peak could repreent hydrolysis product of innidan or may be innidoxon, a metabolite of imidan as suggeted by Bowman (1991) . The dissipation of imidan may be explained by diffeent procese. Volatilization and plnotodegradation are two ways by which innidan could be lost in the environment. This could be important since this chenical was applied at tine surface of the leaf to control aphids. Chenical decomposition could also account for the disappearance of this peticide. Mean et al. (1965) have shown that spontaneous hydrolysis was the major factor associated with degradation of imidan. Nearly 50% degradation was obseved afte 3-19 days. This same study suggeted that microbial degradation could account for the degradation. Partialdemneionofsoilmieoorganismsineeasedthepesistencebyfl%. This rapid rate of degradation may explain the non-detection of imidan in soil sample. Finally, imidan washed from plant leave may not reacln the soil direer but may be subject to soil eosion or runoff. W For any sample, the concentration of metolachlor in soil was highe tlnan the 34 concentration of metribuzin as shown in Figure C1 to C4. One explanation for this is the diffeence between the rate of application of tlnee hebicide. The amount of metolachlor applied (2.24 kg/ha) is four time the amount of metribuzin (0.56 kg/ha). The high wate solubility of metribuzin (1200 ppm) in conjunction with the the high soil pH may have increased its hydrolysis and microbial attack as suggeted by Ladlie et al. (1976); leading to adeeeaseoftheamount found. Onthecontrary, metolaclnlorhasaveylowwater solubility and its distribution coefficient (Kd = 1.60) is highe than the distribution coefficient of metribuzin (Kd = 1.32); theefore it will remain bound to soil particle leading to les degradation. MW Thee is an appreciable amount of both hebicide found in the soil sample as shown by Figure C. This reidue is the expresion of the pesistence of thee dnemicals from previous applications. More hebicide wee found in the lower layes than the uppe laye-s, with more metolachlor in tine tlnird laye and more metribuzin in the fourth (Fig C7). The high wate solubility of metribuzin compared to metolaclnlor may explain its movenent andconcentration inthefourth laye. Thehighconcentrationoftheechemicalshnthe lowelayescanbeexplained bytheirdisplacement fromtheuppe layetothelowerlayes with wate movenent leading to their accumulation ove long peiod of time. Since microbial activity is highe in the uppe soil layes, increased degradation of thee clnenicals in thee layes may also help explain the obseved reults. Lock and Sydney (1991) attributed the phenomenon to the reduction of microbial activity with increasing soil depth. 35 D EA Afte the treatment thee is an increase of the concentration of botln chenical in almost all the soil profile except a decrease of metribuzin in the fourth laye (Fig C7). The concentration found in the sample is still low. The highet concentration found was 0.05 ppm (third laye) whicln was ve'y low compared to the 0.56 ppm added to the top 6" (0.56 ppm) during the treatment. The hebicide wee surface applied, and their pesistence may have been reduced by volatility and photodecomposition as observed by Bowman (1991) in the study of the mobility and dissipation of metribuzin and atrazine and their metabolite in plainfield using lysimetes. Chennical and mieobial degradation as well as plant uptake may also have contributed to the dissipation of the chenicals. Poor sampling and loss of recovey could also explain this obsevation. The recovey study was done with spiked soil and extracted the same day, thus the reults may have oveetimated tlne extraction efficiency because of reidue binding. Degradation during storage may also account for the decrease in the amount fotmd in the sample. Webste and Reime (1976) have previously obseved the loss of metribuzin during cold storage of sample awaiting extraction. Afte- the input from the treatment thee was an increase of metolaclnlor in the first, second, and fourth layes and a deeease in the third laye. The concentration of metribuzin incensed in the first tlnree layes and deeeased slightly in tlne fourth laye. Twenty flve days afte tine treatment, potato plants wee not well developed, their evapotranspiration and the leaf area index wee low. The-efore the available wate could move down through the soil profile with the hebicide as proposed by Green and Khan (1987) in a review of the movenent of peticide in the soil. The slight decrease in the concentration of metolachlor in the third laye correponded to the movenent of this clnenieal downward leading to the slight increase obseved in the fourth laye. This can be explained by the preence of high 36 absorptive site or les porosity preventing the herbicide from moving with wate. This accumulation in cetain zone of the soil was also obseved by Allan Waite (1973) and he explained it by soil structure. The concentration of metribuzin is highe in the second and third layes compared to the first laye. Because of its mobility metribuzin will move readily with wate as obseved bee. The large decrease in the concentration of metribuzin in the fourth laye may be the reult of the downward movement of this chenical and may aho have contributed to tlne increase of the concentration in the third laye due to upward movenent. W Thee was a large increase in the concentration of metolachlor in all the soil layes. Metribuzin slightly increased in the first and fourth laye and slightly deeeased in othes. This increase in the concentration of metolaclnlor 87 days afte the treatment was not easy to intepret. This high concentration found was probably due to inheent soil clnaracteristie and spatial variability, and has been seen in otlne studie (Carsel et al, 1988; Rutln and Penne, 1991). This increase in the concentration may also be due to upward movenent of the hebicide reulting from the drought situation. Even though thee was rainfall and irrigation was done during this peiod, the soil was dry because of the high uptake of wate by potato plants. The plants wee at the stage of tube production, consequently their metabolism and evaporation rate wee high theefore thee was increase of their evapotranspiration. The chenicals in soil will move upward with wate. Metribuzin is a weak acid and may have been subjected to binding to soil particle. This binding could have reduce the movenent of metribuzin in the soil as shown by the reults. The slight increase of the concentration in the fourth and first layes may have reulted 37 from some movenent of metribuzin from the second and tlnird laye. 151W Metribuzin conwntration increased in the first and third laye and decreased in the fourth laye. The concentration in the second laye renained almost constant. The concentration increase of metribuzin in the tlnird laye could have reulted from the upward movenent of this clnennical frorn the fourth laye. The tlnird laye has not been disturbed by tillage, renaining compacted. In this case the aeation is low, reducing microbial activity. Further metribuzin may have move upward to the first laye reulting in the high concentration found in the uppermost laye. Les rainfall occurred during this- peiod contributing to the drought. This would ineease upward movenent of soil wate potentially moving soluble hebicide with it. Potatoe wee harvested before this tinne peiod and the leave renaining on the ground may have been incorporated into the soil. The preence of this biomass may have increased the retention of metribuzin reulting in les degradation and les movenent. We found a large decrease of nnetolaclnlor in all layes. This large concentration decrease of metolaclnlor may be explained by metabolization. The high microbial activity in the top layes combined with hydrolysis may have increased the dissipation of this chenical. The concentration of metolaclnlor in the tlnird laye decreased less. This reult was obseved with metribuzin and could be explained by the same soil compaction. The oveall patten of the curve can be explained by downward and upward movenent of the hebicide in the soil profile. This movenents have been influenced by environmental conditions (rainfall, tenpeature), plants metabolism (evapotranspiration), and by cultural practice (irrigation, billing, and harveting). CHAPTERC CONCLUSION AND FUTURE amen Complete metabolism of phosmet was obseved with the preence of one prepondeant metabolite. Even though furthe studie should look at the metabolic products, phosmet should not be a seious threat to the environment. We found the two hebicide (metolachlor and metribuzin) in the soil 157 days afte treatment. Some hebicide will renain in the soil like those found in the background sample but the amount will be low due to continue degradation occuring in the soil. Thus thee herbicide are not likely to pose a problen of carryover and innjury to susceptible crops. Furthernore injury problens may be solved by using protectants and antidote. The concentration of the herbicide in the soil is variable from laye to laye. This diffeence was explained by variability in soil structure among layes. Soil physical and chemical structure analyse should have helped explain thee diffeence obseved. The large variations obseved in the data may be due to the small size of soil sample. For an expeiment in plots bearing crops, Hormann et all. (1973) suggeted that at least 20 cylindes of soil should be taken and combined for each replication. This numbe seens to be a good compromise between reproducibility and economy. Their study showed also that if thee is a reidue patten in the soil, the sampling must be deigned to obtain repreentative reults. The reults obtained show leaching of the hebicide down the profile. This leaching can reult in ground wate contamination. Since irrigation can not be stopped for productivity reason, farmers should not over irrigate to reduce the amount of herbicide 38 39 leached. Othe factors such as infiltration, evapotranspiration, root absorption and exudation, lateral transport, ve'tical percolation and volatilization may also explain the oveall reults obtained. The complexity and difficulty in intepreting the reults are due to the fact that the length of this study doe not allow sufficient time to appreciate all the natural and weathe-dependent phenomena such as pesitence and leaching. Thee is also a danger of ove'interpreting such data. APPENDICIE 'RESULJS(NFTIHICIHNNMAJIKHKAPBWCIUWALYSESCHFSOHLSALDHUEB Table Al. Concentration of the three pesticides found ion soil samples 24 days before treatment (24 DBT). SAMPLE CONCENTRATION (PPM) SAMPLE CONCENTRATION (PPM) IMI DAN MTBZ METOLA IMI DAN MTBZ METOLA 101-1 0.00 0.07 201-1 0.00 0.07 101-2 NI 0.00 0.07 201-2 NI 0.00 0.09 101-3 0.02 0.05 201-3 0.00 0.10 101-4 0.02 0.05 201-4 0.02 0.17 102-1 0.00 0.03 202-1 0.00 0.10 102-2 NI 0.00 0.20 202-2 NI 0.00 0.18 102-3 0.04 0.26 202-3 0.00 0.45 102-4 0.01 0.15 202-4 0.04 0.10 103-1 0.00 0.01 203-1 0.00 0.10 103-2 NI 0.00 0.17 203-2 NI 0.00 0.05 103-3 0.02 0.2000 203-3 0.09 0.12 103-4 0.04 0.05 203-4 0.07 0.05 104-1 0.00 0.00 204-1 0.00 0.07 104-2 NI 0.00 0.00 204-2 NI 0.00 0.07 104-3 0.03 0.05 204-3 0.00 0.25 104-4 0.02 0.03 204-4 0.01 0.11 105-1 0.01 0.00 205-1 0.00 0.02 105-2 NI 0.00 0.00 205-2 NI 0.00 0.05 105-3 0.09 0.10 205-3 0.00 0.18 105-4 0.05 0.07 205-4 0.00 0.04 MTZ = metribuzin METOLA = metolachlor non identified NI = Table Al.(cont'd) 41 MTZ = metribuzin METOLA = metolachlor NI = non identified SAMPLE CONCENTRATION ( PPM) SAMPLE CONCENTRATION ( PPM) IMIDAN' MTBZ IMIDAN MTBZ METOLA 301-1 0.00 0.05 401-1 . 0.00 0.02 301-2 NI 0.00 0.10 401-2 NI 0.00 0.10 301-3 0.04 0.25 401-3 0.03 0.17 301-4 0.00 0.10 401-4 0.02 0.10 302-1 0.00 0.09 402-1 0.00 0.03 302-2 NI 0.00 0.03 402-2 NI 0.00 0.09 302-3 0.00 0.07 402-3 0.02 0.15 302-4 0.05 0.05 402-4 0.05 0.07 303-1 0.00 0.01 403-1 0.00 0.01 303-2 NI 0.00 0.10 402-2 NI 0.03 0.30 303-3 0.01 0.20 403-3 0.05 0.20 303-4 0.03 0.05 403-4 0.03 0.05 304-1 0.00 0.00 404-1 0.00 0.00 304-2 NI 0.00 0.08 404-2 NI 0.00 0.09 _304-3 0.00 0.20 404-3 0.01 0.20 304-4 0.00 0.05 404-4 0.01 0.02 305-1 0.00 0.05 405-1 0.00 0.05 305-2 NI 0.00 0.07 405-2 0.03 0.06 305-3 0.00 0.08 405-3 0.20 0.06 305-4 0.01 0.07 405-4 0.09 0.08 w _- 42 Table AZ. Concentration of the three pesticides found in soil samples 25 days after treatment (25 DAT). SAMPLE CONCENTRATION (PPM) IMIDAN MTBZ METOLA .8... 101-1 101-2 101-3 101-4 NI 0.00 0.05 0.12 0.22 0.14 0.30 ISAMPLE 201-1 201-2 201-3 201-4 ,,_ 474 CONCENTRATION (PPM) MTZ - metribuzin METOLA = metolachlor NI = non identified IMIDAN MTBZ METOLA 0.01 0.27 NI 0.02 0.15 0.03 0.20 0.00 0.30 0.02 0.25 0.01 0.27 NI 0.02 0.70 0.00 0.16 0.01 0.20 NI 0.00 0.10 0.07 0.20 0.01 0.00 0.00 0.10 0.00 0.20 NI 0.00 0.30 0.00 0.12 0.00 0.09 NI 0.04 0.10 0.01 0.30 0.01 0.05 43 Table hz.(cont'd) J SAMPLE CONCENTRATION (PPM) SAMPLE CONCENTRATION (PPM) IMIDAN MTBZ METOLA IMIDAN MTBZ METOLA .1 MW 301-1 0.00 0.16 401-1 0.00 0.10 301-2 NI 0.02 0.30 401-2 NI 0.00 0.20 301-3 0.00 0.35 401-3 0.03 0.20 301-4 0.00 0.13 401-4 0.03 0.12 302-1 0.01 0.20 402-1 0.01 0.11 302-2 0.02 0.10 402-2 0.00 0.17 302-3 NI 0.02 0.10 402-3 NI 0.02 0.20 302-4 0.00 0.01 402-4 0.00 0.07 303-1 0.00 0.12 403- 0.00 0.12 303-2 NI 0.00 0.25 403-2 NI 0.02 0.40 303-3 0.00 0.27 403-3 0.03 0.25 303-4 0.00 0.02 403-4 0.00 0.07 304-1 0.00 0.09 404-1 0.02 0.05 304-2 0.00 0.22 404-2 0.04 0.18 304-3 NI 0.00 0.20 404-3 NI 0.02 0.22 304-4 0.00 0.13 404-4 0.00 0.05 305-1 0.00 0.07 405-1 0.01 0.12 305-2 NI 0.03 0.17 405-2 NI 0.07 0.13 305-3 0.07 0.18 405-3 0.25 0.10 305-4 0.00 0.05 405-4 0.10 0.10 _ _ MTZ = metribuzin METOLA = metolachlor NI = non identified Table as. Concentration of the three pesticides found in soil samples 87 days after treatment (87 DAT) SAMPLE CONCENTRATION (PPM) IMIDAN MTBz 101-1 101-2 101-3 101-4 NI 0.02 0.01 0.03 SAMPLE CONCENTRATION (PPM) METOLA IMIDAN MTBZ METOLA W :8 0.28 201-1 0.01 0.25 0.16 201-2 NI 0.01 0.16 0.23 201-3 0.00 0.36 0.38 201-4 0.00 0.12 0.27 202-1 0.01 0.16 0.25 202-2 0.03 0.35 0.65 202-3 NI 0.01 0.35 0.16 202-4 0.00 0.12 0.27 203-1 0.00 0.19 0.17 203-2 NI 0.00 0.27 0.24 203-3 0.12 0.46 0.11 203-4 0.00 0.09 0.27 204-1 0.00 0.19 0.17 204-2 0.00 0.09 0.36 204-3 NI 0.00 0.12 0.12 204-4 0.00 0.01 0.09 205-1 0.00 0.09 0.12 205-2 NI 0.00 0.12 0.37 205-3 0.00 0.25 0.07 205-4 0.00 0.10 MTZ = metribuzin METOLA = metolachlor NI = non identified 45 Table A3.(cont’d) SAMPLE CONCENTRATION (PPM) SAMPLE CONCENTRATION (PPM) IMIDAN MTBZ METOLA IMIDAN MTBZ METOLA 301-1 0.00 0.17 401-1 0.01 0.16 301-2 NI 0.00 0.25 401-2 NI 0.00 0.35 301-3 0.04 0.36 401-3 0.00 0.33 301-4 0.03 0.12 401-4 0.00 0.01 302-1 0.01 0.11 402-1 0.01 0.22 302-2 0.00 0.17 402-2 0.01 0.11 302-3 NI 0.00 0.23 402-3 NI 0.00 0.25 302-4 0.00 0.07 402-4 0.00 0.01 303-1 0.00 0.12 403-1 0.00 0.12 303-2 NI 0.00 0.42 402-2 NI 0.07 0.21 303-3 0.00 0.22 403-3 0.10 0.33 303-4 0.00 0.16 403-4 0.00 0.02 304-1 0.02 0.09 404-1 0.00 0.09 304-2 0.04 0.18 404-2 0.00 0.22 304-3 NI 0.00 0.18 404-3 NI 0.03 0.25 304-4 0.00 0.05 404-4 0.00 0.12 305-1 0.01 0.12 405-1 0.00 0.05 305-2 0.07 0.13 405-2 ' 0.00 0.21 305-3 NI 0.13 0.10 405-3 NI 0.00 0.22 305-4 0.00 0.10 405-4 0.00 0.11 MTZ = metribuzin METOLA = metolachlor NI - non identified 46 Table A4. Concentration of the three pesticides found in soil samples 157 days after treatment (157 DAT). - L — SAMPLE CONCENTRATION (PPM) SAMPLE CONCENTRATION(PPM) IMIDAN MTBZ METOLA IMIDAN MTBZ METOLA 101-1 0.01 0.09 201-1 0.01 0.03 101-2 NI 0.00 0.16 201-2 NI 0.03 0.04 101-3 0.01 0.16 201-3 0.08 0.11 101-4 0.00 0.05 201-4 0.00 0.01 102-1 0.00 0.09 202-1 0.01 0.09 102-2 0.00 0.12 202-2 0.02 0.10 102-3 NI 0.00 0.22 l 202-3 NI 0.02 0.10 102-4 0.00 0.11 202-4 0.00 0.01 103-1 0.00 0.12 203-1 0.01 0.12 103-2 NI 0.00 0.12 203-2 NI 0.01 0.16 103-3 0.00 0.07 203-3 0.00 0.16 103-4 0.00 0.02 203-4 0.00 0.08 104-1 0.02 0.12 204-1 0.03 0.13 104-2 0.01 0.12 204-2 0.03 0.13 104-3 NI 0.01 0.07 204-3 NI 0.03 0.16 104-4 0.00 0.02 204-4 0.00 0.08 105-1 0.01 0.14 205-1 0.00 0.07 105-2 NI 0.01 0.15 205-2 NI 0.00 0.12 105-3 0.01 0.15 205-3 0.01 0.13 105-4 0.00 0.10 205-4 0.00 0.11 MTZ = metribuzin METOLA = metolachlor NI a non identified Table A4.(cont'd) 47 SAMPLE CONCENTRATION (PPM) SAMPLE CONCENTRATION (PPM) IMIDAN MTBZ METOLA IMIDAN MTBZ METOLA 301-1 0.01 0.0 3 401-1 0.01 0.15 301-2 NI 0.03 0.03 401'2 NI 0.01 0.09 301-3 0.08 0.12 401-3 0.00 0.09 301-4 0.00 0.01 401-4 0.01 0.01 302-1 0.04 0.06 402'1 0.00 0.00 302-2 0.04 0.12 402-2 0.00 0.00 302-3 NI 0.04 0.12 402-3 NI 0.00 0.00 302-4 0.00 0.10 402-4 0.00 0.00 303-1 0.02 0.10 403-1 0.02 0.01 303“2 NI 0.02 0.08 402-2 NI 0.03 0.12 303-3 0.16 0.12 403-3 0.03 0.12 303-4 0.00 0.10 403-4 0.00 0.07 304-1 0.00 0.12 404-1 0.00 0.08 304-2 0.01 0.12 404-2 0.04 0.12 304-3 NI 0.01 0.00 404-3 NI 0.04 0.13 304-4 0.00 0.00 404-4 0.00 0.07 305-2 NI 0.01 0.10 405-2 NI 0.05 0.12 305-3 0.00 0.10 405-3 0.07 0.05 305-4 0.00 0.00 405-4 0.00 0.05 MTZ a metribuzin METOLA - metolachlor NI 8 non identified APPENDIX B CALCULATED MEAN AND STANDARD DEVIATION FROM CHROMATOGRAPHIC DATA Table 81. Mean concentration of metribuzin measured at different depths in soil sampled before treatment. REPLICATION DEPTH I II III IV #1 0.005 0.000 0.034 0.028 #2 0.000 0.000 0.018 0.028 #3 0.000 0.000 0.010 0.018 #4 0.000 0.006 0.023 0.040 MEAN 0.001 0.002 0.031 0.029 STD.DEV. 0.003 0.003 0.023 0.009 Table 82. Mean concentration of metolachlor measured at different depths in soil sampled before treatment. L REPLICATION DEPTH I II III IV -.If1 0.054 0.08; 0.132 0.070 #2 0.072 0.088 0.220 0.094 #3 0.040 0.076 0.160 0.064 #4 0.000 0.128 0.156 0.064 MEAN 0.042 0.095 0.167 0.073 STD.DEV. 0.031 0.023 0.037 0.014 49 Table 83. Mean concentration of metribuzin measured at different depths in soil sampled 25 days after treatment. DEPTH REPLICATION I II III IV #1 0.002 0.016 0.046 0.000 #2 0.008 0.014 0.046 0.004 #3 0.002 0.016 0.018 0.000 #4 0.008 0.026 0.070 0.026 MEAN 0.005 0.018 0.045 0.008 STD.DEV. 0.004 0.005 0.021 0.120 Table 84. Mean concentration of metolachlor measured at different depths in soil sampled 25 days after treatment (series 892). a i DEPTH REPLICATION I II III IV WM — #1 0.124 0.184 0.265 0.074 #2 0.182 0.164 0.340 0.126 #3 0.124 0.208 0.220 0.068 #4 0.100 0.216 0.194 0.068 MEAN 0.133 0.193 0.255 0.084 STD.DEV. 0.035 0.024 0.064 0.028 50 Table 85. Mean concentration of metribuzin measured at different depths in soil sampled 86 days after treatment (series 893). DEPTH REPLICATION I II III IV #1 0.010 0.012 0.074 0.020 #2 0.004 0.003 0.026 0.020 #3 0.008 0.022 0.034 0.008 #4 0.004 0.016 0.026 0.000 MEAN 0.007 '0.015 0.040 0.012 STD.DEV. 0.003 0.006 0.023 0.009 Table 86. Mean concentration of metolachlor measured at different depths in soil sampled 86 days after treatment (series 893). DEPTH REPLICATION I II III IV #1 0.738 0.854 0.370 0.784 #2 0.683 0.704 0.308 0.280 #3 0.514 0.224 0.218 0.100 #4 0.128 0.220 0.293 0.076 MEAN 0.516 0.501 0.297 0.310 STD.DEV. 0.276 0.327 0.062 0.329 51 Table 87. Mean concentration of metribuzin measured at different depths in soil sampled 153 days after treatment (series 89F). DEPTH REPLICATION I II III IV an lasaggggsg #1 0.007 0.022 0.028 0.002 #2 0.066 0.022 0.058 0.000 #3 0.010 0.018 0.028 0.000 #4 0.088 0.004 0.080 0.000 MEAN 0.043 0.017 0.049 0.000 STD.DEV. 0.041 0.008 0.025 0.001 1.”-Mm____ 1.". _._ ____. Table 88. Mean concentration of metolachlor measured at different depths in soil sampled 153 days after treatment (series 89F). DEPTH - REPLICATION I II III Iv #1 0.083 0.113 0.123 0.033 #2 0.064 0.090' 0.303 0.036 #3 0.088 0.110 0.132 0.052 #4 0.094 0.112 0.120 0.060 MEAN 0.082 0.106 0.172 0.045 STD.DEV. 0.013 0.011 0.090 0.013 Table 39. 52 sampling period at four soil depths. Metribuzin concentration in soil at different DEPTH SAMPLING SERERIES I II III IV 24 DBT 0.001 0.002 0.031 0.029 25 DAT 0.005 0.018 0.045 0.008 87 DAT 0.007 0.015 0.040 0.012 157 DAT 0.043 0.017 0.049 0.000 MEAN 0.018 0.017 0.045 0.007 STD.DEV. 0.021 0.001 0.005 0.006 Table 310. Metolachlor concentration in soil at different sampling period at four soil depths. DEPTH . SAMPLING PERIOD I II III IV ‘ 24 DBT 0.042 0.095 0.167 0.073 25 DAT 0.133 0.193 0.255 0.084 87 DAT 0.516 0.501 0.297 0.310 157 DAT 0.082 0.106 0.172 0.045 MEAN 0.244 0.266 0.241 0.146 STD.DEV. 0.237 0.208 0.064 0.143 53 APPENDIX C PLOTS OP THE RESULTS Figure CI. Mean concentration Of metribuzin in different soil layers. Mean with the same letter at the same sampling period are not significantly different at the 0.05 significance level according to Duncans's Multiple Range test. 0.05 ' I 24 DBT I25 DAT 2 I87 DAT 0'04 I157 DAT 0.03 ‘ 0.02 ' 0.01 ' CONCENTRATION (PPM) 0.00 E Figure C2. Mean concentration of metolachlor in different soil layers. Mean with the same letter at the same sampling period are not significantly different at the 0.05 significance level according to Duncans’s Multiple Range test. 0.6 - A A ‘ E A I 24 DBT n_ 0 5 - 25 DAT n_ 87 DAT v 157 DAT z 0.4 — 2 r; D: l— 2 0.2 - |.|.l C ; O ’ ; Z O O DEPTH 55 Figure C3. Mean concentration of metribuzin in different layers for each sampling period. Mean with the same letter at the same DAT are not significantly different at the 0.05 significance level according to Duncans’s Multiple Range test. 0.05 - A I cm DE- 0—15 9.: 0.04 - g Q 0.03 - ig l— i E 7; LL] g; 0 0.01 " % 2 ¢ 0 g f. 24 DBT 25 DAT 87 DAT 157 DAT 56 Mean concentration of metolachlor in different layers for each sampling period. Mean with the same letter at the same DAT are not significantly different at the 0.05 significance level according to Duncans’s Multiple Range test. Figure c4 . DAT .......... 157 161,. w. T /$\. qu9m n51...“ $1.. ....$<>). 2.1“? ~ 7 AA'i/ //////////////////////%fl/////////////////////4/// 3 .wu. H mm Mm mmmm 4” emem mmww m lwmfi m _ ‘_ 2 22%: 22.252328 57 Figure C5. Metribuzin concentration found in soil samples ammmwouéfi 000.00 0“” --o--15-flau —o—Muu «no-"wan 58 Figure cs. Metolachlor concentration found in soil samples 0.6 T axmmmwm 0.1 7” ........... /.. \ ‘.\ >’°-.::F"" oooooooo -. ‘.\ ‘ a. “o o ' = : I 24 GET 25 DAT B7 DAT 153 DAT SOIL SAMPLING PERI“) -"--owun --°-- 1540c": —"—30-45¢m -°°-"45-00un 59 APPENDIX D CHROMATOGRAMS OF THE ANALYSES 00:22:54 INJECT CHRHHEL 8 00822854 F ILE 0. HEWD 0. RUN 2 mm 2 PER!“ BRERX RT RREB DC a 22:32; 2:: 33:2: :: TOTRL 180. 89884 Figure D1. Chromatogram of 0.4 ppm standard solution of imidan (FPD, 5 mode). 01827858 INJECT CHRHHEL R 60 h. to lbtahollte Ens m Imnwn a ram. luau at - 1 s. 59 o. as 2 0.079 0.25 8 mm 3 e. 45 o. 31 “ 4 o. 132 a. 34 j “3 s o. 171 o. 33 ' 6 .4 as: 8 7 12.30:. a. 6? B as do 9 . 1, 1‘ ' 10 51. 515 1. .55 u a. 190 2. 62 . 12 a. 058 3. 59 13 364 Figure D2. Chromatogram of soil extract 01827858 RUN .2 INDEX 82 (FPD, 8 mode). 61 Metolachlor Metribuzin .fl STOP Rmii l7 amen RT ammvnmt NVflT mum: 0.61 558729 88 0.32! 25.933 5.64 242270 PR 0.225 10.064 0.09 277600 P8 0.268 @357 Figure D3. Chromatogram of mixed Standard solution of metribuzin and metolachlor (ECD) 62 Metribuzin Metolachlor a 1tii' j. LU RW!! 48 GREAZ . RT amalnms “VH1 M532 0.70 571870 P? 0.387 29.474 1.87 51120 P? 0 111 2 635 5.63 352290 PB 01264 101157 8.50 156040 Y? 0.287 8.042 8.94 507770 V? 0.348 26.170 10.19 49078 P? 0.220 2.530 10.83 71580 9? 0.245 3.689 11.41 140730 VP 0.317 7.253 11.76 39776 P9 0,130 2.050 TU"“.NM¥F un0am ML.HIHNF=LONNEHN Figure D4. Chromatogram of soil extract (ECD) STOP LIST OF REFERENCES LITERATURE CITED Ahmed, M.K. and Casida, T.E. ”Metabolism of some organophosphorus insecticides by microorganisms." J. Econ. Entomol. 51(1958): 59-63. 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