Pesticides in the environment

Environmental Chemistry. Requirements for data on pesticides in the environment include both laboratory and field studies. The purpose of these studies is to identify and assess the potential ha2ards associated with each use of a pesticide in the environment in which it is to be used (20). 

For those pesticides which are utilized as microbial growth substrates, sigmoidal rates of biodegradation are frequentiy observed (see Fig. 2). Sigmoidal data are more difficult to summarize than exponential (first-order) data because of their inherent nonlinearity. Sigmoidal rates of pesticide metabohsm can be described using microbial growth kinetics (Monod) however, four kinetics constants are required. Consequentiy, it is more difficult to predict the persistence of these pesticides in the environment. 

Persistence of pesticides in the environment is controlled by retention, degradation, and transport processes and their interaction. Retention refers to the abihty of the soil to bind a pesticide, preventing its movement either within or outside of the soil matrix. Retention primarily refers to the sorption process, but also includes absorption into the soil matrix and soil organisms, both plants and microorganisms. In contrast to degradation that decreases the absolute amount of the pesticide in the environment, sorption processes do not affect the total amount of pesticide present in the soil but can decrease the amount available for transformation or transport. 

Transport processes describe movement of the pesticide from one location to another or from one phase to another. Transport processes include both downward leaching, surface mnoff, volatilization from the soil to the atmosphere, as weU as upward movement by capillary water to the soil surface. Transport processes do not affect the total amount of pesticide in the environment however, they can move the pesticide to sites that have different potentials for degradation. Transport processes also redistribute the pesticide in the environment, possibly contaminating sites away from the site of apphcation such as surface and groundwater and the atmosphere. Transport of pesticides is a function of both retention and transport processes. 

Desorption is the reverse of the sorption process. If the pesticide is removed from solution that is in equdibrium with the sorbed pesticide, pesticide desorbs from the sod surface to reestabUsh the initial equdibrium. Desorption replenishes pesticide in the sod solution as it dissipates by degradation or transport processes. Sorption/desorption therefore is the process that controls the overall fate of a pesticide in the environment. It accomplishes this by controlling the amount of pesticide in solution at any one time that is avadable for plant uptake, degradation or decomposition, volatilization, and leaching. A number of reviews are avadable that describe in detad the sorption process (31—33) desorption, however, has been much less studied. 

Brown, A.W.A. (1971). Pest resistance to pesticides In Pesticides in the Environment, R. White-Stevens (Ed.) Dekker New York, 437-551. 

Edwards, C.A. (1973). Persistent Pesticides in the Environment, 2nd edition. Cleveland, OH CRC Press. 

Warner, R.P., Peterson, K.K., and Borgman, L. (1966). Behavioural pathology in fish a quantitative study of sublethal pesticide intoxication. In Pesticides in the Environment and Their Effects on Wildlife. N.W. Moore (Ed.) Journal of Applied Ecology 3 (Supplement), 223-248. 

Racke KD, JR Coats (1990) Enhanced Biodegradation of Pesticides in the Environment. American Chemical Society Symposium Series 426. American Chemical Society, Washington, DC. 

Dick WA, RO Ankumah, G McClung, N Abou-Assaf (1990) Enhanced degradation of S-ethyl A, A -dipropyl-carbamothioate in soil and by an isolated soil microorganism. In Enhanced Bio degradation of Pesticides in the Environment (Eds KD Racke and JR Coats), pp 98-112. American Chemical Society Symposium Series 426, American Chemical Society, Washington, DC. 

The need to understand the fate of pesticides in the environment has necessitated the development of analytical methods for the determination of residues in environmental media. Adoption of methods utilizing instrumentation such as gas chro-matography/mass spectrometry (GC/MS), liquid chromatography/mass spectrometry (LC/MS), liquid chromatography/tandem mass spectrometry (LC/MS/MS), or enzyme-linked immunosorbent assay (ELISA) has allowed the detection of minute amounts of pesticides and their degradation products in environmental samples. Sample preparation techniques such as solid-phase extraction (SPE), accelerated solvent extraction (ASE), or solid-phase microextraction (SPME) have also been important in the development of more reliable and sensitive analytical methods. 

Even before a method is developed for detecting the presence of a pesticide or pesticides in the environment, the level of sensitivity in the method that will be needed for fate and monitoring studies to adequately portray the behavior of the analytes in the environment must be assessed. For example, in surface water monitoring programs. 

Monitoring pestitsidov v obyektakh prirodnoy sredy Rossiyskoy Federatsii Yezhegodnik. Kn. 1/2 (Monitoring Pesticides in the Environment of the Russian Federation Yearbook. Book 1/2). Obninsk NPO Taifun, 1992. 425 pp. 

Reinert, J. L., "Estimating the Maximum Concentration of Pesticides in the Environment as a Consequence of Specific Events" October 1, 1980, Environmental Fate Branch, U.S. EPA. 

Dick, W.A., Ankumah, R.O., McCltmg, G, and Abou-Assaf, N. Etrhanced degradation of 5-ethyl A,lV-dipropylcarbamothioate in soil and by an isolated soil nricroorganism in Enhanced Biodegradation of Pesticides in the Environment ACS Symposium Series 426, Racke, K.D. and Coats, J.R., Eds. (Washington, DC American Chenrical Society, 1990), pp. 98-112. 

Kawamoto, K. and Urano, K. Parameters for predicting fate of organochlorine pesticides in the environment (I) octanol-water and air-water partition coefficients, Chemosphere, 18(9/10) 1987-1996, 1989. 

Pesticide registrants must also submit environmental fate and effects data to the EPA as part of an application for pesticide registration. The EPA uses such environmental data to characterize the persistence and partitioning of a pesticide in the environment and the pesticide s environmental metabolites and degradates. This information is used by the EPA to assess the potential for human exposure via drinking water contamination and environmental exposure of organisms such as fish, wildlife, and plants to the pesticide or its metabolites. 

A device can be inserted between the column and detector to automate the reaction, or reactions, of a fluorescent reagent with the eluted analyte to render it fluorescent. This principle is used to measure trace carbamates (pesticides) in the environment. The compound is reacted with sodium hydroxide then o-phthalalde-hyde, which transforms the methylamine group into a fluorescent derivative (Fig. 3.16). 

GW Aherne. Immunoassays for the measurement and detection of pesticides in the environment. In G Marshall, D Atkinson, eds. Molecular Biology Its Practice and Role in Crop Protection. Surrey, UK British Crop Protection Council, 1991, pp 59-78. 

The ways in which microorganisms affect the fate of. y-triazine herbicides and, in a larger sense, all organic pesticides in the environment, are the subject of intense investigation. Among the pesticides, atrazine represents one of the most extensively investigated compounds. 

Matsumura, F. (1982). Degradation of pesticides in the environment by microorganisms and sunlight. In F. Matsumura and C.R. Murti Krishna, eds., Biodegradation of Pesticides. New York Plenium Press, pp. 67-87. 

Biological Impact of Pesticides in the Environment. Proc. Symp. Aug 18-20, 1969 Oregon State Univ., Corvallis, OR. James W. Gillett (Ed.), Environmental Health Sciences Series No. 1. Oregon State U. Press, Corvallis (1970) 6 parts I. Transport and Accumulation, 26p. II. Impact of Chlorinated Hydrocarbons on Birds, 38p. III. Banquet Session 1 D.G. Crosby, "Chemical Ecology and Man" pp.75 ... 

White-Stevens, R. 1977. Pesticides in the Environment. Warszawa PWRiL. 

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