Pesticides problem soils

The problems relating to increased contamination levels and/or insufficient sensitivity may be overcome by using matrix-solid phase dispersion, MS detection in selected ion monitoring (SIM) mode, and/or large volume injection. An example of combined analysis that utilizes specific detection is shown in Fig. 2.6. It entails simultaneous analyses of PAHs, PCBs, chlorobenzene, and organochlorine pesticides in soil. 

One approach to restoration of herbicidal activity in problem soils has been the use of microbial/enzymatic inhibitors (20). Stauffer Chemical Company (now ICI Americas) has provided leadership for the agrochemical industry in this area and provided potential inhibitors to university scientists for validation. Kaufman et al. (21) had earlier suggested the use of inhibitors to improve the performance of herbicides with short residual lives in soils. Kaufman et al. (3) discussed the role of pesticides as inducers, substrates, and/or inhibitors of degradative enzymes in soil microorganisms and gave selected examples of specific pesticides as inducers and others as inhibitors of certain enzymes. They also considered the potential of "multiproblem" soils. 

Pesticide-treated soils may be stored for various lengths of time before they are used in laboratory studies. With problem soils, one wonders if they lose their degradative potential upon storage. To address this question, butylate-history soils were... 

General Assay Urease Activity in Problem Soils. Tu (14) examined urease activity in clay loam soils incubated with various pesticides. He observed increased levels of microbial urease activity with carbofuran- and ethoprop-amended soils (Table I). These results suggest that activity levels of specific indigenous soil enzymes may be influenced by certain pesticides applied to... 

One recent agricultural phenomenon that may be elucidated by such basic research Is the manner In which problem soils arise. In these soils, the microbial population degrades applied pesticides so rapidly that pesticide efficacy Is lost (30). Presumably, the repeated application of a particular pesticide acts as an enrichment procedure, constantly selecting for Increased numbers of the particular microorganisms that can metabolize the pesticide and derive some nutritional benefit from It. Several basic questions that need to be answered In order to understand this process. First, where do the genes that encode the pesticide degradation enzymes... 

Hydrolyzed wastes could be stored until a cooperatively owned or privately rented processor could be brought around to finish the job. An additional safety factor Incorporated Into such a multlstep process Is that the organisms that produce these enzymes derive little or no nutritional benefit from the metabolism of the pesticide. Since they cannot grow on the pesticide they should not propagate In field situations where some pesticide "staying power Is required. Thus, use of such microorganisms does not threaten to create new problem soils situations. 

Chemical, cultural, and mechanical weed control practices have been relatively successful ia reducing yield losses from weeds (448). However, herbicide-resistant weed populations, soil erosion, pesticide persistence ia the environment, and other problems associated with technologies used (ca 1993) to control weeds have raised concerns for the long-term efficacy and sustainability of herbicide-dependent crop production practices (449). These concerns, coupled with ever-increasing demands for food and fiber, contribute to the need for innovative weed management strategies (450). 

Cultivation of soil has and will continue to be an important means of controlling weeds (1). However, extensive soil cultivation leads to various problems such as losses of soil, soil moisture and nutrients. This results in water pollution by both the soil itself and pesticides and nutrients associated with it (2, 3, 4). Minimum or no-till cropping systems can reduce these problems because various crop residues (i.e., mulch) are left on the soil surface with a minimum of soil disturbance in planting the crop. 

The threat of pesticides impact on the environment in Russia and other CIS countries has not diminished because they were used less in the 1990s. The long-term influence of pesticides on the soil not only has not decreased, but has become more apparent. Until recently, OCP soil contamination, significantly exceeding MPC, has been observed in the Krasnodar Krai, in the Republics of Central Asia, Moldova, Kazakhstan, in Ukraine, and in other regions [35]. DDT and its metabolites cause the most significant environmental problems, especially where perennial and industrial crops are grown. 

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