Atrazine environmental fate

USEPA (2007). White paper on the potential for atrazine to affect amphibian gonadal development, in support of an Interim Reregistration Eligibility Decision on Atrazine. Submitted to FIFRA Scientific Advisory Panel, October 9-12. Office of Prevention, Pesticides, and Toxic Substances, Office of Pesticide Programs, Environmental Fate and Effects Division. Washington, DC. September 21. 

Bacci, E., A. Renzoni, C. Gaggi, D. Calamari, A. Franchi, M. Vighi, and A. Seven (1989). Models, field studies, laboratory experiments An integrated approach to evaluate the environmental fate of atrazine (s-triazine herbicide). Agric. Ecosys. Environ., 27 513-522. Baker, J.L. and J.M. Laflen (1979). Runoff losses of surface-applied herbicides as affected by wheel tracks and incorporation../. Environ. Qual., 8 602-607. 

Figure 3 Distributions of atrazine, chlorpyrifos, and chloropicrin among air, surface water, soils, and aqueous sediments, based on fugacity calculations. Percentages sum to less than 100% because partitioning into fish and suspended sediment was not accounted for (Mackay et al. (1997) reproduced hy permission of CRC Press, Lewis Publishers from Illustrated Handbook of Physical-Chemical Properties and Environmental Fate for Organic...

Again, it is important to emphasise that the environmental fate of a chemical substance is a choice variable for the chemical producer. All chemical substances couldbe made to decay instantaneously, andthusnot accumulate, but this would imply zero effectiveness. The problem is that the cost of in-built persistence is implied accumulation. The studies on affinity indicate the route of accumulation that such persistence will take. The organochlorines (such as D D T) are fat soluble and hence accumulated within the food chain. Substances such as atrazine are more water soluble and hence are more problematic with respect to groundwater. 

Most soil-boimd pesticides are less hkely to volatihze or to leach through the soil. They are also less easily taken up by plants. In terms of environmental fate, bound residues can be significant and may result in the underestimation of chemical half-life. A nine-year outdoor study showed that soil residues contained as high as 50-60% of the initial apphed radioactivity of C-atrazine [38,39], and some transformation products of atrazine persisted for 9 years in outdoor conditions [39]. Most of the boimd residues were the hydroxy analogues of atrazine and their dealkylated products. 

The possible environmental fate of chemical transformation products is dependent on various factors. Once formed under certain conditions, transformation products are distributed between four major environmental media air, water/sediment, soil, and biota. Therefore, environmental fate of transformation products is primarily influenced by the properties of the chemical and conditions of environmental media. Differences in fate are clearly due to variance in environmental media with different physical, chemical, and biological properties including temperature, soil type, light intensity, organic matter, moisture, pH, aeration, and microbial activity. For example, mobilities of flve atrazine transformation products, deethylatrazine, deisopropyl-atrazine, didealkyatrazine, hydroxyatrazine, and ammeline, were negatively correlated with soil organic matter content and positively correlated with sand content [43]. 

Bintein, S. and Devillers, J. (1996). Evaluating the environmental fate of atrazine in France. Chemosphere 32, 2441-2456. 

Al ough alachlor is no longer used in the U.S., the three chemical compounds have very similar structural (Figure 1) and chemical properties. Alachlor degradataion data may be useful as a model for this chemical class. Caution must be used in interpolating these data however since the ESA metabolite of metolachlor is formed more slowly and at lower concentrations in soil (18). The objective of this study was to compare atrazine and alachlor sorption, mineralization, and degradation potential, processes that are major contributors to the environmental fate of pesticides, from surface soil to aquifer sediments in laboratoiy studies. In addition, ctegradation of alachlor was compared under aerobic and anaerobic conditions. 

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