The OECD 307 Guideline ‘Aerobic and Anaerobic Transformation in Soil’ and the EPA Guideline OCSPP 835.4100 ‘Aerobic Soil Metabolism’ define the degradation rate of an organic chemical in soil. The tests are conducted in field fresh moist soils at a constant temperature of 20<sup>o</sup>C under dark conditions. These parameters allow for consistent testing between studies, however these tests do not assess the simultaneous degradation contributed by natural sunlight that can occur in the field for some pesticides that are on the soil surface at least initially.  A soil metabolism study design based on the above guidelines was modified in this experiment by setting up treated soil samples with [<sup>14</sup>C]atrazine and exposing them to artificial sunlight for several days prior to introducing the illuminated samples to additional fertile soil. Comparisons of the rate of degradation in the illuminated samples will be compared to treated soils incubated solely in the dark. This study design provides an example of higher tiered testing to assess a chemical’s persistence.

Photo-enhanced soil metabolism of atrazine

256th National Meeting (2018)

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