Urban pesticide use may lead to pollution in urban watersheds that raises ecotoxicological concerns. In California, pyrethroids and fiproles (fipronil and its degradates) are the two groups of pesticides of particular interest because of their high use and high toxicity to aquatic invertebrates. This study aims to understand the seasonality in those chemical signals in urban watersheds so that monitoring programs can be optimized to achieve their specific goals.  We investigate the three components that influence the offsite transport of these chemicals to urban watersheds: (1) the pollution source – urban pesticide use patterns, (2) the main driving force for transport – precipitation and irrigation, and (3) the transport dynamics – environmental fate properties. The seasonality of the pollution source and driving force are compared to the seasonality in those chemicals’ observed environmental concentrations in urban watersheds.  The differential responses of those chemicals to the seasonality of the pollution source and driving force can be explained by their difference in environmental fate properties, in particular, the hydrophobicity or the ability to attach to particulate matters.  With this understanding, we can predict the seasonality of pesticides signals from the values of those three components and design monitoring programs with varying temporal frequency to capture the worst case or the average condition.<br/>

Seasonality in pesticide signals in California’s urban watersheds

254th National Meeting (2017)

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