Exposures of Aquatic Organisms to the Organophosphorus Insecticide, Chlorpyrifos Resulting from Use in the United States - Reviews of Environmental Contamination and Toxicology - page 99

Fig. 8 Influence of aerobic soil metabolism half-life on 90th centile 96-h time-weighted mean
estimated environmental concentrations for crop/label sensitivity analysis
Assessment of vulnerability for runoff of CPY in California . An assessment of vul-
nerability specific to California was conducted for several reasons. First, because of
the large volume of CPY used in that state (Fig. 1 ); second, the historical detections
of CPY reported from monitoring studies conducted in the state (CDPR 2012a ;
CEPA 2011a , b ; USGS 2013 ); third, the availability of detailed records on pesticide
applications from the California Department of Pesticide Regulation's (CDPR)
Pesticide Use Reporting (PUR) database (CDPR 2012b ); and fourth, because of the
intensive use of furrow and flood irrigation on crops registered for use with CPY in
the state (Orang et al. 2008 ). Losses in furrow and flood irrigation tail-water have
been identified as a major cause of transport of pesticides, including CPY, to non-
target aquatic systems (Budd et al. 2009 ; Gill et al. 2008 ; Long et al. 2010 ; Starner
et al. 2005 ). This pathway could not be simulated with the National Pesticide
Assessment (NPAT) model.
The assessment of vulnerability for California was conducted using the Co-
occurrence of Pesticides and Species Tool (CoPST), a modeling framework
developed by the California Department of Water Resources (CDWR) to evaluate
the potential spatial and temporal co-occurrence of pesticides with threatened or
endangered aquatic and semi-aquatic species (Hoogeweg et al. 2011 ). The frame-
work integrates a number of databases necessary for temporal and spatial analysis,
including historical records of pesticide use and soil properties, weather records,
agronomic data, and species habitat for the Sacramento River, San Joaquin, and the
San Francisco Bay Delta Estuary watersheds (SI Appendix C). Using the modeling
framework, daily pesticide runoff and erosion losses in the Central Valley of CA
were estimated for historical CPY applications to agricultural fields. Approximately
47,860 historical applications of CPY were simulated for the period 2000-2008.