Environmental Modeling and Exposure Assessment of Sediment-Associated Pyrethroids in an Agricultural Watershed

Synthetic pyrethroid insecticides have generated public concerns due to their increasing use and potential effects on aquatic ecosystems. A modeling system was developed in this study for simulating the transport processes and associated sediment toxicity of pyrethroids at coupled field/watershed scales. The model was tested in the Orestimba Creek watershed, an agriculturally intensive area in California' Central Valley. Model predictions were satisfactory when compared with measured suspended solid concentration (R2 = 0.536), pyrethroid toxic unit (0.576), and cumulative mortality of Hyalella azteca (0.570). The results indicated that sediment toxicity in the study area was strongly related to the concentration of pyrethroids in bed sediment. Bifenthrin was identified as the dominant contributor to the sediment toxicity in recent years, accounting for 50–85% of predicted toxicity units. In addition, more than 90% of the variation on the annual maximum toxic unit of pyrethroids was attributed to precipitation and prior application of bifenthrin in the late irrigation season. As one of the first studies simulating the dynamics and spatial variability of pyrethroids in fields and instreams, the modeling results provided useful information on new policies to be considered with respect to pyrethroid regulation. This study suggested two potential measures to efficiently reduce sediment toxicity by pyrethroids in the study area: [1] limiting bifenthrin use immediately before rainfall season; and [2] implementing conservation practices to retain soil on cropland.

[1]  Jeffrey G. Arnold,et al.  Soil and Water Assessment Tool Theoretical Documentation Version 2009 , 2011 .

[2]  M. O’Malley,et al.  Pyrethroid illnesses in California, 1996-2002. , 2006, Reviews of environmental contamination and toxicology.

[3]  Minghua Zhang,et al.  Pyrethroid insecticide concentrations and toxicity in streambed sediments and loads in surface waters of the San Joaquin Valley, California, USA , 2010, Environmental toxicology and chemistry.

[4]  K. Kuivila,et al.  Assessing the occurrence and distribution of pyrethroids in water and suspended sediments. , 2009, Journal of agricultural and food chemistry.

[5]  T. Backhaus,et al.  A general best‐fit method for concentration‐response curves and the estimation of low‐effect concentrations , 2001, Environmental toxicology and chemistry.

[6]  Gerald T. Ankley,et al.  Methods for measuring the toxicity and bioaccumulation of sediment-associated contaminants with freshwater invertebrates , 1994 .

[7]  F. Spurlock,et al.  Pesticide concentrations in water and sediment and associated invertebrate toxicity in Del Puerto and Orestimba Creeks, California, 2007–2008 , 2011, Environmental monitoring and assessment.

[8]  David R. Maidment,et al.  Geographic Information Systems (GIS)‐based spatially distributed model for runoff routing , 1999 .

[9]  Liwang Ma,et al.  Test of the Root Zone Water Quality Model (RZWQM) for predicting runoff of atrazine, alachlor and fenamiphos species from conventional-tillage corn mesoplots. , 2004, Pest management science.

[10]  Minghua Zhang,et al.  Management-oriented sensitivity analysis for pesticide transport in watershed-scale water quality modeling using SWAT. , 2009, Environmental pollution.

[11]  Xiusheng Yang,et al.  Dynamic modeling of chemical fate and transport in multimedia environments at watershed scale-I: theoretical considerations and model implementation. , 2007, Journal of environmental management.

[12]  D. M. Whitacre,et al.  Reviews of Environmental Contamination and Toxicology , 2007 .

[13]  Minghua Zhang,et al.  Dynamic modeling of organophosphate pesticide load in surface water in the northern San Joaquin Valley watershed of California. , 2008, Environmental pollution.

[14]  W. G. Knisel,et al.  GLEAMS: Groundwater Loading Effects of Agricultural Management Systems , 1987 .

[15]  M. Lydy,et al.  Distribution and toxicity of sediment-associated pesticides in agriculture-dominated water bodies of California's Central Valley. , 2004, Environmental science & technology.

[16]  D. Weston,et al.  Use and toxicity of pyrethroid pesticides in the Central Valley, California, USA , 2005, Environmental toxicology and chemistry.

[17]  Jeffrey G. Arnold,et al.  Model Evaluation Guidelines for Systematic Quantification of Accuracy in Watershed Simulations , 2007 .

[18]  Steven C. Chapra,et al.  QUAL2K: A Modeling Framework for Simulating River and Stream Water Quality , 2004 .

[19]  Minghua Zhang,et al.  A geo-referenced modeling environment for ecosystem risk assessment: organophosphate pesticides in an agriculturally dominated watershed. , 2009, Journal of environmental quality.

[20]  M. Lydy,et al.  Identifying the cause and source of sediment toxicity in an agriculture‐influenced creek , 2008, Environmental toxicology and chemistry.

[21]  D. A. Laskowski.  Physical and chemical properties of pyrethroids. , 2002, Reviews of environmental contamination and toxicology.

[22]  L. Epstein,et al.  Patterns of pesticide use in California and the implications for strategies for reduction of pesticides. , 2003, Annual review of phytopathology.