Pesticide concentrations in water and sediment and associated invertebrate toxicity in Del Puerto and Orestimba Creeks, California, 2007–2008

Abstract

The California's San Joaquin River and its tributaries including Orestimba (ORC) and Del Puerto (DPC) Creeks are listed on the 2006 US EPA Clean Water Act §303(d) list for pesticide impairment. From December 2007 through June 2008, water and sediment samples were collected from both creeks in Stanislaus County to determine concentrations of organophosphorus (OP) and pyrethroid insecticides and to identify toxicity to Ceriodaphnia dubia and Hyalella azteca. OPs were detected in almost half (10 of 21) of the water samples, at concentrations from 0.005 to 0.912 μg L(-1). Diazinon was the most frequently detected OP, followed by chlorpyrifos and dimethoate. Two water samples were toxic to C. dubia; based on median lethal concentrations (LC50), chlorpyrifos was likely the cause of this toxicity. Pyrethroids were detected more frequently in sediment samples (18 detections) than in water samples (three detections). Pyrethroid concentrations in water samples ranged from 0.005 to 0.021 μg L(-1). These concentrations were well below reported C. dubia LC50s, and toxicity was not observed in laboratory bioassays. Cyfluthrin, bifenthrin, esfenvalerate, and λ-cyhalothrin were detected in sediment samples at concentrations ranging from 1.0 to 74.4 ng g(-1), dry weight. At DPC, all but one sediment sample caused 100% toxicity to H. azteca. Based on estimated toxicity units (TUs), bifenthrin was likely responsible for this toxicity and λ-cyhalothrin also contributed. At ORC, survival of H. azteca was significantly reduced in four of the 11 sediment samples. However, pyrethroids were detected in only two of these samples. Based on TUs, bifenthrin and λ-cyhalothrin likely contributed to the toxicity.

Exposures of Aquatic Organisms to the Organophosphorus Insecticide, Chlorpyrifos Resulting from Use in the United States

“…The primary crops in the watershed are hay (12.0%), cherries (11.1%), alfalfa (8.1%), and corn (2.7%) Orestimba Creek in the San Joaquin River basin of California (Fig. 12) was selected because of the high density of use of CPY in the watershed, frequent detections of CPY in ambient monitoring programs (Domagalski and Munday 2003;Ensminger et al 2011;Zhang et al 2012), and because an existing model setup of the watershed was available from the University of California (Luo et al 2008;Luo and Zhang 2010). The watershed drains 55,998 ha from the mountainous area in the west, where brush and scrubland is predominant, into the agriculturally intensive valley floor.…”

Risks to Aquatic Organisms from Use of Chlorpyrifos in the United States

“…In a few cases, observed toxicity in sediments collected from agricultural drains, creeks, and rivers in California was linked to the presence of CPY (Phillips et al 2012 ;Weston et al 2012 ). However, in most locations CPY contributed less to toxicity of sediments than other pesticides such as pyrethroids (Amweg et al 2006 ;Ding et al 2010 ;Ensminger et al 2011 ;Phillips et al 2006 ).…”

Ecological Risk Assessment for Chlorpyrifos in Terrestrial and Aquatic Systems in the United States

“…In a few cases, observed toxicity in sediments collected from agricultural drains, creeks, and rivers in California was linked to the presence of CPY (Phillips et al 2012 ;Weston et al 2012 ). However, in most locations CPY contributed less to toxicity of sediments than other pesticides such as pyrethroids (Amweg et al 2006 ;Ding et al 2010 ;Ensminger et al 2011 ;Phillips et al 2006 ).…”

“…The primary crops in the watershed are hay (12.0%), cherries (11.1%), alfalfa (8.1%), and corn (2.7%) Orestimba Creek in the San Joaquin River basin of California (Fig. 12) was selected because of the high density of use of CPY in the watershed, frequent detections of CPY in ambient monitoring programs (Domagalski and Munday 2003;Ensminger et al 2011;Zhang et al 2012), and because an existing model setup of the watershed was available from the University of California (Luo et al 2008;Luo and Zhang 2010). The watershed drains 55,998 ha from the mountainous area in the west, where brush and scrubland is predominant, into the agriculturally intensive valley floor.…”