The use of sediment toxicity identification evaluation methods to evaluate clean up targets in an urban estuary

Abstract

The Ballona Creek Estuary (BCE) in Los Angeles, California, is in a highly urbanized watershed, is contaminated by a variety of chemicals, and has prevalent sediment toxicity. Sediment cleanup targets for BCE have been established for Cu, Cd, Pb, Zn, chlordane, DDTs, PCBs, and PAHs, based on sediment quality guidelines. A sediment toxicity identification evaluation (TIE) was conducted to examine how these targets corresponded to toxicity observed with the estuarine amphipod Eohaustorius estuarius. Whole sediment and porewater TIEs were used to identify the cause of toxicity. Passive samplers were deployed to determine the bioavailable fraction of contaminants. Spiked sediment tests were conducted to determine the thresholds of toxicity for selected constituents. Toxicity was found to be widespread but temporally and spatially variable. Whole sediment and porewater TIEs both indicated pyrethroid pesticides were the most likely contaminant group contributing to the toxicity. Concentrations of the chemicals listed for cleanup were found to often exceed target values but were not observed at concentrations likely to cause toxicity. Bioavailable fractions of the target chemicals quantified using passive samplers did not exceed toxicity thresholds. Spiked sediment tests established 10 day LC50s for 4,4' DDE, 4, 4' DDT, α-chlordane, and cyfluthrin at >3050 μg/g, 266 μg/g, >2120 μg/g, and 0.33 μg/g organic carbon (OC), respectively. The cyfluthrin LC50 was within the range of concentrations observed in the estuary sediments, but LC50s for the other 3 chemicals were orders of magnitude greater than observed levels. The combination of TIE, sediment chemistry and the results from spiked sediment exposures indicate pyrethroid pesticides are more likely the cause of the observed toxicity than any of the contaminants targeted for cleanup. The results of this study indicate the importance of using a TIE approach to determine chemicals of concern and dose-response information to set cleanup targets, rather than using sediment quality guidelines. Integr Environ Assess Manag 2014;10:260-268. © 2013 SETAC.

Using spatial and temporal variability data to optimize sediment toxicity identification evaluation (TIE) study designs

“…This, along with the low sensitivity of E. estuarius to metals (e.g., Cu LC50 > 1000 mg/L; McPherson and Chapman ) and the presence of plentiful metal‐binding sulfides, reducing metals bioavailability (Di Toro et al ), indicates that metals were not a cause of the observed toxicity. While chlordanes, DDTs, and PCBs were at high concentrations relative to other southern California sites (Dodder et al ), their concentrations were still orders of magnitude below where toxicity would be expected to occur (Murdoch et al ; Greenstein et al ).…”

“…A concurrent reduction in toxicity following charcoal addition is also needed to demonstrate that pyrethroids are a likely cause of toxicity. It is common to observe the PBO treatment reducing survival even when there is little or no toxicity in the untreated (baseline) sample (Greenstein et al ). This reduction in survival is an indication of pyrethroids being present and bioavailable but at a low enough concentration that the animals can detoxify them and prevent mortality.…”

“…Sediment TIEs are used as part of the assessment process for total maximum daily loads (TMDLs; Anderson et al ; Perron et al ; Ho et al ; Greenstein et al ) and may be required in regulatory assessments (SWRCB ). During the assessment process for a TMDL, TIEs are often used to determine what chemicals are causing negative effects to the site, so that limits can be set for inputs of these chemicals to the system.…”

How to Improve Exposure Assessment

“…Phase II focuses on structure elucidation or other identification of the toxicant, which according to Burgess et al (2013) is less complicated for cationic metals, but would benefit from more research into robust methods for organic chemicals. Recent publications on TIE include those by Greenstein et al (2014) and Matos et al (2014). Further research has focused on including emerging contaminants in phase II tests.…”

Enantiomer‐specific measurements of current‐use pesticides in aquatic systems

“…Increasingly, researchers are finding conditions in California water and sediment toxic to a variety of organisms such as Hyalella azteca and Ceriodaphnia dubia . To explain the toxicity, a wide array of water quality and chemical measurements have been made, including measurements for current‐use pesticides such as the pyrethroids permethrin, bifenthrin, cypermethrin, cyfluthrin, and the phenylpyrazole fipronil . Some of these measurements allow clear identification of a cause of toxicity, whereas others do not permit a full explanation of the toxic conditions, suggesting that additional information might be helpful.…”