Bioavailability assessment of a contaminated field sediment from Patrick Bayou, Texas, USA: Toxicity identification evaluation and equilibrium partitioning

Abstract

Contaminated sediments are commonly found in urbanized harbors. At sufficiently high contaminant levels, sediments can cause toxicity to aquatic organisms and impair benthic communities. As a result, remediation is necessary and diagnosing the cause of sediment toxicity becomes imperative. In the present study, six sediments from a highly industrialized area in Patrick Bayou (TX, USA) were subjected to initial toxicity testing with the mysid, Americamysis bahia, and the amphipod, Ampelisca abdita. All sediments were toxic to the amphipods, while sites PB4A, PB6A, and PB9 were the only sites toxic to mysids. Due to its toxicity to both test organisms, site PB6A was chosen for a marine whole sediment phase I toxicity identification evaluation (TIE). Results of the TIE found toxicity to amphipods was primarily due to nonionic organic contaminants (NOCs), rather than cationic metals or ammonia. Causes of mysid toxicity in the TIE were less clear. An assessment of metal bioavailability using equilibrium partitioning (EqP) approaches supported the results of the TIE that cationic metals were not responsible for observed toxicity in PB6A for either organism. Toxic units (TU) calculated on measured concentrations of NOCs in the sediment yielded a total TU of 1.25, indicating these contaminants are contributing to the observed sediment toxicity. Using a combination of these TIE and EqP assessment tools, this investigation was capable of identifying NOCs as the likely class of contaminants causing acute toxicity to amphipods exposed to Patrick Bayou sediment. The cause of mysid toxicity was not definitively determined, but unmeasured NOCs are suspected.

What's causing toxicity in sediments? Results of 20 years of toxicity identification and evaluations

“…Currently, much of the discussion of TIE methodology development is on the topic of identifying specific organic toxicants. With complex natural mixtures, it is often difficult to discern specific, individual toxicants, particularly in the large class of nonionic organic chemicals . Methods to identify specific pesticides such as pyrethroids or organophosphates have been successfully employed ; however, developing methods to identify other emerging contaminants—including toxic ionic organic chemicals such as many of the pharmaceuticals, personal care products, and degradation products of pesticides and herbicides—as well as the milieu of legacy organic compounds still remains a challenge.…”

“…Sediment TIEs have been successfully performed in many countries around the world over the last 20 yr . The present study builds on a 2002 article that analyzed the available set of data at the time ( n = 18).…”

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

“…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.…”

Identifying the causes of sediment-associated toxicity in urban waterways in South China: Incorporating bioavailabillity-based measurements into whole-sediment toxicity identification evaluation

“…The bioavailability of sediment‐bound contaminants should be considered when applying whole‐sediment TIE . Ignoring the difference in bioavailability when manipulating sediment in phase I of TIE (characterization) may exaggerate the toxicity of polar chemicals .…”