Smarter Sediment Screening: Effect-Based Quality Assessment, Chemical Profiling, and Risk Identification

Abstract

Sediments play an essential role in the functioning of aquatic ecosystems but simultaneously retain harmful compounds. However, sediment quality assessment methods that consider the risks caused by the combined action of all sediment-associated contaminants to benthic biota are still underrepresented in water quality assessment strategies. Significant advancements have been made in the application of effect-based methods, but methodological improvements can still advance sediment risk assessment. The present study aimed to explore such improvements by integrating effect-monitoring and chemical profiling of sediment contamination. To this end, 28 day life cycle bioassays with Chironomus riparius using intact whole sediment cores from contaminated sites were performed in tandem with explorative chemical profiling of bioavailable concentrations of groups of legacy and emerging sediment contaminants to investigate ecotoxicological risks to benthic biota. All contaminated sediments caused effects on the resilient midge C. riparius, stressing that sediment contamination is ubiquitous and potentially harmful to aquatic ecosystems. However, bioassay responses were not in line with any of the calculated toxicity indices, suggesting that toxicity was caused by unmeasured compounds. Hence, this study underlines the relevance of effect-based sediment quality assessment and provides smarter ways to do so.

Mixture Risk Drivers in Freshwater Sediments and Their Bioavailability Determined Using Passive Equilibrium Sampling

“…Application of batteries of in vitro assays allows one to identify which modes of action are affected and how large the mixture effects are, but it is not possible to identify which chemical cause the specific effects. An integrated approach combing chemicals and effect screening indicative of diverse compounds and toxicological endpoints has been shown powerful for monitoring sediment quality and may aid to identify mixture risk drivers. − …”

Contaminated aquatic sediments

“…de Baat et al (2019) performed sediment screening process to support effect‐based quality assessment by using three well‐known toxicity indices, for example, exposure‐activity ratio (EAR), multi‐substance potentially affected fraction (msPAF), and toxic unit (TU); chemical profiling of sediment contaminated by PAHs, emerging contaminants, pesticides, herbicides, metals from four sources such as reference (R), wastewater treatment plant (WWTP), agriculture (A), and urban (U); and risk identification of benthic biota such as Chironomus riparius and Daphnia magna as representative, when survival rate of targeted organism in sediment polluted by different sources such as WWTP, A, and U was 47.5%–52.2%, 34%–76%, and 70%–86%, respectively, and the emergence rate was 48%–53%, 30%–72%, and 46%–64%, respectively. Moreover, the emergence time for R, WWTP, A, and U was 16.4–19.1 days, 16–18 days, 16.7–22.0 days, and 20.0–24.2 days, respectively, while the highest EAR, msPAF, and TU values were found in WWTP, U, and U, respectively; however, the lowest EAR, msPAF, and TU values were found in U, A, and R, respectively; and bioassay‐based toxicity was highest at WWTP and lowest at R. Metals and PAHs were mostly available in U, WWTP markets at WWTP and pesticides in A although pesticides and emerging contaminants were mainly responsible for toxicity as the targeted organism, that is, C. riparius had showed lethal or sub‐lethal effects but D. magna did not effect by toxicity.…”

Contaminated aquatic sediments

“…Using Chironomus riparius in a 28‐day bioassay, De Baat et al (2019) sought to integrate chemical contamination profiling and effects monitoring to study risks to benthic organisms. They found that bioassay responses did not correspond with calculated toxicity indices and surmised that unmeasured compounds caused the observed toxicity.…”