John Wiley & Sons, Ltd.

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

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Courtesy of John Wiley & Sons, Ltd.

Sediments in urban waterways of Guangzhou, China were contaminated by a variety of chemicals and showed prevalent toxicity to benthic organisms. A combination of whole‐sediment toxicity identification evaluation (TIE) procedure and bioavailability‐based extraction approaches were used to identify the causes of sediment toxicity. Four of the six sediment samples collected caused 100% mortality to Chironomus dilutus in 10‐d bioassays and the potential toxicants were assessed using TIE testing in these sediments after dilution. The results of phase I characterization showed that organic contaminants were the principal contributors to the mortality of the midges in two sediments, and metals and organics jointly caused the mortality in the other two sediments. Ammonia played no role in the mortality for any samples. Conventional toxic unit analysis in phase II testing identified Cr, Cu, Ni, Pb and Zn as the toxic metals while cypermethrin, lambda‐cyhalothrin, deltamethrin and fipronils being the toxic organics. To improve the accuracy of identifying the toxicants, four‐step sequential extraction and Tenax extraction were conducted to analyze the bioavailability of the metals and organics, respectively. Bioavailable toxic unit analysis narrowed the list of toxic contributors and the putative toxicants included three metals (Zn, Ni and Pb) and three pesticides (cypermethrin, lambda‐cyhalothrin and fipronils). Metals contributed to the mortality in all sediments, but sediment dilution reduced the toxicity and confounded the characterization of toxicity contribution from metals in two sediments in phase I. Incorporating bioavailability‐based measurements into whole‐sediment TIE testing improved the accuracy of identifying the causative toxicants in urban waterways where multiple stressors occurred and contributed to sediment toxicity jointly. This article is protected by copyright. All rights reserved

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