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

Abstract

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) and bioavailability-based extraction was used to identify the causes of sediment toxicity. Of the 6 sediment samples collected, 4 caused 100% mortality to Chironomus dilutus in 10-d bioassays, and the potential toxicants were assessed using TIE 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 2 sediments and that metals and organics jointly caused the mortality in the other 2 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, with cypermethrin, lambda-cyhalothrin, deltamethrin, and fipronils being the toxic organics. To improve the accuracy of identifying the toxicants, 4-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 3 metals (Zn, Ni, and Pb) and 3 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 2 sediments in phase I. Incorporating bioavailability-based measurements into whole-sediment TIE improved the accuracy of identifying the causative toxicants in urban waterways where multiple stressors occurred and contributed to sediment toxicity jointly.

Using Chironomus dilutus to identify toxicants and evaluate the ecotoxicity of sediments in the Haihe River Basin

“…The TIE approach is divided into three phases: characterization into main classes with physical and chemical manipulations (Phase I), identification of the toxicants through analytical techniques and a toxicity evaluation (Phase II), and confirmation of the actual causes of toxicity through collating the corroborating toxicant data (Phase III) 10, 12 . This method has been used successfully for identifying toxicants in both sediment interstitial water and pure sediment 11, 13, 14 . Previous studies have shown that better outcomes are expected from a TIE of aggregated sediment than from observations of intact sediments in situ 10, 15, 16 .…”

“…The TIE procedure has been routinely used for environmental risk assessments in North America, Europe, Australia and Brazil 8, 17–19 , where the level of contamination was relatively low and the toxicity in sediment was mainly identified as arising from a single class of contaminants 13, 20 . In China, however, few studies have applied the TIE approach to identify contaminants in sediments 12, 13, 21 .…”

“…In China, however, few studies have applied the TIE approach to identify contaminants in sediments 12, 13, 21 . The Haihe River Basin is in one of the most industrialized and urbanized regions in China.…”

Does cadmium affect the toxicokinetics of permethrin in Chironomus dilutus at sublethal level? Evidence of enzymatic activity and gene expression

“…Because of their persistence, bioaccumulation and toxicity, these contaminants posed potential risk to aquatic organisms. Yi et al (2015) reported that the sediments from urban waterways in South China were seriously deteriorated by a suite of contaminants and caused high lethality to the benthic invertebrate, Chironomus dilutus. Whole sediment toxicity identification evaluation testing found that the toxicity was caused jointly by current-use insecticides (cypermethrin, lambda-cyhalothrin and fipronil) and metals (Zn, Ni and Pb) (Yi et al, 2015), indicating the need to understand the interaction between these contaminants.…”

Environmental threats to the Three Gorges Reservoir Region: Are mutagenic and genotoxic substances important?

“…Phase II measures target toxicants using different analytical techniques, while Phase III confirms, or otherwise, that the suspect toxicants identified in Phases I and II of the TIE procedures are actually causing the observed toxicity. Indeed, TIE procedures have been employed to identify toxic components in water and sediments in water bodies in China (e.g., Ke et al, 2015;Yi et al, 2015). Over and above this, effect-directed analysis procedures are currently being developed to deal with issues arising from mixtures of pollutants in the management of water resources ( .…”