Use of embedded Chelex chelating resin and sediment toxicity bioassays with medaka embryos to determine the bioavailability and toxicity of lead-contaminated sediment

Spatial distribution of benthic toxicity and sediment-bound metals and arsenic in Guangzhou urban waterways: Influence of land use

The effects of land use on pollutant loads in sediments have been well documented; however, its influence on spatial variations in sediment toxicity remains largely unknown. In the present study, the toxicological effects of 17 sediments collected from Guangzhou waterways were evaluated using two benthic invertebrates (Chironomus dilutus and Hyalella azteca), along with quantification of heavy metals and arsenic in the sediments. The impacts of land-use configuration on sediment toxicity and occurrence of heavy metals and arsenic were analyzed. The sediments presented moderate lethality (<40 %) in the two test species and significantly altered their enzymatic activity, including the activities of oxidative stress biomarkers and acetylcholine esterase. Metals (Ag, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) and arsenic were detected in all the sediments, with total concentrations ranging from 238 to 1019 mg/kg of dry weight. Both the toxicity and chemical results displayed spatially dependent patterns but were related to different land use types. Toxicity was most influenced by agricultural and aquacultural activities, while metal and arsenic pollution was most influenced by urban land areas. The present findings are expected to provide essential knowledge for developing strategies that reduce the chemical pollution and ecotoxicological risk in sediments.

Monitoring of ion release, bioavailability and ecotoxicity of thallium in contaminated paddy soils under rice cultivation conditions

Paddy soils contaminated by thallium (Tl) have been frequently reported; however, their ecotoxicological impact in the paddy field is less known. We used a novel soil-fish exposure system with larvae of rice fish medaka (Oryzias latipes) to assess the bioavailability of Tl from soils to fish and causal toxicity under simulated conditions of rice cultivation. Two acidic soils [Pingzhen (Pc) and Sankengtzu (Sk)] spiked with monovalent Tl [Tl(I), 75-250 mg/kg] released higher Tl⁺ into pore or overlying waters than neutral soils [Sangkang (Su)], which resulted in higher mortality to exposed fish. The addition of K fertilizers into the system did not significantly reduce Tl release and fish mortality, but a drainage/re-flooding treatment worked effectively. The acidic Pc soil contaminated with low Tl(I) (2.5 and 15 mg/kg) caused higher sublethal toxicity in medaka than the neutral Su soil, including altered growth and swimming behavior with increased Tl body burden. These Tl-induced effects by low-Tl soils were significantly alleviated by K addition. The Tl/K ratios in aqueous phases were correlated with the mortality or Tl body burden in exposed fish. This study provides useful bio-analytical evidence that can help assess the ecological risks of Tl pollution in paddy field-related ecosystems.

Sublethal toxicity of PbI2 in perovskite solar cells to fish embryos (Danio rerio and Oryzias latipes): Deformity and growth inhibition

Pb-based perovskite in solar cells is a source of PbI₂. The objective of this study was to characterize the embryonic toxicity of PbI₂, a potentially leachable chemical and hazardous material, for two fish species (zebrafish and Japanese medaka). A series of measurements were performed to assess mortality, abnormalities (deformities and other pathological changes), hatchability, and growth inhibition. The results obtained showed that the toxicities observed were predominantly associated with Pb²⁺ and I^-. Therefore, given the potential ecotoxicity of PbI₂, precautions should be taken to prevent its release during the breakage and disposal of Pb-based perovskite solar cells.