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Selenium (Se) is an essential microelement for human or animal health. At high concentrations, it can cause Se poisoning. Human activities (such as coal burning and mining) threaten soil biota by mobilizing high levels of Se. We used the earthworm Eisenia fetida as a bio-indicator of environmental pollutants to investigate Se acute toxicity, enrichment, and distribution through exposure tests using filter paper, artificial soil and cow manure. The 24 h- and 48 h-LC 50 for the filter paper contact test were 2.7 and 1.52 μg/cm2. In artificial soil test, the 14 d-LC 50 and 14 d-biomass inhibition concentration (IC 20) were 63.86 and 59.81 mg/kg, respectively. The cow manure resulted in a 2.2- and 2.6-fold higher LC 50 and IC 20 than artificial soil results, respectively. Earthworms accumulated the largest Se load (89.47 mg/kg) in artificial soil containing 80 mg Se/kg and only accumulated 90.3 mg/kg in cow manure containing 160 mg Se/kg; 46.6–60.59% of the total Se was distributed in the tail of E. fetida. The Se enrichment rate (SER Se) and bioaccumulation factor (BAF Se) scored higher in artificial soil than in cow manure with the same Se concentration exposure, and the highest SER Se was 6.21 and 6.31 mg Se/kg earthworm/d, respectively. The highest BAF Se was 1.49 in artificial soil and 0.75 in cow manure. Our results demonstrate that selenite is more toxic to earthworms living in artificial soil than in cow manure. E. fetida possesses certain Se detoxification mechanisms by distributing Se in the tail. [Display omitted] • 48 h LC 50 of selenite toxicity to earthworm was 1.52 μg/cm2 in the filter paper test. • Earthworms exposed to artificial soil had lower LC 50 and IC 20 than in cow manure. • Earthworms suffered greater Se burden in artificial soil compared to cow manure. • Earthworm mainly distributed Se in the tail to alleviate Se toxicity. • Selenite was more toxic to earthworms in artificial soil than that in cow manure. [ABSTRACT FROM AUTHOR]

Aquatic contamination can settle into sediments, where it complexes with organic matter and becomes bioavailable. The resulting bioaccumulation of these contaminants by benthic fauna poses a serious threat due to the potential for trophic transfer. This paper offers an insight into the heterogenous accumulation behavior of different elements, and the consequences for ecological risk. In this study, we present field quantification of sediment-associated bioaccumulation factors (BAF S) in freshwater benthic macroinvertebrates. 17 elements were quantified using ICP-MS in sediment and Asellus aquaticus and Gammarus sp. samples. Previously published reports of contaminant concentrations in freshwater and marine sediments and benthic fauna were likewise analyzed to provide a complementary picture of bioaccumulation across contaminants and taxa. We demonstrate that the BAF S correlates strongly with the thiophilicity of the elemental contaminants, as defined by (Kepp, 2016), for all strata examined. These findings support the hypothesis that thiol-mediated processes, such as that of metallothionein, play a larger role in bioaccumulation than typically afforded. In conclusion, we demonstrate the potential for the thiophilic scale to act as a predictor of accumulation potential. [Display omitted] • Accumulation correlates strongly with thiophilicity across orders and environments. • Results support a thiol-based bioaccumulation process. • Bioavailability of contaminants can be predicted using the thiophilic scale. [ABSTRACT FROM AUTHOR]