The pyrite ores are strategic industrial resources which generally serve as raw material for producing sulfuric acid. However, during the mining and industrial processing activities, associated toxic elements of cadmium (Cd) and lead (Pb) could be released into the surroundings, posing a significant threat to local environment and human health. In this study, the Institute for Reference Materials and Measurement (IRMM) sequential extraction scheme was used to investigate the geochemical fractionation of Cd and Pb in pyrite ores from a mining area located in Yunfu, western Guangdong, China. The results showed that most of Cd and Pb (>90%) were predominantly found in the geochemically mobile fractions, indicating that Cd and Pb were readily bioaccessible thus easily assimilated and accumulated by organisms. FESEM-EDS results showed that the studied pyrite ores were mainly composed of O, S, and Fe, while the XRD characterizations suggested that FeS 2 and SiO 2 were the major minerals. The high-resolution transmission electron microscope and element mapping characterization further confirmed that FeS 2 was the main mineral of pyrite ores which contained relatively enriched toxic heavy metals (e.g., Pb and Cd). The findings highlight that an extremely large amount of geochemically mobile heavy metals can be released into the environmental media during the mining and utilization processes of pyrite ores based on IRMM sequential extraction protocol. Therefore, proper countermeasures against environmental risks of utilizing pyrite ores should be taken to mitigate the impacts on local ecosystem and human health.

Thallium (Tl) is a highly toxic trace metal widely distributed in water environments, which may threaten the water quality and aquatic organisms at excessive levels due to increased anthropogenic activities. This study investigated the changes in microbial communities of intestines and organs of zebrafish. The toxic response assessments include intestinal microbiota composition and the histopathology of zebrafish’s gill and liver tissues under exposure of Tl at environmental-relevant levels. The results support that the intestinal microbial community of zebrafish greatly changed under a relatively high Tl concentration (1000 ng/L). A significant increase of pathogenic intestinal bacteria such as Mycobaterium in the intestine of zebrafish exposed at Tl levels over 500 ng/L was found. Additionally, the gill and liver tissues displayed different degrees of damage under Tl exposure, which possibly leads to mating behavior changes and death of zebrafish. The results indicate that low doses of Tl in the aquatic environment induce high toxicity on zebrafish and may pose pathological threats to the gill and liver of zebrafish. In addition, Tl exposure gives rise to increasing abundance of pathogenic intestinal bacteria and changes the community structure of intestinal microorganisms.