Abstract
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 FeS2 and SiO2 were the major minerals. The high-resolution transmission electron microscope and element mapping characterization further confirmed that FeS2 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.
Highlights
The environmental risks over utilization of minerals containing highly toxic metals have been receiving increased attention
The geochemical fractionation of Cd, Cr, Cu, Ni and Pb in sediments of the Hooghly (Ganges) River Estuary, eastern part of India was studied by Mondal et al (2020), and the results indicated that Cd primarily existed in the acid extractable fraction while Pb was dominant in the reducible fraction
The acid extractable fraction of the studied heavy metals in the pyrite ores refers to the part that is adsorbed onto the mineral microstructure layers, or bonded with carbonates, which tends to release into the environment media upon the decomposition of carbonate and/or the disappearance of Van der Waals force between the mineral structure layers (Zhang et al, 2007a, 2007b)
Summary
The environmental risks over utilization of minerals containing highly toxic metals have been receiving increased attention. Excessive intake of Pb can lead to destruction of biological activity (Zhou et al, 2020), while high Cd poisoning can induce kidney disease, bone damage, and hematuria (Sasmaz et al, 2019). These elements can migrate and tend to be accumulated in the environment, which could be subjected to further geochemical dispersal, transport, and transformation, posing a significant threat to both environmental quality and human health. Tessier et al (1979) proposed the first methodology named “sequential extraction” for analyzing the chemical phase distribution of heavy metals in soils and sediments. Kersten and Forstner (1986) further improved the analytical methods for identifying the chemical fraction of heavy metals in coastal sediments.
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