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The adverse impacts of detrimental thallium (Tl) contamination are of increasing concerns to sustainable development. Herein, the contents, distributions and sources of Tl and potential toxic elements (PTEs) (Pb, As, Cr, Cu, Ni, Co, Sb, Cd and U) were investigated in sediments collected in Gaofeng River, which has been contaminated by long-term mining activities, located in Yunfu City, Southern China. Results indicated that excessive Tl levels were found in sediments (1.80-16.70 mg/kg). Sequential extraction procedure indicated that despite a large amount of Tl entrapped in residual fraction, a significant level of Tl (0.28-2.34 mg/kg) still exhibited in geochemically labile fractions, which was easy for Tl mobilization and availability. Pb isotope tracing method further confirmed that the pyrite exploitations may be the prime contaminated contributor (47-76%) to these sediments. These findings highlight that it is essential to establish more effective measures for Tl contamination control and call for engineered remediation countermeasures towards polluted river sediments., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Thallium (Tl) is a trace metal of severe toxicity. Its health concerns via consumption of contaminated vegetables have often been overlooked or underestimated. This study was designed to gain insight into the actual level and distribution characteristics of Tl and metal (loid)s (Pb, Cd, Cr, Sb, Mn, Cu, Zn, Ni, and Co) in agricultural soils and common vegetables cultivated in different zones (upstream, midstream, and downstream) of a densely populated residential area in a typical mine city, which has been open-pit exploiting Tl-bearing pyrite minerals since 1960s. The results show that most of the agricultural soils exhibit contaminated levels of Tl, with Tl contents (upstream: 1.35-4.31 mg/kg, midstream: 2.43-5.19 mg/kg, and downstream: 0.65-2.33 mg/kg) mostly exceeding the maximum permissible level (MPL) for agricultural land use (1 mg/kg). Sequential extraction procedure indicates that even Tl is predominantly retained in the residual fraction, significant levels of Tl are still present in the geochemically mobile fractions. Besides, metals like Cu, Cd, Mn, and Co are mostly distributed in the labile fractions. Almost all metal (loid)s in edible parts of the vegetables exceed their corresponding MPL for consumption. The chronic daily intake (CDI) and hazard quotient (HQ) values calculated for inhabitants at different ages indicate non-negligible Tl risks via consumption of local vegetables, especially for children. Therefore, it is critical to establish effective measures for hazardous waste management and enforceable regulations in Tl-polluted area to mitigate potential severe impacts of Tl on human health through food chain., (Copyright © 2019 Elsevier Ltd. All rights reserved.)