Environmental impact of thallium related to the mercury-thallium-gold mineralization in southwest Guizhou Province China

Abstract

Toxic metals associated with metal mineralization and mining are critical targets for environmental studies. Thallium, as a typical toxic metal, has received less attention from a geo-environmental perspective since thallium deposits are relatively rare.This study focuses on natural accumulation of thallium associated with Hg-Tl-(Au) mineralization in the Lanmuchang area in southwest Guizhou Province, China, as a case study for thallium hazard in a geo-environmental perspective. It aims at understanding of the occurrence, the transfer processes and the environmental impacts of thallium related to natural processes and human activity. The distribution and dispersion of thallium together with mercury and arsenic in bedrock, sulfide ore, coals, soil, sediment, ground and surface waters, crops and vegetation have been examined.This study shows that the Lanmuchang area can be characterized as a specific geological context of thallium, mercury and arsenic accumulations. The extensive occurrences of sulfide minerals, such as lorandite, cinnabar, realgar, orpiment and pyrite are the primary carriers of Tl, Hg and As in the rocks and ores. Thallium occurs either as isomorphous substitution in the structure of sulfide minerals of mercury ores, arsenic ores coals, or as a pure thallium mineral lorandite.Tl, Hg and As accumulations are characterized by their high concentrations in rocks/ores, soils, sediments, (sub)surface waters and various crops. The range of thallium concentrations are 33-35000 ppm in sulfide ores, 12-46 ppm in coals, 33-490 ppm in host rocks, 25-1100 ppm in secondary minerals, and 6-330 ppm in outcropped host rocks. Thallium concentrations in soils in the mineralized area range from 53 to 282 ppm, from 21 to 100 ppm in alluvial deposits or foundation soils, from 40 to 46 ppm in slope wash material, and from 2.2 to 29 ppm in undisturbed natural soil. A high concentration has also been observed in sediments, ranging from 10 to 3700 ppm. Thallium concentrations are also high in the deep groundwater of the thallium-mineralized area (13.4-1102 \lg/\), decreasing away from the area to a background level of less than 0.005 |ig/l. In stream water, thallium concentration ranges from 0.3 to 33 jig/1, with marked high contents in downstream sections which likely originated from an unidentified groundwater discharge. In the edible parts of various vegetables and cereals, thallium ranges from 0.21 to 494 ppm (dry weight). The uptake of thallium is more pronounced in vegetables than in cereals, and the highest accumulation occurs in green cabbage.The dispersion of thallium together with mercury and arsenic in the specific ecosystem of Lanmuchang is constrained by the original Tl-Hg-As sulfide mineralization, the specific topography and hydro-geomorphology, and by the disturbance of human activity. High values of thallium are concentrated in the mineralized and mining area; away from this area, thallium concentrations decreases gradually to a background level. Thallium from bedrocks is accumulated in soils, se...

Differences of oribatid mite community and trophic structure between karst caves and surface different moss habitats

“…Higher community diversity index and richness index indicate that there is a longer food chain and more complex food web in the ecosystem, thus enhancing the stability of the community [ 54 , 55 ]. The diversity index of mites in different moss habitats in the study area is generally higher than that of mites in rose mixed agricultural forest, burning agricultural land and rosa roxburghii land in karst area [ 56 – 58 ], indicating that the ecological environment of mites in cave moss habitats is more stable than that of human disturbance. A lot of research shows that the diversity of mite community is related to the composition of vegetation components and the diversity of covering plants, and the quantity and nature of its litter may have a decisive impact on mite community [ 24 , 59 ].…”

Recent Advances in Thallium Removal from Water Environment by Metal Oxide Material

“…Tl adsorption to Fe-Mn adsorbents is fast, efficient, and selective. Equilibrium adsorption can be achieved by over 95% at a wide range of the operating pH values (3)(4)(5)(6)(7)(8)(9)(10)(11)(12) and high ionic strengths (0.1-0.5 mol•L −1 ). This study demonstrates that the mechanism of Tl adsorption is mainly in the complexation of hydroxyl groups and Tl(I) on the Fe-Mn surface, as well as the oxidation of Tl(I) to Tl(III) and the generation of Tl 2 O 3 precipitates on the surface of the material to be adsorbed by the material [60].…”

“…Studies have shown that thallium contamination has posed a serious threat to drinking water safety, and the scope of contamination has spread to countries around the world [7][8][9]. In Canada, New Brunswick, the United Kingdom, Cornwall, Idaho, China, Qianxinan, Guangdong, and Xiangnan, as well as other waters near the mine and downstream water bodies, the monitoring value of drinking water thallium exceeded 10.2-10.4 times.…”