title: The geochemical release feature of Tl in Tl-rich pyrite mine wastes: a long-term leaching test.
abstract: Identifying and revealing the geochemical behaviour of Tl during mine waste weathering are very important to assess the potential environmental impact of Thallium (Tl) from open mine-waste piles. Herein, two methods including the modified BCR sequential extraction and the long-term humidity cell tests (HCT) were employed to understand the Tl chemical fractions and to stimulate intense chemical weathering process, respectively. The results from BCR sequential extraction showed that the Tl concentration in the studied sample was 18.78 mg/kg, containing 1.878 mg/kg oxidisable, 0.282 mg/kg acid exchangeable and 1.596 mg/kg reducible Tl. The acid exchangeable fraction contributed to a particular potential risk to the aquatic marine life in the early stages and the Fe/Mn oxidisable fraction posed a potential risk being dissolved into solution at low pH (i.e. acidic conditions). The variations of Tl concentration in leachates were classified as two period as the pH values decrease. In the first period, the Tl concentrations decreased positively with pH value with poor correlation between pH value and SO42-concentration in leachates. Drastic release of Tl was observed in the early period once the material was exposed to air and water, being ascribe to the acid exchangeable fraction bound to carbonate as dissolved by acid. During the second period, three increased peaks of Tl concentration (11.02, 16.03, 43.15 μg/L) and four increased peaks of SO42-concentration (315, 390, 899.61 and 2670 mg/L) were observed. A good correlation (R2= 0.8384) between the concentrations of Tl and SO42-was observed, indicating the Tl was mainly released from the oxidation of sulphide.
authors.affiliation: School of Environmental Science and Engineering, Guangzhou University, Guangzhou, 510006, China.|Global ARD Testing Services Inc., Burnaby, Canada.
authors.forename: Jinwen
authors.initials: J
authors.lastname: Li
authors.affiliation: School of Environmental Science and Engineering, Guangzhou University, Guangzhou, 510006, China.|Provincial Radioactive Pollution Control and Resource Reuse, Key Laboratory Guangzhou University, Guangzhou, 510006, China.
authors.forename: Nan
authors.initials: N
authors.lastname: Chen
authors.affiliation: Global ARD Testing Services Inc., Burnaby, Canada.
authors.forename: Ivy
authors.initials: I
authors.lastname: Rajan
authors.affiliation: School of Environmental Science and Engineering, Guangzhou University, Guangzhou, 510006, China.
authors.forename: Zhehua
authors.initials: Z
authors.lastname: Sun
authors.affiliation: Provincial Radioactive Pollution Control and Resource Reuse, Key Laboratory Guangzhou University, Guangzhou, 510006, China.
authors.forename: Huiming
authors.initials: H
authors.lastname: Wu
authors.affiliation: School of Environmental Science and Engineering, Guangzhou University, Guangzhou, 510006, China. cdy@gzhu.edu.cn.|Provincial Radioactive Pollution Control and Resource Reuse, Key Laboratory Guangzhou University, Guangzhou, 510006, China. cdy@gzhu.edu.cn.
authors.forename: Diyun
authors.initials: D
authors.lastname: Chen
authors.affiliation: School of Environmental Science and Engineering, Guangzhou University, Guangzhou, 510006, China.|Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou, 510275, People's Republic of China.
authors.forename: Lingjun
authors.initials: L
authors.lastname: Kong
mesh_terms: D004784:Environmental Monitoring; D007501:Iron; D008906:Mining; D013440:Sulfides; D013793:Thallium
chemical_list: D013440:Sulfides; C011342:pyrite; D013793:Thallium; D007501:Iron
keywords: Humidity cell; Pollution; Sequential extraction; Thallium; Waste mine