LEI Liang-qi，MO Bin-ji, FU Wei, MO Jia，SHI Zhen-huan, CHENG Si-nai
(Earth Science Faculty, Guilin University of Technology, Guangxi Guilin 541004, China)

 

Abstract: To probe into the mechanism of heavy metals release from carbonate-rich sulfide tailings (CRSTs) subjected to the oxidation/acidification, the study focused on the Bali CRSTs, piled more than 20 years, in Dachang cassiterite-polymetallic sulfide mine (Guangxi, China). By investigating the distribution of the chemical speciation (BCR three-step sequential extraction procedure) and total contents of heavy metals (Zn, Cd, Pb, As) on a plumb profile in Bali tailings impoundment, discussing it on the basis of the tailings structure, secondary and primary mineral composition and its change, this paper indicated that: (1) Heavy metals in the original tailings of lower profile occurred mainly as stable or relatively stable forms, i.e. residual fraction (As, Pb, Zn, Cd), Fe-Mn oxide bound fraction (Pb) and sulfide bound fraction (Zn, Cd). The mobility of metals in the original tailings leached by acid water followed the order Cd≈Zn＞Pb＞As. (2) In the hard layer (hardpan, 1~1.5 m thick) of upper profile, Zn and Cd occurred mainly as acid soluble speciation, which are of stronger mobility, while As and Pb occurred mainly as residual fraction and Fe-Mn oxide bound fraction, which are of weaker mobility. Therefore, the CRSTs subjected to oxidation possess the potential to release multiple heavy metals. Because the heavy metals in the CRSTs were not identical in occurrence state, their mobility and environmental effect should be considered discriminatively.

 

Key words: carbonate rich tailings; tailings fabric; heavy metals chemical speciation; mine environment; Dachang tin mine.

 

EARTH AND ENVIRONMENT Vol. 42, No.5, Tot No.301, 2014, Page 604-610