Mercury is a non-essential and toxic element to human due to its volatility, mobility, bio accumulative and neurotoxicity. Since last century, a series of events have happened as a result of Hg poisoning all over the world. The Minamata disease, which happed in Japan in 1956, was caused by eating methylmercury-contaminated seafood. It is estimated that more than 1000 people died and 10000 people were adversely affected in this event. Due to its serious adverse impact, Minamata tragedy is labeled as one of the world's top ten environmental disasters in the 20th century.

Guizhou Province locates at the SW of China and has several large-scale and super large-scale mercury deposits such as Wanshan, Wuchuan, Danzhai and Tongren mercury deposits. The soils are heavily contaminated mercury due to the long period of mining activities, and the mercury concentrations in the crops greatly exceed the environmental standard set by the Chinese EPA.

Professor FENG Xinbin and his research group from the State Key of Laboratory of Environment Geochemistry (SKLEG) at Institute of Geochemistry, Chinese Academy of Sciences (IGCAS) tried to remediate mercury contaminated soil at Wanshan. They reviewed the techniques and case studies that related to remediation of mercury contaminated sites. Based on the current economic development level in Guizhou, the researchers proposed the use of phytoremediation to remediate mercury contaminated soils at mercury mine in Guizhou. Their results from greenhouse and field experiments indicated that the thiosulphate assisted phytoextraction could effectively enhance the phytoremediation efficiency of mercury contaminated soils and significantly decrease the concentration of mercury associated with Fe/Mn oxides and organic matter in soils. Moreover, the majority of mercury uptaken from soil mainly present as in a form similar with meta-cinnabar in plant tissues.

These results have been published in Journal of Hazardous Materials（2012, Volumes 221–222, pp 1–18）and Environmental Science & Technology (2012, Volume 46, pp 5361–5368) respectively, and the papers were entitled ‘Remediation of Mercury Contaminated Sites-A Review’ and ‘Implication of Mercury Speciation in Thiosulfate Treated Plants’, respectively.

(BY WANG Jianxu)