No mercury hyperaccumulators have been identified to date. Many studies have proven that the ammonium thiosulfate can enhance the mercury accumulation in plant through which they can meet the standard of accumulators or even hyperaccumulators. However, the mechanism of mercury transport and accumulation in plant as a result of ammonium thiosulfate has not been identified yet. Researchers from Institute of Geochemistry, CAS have studied the mercury speciation in thiosulfate treated plant by using XANES approach and explored the possible mechanism of mercury accumulation induced by thiosulfate. Their results have been published on Feb, 2012 in Environmental Science & Technology.

The research group found very interesting results that nearly 80% of mercury in thiosulfate treated plant was in a form similar with black cinnabar. Moreover, mercury concentration was positively correlated with sulfur concentration in plant tissues. These evidences indicate that the mercury may combine with sulfur and transport in plant tissues. This mercury-sulfur complex will decompose to HgS. The scientists are pleased with this result, because plant can emit mercury to the air and cause secondly contamination. Mercury presented as cinnabar may inhibit the emission of mercury to the air.

The results from this study not only provide the evidences for exploring the mechanism of mercury accumulation induced by thiosulfate, but also provide the theoreial base for exploring thiosulfate assisted phytoextraction technology. In this study, the synchrotron sources provide the effective tool to make us to be able to analysis mercury speciation in plant tissues.

“By using XANES, we understand the speciation of mercury in plants, this was very import for exploring the mechanism of mercury accumulation in plants, however, the migration pathway of mercury in plant should be further explored, the XRF can help us to solved this scientific question” says Xinbin Feng, the team leader and the professor of Institute of Geochemistry, Chinese academy of sciences.

Normalized Hg HgLⅢ XAS spectra of plant samples and standard

Article:

Wang JX, Feng XB, Anderson CWN, Wang H, Zheng LR, Hu TD. Implications of Mercury Speciation in Thiosulphate Treated Plants. Environmental Science & Technology, 46, 5361−5368, 2012.