The Selection Of Hg-Tolerance Plants And The Study Of The Tolerance Mechanisms In The WanShan Mine

Hg is one kind of heavy metal which can cause environmental pollution, componenl electron transport enzymes. Mining and smelting of Hg mine are the main reasourses that result in environmental pollution. Numerous castoff and waste water that comefrom mining have different degree pollution to the plants and soil around the Hg mine. Hg also induces toxicity to plant when the tissue concentration is slightly above its optimal levels.. Eventually, they may pose a potential health risk to residents in the vicinity of mining areas. So the Hg contamination of soils and plants by metalliferous mining activities in Wanshan Hg mine, located in eastern Guiyang city, Guizhou province was surveyed. The result shows that elevated Hg concentrations of soils and crops were found in the study area. Soil samples contained Hg concentration exceed the second class of environment quality standards for world soils.Hg tolerant plants were surveyed in several Hg mines of Wanshan, and a series of pot experiments of Euphorbia esula L.and Pteris vittata L. in greenhouse were performed to evaluate their possibilities in repairing Hg contaminated soils. The survey results showed that no plant was yet found in this area to strictly meet the definition of Hg hyperaccumulator. Pteris vittata L. is very tolerant to Hg toxicity in a culturing solution with Hg concentration up to 50μmol/L, and can take up high Hg contents in shoot.Hydroponic cultures were conducted to investigate the Hg tolerance and toxicity mechanisms on the growth of Pteris vittata L., which as a Hg tolerant plant was sampled from Wanshan Hg mine. The experimental result shows Pteris vittata L. has higher Hg concentration in the roots, but lower in its shoots. And Hg concentration in shoots and roots increases with the increasing Hg concentration in solution and lengthening treatment time. The uptake of Mg in Pteris vittata L. isn't influenced by different Hg concentration in solution. The presence of Hg can decrease the production of Chl contents, SOD activity in short times, which can increase the endurances of Pteris vittata L. to Hg. But with lengthening treatment time this effect will decrease gradually. P. vittata L. has a strong tolerant capability to high Hg concentration in the medium.There was no significant difference in biomass between adding Hg and CK treatments. But the dry matter production decreased markedly with increasing Ca concentration.The effects of Hg and Ca concentration in culture solution on Hg content in P. vittata L. were much gnificant. Hg uptake by each part of P. vittata L. increased obviously with elevating Hg level and the ratio of pinna Hg concetration to root Hg concentration increased gradually. Hg concentration in root was not affected markedly by Ca levels, while that ofpetiole increased and that of pinna decreased significantly. Adding Hg was benefit to take up Ca by P. vittata L., in the roots and pinnac. Ca concentration in the plant strongly increased followed by enhancing Ca level in solution compared to 0.03 mmoI/L Ca treatment. But the obvious difference about Ca content in P. vittata L. between middle and high Ca level treatments was not found except that in the petiole. Applying Hg maybe reduced Mg concentration in P. vittata L., but that in the frond was not affected sigficantly.