Research On Chemical Regulation Of Mercury Contaminated Farmland Soil By Humic Acid In Wanshan Area

Wanshan Area is rich in mercury and other natural resources,these resources have made great contributions to the region's economic development and earned foreign exchange of China.However,disordered mining of resources have brought a serious harm to the ecosystem environment and people's life have been impacted.Recently,environmental awareness has been developed and government pays attention to heavy metal pollution of the soil.With the important opportunity to promulgate the Policy for the Action Plan for Prevention and Treatment of Soil Pollution,heavy metals contaminated soil remediation will enter a brand new developing period.In this study,farmland soil of Wanshan was regarded as sample soil,the biomass of Brassica chinensis and the mercury concentration in plant tissues treated with different contents of humic acid added were studied by using pot experiment,effect of the content of humic acid(?_?HA?),moisture regime of soil,application time of humic acid were explored by using signal factor and orthogonal experiments.The conclusions obtained as follows:1.The sample soil was slightly alkaline and the content of mercury of the soil was seriously higher than the secondary standard of Environmental Quality Standard for Soils?GB15618-1995?.A majority of mercury of sample soil dominated by Residual and Bound to Organic Matter and only a tiny minority of mercury existed as Exchangeable and Bound to Carbonates.2.In the pot experiment,humic acid could increase the biomass of Brassica chinensis and reduce mercury concentration of the plants at some level.As ?_?HA?= 1.6%,the biomass of Brassica chinensis was the highest,the biomass of the plants,the biomass of leaves and stems and the biomass of roots were positively correlated to ?_?HA?.Humic acid could change the biomass of Brassica chinensis through changing the biomass of roots,leaves and stems.The mercury concentration in plants,plant roots,plant leaves and stems decreased at the beginning and then increased while ?_?HA?increased,the mercury concentration of the plants,roots,BF were positively correlated to ?_?HA?,mercury concentration in leaves and stems were highly corrected to mercury concentration in plants,mercury concentration in roots was correlated significantly with mercury concentration in plants.3.The change of ?_?HA?,moisture regime of soil,application time of humic acid could change soil pH,Eh,population quantity of edaphon.In the single factor experiment,distributions of mercury speciation in soils were optimal when ?_?HA?was 1.2%,moisture regime of soil was 85% WHC,application time of humic acid was 31 d.4.In the orthogonal experiment,Stab-Hg and Bio-Hg were chosen as test index,the above three factors ranked with their importance as follows: ?_?HA?>application time of humic acid>moisture regime of soil.When ?_?HA?was 1.2%,moisture regime of soil was 85% WHC,application time of humic acid was 41 d,the content of Stab-Hg was biggest and the content of Bio-Hg was smallest.