The Survey And Scheme Research Of Arsenic Pollution Control In The Nanhua Arsenic Mining In Yunnan

Arsenic is a familiar environmental toxicant that affects our health,and it is affirmed that arsenic can induce cancer on human being.Yunnan Province is an important non-ferrous metal base.There is a long history of smelting in Yunnan Province.Meanwhile,it is also one of the fourteen significant arsenic pollution prevention and controlling provinces.Based on the characteristics of arsenic pollution are long-term,cumulative,latency and irreversibility and the resource distribution,industrial structure of Yunnan Province,the arsenic pollution prevention and controlling situation in Yunnan Province are very serious.In a arsenic mine located in Nanhua county,Yunnan province,arsenic ore had been exploited in order to produce white arsenic since 1953.Due to poor production technology and lack of effective environmental protection measures,the soil and surface water near the plant was polluted seriously in the production process of white arsenic.Even after several ordered rectification,the pollutants discharged from the factory still exceeded the critical values in Chinese legislation by many times.As a result,the plant was shut down in 2000.Unfortunately,a lot of arsenic residues which had not been disposed effectively and still left around the mining area.Monitoring results show that the water and soil near the the project area have been polluted in different degrees and the environment quality has decreased seriously.In order to prevent the scope of arsenic contamination further expansion,protect the ecological environment and the people's lives and property safety life of the Red River basin-wide and downstream areas,it is imperative to control the environment pollution in this region.In this paper,the number and the forms of arsenic residue were analyzed and the arsenic pollution control techniques and enviromental management also were proposed.The results were showed as follow:(1)The arsenic residues mainly were stacked in five dump sites.The total volume of arsenic residues and arsenic contaminated soil in all dump sites reaches 252,000 m3.The clearing area of arsenic residues and arsenic contaminated soil is about 36626.69 m2 and the total quantity is around 417,000 tons.Studies indicate a relatively high leachability of As in arsenic residues,which exceeded the critical values in Chinese legislation by many times.The arsenic residue in project area is consisted mainly of residual form.In addition,the proportion of acid-soluble arsenic residue is still high;(2)It is indicated by the monitoring result of surface water that the water which has not been polluted is favorable.Because there are no other pollution source,the concentration of arsenic in Longtan and Xincun River of uncontaminated section is relatively low.Due to arsenic contamination,the water quality of Longtan and Xincun River near downstream the factory has become poor and almost lost its level of functionality defined in Chinese legislation;According to the investigation of gushing water of two mines left over in the mining area,the concentration of arsenic is high.The highest concentration of arsenic in the No.1 mine gushing water reaches 22.3 mg/L,which exceeds critical values in legislation by 445 times.The highest concentration of arsenic in the No.2 mine gushing water reaches 22.9 mg/L,which exceeds the critical values by 457 times;(3)Based on the results of surveys and studies,the solidification approach was used to treat and dispose the area arsenic waste.In the experiments,portland cement and lime are used for curing agent.The experiment results of solidification showed the former is more suitable for solidification/stabilization(S/S)of arsenic waste residue from the former industrial site than the latter;The experiment result of arsenic residue stabilizing show ferrous sulfate is more suitable as stabilizing agent.The optimum stabilization reaction conditions for arsenic residue were Fe:As = 2,pH 8,water cement ratio 0.4,cement;arsenic residue=40:60,mixing time of 15 minutes and reaction time of 60 minutes;(4)The activated carbon was modified with FeCl3,and the optimization modified reaction conditions for the reaction were temperature 55?,FeCl3 impregnation concentration of 1 mg/ml,modification reaction time of 7 h;The modified activated carbon was used to treat wastewater containing arsenic.The experimental results show that the equilibrium time,pH,initial concentration of arsenic in solution and solid-liquid ratio are the critical factors affecting the results.(5)In addition,the mechanism of the chemical reactions and material transformation in the treatment process of arsenic water and arsenic residue were explored.(6)To make the project more feasible,environmental management measures were proposed from the five aspects of legal,institutional,technical,administrative and economic.By adopting the above measures,the arsenic waste residue will be disposed properly and the arsenic water will be effectively purified in the Nanhua County arsenic pollution area.Aa a result,the soil and water pollution trends near and downstream of the project area will be controlled At the same time,the environmental risks will be also significantly reduced.