Characteristics Of Heavy Metal Pollution And Environmental Effects From Manganese Residues In Typical Manganese Mining Area In Guizhou

As an important metallurgical and chemical raw material,manganese has made great contributions to the rapid development of China's industry.However,at the same time,the mining and smelting of manganese ore produced abandoned waste residue that have caused varying degrees of pollution hazards to the surrounding environment.This study selected typical manganese mining areas?Zhailanggou,Yanglizhang,Xixibao,Baiyanxi,Pengjiashan,Pengcheng,Hongyandong,Xiangjiang,and Nancha?of Guizhou Tongren and Zunyi As main research areas.Samples of tailing,mine water and mining soil,surface water,sediment,vegetable,electrolytic manganese slag in the study area were collected,The composition and content of heavy metals in each sample were analyzed;the heavy metal of surface water was evaluated using the single factor pollution index and the Nemerow comprehensive pollution index method,the degree of pollution and potential ecological risks of sediments and soils were evaluated using the methods of geoaccumulation index and potential ecological index,the health risk of vegetables wered evaluated applying the carcinogen risk and non-carcinogen risk assessments;and further studied the characteristics of manganese morphology,leaching toxicity,seed toxicity of manganese,and the toxic effects of vegetables.The main conclusions are as follows:?1?The average contents of heavy metal elements As,Hg,Cd,Cr,Pb,Zn,Cu,Ni and Mn in tailings slag in the study area exceed the soil background values in Guizhou Province,and the oversizing multiples are 1.24,2.73,4.25,1.06,1.31,1.39,39.0 times respectively.The Mn in the tailings slag is mainly exists in the organic bound state,followed by the residue state.?2?The average contents of As,Hg,Cd,Cr,Pb,Zn,Cu,Ni and Mn in the electrolytic manganese residues of the 12 typical electrolytic manganese enterprises in Guizhou exceed the soil background values in Guizhou Province with the exceeding multiples of 1.69,9.10,2.0,2.57,1.07,1.58,33.0 times respectively.The Mn in electrolytic manganese slag in Tongren area is mainly exist in the exchangeable state,followed by the organic bonded state;in the electrolytic manganese slag in Zunyi area,Mn is mainly exist in the organic bound state,followed by the exchangeable state.?3?The average content of heavy metal element Mn in surface water in the study area exceeds the standard limit(100?g?L^-1)of 39.67 times that of the supplemental item for centralized drinking water surface water sources.The Nemerow comprehensive pollution index method shows that the surface water of Yanglizhang,Baiyanxi,Xixibao and Xiangjiang mining areas were heavily polluted by heavy metals,the Penjiashan was moderately polluted,and Zhailanggou and Pengcheng were mildly polluted,Hongyandong is at clean level.?4?The average contents of heavy metal elements Mn,Cu,Zn,Cd,Pb,As and Hg in the sediments of the study area exceed the geochemical background values of surface sediments in Guizhou Province,exceeding the multiples of 14.95,1.57,1.77,4.97,1.27,1.57,4.60 times respectively.The comprehensive potential ecological risk index RI indicates that:the very strong ecological hazard of Xiangjiang mining area,the strong ecological hazard of Baiyanxi,Zhailanggou,Xixibao and Pengcheng mining areas,the medium-term ecological hazard of Yanglizhang,the minor ecological damage of Panjiashan and Hongyandong.?5?The average contents of heavy metals Hg,Cd,Mn exceeded the soil background values in Guizhou Province by 2.08,1.21,8.47 respectively.Cd exceeds2.67 times the secondary standard value of soil environmental quality?GB15618-1995?.The average contents of heavy metals Hg,Cd,Mn exceeded the soil background values of Guizhou Province by 1.48,1.01,2.77 respectively.Cd exceeds 2.20 times the secondary standard value of soil environmental quality?GB15618-1995?.The comprehensive potential ecological risk index RI indicates that the dryland soils in the Xiangjiang Mining Area and the Xixibao Mining Area were in a moderate ecological hazard,and the soil in other mining areas was in a slight ecological hazard.?6?The contents of heavy metal elements Pb,Cd,As and Cr didn,t exceed the“Contaminant Limits in Food”?GB 2762-2012?,and the Zn content didn,t exceed the“Zinc Health Standard for Foods”?GB 13106-1991?.The results of carcinogenic risk and non-carcinogenic health risk assessment showed that the carcinogenic and non-carcinogenic heavy metal pollution of 5 kinds of vegetables have certain risks to human health,but were acceptable.?7?The contents of heavy metals As,Hg,Cd,Cr,Pb,Zn,Cu,Ni and Mn in manganese ore tailing slag and electrolytic manganese slag leaching solution did not exceed the provisions of“Diagnostic Standard for Hazardous Waste-Identification of Leaching Toxicity”?GB5083.3-2007?.The Mn content in the leachate of electrolytic manganese slag exceeds the secondary discharge standard limit of the Integrated Wastewater Discharge Standard?GB8978-1996?.?8?The toxicity of manganese ore fresh slag,weathered slag and electrolytic manganese residue to Chinese cabbage,ryegrass,and wheat showed that it had different effects on germination rate,root length,shoot length,fresh weight,germination index and vigor index of the test seeds.Experimental studies on the toxicity of manganese tailings slag and electrolytic manganese slag on vegetables showed that:The three ratios of electrolytic manganese residue and soil?1:9,3:7,5:5?are set to plant cabbage,radish,and cowpea,the vegetables germinated and the germination rate was extremely low only in the 1:9 ratio setting;The three ratios of tailings slag and soil?1:9,3:7,5:5?are set to plant vegetables above.The results show that:With the increase of the ratio of tailings slag,the content of chlorophyll,soluble sugar,soluble protein,POD and SOD in the leaves of vegetables firstly increased then decreased.while the MDA content continued to increase.