Study On Heavy Metals In Soil Polluted By Manganese Sulphate Waste Residues

Heavy metal pollutants is the typical priority pollutants and heavy metal pollution is very serious environmental pollution problems to soil environment. The exploitation and extraction of heavy metal is primary source of pollution. Manganese sulphate waste residues come into being more and more with the development of manganese sulphate industry because of manganese extensive application in many industry areas. Some recent studies present evidences that many kinds of heavy metal contained in manganese sulphate waste residues can enter soil going with leachate and result in soil pollution. The pollution phenomenon and the degree in the soil polluted by manganese sulphate waste residues was studied, the influence degree to the crops was valued and the relativity was studied between each heavy metals'total amount, and the total amount and each species'of heavy metals.First soil samples were collected from the spot stacking manganese sulphate waste residues in Xiangtan Manganese-mine, Hunan Province and nine sampling sites were set. The total amount of the heavy metal in the samples such as copper(Cu), zinc(Zn), cadmium(Cd), lead(Pb) and manganese(Mn) are determined by atomic absorption spectrophotometry. Results showed that the total amount of heavy metals such as Cu, Zn, Cd, Pb and Mn, in soils polluted by manganese sulphate waste residue exceeds environmental background values and the second standard of soil environmental quality ones. The phenomenon of exceeding the standard is serious, Mn is the most serious one and the total amount of Mn is more than one hundred times of the standard while Pb is the least and below one time of the standard.Then all kinds of heavy metal species were extracted with Tessier's sequential extraction procedure and each species'content are determined by atomic absorption spectrophotometry. It indicated:⑴The distribution characteristics of the heavy metal species in the soils are as follow: Cu, Organically bound> residua> Fe-Mn Oxides> Carbonate> Exchangeable; Zn, residua> Fe-Mn Oxides> Organically bound> Carbonate> Exchangeable ; Cd, Fe-Mn Oxides> Exchangeable> residua> Carbonate> Organically bound; Pb, Fe-Mn Oxides> residua> Organically bound> Carbonate> Exchangeable; Mn, Fe-Mn Oxides> residua> Exchangeable> Organically bound> Carbonate. ⑵Comprehensive evaluation of the environmental impact depents on the biological activity of heavy metals. The average coefficient of bioavailability and the coefficient mobility has the same rank: Cd> Mn> Pb> Cu> Zn .At last, the relativity was studied between each heavy metals'total amount ,and the total amount and each species'of heavy metals on the base of the the total amount of heavy metals and the distribution characteristics of each species, the conclusion was drawed:⑴The linear dependence of the total amount indicates that there was a good linear relationship between Cu,Zn and Cd. The relativity between Cu,Zn and Cd was significant under the given level. It illustrates the three heavy metal pollution provids with the same source of pollution.⑵The relativity between the total amount and the species indicates: There was a good linear relationship between the total amount and F3,F4,F5 of Cu , the significant relativity under the given level shows that the total amount affects the three species and F1 and F2 has similar change tendency just like F3 and F4;There was a good linear relationship between the total amount and F1,F2,F4,F5 of Zn, the significant relativity under the given level shows that the content of F1,F2,F4,F5 species depends on the total amount. What's more, the four species affects each other;There was a good linear relationship between the total amount and any species of Cd, the significant relativity under the given level shows that any species'content depends on the total amount;There was a good linear relationship between the total amount and F4,F5 of Pb. The significant relativity under the given level shows that the total amount decides the content of F4 and F5 and similar change tendency exists between F1 and F2, likewise between F3,F4 and F5;There was a good linear relationship between the total amount and F1,F2,F3,F5 of Mn. The significant relativity under the given level shows that the total amount decides the content of F1,F2,F3 and F5, What's more, the four species affect each other and similar change tendency exists between F3 and F5.