Geochemical Characteristics Of Heavy Metals In Different Media In Panzhihua V-Ti-Magnetite Zone

Sulphide mines have always been the concerns of people because of their various forms and the resultant environmental problems,whereas oxide mines are paid less attention and not studied much because they do not cause obvious environmental problems such as acid mining drainage (AMD).However,the potential environmental problems caused by oxide mines can not be ignored.Under the support of the two projects,The National Scientific and Technologic Project (2005BA901A03) and The International Cooperation Project(2005DFA20900),the author chooses Panzhihua V-Ti-Magnetite,a famous oxide mine in China,as the subject of research.In this thesis, the geochemical characteristics of heavy metals in various environmental media in the zone(such as water,soil,atmosphere and plants) during the process of mining are systematically studied by using those media as research carriers and employing the analyzing methods of ICP-MS and ICP-OES.The research results are shown below:(1)The research on the geochemical characteristics of heavy metals in the system of water-suspended solid-sediment in the mining zone show that:the contents of heavy metals in water are very low,while those in suspended solids and sediments are relatively higher;the contents of Cu,Zn,Co,Ni,Fe and As in suspended solids are higher than those in sediments;the contents of Pb,V,Ti and Cr in sediments are higher than those in suspended solids.The partition coefficients show that:Hg is most active,As and Ni are less active,and Ti is least active.The morphological analyzing results of sediments show that in the sediments in Panzhihua Mining Zone, Ti is most stable,V,Cu and Cr are relatively stable,and Zn,Mn,Co and Ni are more active.The index evaluation on potential ecological risk shows that most heavy metal elements in the sediments are contaminated,whether heavily or in a medium degree,in which Cu,Co,V and Ti are contaminated heavily or even more severely.The potential ecological risk index shows that all places are in light ecological risk and generally the potential ecological risk of heavy metals in the sediments are not high and they have limited influence on environment.(2)The geochemical activity and transferring features of Vanadium in soil are studied by doing the partition coefficient and penetrating tests of Vanadium between soil and water and the transferring test of vanadium in soil as well as analyzing the chemical forms of Vanadium in soil.In the tests,various parameters and features of vanadium are analyzed.The adsorption isothermal curves show that loam soil is most absorptive to V,sandy soil is less absorptive,and V is positively correlative to K_d in certain temperature ranges.The changes of pH to the partition coefficient in both loam soil and sandy soil are identical.The penetrating coefficients in different soils are different and the absorbing coefficient of sandy soil is obviously higher than that in loam soil.In soil,most vanadium takes the form of residua,which shows that vanadium is not active in soil.(3)The geochemical characteristics of heavy metals in the soils in the mining zone is studied and the potential ecological risks of those heavy metals are evaluated.The heavy metals are distributed around the stope and dump and the change of the elements on the surface of the profile is generally greater than that on the underlayer.Through the correlation analysis and the clustering analysis,the heavy metals in the soil are classified into two classes:Zn,Cd,Pb,Hg and As belong to one class while V,Co,Ti,Cu,Ni,Cr and Mn belong to the other.For samples from different areas,the correlations and clustering results of those heavy metals are different.That may be caused by the type and feature of soil in the sampling places or the degree of man-made pollution in the area.The evaluation on the potential ecological risk of heavy metals shows that the contamination of most heavy metal elements in the surface soils in Panzhihua mining zone are medium or heavy.Judged by the potential ecological risk index,only one place are in strongly high ecological risk.Generally,the ecological risk of heavy metals in the zone is not high.(4)The geochemical characteristics of two kinds of atmospheric particle in Panzhihua mining zone and mining activity area.The results show that contents of heavy metals in atmospheric dust and near-earth-surface atmospheric particle in Panzhihua mining activity area are very high and the contents of the elements,such as V,Ti and Fe,related with mining activity are especially high and can be up to several or even more than ten times of those in other cities in Chengdu Economic Zone. The morphological analysis of heavy metals in near-earth-surface atmospheric particle shows that the contents of ion-exchange and carbonate-bound of Cu,Pb,Zn,Co,Ni and Mn are higher and have significant effect on environment,V and Cr have less effect on environment,Ti residua accounts for more than 99%and has very little effect on environment.The study on the granularity of near-earth-surface atmospheric particle and the mineralogical research show that the granularity of the near-earth-surface atmospheric particle is very thin,most are thinner than 80um and mainly fall in the range of 20-50um,and only some are thinner than 20um;the mineral are mainly composed by quartz,then by feldspar and gesso,and then by carbonate minerals.(5)The characteristics of heavy metals in the tree ring samples in different areas are studied. The results show that,in a certain extent,the tree ring can reflect the contamination degree of heavy metals in the mining zone and the heavy metals in the tree ring in different areas are related with the mining activity in the area.Through contrast,it is found that the heavy metals in the tree ring are obviously positively correlated with the root soil and the elements in the tree ring are not only from soil but probably from atmospheric deposition.(6)The correlation heavy metals in different media as well as the source,the existing form and the transform of heavy metals are studied.There are two sources for the heavy metals in different media in the mining zone:one is the natural weathering of basic and ultra-basic rocks that contain heavy metals and the other is the mining activity,and the latter is the main reason.Most heavy metal elements exist in mineral crystal lattice in the form of residua.For some elements,the proportion of their organic bound and carbonate-bound is also higher.The heavy metals in different media in the mining zone mainly activated and transferred physically.Under natural conditions,the heavy metals have the same transforming relation with all other elements,that is,transform and cycle between rock,soil and water under the action of weathering and sedimentation.Whereas, under the human conditions,heavy metals in different stages of mining activity transform and cycle between soil,atmosphere,water and plant by exhaust gas(raised dust and exhaust gas),liquid waste(waste water),solid waste(waste residue,mullock,gangue). (7)The geochemical characteristics of heavy metals in sulphide mines and oxide mines are contrasted and the geochemical characteristics of heavy metals are summarized.It is found that the geochemical characteristics of heavy metals in the two mines have not only similarity but also difference.And the biggest difference is that the content of chalcophile elements in environmental media of sulphide mines is far higher that in oxide mines and the biggest pollution for oxide mines is that caused by atmosphere dust and heavy metals,while the biggest pollution of sulphide mines is that caused by acid mining waste water.The similarity between the two mines is that their morphological features are same.