Distribution And Migration Of Heavy Metals Among System Of The Slag,Soil And Plant In The Indigenous Zinc Smelting Area Of Northwestern Guizhou Province,China

Northwestern Guizhou Province is a place where concentrated on indigenous zinc smelting in Guizhou Province,China.The indigenous zinc smelting area has a long smelting history,especially in Hezhang and Weining Counties.Indigenous zinc smelting has some advantages compared with other advanced zinc smelting technology,such as the fact that it is not very technical and can be performed by many farmers who have little knowledge,it requires less investment,and it is easy to perform;But it wastes a certain amount of resources due to its bad recovery of metal zinc,and it might seriously contaminate the surrounding environment because the slag pile randomly stacked and the slag contained high heavy metal contents.Moreover,many researchers have mainly studied the environmental impact of the surrounding soil and water due to the slag,while few researchers have studied on the environmental impact of the vertical migration of heavy metals in the slag,especially using Cd and Pb isotopes to trace their vertical migration.In order to better understand the environmental contamination and the vertical migration of heavy metals of the slag in this area,there were taken as the research objects that the soil profiles of different stacking sites and the plants growing around them in northwestern Guizhou Province in this study.And our research is mainly focus on the vertical migration characteristics of heavy metals in the slag and systematical study on distribution and migration of heavy metals and Cd and Pb isotopes among of the soil profiles covered the slag,the slag and its surrounding plant.Through this study,there are some results or conclusions as follow:?1?In the distribution area of the clastic and the carbonate rock,most heavy metals?such as As,Cd,Pb and Zn?are obviously migrated into its covered soil profile,especially in surface soil.And there are significantly different that the heavy metal migration contents and depths of soil profile in different rock distribution areas.In the clastic rock distribution area,pollution of heavy metals As,Cd,Pb and Zn are mainly sourced of the indigenous zinc smelting slag in the soil profile of DFHHLPM1 which covered the slag.But there are obviously different in different heavy metal migration depths and contents of the DFHHLPM1section:the As migration depth is within 30 cm,Pb migration depth is within 50 cm,and the Cd and Zn migration depths are the whole soil profile.The Cr,Cu and Hg are not or a little affected by these heavy metals of the slag.In the control core?DFHHLPM2?,only Cu in all section,Zn in surface soil and Cd in soils within 30 cm are enriched and reached certain pollution levels,other heavy metals are not enriched.In the carbonate rock distribution area,the Cd,Pb or Zn contents are reached at different polluted degrees or depths in the soil profiles.This might be caused by these heavy metals from their covered slag.And Cd,Pb and Zn are obviously enriched in soil profiles near Pb-Zn mining district,which might be affected by parent rock mineralization.?2?Some heavy metals of the slag could not only contaminate its surrounding soil,but also pollute the plants growth on the slag or its surrounding soil.In the research area,there is contamination risk in heavy metals As,Cd,Cu,Pb and Zn of the indigenous zinc smelting slag?especially Cd and Pb are at high pollution risk?,in Cd,Pb and Zn of the planting soil with the slag?especially Cd and Pb?,and in Cd and Cu of the planting soil without the slag around the slag pile.Additionally,some heavy metals?i.e.As,Cd and Pb?of Juncus effusus and Artemisia argyi which used as Chinese medicinal materials are significantly exceed their standard values and obviously contaminate with these heavy metals.And although some heavy metals in potatoes and maize grains exceeded their limit values and reached a certain contamination level,the Se and Zn contents in some corn grain are abundant.Moreover,the ratios of ²⁰⁶Pb/²⁰⁷Pb in Juncus effusus are all within 1.20 and similar to these in the slag,this indicates that its Pb content might be mainly sourced of the slag.The?^114/110Cd and?^112/110Cd of root part in Juncus effusus is below its aboveground part in the indigenous zinc smelting area,this indicates that its root part could be enriched in lighter Cd isotope.?3?The Pb and Cd isotopes analysis on system of the indigenous zinc smelting slag and profile shows some conclusions in clasolite distribution area as follow:the Pb and Cd contents of the soil in the whole DFHHLPM1 profile which covered the slag are affected by the downward migration of Pb and Cd contents from the slag above the slag,especially in Pb content of the soils within 50 cm and Cd content of the soils of the whole profile;and their contamination degrees gradually weakened with the increase of soil depth.However,besides Pb content in the surface soil and Cd content in the soil within 30 cm might be also be affected by human activities,the Pb and Cd are mainly originated from weathering of parent rock in the control section?DFHHLPM2?which covered without the slag.?4?The Pb and Cd isotopes analysis on system of the indigenous zinc smelting slag and profile shows some conclusions in carbonate rock distribution area as follow:The Pb and Cd contents in the soil of JZLMCPM3 profile is mainly from natural sources,except for Cd in soils within 50 cm are also obviously affected by the slag.The Pb and Cd contents of the soil in whole section are affected to a certain extent by their downward migration from the slag;and their Pb and Cd contamination degrees from downward migration in the slag decreased with the increase of soil depth.However,some heavy metals?i.e.As,Cd,Pb and Zn?of the soil in whole section are high and reach at different enrichment degrees.This shows that some heavy metals in soil mainly inherited their content characteristics from the bedrock which is one of important reasons why some place have high geological background of some heavy metals in carbonate rock distribution area.Moreover,although the contents of Cd and Pb in JCPPM soil near Pb-Zn ore mining area are higher than those in the soil profile covered the slag,they are mainly sourced from natural source.This might be related to abnormal geological background?weathering of lead-zinc mineralized bedrock?.