Heavy Metal Content Of The Plants And Soil Of Baoji City Dongling Lead And Zinc Smelter In The Surrounding Area

In recent years, metallurgical industry productions spring up like mushrooms in areas. Large number of ore, fuel have been consumed and have brought about a lot of wastes with heavy metals in the smelting process of metallurgical industry. These "three wastes" pollutants enter into the air, soil and underground water by various channels, causing heavy metals exceeding standard already established in the soil and crops in the metallurgical industry areas or areas around the factory and posing a threat to human health.Blood lead level was found unexpectedly to exceed the standard seriously in conducting an examination of trace elements in the body at the end of July 2009 to the children in Sun-jia-nan-tou village and Ma-dao-kou village in Changqing Town of Fengxiang County, and Dongling Group was suspected the culprit of the event. By undertaking on-the-spot investigation and sampling and indoor analysis of samples, this paper mainly studies the content of heavy metals in 19 families 41 genera 48 species plants widely seen and the corresponding soil around Dongling Lead-Zinc Melting Plant, enrichment and transport characteristics of the sampling plants to heavy metals, the correlation between various heavy metals content in the soil, heavy metals content in the sampling plants and the corresponding soil, and carries out a environment risk evaluation on heavy metals content in the soil by using the single pollution index, the nemerow composite pollution index and the potential ecological risk index so as to explore that the metallurgical industry production of Dongling Group has caused the situation of the heavy metals pollution and influences posed to the local residents, thus to make a solid foundation for the research on the happened lead poisoning incidents to the local children, and also to provide a certain reference for governance of soil heavy metals pollution by taking advantage of phytoremediation technology in this area. The main conclusions reached by this study are as follows:(1) The content of various heavy metals in the soil around Dongling Lead-Zinc Melting Plant differ greatly. The average value of the heavy metals content are Pb56.18mg/kg, Zn83.79mg/kg, Cu26.24mg/kg, Mn248.65mg/kg, Cd3.41mg/kg, Cr116.71mg/kg and Ni70.75mg/kg respectively, they are ordered from high to low as follows:Mn>Cr>Zn>Ni>Pb>Cu>Cd, thereinto, the content of Pb,Zn,Cu,Cd,Cr,Ni are all higher than the soil elements'background values of shaanxi province; Judging from the spatial distribution characteristics, the content of Pb,Zn,Cu,Cd in the downwind direction's soil(The distance from the center of factory chimneys is about 500m) of the study area's prevailing wind are all significantly higher than the content of corresponding heavy metals in the upwind direction's soil. (2) A certain ecological risk exists in the soil around Dongling Lead-Zinc Melting Plant. Judging from the single pollution index. Mn doesn't constitute a pollution yet, Zn, Cu and Cr are all mild pollution, Pb and Ni are allmoderate pollution, Cd is a severe pollution and it is main exceeding standard factor of heavy metals; The nemerow composite pollution index is 27.52, the pollution degree of soil has reached to heavy pollution level; The pollution of heavy metal pollutants is the degree of severe pollution; The general potential risk index of heavy metals pollution in the soil ranges from 581.06 to 1611.45, the ecological risk is very strong, this shows that the ecological risk level of heavy metals pollution in the soil around Dongling Lead-Zinc Melting Plant in Baoji is very high.(3) The content of various heavy metals of all sampling plants around Dongling Lead-Zinc Melting Plant doesn't reach the standards of hyper-accumulators. However, the maximum content of Pb in the aerial parts of avena fatua, conyza canadensis and erigeron annuus are 153.70mg/kg, 198.15mg/kg and 159.20mg/kg respectively; the maximum content of Pb in the underground parts of the three plants above are 369.80mg/kg,100.17mg/kg and 273.31mg/kg respectively, and they all show attribute of big biomass and easy harvest, thus they are important Pb-resistance plants.(4) The enrichment ability to Pb, Cu, Cd in the aerial parts of different plants around Dongling Lead-Zinc Melting Plant varies greatly, and their change ranges are even bigger than Zn, Mn, Cr and Ni. The change ranges of enrichment ability to Pb, Zn, Cu, Mn, Cd, Cr and Ni in the underground parts of different plants in the soil are also big.The Erigeron annuus, Trifolium repens, Plantago depressa, Humulus scandens, Potentilla chinensis and Avena fatua in the sampling plants can effectively absorb great amount of Pb from soil, so they are good plants to resort Pb-polluted soil; the enrichment coefficients of Cu in the aerial and underground of Cynanchum chinense are all above 1 and the content of Cu in Cynanchum chinense is also relatively high, so it is good to restore Cu-polluted soil; The Erigeron annuus, Phragmites australis, Trifolium repens and Artemisia scoparia can effectively absorb great amount of Cd from soil, so these plants can be used to restore relatively serious Cd-polluted soil. The root of Portulaca oleracea can effectively enrich Pb, Zn, Cu, Mn, Cr and Ni in the soil, so it is promising to restore heavy metals-polluted soil.(5) The transport capacity of different plants to Cd, Cr and Ni in the soil around Dongling Lead-Zinc Melting Plant varies greatly, and their change ranges are bigger than Pb, Zn, Cu and Mn. The transport coefficients of Tribulus terrestris of all sampling spots to all kinds of heavy metals in the soil are all above or close to 1, the transport capacity is sronger, and there is a high biomass in its aerial part, so it is alternative plant to restore the heavy metal-polluted soil; Most of the transport coefficients of Digitaria sanguinalis, Avena fatua, Trifolium repens, Ligusticum tachiroei and Portulaca oleraceu to all kinds of heavy metals in the soil are all below or close to 1, the transport capacity are all weaker.(6) The correlations of various heavy metals content in the body of the sampling plants, different parts of the sampling plants and corresponding soil around Dongling Lead-Zinc Melting Plant are different. The correlations between the content of Pb and Zn, Pb and Cd, Zn and Cd in the aerial part and underground part of the sampling plants are all better;the correlations of Zn, Mn and Ni content between the aerial part and underground part of the sampling plants are all better; the correlations between the content of Zn in the aerial part of the sampling plants and the content of Zn, Cu in the corresponding soil are all better;the correlations between the content of various heavy metals in the underground part of the sampling plants and corresponding soil are all worse.