您好,欢迎来到化拓教育网。
搜索
您的当前位置:首页Evaluation of ecological risk and primary empirical research on heavy metals in polluted soil ov

Evaluation of ecological risk and primary empirical research on heavy metals in polluted soil ov

来源:化拓教育网
Available online at、^n^n^,.sciencedirect.com 二 ScienceDi rect ELSl三VIER P ress Trans.Nonferrous Met.Soc.China 20(20 1 01 688~694 Transactions of Nonferrous Metals Society of China WWW.tm柚sc.en Evaluation of ecological risk and primary empirical research on heavy metals in polluted soil over Xiaoqinling gold mining region,Shaanxi,China wu Yao—guo(吴耀国) ,XU You.ning(8 ̄,,友宁) ,ZHANG Jiang—hua(张江华) ,HU Si_hai(胡思海) 1.Department ofApplied Chemistry,Northwestem Polytechnical University,Xi’an 710072,China; 2.Xi’an Institute ofGeology and Mineral Resources,Xi’an 710054,China Received 6 July 2009;accepted 1 1 January 2010 Abstract:Soil,crop and residents’hair over Xiaoqinling gold mining region,China,which was selected as a case study,were sampled and analyzed for Hg,Cd,Pb,Cu,Cr,As and Zn concentrations.The concentrations of heavy metals in soil or crop and hair samples were used to assess their potential ecological risks.or to find the responses to these metals as evidences to prove the potential risk was coming down to observed harm,respectively.The results showed that,these metals in soil were ranked by severity ofecological risk as Hg>Cd>Pb>Cu>Cr>As>Zn.based on their single.element indexes.In the view ofthe potential ecological risk indexes,of a1l soil samples,about half had signiicantlfy high or high potentia1 ecologica1 risk.which covered more than 74%Of the studied region.Most of the risks were 97.4 1%from Hg Pb and Cd.especially,84_37%from Hg.Both the single.dement and potential ecological risk indexes indicated that.the ecological risk grades had a special spatial characteristic.and increased from northwest to southeast generally.This was agreed with the spatial distribution of the strength in gold mining activities over the studied region.The concentrations of Hg and Pb were higher than their relative backgrounds in the coms.and were even 9.48 and 25.09 times higher than their relative backgrounds in residents’hair,respectively.A1l these showed that the heavy metals in the soil had a high potential ecological risk,especially,had been affecting these crops’growing and yield,and even the residents’health through food strains.Obviously,these metals’potential ecologica1 harm had been coming down to observed harm to the ecology. Key words:gold mining activity;soil pollution;heavy metal;potentia1 ecological risk a great progress has been made[2—9].Meanwhile,more 1 IntrOductiOn It is well known that.the soil.over a gold mining region,is always polluted by heavy metals,which are released from gold mining activities.Because these metals are toxic to living organisms,and even are several pollutants where ingestion of contaminated food has led and more studies and practices showed that,such results from the risk assessment have liRle capability to reveal the real degree of their potential toxic effects completely, especially,no capability to show whether the potential toxic effect is coming into an observed harm of ecology and its degree.So,based on the results,relative strategies and methods were taken to centrel the risk and even their practices usually were not operated in time.Therefore.a to human death[11,such researches on ecological risk assessment of heavy metals in the polluted soil had great harm of ecology would be happened in the end. Obviously.in order to obviate an ecology system to be harmful_it is important to do assessment of ecologica1 risk;meanwhile,it is necessary to do primary empirical researches too. goRen more and more attention[2—71.It was found that the results of the ecological risk assessment can reveal the possibility for soil to be polluted.and even for the ecology to be harmed by concerned heavy metals[8],so these results were usually used to serve as a guide for all Xiaoqinling gold mining region,which is the second larger Au.producing area in China.is located in US Environmental Protection Agency(EPA)programs and regional ofices to supplfement or update the policies, practices and guidance.Therefore,such researches have got much attention from researchers over the world.and eastern Shaanxi Province rN 34。23'-34。40 and E 110。09L110。25 ),northwestem China(Fig.1).The Au production in the area from 1 980 to 2003 reached 56.25 t Foundation item:Project(1212010741003)supported by the Ministry of Land and Resources of China;Project(SJ08一ZT08)supported by the Natural Science Foundation of Shaanxi Province,China;Project(NCET-07-0694)supported by Program for University Talents in the New Century,China Corresponding author:WUYao—guo;Tel:+86—29—88431962;E-mail:wuygal@163.com DOI:10.1016/S1003—6326(09)60199-0 wU Yap—guo.et al/Trans.Nonferrous Met.Soc.China 20(20 1 01 688—694 689 Fig.1 Location of studied region and its landscape distribution [1 0].During the 1 980s and 1 990s,artisanal Au mining activities were popular in the region and more than 1 5 000 people were involved in Au mining activities. Presently,there are 29 large Au mining companies involving 6 000 workers.Most of gold is extracted from original Au ores by amalgamation,meanwhile,waste water during these processes is directly discharged and resulted in both soil and water heavy metals pollution. Although severa1 researches had been conducted on the soi1 heavy metals pollution and the source and transport paths of several metals were determined『l1],there were few researches conducted on ecological risk assessment of these heavy metals,and no such studies were conducted to determine whether the potential toxic ef.fect is coming into the observed harm of ecology and its degree.So,the goals of this study were to do the potential ecological risk assessment of heavy metals in the soil,and to find testimonies to confirm that the potential risk was coming into an observed ecological harm. 2 Materials and methods Xiaoqinling gold mining region is situated in the Loess Plateau.and its average elevation is 1 500 m above sea leve1.It has a t ̄ical temperate zone terrestrial monsoon arid climate.The average annual rainfall is 625.5 mm.and the average annual temperature is 13℃. Based on its geochemica1 landscape characteristics. the region is divided into five areas.the rock base mountain area. 1oess ravined tableland.piedmont alluvial。pluvial inclined tableland,Shuangqiao River alluvial terrace area.and Yellow River and Weihe River alluvial plain area.In the rock base mountain area,there are lots of gold ores and several gold mines(Fig.1、. However,there is few soil.so it is suitable for agricultural activity and not included in the studied area. and the other four areas were selected as studied region. Among these four areas.Yellow River and Weihe River alluvial plain area is the only one which is occupied mainly by agricultural activities.and the others are cooperated in mixtures of agricultural and gold—mining activities.Although agricultural activities are conducted all over the other three,most of them are condensed in the area close to Tongguan county. According to its 1ocal records.Au mining was first initiated in the region about 900 years ago[1 0].Large— scale Au mining activities began in 1 975 1 1 2].About 72 abandoned ancient Au mines were known in the Tongyu. Haochayu,Taiyu,and Dongtongyu areas(Fig.1). Presently,there are many gold mills,and almost are mainly in Shuangqiao River alluvial terrace area(Fig.1), and the annual Au production reaches 2.5-3.0 t in the regiona『l0]. The Au processing mills are distributed along severa1 streams that are tributaries of the Ye:llow River (Fig.1、and wastewater from these mills is directly discharged into these streams.During the 1 980s and 1 990s.artisanal Au mining activities were popular in the region and more than 1 5 000 people were involved in Au mining activities.in which elemental Hg was used widely for Au extraction.Artisanal Au mining activities mainly occurred along the streams in Tongguan county. Artisanal Au mining in Tongguan county has declined significantly since the Chinese ban of such activities in 1 996.but there are presently a few artisanal Au mines still operating.Generally,elemental Hg is used usually by these companies for extraction of Au.To date.at least eight million tons of tailings have been produced from mining in this area,and the average Hg content in the tailings is approximately 630 mg/kg,which is significantly elevated compared with the average Hg content(0.069 mg/kg)in original Au ores.So,the soil had been polluted by the heavy metals released from 690 wu Yao—guo.et al/Trans.Nonferrous Met.Soc.China 20(20 1 0)688—694 of the studied region,was selected as the background site. Several soil samples were collected there and analyzed or metfal concen仃ations.And Hg。Pb.Cu or As concentrations determined were 0.1 3.32.57.20.7 1 and 1 5.1 3 mg/kg as relative background.respectively. 34 crop samples which included wheat, B. Chinensis var.Communis,Lactuca sativa.L.var.romana, these gold mining activities[12]. Soil sampling was carried out in July 2006.The studied region was divided into a grid of 1 92×1 92 cells using a systematic grid sampling method with regularly spaced intervals of about 250-250 m.Within each grid cell five samples were randomly collected to a depth of 0—1 5 cm and then mixed thoroughly to give a composite sample.The sampling protocol was,therefore,a green vegetables and radish,and 20 hair samples from the residents over the regional were gotten and analyzed combination of systematic grid,simple,random and composite sampling methods. ofr the heavy metal cOncentrati0ns. After air—drying,mixing and milling,soil sub- Statistical analyses were conducted using Microsofl samples were digested with aqua—regia f4:1 HC1-to— Excel and SPSS 1 0.0 1 software.Linear regression HN03 by volume)according to the Refs.[13—15]to analysis and factor analysis of the concentration were determine the concentrations of Cu.Zn.Pb and Cd.The performed using STATISTICA for Windows.Release 5.0. total concen仃ations in the solution of Cu Zn and Pb Copyright StatSoft.Inc. 1984-1995.The method were determined by flame atomic absorption suggested bv HAKANS0N『1 9]was used to do the spectrophotometry(Varian SpectrAA 220 FS)and of Cd ecological risk assessment. with a Varian SpectrAA 220Z spectrophotometer using a graphite furnace. 3 Results and discussion Soil sub—samples were digested with HNO1 and HCl0d for determination of the metalloid As.and with The metal concentrations in 1 33 soil samples were HNO and H20,for the metal Hg.The concentrations of done through statistica1 analyses with Microsoft Excel these three elements in the solutions were determined by and SPSS 1 0.0 1 software,and descriptive parameters and hydride generation.atomic fluorescence spectrometry probability distributed are obtained and listed in Table 1. (Titan AFS 930).Quality control was based on the The Pb concentrations fabout 3 450 mg/kg) combined use of the GSS series of Chinese standard soi1 (between the minimum and maximum values)was the reference materials『1 61 with intemal control samples and 1argest,and its variation(Standard deviation=487.83), duplicate analyses of each sample. Selected soil mean(2 1 6.93 mg/kg)and mode(32.00 mg/kg)were also physicochemical properties,namely pH and mechanical the highest of all the studied samples.This suggests that composition were also measured.The data and heavy there are severallocations having great Pb concentrations. metal concen仃ations have been discussed elsewhere『171. and the soils have been co・ntaminated more severely by Soil heavy metal concentrations were analyzed by this meta1.The ratios of mean to background value for principal component analysis(PCA)and correlation most metals,except Cr and As,are larger than 1.0,and analysis uSing Version 11.5 of the SPSS software are ranked in following order:Hg>Pb>Cd>Cu>Zn. package(SPSS Inc.,Chicago,IL).In the PcA,varimax This means that the human activities have signiifcant that was proposed by KAISER(1958)[18]was used as effects on the concentrations for almost metals in soils the rotation method in the analysis following over this studied region.and the soil is polluted by these standardization of the data. metals. ACCOrding to the local climate.prevailing wind Correlation analysis was conducted to determine the direction is from northwest to southeast generally.Under extent of the relationships among metals in soils over the respecting to this wind and its effect on air studied region.The correlation matrix in Tab1e 2 shows transformation,Mengyuan,which was in the northwest that As is negatively correlated with any metal in soils Table 1 Summary statistics of heavy metals in soils over studied region wU Yao—guo.et al/Trans.Nonferrous Met.Soc.China 20(2010)688—694 Table 2 Correlations between heavy metal contents in studied soils over studied region 691 over the studied region,suggesting perhaps different soil sources from other metals.Hg,Pb,Cd,Cu,Cr and Zn are closely related to each other >0.92,P<0.01 .This mentions that Hg,Pb,Cd,Cu,Cr and Zn may have Table 3 Evaluating standards of heavy metal contamination on farmland soils(mg・kg ) another originate.Obviously.the soil pollution sounded complex in several kinds of heavy metals and their sources.This is agreed with XU et al『12],and mentions that it is dificultf to protect the soil from the heavy metals pollution. The assessment of soil contamination was conducted using the contamination factor and degree.In the version suggested by HAKANSON[1 9], an assessment of soil contamination was conducted through reference of the concentrations in the surface layer of bottom sediments to pre—industrial concentrations: r1iEnvironmental quality standard for soils(GB15618--1995),Ministry of Environmental Protection ofthe People’s Republic ofChina[20]. C L/n r一 (1) four categories of Ca,five categories of categories of .as shown in Table 4. ,and four where C|is the mean concentration of an individua1 metal examined and is the pre—industrial Based on the single—element index(cr )and its grades(Table 4),the soil around Tongguan county and over Yellow River and Weihe River alluvia1 plain area, concentration of the individual meta1.In our work.the background concentration of a metal in the regional soil was classiied as consifderably contaminated with As. The soil of piedmont alluvial—pluvial inclined tableland. (Table 3)was applied as the pre—industrial concentration of each individua1 meta1.Cr iS the single element index. The sum of contamination factors for al1 metals Shuangqiao River alluvia1 terrace area.was contaminated with Hg,Pb,Cu,Cd and Zn.It was interesting that,the soil polluted seriously by As or Hg,Pb,Cu,Cd and Zn, was distributed over agricultural or gold mining area, examined represents the contamination degree(Ca)of the environment: respectively.This may be used to prove the guess (2) E is the potential ecological risk index of an individual meta1.It can be calculated by mentioned above on metal sources and their complex to be right. Among these metals,the range and means of the potentia1 ecorisk index of Hg were the largest.The second was Pb.then followed by Cu,Zn,As and Cr =C;× (3) (1’able 5).This agreed with the results obtained from 11able 1. where is the toxic response factor provided by 0f all soil samples.the ratios of the soi1 samples with low potential ecological risk,moderate potential ecological risk,high potential ecological risk and signiicantly high potentialf ecological risk,were determined.respectively.The results showed that.for al1 Hg,Pb,Cd,Cr,As,Cu or Zn HAKANSON[19](Tr for is 40,5,30,2,1 0,5 or 1,respectively).R is the potential ecological risk index,which is the sum of : sampling sites,there were 2 1.05%of the sites had high risk,and 28.57%had significantly high potential HAKANSON[1 9]defined four categories of G , ecological risk.and both were about 49.62%.And the wu Yao—guo,et al/Trans.Nonferrous Met.Soc.China 20(20 1 0)688—694 risk index.Most of these potential ecological risk indexes,especially for Hg,were much larger than 80, and even 1 8 830.77.so that the risk grades were in considerable potential ecological risk,high potential ecological risk and significantly high potential ecological risk.and these samples were 88.73%Of all the studied 693 pass into human body through food chain,thus the resident health was hardly escaped from the stress of these heavy metals. In order to reveal the ef1’ect of the gold mining activities on the resident’s health,20 hair samples from the residents over the studied region,and 4 hair samples from background were obtained and analyzed for Hg,Pb, samples.On con仃ary,out of all the studied soil samples. samples with significantly high and high potential Cd.Cu and Zn concen仃ations(the data was not given). The cOncentratiOns showed that.these heavy metals. which existed in both the soi1 and the crops.were also ecological risks for Pb.Cd and Cu were 6.02%,9.77% and 1.50%.respectively.Obviously,the studied heavy metals can be ranked by severitv of ecologica1 risk as follows:Hg>Cd>Pb>Cu>As>Cr>Zn. The potential ecologica1 risk indexes 1 for all the studied soi1 samples were distributed with a site.specific characteristic(Fig.2).The soil samples with signiifcantly high potential ecologica1 risk were distributed over the east part from Taiyao village.and the soi1 samples with high potential ecological risk were distributed over the area between Taiyao village and Tongguan county.Over the last part of the studied region,the west part from Tongguan county,there were the soil samples with low potential ecological risk.Generally,the grade of potential ecological risk was increased from northwest to southeast.This characteristic was agreed wel1 with the distribution of the gold mining activities(Fig.1 1. From all above,it was concluded that these heavy metals in the studied regional soil were resulted mainly from the gold mining activities,and had large potential to affect the ecology.The results of the study conducted by CAO et al[2]showed that,the heavy metals in the polluted soil had the potential to affect crops.and the effect could be observed. Actually,the metals accumulated to shield concentrations and then caused toxic to the crops,so the effect could be observed. Otherwise,the effect was not easy to be observed, although the stress of the metals existed.Under this condition.the heavy metals concentration is a good index to show the stress of the metals to the crops. The common crops(wheat,B.Chinensis var. Communis,Lactuca sativa.L.var.romana, green vegetables and radish)were sampled in the studied region and the background,and were analyzed for Hg, Pb.Cd.Cu and Zn concentrations(the data were not shown).The concentrations in the crop samples rfom the studied region were higher than relative ones from background.For examples,the mean concentrations for Hg,Pb and Cd in the wheat from the studied region, were 5.11.5.69 and 5.12 times higher than their relative concen仃ations from background.and also higher than their relative tolerance limit of iron in foods in national standards of China.Therefore,the yield of the crops and its quality were in a great risk to be affected by the heavy metals from the gold mining activities.This also mentioned that these heavy metals in the crops would found in hair samples from the residents.no matter whether how old,and male or female they were.And the concentrations were not only higher than their relative backgrounds[18],but also higher than relative limits in GBW-0760 1[2 1].Especially,the means of Pb and Hg concentrations.were 9.48 and 5.09 times higher than their relative backgrounds.and were 8.64 and 7.64 times higher than their relative limits in GBW 0760 1. respectively.It was worth mentioning that.1 5 of the surveyed 20 residents did not feel well and had something wrong with their healthy,such as weak chest, dizzy and high blood pressure.On the contrary,these phenomena were not commonly found among the residents in the background.Al1 these strongly revealed that these heavy metals in the soils and crops due to the gold mining activities,had being affected the residents’ health 4 Conclusions 1)Hg,Pb,Cu,As and Cr heavy metals in the polluted soil,were sourced from gold mining activities, and these metals with higher concentrations were mainly distributed around the gold mills over the studied region. 2、The potentia1 ecological risk indexes of these metals in most soil samples were more considerable,and in about 49.62%soil samples were high or significantly high potential ecological risk,which covered 74.54%of all the studied area.A11 these mean not only that the soil had been polluted seriously by heavy metals,but also these heavy metals were ready to be toxic to the environment. 3、These heavy metals concentrations in crops were higher than their relative backgrounds and even than relative limits in the national food standards (GBW-0760 1),respectively.Unfortunately,these metals were also found in hair from the residents and their concentrations were higher than relative backgrounds. These proved that the risk had come into observed harm to environment and even to human beings. References [1] National Academy of Sciences.An assessment of mercury in the 694 wU Yao—guo.et al/Trans.Nonferrous Met.Soc.China 20(2010)688—694 environment[RJ.Washington,DC:National Academy of Sciences, National Research Council,1978. [2] CAO H C,LUAN Z Q,WANG J D,ZHANG X L.Potenfia1 ecological irsk ofcadmium,lead and arsenic in agricultural black soil in Jilin Province,China[J】.Stoch Environ Res Risk Assess,2009,23: 57-64. [3] PEKEY H.KARAKA D,AYBERK S.Ecological risk assessment using trace elements from surface sediments of Izmit Bay (Northeastern Marmara Sea)Turkey[J].Marine Pollution Bulletin, 2004,48:946—953. [4】 CHEN C M.LIU M C.Ecological risk assessment on a cadmium contaminated soil landfill—A preliminary evaluation based on toxicity tests on local species and site-speciifc information[J]. Science ofthe Tota1 Environment,2006,359:120-129. [5] BOEKHOLD A E.Ecological risk assessment in legislation on contaminated soil in The Netherlands fJ】.Science of the Total Environment.2008.406:5 1 8-522. [6] POSTHUMA L.EIJSACKERS H J KOELMANS A A.Ecological effects of dilfuse mixed pollution are site—speciifc and require hi er-tier risk assessment to improve site management decisions:A discussion paper[J1.Science of the Total Environment,2008,406: 503-5l7. [7] CAEIRo S COSTA M H,RAMOS T B,FERNANDES F, SILVEIRA N.COIMBRA A,MEDEIROS G,PAINHO M. Assessing heavy metal contamination in Sado Estuary sediment:An index analysis approach fJ].Ecological Indicators,2005,5:151—169. [8] FAIRBROTHER A.WENSTEL R.SAPPINGTON K.Framework for metals risk assessment【J].Ecotoxicology and Environmental Safety,2007,68:145—227. [9] FENGXB,DAIQQ,QIUGL,LIGH,HE L,WANGDYGold mining related mercury contamination in Tongguan,Shaanxi Province,P R.China[J】_Applied Geochemistry,2006,21: 1955-1968 [10] DAI Q Q.Environmental geochemistry study of mercury contamination from gold mining areas by amalgamation technique in China—A case study from Tongguan county of Shaanxi Province【D] Beijing:Instiutte of Geochemistry,Chinese Academy of Sciences, BeOing,2004.(in Chinese) [1 1] HONG C0.LEEDK.CHUNGDY.KIM P J_Liming effects on cadmium stabilization in upland soil affected by gold mining activity [J].Arch Environ Contain Toxicol,2007,52:496—502. 【12] XU Y N.KE H L.ZHAO A I.Assessment of heavy metals contamination of farmland soils in some gold mining area of Xiao Qinling『J].Chinese Journal of Soil Science,2007,38(4):732—736. (in Chinese) [13] McGRATH S P-CUNLIFFE C H.A simplified method for the extraction ofthe metals Fe,Zn,Cu,Ni,Cd,Pb,Cr,Co and Mn from soils and sewage sludges[J】_Journal of hte Science of Food and Agriculture.1 985,36:794-798. [14] SWARTJES F A.CARLON C.de WIT NHSM.The possibilities for hte EU wide use of similar ecological risk.based soil contamination assessment tools[J].Science of the Total Environment,2008,406: 523-529. [15】 ZHAO H K.GAN J M.Study of absorbance of seven elements in atomic absorption spectrometer[J].Chinese Journal of Spectroscopy Laboratory,1998.15:104—107.(in Chinese) 【l6] Geological standard reference samples【M].Beijing:Geological Publishing House.1987.(in Chinese) [17] ZHANG C B,LI Z B,YA0 C X.Characteristics of spatial variability of soil heavy metal contents in contaminated sites and their implications for source identiifcation[J].Soils,2006,38:525—533. (in Chinese) [18] KAISER H F.The varimax criterion for analytic rotation in factor analysis[J】.Psychometrika,1958,23:187—200. [19] HAKANSON L.An ecological risk index for aquatic pollution control:A sediment logical approach[J].Water Res,1980,14: 975-1001. 【2O] GBl5618—1995.Environmental quality standard for soils[S]1995. (in Chinese) [21] GB15201—94,GB14961—9,GB2762—94,GB14935—94,GB 48l —94.GBl5199—94.GB131O6—_91.Ministry of health of the People’s Republic of China,tolerance limit of nitirte in foods[S]. 1994.(in Chinese) (Edited by LI Xiang-qun) 

因篇幅问题不能全部显示,请点此查看更多更全内容

Copyright © 2019- huatuo9.cn 版权所有 赣ICP备2023008801号-1

违法及侵权请联系:TEL:199 18 7713 E-MAIL:2724546146@qq.com

本站由北京市万商天勤律师事务所王兴未律师提供法律服务