摘要
估算水系沉积物的地球化学背景值和识别其异常对人为污染判别与环境风险评估非常重要。采集并分析了珠江58件水系沉积物样品,经分析检验,Al、Fe和Sc被选作参考元素,并对比了确定地球化学背景及识别异常值的方法。其中,基于最小截断二乘法的回归分析是定义地球化学背景的有效方法,它是一种对异常值不敏感的稳健统计方法,而基于局部富集因子的箱线图和回归诊断图更适用于识别异常值。珠江不同河段重金属污染存在差异,北江和河网区主要受As、Cd、Cu、Pb和Zn污染,东江主要受Cu、Cr和Ni污染,而西江几乎不存在重金属污染。水系沉积物的主要污染类型是点源污染,主要污染来源是采矿和电镀等相关的工业活动。
Estimating the background values and identifying anomalies are very important to discriminate anthropogenic contamination source and assess environmental risk of heavy metals. We collected and analyzed 58 sediment samples from different branches and channels of the Pearl River,China. Based on geochemical and statistical analysis,Al,Fe and Sc were proved suitable for as reference elements. Different methods of obtaining geochemical background values and outliers of heavy metals were presented and compared in this paper. A useful way to estimate the geochemical background values is provided by regression based on the least trimmed sum of squares(LTS),which is a robust statistical approach showing low sensitivity to outliers. Both boxplots of local enrichment factor and regression diagnostic plots turn out to be better for identifying outliers. Results show that contamination varied in the different segments of the Pearl River. The North River and Pearl River channels were contaminated by As,Cd,Cu,Pb and Zn and the East River by Cu,Cr and Ni while there was almost no contamination in the West River. Point source contamination remains a major cause of contamination to sediments. Main sources of heavy metals may be industrial contamination such as mining and electroplating.
引文
[1]FOSTER I D L,CHARLESWORTH S M.Heavy metals in the hydrological cycle:Trends and explanation[J].Hydrological Processes,1996,10:227-261.
[2]SEGURA R,ARANCIBIA V,Zù?IGA M C,et al.Distribution of copper,zinc,lead and cadmium concentrations in stream sediments from the Mapocho River in Santiago,Chile[J].Journal of Geochemical Exploration,2006,91(1/3):71-80.
[3]HAKANSON L.An ecological risk index for aquatic pollution control.A sedimentological approach[J].Water Research,1980,14(8):975-1001.
[4]MULLER G.Index of geoaccumulation in sediments of the Rhine River[J].Geological Journal,1969,2(3):108-118.
[5]SZEFER P,GLASBY G P,KUSAK A,et al.Evaluation of the anthropogenic influx of metallic pollutants into Puck Bay,southern Baltic[J].Applied Geochemistry,1998,13(3):293-304.
[6]JIANG J,WANG J,LIU S,et al.Background,baseline,normalization,and contamination of heavy metals in the Liao River Watershed sediments of China[J].Journal of Asian Earth Sciences,2013,73:87-94.
[7]?EVIK F,G?KSU M Z L,DERICI O B,et al.An assessment of metal pollution in surface sediments of Seyhan dam by using enrichment factor,geoaccumulation index and statistical analyses[J].Environmental Monitoring and Assessment,2009,152(1/4):309-317.
[8]CHEN J B,GAILLARDET J,BOUCHEZ J,et al.Anthropophile elements in river sediments:Overview from the Seine River,France[J].Geochemistry,Geophysics,Geosystems,2014,15(11):4526-4546.
[9]ZAHRA A,HASHMI M Z,MALIK R N,et al.Enrichment and geo-accumulation of heavy metals and risk assessment of sediments of the Kurang Nallah-feeding tributary of the Rawal Lake Reservoir,Pakistan[J].Science of the Total Environment,2014,470/471:925-933.
[10]KOITER A J,OWENS P N,PETTICREW E L,et al.The behavioural characteristics of sediment properties and their implications for sediment fingerprinting as an approach for identifying sediment sources in river basins[J].Earth-Science Reviews,2013,125:24-42.
[11]GRYGAR T M,POPELKA J.Revisiting geochemical methods of distinguishing natural concentrations and pollution by risk elements in fluvial sediments[J].Journal of Geochemical Exploration,2016,170:39-57.
[12]BLASER P,ZIMMERMANN S,LUSTER J,et al.Critical examination of trace element enrichments and depletions in soils:As,Cr,Cu,Ni,Pb,and Zn in Swiss forest soils[J].Science of the Total Environment,2000,249(1/3):257-280.
[13]VAROL M,SEN B.Assessment of nutrient and heavy metal contamination in surface water and sediments of the upper Tigris River,Turkey[J].Catena,2012,92:1-10.
[14]SAKAN S,DEVI G,RELI D,et al.Evaluation of sediment contamination with heavy metals:The importance of determining appropriate background content and suitable element for normalization[J].Environmental Geochemistry and Health,2015,37(1):97-113.
[15]TAPIA J,AUDRY S,TOWNLEY B,et al.Geochemical background,baseline and origin of contaminants from sediments in the mining-impacted Altiplano and Eastern Cordillera of Oruro,Bolivia[J].Geochemistry:Exploration,Environment,Analysis,2012,12(1):3-20.
[16]BáBEK O,GRYGAR T M,FAMERA M,et al.Geochemical background in polluted river sediments:How to separate the effects of sediment provenance and grain size with statistical rigour?[J].Catena,2015,135:240-253.
[17]COVELLI S,FONTOLAN G.Application of a normalization procedure in determining regional geochemical baselines[J].Environmental Geology,1997,30(1/2):34-45.
[18]GRYGAR T M,NOVáKOVáT,BáBEK O,et al.Robust assessment of moderate heavy metal contamination levels in floodplain sediments:A case study on the Jizera River,Czech Republic[J].Science of the Total Environment,2013,452/453:233-245.
[19]MAJEROVáL,GRYGAR T M,ELZNICOVáJ,et al.The differentiation between point and diffuse industrial pollution of the floodplain of the Plou8nice River,Czech Republic[J].Water,Air,&Soil Pollution,2013,224(9):1-20.
[20]VIJVER M G,SPIJKER J,VINK J P M,et al.Determining metal origins and availability in fluvial deposits by analysis of geochemical baselines and solid-solution partitioning measurements and modelling[J].Environmental Pollution,2008,156(3):832-839.
[21]阂育顺,祁士华,张干.珠江广州河段重金属元素的高分辨沉积记录[J].科学通报,2000,45(S1):2802-2805.
[22]GENG J,WANG Y,LUO H.Distribution,sources,and fluxes of heavy metals in the Pearl River Delta,South China[J].Marine Pollution Bulletin,2015,101(2):914-921.
[23]李红玉,赵彦龙,梁永津,等.北江干流沉积物重金属污染生态风险评价[J].广东微量元素科学,2014,21(7):1-5.
[24]谢文平,王少冰,朱新平,等.珠江下游河段沉积物中重金属含量及污染评价[J].环境科学,2012,33(6):1808-1815.
[25]许振成,杨晓云,温勇,等.北江中上游底泥重金属污染及其潜在生态危害评价[J].环境科学,2009,30(11):3262-3268.
[26]吕文英,周树杰,雷颖欣.珠江广州段东朗断面底泥中重金属污染研究[J].环境科学与技术,2009,32(5):183-186.
[27]赖启宏,杜海燕,方敬文,等.珠江三角洲冲积平原土壤镉高含量区形成原因[J].农业环境科学学报,2005,24(4):746-750.
[28]刘子宁,窦磊,张伟.珠江三角洲第四纪沉积物Cd元素的分布特征及成因[J].地质通报,2012,31(1):172-180.
[29]ROUSSEEUW P J.Least median of squares regression[J].Journal of the American Statistical Association,1984,79:871-880.
[30]R Core Team.R:A language and environment for statistical[CP/OL].(2018-04-23)[2018-07-03].https://www.r-project.org/
[31]MAECHLER M,ROUSSEEUW P,CROUX C,et al.robustbase:Basic Robust Statistics R package[CP/OL].(2018-04-25)[2018-07-03]https://cran.r-project.org/web/packages/robustbase
[32]GRYGAR T M,ELZNICOVáJ,BáBEK O,et al.Obtaining isochrones from pollution signals in a fluvial sediment record:Acase study in a uranium-polluted floodplain of the Plou8nice River,Czech Republic[J].Applied Geochemistry,2014,48:1-15.
[33]TUKEY J W.Exploratory Data Analysis[M].Boston:AddisonWesley Publishing Company,1977:39-56.
[34]ROUSSEEUW P J,VAN ZOMEREN B C.Unmasking multivariate outliers and leverage points[J].Journal of the American Statistical Association,1990,85:633-639.
[35]迟清华,鄢明才.应用地球化学元素丰度数据手册[M].北京:地质出版社,2007:92-93.
[36]史长义,梁萌,冯斌.中国水系沉积物39种元素系列背景值[J].地球科学,2008,41(2):234-251.
[37]GALUSZKA A,MIGASZEWSKI Z M.Geochemical background-an environmental perspective[J].Mineralogia,2011,42(1):7-17.
[38]BOUCHEZ J,GAILLARDET J,LANORD C F,et al.Grain size control of river suspended sediment geochemistry:Clues from Amazon River depth profiles[J].Geochemistry,Geophysics,Geosystems,2013,12(3):1-24.
[39]REIMANN C,GARRETT R G.Geochemical background-concept and reality[J].Science of the Total Environment,2005,350(1/3):12-27.
[40]GU Y G,LI Q S,FANG J H,et al.Identification of heavy metal sources in the reclaimed farmland soils of the Pearl River estuary in China using a multivariate geostatistical approach[J].Ecotoxicology and Environmental Safety,2014,105:7-12.
[41]丁小勇,陈来国,张卫东,等.北江沉积物汞污染现状与评价初步研究[J].农业环境科学学报,2010,29(2):357-362.