摘要
长江口滨岸带是一个特殊的开放系统。长江径流和河口区潮波系统在这里汇合,潮波流水动力作用强烈,泥沙输移和物质交换频繁,各物理要素(悬浮颗粒含量、流速等)和化学要素(盐度、溶氧、pH、Eh等)梯度变化剧烈,生物地球化学作用非常复杂,物理化学要素梯度变化大、生物种类丰富多样。然而长期以来,长江口滨岸带由于其特殊的地理位置,以及气候、水文、人类活动多要素的高强度耦合作用影响,汞污染形势严峻,生态环境较为脆弱。
本文选取长江口陈行水库及其附近岸段作为典型区域,选取典型有毒重金属汞(Hg)为主要研究对象,分析在潮汐再悬浮及其与pH、盐度等环境条件耦合影响下,沉积物中汞的沉积物-水界面分布、累积、迁移和转化规律。在对大量第一手数据资料进行综合分析的基础上,本文主要得到以下几条结论:
(1)长江口滨岸带已经遭受到较严重的汞污染,尤其是陈行水库地区,上覆水汞含量达到0.159μg/L,超过国家地表水Ⅲ类水标准50%以上,沉积物中汞累积量达到0.133μg/g,是长江口长江口沉积物底质标准0.027μg/g的4.93倍,对水源地取水造成了严重隐患。
(2)潮汐扰动导致表层沉积物发生再悬浮,水体理化性质也发生周期性变化。一方面,水体氧化还原电位和盐度升高,有利于原本沉降的汞的溶出和释放;而另一方面,水体pH和悬浮颗粒物浓度升高,使水体环境总体向有利于汞的吸附沉降的方向演化。因此,再悬浮过程中汞的释放和沉降,是各种环境条件耦合作用的综合结果。
(3)潮汐再悬浮过程中,潮汐动力扰动和颗粒物表面吸附-解析过程是控制汞再悬浮迁移转化的主导过程。在较强潮汐动力扰动下,沉积物发生再悬浮,原本沉降的汞将向上覆水发生再悬浮释放;同时在较强动力扰动下,颗粒物表面吸附的汞可以解析进入水体。这是造成水体可溶态汞含量升高的两个主要原因。而在在动力较弱时,通过对水体可溶态汞的捕集吸附及重力沉降,颗粒物表现为对水体可溶汞的去除,并最终回到表层沉积物。长江口沉积物总体上仍是汞的汇。
(4)水动力强度、pH、盐度是影响颗粒物表面吸附-解析平衡的主要环境因素。较强水动力条件有利于颗粒物表面汞的解析;较高的pH(>8.5)、盐度(>1.5‰)环境有利于颗粒物絮凝沉降,从而表现为对上覆水可溶汞的去除。
(5)再悬浮底泥扰动对水体的直接影响有一个范围,对上覆水影响上界大致在距沉积物-水界面100cm处,其上部近表层水体汞的交换是一个相对独立的体系;其沉积物影响的下界大约在4-5cm深度左右。
The intertidal flat of coastal areas of the Yangtze estuary is a complex-open ecosystem influenced both by natural factors and strong human activities.The runoff and tide meet here,making acuity disturbing to transport and transfer of sand and suspensions.Parameters here,both Physical and Chemical change quite often.So its biochemistry process is very complexible,and biata is very sensitive and frailty. However,the environment of Yangtze estuary is suffering serious pollution of mercury because of its special geography position and gathering of climate, hydrography and human activities.
So here,we choose Henhang wellspring as typical case of sampling profile,in order to study Transfer and Transform of Mercury during Resuspension under Dynamic Disturbing,concerning affection of pH,salinity,and dynamics.We conclude under firsthand datas as follow:
1) The tideflat of Yangtze estuary has suffered serious mercury pollution especially at Chenhang wellspring.The mercury in water reaches 0.159μg/L,50% overtoil to National Standard ofⅢsurface water;and 0.133μg/g in sediment,4.93 times more than Standard of sediment of Yangtze river.The environment condition makes much risk to drinking water.
2) The resuspension in surface sediment deal to tide disturbing drives periodical fluctuation of water characteristics.On the one hand,the rising of Eh and salinity intensify the release and disadsorption of mercury;on the other hand,the pH and TSS climb up,making it benefits the adsorption and deposition of mercury.So it's the compositive result of release and deposition of mercury,by coupling action of all environmental factors.
3) Tide disturbing and adsorbtion-disadsorbtion on TSS are two factors controlling transfer and transport of mercury.Under strong disturbing,the mercury would release from surface sediment for resuspension,and particle mercury would also dissolve into water.That will make high concentration of dissolved mercury. However,TSS would adsorb mercury while dynamics change weaker,and mercury would back to sediment through deposition of suspending particles.
4) Dyamics,pH and salinity can affect adsorbtion-disadsorbtion balance upon suspending particles.Strong dynamics,high pH(>8.5) and salinity(>1.5) would advance deposition of particle,benefit for wipping off dissolved mercury.
5) There are boundaries for resuspension,which arranging 100cm depth in water,and 4-5cm in sediment from sediment-water counterface.
引文
陈吉余,杨启伦.1988.上海市海岸带和海涂资源综合调查报告[M].上海:科学技术出版社.
陈业材.环境汞的来源与迁移转化规律的研究[J].矿物岩石地球化学通报,1994,3:135-137.
陈振楼,许世远,柳林等.2000.上海滨岸潮滩沉积物重金属元素的空间分布与累积[J].地理学报.55(6),641-651.
程金平,刘晓洁,冀秀玲等.总汞、甲基汞和硒在汞暴露大鼠脑、肝、肾中的分布[J].中国环境科学,2006,26(3):376-379.
丁振华,刘彩娥,汤庆合等.长江口及邻近海域环境污染研究的必要性——以汞污染为例[J].长江流域资源与环境,2005a,14(2):204-207.
丁振华,王文华,刘彩娥等.黄浦江江水和沉积物中汞的分布和形态特征[J].环境科学,2005b,26(5):62-66.
丁振华,王文华,庄敏.汞的界面地球化学研究进展[J].海洋科学,2005c,29(10):54-64.
樊安德,杨晓兰,应时理.长江口及其邻近海区的重金属元素[J].东海海洋,1995,13(3-4):37-74.
方子云,邹家祥.长江地区环境对策与可持续发展[M].武汉:武汉出版社,1999.
冯新斌,洪业汤.酸沉降对人类的威胁之一:引起湖泊体系鱼体汞污染[J].地质地球化学,1996,(5):50-53.
郭建青,钱碧华,党爱翠等.厦门九龙江河口区海水中溶解和颗粒态Cu、Pb、Cd的地球化学行为[J].厦门大学学报,2007,46(1):54-61.
黄奕龙,王仰麟,谭启宇等.城市饮用水源地水环境健康风险评价及风险管理[J].地学前缘,2006,13(3):162-167.
李鱼,刘亮,董德明等.城市河流淤泥中重金属释放规律的研究[J].水土保持学报,2003,17(1):125-127.
刘先利,刘彬,邓南圣.环境内分泌干扰物研究进展[J].上海环境科学,2003,22:57-64.
陆敏,张卫国,师育新等.太湖北部沉积物金属和营养元素的垂向变化及其影响因素[J].湖泊科学,2003,15(3):213-220.
茅志昌,潘定安,沈焕庭.长江河口悬沙的运动方式与沉积形态特征分析[J].地理研究,2001,20(2):170-177.
钱家忠,李如忠,汪家权等.城市供水水源地水质健康风险评价[J].水利学报,2004,8:90-93.
邵秘华,王正方.长江口海域悬浮颗粒物中铜、铅、镉的化学形态及分布特征研究[J].海洋与湖沼,1992,23(2):144-149.
沈焕庭等.长江河口物质通量[M].北京:海洋出版社,2001:30-31.
孙树青,胡国华,王勇泽等.湘江干流水环境健康风险评价[J].安全与环境学报,2006,6(2):12-15.
许世远.长江三角洲地区风暴潮沉积研究[M].北京:科学出版社,1997.
闫鹏,于梅,张姝.我国部分城镇饮用水源水有机物污染的研究概况[J].中国预防医学杂志,2004,5(1):76-78.
杨建华.对上梅市东旺沙滩涂围垦规划设计的认识与实践[J].上海农业学报,1999,15(3):77-84.
杨陇慧,朱建荣,朱首贤.长江口杭州湾及邻近海区潮汐潮流场三维数值模拟[J].华东师范大学学报,2001(3):74-84.
杨晓兰.长江口悬浮颗粒物的表面特性与重金属的沉降[J].环境污染与防治,1999,21(3):36-38.
杨世伦,姚炎明,贺松林.长江口冲积岛岸滩剖面形态和冲淤规律[J].海洋与湖沼,1999,30(6),764-769.
张经.中国河口地球化学研究的若干进展[J].海洋与湖沼,1994,25(4):438-444.
Anakel,A.V.,1995.Towards developing sediment quality assessment guidelines for aquatic systems:an Australian perspective[J].Aust.J.Earth Sci.42,335-369.
Andrew Heyse,Carrie Miller,Robert P.Masom Mercury and methylmercury in Hudson River sediment:impact of tidal resuspension on partitioning and methylation[J].Marine Chemistry,2004(90):75-89.
Aμger N.,Kofman O.,Kosatsky T.,Armstrong B.Low-level Methylmercury Exposure as a Risk Factor for Neurologic Abnormalities in Adults[J].Neuro Toxicology,2005(26):149-157.
Beldowski J,Pempkowiak J.Mercury transformations in marine coastal sediments as derived from mercury concentration and speciation changes along source/sink transport pathway (Southern Baltic)[J].Estuarine,Coastal and Shelf Science,2007,72:370-378.
Billon G,Ouddane B.,Boughriet A.Chemical speciation of sulfur compounds in surface sediments from three bays (Fresnaye,Seine and Authie) in northern France,and identification of some factors controlling their generation[J],Talanta,2001,53:971-981.
Bloom N S,Watras C J,Hurley J P.Impact of acidification on the methylmercury cycle of remote seepage lakes [J].Water air and soil pollution,1991 ,56(4):477-491.
Burdige DJ.The biogeochemistry of manganese and iron reduction in marine sediments.Earth-Science Reviews,1993,35:249-284.
Conrad C F,Chisholm Brause C J.Spatial survey of trace metal contaminants in the sediments of the Elizabeth River,Virginia.Marine Pollution Bulletin[J],2004,49:319-324.
Carapu(?)a H.,Vdlega M.,Pereira E.,et al.Monitoring acid-volatile sulphide by a fast scan voltammetric method:application to mercury contamination studies in salt marsh sediments[J].Analytica Chimica Acta,204,524:127-131.
Chapman,P.,1997.Is Bioaccumulation Useful for Predicting Impacts[J].Marine Pollut.Bull.34 (5),282-283.
Driscoll,C.T,Blette,V.,Yan,C,Schofield,C.L,Munson,R.,Holsapple,J.,1995.
The role of dissolved organic carbon in the chemistry and bioavailability of mercury in remote Adirondack Lakes[J].Water Air Soil Pollut.80,499 - 508.
Eun-Hee Kim,Robert P.Mason,Elka T.Porter,et al.The impact of resuspension on sediment mercury dynamics,and methylmercury production and fate:A mesocosm study[J].Marine Chemistry,2006,102:300-315.
Fang T.,Li X.D.,Zhang G Acid volatile sulfide and simultaneously extracted metals in the sediment cores of the Pearl River Estuary,South China [J].Ecotoxicology and Environmental Safety,2005,61:420-431.
Gambrell LP,Wiesepape JB,Patrick WH,et al.The effects of pH,redox,and salinity on metal release from a contaminated sediment[J].Water,Air and Soil Pollution,1991,57-58:359-367.
Gerritse R G,Wallbrink P J,Murray A S.Accumulation of Phosphorus and Heavy
Metals in the Peel-Harvey Estuary in Western Australia:Results of a Preliminary Study[J].Estuarine,Coastal and Shelf Science,1998,47:679-693.
Grassi S,Netti R.Sea water intrusion and mercury pollution of some coastal aquifers in the province of Grosseto (Southern Tuscany-Italy)[J].Journal of Hydrology,2000,237:198-211.
Haag I,Kern U,Westrich B.Erosion investigation and sediment quality measurements for a comprehensive risk assessment of contaminated aquatic sediments[J].Science of the Total Environment,2001,266:249-257.
Hatje V,Birch GF,Hill DM.Spatial and temporal variability of particulate trace metals in Port Jackson Estuary,Australia[J].Estuarine,Coastal and Shelf Science,2001,53:63-77.
Isabelle S.,Alfonso M.Trace metal remobilization following the resuspension of estuarine sediments:Saguenay Fjord,Canada[J].Applied Geochemistry.2000,15,191-210.
Kim E.,Mason R.,Porter E.,et al.The impact of resuspension on sediment mercury dynamics,and methylmercury production and fate:A mesocosm study [J].MarineChemistry,2006,102:300-315.
Lathrop R C,Rasmussen P M,Kananer D R.Mercury concentrations in walleyes from Wisconsin (USA) Lake [J].Water air and soil pollution,1991,56[4]:295-307.
Latimer JS,Davis WR,Keith DJ.Mobilization of PAHs and PCBs from in-place contaminated marine sediments during simulated resuspension events[J].Estuary,Coastal and Shelf Science,1999,49:577-595.
Lee,C.L.,Fang,M.D.,Hsieh,M.T.,1998.Characterization and distribution of metals in surficial sediments in Southwestern Taiwan[J].Marine Pollut.Bull.36 (6),464 - 471.
Martin J M,Guan D M,Flbaz F,etc.Preliminary assessment of the distributions of some trace elements in a pristine aquatic environment[J].Marine Chemistry,1993,43:185-199.
May,T.W.,Wiedmeyer,R.H.,Brumbaugh,W.G.,Schmitt,C.J.,1997.The determination of metals in sediment pore waters and in 1 N HC1 extracted sediments by ICP-MS[J].At.Spectrosc.18 (5),133 - 139.
Nedwell D.B.and Trimmer M.Nitrogen fluxes through the upper estuary of the Great Ouse,England:the role of the bottom sediments[J].Marine Ecology Progress Series 1996(142):273-286.
Philippe G.Methylmercury toxicity and functional programming [J].Reproductive Toxicology,2007(23):414-420.
Ramalhosa E.,Pato P.,Monterroso P.,Pereira E.,Vale C,Duarte A.C..2006 .
Accumulation versus remobilization of mercury in sediments of a contaminated lagoon[J].Marine Pollut Bull.52,353-356.
Riedel GF,Sanders JG,Osman RW.Biogeochemical control on the flux of trace elements from estuarine sediments:effects of seasonal and short-term hypoxia[J].Marine Environmental Research,1999,47:349-372.
Sanudo-Wilhelm SA.,Rivera-Duarte I,Flegal AR.Distribution of colloidal trace metals in the San Francisco Bay estuary[J].Geochimica et Cosochimica Acta,1996,60:4933-4944.
Simpson S.,Apte S.,Batley G Effect of Short-Term Resuspension Events on Trace Metal Speciation in Polluted Anoxic Sediments [J].Environ.Sci.Technol.,1998,32:620-625.
Turner A,Millward GE,Tyler AO.The distribution and chemical composition of particles in a macrotidal estuary [J].Estuarine,Coastal and Shelf Science,1994,38:1-17.
Turner A.Trace metal contamination in sediments from U.K.estuaries:an empirical valuation of the role of hydrous iron and manganese oxides estuary [J].Estuarine,Coastal and Shelf Science,2000,50:355-371.
Wallmann,K.,Petersen,W.,Reiners,C,Gramm,H.,1996.Trace element diagenesis in polluted sediments of the River Elbe Estuary[D].In:Calmano,W.,Forstner,U.(Eds.),Sediments and Toxic Substances.Springer-Verlag,Berlin,Germany,197-213.
Wanderley R.B.,J.Paulo O.G.Mercury in the environment and riverside population in the Madeira River Basin,Amazon,Brazil[J].Science of the Total Environment,2006,368:344-351.
Whealey B.,Wheatley M.A.Merthylmercury and the health of indigenous peoples:a risk management challenge for physical and social sciences and for public health policy [J].The Science of the Total Environment,2000(259):23-29.
Yang S.L.Sedimentation on a growing intertida island in the Yangtze River mouth[J].Estuarine,Coastal and Shelf Science,1999,49:401-410.
Yin Yunjun.Adsorption of Mercury( Ⅱ) by Soil:Effects of pH,Chloride,and Organic Matter[J].Environ Qual.1996,25(6):837-844.
Zwolsman J J G,Van Eck B T M,Van Der Weijden C H.Geochemistry of dissolved trace metals (Cadmium,Copper,Zinc) in the Scheldt estuary,southwestern Netherlands:Impact of seasonal variability [J].Geochemical Cosmochimica Acta,1997,61(8):1635-1652.
Zwolsman J J G,Eck GTM.Geochemistry of major elements and trace metals in suspended matter of the Scheldt estuary,southwest Netherlands [J].Marine Chemistry,1999,66:91-111.