Trace Metal Levels in Uncontaminated Groundwater of a Coastal Watershed: Importance of Colloidal Forms
详细信息 查看全文
- 作者：Sergio A. Sañ ; udo-Wilhelmy ; Francis K. Rossi ; Henry Bokuniewicz ; and Ronald J. Paulsen
- 刊名：Environmental Science & Technology
- 出版年：2002
- 出版时间：April 1, 2002
- 年：2002
- 卷：36
- 期：7
- 页码：1435 - 1441
- 全文大小：153K
- 年卷期：v.36,no.7(April 1, 2002)
- ISSN：1520-5851
文摘
Groundwater and surface water were collected usingtrace metal clean techniques from the upper glacialaquifer of West Neck Bay (Shelter Island) in eastern LongIsland, NY, during the late spring and summer of 1999.The collection sites on Shelter Island are located in an areathat is primarily residential and believed to haveuncontaminated groundwater. Ultrafiltration was used to size-fractionate the dissolved (<0.45 
m) fraction into colloidal(1 kDa - 0.45 m) and low molecular weight (<1 kDa)size pools. These fractions were analyzed for trace metals(Al, Ag, Cd, Cu, Mn, Pb, and Zn), organic carbon, andinorganic nutrients (NH4, NO3, PO4). The levels of metalsand organic carbon in the groundwater were as low as thosefound in the open ocean, far removed from anthropogenicinputs. These findings corroborate the need to applytrace metal clean techniques in the determination of metallevels in uncontaminated groundwater. A significantfraction of dissolved metals (22-96%) and organic carbon(~40%) in the groundwater and in surface waters of theBay was found to be associated with colloids. The significanceof the metal association with the colloidal fractiondecreased in the order of Al > Cu > Ag > Zn = Cd =Mn and appeared to be dependent on the affinities of thesemetals for humic substances. In contrast, NO3 and NH4were found to be almost entirely (~98-99%) in the lowmolecular weight size fraction. Metal/aluminum and metal/carbon ratios measured in the colloids were similar tothose reported for humic substances and significantly differentfrom those of soils. This suggests that colloidal particlesmight originate from humic materials as opposed to purelyinorganic minerals. These results indicate the need toconsider the colloidal fraction in the fate and mobility ofmetals in groundwater and that, despite the low levels oforganic matter (<50 M of DOC) measured in groundwater,some groundwater colloids appear to be organic innature.
m) fraction into colloidal(1 kDa - 0.45 m) and low molecular weight (<1 kDa)size pools. These fractions were analyzed for trace metals(Al, Ag, Cd, Cu, Mn, Pb, and Zn), organic carbon, andinorganic nutrients (NH4, NO3, PO4). The levels of metalsand organic carbon in the groundwater were as low as thosefound in the open ocean, far removed from anthropogenicinputs. These findings corroborate the need to applytrace metal clean techniques in the determination of metallevels in uncontaminated groundwater. A significantfraction of dissolved metals (22-96%) and organic carbon(~40%) in the groundwater and in surface waters of theBay was found to be associated with colloids. The significanceof the metal association with the colloidal fractiondecreased in the order of Al > Cu > Ag > Zn = Cd =Mn and appeared to be dependent on the affinities of thesemetals for humic substances. In contrast, NO3 and NH4were found to be almost entirely (~98-99%) in the lowmolecular weight size fraction. Metal/aluminum and metal/carbon ratios measured in the colloids were similar tothose reported for humic substances and significantly differentfrom those of soils. This suggests that colloidal particlesmight originate from humic materials as opposed to purelyinorganic minerals. These results indicate the need toconsider the colloidal fraction in the fate and mobility ofmetals in groundwater and that, despite the low levels oforganic matter (<50 M of DOC) measured in groundwater,some groundwater colloids appear to be organic innature.