Aqueous Stability of Gadolinium in Surface Waters Receiving Sewage Treatment Plant Effluent, Boulder Creek, Colorado

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• 作者：Philip L. Verplanck ; Howard E. Taylor ; D. Kirk Nordstrom ; and Larry B. Barber
• 刊名：Environmental Science & Technology
• 出版年：2005
• 出版时间：September 15, 2005
• 年：2005
• 卷：39
• 期：18
• 页码：6923 - 6929
• 全文大小：155K
• 年卷期：v.39,no.18(September 15, 2005)
• ISSN：1520-5851

文摘

In many surface waters, sewage treatment plant (STP)effluent is a substantial source of both regulated andunregulated contaminants, including a suite of complexorganic compounds derived from household chemicals,pharmaceuticals, and industrial and medical byproducts.In addition, STP effluents in some urban areas have alsobeen shown to have a positive gadolinium (Gd) anomaly inthe rare earth element (REE) pattern, with the Gd derivedfrom its use in medical facilities. REE concentrationsare relatively easy to measure compared to many organicwastewater compounds and may provide a more widelyutilized tracer of STP effluents. To evaluate whether sewagetreatment plant-associated Gd is a useful tracer oftreatment plant effluent, an investigation of the occurrence,fate, and transport of rare earth elements was undertaken.The rare earth element patterns of four of five STPeffluents sampled display positive Gd anomalies. The onesite that did not have a Gd anomaly serves a smallcommunity, population 1200, with no medical facilities.Biosolids from a large metropolitan STP are not enrichedin Gd even though the effluent is, suggesting that asubstantial fraction of Gd remains in the aqueous phasethrough routine treatment plant operation. To evaluate whetherSTP-derived Gd persists in the fluvial environment, a 14-km study reach downstream of an STP was sampled.Gadolinium anomalies were present at all five downstreamsites, but the magnitude of the anomaly decreased.Effluent from STPs is a complex mixture of organic andinorganic constituents, and to better understand the chemicalinteractions and their effect on REEs, the aqueousspeciation was modeled using comprehensive chemicalanalyses of water samples collected downstream of STPinput. These calculations suggest that the REEs will likelyremain dissolved because phosphate and carbonatecomplexes dominate over free REE ions. This study supportsthe application of Gd anomalies as a useful tracer ofurban wastewater.