RAPID: Trace Element Cycling in Dan River Sediments following Coal Fly Ash Release

2014年2月2日，全国第三大煤灰泄漏事件发生在北卡罗来纳州的伊甸园，一个占地27英亩的杜克能源丹河蒸汽厂废水池下的排水管倒塌，将煤灰和数百万加仑的污染水排入丹河。丹河发源于弗吉尼亚州，流入北卡罗来纳州，然后向北流回弗吉尼亚州，穿越州界八次。 它最终流入罗阿诺克河，进入克尔湖，然后加斯顿湖，最终进入Albemarle Sound，NC。 沃茨是一个高度使用的娱乐系统，也是从弗吉尼亚州丹维尔到远至弗吉尼亚海滩的城市的饮用水来源。煤灰的有毒成分包括从金属如砷（As）、铅（Pb）、汞（Hg）到硒（Se）的各种污染物沿着一系列有机化合物。虽然蓄水池中的元素浓度可能超过饮用水标准和水生生物水质标准，但在丹河新的地球化学环境中，与灰分结合的微量元素的命运却知之甚少。溶解和形态的变化会增加金属毒性，从而威胁野生生物和水的可用性多年来。要回答其中的一些问题，需要采取多学科的方法。这项研究将为政策制定者提供有关粉煤灰释放对人类和野生动物造成危害的程度的信息。具体而言，它将解决微量元素继续从富含灰分的沉积物中释放的程度，以及沉积环境是否影响这种释放。这项研究将有助于确定是否有必要清除沉积物，并根据沉积环境和与关注目标的接近程度（如饮用水取水口和河流渔业和娱乐用途的敏感区域）确定任何清除工作的优先顺序。这项拟议的研究旨在评估灰对沉积物生物地球化学的影响，因为它涉及灰中微量元素的生物利用度和毒性。特别强调的是沉积物的氧化还原条件，因为这会影响沉积物中的金属形态和流动性。据了解，沉积物中缺氧条件的发展通过形态变化促进微量元素的释放。假设这将发生在粉煤灰的情况下。研究将侧重于微量元素As、Se、Hg和MeHg向孔隙水的释放，作为微量元素流动性、转化和生物有效性的指标。也有人提出，微量元素的流动性是通过与硫的直接相互作用或通过硫化有机物间接增强的。本研究将调查沉积物孔隙水中DOM的硫化程度，以评估这是否是微量元素动员和运输的潜在机制。

1439743HeyesOn February 2, 2014, the third-largest coal ash spill in the Nation occurred at Eden, North Carolina where a drainage pipe under a 27-acre Duke Energy Dan River Steam Plant waste pond collapsed, discharging coal ash and millions of gallons of contaminated water into the Dan River. The Dan River originates in Virginia and flows into North Carolina and then flows north back into Virginia crossing the state lines eight times. It eventually flows into the Roanoke River, and into Lake Kerr then Lake Gaston and eventually into the Albemarle Sound, NC. The waters serve as a highly used recreation system and as a source of drinking water for cities from Danville, VA to as far away as Virginia Beach. The toxic constituents of coal ash include various contaminants from metals such as arsenic (As), lead (Pb), mercury (Hg) to selenium (Se) along with a suite of organic compounds. While the element concentrations in impoundment water can exceed drinking water criteria and aquatic life water quality criteria, less is known about the fate of trace elements bound to ash in the new biogeochemical environment of the Dan River. Dissolution and changes in speciation can increase metal toxicity thus threaten wild life and water usability for years to come. To answer some of these questions a multidisciplinary approach is necessary. This study will provide information to policy makers on the extent to which coal fly ash releases present a hazard to humans and wildlife. Specifically it will address the extent to which trace elements continue to be released from ash enriched sediments and if the depositional environment influences such release. This research will help determine if sediment removal is warranted and to prioritize any removal efforts based on the environment of deposition and proximity to targets of concern such as drinking water intakes and sensitive areas for the rivers fishery and recreational use.This proposed research seeks to assess the impact of ash on sediment biogeochemistry as it pertains to the bioavailability and toxicity of ash born trace elements. Particular emphasis is placed on the sediment redox condition as this impacts metal speciation and mobility in sediments. It is understood that development of anoxic conditions in sediments promotes the release of trace elements through changes in speciation. It is hypothesized this will occur in the case of coal fly ash. The research will focus on the release of trace elements As, Se, Hg and MeHg to porewater as indicators of trace element mobility, transformation and bioavailability. It has also been proposed that trace element mobility is enhanced through a direct interaction with sulfur or indirectly through sulfurized organic matter. The research will investigate the degree of sulfurization of DOM in sediment porewater to assess if this is a potential mechanism for trace element mobilization and transport.