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

2014年2月2日，美国第三大煤灰泄漏事件发生在北卡罗来纳州伊甸市，杜克能源丹河蒸汽厂27英亩废水池下的排水管道坍塌，将火山灰和数百万加仑受污染的水排放到丹河中。丹河发源于弗吉尼亚州，流入北卡罗来纳州，然后向北流入弗吉尼亚州，八次越过州界。它最终流入罗阿诺克河，然后进入科尔湖，然后是加斯顿湖，最终进入北卡罗来纳州的阿尔贝马尔湾。这些水域是一个使用率很高的娱乐系统，也是从弗吉尼亚州丹维尔到遥远的弗吉尼亚海滩的城市的饮用水来源。火山灰的有毒成分包括各种污染物，包括砷(As)、铅(Pb)、汞(Hg)和硒(Se)等金属以及一系列有机化合物。虽然蓄水中的元素浓度可以超过饮用水标准和水生生物水质标准，但在丹河新的生物地球化学环境中，与灰烬结合的痕量元素的去向却鲜为人知。溶解和形态的变化会增加金属的毒性，从而威胁到野生动物和未来几年的水的可用性。要回答其中一些问题，多学科方法是必要的。这项研究将向政策制定者提供有关燃煤飞灰排放对人类和野生动物构成危害的程度的信息。具体地说，它将讨论从富含灰分的沉积物中继续释放微量元素的程度，以及沉积环境是否会影响这种释放。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邻近程度，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烬对沉积物生物地球化学的影响，因为它与灰烬生成的微量元素的生物有效性和毒性有关。特别强调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了微量元素的释放。据推测，这种情况将发生在煤炭飞灰的情况下。这项研究将侧重于将痕量元素As、Se、Hg和MeHg释放到孔隙水中，作为微量元素迁移、转化和生物有效性的指标。也有人提出，通过与硫的直接相互作用或通过硫化的有机物间接增强微量元素的流动性。这项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迁移的潜在机制。

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.