(SGER) Collaborative Research: Transport and Fate of Mercury Within the Carson River Valley During the January 1997 Flood

9714150米勒对康斯托克矿脉的开采（1860-1890）导致约7500吨汞释放到卡森河系统，包括Lahontan水库。许多受污染的沉积物与填满的古河道有关，这些古河道被认为是由先前与主河道切断的废弃曲流填满而形成的。鉴于目前卡森河中的大部分汞负荷来自河岸侵蚀，因此，在洪水期间，大部分被侵蚀的沉积物通过废弃曲流河道内沉积物的沉积而重新储存起来。因此，在淹没谷底的洪水事件中，河道和山谷填充物之间可能存在污染碎屑的循环。1997年1月初，洪水淹没了卡森河谷的大片地区，其规模在过去57年的记录中只出现过一次。在事件发生期间和之后进行的实地观察显示，水道沿线的许多河段遭受了广泛的侵蚀，而厚厚的沉积序列沉积在谷底的其他地区。根据这些实地观察，我们认为这一低频率、高震级的事件对沿卡森河谷的汞污染颗粒的运输和储存产生了重大影响。本研究的主要目的是：(1)记录1997年1月洪水期间沿卡森河谷从卡森市到拉洪坦水库的侵蚀和沉积模式；(2)确定新形成的洪水沉积物中汞浓度的空间变化；(3)评估污染沉积物沉积和沉积物中汞分布的主要控制因素。通过将这次调查得出的结论与之前对卡森河的研究相结合，我们将能够评估从单个洪水事件到几十年的时间内汞通过物理过程的运输和命运。此外，对风暴前后测量的地理趋势进行比较，将对罕见的、高强度的洪水对冲积沉积物中重金属扩散的重要性产生重要的见解。

9714150 Miller Mining of the Comstock Lode (1860-1890) resulted in the release of an estimated 7,500 tons of mercury to the Carson River system including Lahontan Reservoir. Much of the polluted sediment is associated with filled paleochannels which are thought to have been produced by the filling of abandoned meanders previously cutoff from the main channel. Given that a majority of the present day mercury load in the Carson River is derived from bank erosion, it follows that during floods, much of the eroded sediment is returned to storage by the deposition of sediment within the channels of the abandoned meanders. Thus, there may be a cycling of contaminated debris between the channel and the valley fill during flood events which inundated the valley floor. In early January, 1997 flood flows, with a magnitude which has only been exceeded once in the past 57 years of record, inundated large regions of the Carson River valley. Field observations made during and following the event revealed that numerous reaches along the channel suffered extensive erosion, while thick sedimentary sequences were deposited over other regions of the valley floor. Based on these field observations, we believe that this low frequency, high magnitude event had a significant affect on the transport and storage of mercury contaminated particles along the Carson River valley. The primary objectives of this investigation are to (1) document the patterns of erosion and deposition that occurred along the Carson River valley from Carson City to Lahontan Reservoir during the January, 1997 flood, (2)determine the spatial variations in mercury concentration that occur within the newly formed flood deposits, and (3) assess the primary controls on both the deposition of contaminated sediments and the distribution of mercury within those deposits. By combining the conclusions reached in this investigation with previous studies of the Carson River, we will be able to assess the transport and fate of mercury by phys ical processes over time periods ranging from individual flood events to decades. In addition, a comparison of the geographic trends measured prior to and following the storm will lead to significant insights into the importance of rare, high magnitude floods on the dispersal of heavy metals in alluvial deposits.