NOAA, National Centers for Coastal Ocean Science, Center for Coastal Monitoring and Assessment, N/SCI 1, SSMC4, 9110, 1305 East West Hwy, Silver Spring, MD 20910, USA.
Sci Total Environ. 2010 Apr 1;408(9):2096-108. doi: 10.1016/j.scitotenv.2010.01.006. Epub 2010 Feb 20.
Restoration of the Chesapeake Bay, the largest estuary in the United States, is a national priority. Documentation of progress of this restoration effort is needed. A study was conducted to examine water quality in the Choptank River estuary, a tributary of the Chesapeake Bay that since 1998 has been classified as impaired waters under the Federal Clean Water Act. Multiple water quality parameters (salinity, temperature, dissolved oxygen, chlorophyll a) and analyte concentrations (nutrients, herbicide and herbicide degradation products, arsenic, and copper) were measured at seven sampling stations in the Choptank River estuary. Samples were collected under base flow conditions in the basin on thirteen dates between March 2005 and April 2008. As commonly observed, results indicate that agriculture is a primary source of nitrate in the estuary and that both agriculture and wastewater treatment plants are important sources of phosphorus. Concentrations of copper in the lower estuary consistently exceeded both chronic and acute water quality criteria, possibly due to use of copper in antifouling boat paint. Concentrations of copper in the upstream watersheds were low, indicating that agriculture is not a significant source of copper loading to the estuary. Concentrations of herbicides (atrazine, simazine, and metolachlor) peaked during early-summer, indicating a rapid surface-transport delivery pathway from agricultural areas, while their degradation products (CIAT, CEAT, MESA, and MOA) appeared to be delivered via groundwater transport. Some in-river processing of CEAT occurred, whereas MESA was conservative. Observed concentrations of herbicide residues did not approach established levels of concern for aquatic organisms. Results of this study highlight the importance of continued implementation of best management practices to improve water quality in the estuary. This work provides a baseline against which to compare future changes in water quality and may be used to design future monitoring programs needed to assess restoration strategy efficacy.
恢复切萨皮克湾，美国最大的河口，是国家的当务之急。需要记录这一恢复努力的进展情况。本研究旨在检查切萨皮克湾支流乔普坦克河口的水质，自 1998 年以来，该河口一直被《联邦清洁水法》归类为受损水域。在乔普坦克河口的七个采样站测量了多个水质参数（盐度、温度、溶解氧、叶绿素 a）和分析物浓度（养分、除草剂和除草剂降解产物、砷和铜）。在 2005 年 3 月至 2008 年 4 月的 13 天里，在流域的基流条件下采集了样本。结果表明，农业是河口硝酸盐的主要来源，农业和污水处理厂都是磷的重要来源。河口下游的铜浓度一直超过慢性和急性水质标准，这可能是由于船用防污漆中使用了铜。上游流域的铜浓度较低，表明农业不是铜向河口的主要污染源。除草剂（莠去津、西玛津和甲草胺）的浓度在夏初达到峰值，表明其从农业区迅速通过地表传输进入河道，而其降解产物（CIAT、CEAT、MESA 和 MOA）似乎通过地下水输送。CEAT 在河中有一定的降解，而 MESA 则保持稳定。观察到的除草剂残留浓度没有达到水生生物关注的既定水平。本研究结果强调了继续实施最佳管理实践以改善河口水质的重要性。这项工作为未来水质变化提供了一个基准，并可用于设计未来的监测计划，以评估恢复策略的效果。
