Moir Katherine E, Windle Matthew J S, Cumming Brian F, Ridal Jeffrey J
Paleoecological Environmental Assessment and Research Laboratory, Queen's University, Kingston, Ontario, Canada.
St. Lawrence River Institute of Environmental Sciences, Cornwall, Ontario, Canada.
Environ Toxicol Chem. 2021 Jun;40(6):1788-1799. doi: 10.1002/etc.5009. Epub 2021 Apr 6.
The St. Lawrence River at Cornwall, Ontario, Canada, received substantial inputs of mercury from local, shoreline-based industries through much of the 20th century. Although emission controls were implemented in the late 20th century to reduce the influx of mercury and other metals entering the river, legacy contamination of riverine sediments continues to be a concern. Monitored natural recovery was prescribed in 2005 to remediate contaminated sediments; however, few surveys have been undertaken to examine its effectiveness on shallow, nearshore sediments in contaminated areas. Surface sediments were collected at shallow, nearshore sites in contaminated zones and upstream reference areas to evaluate the current state of sedimentary contamination of mercury and other metals. A Getis-Ord Gi* "hot spot" analysis was employed to assess the spatial distribution of contaminants. In addition, 3 sediment cores were collected from contaminated zones and dated using radioisotopes ( Pb) to assess sedimentation patterns over time. Results indicated that surface sediments from contaminated zones remained elevated in mercury relative to reference sites but spatial distribution of contaminants was highly heterogeneous. Dated sediment cores suggested that sedimentation was not occurring consistently across all areas; variable sedimentation and resuspension patterns over small spatial scales were likely factors driving heterogeneous sedimentary contamination. Such patterns complicate remediation strategies because unburied sediments may serve as continuing sources of contaminants to the ecosystem. Environ Toxicol Chem 2021;40:1788-1799. © 2021 SETAC.
在20世纪的大部分时间里，加拿大安大略省康沃尔的圣劳伦斯河从当地沿岸工业接收了大量汞输入。尽管在20世纪后期实施了排放控制以减少进入河流的汞和其他金属的流入，但河流沉积物的遗留污染仍然令人担忧。2005年规定进行监测自然恢复以修复受污染的沉积物；然而，很少有调查来检验其对污染区域浅海近岸沉积物的有效性。在污染区和上游参考区域的浅海近岸地点采集表层沉积物，以评估汞和其他金属的沉积污染现状。采用Getis-Ord Gi*“热点”分析来评估污染物的空间分布。此外，从污染区采集了3个沉积岩芯，并使用放射性同位素（铅）进行年代测定，以评估随时间的沉积模式。结果表明，污染区的表层沉积物汞含量相对于参考地点仍然较高，但污染物的空间分布高度不均匀。有年代测定的沉积岩芯表明，并非所有区域都持续发生沉积；小空间尺度上可变的沉积和再悬浮模式可能是导致沉积污染不均匀的因素。这种模式使修复策略复杂化，因为未掩埋的沉积物可能继续作为生态系统污染物的来源。《环境毒理学与化学》2021年；40:1788 - 1799。© 2021 SETAC。
