Mercury–organic matter relationships in pre-pollution sediments of thermokarst lakes from the Mackenzie River Delta, Canada: the role of depositional environment
Mercury–organic matter relationships in pre-pollution sediments of thermokarst lakes from the Mackenzie River Delta, Canada: the role of depositional environment
复制标题
加拿大马更些河三角洲热岩溶湖污染前沉积物中汞与有机物的关系：沉积环境的作用
作者：
H. Sanei;P. Outridge;A. Dallimore;P. Hamilton
本研究探讨了有机物（OM）的历史变化的影响，从两个密切位于加拿大北极湖泊沉积物中的汞，汞污染输入的到来之前。由于麦肯齐河三角洲在过去的1-3千年里景观的变化，湖泊提供了明显不同的有机物来源、类型和水产生产力程度的历史（即，沉积环境）。它们在1900年前的汞浓度分布图上也有很大不同。当来自水生来源（硅藻和其他单细胞藻类）的不稳定的干酪根样碳（“S2”）在公元750年至1900年之间在生产力更高的湖泊（内湖）中增加时，汞浓度也增加了约1000。百分之五十相比之下，S2的碳浓度在附近的有机贫湖（大湖）几倍低于在Nescalus和减少在过去的千年，而汞浓度没有表现出任何趋势，可能反映了稳定输入的碎屑物质从苔原土壤。湖泊之间的对比表明，OM来自单细胞藻类是更有效地清除汞比OM从陆生植物或水生植物，可能是因为较高的含量不稳定，富硫化合物，高颗粒表面积和其分散在整个水体。结果表明，在人为汞输入的情况下，增加浮游植物的生产力和汞清除单独可以导致显着增加湖泊沉积物中的汞含量。这一发现与以下假设相一致，即由于世纪气候变暖，湖泊生产力增加，混淆了对北方湖泊沉积物中汞含量最近增加的解释，认为这是人为汞沉积造成的。这项研究还表明，沉积物TOC本身是一个穷人，有时误导性的指标，可能会发生变化的来源和质量的OM在水生系统中，这可能会对沉积物中的汞浓度产生重大影响。
This study investigates the influence of organic matter (OM) on the historical variations of Hg in sediments from two closely-situated Canadian Arctic lakes, prior to the advent of Hg pollution inputs. Because of variable landscape evolution in the Mackenzie River Delta over the past 1–3 millennia, the lakes provide distinctly different histories of OM sources, types, and degree of aquatic productivity (i.e., depositional environments). They also differ significantly in their pre-1900 Hg concentration profiles. When labile, kerogen-like carbon (“S2”) from aquatic sources (diatoms and other unicellular algae) increased between 750 and 1900 A.D. in the more productive lake (Nesbitt), Hg concentrations also increased by ca. 50%. In contrast, S2 carbon concentrations in the nearby organic-poor lake (Big Lake) were several-times lower than in Nesbitt and decreased over the past millennium, while Hg concentrations showed no trend probably reflecting the stable input of clastic material from tundra soils. The contrast between lakes suggests that OM derived from unicellular algae is more effective at scavenging Hg than OM from terrestrial plants or aquatic macrophytes, possibly because of a higher content of labile, sulphur-rich compounds, high particle surface area and its dispersion throughout the water column. The results indicate that, in the absence of anthropogenic Hg inputs, increasing phytoplankton productivity and Hg scavenging alone can lead to significant increases in the Hg content of lake sediments. This finding is consistent with the hypothesis that increasing lake productivity because of climate warming during the twentieth century has confounded the interpretation of recently increasing Hg levels in northern lake sediments as being unequivocally due to anthropogenic Hg deposition. This study also suggests that sedimentary TOC by itself is a poor and sometimes misleading indicator of possible changes in the source and quality of OM in aquatic systems, which can have a major impact on Hg concentrations in sediments.