Mercury in lake sediment cores of eastern and northern Canada

Recent and historical deposition of mercury (Hg) are examined over a broad geographic area from southwestern Northwest Territories to Labrador and from the U.S. Northeast to northern Ellesmere Island using dated sediment cores from 50 lakes (18 in midlatitudes (41-50 degrees North), 14 subarctic (51-64 degrees North) and 18 in the Arctic (65-83 degrees North)). Objectives were to quantify latitudinal and longitudinal trends of anthropogenic mercury deposition in eastern and northern North America, to investigate variations in mercury deposition, to examine relationships with lake area, catchment/lake area ratio and sedimentation rates, and to compare results with model predictions.

Distinct increases of mercury over time were observed in 76% of Arctic, 86% of subarctic and 100% of midlatitude cores. Subsurface maxima in mercury depositional fluxes were observed in only 28% of midlatitude lakes and 18% of arctic lakes, indicating little recent reduction of inputs. Anthropogenic mercury fluxes adjusted for sediment focusing and changes in sedimentation rates were negatively correlated with latitude. The latitudinal trend for anthropogenic mercury fluxes adjusted for sediment focusing and changes in sedimentation rates values showed excellent agreement with predictions of the global/regional atmospheric heavy metal (mercury) model (GRAHM) for the geographic location of each lake. The results are consistent with a scenario of slow atmospheric oxidation of mercury, and slow deposition of reactive mercury emissions, declining with increasing latitude away from emission sources in the midlatitudes, and support the view that there are significant anthropogenic mercury inputs in the Arctic.

Supplemental Information

The Northern Contaminants Program (NCP, http://www.science.gc.ca/eic/site/063.nsf/eng/h_7A463DBA.html) was established in 1991 in response to concerns about human exposure to elevated levels of contaminants in wildlife species that are important to the traditional diets of northern Aboriginal peoples. Early studies found a wide variety of substances, many of which had no Arctic or Canadian sources, but which were, nevertheless, reaching unexpectedly high levels in the Arctic ecosystem.

The Canadian Cryospheric Information Network (CCIN, https://www.ccin.ca/) and the Polar Data Catalogue (PDC, https://polardata.ca/) have been developed over the past two decades through collaborative partnerships between the University of Waterloo and numerous government, university, and private organizations to provide the data and information management infrastructure for the Canadian cryospheric community. The PDC is one of Canada’s primary online sources for data and information about the Arctic and is Canada's National Antarctica Data Centre.

Polar Data Catalogue Canadian Cryospheric Information Network Metadata Record:

https://www.polardata.ca/pdcsearch/PDCSearchDOI.jsp?doi_id=9812

The Northern Ecosystem Initiative ran from 1998 to 2008. It was a national, pan-northern program based on a common, unifying vision, goals and objectives while being flexible and responsive to differing regional needs. This initiative was created to increase the understanding of northern ecosystems and to identify and respond to issues at the local and regional levels.