Advances in Environmental Research, Vol. 2, No. 2 (2013) 81-98 DOI: http://dx.doi.org/10.12989/aer.2013.2.2.081 81 Copyright © 2013 Techno-Press, Ltd. http://www.techno-press.org/?journal=aer&subpage=7 ISSN: 2234-1722 (Print), 2234-1730 (Online) The influence of anthropogenic disturbances and watershed morphological characteristics on Hg dynamics in Northern Quebec large boreal lakes M. Moingt 1 , M. Lucotte 1 , S. Paquet 1 and J.-S. Beaulne 2 1 GEOTOP-UQAM, Institut des Sciences de l’Environnement, Montreal, Canada 2 Ecole Centrale de Lyon, Environmental Microbial Genomics Group, Lyon, France (Received October 23, 2012, Revised March 06, 2013, Accepted March 15, 2013) Abstract. Mercury (Hg) dynamics in the boreal environment have been a subject of concern in recent decades, due to the exposure of local populations to the contaminant. Land use, because of its impact on mercury inputs, has been highlighted as a key player in the sources and eventual concentrations of the heavy metal. In order to evaluate the impact of watershed disturbances on Hg dynamics in frequently fished, large boreal lakes, we studied sediment cores retrieved at the focal point of eight large lakes of Québec (Canada), six with watersheds affected by land uses such as logging and/or mining, and two with pristine watersheds, considered as reference lakes. Using a Geographical Information System (GIS), we correlated the recent evolution of land uses (e.g., logging and mining activities) and morphological characteristics of the watershed (e.g., mean slope of the drainage area, vegetation cover) to total Hg concentrations (THg) in sedimentary records. In each core, THg gradually increased over recent years with maximum values between 70 and 370 ng/g, the lowest mercury concentrations corresponding to the pristine lake cores. The Hg Anthropogenic Sedimentary Enrichment Factor (ASEF) values range from 2 to 15. Surprisingly, we noticed that the presence of intense land uses in the watershed does not necessarily correspond to noticeable increases of THg in lake sediments, beyond the normal increment that can be attributed to Hg atmospheric deposition since the beginning of the industrial era. Rather, the terrestrial Hg inputs of boreal lakes appear to be influenced by watershed characteristics such as mean slopes and vegetation cover. Keywords: Hg; boreal forest; lake sediments; organic matter; GIS approach 1. Introduction Mercury (Hg) dynamics in boreal lakes are an ongoing topic of serious concern, as human populations are exposed to the contaminant through fish consumption. Natural sources, including re-emissions from top soil and vegetation as well as volatilization from water surfaces and volcanoes, represent more than half of total Hg emissions in the global atmospheric mercury Corresponding author, Ph.D., E-mail: matthieumoingt@yahoo.fr a Professor b Associate Professor