Base de données de recherche des TNO

étiquettes: physical sciences, water quality, metals, sediment quality, forest fire, peatlands

Objectif(s): To characterize the forest fire history in the study region and test the relationship between fire events and metal accumulation over recent centuries.

Description du projet: The research team will use natural environmental archives (lake sediment and peat cores) to characterize the forest fire history in the study region and test the relationship between fire events and metal accumulation over recent centuries. Study sites will be selected along a gradient of recent forest fire activity with some study sites located in areas of the latest burns (2014-15) to examine the impacts of recent fires on metal accumulation. This study will address the following questions: •What was the timing and frequency of fire events in the North Slave Region, and how does that relate to metal accumulation over the last few centuries? •Did atmospheric deposition rates of metals increase as a result of recent fires in 2014-15? •How does metal deposition by natural processes (forest fires) compare to legacy industrial activity (Giant Mine roasting emissions)? This project will generate important new information on the potentially dominant role of forest fires in metal deposition within the Northwest Territories. The research team will use paleo-environmental approaches to investigate the forest fires impacts on metal deposition to lakes and peatlands. Sediment cores from lakes with small catchments (thus predominately influenced by atmospheric deposition) will be dated and analyzed for macroscopic charcoal fragments to reconstruct forest fire events in recent centuries (last 500 years). These fire histories will then be compared to metal accumulation in the sediment records to test for a relationship between fire events and metal accumulation. Peat cores, which represent a purely atmospheric signal (no catchment inputs), will be collected near the lakes to estimate local atmospheric deposition rates of metals and to act as a control for catchment or lake influences on metal accumulation. A paleo-environmental approach will provide a historical perspective on the significance of fire events for metal deposition over recent centuries and identify impacts from the latest fire events in the region. All sample collection will be conducted in the summer of 2016. A total of 8 lake sediment cores and 4 peat cores will be collected from 5 areas in the North Slave region. Two small lakes will be sampled in each of two areas close to recent burns along Hwy 5 (2014) and the Ingraham Trail (2015). Both areas are also near to earlier fires over the last two decades, making them excellent areas to investigate recent impacts of forest fires on metal deposition. Two sites (Russell Lake, North Arm of Great Slave Lake) will provide information on the response of larger lakes to atmospheric inputs from forest fires. Two small lakes south of Yellowknife on the shoreline of Great Slave Lake (Wool Bay), which are farther from recent forest fires, will provide information on regional deposition patterns. Peat cores will be collected from areas to control for catchment influences and also near Giant Mine (Yellowknife) for comparison with atmospheric deposition from mining emissions. Surface water will be collected from each lake for associated water quality information. Three NWT organizations, the Yellowknives Dene First Nation (YKDFN), the Wek’èezhìi Renewable Resources Board (WRRB), and Tlicho Government are team members on this project to provide guidance on the project’s purpose, design and implementation. For the field program, one of the study areas (Russell Lake) has been chosen to link with the Tlicho Aquatic Ecosystem Monitoring Program, and sampling at that site will provide new information (historical changes in metal accumulation in sediments) that is directly relevant to their on-going water and sediment quality monitoring. In addition, the study area near Wool Bay on Great Slave Lake will provide new information on metal deposition to an important fishing area for the YKDFN. A local guide from Behchoko and Ndilo/Dettah will assist for the field program in each of those study areas, respectively. This project will generate important new findings that will inform community organizations and decision makers on the influence of forest fires on metal deposition to lakes and peatlands in the North Slave Region. The main deliverables for this project will be in the form of reports, meetings, and presentations. The following specific deliverables will result from the project. •NWT Cumulative Impacts Monitoring Program’s (CIMP’s) Annual and Final Reports will be submitted to NWT CIMP and uploaded to the NWT Discovery Portal (progress report - February 2017, final report - April 2018) •Poster or oral presentation at the annual Yellowknife Geoscience Forum (November 2016 and 2017) •Meetings to communicate in person the progress of the study with community organizations, government and other stakeholders (November 2016 and 2017) •A final plain language report that summarizes the main findings for community organizations and decision makers on the influence of forest fires on metal deposition to lakes and peatlands in the North Slave Region (2018). This report will contain water chemistry and sediment chemistry datasets from the study as annexes to the report. The fieldwork for this study will be conducted from June 15, 2016 to October 1, 2016.