Paleolimnological assessment of the controls on metal mobility in Nova Scotia

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Arsenic (As) is a pervasive environmental toxin and carcinogenic metalloid in Maritime Canada. Surface and groundwater systems are highly susceptible to arsenic enrichment. Bioaccumulation of arsenic is a significant concern. In Nova Scotia arsenic poisoning from groundwater sources has been reported and elevated concentrations in soils and aquatic sediments are common. There are many natural local and regional sources of arsenic; mining and development have both concentrated and mobilized the metalloid. The mobility of arsenic among environmental media is complex, the factors affecting the retention and mobility of arsenic in fresh and brackish surface water systems are poorly understood. This research proposal focuses on the use of lake sediment archives (paleolimnology) to better understand how watershed-scale landscape disturbance (mining, development) influences the mobility and retention of arsenic in a variety of environments in Nova Scotia, Canada.*******Research will take place in Halifax Regional Municipality (HRM), Cape Breton Regional Municipality (CBRM) and the Cumberland Marsh Region (Nova Scotia-New Brunswick border region). Stable isotopes (C, N), bulk sediment geochemistry (ICP-MS, XRF, XRD), and a suite of abiotic proxies coupled with radiometric dating (14C and 210Pb) will be applied to lake sediment archives obtained by gravity coring to reconstruct 500-year sedimentary records. Bioproxy research in NS that identified the significant environmental stressors (e.g. pH, T, EH, TP) in surface water systems will be applied to predict how environmental change has and will influence arsenic mobility and retention in lake sediments. Groundwater models are being developed for HRM and CBRM that will be used to help predict the relationship between historical watershed disturbance and the bulk geochemistry of lake sediments. A >300 year historical record of landscape disturbance at all sites will enable the integration of the lake sediment archive with historical records to better understand the relative importance of disturbance, water column chemistry and climate variability on metal mobility and retention. As well, the role of lake sediment composition and lake water column redox conditions in metal sequestration and mobility will be explored.*******This research is collaborative and will be integrated with bioaccumulation and toxicology research already in progress. The proposed research will develop strategies that will facilitate effective watershed management and help determine conditions that increase the risk of elevated arsenic in groundwater and arsenic bioavailability and mobility in aquatic systems. The field and laboratory techniques required in this research will train highly qualified individuals and are transferrable and relatively inexpensive; technology transfer to both the public and private sector will be an important component of this research.***