| For many, the Swedish forest in winter is an icon of pristine wilderness. Unfortunately, this may not be true. Using a newly developed sampler, our research group has shown that a number of legacy and emerging persistent organic pollutants (POPs) are being deposited in snowfall. Additionally, higher concentrations of POPs in streams draining supposedly pristine Swedish boreal forests have been reported than have been observed downstream of known contaminated sites. These alarming observations have potentially far reaching consequences for water quality in Swedish forests and the Baltic.
POPs flushed out from Swedish boreal catchments reach the Baltic Sea, where on-going pollution is a major problem. The levels of dioxins in fatty fish from the Baltic Sea frequently exceed EU regulatory limits. As point sources of pollution to the Baltic are cleaned up, diffuse pollution will comprise an ever greater share of the total load of POPs to the Baltic. Hence, research to understand deposition, fate and transport of POPs in the boreal landscape, both today and under a changing climate, is a vital part of improving the health of the Baltic ecosystem.
We will test the hypotheses that (i) transfer from the atmosphere of legacy and emerging POPs is highly efficient in boreal (cold) forested areas where precipitation is dominated by snow for much of the year, and (ii) these POPs will reach catchment waters particularly during snow melt events.
We will quantify the potential scale and fate of winter-time POPs deposition to the boreal forest using modern measurement techniques. The Krycklan Catchment Study (KCS) site is the ideal location for the proposed research. It is unique in Sweden and probably the world for its well-documented, long-term monitoring of climate, hydrology, soil and water chemistry in boreal forests and mires over decades.
Our overall goal is an improved understanding of the environmental behaviour of POPs in the boreal forest by studying two fundamental environmental interfaces: the ‘air-soil/snow’ interactions and the ‘terrestrial-to-stream’ processes that together regulate lake and stream water quality in remote catchments.
Specific objectives include: (i) Quantify atmospheric deposition and presence in surface water of a large variety of POPs in a boreal catchment using modern measurement techniques; (ii) Characterize the role of snow and overland flow as a vector of POPs transport to stream water; (iii) Examine the influence of dissolved organic carbon (DOC) and suspended particulate matter (SPM) on POPs transport and fate in headwater catchments; (iv) Explore the influence of organic carbon quality on POPs transport and fate by comparing forested and mire landscape elements.
Our study is the first of its kind to examine the importance of winter processes in deposition and transport of legacy and emerging POPs in the Swedish forest. The study will provide important new insights into deposition, cycling and output of legacy and emerging POPs in Sweden. Our results will help evaluate Sweden’s ability to meet international treaty obligations including the Water Framework Directive and prioritize POPs contaminated sites for remediation.
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