Mechanisms of the air-surface exchange of organic pollutants and mercury in a Chinese subtropical forest

Project summary The overall aim of the project is to develop tools and conceptual frameworks to evaluate the mechanisms controlling the inter-compartment exchange of long range transported semivolatile persistent pollutants (SVPPs) in a forest soil system , in order to provide elements to link pollutant fate with the climatic and ecological factors and their seasonality. The focus here will be on selected persistent organic pollutants (POPs) and mercury (Hg) in the sub-tropical forest scenario, but the mec hanisms and set up also has relevance for other areas and biotopes. Climate change is expected to increase the yearly average temperatures, modify meteorological conditions and causing a modification in ecosystem functions and distributions. A deep know ledge of the mechanisms linking climate/biogeochemical cycles and pollutant environment partitioning is needed to assess future exposure scenarios. The experimental activity of this project will be carried in a subtropical forest site in China, character ized by high productivity, fast turn over of soil organic matter and enhanced seasonality of precipitations. This scenario is therefore ideal to assess the influence of the carbon cycle and varying hydrological regimes on the fate of POPs, with the goal o f quantitatively characterizing it in terms of its ability of behaving as a net sink or source for SVPPs. To address the specified objectives, the following activities are planned: - periodical measurements of air/soil exchange fluxes and velocities for selected SVPPs using a newly developed echange-meter and low volume air samplers, respectively; - determine the leaching flux of SVPPs from surface soils, by measuring the water dissolved phase in the exchange meter; - determine the distribution of SVPPs in different soil horizons; - Collection of support data on physical/ecological parameters to test and identify the mechanisms controlling the exchange. The planned activity will directly address the outlines objectives and help us reach the primary aim of the project: evaluate the mechanisms controlling the inter-compartment exchange of long range transported semi-volatile persistent pollutants (SVPPS) in a forest-soil system. The project foresees the partnership between NIVA and two outstanding Chine se institutions. Additionally, another European institute will externally support the activities. All partners will take part to the project in a balanced and cooperative way, with particular attention on the transversal transfer of knowledge