Euro-limpacs Deliverables

ABSTRACT - DELIVERABLE 67

Report outlining the experimental design and sampling strategy for study of climate change and mercury mobilisation

Future climate scenarios suggest that precipitation amounts will vary substantially in different parts of Europe. In some regions, large increases are expected. Increased precipitation will potentially affect the mobility of mercury and other pollutants accumulated in forest soils and can thus lead to increased loadings on surface waters. The objective of this activity in WP 5 is to determine the influence of increased precipitation on the release of total mercury and methylmercury from forest soils to surface waters. The main hypotheses are that increased precipitation will change the hydrological pathways in the soil and enhance the leaching of total mercury and methylmercury and lead to the formation of anaerobic zones in the soil which will enhance formation of methylmercury. This report describes the experimental design and sampling strategy at an irrigation experiment at the Gårdsjön catchment in Sweden to address these issues.

Additionally, the experimental design and sampling strategy of the THERMOS experiment at Lake Halsjärvi, Finland are described. This seeks to examine the effect of climate change on the mercury cycle in small boreal lakes. The main aim in this subtask is to carry out a whole−lake experiment (THERMOS) to study climate change impacts on lake chemistry and biology by manipulating the lake stratification pattern (thermocline depth). The mercury work in WP5, task 3 is closely connected to WP1 (Task 3). There are also close links with the Norwegian THERMOS lake manipulation experiment, where a clear water deep mountain lake has been manipulated. Detailed monitoring of several chemical and biological variables (mainly weekly−biweekly sampling) is on−going in a) the reference lake Valkea−Kotinen and b) the manipulation lake Halsjärvi (See WP1, Task 3.3).

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