The effect of forest vegetation on the formation of mercury accumulation signals in lake sediments

拟议项目的目的是研究森林植被的变化如何影响湖泊沉积物中汞的积累。该方法建立在湖泊集水区不同的森林植被对森林土壤的汞积累速率不同的假设之上。此外，森林类型影响森林土壤中有机质（OM）的生产、退化和释放，从而也影响汞向湖泊的输送。拟议中的项目将结合对四个集水湖系统（一个是落叶植被，三个是针叶植被）的长期（几千年）沉积物记录和已知植被历史（来自花粉分析）的调查。此外，我们将通过POM和DOM分析来研究研究湖泊中OM的质量和数量与Hg沉积的当代关系。由于土壤和沉积物中有机质的化学特征受到森林植被的强烈影响，我们将使用定性方法，其中OM质量（由傅里叶变换红外光谱和热解-气相色谱-质谱法定义）将与森林植被的变化联系起来，这些变化来源于沉积物中的树木花粉分布。此外，我们将使用多元统计方法来厘清森林植被变化对湖泊沉积物中汞积累的影响在多大程度上可以与其他影响汞负荷的过程区分开来。对这种关系的更深入了解被视为预测在土地利用或气候条件变化下，北半球广泛受污染的表层土壤中汞向水生系统释放的基础。

The aim of the proposed project is to study how changes in forest vegetation will affect the accumulation of mercury in lake sediments. This approach builds on the hypothesis that different forest vegetation in lake catchments causes different Hg accumulation rates to forest soils. Moreover, forest type affects production, degradation and release of organic matter (OM) from forest soils, and thus also the transport of mercury to lakes. The proposed project will combine the investigation of long (several millennia) sediment records with known vegetation histories (from pollen analyses) taken from four catchment-lake systems, one with deciduous and three with coniferous vegetation. In addition we will investigate the contemporary relation between OM quality and quantity and Hg sedimentation in the study lakes through POM and DOM analyses. As chemical characteristics of organic matter in soils and assumingly also in sediments are strongly influenced by forest vegetation, we will use a qualitative approach where the OM quality (as defined by Fourier-transform infrared spectroscopy and Pyrolysis-GC-MS) will be related to changes in forest vegetation as derived from the tree pollen distribution in the sediments. Moreover, we will use multivariate statistical approaches to disentangle to which extent the influence of changes in forest vegetation on Hg accumulation in the lake sediments can be distinguished from other processes affecting the Hg load. A deeper understanding of this relationship is seen as the basis to predict the release auf Hg from the widely contaminated surface soils in the Northern Hemisphere to aquatic systems under changing land use or climatic conditions.