The response of metal leaching from soils to climate change and land management in a temperate lowland catchment

Changes in soil hydrology as a result of climate change or changes in land management may affect metal release and leaching from soils. The aim of this study is to assess the cascading response of SOM and DOC levels and metal leaching to climate change in the medium-sized lowland Dommel catchment in the southern part of the Netherlands. We implemented the CENTURY model in a spatial setting to simulate SOM, DOC, and water dynamics in topsoils of the Dutch portion of the Dommel catchment under various climate and land management scenarios. These CENTURY model outputs were subsequently used to calculate changes in the topsoil concentrations, solubility, and leaching of cadmium (Cd) and zinc (Zn) for current (1991-2010) and future (2081-2100) conditions using empirical partition-relations. Since the metal leaching model could not be evaluated quantitatively against measured values, we focus mainly on the trends in the projected metal concentrations and leaching rates for the different scenarios. Our results show that under all climate and land management scenarios, the SOM contents in the topsoil of the Dommel catchment are projected to increase by about 10% and the DOC concentrations to decrease by about 20% in the period from present to 2100. These changes in SOM and DOC only have a minor influence on metal concentrations and leaching rates under the climate change scenarios. Our scenario calculations show a considerable decrease in topsoil Cd concentrations in the next century as a result of increased percolation rates. Zinc, however, shows an increase due to agricultural inputs to soil via manure application. These trends are primarily controlled by the balance between atmospheric and agricultural inputs and output via leaching. While SOM and DOC are important controls on the spatial variation in metal mobility and leaching rates, climate-induced changes in SOM and DOC only have a minor influence on metal concentrations and leaching rates. The climate-induced changes in metal concentrations in both the topsoil and the soil leachate are primarily driven by changes in precipitation and associated water percolation rates.