Spatially Resolved Soil Solution Chemistry in a Central European Atmospherically Polluted High-Elevation Catchment

Abstract. In order to interpret spatial patterns of soil nutrient partitioning and compare these with runoff in a temperate forest with a history of acidification-related spruce die-back, the chemistry of mineral soil solutions were collected by suction lysimeters and evaluated relative to concurrent loads of anions and cations in precipitation. Lysimeters nest were installed in the 33-ha U dvou loucek (UDL) mountain catchment at different topographic positions (hilltops, slopes and valley). Following equilibration, monthly soil solution samples were collected over a 2-year period. In the vicinity of each lysimeter nest, soil pits were excavated for constraining soil chemistry. Soil solutions were analyzed for SO 4 2− , NO 3 − , NH 4 + , Na + , K + , Ca 2+ , Mg 2+ , and total dissolved Al concentrations and organic matter (DOC), and pH. For a P release estimation, ammonium oxalate extraction of soil samples was performed. Comparison of soil water data with other previously acidified monitored European sites indicated that environmentally relevant chemical species at UDL had concentrations similar to median concentrations observed in sites with similar bedrock lithology and vegetation cover. Cation exchange capacity (CEC ≤ 58 meq kg −1 ) and base saturation (BS ≤ 13 %), however, were significantly lower at UDL, documenting incomplete recovery from acidification. Spatial trends and seasonality in soil water chemistry support belowground inputs from mineral-stabilized legacy pollutants. Overall, the soil-solution data suggest the system is out of balance chemically, relative to the present loads of anions and cations in precipitation. Higher concentrations of SO 4 2− , NO 3 − , and base cations in runoff than in soil solutions are explained by lateral surficial leaching of pollutants and nutrients from shallow soil horizons. Nearly 30 years after peak acidification, UDL exhibited similar soil solution concentrations of SO 4 2 , Ca 2+ and Mg 2+ as median values at the Pan-European International Co-operative Program (ICP) Forest sites, yet NO 3 − concentrations were an order of magnitude higher.