Spatial and temporal patterns of groundwater chemistry in the river riparian zone

Abstract

The nutrients dynamics and groundwater flowpaths were studied in a riparian zone of the Narew River valley (NE, Poland). On the monthly basis a transect of monitoring wells extending across cropland, a row of trees, grass belt and mire up to a river were sampled for NO3−, SRP, Cl−, K+, Fe2+/3+. The Groundwater Modelling System (GMS) was used to assume the spatial and temporal aspects of groundwater movement. The highest concentration of nitrate, potassium and chloride were observed under the fertilized cropland. Their content diminished abruptly towards the wetland and the river. The soluble reactive phosphorus (SRP) concentrations were highest in groundwater of deeper peat horizons and in alluvial sands beneath the peat. Our results revealed that water infiltrating from the field is diverted into alluvial sands beneath the riparian soils and probably below the range of plants roots. Thus, the removal of agrochemicals does not take place in shallow, organic-rich sediments or soils of the riparian zone, but it occurs in sandy aquifer in the valley. Although tree and grassland strips do not play significant role in diminishing of groundwater pollutant transport they are important barrier for sediment-bound P transported from cropland with erosion and surface runoff.