Trace elements in natural organic-rich surface soils: Contributions from natural and anthropogenic sources

Abstract

The aim of this research is to study the change of P and N contents of the surface runoff and subsurface flow caused by rainfall events, from the watershed till the stream. Samples were taken and analyzed from the surface runoff water after each rainfall event from five sampling points along a representative slope, from the groundwater at two points of the slope section, from the stream at the valley bottom and from the precipitation. The nitrate, nitrite, ammonium and phosphate contents of water samples were analyzed. Our results show that P also moves in dissolved form and appears both in surface runoff water and in groundwater. The P concentrations measured in the stream water is always lower than that of surface runoff, while the P amounts in the groundwater near the stream are high. The dissolved P is transported probably by the groundwater towards the lake. There was no relation found between the intensity and amount of precipitation as well as the amount of dissolved nutrients. The dissolved N appears almost solely as nitrate in the groundwater. The enhanced nitrate concentrations are due to the communal pollution, which exceeds the N contribution of agricultural activity. Contrarily, the dissolved N forms appear as ammonium in the surface runoff, while they are present as nitrate in the groundwater. With full knowledge of manures and fertilizers applied in the study area, the different anthropogenic sources derived from the agricultural and from communal pollution can be distinguished.