Occurence and transport of mercury within a small catchment area

Abstract

To contribute to the understanding of Hg flow to forest lakes the storage of Hg in the soil of a catchment was quantified, the transport of Hg from the recharge area to the discharge area was studied and a mass balance for different soil horizons was calculated. The transport of Hg in soil, ground and stream water was estimated using water flows from a hydrological model and by determining Hg in water sampled with a clean procedure. The estimate for the annual Hg flux out of the till overburden in the catchment was 3.4 g km−2. The annual flux was reduced to 1.3 g km−2 in the stream, indicating interception in a lake. The transport was predominantly taking place in the upper 50 cm of the soil. The storage of Hg in the soil was 8.8 kg km−2, which is large compared to the flux. A net accumulation, amounting to 80% of the Hg deposition, is almost entirely located to the nor layer.