Sandy soils, in the border area of Belgium and the Netherlands (the Kempen region), are heavily contaminated by atmospheric deposition of cadmium and zinc from nearby smelters. Groundwater contamination by leaching from these low retention soils is subject of study. There are reports of high cadmium and zinc concentrations in groundwater in the area, but in most cases the direct sources are unknown. In an attempt to predict present or future risk of groundwater contamination by soil leaching, metal binding processes (retardation) were studied that are specific for these soil types under the existing acidifying conditions. From four fields nine contaminated profiles were sampled and analyzed for cadmium and zinc. Average concentrations of 131μg g⁻¹ zinc and 1.6μg g⁻¹ cadmium with maximum values of 2989μg g⁻¹ respectively 16.3μg g⁻¹ were found. In addition pH and contents of organic matter, aluminium, iron, and manganese were determined. The relative importance of these soil parameters for metal retardation is derived from the profiles. The data show that organic matter is the most important soil component for binding cadmium and zinc. Adsorption of cadmium and zinc on aluminium, iron and manganese (hydr) oxides appears to be of minor importance at low pH (<5.5).

Total mercury (Hg) and methylmercury (MeHg) concentrations were determined in sediments and in the polychaete wormNereis diversicolor at 13 stations of a brackish water intertidal mudflat of the Scheldt estuary. Hg and MeHg concentrations in sediments ranged from 144 to 1192 ng g⁻¹ dw and from 0.8 to 6 ng g⁻¹ dw, respectively. Both Hg and MeHg concentrations increased with an increase of organic matter (OM) content and fine grain fraction. In contrast, Hg accumulation byN. diversicolor was significantly (p<0.05) higher at stations with sandy sediments (mean value: 125 ng g⁻¹ dw) than at stations with muddy sediments (mean value, 80 ng g⁻¹), probably because Hg availability for bioaccumulation at muddy stations was reduced by high OM content of the muddy sediments. MeHg accounted for an average of 0.7% of the total Hg in sediments and 18% of the total Hg inN. diversicolor. Seasonal variations significantly affected Hg concentrations in sediments and MeHg inN. diversicolor. Total Hg concentrations in sediments were significantly (p<0.05) higher in autumn and winter than in spring and summer whereas MeHg concentrations were lowest in winter compared to the other seasons. On the other hand, total Hg concentrations in the worms were lowest in spring whereas MeHg concentrations were significantly (p<0.01) higher in spring and summer than in autumn and winter.