Concentration and chemical species of iron in soils from groundwater/surface water ecotones

Abstract

The total pools and chemical species of Fe in soils from sevengroundwater/surface water ecotones were analysed. The associated soil waters from four of the sites were analysed for Fe and SO4. The selected sites were mainly the upper reaches of streams in coniferous forests, having a size of 3–4 m2. The results showed great differences in total Fe concentrations in the soils. The high positive correlation between pyrophosphate- extractable Fe and organic matter (Spearman rank coefficient 0.700) indicated the importance of organic C for the retention of Fe. Organically-bound Fe and Fe oxides were the major species in all the soils. Moreover, soil water analyses suggested that sulphate reduction occurs, with the formation of Fe-sulphides during seasons with high microbiological activity. Comparable sulphate concentrations in groundwater and runoff waters, but much lower concentrations in peat waters, may be a result of a dynamic cycling of reduction and oxidation within the soils. Another explanation could be that most of the discharging groundwater was flowing quickly through more permeable sections of the soil. © 1995 Taylor and Francis Group, LLC.