Abstract
Saturated paste extracts are sometimes used to estimate metal levels in the soil solution. To assess the significance of heavy-metal concentrations measured in saturation extracts, soil paste extracts were prepared with distilled water in amounts ranging from 60–200% of the moisture content at saturation. Trace metals behaved as if a small pool consistently was dissolved independent of the extraction ratio applied. Metal concentrations in the solution hence were not buffered by the solid phase, but the observed behaviour would allow the estimation of metal concentrations in the soil solution as a function of moisture content. The behaviour of iron and manganese suggested that some microbial reduction occurred. The intensity increased with increasing extraction ratio but not to the extent of affecting dissolution of trace elements.
Highlights
Potential adverse effects of heavy metals are most likely determined by their contents in the soil solution
In contaminated soils, leaching phenomena and the related risk of groundwater contamination are directly proportional to the concentrations in the soil solution, which in turn are determined by the physicochemical soil environment[3,4]
A saturated paste extraction of a soil is a method originally developed to determine salts in soils[5], but workers in heavy-metal research have relied on it to obtain a reflection of metal levels in the soil solution[4,6,7,8,9,10,11,12]
Summary
Potential adverse effects of heavy metals are most likely determined by their contents in the soil solution. With respect to plant uptake, it is assumed that the activity of the free metal ion in solution largely governs metal contents in crops[1,2]. Saturated paste extracts may provide a more practical alternative to obtain information about the soil solution. A saturated paste extraction of a soil is a method originally developed to determine salts in soils[5], but workers in heavy-metal research have relied on it to obtain a reflection of metal levels in the soil solution[4,6,7,8,9,10,11,12]
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