The need for rapid and reliable procedures for determining mercury in environmental samples need not be stressed. There has been growing interest during recent years in the particular case of sediments, since they can provide valuable information con- cerning the degree of contamination of rivers, lakes, estuarine and other aquatic environments. The determination of mercury levels in soils is also important, since human activities have led to the emission of this toxic metal into air, water and the soil itself. Soils are considered as sinks for trace elements, and mercury is no exception. Agricultural soils, in particular, can show relatively high levels of this metal as a consequence of the widespread use of fungicides, seed disinfectants, fertilizers and,