MODELING AND MONITORING ORGANOCHLORINE AND HEAVY-METAL ACCUMULATION IN SOILS, EARTHWORMS, AND SHREWS IN RHINE-DELTA FLOODPLAINS

In the Rhine-delta, accumulation of microcontaminants in floodplain fo odwebs has received little attention in comparison with aquatic commun ities. To investigate organochlorine and metal concentrations in a ter restrial foodchain, samples of soil, earthworms (Lumbricus rubellus), and shrew (Crocidura russula, Sorer araneus) livers and kidneys were t aken from two moderately to heavily polluted floodplains. Chlorobiphen yl residues in earthworm fat were 0.10 to 3.5 times the concentrations in soil organic matter, whereas ratios for other organochlorines vari ed between 0.87 and 8.8. These ratios are one order of magnitude lower than expected from laboratory experiments with earthworms, and labora tory and field studies on aquatic invertebrates. Bioconcentration rati os for heavy metals are in accordance with literature values for other locations, confirming the high potential for cadmium accumulation in Lumbricidae. Concentrations of organochlorines in shrew liver lipids w ere 1.0 to 13 times the residues in earthworm fat. These values are hi gher than lipid-corrected biomagnification ratios for laboratory roden ts, but equal to those measured far benthivorous birds in the Rhine-de lta. On a dry weight basis, kidney-earthworm ratios for cadmium were a bout one order of magnitude lower than previously reported values for insectivores. Soil concentrations of many compounds in both floodplain s did not meet Dutch quality standards. Yet, hexachlorobenzene, chloro biphenyl 153 (PCB153), gamma-hexachlorocyclohexane, Sigma DDT, and die ldrin residues in earthworms and shrews did not exceed diet levels exp ected to be safe for endothermic species. An exception was noted for c admium in worms and shrew kidneys. Heavy metal pollution in soil was c lose to levels that are critical to earthworms in laboratory studies. Cadmium concentrations in shrew kidneys were below levels suggested to be safe for Sorer araneus, but above those that were critical to the rat.