EARTHWORM COMMUNITIES ALONG A GRADIENT OF URBANIZATION

Earthworms were studied at six sites along a gradient of urbanization and their relations with several soil abiotic factors were determined. Concentrations. of heavy metals, calcium and magnesium in earthworms and in soils were measured by atomic absorption spectroscopy. Strong n egative correlations were detected between earthworm density and soil concentrations of cadmium and magnesium. Earthworm biomass was negativ ely correlated with lead, copper and zinc, and positively correlated w ith the distance from the centre of the city. High concentrations of C d and Zn (concentration factors 49 and 32) were accumulated by earthwo rms in contrast to those of Cu and Pb (2 and 1). Relations between wor m and soil concentrations of heavy metals, Ca and Mg are discussed.