DEVELOPMENT OF ZINC BIOAVAILABILITY AND TOXICITY FOR THE SPRINGTAIL FOLSOMIA-CANDIDA IN AN EXPERIMENTALLY CONTAMINATED FIELD PLOT

The influence of outdoor exposure conditions and ageing of contaminati on on the toxicity of zinc was investigated for the springtail Folsomi a candida to evaluate the validity of a standardised soil toxicity tes t. In three successive years, animals were incubated in an experimenta lly contaminated field plot. During the first months after constructio n of the test field, total zinc concentrations of the soil decreased r apidly due to leaching of excess zinc with rainwater, while increased sorption of the remaining residues resulted in a reduced bioavailabili ty of the metal. Although variation between replicates was substantial , the EC(50)s for the effect of zinc on reproduction off. candida dete rmined in the field experiments differed by less than a factor of two from effect concentrations obtained in laboratory tests in which the s ame soil was used. Expression of the EC(50)s on the basis of water sol uble zinc allowed for a comparison with effect concentrations estimate d for other soil types. EC(50)s were comparable with literature data, which indicates that bioavailability of zinc is the main factor determ ining toxicity for F. candida. It is concluded that laboratory based t oxicity data are suitable to predict effects of zinc for F. candida un der outdoor conditions, provided that the bioavailability of zinc is d etermined accurately using water soluble concentrations. (C) 1998 Else vier Science Ltd. All rights reserved.