Surface and ground waters characterization in Tuscany (Italy) by using algal bioassay and pesticide determinations: comparative evaluation of the results and hazard assessment of the pesticides impact on primary productivity

Algal bioassays and pesticide analysis were joined in Tuscany regional monitoring of surface and ground waters. Results were compared. Waters affected algal growth in any of the following ways: stimulation, inhibition, stimulation at low concentrations and inhibition at higher concentrations. Most of ground waters inhibited algal growth whereas only a little percentage were contaminated with pesticide. Most of surface waters stimulated algal growth and a higher percentage were contaminated with pesticides. In waters with inhibitory effect toxicological parameters (EC50, EC25, EC10 and NOEC) were measured and compared; EC25 values were very close to NOEC values. Hazard to aquatic primary productivity for each pesticide found during chemical monitoring was evaluated; for this aim the margin of safety (MOS) was calculated by using algal toxicity and the pesticide concentration measured.