A monitoring of chemical contaminants in waters used for field irrigation and livestock watering in the Veneto region (Italy), using bioassays as a screening tool

In this study, 50 livestock watering sources (ground water) and 50 field irrigation sources (surface water) from various industrialised areas of the Veneto region were monitored for chemical contaminants. From each site, four water samples (one in each season) were collected during the period from summer 2009 through to spring 2010. Surface water samples and ground water samples were first screened for toxicity using the growth inhibition test on Pseudokirchneriella subcapitata and the immobilisation test on Daphnia magna, respectively. Then, based on the results of these toxicity tests, 28 ground water samples and 26 surface water samples were submitted to chemical analysis for various contaminants (insecticides/acaricides, fungicides, herbicides, metals and anions) by means of UPLC-MSn HPLC-MSn, AAS and IEC. With the exception of one surface water sample where the total pesticides concentration was greater than 4 mu g L-1, positive samples (51.9 %) showed only traces (nanograms per liter) of pesticides. Metals were generally under the detection limit. High concentrations of chlorines (up to 692 mg L-1) were found in some ground water samples while some surface water samples showed an excess of nitrites (up to 336 mg L-1). Detected levels of contamination were generally too low to justify the toxicity recorded in bioassays, especially in the case of surface water samples, and analytical results painted quite a reassuring picture, while tests on P. subcapitata showed a strong growth inhibition activity. It was concluded that, from an ecotoxicological point of view, surface waters used for field irrigation in the Veneto region cannot be considered safe.