SCREENING, NEL VENETO, DI ACQUE DI FALDA IMPIEGATE PER L'ABBEVERATA, MEDIANTE SAGGI DI TOSSICITA' SU DAPHNIA MAGNA

Groundwaters used for livestock watering were screened for toxicity using the 48 hours immobilisation test on the microcrustacean Daphnia magna. This was done to generate a priority list of water samples to be further checked by chemical analysis for various contaminants. Fifty farms were monitored. From each site two samples were collected: one in summer and one in autumn. Seven summer samples and one autumn sample were quite toxic to D. magna (immobilisation effect >25%). Four summer samples and two autumn samples were only slightly toxic (effect=15-20%) while other 15 samples (9 summer, 6 autumn) were considered as suspect (effect=5-10%). The test was sensible enough for the prioritisation of the water samples and confirmed that ground waters are more contaminated during the summer season due to massive use of agricultural pesticides during the spring-summer period.