Using the 96 hours growth inhibition test on the green alga Pseudokirchneriella subcapitata and the 48 hours immobilisation test on the microcrustacean Daphnia magna, surface waters used for field irrigation and ground waters used for livestock watering were respectively screened for toxicity. This was done in order to generate a priority list of water samples to be further checked by chemical analysis for various contaminants. Fifty livestock watering sources and fifty field irrigation sources were monitored. From each site four samples (one in each season) were collected. Irrigation samples were filtered and then diluted in algal medium before testing. Livestock watering samples were filtered, their salinity and pH adjusted to those of D. magna medium, and then tested without dilution. The large majority of irrigation samples tested positive, particularly those collected during the summer season, where some samples showed more than 50% algal growth inhibition even at the highest dilution (1:8). Effects of ground water samples on D. magna were moderate, and the majority of samples tested negative. Positive samples generally caused not more than 10% immobilisation and were considered only as suspected toxic, some samples caused 15-45% immobilisation while only a few samples, collected during the summer season, caused 45-60% immobilisation. Altogether the tests showed to be sensible enough for the prioritisation of the water samples and confirmed that both surface and ground waters are more contaminated during the summer season, probably due to the massive use of fertilizers and pesticides on crops during the spring-summer period. The results indicate also that in the Veneto region the contamination of surface waters is a serious problem while that of ground waters is only a moderate problem and regards essentially those waters coming from aquifers that are closer to the surface.
An overall toxicity screening of waters used for field irrigation and livestock watering in the Veneto region, using Pseudokirchneriella subcapitata and Daphnia magna as test organisms
DE LIGUORO, MARCO;DALLA BONA, MIRCO;GALLINA, GUGLIELMO
2011
Abstract
Using the 96 hours growth inhibition test on the green alga Pseudokirchneriella subcapitata and the 48 hours immobilisation test on the microcrustacean Daphnia magna, surface waters used for field irrigation and ground waters used for livestock watering were respectively screened for toxicity. This was done in order to generate a priority list of water samples to be further checked by chemical analysis for various contaminants. Fifty livestock watering sources and fifty field irrigation sources were monitored. From each site four samples (one in each season) were collected. Irrigation samples were filtered and then diluted in algal medium before testing. Livestock watering samples were filtered, their salinity and pH adjusted to those of D. magna medium, and then tested without dilution. The large majority of irrigation samples tested positive, particularly those collected during the summer season, where some samples showed more than 50% algal growth inhibition even at the highest dilution (1:8). Effects of ground water samples on D. magna were moderate, and the majority of samples tested negative. Positive samples generally caused not more than 10% immobilisation and were considered only as suspected toxic, some samples caused 15-45% immobilisation while only a few samples, collected during the summer season, caused 45-60% immobilisation. Altogether the tests showed to be sensible enough for the prioritisation of the water samples and confirmed that both surface and ground waters are more contaminated during the summer season, probably due to the massive use of fertilizers and pesticides on crops during the spring-summer period. The results indicate also that in the Veneto region the contamination of surface waters is a serious problem while that of ground waters is only a moderate problem and regards essentially those waters coming from aquifers that are closer to the surface.
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