Protecção das Plantas e dos Produtos Agrícolas Armazenados

1.Environment Exposure and Effects of Pesticides (Table)

1.2.Surface water exposure and effects of pesticide to aquatic biota

Several laboratory and field studies were performed in order to study possible toxicity effects of surface waters of agricultural ecosystems to aquatic organisms as well as levels of pesticide exposition. In laboratory, several acute toxicity tests were carried out with formulated products of most used pesticides in the rice crop as well as with the respective active ingredients, in order to clarify the effects that they cause to the aquatic organisms and yet to compare differences of toxicity between formulated products and active ingredients. The pesticides tested were: molinate (granules), MCPA, propanil, endosulfan and clorfenvinphos (emulsifiable concentrate) and quinclorac (oil miscible suspension). Studies to observe the influence of storage of water samples at (4ºC and -18ºC) before testing in the toxicity of water fortified only with the formulated products referred above were also performed. The storage periods studied, at the above temperatures, were: 0, 4, 7, 14 and 28 days. Toxicity tests with the aim to determine the EC50 of the several formulated products, were also carried out. Concerning field work, water samples were collected in different strategic points defined along all study area of Sado Estuary: dams, rice plots, water canals, drainage channels and river. Sampling frequency was defined for rice plots, water canals and drainage channels according to the time of pesticide application, and for Sado river it was defined to be regularly performed every 15 days, except by the end of the field work period in which the sampling was carried out every 30 days. In all collected samples pH, temperature and conductivity were measured in field conditions, while chloride concentration, nitrates, nitritos e amónia were determined in laboratory. As it was referred in last year report the assessment of the acute toxicity of the collected water samples was performed using microbiotests based on immobilized forms of Daphnia magna, Thamnocephalus platyurus, Artemia salina, Selenastrum capricornutum and Vibrio fisheri. The toxicity values found are being compared with exposure data obtained from pesticide residues analyses carried out in the same water samples (in collaboration with DGA). Climatic data, particularly precipitation and temperature, have been registered from two points located in the studied area, and are also considered in the interpretation of field results. Besides the referred studies, a research on the existent models to predict environmental concentrations in surface waters is being performed in order to try to use them in this study case.