Analysis of antibiotic and pesticide residues in shrimp farm waters using passive sampling

Vietnam is one of the largest shrimp exporters in the world. Intensive shrimp farming uses a lot of insecticides to sanitize the shrimp ponds and antibiotics for the prevention of diseases. The aims of this study are to develop a passive sampling method for evaluation of fifteen antibiotics and pesticides in the surface water and determine the contamination of surface waters by these compounds in Can Gio district – Ho Chi Minh City and Long An province, two major intensive shrimp farming sites in Southern Vietnam. Passive samplers (Polar Organic Chemical Integrative Samplers - POCIS) enable to calculate time-weighted average concentrations of the free dissolved fraction of pollutants and thus provide precious data about pollutant bioavailability. A two-weeks in-situ calibration in a Long An shrimp pond has been done, where aqueous concentrations of the compounds of interest obtained by composite sampling have been compared to the concentrations of these same compounds in POCIS, with the use of deisopropyl atrazine-d5 as Performance Reference Compound (PRC). The results showed that, passive sampling with POCIS is quite effective for evaluation of antibiotics and pesticides in surface water. Five calibration sampling rates (Rs) – for three antibiotics and two pesticides – have been calculated. The antibiotics and pesticides were found in both surface waters from the shrimp ponds and the canals. The maximum aqueous concentrations of total antibiotics and total pesticides were found in the shrimp ponds, 2800 ng/l and 250 ng/l respectively.