Determination of diazinon concentration by Gas Chromatography - Mass Spectrometry in underground drinking water resources located near the rice fields, before and after the pesticide spraying

Abstract Widespread and unsupervised use of pesticides in the rice fields of northern Iran has greatly increased the concern about their presence in drinking water resources. This study aimed to determine the effect of spraying of rice fields on the concentration of diazinon in rural underground drinking water resources with depth and water table of about 120 and 30 m respectively. Sampling was performed at regular intervals, before the first and after the last spraying. Diazinon extraction was carried out by USEPA liquid–liquid extraction method and the concentration of diazinon was measured by GC / Mass Spectrometry. No diazinon was observed in any of water resources before spraying, while the average concentration of diazinon after spraying was 0.005 ± 0.007 µg/l. Also there was a significant difference in diazinon concentration between water resources after spraying rice fields. There was a reverse significant correlation between the diazinon concentration and longitudinal distance from water resources to rice farms. Moreover, there was a significant direct correlation between the diazinon concentration in post-spraying samples and water turbidity. In general, spraying rice fields can cause diazinon to enter underground water resources near farms and it can be present in water resources for at least one month after the last spraying.