Fate of selected agrochemicals in a tropical karst aquifer: A five-year study

Abstract Water contamination by agricultural pollutants is one of the major environmental problems for terrestrial and aquatic life on earth. Recent studies have demonstrated the contamination of karst aquifers by pesticides and agricultural nutrients. However, the predominant research does not adequately address the main destination of these compounds. Also, research is targeted primarily towards Europe and North America. The objective of this study is to assess the fate of selected pesticides along the saturated layers of a karst aquifer, located in a tropical area. During a five-year period, 48 monthly collections were conducted by extracting samples from 24 shallow wells (8–9 m depth) and 24 deep wells (55–60 m depth). A total of 2880 samples were obtained. For all samples physical-chemical and pesticide analyses were performed. We found the presence of atrazine, lambdacyhalothrin, lactofen, fluazifop-p-butyl, chlorpyrifos, nitrate and nitrogen agricultural nutrients. The wells with 8–9 m depth had the highest concentration of the compounds studied in relation to deeper wells at 55–60 m. A significant difference was found regarding the types of pesticide (p -1 ) and the deepest wells (1.2 mg L -1 ) is observed along the period 2008–2013.