Geographical distribution of pesticides in waters of the river Júcar, Spain

Abstract

Among emerging contaminants, the group of pesticides is associated to farming activities (Richardson, 2012). Research to large basin scale is needed to understand surface waters transport and hydrological connectivity of contaminants. The working hypothesis of this research is that at large geographical scale pesticides and herbicides are related to major landscape land use-cover types. The methodological framework developed consisted on the application of environmental forensic criteria (Taylor, 2004) combining laboratory analytical water samples and cartographic analysis using Geographical Inforn1ation Systems (GIS). For the frrst case, the sampling strategy consisted in the collection of 15 water samples distributed alongside the River Júcar and its two main tributarles (River Cabriel and Magro), located in the River J úcar drainage Basin. After selective sample extraction, 50 pesticides were identified and quantified by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) (Masiá et al., 2013). Geographical analysis were performed after geo-location of sampling points analytical results and integration in the GIS environment using CORINE land use-cover layers for the year 2006. Out of 50 pesticides 20 were identified and 18 presented concentrations higher than the Limits of Quantification. Values ranged from 0.04 ng¿L-1 (Terbuthylazine-2 Hydroxy) to 79.39 ng¿L-1 (Carbendazim), 150.75 ng¿L-1 (Thiabenzadole) and 222.45 ng¿L-1 (Imazalil). Contaminants identified more frequently were Chlorpyriphos, Ethion, Chlorfenvinphos and Imazalil, found in 15, 13, 12 and 10 sites respectively. There is a clear geographical trend in the number of pesticides found and their concentrations. Three main land use-cover areas where established, according to the dominant vegetation cover: natural surfaces, rainfed agriculture and intensive irrigation fatming. The number of pesticides incrise from natural areas (28 incidencies in 6 si tes) to rainfed (3 7 detections in 5 sites) and irrigation agriculture (50 incidencies in 4 sampling points). Higher levels of concentrations area also found in the sector with intensive irrigation agriculture.