Occurrence of Banned and Currently Used Herbicides, in Groundwater of Northern Greece; A Human Health Risk Assessment Approach

Abstract The presence of pesticide residues in groundwater, many years after their phase out in European Union verifies that the persistence in aquifer is much higher than in other environmental compartments. Factors such as limited degradation, and adsorption in phreatic horizon have resulted in frequent detection of pesticide residues and their metabolites in the saturated zone. Currently used and banned pesticides were monitored in Northern Greece aquifers and risk to human health was assessed. The target compounds were the herbicides metolachlor, terbuthylazine, atrazine and its metabolites Deisopropylatrazine (DIA), Deethylatrazine (DEA) and Hydroxyatrazine (HA). The area’s aquifer has been extensively studied over the past 20 years. Eleven sampling sites were selected in order to have representatives of different type of wells. Namely, five drinking water, two irrigation wells and four experimental boreholes located close to Greek/Turkish/Bulgarian borders were monitored and fifty-four samples were analyzed. Pesticides were extracted by solid-phase extraction and analyzed by liquid chromatography. Metolachlor was detected in 100% of water samples followed by ATR (96.4%), DEA and HA (88.6%), DIA (78.2%) and TER (67.5%). Atrazine, DIA, DEA, HA, MET and TER mean concentrations detected were 0.18, 0.29, 0.14, 0.09, 0.16 and 0.15 μg/L, respectively. Obtained results were compared with historical data from our previous monitoring studies (1999-2003 and 2010-2012) and temporal trends were assessed. Preferential flow was the major factor facilitating pesticide leaching within the month of herbicide application. Moreover, apparent age of groundwater and the reduced pesticide dissipation rates on aquifers resulted of long-term detection of legacy pesticides. Although atrazine had been banned more than 15 years ago, it was detected frequently during our monitoring campaign and their concentrations in some cases were over the maximum permissible limit. Furthermore, human health risk assessment of pesticides was calculated for two different age groups though drinking water consumption. The presence of atrazine residues causes concerns related with chronic toxicity.