Abstract
This paper addresses groundwater pollution and the potential presence of pesticides within the catchment areas of two reservoirs that are sources of drinking water. The two reservoirs are Goczałkowice and Kozłowa Góra, both in Southern Poland. Agricultural and rural areas dominate both catchments. Archival data showed local groundwater contamination with nitrates. This indicated the possible presence of pesticides in shallow groundwater. In total, 13 groundwater samples from shallow sandy aquifers were collected. All the samples were tested for the presence of 35 organophosphate pesticides and 28 organochlorine pesticides. Additionally, in order to determine the current groundwater conditions, physicochemical parameters were measured in the field, and water samples were subjected to analysis of their chemical composition (incl. the determination of nitrates). The research outcomes showed that pesticides were not detected above the detection limits in any of the samples. Due to variations in the persistence and degradation rates of pesticides, the occurrence of these substances in the groundwater environment and the possibility of their migration to aquifers should not be completely excluded. Natural processes and factors (e.g., sorption, biodegradation, hydrolysis and redox conditions) may gradually reduce the pesticide concentrations in groundwater. The chemical analyses revealed high concentrations of nitrates in the groundwater. This suggests the possible influence of agriculture and fertilizer application on groundwater quality; however, a proportion of NO3- ions may be connected with improper sewage management within the two catchments. The absence of pesticides in groundwater impacted by agriculture may result from processes occurring in the aquifer and the rapid degradation of these compounds due to photolysis and prevailing weather conditions. In the vicinity of dwellings, nitrates also originate from domestic wastewater. Thus, the occurrence of pesticides in groundwater contaminated with NO3 cannot always be expected.
Highlights
Pesticides are chemicals that are widely used all over the world as plant protection products, which allow plant growth to be controlled and pests to be repelled
One example is a monitoring study conducted in Minnesota, USA [15], which revealed that high concentrations of nitrates are related to the presence of pesticide residues in shallow aquifers
The significant influence of human activity on groundwater quality was manifested through elevated concentrations of nitrates, the results of the investigation showed that pesticides were absent or nearly so
Summary
Pesticides are chemicals that are widely used all over the world as plant protection products, which allow plant growth to be controlled and pests to be repelled. These substances are applied in agriculture since they significantly improve crop yields, deter pests such as insects, and kill weeds. The use of pesticides in high doses may contribute to contamination of the water environment, since chemicals may be leached from soils and migrate to shallow aquifers [1,2,3,4,5,6,7]. Both the detection frequency and the observed pesticide concentrations increased with the increasing nitrate concentration
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