Temporal Trends of Nitrate Pollution in Changing Village Environment

High levels of nitrate (NO3−) contamination of shallow groundwater resources in settlements due to inadequate wastewater treatment is a widespread environmental issue. Efforts to reduce pollution to enhance the quality of the municipal environment have to become an urgent priority. In recent years, significant developments in village wastewater collection and treatment have resulted in considerable changes in water quality. The present study investigated the NO3− contamination of groundwater in a Hungarian settlement between 2011 and 2021. The sewerage network was established in 2014, allowing comparative analysis regarding the pre-sewerage and post-sewerage periods. According to the results, the establishment of the sewerage network significantly reduced the NO3− concentrations. In the pre-sewerage period, NO3− concentrations exceeded the limit value (50 mg/L) in almost the entire municipality. In the central and southern areas, the values exceeded 200 mg/L and in several wells, values above 500 mg/L were determined. In the period following sewerage, a significant decrease in concentrations was found from 2017. The decline in the NO3− concentration also implies the significant loss of the pollutant supply. The lower quartile was below the limit value during the samplings in 2017–2021, unlike in the pre-sewerage period. Concentrations below the contamination limit value were found in 31% of the monitoring wells. Based on our results, it can be stated that the cleaning processes in the area have commenced; however, high NO3− concentrations indicate that the complete decontamination process could require several decades.