Özet:

Agricultural activities are frequently associated with groundwater pollution. In this study, the goal is to evaluate the nitrate and phosphorus levels and it's impact to the groundwater. The investigation was located in the Eastern Croatia in the area of 6.600 ha of mainly agricultural land. Groundwater quality in the countertop part of the soil profile to 4.0 m depth was monitored by 40 installed hydropedological piezometers. Sampling water from piezometers was carried out every 60 days. In the groundwater samples nitrate, nitrite, ammonia and orthophosphate were analyzed. According to the indicators it was confirmed that at all locations during the observation period mean concentrations of NH4-N, NO3-N, total nitrogen (N) and phosphorus (P) in the groundwater from piezometers occasionally exceeded the value of maximum allowable concentration (MAC) which is prescribed by the Regulations. The mean concentrations of NO3-N were consistent and varied in the range from 2.42 to 4.61 mg NO3-N/l, the mean concentrations of nitrogen from ammonia exceed the permissible value (NH4-N) throughout the year, the average being higher than MAC (0.50 mg NH4-N/l) and were within the range of 0.57 mg NH4-N/l in to 1.21 mg NH4-N/l. The maximum concentration of phosphorus in groundwater were in the range of values from 0.40 to 1.11 mg P/l. Observation of traditional agricultural production in the investigation area with emphasis on leaching of nitrogen and phosphorus shows that it represents a potential threat to the future pollution of groundwater with nitrogen with phosphorus.

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