Nitrogen Dynamics In Groundwater Of Gley SOILS In Eastern Croatia.

NITROGEN DYNAMICS IN GROUNDWATER OF GLEY SOILS IN EASTERN CROATIA (poster presentation) D. Petosic, I. Mustac University of Zagreb, Faculty of Agriculture, Department of Soil Amelioration, Svetosimunska 25. 10 000 Zagreb SUMMARY Groundwater contamination caused by agricultural activities is an increasingly more topical theme in Croatian public, notably in regions with discernible problems of increasing nitrogen concentrations. The main goal of this study was to assess nitrogen dynamics in groundwater of gley soils to 4.0 m profile depth. Five-year investigations (2002-2006) were carried out in the Eastern Slavonija region of Croatia. Investigation results are based on field piezometer and laboratory investigations, which covered a total area of ca 8,700 ha. Nitrogen dynamics in groundwater of gley soils was continually monitored and analyzed throughout the period 2002-2006 on 50 locations – piezometers. It was found that the mean values of nitrogen concentration in groundwater of gley soils throughout the investigation period (2002-2006) were below the maximum allowable concentrations (MAC) pursuant to the Rulebook on Health Criteria for Drinking Water Official Gazette 182, 12. 2004. (11 mg N/l), ranging from 1.66 mg N/l to 4.85 mg N/l. It should be mentioned that according to the mean nitrogen concentration values during the studied period (2002-2006) and pursuant to the criteria prescribed by the Water Classification Directive in Croatia (Official Gazette 77/98), the groundwater of gley agricultural soils in the monitored area belongs to the third ecological quality category. However, maximum allowable concentrations of nitrogen in groundwater of gley agricultural soils on ca 10% of monitored locations were continually during the investigation period (2002-2006) higher than MAC (11 mg N/l), pointing to the potential risk of higher groundwater contamination by nitrogen in the wider agricultural region of Eastern Slavonija in Croatia. Keywords: dynamics, concentration, nitrogen, groundwater, gley soil