1. NITRATE CONCENTRATION IN DRINKING WATER FROM WELLS AT THREE DIFFERENT LOCATIONS IN NORTHWEST CROATIA Jasna NEMCIC JUREC Milan MESIC Ferdo BASIC Ivica KISIC Ivica KISIC Zeljka ZGORELEC

2. INTRODUCTION  Agriculture is often recognized as one of the most important non-point-source of pollution with nitrogen (N) and in some areas it can be a major cause of water-quality problems  Excessive levels of N-fertilisation may increase nitrate (NO3-) leaching although some natural processes can be also taken into account when groundwater nitrate levels are discussed  Groundwater pollution by nitrates has become a problem of major concern for surrounding communities that use groundwater as their water supply.

3. EU Nitrate Directive (91/676/EEC)  Was designed to reduce water pollution from agriculturally derived nitrates  Drinking water Directive establishes maximum allowable level of 50 mg/L and guideline level of 25 mg/L

4. Nitrate leaching  The highest nitrate leaching usually occurs during the autumn and winter period when precipitation exceeds evaporation and the plant intake is reduced to the minimum  In urban and suburban areas other sources of water pollution prevails and in some cases problems with sewerage systems can be defined as the most important ones

5. to investigate NO3- pollution of to investigate NO3- pollution of drinking water in 6 wells located in different parts of Northwest Croatia

6. MATERIAL AND METHODS Locations were used for this research  Kalnik Area of Kalnik is presented with 400 m deep water well (L1) without any influence of agriculture or urbanisation on nitrate concentration in exhausted water. Water samples from this location were used as a control for comparison of nitrate concentration in water from other 2 locations. Area of Kalnik is presented with 400 m deep water well (L1) without any influence of agriculture or urbanisation on nitrate concentration in exhausted water. Water samples from this location were used as a control for comparison of nitrate concentration in water from other 2 locations.  Krizevci Water samples from 2 wells (10-50 m depth) in suburb of Krizevci (L3 i L4) represent an area with possible influence of agriculture combined with inadequate sewerage systems of the households but without possibility for detailed distinction of main source. Water samples from 2 wells (10-50 m depth) in suburb of Krizevci (L3 i L4) represent an area with possible influence of agriculture combined with inadequate sewerage systems of the households but without possibility for detailed distinction of main source.  Koprivnica Area of Koprivnica is presented with 3 wells (10-50 m depth) that are located mainly in area of intensive agricultural production (L2, L5 and L6). Area of Koprivnica is presented with 3 wells (10-50 m depth) that are located mainly in area of intensive agricultural production (L2, L5 and L6).

7. LOCATIONS OF WELLS INCLUDED IN MONITORING  Ground water samples were collected weekly on described locations (L1-L6) in the period from April 1st 2005 to April 1st 2006  Immediately after sampling samples were stored in 1 L plastic bottles at temperature between 4°C to 6°C  Method used for analyses was Ion chromatography (HRN ISO 10304-1:1998)

8. IC system-Dionex DX 500  gradient pump GP 40  autosampler AS 40  chromatographic compartment LC 20 compartment LC 20  conductivity detector CD 20  chemical suppression was performed by using Dionex ASRS-ULTRA 4 mm suppressor  entire system was controlled by Dionex Peak Net 5.2 software.  for separation Dionex Ion Pac AS-9-HC analytic column (4x250 mm) and suitable guard column Ion Pac AG 9-HC (4x50mm) have been used

9. RESULTS AND DISCUSSIONS Sources of nitrogen from mineral and organic fertilizers in study area are calculated for the year 2000 Sources of nitrogen from mineral and organic fertilizers in study area are calculated for the year 2000 Compared to the average nitrogen use in whole Croatia it is evidently an area with relatively high consumption of nitrogen Compared to the average nitrogen use in whole Croatia it is evidently an area with relatively high consumption of nitrogen Average data on nitrogen consumption can be useful for rough estimation of possible influence of agriculture to groundwater pollution with nitrate Average data on nitrogen consumption can be useful for rough estimation of possible influence of agriculture to groundwater pollution with nitrate Mineral fertilizers Organic fertilizers Total nitrogen AREA kg N / ha agricultural land Koprivnica- Krizevci county 6759126 Croatia351954

10. Average nitrogen load from mineral and organic fertilizers for year 2000.

11. Nitrogen balance, 2000.

12. Nitrogen balance, 2001.

13. Nitrogen balance, 2002.

14. Nitrogen balance, 2003.

15. Nitrogen balance, 2000 – 2003.

16. Nitrate concentrations in single water samples from 3 different locations in Koprivnica-Krizevci County At location Kalnik nitrate concentration in water from deep well was almost constant and it was relatively low. At location Kalnik nitrate concentration in water from deep well was almost constant and it was relatively low. According to the single measurements of nitrate concentration in water samples from shallow wells in locations Krizevci and Koprivnica values were much higher compared to the location Kalnik and differences in nitrate concentration between individual samples relatively high According to the single measurements of nitrate concentration in water samples from shallow wells in locations Krizevci and Koprivnica values were much higher compared to the location Kalnik and differences in nitrate concentration between individual samples relatively high

17. Average monthly values of nitrate concentration some differences between locations can be defined some differences between locations can be defined at location Krizevci average monthly nitrate concentration in water decreased from April to December. In period from January to March nitrate concentrations start to grow again and they were increased, compared to the previous months. at location Krizevci average monthly nitrate concentration in water decreased from April to December. In period from January to March nitrate concentrations start to grow again and they were increased, compared to the previous months. at location Koprivnica nitrate concentrations grow from April to September and after that period they start to fall. at location Koprivnica nitrate concentrations grow from April to September and after that period they start to fall.

18. The results of analysis of variance Average NO3- concentration in water from monitored wells it is evidently that statistically significant differences exist between locations in Kalnik, Krizevci and Koprivnica it is evidently that statistically significant differences exist between locations in Kalnik, Krizevci and Koprivnica average nitrate concentrations in water samples from location Krizevci and Koprivnica are significantly higher from average concentration in water from location Kalnik average nitrate concentrations in water samples from location Krizevci and Koprivnica are significantly higher from average concentration in water from location Kalnik there is no statistically significant difference between nitrate concentration in average water samples form locations Krizevci and Koprivnica there is no statistically significant difference between nitrate concentration in average water samples form locations Krizevci and Koprivnica the highest average nitrate concentration is related to location Koprivnica, which is the area of intensive agricultural production the highest average nitrate concentration is related to location Koprivnica, which is the area of intensive agricultural production LocationWell Nitrate concentration,mg/l KalnikL14,6 KrizevciL3,L426,5 Koprivnica L2, L5, L6 28,7 LSD 0,05 % 4,3 LSD 0,01 % 5,9

19. Differences in average nitrate concentration can be explained with: different depths of water extraction agricultural nitrogen application individual home sewage disposal systems

20. Differences in average nitrate concentration can be explained partly with: Kalnik – high depth of water extraction Krizevci - stronger influence in nitrate enrichment can be given to households and their septic tank systems Koprivnica - agricultural application of mineral and organic fertilizers is most probably the main source of water pollution with nitrates

21. CONCLUSIONS The findings confirm that nitrate concentrations in water samples from wells in 3 different locations in Northwest Croatia are significantly different The highest average nitrate concentration of 28.7 mg L- 1 NO3- is related to location Koprivnica, which is the area of intensive agricultural production At location Krizevci wells are located at suburban area and average nitrate concentration is 26.5 mg L-1 NO3- Compared to this two values significantly lower average concentration of 4.6 mg L-1 NO3- is determined at location Kalnik in water samples without any influence of agriculture and urbanisation