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[VD05] Nitrates in groundwater
State

Key message
Neutral

Slovenian groundwater bodies most polluted with nitrates are those with intergranular (alluvium) aquifers, particularly in north-eastern Slovenia. Groundwater in karst and fractured aquifers is less burdened with nitrates due to geographical conditions, low population density and less agricultural land. In the period 1998–2019, the average annual levels of nitrates in water bodies in the Sava valley, Ljubljansko barje, Savinja, Drava and Mura basins show a statistically significant downward trend. In other water bodies, nitrate levels are not statistically significant.

This indicator shows the concentration of nitrates in groundwater samples. Mean annual values for individual measuring sites, water bodies in Slovenia and Europe, were calculated.

Nitrates can be naturally present in groundwater. Natural background concentrations of nitrates depend on geological properties of aquifers – in Slovenia, they are below 10 mg NO3/l. Increased concentrations of nitrates in groundwater are a result of human activities, agriculture in particular. Nitrates can also appear in groundwater as a consequence of improper urban wastewater management. In Slovenia, groundwater represents the main source of drinking water.

Charts

Figure VD05-1: Average annual values ​​of nitrate in groundwater samples at the sampling points of the Slovenian national monitoring in 2019
Sources:

Standardised Database for Water Quality Monitoring, Slovenian Environmental Agency, 2020

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Figure VD05-2: The average value of nitrate levels in Europe and in Slovenia and Slovenian groundwater bodies with predominantly intergranular (alluvial) and karst/fractured aquifers
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Slovenija - alluvial aquifers[mg/l] Slovenia - karst-fractured aquifers[mg/l] Slovenia - average[mg/l] Europa - average[mg/l]
2004 40.56 7.48 15.36 20.04
2005 40.29 7.39 15.23 19.72
2006 38.59 7.41 14.84 19.50
2007 31.75 7.33 13.15 19.27
2008 32.77 6.78 12.97 19.20
2009 32.87 6.58 12.84 19.12
2010 31.95 5.50 11.80 19.28
2011 31.20 6.60 12.50 19.28
2012 30.20 5.36 11.28 19.28
2013 32.30 5.27 11.70 19.28
2014 32.21 5.27 11.69 19.28
2015 31.05 5.78 11.80 19.28
2016 25.35 5.50 11.44 19.28
2017 31.73 5.90 12.05 19.28
2018 31.95 5.61 11.88 19.28
2019 30.11 5.78 11.57 19.28
Figure VD05-3: Average annual nitrate levels in groundwater of the more polluted water bodies
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1001 Savska kotlina in Ljubljansko barje[mg/l] 1002 Savinjska kotlina[mg/l] 1003 Krška kotlina[mg/l] 3012 Dravska kotlina[mg/l] 4016 Murska kotlina[mg/l] quality standard[mg/l] [ ]
1998 23.39 50.01 21.84 45.10 47.63 50 1
1999 22.80 43.78 23.80 48.37 39.75 50
2000 21.64 47.21 20.39 45.44 47.34 50
2001 21.94 55.49 25.68 46.46 50
2002 20.68 43.88 32.96 39.70 34.43 50
2003 20.70 50.45 22.34 40.29 39.86 50
2004 20.90 65.03 29.44 49.45 37.98 50
2005 22.90 57.83 24.76 54.01 41.99 50
2006 22.70 45.37 26.94 53.25 44.67 50
2007 18.38 47.29 21.10 39.12 32.88 50
2008 19.57 48.65 23.16 40.28 32.20 50
2009 20.63 44.83 24.19 42.13 32.57 50
2010 19.21 42.52 24.05 42.18 31.78 50
2011 19.20 43.20 21.60 39 32.90 50
2012 18.23 46.91 23.66 35.56 26.65 50
2013 18.93 40.24 28.67 42.31 31.36 50
2014 18.80 43.98 24.52 40.00 33.73 50
2015 17.96 44.66 23.64 40.27 28.73 50
2016 16.75 42.02 24.53 38.51 30.32 50
2017 16.83 49.85 24.13 39.09 28.75 50
2018 18.78 44.41 25.71 39.66 31.19 50
2019 17.46 47.75 21.85 36.11 27.37 50
Figure VD05-4: The declining trend of the nitrate concentration in water bodies Sava, Mura, Drava and Savinja basin in the period 1998-2019
Sources:

Enotna zbirka podatkov monitoringa kakovosti voda (2020)

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Figure VD05-5: Structure of agricultural land use in 2018 and groundwater quality by water bodies in 2019
Sources:

Environmental Agency of the Republic of Slovenia, 2020. Agricultural Institute of Slovenia (2020)

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Figure VD05-6: Share of agricultural area in the surface of ground water bodies in Slovenia in 2018 (%)
Sources:

Ministry of Agriculture, Forestry and Food (2020)

Note:

Red coloured bars denote ground water bodies with poor chemical state because the nitrate concentration limit is exceeded.

Figure VD05-7: Total nitrogen emissions from municipal wastewater treatment plants (t / year)
Sources:

Waste Water Treatment Plants Database, Environmental Agency of the Republic of Slovenia (2020)

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Indirect outflow into groundwater[t/year] Outflow into surface waters[t/year]
2010 5.90 1993.30
2011 6.60 2011.40
2012 3.40 1710.40
2013 2.40 1707.10
2014 4.50 1634
2015 5.90 1502
2016 9.70 1321.40
2017 9.90 1315.50
2018 12 1388.60
2019 12.80 1283.10

Goals

  • To improve the state of the water environment
  • To reduce emissions from dispersed sources (intensive agriculture, dispersed settlement without wastewater treatment)
  • To achieve a favourable state of groundwater by 2015
  • To reduce concentrations of nitrates in overburdened groundwater below 50 mg NO3/l and to reverse the trends of increasing nitrate concentrations

 

Methodology

Date of data source summarization
Last modified
10.20.2020
Author(s)

Polona Mihorko, Marina Gacin, Marjan Zajc Slovenian Environment Agency, Janez Sušin, Agricultural Institute of Slovenia