Nitrogen pollution of groundwater and surface waters in Thuringia, Germany: Status quo and management options (Germany)

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1 Mitglied der Helmholtz-Gemeinschaft Nitrogen pollution of groundwater and surface waters in Thuringia, Germany: Status quo and management options (Germany) Frank Wendland 1, Frederic Ahrens 2, Peter Kreins 3, Ralf Kunkel 1 & Björn Tetzlaff 1 1: Forschungszentrum Jülich, Agrosphere Institute (IBG-3), Jülich 2: Federal State Agency for Environmentand and Geology Thuringia (TLUG), Jena 3: Thünen-Institut, Institute of Rural Studies (LR), Braunschweig

2 Thuringia Hydrogeology One of the 16 Federal German States, total area: ca km 2 Population: ca. 2.2 Mio. Typical Central German Upland area Geology: consolidated rocks (>95%) Land use: forest 33%, agriculture 55% (concentrated in Thuringian Basin) Groundwater in bad status due to nitrate Black soil in Thuringian Basin is one of the most fertile soils in Europe

3 R&D project on behalf of Federal State Agency for Environment and Geology Thuringia (TLUG) Tasks of R&D - project / structure of talk: Quantification of diffuse and point source N- inputs into groundwater and surface waters based on the simulation tools RAUMIS-GROWA-DENUZ-WEKU (status quo analysis) Assessment of N reduction requirement to reach quality target for groundwater (50 mg/l) Prognosis of effects of agricultural management adaptations and conclusions about reachability of groundwater quality target in Thuringia Funding period ( )

4 Hot-spot areas Simulation tool RAUMIS-GROWA-DENUZ-WEKU Agricultural N-balance surplus (RAUMIS) Land use Disaggregation Immobilization Displaceable N-input into soil Total N-output river / lake Combined sewer systems Separate sewer system Waste water treatment plants Industrial effluents Small sewage treatment plant Bürgermeisterkanäle Point source N-inputs river /lake Total N-input river/lake N-Retention in river/lake Atmospheric N- deposition on land Atmospheric N- deposition river /lake Water balance (GROWA) Diffuse N-input river/lake Erosion Wash-off Drainage Interflow Groundwater N-output from soil Denitrification in soil (DENUZ) N-input into groundwater Denitrification in groundwater (WEKU) Quantification of N-inputs from 6 diffuse sources and 6 point sources Area-covering application (ca km 2 ) Area-differentiated (100 x 100 m grids)

5 Agricultural N balance surplus for agricultural areas (on community level 2015) RAUMIS model result determined by Thünen-Institute (TI) t N/a ~ ca. 35 kg N/ha a Upper limit of N-balance surplus according to German fertilizer ordinance: actually: 60 kg N/(ha a) revised (effective from 2020): 50 kg N/(ha a)

6 Agricultural N balance surplus for agricultural areas (on community level 2015) in different Federal States t N/a ~ ca. 35 kg N/ha a t N/a ~ ca. 71 kg N/ha a t N/a ~ ca. 74 kg N/ha a Results presented LUWQ 2013 Results presented LUWQ 2015

7 Simulation tool RAUMIS-GROWA-DENUZ-WEKU Hot-spot areas Agricultural N-balance surplus (RAUMIS) Land use Disaggregation Immobilization Displaceable N-input into soil Total N-output river / lake Combined sewer systems Separate sewer system Waste water treatment plants Industrial effluents Small sewage treatment plant Bürgermeisterkanäle Point source N-inputs river /lake Total N-input river/lake N-Retention in river/lake Atmospheric N- deposition on land Atmospheric N- deposition river /lake Water balance (GROWA) Diffuse N-input river/lake Erosion Wash-off Drainage Interflow Groundwater N-output from soil Denitrification in soil (DENUZ) N-input into groundwater Denitrification in groundwater (WEKU)

8 Displacable N load in soil Agricultural N-Surpluses t N/a ~ ca. 35 kg N/ha a LN Disaggeration to 100 x 100 m grids N-Immobilization (forest, pasture) ca t/a Atmospheric deposition t N/a / km 2 ~ ca. 29 kg N/ha a t N/a ~ ca. 21 kg N/ha a

9 N output from soil (DENUZ model) Displacable N load in soil Assessment of denitrification in soil based on Michaelis-Menten cinetics: dn dt t D max N k t N t t N/a ~ ca. 29 kg N/ha a N output from soil Denitrification losses in soil: ca t/a N Maximum yearly denitrification rate in soils <20 kg/ha a predominantly (e.g. luvisoils) t N/a ~ ca. 21 kg N/ha a

10 Hot-spot areas Simulation tool RAUMIS-GROWA-DENUZ-WEKU Agricultural N-balance surplus (RAUMIS) Land use Disaggregation Immobilization Displaceable N-input into soil Total N-output river / lake Combined sewer systems Separate sewer system Waste water treatment plants Industrial effluents Small sewage treatment plant Bürgermeisterkanäle Point source N-inputs river /lake Total N-input river/lake N-Retention in river/lake Atmospheric N- deposition on land Atmospheric N- deposition river /lake Water balance (GROWA) Diffuse N-input river/lake Erosion Wash-off Drainage Interflow Groundwater N-output from soil Denitrification in soil (DENUZ) N-input into groundwater Denitrification in groundwater (WEKU)

11 GROWA water balance components (input pathways) Surface runoff Natural interflow Drainage runoff N-output is coupled to runoff components Runoff from urban areas Groundwater recharge

12 STATUS QUO N-inputs into surface waters from 6 diffuse input pathways Wash-off: ca. 40 t/a Erosion: ca t/a Interflow: ca t/a N-Deposition: ca. 174 t/a Groundwater: ca t/a Drainage: ca t/a Hardly any denitrification in groundwater due to oxidizing groundwater conditions

13 Thuringia: N-input into groundwater vs. N-input into surface waters from groundwater Oxidized groundwater prevents denitrification processes in groundwater in Thuringia. Accordingly N-input into the aquifer corresponds to a large extent to the N-input into surface waters from groundwater Oxidized gw Reduced gw In contrast, > 80% of N-input into aquifers are denitrified in the Federal States of Schleswig-Holstein and Mecklenburg- Vorpommern Denitrification in groundwater: < 500 t/a (only)

14 Hot-spot areas Simulation tool RAUMIS-GROWA-DENUZ-WEKU Agricultural N-balance surplus (RAUMIS) Land use Disaggregation Immobilization Displaceable N-input into soil Total N-output river / lake Combined sewer systems Separate sewer system Waste water treatment plants Industrial effluents Small sewage treatment plant Bürgermeisterkanäle Point source N-inputs river /lake Total N-input river/lake N-Retention in river/lake Atmospheric N- deposition on land Atmospheric N- deposition river /lake Water balance (GROWA) Diffuse N-input river/lake Erosion Wash-off Drainage Interflow Groundwater N-output from soil Denitrification in soil (DENUZ) N-input into groundwater Denitrification in groundwater (WEKU)

15 STATUS QUO N-inputs into surface waters from 6 point source input pathways Combined sewer systems: ca. 500 t/a Small sewage treatment plants: 790 t/a Separate sewer systems: ca. 520 t/a Industrial effluents: ca. 50 t/a Wastewater treatment plants: ca t/a Bürgermeisterkanäle : ca. 750 t/a

16 Total N input into surface waters according to input pathways N-input into surface waters via 6 diffuse and 6 point source input pathways: ca t N/a Ca. 10% from point sources, ca. 90% from diffuse sources Inputs via interflow and groundwater predominate Good agreement between modelled and observed N loads in surface waters

17 comparison of displaceable N load in soil to total N input into surface waters for different Federal States Thüringia: from down to t N/a N input into surface waters in Thuringia is higher than in Schleswig-Holstein and Mecklenburg- Vorpommern although the N output from soil was much lower Schleswig-Holstein: from down to t N/a Mecklenburg-Vorpommern: from down to t N/a

18 R&D project on behalf of Federal State Agency for Environment, and Geology Thuringia (TLUG) Structure of talk: Quantification of diffuse and point source N- inputs into groundwater and surface waters based on the simulation tools RAUMIS-GROWA-DENUZ-WEKU (status quo analysis) Assessment of N reduction requirement to reach quality target for groundwater (50 mg/l) Prognosis of effects of agricultural management adaptations and conclusions about reachability of groundwater quality target in Thuringia Funding period ( )

19 Quality target for groundwater Already nitrate in leachate shouldn t exceed 50 mg/l Leachate (root zone) EU groundwater directive: 50 mg/l nitrate in groundwater Positive (side) effects of 50 mg/l nitrate in leachate: groundwater quality target will be reached on the long run in any case Conservation of substances in groundwater involved in denitrification process (e.g. pyrite) Counteract secondary problems for water suppliers due to nitrate pollution of groundwater: Release of Ni, As, Zn etc. from pyrite in denitrification process Precipitation of FeOOH (Goethit) in withdrawal devices Very positive effect with regard to reduction of diffuse N input into surface waters and coastal waters via direct runoff components, above all drainage systems

20 Quality target for groundwater: Already nitrate in leachate shouldn t exceed 50 mg/l (LAWA, 2014) Leachate rate : < > 500 mm/a N-output from soil: t N/a Nitrate concentration in leachate c NO 3 [ mg/ L ] = 443 (N surplus N output denitrification from soil in soil) Infiltration rate [mm/a] [kg N/(ha a)] N reduction need quantified for all agricultural areas showing > 50 mg NO 3 /l in the leachate

21 Required N reduction in agriculture in order to reach 50 mg/l in leachate Required N reduction in agriculture Ca t N/a (~ 45% of actual N-surpluses)

22 R&D project on behalf of Federal State Agency for Environment, and Geology Thuringia (TLUG) Structure of talk: Quantification of diffuse and point source N- inputs into groundwater and surface waters based on the simulation tools RAUMIS-GROWA-DENUZ-WEKU (status quo analysis) Assessment of N reduction requirement to reach quality target for groundwater (50 mg/l) Prognosis of effects of agricultural management adaptations and conclusions about reachability of groundwater quality target in Thuringia Funding period ( )

23 Prognosis of effects of agricultural management adaptations: State-wide limitation of N-balance surplus Down to 60 kg N/(ha a) according to actual German fertilizer ordinance Minimal effects only as actual N balance surpluses are in compliance with upper limit of actual German fertilizer ordinance Ca t N/a Further limitation down to 40 kg N/(ha a) (even beyond revised German fertilizer ordinance which will be effective in 2020) Even a throughout limitation of N-balance surplus to maximal 40 kg N/(ha a) will not be enough to achieve the groundwater quality target. Ca t N/a

24 Reachability of groundwater quality target in Thuringia Highest possible agricultural N-surplus for not exceeding 50 mg/l in leachate Due to low dilution of N output from soil (low leachate rates) only a throughout limitation of N-balance surplus down to max. 20 kg N/(ha a) would be enough to achieve the groundwater quality target (50 mg/l) Agricultural N balance surpluses however are in compliance with German Fertilizer ordinance Agriculturally productivity very high (black soils) Well, and now?

25 What are the options (I)? 1. Further reduction of agricultural N-balance surplus (down to kg N/ha a): Maybe a logical step forward with regard to successful EU-WFD implementation unacceptable for agriculture as far beyond the requirements of the German fertilizer ordinance (N surplus of 60 (50) kg N/ha a) 2. Proofing evidence that the reachability of the quality target is not possible due to natural site conditions in spite of successfully implemented N reduction measures: long residence times another delay low leachate rates justify less stringent nitrate quality targets (> 50 mg NO3/l)? business as usual : to be with avoided with regard to successful EU-WFD implementation 3. Integration of the targets of EU-WFD and EU - nitrate directives?

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