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Atmospheric Ammonia in Coastal Areas Erik Noordijk Atmospheric Ammonia in Coastal Areas | 14 May 2014

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RIVM publication of nitrogen deposition Atmospheric Ammonia in Coastal Areas | 14 May 2014 2 Modelcalculations calibrated on 8 monitoring sites: is this map correct?

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The MAN network (Monitoring Ammonia in Nature) Gradko samplers Monthly sampling by volunteers in nature Monthly calibration on 6 Amanda sites Atmospheric Ammonia in Coastal Areas | 14 May 2014 3

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MAN measurements of ammonia Measured ammonia shows the same spatial pattern of modeled ammonia High concentrations in centre, southeast and east Low concentrations near the coast Atmospheric Ammonia in Coastal Areas | 15 May 2014 4

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Performance model in detail Coastal areas show measured ammonia to be up to 4 times higher than OPS-model What is the reality? Model or measurement? Atmospheric Ammonia in Coastal Areas | 15 May 2014 5

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Further validation of Gradko samplers MAN Alpha samplers are more sensitive and more reliable Good agreement Gradko and alpha The measurements are good, the model is flawed near the coast Atmospheric Ammonia in Coastal Areas | 14 May 2014 6

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MAN monitoring setup across the coast Atmospheric Ammonia in Coastal Areas | 15 May 2014 7

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Transect model versus MAN Atmospheric Ammonia in Coastal Areas | 14 May 2014 8 Many MAN-analyses indicate: sea = source of ammonia Summer: monthly averages up to 5 g/m 3 higher due to the sea

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Evaporation of NH 3 from seawater calculation based on: seawater: measurements of NH 3, NH 4 +, Temperature and pH air: assumptions on windspeed and NH 3 Atmospheric Ammonia in Coastal Areas | 14 May 2014 9

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Other emission mechanisms Seaspray ammonia (seasalt as a proxy): emission is negligible Influence of algae: Algae growth: uptake of N increase pH during algae growth: more NH 3 (gas), less NH 4 + Algae decay: release of N Role of algae in emission is qualitatively plausible, but biology is more complex than just chemical equilibria (too complex yet for causal model) Atmospheric Ammonia in Coastal Areas | 14 May 2014 10

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Atmospheric Ammonia in Coastal Areas | 15 May 2014 11

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Basic assumption Algae grow where nutrients (ammonium) are available Good correlation (R 2 0.67) between algae and NH 3 in the North Sea Atmospheric Ammonia in Coastal Areas | 14 May 2014 12

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Algae as proxy for ammonia emission Map of Chlorophyll-a from sealevel-calibrated satellite data Copyright Van der Woerd en Pasterkamp, 2008 Atmospheric Ammonia in Coastal Areas | 14 May 2014 13

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Emission calculation: a pragmatical approach Fill the gap between measurement & model with an emission estimate BASIC ASSUMPTIONS: Ammonia emission is proportional to chlorophyll-a concentration (the chlorophyll map gives the spatial emission distribution) Total ammonia emission from the sea: fill the gap between modeled and measured coastal ammonia (a simple fitting procedure) based on yearly averages (seasonal behaviour is too complex, not supported by enough data) Atmospheric Ammonia in Coastal Areas | 14 May 2014 14

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Results: NH3 from the sea Concentration (g/m 3 per year) Deposition (mol/ha per year) Atmospheric Ammonia in Coastal Areas | 14 May 2014 15

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Results per type of area Atmospheric Ammonia in Coastal Areas | 14 May 2014 16

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Results per location type R 2 total is 0.76, R 2 central sites is 0.87 Atmospheric Ammonia in Coastal Areas | 14 May 2014 17

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Emission totals: are they plausible? Dutch 20 km coastal zone: 10 kton/year NH 3 (97 % of the calculated seaborne NH 3 over Holland) Atmospheric Ammonia in Coastal Areas | 14 May 2014 18

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Emission totals: are they plausible? Dutch 20 km coastal zone: 10 kton/year NH 3 (97 % of the calculated seaborne NH 3 over Holland) Dutch emission 2011: 119 kton Nitrogen load Rhine river: about 150 kton/year Atmospheric Ammonia in Coastal Areas | 14 May 2014 19

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Emission totals: are they plausible? Dutch 20 km coastal zone: 10 kton/year NH 3 (97 % of the calculated seaborne NH 3 over Holland) Dutch emission 2011: 119 kton Nitrogen load Rhine river: about 150 kton/year Literature values: W. Asman: cruise North Sea 1989 emissions based on:measured NH 3 NH 4 + in seawater and air assumed pH T this studyAsman (g/s per km 2 ) 20km zone / estuarium0.020.0085 Atmospheric Ammonia in Coastal Areas | 14 May 2014 20

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Conclusions Measurements indicate that near the Dutch coast the sea contributes more to atmospheric NH 3 than anthropogenic emissions to air No quantitative causal emission estimate (reality is too complex yet) Pragmatic approach algae proxy - gives satisfying results Atmospheric Ammonia in Coastal Areas | 14 May 2014 21

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Conclusions Measurements indicate that near the Dutch coast the sea contributes more to atmospheric NH 3 than anthropogenic emissions to air No quantitative causal emission estimate (reality is too complex yet) Pragmatic approach algae proxy - is satisfying LIMITATIONS OF THE STUDY A causal model is needed for projections, we only describe the present Tidal waters / estuaria are still a problem, not included in this study Other parts of the North Sea: need for measurements in other countries to validate / expand the model Atmospheric Ammonia in Coastal Areas | 14 May 2014 22