UNECE Workshop on Atmospheric Ammonia: Detecting emission changes and environmental impacts Mark Sutton, Emma Giles, Sam Baker

UNECE Ammonia Workshop: Objectives Address 4 specific ammonia questions for the Convention on Long Range Transboundary Air Pollution (CLRTAP) Link contributions from 4 Bodies under the Convention: –Expert Group on Ammonia Abatement (EGAA) –Task Force on Measurement and Modelling (TFMM) –International Cooperative Program (ICP) on Mapping and Modelling (ICP-M&M) –Agriculture and Nature Panel of the Task Force on Emission Inventories and Projections (TFEIP) First workshop to link the ammonia interests of all these groups under the Convention.

Coordinates Edinburgh 4-6 December 2006 Hosted at the Scottish Executive 80 Experts from 19 parties to the CLRTAP Funded and organized by:

Objective 1: Ammonia Critical Level To assess the extent to which the existing critical thresholds for ammonia reflect current scientific understanding: a) Case for setting new ammonia critical threshold(s) based on current evidence of direct impacts of ammonia on different receptors; b) Extent of differential sensitive to ammonia versus other forms of reactive N; c) Debate the case for establishing air concentration limits for indirect effects of ammonia, which would be consistent with current critical loads for nitrogen.

Objective 2: Trends and Ammonia Gap To assess the extent to which independent atmospheric measurements can verify where regional changes in NH 3 emissions have and have not occurred: a) Extent to which regional changes in ammonia emissions have been reflected in measurements of ammonia and ammonium in the atmosphere; b) Distinguish cases where the estimated changes are due to altered sectoral activity or the implementation of abatement policies to see if atmospheric measurements verify the ammonia abatement policies; c) Make recommendations for future air monitoring and systems for assessing the national implementation of ammonia abatement policies and consider the implications of any non-linearities

Objective 3: Ammonia Hot Spots To review approaches for downscaling transboundary assessments to deal with ammonia hotspots in relation to operational modelling and monitoring: a) Review current emission and atmospheric dispersion modelling methods for downscaling NH 3 dispersion and deposition in hot spots; b) Examine the status of methods for effect assessment and air monitoring in NH 3 hot spots; c) Recommend broad principles for assessment of ammonia hot spots, including interactions between transboundary ammonia emission reduction targets and other policy measures.

Objective 4: Mesoscale modelling of ammonia To review mesoscale atmospheric transport and chemistry models in relation to their formulation and results for ammonia: a) Review emission parameterizations used in the models, establishing comparability, spatial and temporal resolution and uncertainties; b) Review dispersion, air chemistry and deposition formulations identifying key differences and uncertainties; c) Assess the overall performance of the models against measurements, giving model recommendations and implications of non-linearities for integrated assessment models.

Recipe 2 discussion documents 4 background documents (1 for each objective) Add experts, with a pinch of stakeholders Lock participants in a room for a day Remix half-way adding 2 cross-cutting groups: –Reliability of ammonia emission and abatement efficiencies –Ammonia policy context and future challenges Cook overnight and distil the conclusions.

Conclusions: Ammonia Critical Levels Current UNECE Critical Levels: –8  g m -3 annual mean –23  g m -3 monthly mean –270  g m -3 daily mean –3300  g m -3 hourly mean Out of date, based mainly on data from 1980s. New evidence from field surveys and experiments: The old values are not sufficiently precautionary Effects accumulate for periods longer than 1 year.

Critical Levels for Ammonia Evidence from UK, CH, PT and IT. (NL is too polluted to derive the CLE). Long Term Critical Level, cannot be assumed to protect for >20-30 years. Critical level for lichens, bryophytes and ecosystems where these are important to ecosystem integrity: 1  g m -3 Critical level for higher plants, inc. woodland ground flora: 3 [2-4]  g m -3

Detecting changes in ammonia There had been an “ammonia gap” in the Netherlands. Was the gap fixed? Long term measurements now follow the emission trend in NL and DK. Part of the gap is closed. However, there remains an absolute gap of in the Netherlands. Air measurements still 30% higher than estimated by emission driven models. Causes? Underestimation of NL emissions or overestimation of dry deposition.

Ammonia gap in eastern Europe Major modelled reduction in NH 3 emissions since In general difficult to match the reduction in atmospheric measurements The trends confounded by major reductions in SO 2 emissions, which have maintained NH 3 levels higher than expected and decreased NH 4 aerosols substantially.

Effect of SO 2 on NH 3 trends in East Europe K-puszta, Hungary compared with the EMEP model L. Horvath et al. Edinburgh poster.

Ammonia Hotspots Assessing ammonia in hotspots remains an issue of high uncertainty, esp. emissions and dry deposition. Need better knowledge on compensation points, surface resistances, and dependence on climatic variables and deposition history. It was concluded that there is potential for local “landscape models” to develop local “tailored” abatement measures, as well as to quantify sub- grid variability.

Dealing with spatial scale European exceedances of the critical load for nitrogen National targets and policy Ecosystem protection

Regional modelling of ammonia Six models from national to regional (European) scale were reviewed. Estimates of wet deposition and aerosol NH 4 + concentrations generally adequate. All European scale models currently underestimated ground level NH 3 concentrations, but better agreement in national models. Key uncertainties linked to emissions, dry deposition, spatial resolution and description of vertical diffusion. None of the models routinely included compensation points, and a more comprehensive database was needed.

Regional modelling of ammonia Differences in the model performance between countries are not fully understood: –(i) the quality of the ammonia emissions inventory, –(ii) differences in the model parameterization schemes, –(iii) geographical differences (climate, terrain) or –(iv), differences in measurement datasets. Hence, a coordinated comparison of regional atmospheric ammonia models, using a common model domain, input database and measurement database, is urgently needed to assess relative model performance. In many countries, better data are available for national modelling efforts than are submitted to EMEP. The reporting to EMEP has to be more flexible to improve data availability.

Reliability of ammonia emssions and abatement efficiencies Few countries had considered uncertainty in ammonia emissions inventories. Conclude +/- 20% at best, but if non-local emission factors used can be c. 100%. Major uncertainty to uncertain and missing data on farming practices, inc. timing, management, diets etc. UNECE guidance on abatement efficiencies is considered robust. Only general guidance on pollution swapping as very variable by site conditions.

“Soft approaches” to ammonia abatement, through best management practices (BMP). Economically attractive, but dificult to quantify the benefits. Need to be able to measure better the achievement for national reporting. Ex ante assessments tend to overestimate abatement costs, although measures may not be as effective when applied in practice. Reliability of ammonia emssions and abatement efficiencies

Policy context and future challenges potential role of policy options to help mitigate ecosystem and health impacts of ammonia emissions were addressed Ammonia policies are interlinked with other environmental and agricultural policies. In order to avoid the problem of “pollution swapping”, future policies needed to consider the interactions In responding to the EU nitrate directive or biodiversity- related directives, farmers in certain areas adjusted agricultural practices, although there was little knowledge of the environmental consequences.

Changed annual NH 3 profile in Denmark

Give further consideration to how the new critical levels will be used in addition to critical loads in formulating air pollution targets. The role of air pollution effects is often not explicitly taken into account even though nitrogen inputs have a large effect on biodiversity: there is room for improvement on local, national and European levels. Ammonia emission reduction policies must be analysed in a: –multi-effect (human health, greenhouse balance, acidification and eutrophication and related biodiversity loss), –multi-media (air, water, soil), –multi-scale (hot spots, regional, European, global) framework. Policy context and future challenges