Modelling the concentration of ammonia and exceedance of the critical level in the UK

Tony Dore1, Jane Hall2, Ed Carnell1, Sam Tomlinson1, Ulli Dragosits1,

Sim Tang1, Amy Stevens1, Christine Braban1, Oliver Pescott3,

Ron Smith1, Massimo Vieno1, Bill Bealey1, Stefan Reis1, Mark Sutton1,

1 Centre for Ecology & Hydrology, Edinburgh, Scotland, UK2 Centre for Ecology & Hydrology, Bangor, Wales, UK3 Centre for Ecology & Hydrology, Wallingford, England, UK

International Cooperative Programme on Modelling and Mapping of

Critical Levels & Loads and Air Pollution Effects, Risks and Trends (ICP M&M)

CEH Wallingford, Tuesday 4th – Thursday 6th April 2017

Is NH3 a risk to natural ecosystems in the UK?

2014 UK Ammonia emissions

NH3 source contribution (%)

Dominant NH3

emissions source

UK National Atmospheric Emissions Inventory

http://naei.defra.gov.uk/

SO2NH3 NO

H2SO4

(NH4)2SO4

NO3-(aq)

NO2

HNO3 NO3

PAN

SO42-

(aq)

NH4 NO3

NH4+

(aq)

*

*

*

*

*

*

*

*

*

Ra

Rb

Rc

Dry

deposition

Wet

deposition

Turbulent

mixing

Particle formation

Emission of gases

Processes parameterised in the FRAME Atmospheric Chemistry Transport Model

HNO3

SO2

NH3

Defra Model inter-comparison

surface ammonia concentrations for the year 2003

Carslaw D (2011) Defra deposition model evaluation – Phase 1https://uk-air.defra.gov.uk/research/air-quality-modelling?view=intercomparison

Dore, A.J., D. Carslaw, C. Braban, M.Cain, C. Chemel, C.Conolly, R.G. Derwent, S.J. Griffiths, J. Hall, G. Hayman, S. Lawrence, S.E. Metcalfe, A. Redington, D. Simpson, M.A. Sutton, P. Sutton, Y.S. Tang, M. Vieno, M. Werner, J.D. Whyatt (2015) Evaluation of the performance of different atmospheric chemical transport models and inter-comparison of nitrogen and sulphur deposition estimates for the UK. Atmospheric Environment 119, 131-143

Model inter-comparison for surface ammonia concentrations for the year 2003

Why does the ‘simpler’ Lagrangian FRAME model obtain good correlation with measurements of NH3

when compared with more state of the art Euerian models (with more complex chemical reactions, surface exchange schemes & dynamic meteorology)?

The simpler Lagrangian model has a fine vertical grid resolution with a 1 m surface thickness layer. Eulerian models have a surface layer depth of typically ~ 100 m.

Eulerian models performed best for particulate NH4 particulates

van der Swaluw E, de Vries W, Vieno M, Sauter F, Aben J, Velders G, Fagerli H, van Pul A (2016) Modelling air quality and deposition at high resolution

in the Netherlands with plume and grid models. Proc. 35th International Technical Meeting on Modelling Air Pollution and its Application

FRAME modelled NH3 concentration for the year 2013

The FRAME model can be run at either a

1 km or 5 km resolution over the UK.

Use of high resolution in the model

allows us to more accurately map NH3

emissions onto the appropriate land

category

This leads to better spatial representation

of NH3 concentrations and improved

correlation with measurements over

semi-natural areas

Hallsworth S., Dore A.J., Bealey W.J., Dragosits U., Vieno M., Hellsten

S.. Tang Y.S. and M.A. Sutton M.A. (2010) The role of indicator choice in

quantifying the threat of atmospheric ammonia to the ‘Natura 2000’

network. Environmental Science and Policy 13, 671-687.

Correlation of 2013 FRAME modelled NH3

concentrations with measurementsUK National Ammonia Monitoring Network

Delta sampler

Can we ‘correct’ modelled NH3 concentrations for

under/over-estimate?

Linear regression line of best fit is heavily

influenced by high concentration outliers.

Normalised Mean Bias (NMB) is also influenced by

outliers at higher concentrations

Mean Normalised Bias (MNB) is influenced by

lower concentrations (where the model tends to

over-estimate)

Use the median bias = 0.46

Combining the results of model and measurements

Model bias for annually averaged

concentrations 2012-2014

1

𝑁𝑀𝐵 = 𝑀𝑖 − 𝑂𝑖

𝑛

𝑖=1

𝑂𝑖

𝑛

𝑖=1

2 𝑀𝑁𝐵 = 1/𝑁

𝑖=1

𝑛

(𝑀𝑖 − 𝑂𝑖) 𝑂𝑖

National critical level exceedance

1 mg m-3 critical level

lichens & bryophytes

3 mg m-3 critical level

all other vegetation

Broad habitat critical level exceedance

1 mg m-3 critical level

3 mg m-3 critical level

FRAME modelled 2012-2014

NH3 concentration

Critical level exceedance metrics

Metric Percentage area exceeding NH3 critical level of:

1 µg m-3 3 µg m-3

% UK land area 60 2.7

% N-sensitive habitats 22 0.5

% SACs 58 5.4

% SPAs 50 6.1

% SSSIs 68 2.7

Bryophyte species richness (hectad-1) adjusted for

estimated recording effort using Frescalo algorithm

(Hill, 2012) Bryophyte species

richness in areas

with NH3 > 1 mg m-3

1 Ulli Dragosit presentation: Historical trends in nitrogen and sulphur deposition in the UK: 1800 to present2 Tang et al (2017) Drivers for spatial, temporal and long-term trends in atmospheric ammonia and ammonium in the UK. Atmospheric Physics and Chemistry (under review)

Recent trend in average UK NH3 concentrations

FRAME model (LTLS NERC project1) National Ammonia Monitoring Network

(Tang et al, 20172)

Model shows little change in NH3 concentration between 1990 and 2010 though emissions fell by 20%

No statistical change in NH3 concentrations (1998-2014) from UK monitoring data

Why have NH3 concentrations not fallen during the last two decades?

Statistical analysis of data from the UK NH3

monitoring network showed no trend in

average NH3 concentrations from 88 sites

during the period 1998-2014

1990 - 2015 Trends in SO2 and NOx emissions in the UK

UK National Atmospheric Emissions Inventory http://naei.defra.gov.uk/

SO2 NOx

between 1970 and 2015: SO2 emissions fell by 93% NOx emissions fell by 70%

The availability of acidic gases (H2SO4, HNO3) in the atmosphere to react with NH3 was depleted

Future emissions predictions for 2030 (further reductions in NOx & SO2

emissions, little change in NH3 emissions) suggest NH3 concentrations will increase

The overall trend is for increasing NH3 and decreasing NH4 particulate concentrations

Nitrogen deposition is shifting from long range wet deposition to local NH3 dry deposition

Conclusion

The FRAME model shows reasonable agreement with measured NH3 concentrations

The 1 mg m-3 critical level for NH3 is exceeded over 60% of the UK

Concentrations are highest in the agricultural areas of England and Northern Ireland

NH3 concentrations have shown little change since peak emissions in 1990 till 2010

according to both the model and monitoring network

The model estimates a doubling of NH3 concentrations between 1970 and 2030 due

to a major decrease of acidic gases (H2SO4, HNO3) in the atmosphere

Future Work

Moss and liverwort epiphyte recovery

Make use of lichen data and refine species richness to N-sensitive species

Establish historical impacts on distribution of lichens and bryophyte richness:

Has NH3 caused a reduction in species richness?

FSC guide to lichens and air quality, phone app developed by CEH, NHM & Nottingham University

http://www.apis.ac.uk/nitrogen-lichen-field-manual

Thank you for your attention!

Any questions (on NH3)

Or comments (on vegetation)?

Acknowledgement