Ammonia: emission, atmospheric transport and deposition

Abstract

The global emission of ammonia (NH $ ) is about 54 Mt N. The major global sources are excreta from domestic animals and fertilizers, but oceans, biomass burning and crops are also important. About 60 % of the global NH $ emission is estimated to come from anthropogenic sources. NH $ -N emissions are of the same order as the NO x -N emissions on both global and European scales. Emitted NH $ returns to the surface mainly in the form of dry deposition of NH $ and wet deposition of ammonium (NH % + ). In countries with high NH $ emission densities, dry deposition of NH $ from local sources and wet deposition of NH % + from remote sources dominate the deposition. In countries with low NH $ emission densities only wet deposition of NH % + from remote sources dominates the deposition. Surface exchange of NH $ is essentially bi-directional, depending on the NH $ compensation point concentration of the vegetation and the airborne concentration. In general, the compensation point is larger for agricultural than semi-natural plants, and varies with plant growth stage. According to basic thermodynamics the leaf tissue or stomatal compensation point of NH $ doubles for each increase of 5 mC. However, exchange of NH $ does not only occur through the stomata, but it can also be deposited to leaf surfaces, as well as emitted back to the atmosphere from drying leaf surfaces. Atmospheric transport and deposition models can be used to interpolate NH $ concentrations and depositions in space and time, to calculate import\export balances and to estimate past or future situations. Adverse effects on sensitive ecosystems caused by high N deposition can be reduced by lowering the emissions and, to a limited extent, also by removing sources close to the ecosystem to be protected.

Heterogeneity of atmospheric ammonia at the landscape scale and consequences for environmental impact assessment

“…The contribution of particulate ammonium (NH 4 + ) to the dry deposition of reduced N is considered minor compared with NH 3 (e.g. Asman et al, 1998;Duyzer, 1994). Hallsworth et al (2010) validated the FRAME model at a 1 km resolution for NH 3 concentrations and Dore et al (2012) for NO 2 concentrations.…”

Impacts of tropospheric ozone and airborne nitrogenous pollutants on natural and semi‐natural ecosystems: a commentary

“…Because of short-range and long-range transport, atmospheric N deposition has increased in many natural and semi-natural ecosystems. In contrast to the estimated background inputs of 1-5 kg N ha −" yr −" early in this century, N deposition can be 20-60 kg N ha −" yr −" in non-forest ecosystems in Europe (Bobbink & Heil, 1993 ;Asman et al, 1998 ;Fowler et al 1998). The availability of nutrients is an important factor in the determination of species composition, and N is the growth-limiting nutrient in many natural and semi-natural ecosystems of high conservation value, especially in oligotrophic and mesotrophic conditions.…”

“…Air pollutants are transported over both short and long distances (as far as a few thousand km) before being deposited on surface water, vegetation or soil. In this way, vegetation over a large area or in remote regions can be influenced by airborne pollutants (see Fowler et al (1998) ;Asman, Sutton & Schjørring (1998)). …”

On-Road Measurement of Ammonia and Other Motor Vehicle Exhaust Emissions

“…Most internal combustion processes also produce ammoma, though the amount of ammonia produced is typically small compared to the other sources men~oned above (11)(12)(13) Ammoma emissmns from catalyst eqmpped vehicles have been shown m laboratory d~amometer studies to be dramaucaUy hagher than for precatalyst vehicles (5, 14, 1.5). The producUon of ammoma can be increased flLrther if the engine runs fuel-nch, because that conchuon favors reducing processes on the catalyst surface (5,14,15).…”