Acid rains date back to the 19thcentury Industrial Revolution, which brought with it powerful increasein coal combustion and sulphur emissions. In the atmosphere, sulphurcompounds are oxidised to SO3 and react with water to producesulphuric acid (VI), producing acid rains (pH <4.5). Today, althoughthe levels of sulphur compounds in the air are much lower, acid rainscontinue. Large volumes of acidifying gases, ammonia and nitrogen oxidesare believed to be the cause. These compounds are released when animalfertilisers are used in quantities exceeding plant uptake, and underspecific animal rearing conditions (emissions from livestock buildings).
Interms of emission volumes, ammonia is one of the major contributors torain acidification. It forms ammonium salt aerosols, including NH4NO3 and (NH4)2SO4, which have a significant rain acidification effect. Ammonia has the same rain acidification potential as SO2 and twice as high as NO2.
Ammoniaproduced from agriculture is believed to be responsible for around 30%of total rain acidification. Ammonia is produced in the decompositionprocess of protein compounds (ammonification) and is very toxic forhumans, animals, plants, soil and aquatic ecosystems. Livestockproduction has the highest share in overall ammonia emissions (65-70%,agriculture ?80-90%), ammonia is released from livestock buildings,natural fertilisers storage installations, and during landspreading.Ammonia emissions to a large extent depends on the animal rearing system? the highest ammonia emissions are generated by non-litter systems(slurry producing systems), and are lower in systems with deep litter.
Enzymaticand anaerobic decomposition of excreta, urine and feed is the mainsource of ammonia released from livestock buildings. In the case ofanimals which excrete urea (cattle, sheep, goats, swine, fur animals),total enzymatic decomposition of ammonia takesplace, with gaseousammonia released to the atmosphere and transformed into nitrates. Animalexcreta contain organic nitrogen compounds which are progressivelymineralized by anaerobic bacteria. Nitrogen contained in poultry litteris solid (uric acid) and is decomposed by bacteria and enzymes. It isestimated that dairy cattle releases 27.8 kg NH3/year, swine ? 5,1 kg NH3/year, sheet or goat ? 1.9 kg NH3/year, poultry ? 0.26 kg NH3/year, horse ? 12.5 kg NH3/year.In 2009, ammonia release from agriculture totalled 268,000 tons.Ammonia input to the Baltic Sea due to atmospheric deposition amountedto around 92,000 Mg in 2005 (44% of total nitrogen input fromatmospheric deposition).Poland, apart from Germany and Denmark, isthe biggest contributor of ammonia input to the Baltic Sea.
Ammoniaconcentration in livestock buildings is 5 - 10 ppm, and can reach 100ppm in poultry housings and during livestock waste removal from cattleand swine buildings. In general, ammonia concentrations depend ontemperature, animal rearing system, livestock size, ventilation system,type of feed, and feeding methods.
Ammoniareleased to the atmosphere is washed down with precipitation, causingsurface water pollution (eutrophication), soil acidification, andcontributes to the dissolution and leaching of nutrients from soil. Dueto toxicological (health-related) and ecological (environmental) risks,restrictions on ammonia production have been imposed under national andinternational laws (maximum concentration of NH3 in thenatural environment, workplaces, livestock housing, and residentialhousing; the Helsinki Conventions established an obligation to reduceammonia emissions from livestock housings and livestock waste deposition sites).