Effects of Agriculture upon the Air Quality and Climate: Research, Policy, and Regulations

Abstract

Scientific assessments of agricultural air quality, including estimates of emissions and potential sequestration of greenhouse gases, are an important emerging area of environmental science that offers significant challenges to policy and regulatory authorities. Improvements are needed in measurements, modeling, emission controls, and farm operation management. Controlling emissions of gases and particulate matter from agriculture is notoriously difficult as this sector affects the most basic need of humans, i.e., food. Current policies combine an inadequate science covering a very disparate range of activities in a complex industry with social and political overlays. Moreover, agricultural emissions derive from both area and point sources. In the United States, agricultural emissions play an important role in several atmospherically mediated processes of environmental and public health concerns. These atmospheric processes affect local and regional environmental quality, including odor, particulate matter (PM) exposure, eutrophication, acidification, exposure to toxics, climate, and pathogens. Agricultural emissions also contribute to the global problems caused by greenhouse gas emissions. Agricultural emissions are variable in space and time and in how they interact within the various processes and media affected. Most important in the U.S. are ammonia (where agriculture accounts for ∼90% of total emissions), reduced sulfur (unquantified), PM 2.5 (∼16%), PM 10 (∼18%), methane (∼29%), nitrous oxide (∼72%), and odor and emissions of pathogens (both unquantified). Agriculture also consumes fossil fuels for fertilizer production and farm operations, thus emitting carbon dioxide (CO 2 ), oxides of nitrogen (NO x ), sulfur oxides (SO x ), and particulates. Current research priorities include the quantification of point and nonpoint sources, the biosphere-atmosphere exchange of ammonia, reduced sulfur compounds, volatile organic compounds, greenhouse gases, odor and pathogens, the quantification of landscape processes, and the primary and secondary emissions of PM. Given the serious concerns raised regarding the amount and the impacts of agricultural air emissions, policies must be pursued and regulations must be enacted in order to make real progress in reducing these emissions and their associated environmental impacts.

The long-term impact of urbanization on nitrogen patterns and dynamics in Shanghai, China

“…The turning point of NH 3 emission emerged is mainly owing to the stopping increase of application rates for nitrogen fertilizer (the largest nitrogen input). Similarly, the turning point was also found in Europe (de Vries et al, 2011a), United States (Reis et al, 2009) and other developed countries in the 1980s owing to the development of precision agriculture that improved the NUE and reduced the nitrogen fertilizer usage (Mosier et al, 2002;Aneja et al, 2009). For example, the NUE of maize production in United States has increased 36% from 1980s to 2000s (Cassman et al, 2002).…”

“…4 and 5a). Population driven nitrogen fluxes vary with policy regulations and economic development (Aneja et al, 2009;Svirejeva-Hopkins et al, 2011). For example, the "Great Cultural Revolution" event (from 1966 to 1976) is an important policy regulation that affects China's society.…”

The molecular processes of urea hydrolysis in relation to ammonia emissions from agriculture

“…However, the toxicity of PM 2.5 seems to largely depend on the specific composition (Schlesinger 2007). Furthermore, by acting as cloud condensation nuclei, the particles can increase formation and lifetime of clouds (Aneja et al 2009). From the perspective of the farmers, the emission of ammonia from both organic and inorganic fertilizers results in a loss of valuable nitrogen, forcing the farmer to over-fertilize fields to obtain the maximum crop yield or accept less optimal production in countries with restrictions and regulations on fertilizer use.…”

Insights into Chemical Coupling among Acidic Gases, Ammonia and Secondary Inorganic Aerosols

“…NH 4 HSO 4 and (NH 4 ) 2 SO 4 are non-volatile in nature whereas NH 4 NO 3 and NH 4 Cl are semi-volatile. These secondary inorganic aerosols (SIA) are formed by reactions involving the only alkaline gas in the atmosphere, NH 3 , with sulfuric acid (H 2 SO 4 ), nitric acid (HNO 3 ) and hydrochloric acid (HCl) (Lin and Cheng, 2007;Aneja et al, 2009;Behera and Sharma, 2011). SIA, represented by ionic species of SO 4 2− , NO 3 − , NH 4 + and Cl − , can account for 20-48% of the mass of PM 2.5 (Balasubramanian et al, 2003;Lin and Cheng, 2007;Weijers et al, 2011).…”