Historical gaseous and primary aerosol emissions in the United States from 1990 to 2010

Abstract

An accurate description of emissions is crucial for model simulations to reproduce and interpret observed phenomena over extended time periods. In this study, we used an approach based on activity data to develop a consistent series of spatially resolved emissions in the United States from 1990 to 2010. The state-level anthropogenic emissions of SO₂, NO_x, CO, NMVOC (non-methane volatile organic compounds), NH₃, PM₁₀ and PM_2.5 for a total of 49 sectors were estimated based on several long-term databases containing information about activities and emission controls. Activity data for energy-related stationary sources were derived from the State Energy Data System. Corresponding emission factors reflecting implemented emission controls were calculated back from the National Emissions Inventory (NEI) for seven years (i.e., 1990, 1995, 1996, 1999, 2001, 2002 and 2005), and constrained by the AP-42 (US EPA's Compilation of Air Pollutant Emissions Factors) dataset. Activity data for mobile sources including different types of highway vehicles and non-highway equipment were obtained from highway statistics reported by the Federal Highway Administration. The trends in emission factors for highway mobile source were informed by the 2011 National Transportation Statistics. Emissions for all non-energy-related sources were either scaled by the growth ratio of activity indicators or adjusted based on the NEI trends report. <br><br> Because of the strengthened control efforts, particularly for the power sector and mobile sources, emissions of all pollutants except NH₃ were reduced by half over the last two decades. The emission trends developed in this study are comparable with the NEI trend report and EDGAR (Emissions Database for Global Atmospheric Research) data, but better constrained by trends in activity data. Reductions in SO₂, NO_x, CO and EC (speciation of PM_2.5 by SMOKE, Sparse Matrix Operator Kernel Emissions) emissions agree well with the observed changes in ambient SO₂, NO₂, CO and EC concentrations, suggesting that the various controls on emissions implemented over the last two decades are well represented in the emission inventories developed in this study. These inventories were processed by SMOKE and are now ready to be used for regional chemistry transport model simulations over the 1990–2010 period

Recent trends in gas-phase ammonia and PM2.5 ammonium in the Southeast United States

“…It would be expected that trends in atmospheric NH x would track trends in emissions, and it is seen that this is qualitatively true when comparing Figure 5 with the estimates of Xing et al (2013) for NH 3 emissions from the four SEARCH states (Georgia, Florida, Alabama, and Mississippi) in Figure 2b. Although NH 3 emissions for the entire U.S. are estimated to have slowly risen (+0.5% yr −1 ) over the past two decades (Figure 2a; Xing et al, 2013), emissions for the four SEARCH states have generally decreased over the same time period (−0.9% yr −1 ), driven primarily by decreasing emissions from declining cattle production in the Southeast (United States Department of Agriculture [USDA], 2009).…”

“…Although NH 3 emissions for the entire U.S. are estimated to have slowly risen (+0.5% yr −1 ) over the past two decades (Figure 2a; Xing et al, 2013), emissions for the four SEARCH states have generally decreased over the same time period (−0.9% yr −1 ), driven primarily by decreasing emissions from declining cattle production in the Southeast (United States Department of Agriculture [USDA], 2009). However, considerable variability in annual estimates is observed, with much of the variability accounted for by annual differences in the amount of NH 3 emitted from wildfires.…”

“…Agricultural sources of NH 3 (from the waste products of domesticated livestock, including hogs, poultry, cattle and sheep; from fertilizer volatilization from managed cropland; and from cultivated legumes) account for nearly two-thirds of total global emissions and nearly 90% of U.S. emissions, but emissions from power generation, industry, motor vehicles, and wildfires also contribute substantially (Erisman et al, 2007;Xing et al, 2013). In the atmosphere, gaseous NH 3 may react with sulfuric (H 2 SO 4 ) or nitric (HNO 3 ) acid to form ammonium (NH 4 + ) salts, which constitute a significant fraction of the total mass of fine particles in many areas (Hand et al, 2012), elevated concentrations of which have been statistically linked to various human health impacts (Pope and Dockery, 2006).…”

“…In the United States (U.S.), emissions of sulfur dioxide (SO 2 ) and nitrogen oxides (NO x ) have been decreasing over the past two decades (Figure 1; Xing et al, 2013) due to Clean Air Act requirements and associated regulations (U.S. Environmental Protection Agency [EPA], 2013). On the other hand, total U.S. NH 3 emissions are estimated to have risen slightly over the same time period, but have trended downward in the Southeast due to declining livestock populations ( Figure 2).…”

Increasing importance of deposition of reduced nitrogen in the United States

“…Further reductions are expected in coming years due to additional policy actions (e.g., the Cross-State Air Pollution Rule, reductions in mobile source emissions, and 5-y reviews of the National Ambient Air Quality Standards). Meanwhile, NH 3 emissions have been reported to increase by 11% between 1990 and 2010 (17), with contributing factors including regional growth in livestock numbers and increased application of NO x controls such as selective catalytic reduction. Unlike NO x , NH 3 emissions in the United States are not regulated.…”