Trends in emissions and concentrations of air pollutants in the lower troposphere in the Baltimore/Washington airshed from 1997 to 2011

Abstract

Trends in the composition of the lower atmosphere (0–1500 m altitude) and surface air quality over the Baltimore/Washington area and surrounding states were investigated for the period from 1997 to 2011. We examined emissions of ozone precursors from monitors and inventories as well as ambient ground-level and aircraft measurements to characterize trends in air pollution. The US EPA Continuous Emissions Monitoring System (CEMS) program reported substantial decreases in emission of summertime nitrogen oxides (NO_x) from power plants, up to ∼80% in the mid-Atlantic States. These large reductions in emission of NO_x are reflected in a sharp decrease of ground-level concentrations of NO_x starting around 2003. The decreasing trend of tropospheric column CO observed by aircraft is ∼0.8 Dobson unit (DU) per year, corresponding to ∼35 ppbv yr⁻¹ in the lower troposphere (the surface to 1500 m above ground level). Satellite observations of long-term, near-surface CO show a ∼40% decrease over western Maryland between 2000 and 2011; the same magnitude is indicated by aircraft measurements above these regions upwind of the Baltimore/Washington airshed. With decreasing emissions of ozone precursors, the ground-level ozone in the Baltimore/Washington area shows a 0.6 ppbv yr⁻¹ decrease in the past 15 yr. Since photochemical production of ozone is substantially influenced by ambient temperature, we introduce the climate penalty factor (CPF) into the trend analysis of long-term aircraft measurements. After compensating for inter-annual variations in temperature, historical aircraft measurements indicate that the daily net production of tropospheric ozone over the Baltimore/Washington area decreased from ∼20 ppbv day⁻¹ in the late 1990s to ∼7 ppbv day⁻¹ in the early 2010s during ozone season. A decrease in the long-term column ozone is observed as ∼0.2 DU yr⁻¹ in the lowest 1500 m, corresponding to an improvement of ∼1.3 ppbv yr⁻¹. Our aircraft measurements were conducted on days when severe ozone pollution was forecasted, and these results represent the decreasing trend in high ozone events over the past 15 yr. Back trajectory cluster analysis demonstrates that emissions of air pollutants from Ohio and Pennsylvania through Maryland influence the column abundances of downwind ozone in the lower atmosphere. The trends in air pollutants reveal the success of regulations implemented over the past decades and the importance of region-wide emission controls in the eastern United States

Tropospheric carbon monoxide variability from AIRS under clear and cloudy conditions

“…The background values are shown in blue and the recent emissions in red. In general, decreasing CO trends in both the background and recent emissions are evident over most of the years, which agrees with results from previous studies He et al, 2013).…”

“…Over the SH ocean, the CO decreasing trends are similar for the transported recent emissions (−0.85 ppbv yr −1 ) and the background values (−0.62 ppbv yr −1 ). The fact that the emission reduction in the NH is larger compared to the SH indicates that the primary cause of the emission reduction is the change in pollution sources due to implementation of regulation regimes, and is also likely associated with economic slowdown in the last decade He et al, 2013). For comparison purposes, Table 1 also listed the trends for the un-segregated CO VMRs at 500 hPa for clear (leftmost column) and cloud-cleared conditions (left second column), as also shown in Fig.…”

“…There has been attention recently on the CO trend using satellite measurements, especially considering that the lifetime of MOPITT and AIRS has exceeded 10 yr He et al, 2013). These studies have found a decreasing trend in a number of regions that is possibly due to increased air quality standards and the recent economic slowdown.…”

Precursor reductions and ground-level ozone in the Continental United States

“…In contrast with the large (>50%) reduction in NO x and VOC emissions and similar decreases in NO 2 and NMOC concentrations, the statewide average of the annual fourth-highest daily peak 8-hr O 3 concentrations declined from~85 ppbv in 1994-1996 to7 5 ppbv in 2010-2012 (a decrease of 12%) (DEC NYS, 2013;Blanchard and Hidy, 2013 Various studies (e.g., Gego et al, 2007;Gilliland et al, 2008;Godowitch et al, 2008;Aleksic et al, 2013;Zhou, et al, 2013) The Baltimore, MD-Washington, DC, area is included in nonattainment status. Ozone in these cities responds to not only high-density local precursor emissions, but also westerly transport of pollution from the interior (Bergin et al, 2007;He et al, 2013). Ozone in these cities has steadily declined in concentration,~0.62 ppbv/yr between 1997 and 2010 (~0.7%/ yr), while NO x decreased from 65 to~30 ppbv (~54% or 4%/ yr).…”

Exploring Winter Mortality Variability in Five Regions of England Using Back Trajectory Analysis

“…The development of the technique can be traced back to Petterssen (1940), with one of the first applications to the understanding of airmass origins and associated implications for identifying pollution sources attributable to Fox and Ludwick (1976). Although not without its problems and caveats (Draxler and Taylor 1982;Kahl 1993;Seibert 1993;Stohl 1998;Polissar et al 1999;Hondula et al 2010;Fleming et al 2012), back trajectory analysis has been frequently applied in both meteorological and climatological analyses of environmental variables relevant to human health, such as air pollution (Riccio et al 2007;Suthawaree et al 2008;Karaca et al 2009;Makra et al 2011;He et al 2013), precipitation and temperature (Theoharatos et al 2010;Bednorz 2013;Hernandez-Ceballos et al 2013;Katarzyna 2013;Tosic and Unkasevic 2013), pollen (Stach et al 2007;Zemmer et al 2012), and dust (Engelstaedter et al 2009;Sunnu et al 2013). …”