Recent trends in gas-phase ammonia and PM_2.5 ammonium in the Southeast United States

Figures & data

Figure 1. Emissions of sulfur dioxide (SO₂) and total nitrogen oxides (NO_x) for the entire U.S. (open circles) and only the Southeast (solid circles) as estimated by Xing et al. (2013).

Figure 2. Total annual ammonia emissions by source category for 1990–2010 summed for the (a) entire U.S. and (b) only the SEARCH states Alabama, Georgia, Mississippi, and Florida (Xing et al., 2013).

Table 1. SEARCH monitoring sites information

Name	City	Type	Setting	Latitude (°N)	Longitude (°W)
JST	Atlanta, GA	Urban	Industrial-residential	33.776	84.413
YRK	Yorkville, GA	Rural	Forest-agricultural	33.391	85.046
BHM	Birmingham, AL	Urban	Industrial-residential	33.553	86.815
CTR	Centreville, AL	Rural	Forest-agricultural	32.902	87.250
GFP	Gulfport, MS	Urban	Residential	30.391	89.050
OAK	Oak Grove, MS	Rural	Forest	30.985	88.932
PNS	Pensacola, FL	Urban	Residential	30.437	87.256
OLF	Pensacola, FL	Suburban	Forest-grass	30.551	87.376

Figure 3. Annual statistics for gas-phase NH₃ at SEARCH monitoring sites for 2004–2012. Box-whisker plots present means (solid horizontal line), medians (dotted horizontal line), and 5th, 10th, 25th, 75th, 90th, and 95th percentiles. Trend lines as estimated with a nonparametric Mann-Kendall test and using the Theil-Sen slope estimate (numerical value also shown) are presented (statistically significant trends at the α = 0.05 level are shown with a solid line; statistically insignificant trends are shown with a dashed line). Note differences in scale by site.

Figure 4. Annual statistics for PM_2.5 NH₄⁺ at SEARCH monitoring sites for 2004–2012. Box-whisker plots present means (solid horizontal line), medians (dotted horizontal line), and 5th, 10th, 25th, 75th, 90th, and 95th percentiles. Trend lines as estimated with a nonparametric Mann-Kendall test and using the Theil-Sen slope estimate (numerical value also shown) are presented (statistically significant trends at the α = 0.05 level are shown with a solid line; statistically insignificant trends are shown with a dashed line). Note differences in scale by site.

Figure 5. Annual statistics for total ammonia, NH_x = NH₃ + PM_2.5 NH₄⁺, at SEARCH monitoring sites for 2004–2012. Box-whisker plots present means (solid horizontal line), medians (dotted horizontal line), and 5th, 10th, 25th, 75th, 90th, and 95th percentiles. Trend lines as estimated with a nonparametric Mann-Kendall test and using the Theil-Sen slope estimate (numerical value also shown) are presented (statistically significant trends at the α = 0.05 level are shown with a solid line; statistically insignificant trends are shown with a dashed line). Note differences in scale by site.

Figure 6. Annual statistics for the fraction of total ammonia in the gas phase, NH₃/(NH₃ + PM_2.5 NH₄⁺), at SEARCH monitoring sites for 2004–2012. Box-whisker plots present means (solid horizontal line), medians (dotted horizontal line), and 5th, 10th, 25th, 75th, 90th, and 95th percentiles. Trend lines as estimated with a nonparametric Mann-Kendall test and using the Theil-Sen slope estimate (numerical value also shown) are presented (statistically significant trends at the α = 0.05 level are shown with a solid line; statistically insignificant trends are shown with a dashed line).

Figure 7. Annual statistics for PM_2.5 SO₄²⁻ at SEARCH monitoring sites for 2004–2012. Box-whisker plots present means (solid horizontal line), medians (dotted horizontal line), and 5th, 10th, 25th, 75th, 90th, and 95th percentiles. Trend lines as estimated with a nonparametric Mann-Kendall test and using the Theil-Sen slope estimate (numerical value also shown) are presented (statistically significant trends at the α = 0.05 level are shown with a solid line; statistically insignificant trends are shown with a dashed line). Note differences in scale by site.

Figure 8. Annual statistics for PM_2.5 NO₃⁻ at SEARCH monitoring sites for 2004–2012. Box-whisker plots present means (solid horizontal line), medians (dotted horizontal line), and 5th, 10th, 25th, 75th, 90th, and 95th percentiles. Trend lines as estimated with a nonparametric Mann-Kendall test and using the Theil-Sen slope estimate (numerical value also shown) are presented (statistically significant trends at the α = 0.05 level are shown with a solid line; statistically insignificant trends are shown with a dashed line). Note differences in scale by site.

Figure 9. Annual statistics for the inorganic neutralization ratio NH₄⁺/(2SO₄²⁻ + NO₃⁻) at SEARCH monitoring sites for 2004–2012. Box-whisker plots present means (solid horizontal line), medians (dotted horizontal line), and 5th, 10th, 25th, 75th, 90th, and 95th percentiles. Trend lines as estimated with a nonparametric Mann-Kendall test and using the Theil-Sen slope estimate (numerical value also shown) are presented (statistically significant trends at the α = 0.05 level are shown with a solid line; statistically insignificant trends are shown with a dashed line).

Figure 10. Annual statistics for organic matter (OM) at SEARCH monitoring sites for 2004–2012. SEARCH uses an OM/OC conversion factor of 1.4. Box-whisker plots present means (solid horizontal line), medians (dotted horizontal line), and 5th, 10th, 25th, 75th, 90th, and 95th percentiles. Trend lines as estimated with a nonparametric Mann-Kendall test and using the Theil-Sen slope estimate (numerical value also shown) are presented (statistically significant trends at the α = 0.05 level are shown with a solid line; statistically insignificant trends are shown with a dashed line). Note differences in scale by site.

Xing, J., J. Pleim, R. Mathur, G. Pouliot, C. Hogrefe, C.-M. Gan, and C. Wei. 2013. Historical gaseous and primary aerosol emissions in the United States from 1990 to 2010. Atmos. Chem. Phys. 13:7531–7549. doi:10.5194/acp-13-7531-2013

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