D. Chand

Vertical distribution of mercury, CO, ozone, and aerosol scattering coefficient in the Pacific Northwest during the spring 2006 INTEX-B campaign

[1] In the spring of 2006, we measured the vertical distribution of gaseous elemental mercury (GEM), CO, ozone, and aerosol scattering coefficient in the Pacific Northwest concurrent with NASA’s INTEX-B campaign. Seven profiles from the surface to 6 km were conducted from 12 April to 8 May along with one flight in the Seattle-Tacoma boundary layer. Ozone had a bimodal distribution with the lower mode occurring primarily in the mixed layer and the higher mode occurring in the free troposphere. In the free troposphere, the mixing ratios (1 � s) of GEM, CO, ozone, and aerosol scattering coefficient were 1.52 (0.165) ng/m 3 , 142 (14.9) ppbv, 78 (7.7) ppbv, and 3.0 (1.8) Mm � 1 , respectively. GEM and CO were correlated in the high ozone mode (r 2 = 0.30) but were uncorrelated in the lower mode (r 2 = 0.05). Three flights observed enhancements of GEM and CO with good correlations and with regression slopes (0.0067 (±0.0027) ng/m 3 /ppbv by ordinary least squares regression and 0.0097 (±0.0018) ng/m 3 /ppbv by reduced major axis regression) slightly higher than previous observations of enhancements due to Asian industrial long-range transport (LRT). The influence of Asian LRT is supported by back trajectories and a global chemical transport model. In the SeattleTacoma boundary layer flight, CO was uncorrelated with GEM, which reflects relatively weaker local GEM sources. On three flights, pockets of air were observed with strong inverse GEM-ozone and ozone-CO correlations (in contrast to all data), which is evidence of upper tropospheric/lower stratospheric (UTLS) influence. An extrapolation of the GEM-CO and GEM-ozone slopes suggests the UTLS can be depleted of GEM.

Laboratory measurements of smoke optical properties from the burning of Indonesian peat and other types of biomass

We present the first results on optical properties ({lambda}{approximately} 540 nm) of fresh aerosols from the combustion of Indonesian peat, German peat and other types of biomass, measured under controlled laboratory conditions. The mass scattering and mass absorption efficiencies for Indonesian and German peat aerosols are in the range of 6.0-8.1 and 0.04-0.06 m{sup 2} g{sup -1}, respectively. A very high single scattering albedo ( 0.99) is observed for the peat smoke aerosols, reflecting the smoldering burning conditions (emission ratio, {Delta}CO/{Delta}CO{sub 2} = 19-50%). The relative increase in light scattering f(RH) due to an increase in relative humidity (RH) from 15% to 90% is very low (i.e., f(90) = 1.05) for both Indonesian and German peat aerosols. This value is considerably smaller than for aged Indonesian peat smoke particles (f(80) = 1.65) ( Gras et al., 1999). This suggests that atmospheric aging processes may be an important factor for aerosol hygroscopicity.

Regional Influence of Aerosol Emissions from Wildfires Driven by Combustion Efficiency: Insights from the BBOP Campaign

Wildfires are important contributors to atmospheric aerosols and a large source of emissions that impact regional air quality and global climate. In this study, the regional and nearfield influences of wildfire emissions on ambient aerosol concentration and chemical properties in the Pacific Northwest region of the United States were studied using real-time measurements from a fixed ground site located in Central Oregon at the Mt. Bachelor Observatory (∼2700 m a.s.l.) as well as near their sources using an aircraft. The regional characteristics of biomass burning aerosols were found to depend strongly on the modified combustion efficiency (MCE), an index of the combustion processes of a fire. Organic aerosol emissions had negative correlations with MCE, whereas the oxidation state of organic aerosol increased with MCE and plume aging. The relationships between the aerosol properties and MCE were consistent between fresh emissions (∼1 h old) and emissions sampled after atmospheric transport (6-45 h), suggesting that biomass burning organic aerosol concentration and chemical properties were strongly influenced by combustion processes at the source and conserved to a significant extent during regional transport. These results suggest that MCE can be a useful metric for describing aerosol properties of wildfire emissions and their impacts on regional air quality and global climate.