Uptake of nitrate and sulfate on dust aerosols during TRACE-P

Aerosol data collected near Asia on the DC-8 aircraft platform during TRACE-P has been examined for evidence of uptake of NO3- and SO4= on dust surfaces. Data is compared between a sector where dust was predominant and a sector where dust was less of an influence. Coincident with dust were higher mixing ratios of anthropogenic pollutants. HNO3, SO2, and CO were higher in the dust sector than the nondust sector by factors of 2.7, 6.2, and 1.5, respectively. The colocation of dust and pollution sources allowed for the uptake of NO3- and nss-SO4= on the coarse dust aerosols, increasing the mixing ratios of these particulates by factors of 5.7 and 2.6 on average. There was sufficient nss-SO4= to take up all of the NH4+ present, with enough excess nss-SO4= to also react with dust CaCO3. This suggests that the enhanced NO3- was not in fine mode NH4NO3. Particulate NO3- (p-NO3-) constituted 54% of the total NO3- (t-NO3-) on average, reaching a maximum of 72% in the dust sector. In the nondust sector, p-NO3- contributed 37% to t-NO3-, likely due to the abundance of sea salts there. In two other sectors where the influence of dust and sea salt were minimal, p-NO3- accounted for < 15% of t-NO3-.