Characteristics and Sources of Water-Soluble Inorganic Ions in PM2.5 in Urban Nanjing, China

Guo, Qinghao; Chen, Kui; Xu, Guojie

doi:10.3390/atmos14010135

Cited by 4 publications

(1 citation statement)

References 66 publications

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“…The pH values measured in UAM were 6.29, 6.03, and 6.06 in the HD, CD, and RA seasons, respectively, while in MER, the values were 6.27, 5.79, and 5.92 for the same seasons, confirming the PM 2.5 acid character determined using the ions. These results are in agreement with those of Guo et al [41] and Geng et al [42] but are opposite to those of Yin et al [26] who presented values greater than one, probably due to the excess of alkaline ions. Figure 6 presents the UAM and MER CE/AE ratios from all of the samples.…”

Section: Ion Balance and Seasonal Aciditysupporting

confidence: 87%

Temporal Variation and Potential Sources of Water-Soluble Inorganic Ions in PM2.5 in Two Sites of Mexico City

Millán-Vázquez,

Sosa-Echevería,

Alarcón-Jiménez

et al. 2023

Atmosphere

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This study presents the characterization and source apportionment of water-soluble inorganic ions (WSII), contained in particulate matter with an aerodynamic diameter equal to or less than 2.5 μm (PM2.5), performed using the positive matrix factorization model (PMF). PM2.5 were collected in Mexico City from two sites: at Merced (MER), which is a residential location with commercial activities, and at Metropolitan Autonomous University (UAM), which is located in an industrial area. The monitoring campaign was carried out across three seasons named Hot Dry (HD) (March–June), Rain (RA) (July–October), and Cold Dry (CD) (November-February). PM2.5 concentration behavior in both sites was similar, following the order: CD > HD > RA. The UAM site exhibited higher concentrations of PM2.5, of the five cations (Na+, Mg2+, Ca2+, K+ and NH4+), and of the four anions (Cl−, SO42−, NO3− and PO43−) than MER, since the UAM site is surrounded by several industrial zones. PM2.5 average concentrations for UAM and MER were 28.4 ± 11.2 and 20.7 ± 8.4 μg m−3, respectively. The ratio of cation equivalent to anion equivalent (CE/AC) showed that aerosol pH is acidic, which was confirmed by direct pH measurements. The sulfur oxidation rate (SOR) was 20 times larger than the nitrogen oxidation rate (NOR). Additionally, SO42− was the most abundant ion during the whole year, especially during the CD season with 5.13 ± 2.5 μg m−3 and 4.9 ± 3.6 μg m−3 for UAM and MER, respectively, when solar radiation displayed a high intensity. On the opposite side, the conversion of NO2 to NO3−, respectively, was low. The air mass backward trajectories were modeled using the National Oceanic and Atmospheric Administration (NOAA-HYSPLIT), which allowed us to know that differences in the mass trajectories during the days with higher concentrations were due to an effect of air recirculation, which favored PM2.5 accumulation and resuspension. On the other hand, on the days with less PM2.5, good air dispersion was observed. The main sources identified with the PMF model were secondary aerosol, vehicular, industrial crustal, and biomass burning for UAM, while for MER they were vehicular, secondary aerosol, and crustal.

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Section: Ion Balance and Seasonal Aciditysupporting

confidence: 87%