Publikationsdatum:
2019
Beschreibung:
Abstract
Aerosol pH is a useful diagnostic of aerosol chemistry for formation of secondary aerosol and has been hypothesized to be a key factor in specific chemical reaction routes producing sulfate and nitrate (Yue et al., 2009; Zhang et al., 2012; Hu et al., 2014). In this study, we measured hourly concentrations of water soluble ions (WS‐ions) in PM2.5, along with gaseous pollutants in Tianjin, China, from 4th January to 31st January 2015. The following source contributions to WS ions were estimated by PMF (Positive Matrix Factorization): secondary sulfate (13%), secondary nitrate (44%), coal (14%), vehicle (16%), and dust (13%). ISORROPIA‐II was used to investigate the complex relationships among aerosol pH, ammonia, and secondary aerosol formation. The estimated hourly aerosol pH varied from ‐0.3 to 7.7, with an average of 4.9 (±0.78); the median value was 4.89, and the interquartile range (IQR) was 0.72. During less polluted conditions, aerosol pH ranged from less than 0 to about 7; during heavily polluted conditions, pH was close to 5 (3.9‐7.9) despite large amounts of sulfate. Sufficient ammonia/ammonium were present to balance high sulfate and nitrate formation. NH4+/NH3 (g) helped stabilize pH while nonvolatile cations contributed less to decreasing aerosol acidity. High acidy (pH〈3), light pollution (Total water soluble ions (TWI)〈30 μg m‐3), and low water content (less than 5μg m‐3) were more correlated with higher rates of sulfate formation than nitrate formation in the winter.
Print ISSN:
2169-897X
Digitale ISSN:
2169-8996
Thema:
Geologie und Paläontologie
,
Physik
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