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Evolution of trace elements in the planetary boundary layer in southern China: Effects of dust storms and aerosol‐cloud interactions
Author(s) -
Li Tao,
Wang Yan,
Zhou Jie,
Wang Tao,
Ding Aijun,
Nie Wei,
Xue Likun,
Wang Xinfeng,
Wang Wenxing
Publication year - 2017
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2016jd025541
Subject(s) - aerosol , trace element , scavenging , environmental chemistry , dust storm , precipitation , chemistry , solubility , cloud physics , mineralogy , meteorology , cloud computing , physics , organic chemistry , computer science , antioxidant , operating system , biochemistry
Aerosols and cloud water were analyzed at a mountaintop in the planetary boundary layer in southern China during March–May 2009, when two Asian dust storms occurred, to investigate the effects of aerosol‐cloud interactions (ACIs) on chemical evolution of atmospheric trace elements. Fe, Al, and Zn predominated in both coarse and fine aerosols, followed by high concentrations of toxic Pb, As, and Cd. Most of these aerosol trace elements, which were affected by dust storms, exhibited various increases in concentrations but consistent decreases in solubility. Zn, Fe, Al, and Pb were the most abundant trace elements in cloud water. The trace element concentrations exhibited logarithmic inverse relationships with the cloud liquid water content and were found highly pH dependent with minimum concentrations at the threshold of pH ~5.0. The calculation of Visual MINTEQ model showed that 80.7–96.3% of Fe(II), Zn(II), Pb(II), and Cu(II) existed in divalent free ions, while 71.7% of Fe(III) and 71.5% of Al(III) were complexed by oxalate and fluoride, respectively. ACIs could markedly change the speciation distributions of trace elements in cloud water by pH modification. The in‐cloud scavenging of aerosol trace elements likely reached a peak after the first 2–3 h of cloud processing, with scavenging ratios between 0.12 for Cr and 0.57 for Pb. The increases of the trace element solubility (4–33%) were determined in both in‐cloud aerosols and postcloud aerosols. These results indicated the significant importance of aerosol‐cloud interactions to the evolution of trace elements during the first several cloud condensation/evaporation cycles.