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Effect of nitrate and sulfate relative abundance in PM2.5 on liquid water content explored through half-hourly observations of inorganic soluble aerosols at a polluted receptor site

Xue, Jian ; Griffith, Stephen M. ; Yu, Xin ; Lau, Alexis K.H. ; Yu, Jian Zhen

Atmospheric environment (1994), 2014-12, Vol.99, p.24-31 [Periódico revisado por pares]

Kidlington: Elsevier Ltd

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  • Título:
    Effect of nitrate and sulfate relative abundance in PM2.5 on liquid water content explored through half-hourly observations of inorganic soluble aerosols at a polluted receptor site
  • Autor: Xue, Jian ; Griffith, Stephen M. ; Yu, Xin ; Lau, Alexis K.H. ; Yu, Jian Zhen
  • Assuntos: Abundance ; Aerosol chemical composition ; Aerosol chemistry ; Aerosols ; Applied sciences ; Atmospheric pollution ; Atmospherics ; Chemical composition ; Chinese aerosols ; Concentration (composition) ; Exact sciences and technology ; Ionic aerosol constituents ; Liquid water content ; Nitrates ; Pollutants physicochemistry study: properties, effects, reactions, transport and distribution ; Pollution ; Sulfates ; Visibility ; Water
  • É parte de: Atmospheric environment (1994), 2014-12, Vol.99, p.24-31
  • Notas: ObjectType-Article-1
    SourceType-Scholarly Journals-1
    ObjectType-Feature-2
    content type line 23
  • Descrição: Liquid water content (LWC) is the amount of liquid water on aerosols. It contributes to visibility degradation, provides a surface for gas condensation, and acts as a medium for heterogeneous gas/particle reactions. In this study, 520 half-hourly measurements of ionic chemical composition in PM2.5 at a receptor site in Hong Kong are used to investigate the dependence of LWC on ionic chemical composition, particularly on the relative abundance of sulfate and nitrate. LWC was estimated using a thermodynamic model (AIM-III). Within this data set of PM2.5 ionic compositions, LWC was highly correlated with the multivariate combination of sulfate and nitrate concentrations and RH (R2 = 0.90). The empirical linear regression result indicates that LWC is more sensitive to nitrate mass than sulfate. During a nitrate episode, the highest LWC (80.6 ± 17.9 μg m−3) was observed and the level was 70% higher than that during a sulfate episode despite a similar ionic PM2.5 mass concentration. A series of sensitivity tests were conducted to study LWC change as a function of the relative nitrate and sulfate abundance, the trend of which is expected to shift to more nitrate in China as a result of SO2 reduction and increase in NOx emission. Starting from a base case that uses the average of measured PM2.5 ionic chemical composition (63% SO42−, 11% NO3−, 19% NH4+, and 7% other ions) and an ionic equivalence ratio, [NH4+]/(2[SO42−] + [NO3−]), set constant to 0.72, the results show LWC would increase by 204% at RH = 40% when 50% of the SO42− is replaced by NO3− mass concentration. This is largely due to inhibition of (NH4)3H(SO4)2 crystallization while PM2.5 ionic species persist in the aqueous phase. At RH = 90%, LWC would increase by 12% when 50% of the SO42− is replaced by NO3− mass concentration. The results of this study highlight the important implications to aerosol chemistry and visibility degradation associated with LWC as a result of a shift in PM2.5 ionic chemical composition to more nitrate in atmospheric environments as is expected in many Chinese cities. •Within study period, aerosol LWC is highly correlated with nitrate, sulfate and RH multivariate (R2: 0.90).•Empirical relationship based on 520 ambient samples shows LWC is more sensitive to nitrate.•Future PM2.5 composition with increased relative nitrate abundance forecasted to have higher LWC.
  • Editor: Kidlington: Elsevier Ltd
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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