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

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Title:	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
Authors:	谷邁世;Xue, Jian;Griffith, Stephen M.;Yu, Xin;Lau, Alexis K.H.;Yu, Jian Zhen
Contributors:	地球科學學院大氣科學學系
Keywords:	Abundance;Aerosol chemical composition;Aerosol chemistry;Aerosols;ammonium compounds;Applied sciences;atmospheric chemistry;Atmospheric pollution;Atmospherics;Chemical composition;China;Chinese aerosols;cities;Concentration (composition);crystallization;data collection;Exact sciences and technology;Ionic aerosol constituents;ions;Liquid water content;Nitrates;nitrogen content;nitrogen oxides;particulates;Pollutants physicochemistry study: properties, effects, reactions, transport and distribution;Pollution;regression analysis;Sulfates;sulfur dioxide;thermodynamics;Visibility;Water;water content
Date:	2014-12-01
Issue Date:	2026-04-21 13:58:44 (UTC+8)
Publisher:	Elsevier Ltd.;Kidlington: Elsevier Ltd
Abstract:	摘要： 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. 出版者： Kidlington: Elsevier Ltd 出版日期： 2014-12-01 出處： Atmospheric Environment, 2014-12, Vol.99, p.24-31 資源來源： Elsevier ScienceDirect Journals: Bodleian Libraries collection 版權： 2014 Elsevier Ltd 版權： 2015 INIST-CNRS 識別號： ISSN: 1352-2310 識別號： EISSN: 1873-2844 識別號： DOI: 10.1016/j.atmosenv.2014.09.049
Appears in Collections:	[Department of Atmospheric Sciences] journal & Dissertation

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