Abstract
Abstract. The atmospheric concentrations of gaseous HNO3, HCl and NH3 and their relative salts have been measured during two field campaigns in the winter and in the summer of 2007 at Beijing (China), as part of CAREBEIJING (Campaigns of Air Quality Research in Beijing and Surrounding Region). In this study, annular denuder technique used with integration times of 2 and 24h to collect inorganic and soluble PM2.5 without interferences from gas–particle and particle–particle interactions. The results were discussed from the standpoint of temporal and diurnal variations and meteorological effects. Fine particulate Cl−, NH4+ and SO42− exhibited distinct temporal variations, while fine particulate NO3− did not show much variation with respect to season. Daily mean concentrations of fine particulate NH4+ and SO42− were higher during summer (12.30 μg m−3 and 18.24 μg m−3, respectively) than during winter (6.51 μg m−3 and 7.50 μg m−3, respectively). Daily mean concentrations of fine particulate Cl− were higher during winter (2.94 μg m−3) than during summer (0.79 μg m−3), while fine particulate NO3− showed similar both in winter (8.38 μg m−3) and in summer (9.62 μg m−3) periods. The presence of large amounts of fine particulate NO3− even in summer are due to higher local and regional concentrations of NH3 in the atmosphere available to neutralize H2SO4 and HNO3, which is consistent with the observation that the measured particulate species were neutralized. The composition of fine particulate matter indicated the domination of (NH4)2SO4 during winter and summer periods. In addition, the high relative humidity conditions in summer period seemed to dissolve a significant fraction of HNO3 and NH3 enhancing fine particulate NO3− and NH4+ in the atmosphere. All measured particulate species showed diurnal similar patterns during the winter and summer periods with higher peaks in the early morning, especially in summer, when humid and stable atmospheric conditions occurred. These diurnal variations were affected by wind direction suggesting regional and local source influences. The fine particulate species were correlated with NOx and PM2.5, supporting the hypothesis that traffic may be also an important source of secondary particles.
Highlights
Atmospheric particulate matter plays an important role in atmospheric visibility reduction, human health effects, acid deposition and climate (Heintzenberg, 1989; Dockery et al, 1993; Charlson and Heintzenberg, 1995; Vedal, 1997; IPCC, 2007)
These species are secondary in nature and are formed in the atmosphere by physical processes, and/or chemical reactions of precursor gases, such as sulphuric acid (H2SO4), nitric acid (HNO3), hydrochloric acid (HCl) and ammonia (NH3)
Our results showed that excess NH3 existed with a mean value of 0.30 μmol m−3 (5.10 μg m−3) during the winter period, indicating that the atmosphere contained sufficient ammonia to form ammonium nitrate and chloride
Summary
Atmospheric particulate matter plays an important role in atmospheric visibility reduction, human health effects, acid deposition and climate (Heintzenberg, 1989; Dockery et al, 1993; Charlson and Heintzenberg, 1995; Vedal, 1997; IPCC, 2007). The major inorganic particles identified in PM2.5 are sulphate (SO24−), nitrate (NO−3 ), chloride (Cl−) and ammonium (NH+4 ), which typically comprise 25–75 % of atmospheric PM2.5 mass (Gray et al, 1986; Heitzenberg, 1989) These species are secondary in nature and are formed in the atmosphere by physical processes (nucleation, condensation and evaporation), and/or chemical reactions of precursor gases (photochemical gas phase, aqueous-phase oxidation and particulate-phase processes), such as sulphuric acid (H2SO4), nitric acid (HNO3), hydrochloric acid (HCl) and ammonia (NH3). When atmospheric nitric acid is available, it has a tendency to react with basic species such as NH3 to form NH4NO3 This reaction is believed to be the main source of fine particulate nitrate in urban air (Stockwell et al, 2000). Marine phytoplankton degradation of dimethyl sulfide (DMS)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
