Journal of Atmospheric Chemistry最新文献

Humic-like substances (HULIS), the most ubiquitous class of water-soluble organic compounds in the atmosphere could enhance the generation of reactive oxygen species (ROS), and play a significant role in impacting aerosol chemistry and health effects. In this study, twenty-three PM_2.5 samples were collected in the atmosphere of suburban Shanghai from November 29 to December 17, 2015, and March 17 to April 30, 2016, during haze and non-haze days. The mean concentrations of HULIS in spring both in haze and non-haze days (2.34?±?0.70 μg/m³ and 1.94?±?0.88 μg/m³) were relatively higher than in that of winter (1.93?±?0.95 μg/m³ and 1.31?±?0.28 μg/m³). The ammonium, sulfate, and nitrate are the dominant ionic species in both winter and spring during haze days in suburban Shanghai. Correlation results revealed that HULIS formation was highly associated with the biomass burning (K) and secondary aerosols formation (SIA: NH₄⁺, SO₄^2?, NO₃^?) and also well-correlated with F^? and ca.²⁺ ions, crustal elements (Al and Fe) and anthropogenic pollution metals (As, Se, Rb, Sr, and Pb), suggesting that HULIS-C formation might be from biomass burning and secondary aerosol processes and also mixed formation (marine, crustal and industrial emissions) sources. From the coinciding results of the clustering analysis and weighted-CWT model, the principal potential source regions were the short transports from the Yangtze River Delta (YRD) regions, local regions, marine areas (the Bohai Sea, the Yellow Sea, the East China Sea) and also the long-range transports from northwestern in those seasons.

The chemical composition of particulate matter impacts both human health and climate. In this study, the chemical characteristics of particulate matter was measured for four months (November 2016–February 2017) at Varanasi, which is located in the middle of the Indo-Gangetic Basin (IGB). The daily observed mean values of PM₁₀ and PM_2.5 are 134?±?48 and 213?±?80?μg/m³, respectively, which exceeds both national and international standards. The average value of PM_2.5/PM₁₀ ratio is 0.64?±?0.16 which indicates a relatively higher fraction of fine particles that are attributed to anthropogenic emission sources (biomass/post-harvest burning) as corroborated by MODIS fire counts and back trajectory analysis. Ion chromatographic measurements showed that SO₄^2?, Cl^?, K⁺, NO₃^?, Na⁺, Ca²⁺, Mg²⁺ are the major ionic species present in the aerosol. Scanning Electron Microscopy with Energy Dispersive X-Ray (SEM–EDX) analysis shows the prevalence of carbon-rich particles at Varanasi which is likely due to biomass burning and other anthropogenic sources.

Clouds, fogs, and rain can serve as useful integrators of both atmospheric aerosols and soluble trace gases. To better understand the chemical characteristics of sea fog and rain in the North and South Pacific Ocean, fog and rain were measured aboard the R/V ARAON in 2012 and 2014, respectively, as part of the Ship-borne Pole-to-Pole Observations (SHIPPO) project. The mean sea fog pH (3.59) was lower than the mean rain pH (4.54), reflecting greater inputs of non-sea-salt (nss)-SO₄^2?. For the collected rain, nss-Ca²⁺ and nss-Mg²⁺ from mineral dust particles were the major contributors to acidity neutralization. NO₃^? concentrations, which are derived from scavenging of gaseous nitric acid and aerosol nitrate, were higher than NH₄⁺ concentrations, indicating that terrestrial and/or local anthropogenic NO₃^? sources outweighed contributions from anthropogenic or biological oceanic NH₃/NH₄⁺ sources. The ratio of Cl^?/Na⁺ in the sea fog was slightly lower than that in the sea water due to HCl volatilization from scavenged sea-salt particles. The ratio of NH₄⁺/ nss-Ca²⁺ was lower in the rain than in the sea fog, revealing the influence of mineral dust particles at altitudes above the sea fog layer. The average sea fog water TOC concentration, 13.2 ppmC, was much higher than the measured TOC concentrations in marine fogs and clouds in other remote environments, likely due to continental influence; the TN and TOC concentrations in the fog water were much higher than those in the rain. The sea fog and rain chemical properties measured during research cruises like these enhance our understanding of wet deposition and cloud condensation nuclei sources and processes in the Pacific Ocean.

The concentrations of suspended particulate matter PM10 in two-month winter period, i.e. December–January in years 2009–2015, were analyzed in relation to the values of wind speed in that time. It was possible to analyze results of air pollution measurements performed in the measuring station from the perspective of their higher levels in winter seasons (so-called smog episodes). Results from 3 stations of the Regional Inspectorate for Environmental Protection in Poznań (WIO? Poznań) served for better presentation of smog episodes in the region (black smog) and aimed at verification of correctness of the measurements of pollution immission in the monitoring station in Piotrkowice which is situated in vicinity of large combustion plant. The analysis confirmed that with low speeds of wind higher values of particulate matter PM10 were observed. The results of the analysis also show the displacement of pollutants according to the current wind direction or their local persistence for a longer time over one area.

The properties of the atmospheric aerosols depend on the source region and on the modifications that occur during their transport in the air. We have studied physical and chemical properties of aerosols along with their sink mechanism over two locations in southwest India, an urban site (Pune) and well-established climate observatory at Sinhagad (SINH), which represents rural and high altitude site. The ground-based measurements of aerosols, together with their radiative properties in this study have provided means to understand the observed variability and the impact on the aerosol radiative properties effectively over this region. The annual mean elemental carbon concentration (3.4 μg m^??3) at Pune was observed about three times higher compared to SINH (1.3 μg m^??3), indicating strong emissions of carbon-rich aerosols at the urban location. Aerosol optical properties were derived using the OPAC model which were used to compute the Aerosol radiative forcing (ARF) over both stations calculated using SBDART (Santa Barbara DISORT Atmospheric Radiative Transfer) model shows pronounced seasonal variations due to changes in aerosol optical depth and single scattering albedo at both locations. The year-round ARF was 4–5 times higher over Pune (31.4?±?3.5 Wm^??2) compared to SINH (7.2?±?1.1 Wm^??2). The atmospheric heating rate due to aerosols shows a similar pattern as ARF for these locations. The heating was higher in the wintertime, ~?0.9–1.6 K day^??1 at Pune, and ~?0.3–0.6 K day^??1 at SINH. The estimated scavenging ratio was found high for NO₃^? and Ca.²⁺. The wet deposition fluxes of Cl^?, SO₄^2?, Na⁺, Mg²⁺ were observed higher for SINH as compared to Pune, due to the high amount of rain received at SINH.

The major ions in precipitation can reflect the conditions of the atmosphere, while stable isotopic characteristics provide information on the moisture source. In order to understand the local hydro-chemical features and regional geochemical cycle, it is essential to assess the chemical composition of precipitation and the associated sources. Therefore, a total of 57 precipitation samples (2016 to 2017) for major ions and 178 samples (2013 to 2017) for stable isotopes were collected from the Wengguo station and analyzed to explore the major ionic deposition and stable isotopic characteristics in the northern slopes of the Himalayas. The average pH and electrical conductivity were 6.82?±?0.45 and 15.36?±?11.67 μS cm^?1, respectively. Ca²⁺ followed by K⁺ and Mg²⁺ played a crucial role in neutralizing the precipitation acidity. The major ionic sources in the region were terrigenous (Ca²⁺, HCO₃^?, and Mg²⁺) and sea salt (Na⁺, Cl^?, and Mg²⁺), as well as anthropogenic emissions (SO₄^2? and NO₃^?) and biomass burning (K⁺). The total deposition flux of the major ions was higher in 2016 than in 2017 and was influenced by the higher precipitation. The average values of δ¹⁸O and δD in precipitation were???15.22?±?5.17 ‰ and???116.01?±?41.31 ‰, respectively. The precipitation stable isotopes were not significantly correlated to the local air temperature but the precipitation amount. Moreover, the variation in stable isotopes, local meteoric water line, and d-excess indicated the existence of continental and monsoon moisture transport systems. The transport of chemicals over the high elevation region from polluted cities in South Asia via moisture originating in the Bay of Bengal and the Arabian Sea was determined based on the source identification, clusters of air mass backward trajectory analysis, and the National Center for Environmental Prediction Final dataset. Thus, the ionic concentrations and stable isotopic characteristics of the precipitation from this study provided a valuable dataset to assess the atmospheric environment in the northern slopes of the Himalayas at Southern Tibetan Plateau.

Particulate matter (PM) can affect climate, air quality, human health, acid deposition and visibility, and contain a significant fraction of organic (OC) and elemental carbon (EC). Southern Africa is an important source region for OC and EC, however, little OC and EC data have been published for this region. This paper presents a multi-year, multi-site (an urban-industrial site in the Vaal Triangle, UI-VT; an industrially influenced site at Amerfoort, iI-AF; and two regional background sites at Skukuza and Louis Trichardt, RR-SK and RR-LT) PM with an aerodynamic diameter?≤?2.5?μm (PM_2.5) OC and EC dataset for South Africa. The median OC (9.3) and EC (3.2?μg.m^?3) concentrations at UI-VT were 1.3 to 2.5 and 2.7 to 4.4 times higher, if compared to the other sites. OC/EC ratios indicated that sources in close proximity to UI-VT were likely the main contributors, while sources that are more distant contributed fractionally more at the other sites. Household combustion for space heating and regional open biomass burning contributed to elevated levels during the cold and dry months at UI-VT. Regional open biomass burning also lead to higher OC and EC concentrations during the dry season at the industrially influenced site (iI-AF) and one of the regional background sites (RR-SK). From the seasonal concentration patterns, it seemed as if household combustion for space heating also contributed at these two sites during the cold months, but this could not be proven, even if only samples with limited influence of open biomass burning were considered. Such biomass burning influences were semi-quantified by considering MODIS fire pixels occurring within the air mass fetch region for each sample. For the remaining regional background site (RR-LT) the results suggesed that only regional open biomass burning contributed to elevated levels of OC and EC in the dry season and that household combustion for space heating did not contribute significantly.

The rapid economic development and significant expansion of urban agglomerations in China have resulted in issues associated with haze and photochemical smog. Central China, a transitional zone connecting the eastern coast and western interior, suffers from increasing atmospheric pollution. This study performed a spatio-temporal analysis of fine particulate matter (PM_2.5) pollution in Changsha, a provincial capital located in central China. Samples of PM_2.5 were collected at five different functional areas from September 2013 to August 2014. The PM_2.5 concentration at the five sampling sites was the highest in winter and the lowest in summer, with an average annual PM_2.5 concentration of 105.2?±?11.0?μg/m³. On average, residential sites had the highest concentrations of PM_2.5 while suburban sites had the lowest. We found that inorganic ionic species were dominant (~48%), organic species occupied approximately 25%, whereas EC (~3.7%) contributed insignificantly to the total PM_2.5 mass. Ion balance calculations show that the PM_2.5 samples at all sites were acidic, with increased acidity in spring and summer compared with autumn and winter. Air quality in Changsha is controlled by four major air masses: (1) Wuhan and the surrounding urban clusters, (2) the Changsha-Zhuzhou-Xiangtan urban agglomeration and the surrounding cities, and (3) southern and (4) eastern directions. The north–south transport channel is the most significant air mass trajectory in Changsha and has a significant impact on PM_2.5 pollution.

Real-time simultaneous measurements of rainwater and PM₁₀ chemistry were carried out at Delhi during the year 2016–17 in order to assess the levels of carbonaceous species and their wet scavenging during monsoon and non-monsoon seasons at Delhi. The PM₁₀ samples were collected Before Rain (BR), During Rain (DR) and After Rain (AR) events, while rainwater samples collected on an event basis. The ambient OC levels were always higher than the levels of EC during both monsoon and non-monsoon seasons in ambient aerosol as well as in rainwater. On an average, during rain (DR) 30% of OC aerosols and 28.2% of EC aerosols removed via wet scavenging process. In after rain (AR), 26.2% OC and 1.8% EC aerosols further decreased in comparison to DR samples due to the presence of OC and EC free air parcel. Overall it observed that the OC concentration significantly lowered from BR to DR and AR. However, EC concentrations in AR were found to be higher than DR samples indicating their build-up after the rains. The Scavenging Ratios (SRs) of OC and rain intensity had a significant positive correlation, whereas the SRs of EC showed a weak correlation with rain intensity. The SRs of EC were significantly higher during non-monsoon as compared to monsoon season. Such characteristics can be explained based on the particles size, source and the hygroscopicity of both types of carbonaceous aerosol.