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Journal of Atmospheric Chemistry

Current research reports and chronological list of recent articles..




The international scientific Journal of Atmospheric Chemistry is devoted to the study of the chemistry of the atmosphere, with particular emphasis on the region below about 100 km. The strongly interdisciplinary nature of atmospheric chemistry means that it embraces a great variety of sciences.

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Journal of Atmospheric Chemistry - Abstracts



Sources of HULIS-C and its relationships with trace metals, ionic species in PM 2.5 in suburban Shanghai during haze and non-haze days

Abstract

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 PM2.5 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+, SO42−, 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.


Datum: 01.09.2020


Variation of carbonaceous species and trace elements in PM 10 at a mountain site in the central Himalayan region of India

Abstract

Observations of carbonaceous species [organic carbon (OC), elemental carbon (EC), water soluble organic carbon (WSOC), carbonaceous aerosols (CAs) and secondary organic carbon (SOC) ] and trace elements (As, Cr, Ni, Zn, Na, Mg, Al, P, K, Ca, Ti, Fe, and Mn) in PM10 are made over a high altitude site (ARIES, Nainital, 29.4° N, 79.5° E, ~1958 m amsl) in the central Himalayan region during October 2018−February 2019 to explore their possible sources. The average concentrations of PM10, OC, EC, WSOC, CA and SOC were recorded as 44±13 µg m-3, 3.66±1.26 µg m-3, 1.29±0.61 µg m-3, 2.28±0.76 µg m-3, 7.15±1.96 µg m-3 and 1.45±0.73 µg m-3, respectively during the study period. The concentrations of PM10, OC, EC, WSOC, CAs and SOC were significantly varied during autumn (October-November) and winter (December-February) seasons. During both the seasons, significant positive linear trend between OC & EC and OC & WSOC have been observed which is indicative of their common sources of carbonaceous aerosols at the study site. WSOC/OC ratio was estimated as 0.56 and 0.67 during autumn and winter, respectively suggested that the biomass burning could be one of the major sources of carbonaceous aerosols at Nainital. The significant positive correlation of PM10 with crustal elements (Al, Fe, Ca, Mg and Ti) as well as correlation of Al with other crustal elements (Fe, Ca, Mg and Ti) indicates the abundance of mineral dust at the sampling site. The observed Fe/Al ratio (1.07) also indicates mineral dust as a source at the sampling site, similarly, Ca/Al ratio (1.36) indicates that aerosols over this region is rich in Ca mineral as compared to average continental crust. Principal component analysis (PCA) identified the contribution of crustal/soil dust, biomass burning and industrial emissions to the PM10 over the central Himalayan region of India. Five days back trajectory analysis indicates that the air mass impacting the sampling site is from local surrounding area in Uttrakhand as well from Himachal Pradesh, Jammu & Kashmir, Ingo Gangetic Plain (IGP) region, Pakistan, Afghanistan region and Thar Desert.


Datum: 01.09.2020


Chemical characteristics of particulate matters and their emission sources over Varanasi during winter season

Abstract

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 PM2.5 are 134 ± 48 and 213 ± 80 μg/m3, respectively, which exceeds both national and international standards. The average value of PM2.5/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 SO42−, 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.


Datum: 01.09.2020


Long term trends of wet deposition and atmospheric concentrations of nitrogen and sulfur compounds at EMEP site in Armenia

Abstract

This paper presents the trends of gaseous nitric acid, nitrogen dioxide, sulfur dioxide, ammonia and nitrate, ammonium, sulfate ions in atmospheric air, and nitrate, ammonium and sulfate ions in wet deposition over 2008–2018 in Armenia. Atmospheric nitrogen and sulfur concentrations were monitored by data obtained from filter pack samplers and glass sinter filters at background monitoring station of Armenia (Amberd), which is designated as EMEP (European Monitoring and Evaluation Programme) station. Laboratory analyses were performed by ion chromatography system and UV spectrophotometer. MAKESENS programme was used for detecting and estimating trends in the time series of annual average values of atmospheric concentrations. Long term trends of atmospheric concentrations of nitrogen and sulfur compounds at the Amberd air quality monitoring station were calculated and discussed for the investigated decade. The trends significance levels for all parameters are calculated. It is identified that there are no significant trends for all explored paramenters, except reduced sulfur in aerosols. Possible emission and deposition changes of nitrogen and sulfur compounds in Armenia were explored in order to identify possible transboundary air pollution and its main sources. Deposition data was estimated by EMEP MSC-W model calculations. Investigation of transboundary fluxes of nitrogen and sulfur compounds displays main receptor areas and contributors. Analysis of seasonality in atmospheric pollutants shows strong seasonal behaviour of the measured parameters in wet deposition - higher concentrations during summertime compared with the wintertime. Atmospheric concentrations of nitrate and ammonium ions are lower during summertime compared with the wintertime, while ammonia has low concentrations during wintertime. Atmospheric nitric acid, sulfate ion, sulfur dioxide and nitrogen dioxide revel no significant seasonality.


Datum: 01.09.2020


Vertical distributions of the microscopic morphological characteristics and elemental composition of aerosols over India

Abstract

Particle morphology and elemental compositions are among the crucial parameters of aerosols required for accurate understanding of the climatic effect of aerosols in the earth-atmosphere system; yet their vertical distributions and region specific properties are poorly characterised due to sparse in-situ measurements. This is the first study to classify and quantify the vertical distributions of the morphological characteristics and elemental composition of aerosols based on single particle as well as bulk chemical analysis over seven geographically diverse regions of northern and central parts of India during spring (April–May, 2013), carried out as a part of Regional Aerosol Warming Experiment (RAWEX). Significant regional distinctiveness in shapes (non-sphericity), sizes and elemental compositions of the airborne particles were conspicuous, having dominance of highly irregular granular aggregates over the north Indian sites. The non-spherical coarse mode particles dominated the lower free tropospheric regions (> 2 km) of the Indo-Gangetic Plains (IGP). These particles could be responsible for enhanced spring time aerosol absorption in the elevated region of the atmosphere. Elemental compositions of the single particle analysis indicate that the free tropospheric layer over the IGP and central India is enriched with Na and Ca compounds mixed with Fe or Al (soil particles), indicating long range transport of crustal aerosols. This finding is very well supported by the bulk particle analysis indicating abundance of Ca2+ in the free troposphere with low contribution of ssNa+. Particles with irregular rough surfaces having dominance of SiO2 were observed over all the study sites. The percentage share of spherical (either smooth or rough) particles to the total morphological characteristics of the particles was found to be highly subdued (< 10%). The present study thus critically assesses the relevant knowledge pertaining to the morphological features of aerosols over the IGP during spring for the accurate estimation of aerosol radiative properties. More such efforts are required in future to study the connections and dependencies between morphological and radiative properties of aerosols in different seasons.


Datum: 14.08.2020


Spatio-temporal distribution and chemical composition of PM 2.5 in Changsha, China

Abstract

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 (PM2.5) pollution in Changsha, a provincial capital located in central China. Samples of PM2.5 were collected at five different functional areas from September 2013 to August 2014. The PM2.5 concentration at the five sampling sites was the highest in winter and the lowest in summer, with an average annual PM2.5 concentration of 105.2 ± 11.0 μg/m3. On average, residential sites had the highest concentrations of PM2.5 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 PM2.5 mass. Ion balance calculations show that the PM2.5 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 PM2.5 pollution.


Datum: 01.06.2020


Physico-chemical characterization and sink mechanism of atmospheric aerosols over South-west India

Abstract

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, SO42−, Na+, Mg2+ were observed higher for SINH as compared to Pune, due to the high amount of rain received at SINH.


Datum: 01.06.2020


Effect of wind speed on the level of particulate matter PM10 concentration in atmospheric air during winter season in vicinity of large combustion plant

Abstract

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 (WIOŚ 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.


Datum: 01.06.2020


Temporal and source assessments of organic and elemental carbon at sites in the northern South African interior

Abstract

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 (PM2.5) 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.


Datum: 01.12.2019


Precipitation chemistry and stable isotopic characteristics at Wengguo in the northern slopes of the Himalayas

Abstract

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 (SO42− 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.


Datum: 01.12.2019


Ship-borne observations of sea fog and rain chemistry over the North and South Pacific Ocean

Abstract

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)-SO42−. 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.


Datum: 01.12.2019


Chemical characteristics and source apportionment of PM 2.5 in Wuhan, China

Abstract

Continuous online measurements of fine particulate matter mass (PM2.5) and its chemical composition were carried out at an urban monitoring site in Wuhan from March 2017 to February 2018. The PM2.5 mass concentration ranged from 6.3 to 223 μg/m3, with the highest in winter and the lowest in summer. Water soluble ions (WSIs) were the most abundant component in PM2.5 (28.8 ± 22.9 μg/m3), followed by carbonaceous aerosol (11.9 ± 10.4 μg/m3) and elements (5.5 ± 6.7 μg/m3). It is noteworthy that six episodes of sustained high PM were observed during the study period. Five major contributors of PM2.5 were identified by positive matrix factorization (PMF) to be the iron and steel industry, fugitive dust, secondary photochemistry, traffic-related emission and biomass burning, contributing 26.3%, 5.5%, 29.5%, 29.2% and 9.6% to PM2.5, respectively. Furthermore, conditional probability function (CPF), trajectory analysis and potential source contribution function (PSCF) were used to identify the influences of local activities and regional source. Local sources mainly include Wuhan iron and steel group, construction sites and urban trunk roads, etc. Three pollution transport pathways of PM2.5 in Wuhan were identified to be northwest, east and south pathway, with the relative contribution of 40%, 17% and 43%, respectively. Western Henan, northern Shaanxi and southwestern Shanxi were identified to be the major potential source regions of PM2.5 in Wuhan.


Datum: 01.09.2019


Water-soluble ions and oxygen isotope in precipitation over a site in northeastern Tibetan Plateau, China

Abstract

A total of 30 precipitation samples were collected at a remote site of Qinghai Lake in the northeastern Tibetan Plateau, China, from June to August 2010. All samples were analyzed for major cations (NH4+, Na+, K+, Ca2+, and Mg2+) and anions (F, Cl, NO3, and SO42−), electric conductivity (EC), pH, dissolved organic carbon (DOC), and oxygen isotopic composition (δ18O). The volume-weighted mean (VWM) values of pH and EC in the precipitation samples were 7.2 and 19.0 μs cm−1. Ca2+ was the dominant cation in precipitation with a VWM of 116.9 μeq L−1 (1.6–662.9 μeq L−1), accounting for 45.7% of total ions in precipitation. SO42− was the predominant anion with a VWM of 32.7 μeq L−1, accounting for 47.1% of the total anions. The average precipitation DOC was 1.4 mg L−1, and it shows a roughly negative power function with the precipitation amount. The values of δ18O in the rainwater in Qinghai Lake varied from −13.5‰ to −3.9‰ with an average of −8.1‰. The enrichment factor analysis indicates that crustal materials from continental dust were the major sources for Ca2+ in the precipitation samples. The high concentration of Ca2+ in the atmosphere played an important role in neutralizing the acidity of rainwater in Qinghai Lake area. Cluster analysis of air-mass trajectories indicates that the air masses associated with northeast and east had high values of NH4+, SO42−, and NO3, whereas large Ca2+ loading was related to the air mass from west.


Datum: 01.09.2019


PM 10 carbonaceous aerosols and their real-time wet scavenging during monsoon and non-monsoon seasons at Delhi, India

Abstract

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.


Datum: 01.09.2019


Optical properties of atmospheric particles over an urban site in Mexico City and a peri-urban site in Queretaro

Abstract

Optical properties of atmospheric particles at Mexico City (UNAM) and Queretaro (JQRO) were measured with a Photoacoustic Extinctiometer (PAX) at 870 nm. The Mexico City Metropolitan Area has around 21 million inhabitants and Queretaro Metropolitan Area has little more than a million. Observations of meteorological parameters (relative humidity, solar radiation, and wind speed) were used to identify the rainy and dry seasons and explain the daily and seasonal behaviors of particles optical properties. The measurements were made from November 1, 2014 to July 31, 2016. At UNAM, the mean values of the scattering coefficient (Bscat) in cold dry, warm dry, and rainy seasons were 35.8, 27.1, and 31.3 Mm−1, respectively; while at JQRO were 10.9, 11.9, and 15.0 Mm−1. The average values of the absorption coefficient (Babs) at UNAM during the cold dry, warm dry, and rainy seasons were 14.5, 12.7, and 12.7 Mm−1, respectively; whereas at JQRO were 4.9, 4.7, and 3.9 Mm−1. Both absorption and scattering coefficients showed similar diurnal behaviors, but at UNAM they are three times higher than JQRO. Concentrations of criteria gases (O3, NO, NO2 and NOx) were also measured. At UNAM no difference was observed between the seasonal values for the single scattering albedo (SSA); while in JQRO, the rainy season had the highest seasonal value, being 13% higher than in the dry seasons. The Mass Scattering Cross-Section (MSC) values at UNAM were close to 2 m2/g; on the other hand, at JQRO the MSC values were lower than 1 m2/g. The results suggest a seasonal variability in the aerosol optical properties in both sites, which should be verified with more long-term studies.


Datum: 01.09.2019


PM 2.5 and PM 10 in the urban area of Naples: chemical composition, chemical properties and influence of air masses origin

Abstract

In order to investigate particulate matter characteristics in the urban area of Naples, South of Italy, PM10 and PM2.5 chemical composition and properties were determined; in particular, ionic composition (Na+, K+, NH4+, Mg2+, Ca2+, HCOO-, CH3COO, Cl, NO2, NO3, SO42−, C2O42−) and concentration of specific metals (Pb, Cd, Cu and Zn) were evaluated in association with an air masses trajectories study. Information on major ions was used to conduct the ionic balance and to evaluate sea salt and non-sea salt contributions; furthermore, the study on metals concentration allowed to distinguish the contribution of anthropic sources while their chemical behaviour (solubility and leachability) was considered in order to highlight the presence of different chemical forms. In the period of interest (June 2015), daily averages PM concentrations were below the limit of 25 μg/m3 for PM2.5 and 50 μg/m3for PM10; moreover, for both fractions, the most abundant ionic species was SO42−followed by NO3. Ionic balance indicated that non-sea salt contribution accounted for the great part of Ca2+, SO42− and K+ while secondary inorganic aerosol accounted for about 5% of total ionic fraction. As expected, the most abundant metal was zinc (about 41 ng/m3 and 44 ng/m3in PM2.5 and PM10, respectively), while cadmium, copper and lead were at very low concentrations, in the range of 0.01–0.47 ng/m3; leachability reached values of 40% for copper in both PM fractions, in contrast with zinc that showed the lowest leachability, corresponding to 6% for PM2.5 fraction. The study on air masses trajectories indicated a change on ionic composition and chemical properties, varying from a condition with air masses coming from Eastern Europe, characterised also by higher concentrations of both PM2.5 and PM10, a prevalence of secondary aerosol and metals showing minor solubility and leachability, to a condition with air masses coming from North-west region, with characteristics opposed to the previous ones.


Datum: 01.06.2019


A one year study of functionalised medium-chain carboxylic acids in atmospheric particles at a rural site in Germany revealing seasonal trends and possible sources

Abstract

This study presents a yearlong data set of 28 medium-chain functionalised carboxylic acids (C5 to C10) in atmospheric aerosol particles (PM10) from a German rural measurement station, which is analysed to obtain seasonal trends and evidences for possible sources of these rarely studied compounds. The analysed carboxylic acids were divided into four main groups: (I) functionalised aliphatic monocarboxylic acids, (II) functionalised aromatic monocarboxylic acids, (III) non-functionalised and functionalised aliphatic dicarboxylic acids, and (IV) aromatic dicarboxylic acids. A concentration maximum in summer was observed for aliphatic carboxylic acids, indicating mainly photochemical formation processes. For example, the highest mean summer concentrations were observed for 4-oxopentanoic acid (4.1 ng m−3) in group I and for adipic acid (10.3 ng m−3) in group III. In contrast, a concentration maximum in winter occurred for aromatic carboxylic acids, hinting at anthropogenic sources like residential heating. The highest mean winter concentrations were observed for 4-hydroxybenzoic acid (2.4 ng m−3) in group II and for phthalic acid (5.8 ng m−3) in group IV. For the annual mean concentrations, highest values were found for adipic acid and 4-oxopimelic acids with 7.8 ng m−3 and 6.1 ng m−3, respectively. The concentrations of oxodicarboxylic acids exceeded those of their corresponding unsubstituted form. Accordingly, straight-chain dicarboxylic acids might act as precursor compounds for their respective oxygenated forms. Similarly, unsubstituted monocarboxylic acids are possible precursors for functionalised aliphatic monocarboxylic acids. The present study contributes to the speciation of organic content on a molecular level of atmospheric particles, as well as giving hints for possible sources for these carboxylic acids.


Datum: 01.06.2019


Assessment of polar organic aerosols at a regional background site in southern Africa

Abstract

A recent paper reported GCxGC-TOFMS analysis used for the first time in southern Africa to tentatively characterise and semi-quantify ~1000 organic compounds in aerosols at Welgegund – a regional background atmospheric monitoring station. Ambient polar organic aerosols characterised are further explored in terms of temporal variations, as well as the influence of meteorology and sources. No distinct seasonal pattern was observed for the total number of polar organic compounds tentatively characterised and their corresponding semi-quantified concentrations (sum of the normalised response factors, ∑NRFs). However, the total number of polar organic compounds and ∑NRFs between late spring and early autumn seemed relatively lower compared to the period from mid-autumn to mid-winter, while there was a period during late winter and early spring with significantly lower total number of polar organic compounds and ∑NRFs. Relatively lower total number of polar organic compounds and corresponding ∑NRFs were associated with fresher plumes from a source region relatively close to Welgegund. Meteorological parameters indicated that wet removal during late spring to early autumn also contributed to lower total numbers of polar organics and associated ∑NRFs. Increased anticyclonic recirculation and more pronounced inversion layers contributed to higher total numbers of polar organic species and ∑NRFs from mid-autumn to mid-winter, while the influence of regional biomass burning during this period was also evident. The period with significantly lower total number of polar organic compounds and ∑NRFs was attributed to fresh open biomass burning plumes occurring within proximity of Welgegund, consisting mainly of volatile organic compounds and non-polar hydrocarbons. Multiple linear regression substantiated that the temporal variations in polar organic compounds were related to a combination of the factors investigated in this study.


Datum: 01.06.2019


Ground-based observation of lightning-induced nitrogen oxides at a mountaintop in free troposphere

Abstract

Lightning is an important source of nitrogen oxides (LNOx). The actual global production of LNOx is still largely uncertain. One of the reasons for this uncertainty is the limited available observation data. We measured the concentrations of total reactive nitrogen (NOy), nitric oxide (NO) and nitrogen dioxides (NO2) and then obtained NOx oxidation products (NOz: NOz = NOy - NOx) at a station at the top of Mount Fuji (3776 m a.s.l.) during the summer of 2017. Increases in NOy and NO2 were observed on 22 August 2017. These peaks were unaccompanied by increases in CO, which suggested that the observed air mass did not contain emissions from combustion. The backward trajectories of the above air mass indicated that it moved across areas where lightning occurred. The NOy concentration was also calculated by using a chemical transport model, which did not take NOx produced by lightning into account. Therefore, the NOy concentration due to lightning can be inferred by subtracting the calculated NOy from the observed NOy concentrations. The concentration of NOy at 13:00 on 22 August 2017 originating from lightning was estimated to be 1.11 ± 0.02 ppbv, which comprised 97 ± 2% of the total NOy concentration. The fractions of NO2 and NOz in the total NOy were 0.54 ± 0.01 and 0.46 ± 0.03, respectively. The NO concentration was below the detection limit. We firstly observed increase of concentrations of NOy originating from lightning by ground-based observation and demonstrated the quantitative estimates of LNOx using model-based calculation.


Datum: 01.06.2019


Dissolved organic carbon in summer precipitation and its wet deposition flux in the Mt. Yulong region, southeastern Tibetan Plateau

Abstract

Dissolved organic carbon (DOC) is an important organic pollutant in the air-water carbon cycle system, potentially influencing the global climate. In this study, 204 rainwater samples from five sampling stations in the Mt. Yulong region were synchronously collected from June to September in 2014. We comprehensively investigated the sources and wet deposition of DOC in summer precipitation. The average concentrations of DOC at five stations ranged from 0.74 to 1.31 mg L−1. The mass absorption efficiency (MAE) of rainwater DOC evaluated at 365 nm was 0.43 ± 0.32 m2 g−1. Backward trajectory analyses indicated that the southwest advection air parcel accounting for 46% of precipitation events, while the corresponding average concentration of rainwater DOC was 1.25 ± 0.56 mg C L−1. In addition to the local or regional contribution, large amount of atmospheric pollutants were transported from South Asia and Southeast Asia to the Mt. Yulong region, both of which had exerted great influence on the regional atmospheric environment. For the first time, the annual wet deposition of DOC in the Mt. Yulong region was estimated and determined to be 1.99 g C m−2 year−1. This is significant because the deposition of DOC on glaciers has great influence on surface albedo of snow and glacier melt. This study can bridge the gap of rainwater DOC research between the Mt. Yulong region and the southeast of Tibetan Plateau (TP), which has significant implications for better understanding the relationship of DOC deposition and glacial shrink in the TP.


Datum: 01.03.2019


 


Category: Current Chemistry Research

Last update: 28.03.2018.






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