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This study evaluates the composition and seasonal characteristics of fine particulate matter (PM2.5) during winter and summer through simultaneous measurements conducted at the Gwangju Institute of Science and Technology in South Korea and the Changping campus of Peking University in China. PM2.5 samples were concurrently collected at both sites, and chemical analyses were conducted to quantify various components, including carbonaceous materials, ionic species, and metals. Although the average PM2.5 concentrations were comparable between the two sites, there were distinct differences in the concentrations of major components. Organic indicator compounds were analyzed to discern the contributions of primary and secondary pollution sources. Changping displayed a mix of primary and secondary pollution, characterized by higher concentrations of primary organic carbon (POC) such as polycyclic aromatic hydrocarbons and hopanes, compared to Gwangju. In contrast, Gwangju demonstrated a higher prevalence of secondary organic carbon (SOC), particularly water-soluble organic carbon not related to biomass burning (WSOCnbb) and various polar organic compounds. The organic mass to organic carbon (OM/OC) ratios estimated using the mass balance method revealed significant differences, with Gwangju showing a higher ratio of 2.3 compared to 1.9 at Changping, indicating a greater influence of secondary pollutants at Gwangju. Additionally, both Changping and Gwangju exhibited higher OM/OC ratios in summer (Changping: 2.0, Gwangju: 2.5) compared to winter (Changping: 1.8, Gwangju: 2.2), indicating seasonal differences in organic mass contributions to PM2.5. These findings underscore the importance of accounting for spatial and seasonal variations in air pollution studies and suggest that updating commonly used OM/OC ratios could enhance the reliability of research outcomes. [ABSTRACT FROM AUTHOR]

In this contribution, we report the study of nuclear resonance magnetic spectroscopy techniques (1H-NMR, 13C-NMR, and 2D-NMR) efficiency in the characterisation of the functional composition of water-soluble organic compounds (WSOC) from atmospheric aerosols. The chosen site was our scientific and technical center of research (CRAPC) situated in Algerian Bou-Ismail city. where the concentrations of PM10 were found to be between 15.66 and 142.19 µg.m−3. As results, 1H-NMR analysis showed the coexistence of biological material and emissions from urban and biomass burning. The dominant source was identified by quantitative integration of each 1H NMR spectral region. By using the HSQC technique, many peaks are revealed in biogenic samples including biomass burning. On the other hand, the identification of the source of various organic compounds and their functional composition is possible through specific NMR spectra, which can also be used to adjust the surrounding organic aerosol sources. [ABSTRACT FROM AUTHOR]

This study investigates the seasonal variation of PM (PM2.5 and PM10) over Bhubaneswar (20.3ºN, 85.827ºE), a smart city on the eastern coast of India. PM2.5 and PM10 ranged from 11.1 to 154.2 µg.m−3 and 20.4–273.8 µg.m−3, respectively. Carbonaceous (EC, OC, WSOC) species and water-soluble inorganic ions (WSIIs) were also examined for PM2.5 samples. SO42− ion was found to be most prevalent among all the species accounting to ~24% of PM2.5 mass, followed by OC (~11%), NH4+ (10%), EC (5%), NO3− (4%), Na+ (4%), K+ (3%), WSOC (3%), Cl− (2%). The relatively low mean OC/EC ratio (1.9±0.4) and WSOC/OC (0.25±0.1) suggest the dominance of fossil fuel emissions over the study site. Additionally, for the first time in the eastern region, the role of several chemical species in light extinction coefficient (bext) and visibility impairment is investigated using IMPROVE algorithm. The mean bext is 311.5±141.8 Mm−1 during the observation period, with a dominant contribution from (NH4)2SO4 followed by carbonaceous species (OM and EC). However, visibility levels sharply diminished by <9 km during winter than post-monsoon (<10 km), pre-monsoon (<19 km) and monsoon (<27 km) over Bhubaneswar. [ABSTRACT FROM AUTHOR]

Throughout the cold and the warm periods of 2020, chemical and toxicological characterization of the water-soluble fraction of size segregated particulate matter (PM) (<0.49, 0.49–0.95, 0.95–1.5, 1.5–3.0, 3.0–7.2 and >7.2 μm) was conducted in the urban agglomeration of Thessaloniki, northern Greece. Chemical analysis of the water-soluble PM fraction included water-soluble organic carbon (WSOC), humic-like substances (HULIS), and trace elements (V, Cr, Mn, Fe, Ni, Cu, Zn, As, Cd and Pb). The bulk (sum of all size fractions) concentrations of HULIS were 2.5 ± 0.5 and 1.2 ± 0.3 μg m−3, for the cold and warm sampling periods, respectively with highest values in the <0.49 μm particle size fraction. The total HULIS-C/WSOC ratio ranged from 17 to 26% for all sampling periods, confirming that HULIS are a significant part of WSOC. The most abundant water-soluble metals were Fe, Zn, Cu, and Mn. The oxidative PM activity was measured abiotically using the dithiothreitol (DTT) assay. In vitro cytotoxic responses were investigated using mitochondrial dehydrogenase (MTT). A significant positive correlation was found between OPmDTT, WSOC, HULIS and the MTT cytotoxicity of PM. Multiple Linear Regression (MLR) showed a good relationship between OPMDTT, HULIS and Cu. [ABSTRACT FROM AUTHOR]

Carbonaceous aerosols (CA) are crucial components in the atmospheric PM 2.5 and derived from diverse sources. One of the major sources for CA is from the incomplete combustion of bituminous coal that has been prevailingly used by household stoves in rural areas for heating during winter. To efficiently eliminate the CA emission, a new household stove (NHS) was developed based on a novel combustion technology and CA emissions from the NHS and a traditional household stove (THS) were comparably investigated under the actual stove operation conditions in a farmer's house. Compared with the THS, the emission factors of organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon (WSOC) from the NHS were reduced by 96%±1%, 98%±1%, and 91%±1% under the flaming process and 95%±1%, 96%±2%, and 83%±4% under the smoldering process, respectively. Additionally, the mass absorption efficiency of WSOC from the NHS reduced by 3 folds and the radiative forcing by WSOC relative to EC shrank remarkably by a factor of 3-8. Based on the reduction of emissions and light absorption of WSOC, the promotion of the NHS offers a possible solution to achieve the clean combustion of residential solid fuel. [Display omitted] [ABSTRACT FROM AUTHOR]

A high time resolution synchronous sampling method al ong with determination of stable carbon isotopes of gaseous water-soluble organic carbon (WSOCg) and particulate water-soluble organic carbon (WSOCp) was realized in this research through equipment modification and method improvement. It was found that WSOCg has significant higher concentration than WSOCp and a more depleted δ13C. Both concentrations of WSOCp and WSOCg have the seasonal variation characteristics of high in winter (WSOCp=15.7±3.9µg/m³; WSOCg=42.4±6.0µg/m³) and low in summer (WSOCp=5.9±1.8µg/m³; WSOCg=25.2±5.2µg/m³), with greater increase in WSOCp (167%) than that in WSOCg (68%). During wintertime, WSOCp and WSOCg had similar daily variation characteristics of concentration, and opposite daily variation characteristics of δ13C. WSOCp had a bimodal distribution with obvious low value at sunrise and sunset, while δ13C WSOCp had a unimodal distribution with low in daytime (-24.6±1.1‰) and high in nighttime (- 22.3±1.7‰). WSOCg and δ13C-WSOCg had same distribution with high in daytime and (49.3±8.8µg/m³; -27.9±1.1‰) low in nighttime (38.3±4.6µg/m³; -29.9±0.4‰). Combining the δ13C variation characteristics with the synchronous observation results of meteorological conditions, gaseous precursor pollutants, gaseous oxidants, gaseous acids and fine particle components, the restriction factors of WSOC gas-particle distribution mechanism were discussed. The presence of radiation rather than its intensity decided whether generations process of WSOCp and WSOCg are divided, for δ13C-WSOC of two phases showed significant correlation only during daytime. Meteorological conditions, gaseous precursor pollutants, gaseous oxidants and gaseous acids restrict the gas particle distribution of WSOC by affecting the aging process of WSOCp and WSOCg, gas particle conversion ratio of semi-volatile organic compounds (SVOC) and the gas phase and liquid phase generation ratio of WSOCp. At the same time, the gas-particle distribution process of WSOC is strongly related to the formation of secondary inorganic ions (nitrate, sulfate, ammonium), and the gas-particle distribution between gaseous nitrous acid and nitrite. [ABSTRACT FROM AUTHOR]

As mankind pays attention to environmental protection and reuse of resources, more and more exogenous materials are being utilized for soil improvement, such as straw, sediment, etc. However, further research is needed on the mechanism of how sediments and other exogenous materials change soil properties. In this study, the changes of soil water soluble organic carbon (WSOC) and soil dissolved organic matter (SDOM) in the process of resource utilization of sediment and other exogenous materials were investigated. Different exogenous substances such as river sediment (RS), lake sediments (LS), straw (SS), algae (AS), Myriophyllum verticillatum L. submerged plants (MS) and livestock manure (FS) were added to the soil, and fluorescence spectroscopy combined with parallel factor analysis was used to explore the characteristics of WSOC changes and SDOM sources in the treated soil. The results showed that the SDOM fluorescence intensity changes show the total fluorescence intensity of the three groups of SS, FS, and MS was significantly higher (P LS (58.2 mg/kg) > FS (45.6 mg/kg) > RS (44.8 mg/kg) > AS (41.4 mg/kg) > SS (39.4 mg/kg) > CK (32.7 mg/kg). the MS group increased the most, reaching a percentage of 220%. The parallel factor analysis of SDOM three-dimensional fluorescence spectra showed that SDOM in soil mainly contains three components, groups contain protein-like, humus-like and tyrosine-like amino acids. In the initial stage, protein-like substances are the main components, and after 50 days, humus-like substances become the main components of SDOM in each treated soil. Among them, the FS group has the highest humus-like content. According to the fluorescence intensity, the SS, FS and MS groups have significant effects on increasing the content of soil water-soluble organic matter, and the SS group has the strongest effect. In summary, sediment and straw, algae, Myriophyllum verticillatum L., livestock manure can change the content of SDOM and WSOC in the soil can change the content of SDOM and WSOC in the soil, enhance the degree of soil vitality, increase the vitality of the soil, and improve the structure, composition, and quality of the soil. This research provided theoretical guidance and technical support for the resource utilization of sediment, straw, algae, submerged plants and livestock manure.

Throughout the cold and the warm periods of 2020, chemical and toxicological characterization of the water-soluble fraction of size segregated particulate matter (PM) (7.2 μm) was conducted in the urban agglomeration of Thessaloniki, northern Greece. Chemical analysis of the water-soluble PM fraction included water-soluble organic carbon (WSOC), humic-like substances (HULIS), and trace elements (V, Cr, Mn, Fe, Ni, Cu, Zn, As, Cd and Pb). The bulk (sum of all size fractions) concentrations of HULIS were 2.5 ± 0.5 and 1.2 ± 0.3 μg m−3, for the cold and warm sampling periods, respectively with highest values in the mDTT, WSOC, HULIS and the MTT cytotoxicity of PM. Multiple Linear Regression (MLR) showed a good relationship between OPMDTT, HULIS and Cu.

Inorganic salts present in the atmosphere may affect the composition and abundance of secondary organic aerosol. Here, we quantify the effects of salt identity, salt concentration (ionic strength), and solution pH on the partitioning of ambient water‐soluble organic gases (WSOCg) at a site in the eastern United States. The experimental pH (pH = 1–6) and ionic strengths (10−3–101 mol kg−1) span a wide range of conditions found in atmospheric particles, clouds, and fog droplets. Chloride salts (NaCl, NH4Cl, and KCl) exhibit a strong salting‐out effect at all ionic strengths >0.005 mol kg−1 and pH = 1.8–6. In contrast, sulfate salts (Na2SO4, (NH4)2SO4, and K2SO4) induce both salting‐in and salting‐out behaviors, depending on ionic strength and pH. These results suggest that monovalent cations have minimal effect, while ionic strength, pH, and anion identity exert strong effects on the partitioning of ambient organic gases in the atmosphere. Plain Language Summary: The presence of salts in atmospheric aerosols, fogs, and clouds may change the amount of dissolved organic compounds. This may lead to changes in their physical and chemical properties, and chemical reactions that produce lower‐volatility organic compounds (secondary organic aerosol, SOA). Inorganic salts can both enhance ("salting‐in") or inhibit ("salting‐out") the partitioning of organic gases to aqueous solutions relative to that in pure water, though their importance in the atmosphere is largely unconstrained at present. We performed ambient air sampling to measure the effects of salt identity, salt concentration, and solution pH on the absorption of VOCs into aqueous solutions. A wide range of pH (pH = 1–6) and salt concentrations (ionic strength = 10−3–101 mol kg−1) representative of atmospheric particles, clouds, and fog droplets were studied. Chloride salts (NaCl, NH4Cl, and KCl) exert strong salting‐out effects at all ionic strengths >0.005 mol kg−1 and pH = 1.8–6, while sulfate salts (Na2SO4, (NH4)2SO4, and K2SO4) exhibit both salting‐in or salting‐out behavior based on the salt concentration and solution pH. It was also found that anions induced strong salting effects, while singly charged cations showed minimal salting effects. Key Points: Anion identity, pH, and ionic strength strongly affect the partitioning of ambient organic gases in aerosol, fog, and cloud waterMonovalent cations do not have a significant effect on the salting behavior of ambient organic gasesChloride salts always induce salting‐out, while sulfate salts exert both salting‐in or salting‐out, depending on pH and ionic strength [ABSTRACT FROM AUTHOR]

In this study we present the seasonal chemical characteristics and potential sources of PM10 at an urban location of Delhi, India during 2010˗2019. The concentrations of carbonaceous aerosols [organic carbon (OC), elemental carbon (EC), water soluble organic carbon (WSOC) and water insoluble organic carbon (WIOC)] and elements (Al, Fe, Ti, Cu, Zn, Mn, Pb, Cr, F, Cl, Br, P, S, K, As, Na, Mg, Ca, B, Ni, Mo, V, Sr, Zr and Rb) in PM10 were estimated to explore their possible sources. The annual average concentration (2010–2019) of PM10 was computed as 227 ± 97 µg m−3 with a range of 34˗734 µg m−3. The total carbonaceous aerosols in PM10 was accounted for 22.5% of PM10 mass concentration, whereas elements contribution to PM10 was estimated to be 17% of PM10. The statistical analysis of OC vs. EC and OC vs. WSOC of PM10 reveals their common sources (biomass burning and/or fossil fuel combustion) during all the seasons. Enrichment factors (EFs) of the elements and the relationship of Al with other crustal metals (Fe, Ca, Mg and Ti) of PM10 indicates the abundance of mineral dust over Delhi. Principal component analysis (PCA) extracted the five major sources [industrial emission (IE), biomass burning + fossil fuel combustion (BB + FFC), soil dust, vehicular emissions (VE) and sodium and magnesium salts (SMS)] of PM10 in Delhi, India. Back trajectory and cluster analysis of airmass parcel indicate that the pollutants approaching to Delhi are mainly from Pakistan, IGP region, Arabian Sea and Bay of Bengal. [ABSTRACT FROM AUTHOR]

Droughts are recognized to impact global biogeochemical cycles. However, the implication of desiccation on in-stream carbon (C) cycling is not well understood yet. We subjected sediments from a lowland, organic rich intermittent stream to experimental desiccation over a 9-week-period to investigate temporal changes in microbial functional traits in relation to their redox requirements, carbon dioxide (CO2) and methane (CH4) fluxes and water-soluble organic carbon (WSOC). Concurrently, the implications of rewetting by simulated short rainfalls (4 and 21 mm) on gaseous C fluxes were tested. Early desiccation triggered dynamic fluxes of CO2 and CH4 with peak values of 383 and 30 mg C m−2 h−1 (mean ± SD), respectively, likely in response to enhanced aerobic mineralization and accelerated evasion. At longer desiccation, CH4 dropped abruptly, likely because of reduced abundance of anaerobic microbial traits. The CO2 fluxes ceased later, suggesting aerobic activity was constrained only by extended desiccation over time. We found that rainfall boosted fluxes of CO2, which were modulated by rainfall size and the preceding desiccation time. Desiccation also reduced the amount of WSOC and the proportion of labile compounds leaching from sediment. It remains questionable to which extent changes of the sediment C pool are influenced by respiration processes, microbial C uptake and cell lysis due to drying-rewetting cycles. We highlight that the severity of the dry period, which is controlled by its duration and the presence of precipitation events, needs detailed consideration to estimate the impact of intermittent flow on global riverine C fluxes. [ABSTRACT FROM AUTHOR]

The impact of the Three-year Action Plan for winning the "blue sky defense battle" on the pollution levels and chemical characteristics of fine particulate matter has been intensively studied over the past few years. However, the effect of air pollution control on light absorption of brown carbon remains unclear. In this study, the light absorption and fluorescence properties of water- and methanol-soluble organic carbon (WSOC and MSOC) in PM 2.5 in Tianjin and Handan in North China Plain were measured and evaluated for three consecutive winters during the Three-year Blue-Sky Action (2018–2020). Overall, the WSOC and MSOC mass concentrations and light absorption coefficients of WSOC and MSOC at 365 nm generally decreased from 2018 to 2020, indicating that the emission of solvent-soluble organic carbon has been effectively controlled with the implementation of pollution abatement measures, such as the enforcement of clean energy policies. The light absorption coefficient and mass absorption efficiency at 365 nm of MSOC were 1.41–3.82 and 1.13–1.72 times higher than that of WSOC, respectively. Fluorescent spectra coupled with parallel factor analysis indicated that less‑/highly‑oxygenated humic-like (LO-/HO-HULIS) and non-N aromatic species (non-Nas) were the major fluorophores in both WSOC and MSOC in the two cities, with LO-HULIS and HO-HULIS as two major contributors to WSOC light absorption, while both HULIS and non-Nas fluorophores had a strong correlation with MSOC light absorption. Correlation analysis with source tracers and fluorescent indices indicated that the influence of combustion emissions remains significant, and secondary formation made a non-negligible contribution to the light absorption and fluorescent components of WSOC and MSOC in both cities. This work will contribute to a better understanding of the evolution of concentration levels and optical properties of WSOC and MSOC during pollution abatement and will inform the subsequent development of measures to achieve a win-win situation for both air quality and climate change. • Water- and methanol-soluble organic carbon concentrations overall decreased with the Blue-Sky War. • Light absorption and direct radiative forcing by brown carbon decreased with the Blue-Sky War. • The impact of combustion emissions remains significant and requires continued attention. [ABSTRACT FROM AUTHOR]

One-hour resolution observations of stable carbon isotopes in both gaseous water-soluble organic carbon (WSOCg) and particulate water-soluble organic carbon (WSOCp) were conducted at a city site in the Yangtze River Delta. WSOCg exhibited significantly higher concentrations and lower 13C compared to WSOCp. The presence of radiation emerged as a crucial factor influencing the gas-particle partitioning mechanism of WSOC. There appeared to be distinct formation processes for WSOCp and WSOCg during nighttime, except on hazy days with elevated particulate matter concentrations. Gas-particle partitioning of WSOC may become inactive in environments with high temperatures and ozone concentrations, while it may become active in environments characterized by high relative humidity (RH) and elevated WSOCg concentrations. When addressing WSOC pollution, it's essential to focus not only on its sources but also on the suitable environmental conditions for gas-particle partitioning. Active gas-particle partitioning of WSOC may coincide with the formation of secondary inorganic ions (NH 4 +, NO 3 − and SO 4 2−). Thus, in targeting WSOC sources, it's imperative to implement coordinated strategies to control the sources of secondary inorganic ions. • Photochemical production is a critical mechanism of WSOC gas-particle partitioning during the wintertime. • δ13C–WSOC is influenced by both WSOC source compositions, meteorological conditions and gaseous pollutants concentrations. • Secondary inorganic ions are formed synergistically during gas-particle partitioning of WSOC. [ABSTRACT FROM AUTHOR]

Oceans are important sources of microbes in atmospheric aerosols; however, information about the characteristics of airborne microbes and their influencing factors over oceans is lacking. Here we report the characteristics of the microbial abundance and activity in aerosols sampled near the sea surface over the South China Sea (SCS) from May to June 2016. The airborne microbial concentration range in the aerosols was 1.68×105 to 4.84×105 cells m−3 over the SCS, reflecting an average decrease of 40%–54% over the SCS compared with that in the samples from the coastal region of Qingdao. About 63%–76% of the airborne microbes occurred in coarse particles (> 2.1 µm), with a variable size distribution over the SCS. The microbial activity range in aerosols, measured by the fluorescein diacetate (FDA) hydrolysis method, was 2.09–11.97 ng m−3 h−1 sodium fluorescein (SF) over the SCS, which was 15%–79% lower than that over the coastal region. These values reflected a different spatial distribution over the SCS from that of the microbial concentration. Except for certain samples, all samples had 68% of the microbial activity occurring in coarse particles. Correlation analysis showed that the microbial abundance and activity were positively correlated with the aerosol, organic carbon (OC), and water-soluble organic carbon (WSOC) concentrations, indicating that the airborne microbes may be related to the reactions of certain water-soluble organic chemicals in the atmosphere. Moreover, the concentrations of airborne microbes were significantly negatively correlated with the horizontal offshore distance. The microbial concentration and activity were significantly correlated with wind speed. [ABSTRACT FROM AUTHOR]

Atmospheric aerosols are a branch of active research in recent decades. The deposition of light-absorbing substances on high-altitude glaciers causes substantial adverse impacts on the cryospheric environment, cryosphere-hydrology, and climate system. Although, the concentrations of water-soluble organic carbon (WSOC) in snow/ice on glaciers of Tibetan Plateau (TP) have been reported, their transfer processes and optical properties in the context of summer precipitation-atmosphere-snow-river water continuum are seldom studied. In this study, we have systematically examined some scientific issues associated with WSOC concentrations and light absorption properties of WSOC in various forms of samples from the Mt. Yulong region. Statistical results demonstrate that the spatial distribution of WSOC in the snow of Baishui glacier was heterogeneous. The average WSOC concentrations of each snowpit were significantly decreased, and its light-absorbing properties were significantly elevated with the time extension. Aerosol WSOC concentrations and light absorption have distinct spatial disparity and seasonal variation. Pre-monsoon and monsoon have the highest and lowest WSOC content, respectively. Whereas the light-absorbing properties present contrasting seasonal trends. Rivers of which runoff was supplied by glacier meltwater have significantly lower WSOC concentrations (e.g., 0.42 ± 0.03 mg L−1) compared with other forms of water bodies. Mass absorption cross-section of WSOC (MAC-WSOC) in multiple snow and meltwater samples was significantly different and type-dependent. Atmospheric aerosol has the lowest MAC-WSOC value among the four types of samples, which was likely associated with exhaust emissions from private vehicles and tour buses. Statistical results indicated that the average AAE330-400 values of various snow/ice samples are subequal. Snow of glaciers supplies a desirable platform for the deposition of gaseous materials which experienced long-range transport in high altitude zones. Biomass-burning emissions made an immense contribution to the WSOC deposition over the study area, as demonstrated by the distribution of active fire points. However, this preliminary study represents the first systematic investigation of WSOC deposition in southeastern TP. Further robust in-situ field investigations and laboratory measurements are urgently necessary to improve our understanding of the transfer process and optical property of WSOC.

Water-soluble organic carbon (WSOC) widely stored in glaciers from local and distant sources, and then released it to downstream environments under a warming climate. Climatic driven changes to glacial run-off are larger and represent an important flux of organic carbon. However, very few WSOC data are currently available to fully characterize WSOC variation in the temperate glacierized regions of the Tibetan Plateau (TP). This study first systematically evaluated the concentration characteristics and light absorbing property of WSOC, and insoluble particulate carbon (IPC) in snow and ice of a typical temperate glacier on Mt. Yulong. Average concentrations of WSOC were 0.61 ± 0.21 mg L−1 in Baishui glacier on Mt. Yulong. WSOC concentrations in surface aged snow were dramatically decreased with the time extension during the entire monsoon season due to extensive glacial melting and scavenging effects by meltwater. The MAC values of WSOC calculated at 365 nm was 6.31 ± 0.34 m2 g−1 on Mt. Yulong, and there exists distinct spectral dependence of MACwsoc within the wavelength range (260 – 700 nm). The low AAE330–400 values suggest the light absorption of WSOC is more spectrally neutral. The flux of WSOC in Baishui glacier was 0.99 gC m−2 yr−1, while the IPC flux was 4.77 gC m−2 yr−1. Total WSOC storage in the Baishui glacier was estimated to be 1.5 tone C and total IPC storage was 7.25 tone C (1 tone = 106 g). Moreover, glacial melting was reinforced by the soluble and insoluble light absorbing impurities (ILAIs) in glaciers, Baishui glacier can be considered as a fraction of carbon source under the scenario of a warming climate, more importantly, WSOC in snow and ice needs to be taken into account in calculating the radiative forcing of ILAIs and accelerating glacial melting.

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. [ABSTRACT FROM AUTHOR]

Water-soluble organic compounds (WSOC) and dichloromethane: methanol-soluble organic compounds (DMSOC) in polar organic compounds (POCs) present in emissions from a diesel truck were characterized by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The main compositions and molecular structures of WSOC and DMSOC were investigated and classified into three groups based on their elemental compositions: CHO, CHON, and S-containing compounds (CHONS and CHOS) (namely WSOC CHO ; WSOC CHON ; WSOC OS ; DMSOC CHO ; DMSOC CHON and DMSOC OS). The main results are as follows. (1) The order of groups in WSOC and DMSOC in terms of peak response was CHO (WSOC: 52.2% and DMSOC: 64.5%), CHON (WSOC: 43.4% and DMSOC:25.9%), and S-containing compounds (WSOC: 4.35% and DMSOC: 9.57%). (2) The relative response of compounds with low H/C and O/C ratios and double-bond equivalents (DBE) > 10 in WSOC CHO was twice that of DMSOC CHO , indicating that the WSOC emitted by diesel trucks might contain many highly condensed benzene rings. Compounds with H/C = 2 and DBE = 1 in DMSOC CHO showed a strong relative response, presumably due to a fatty-acid structure, which might be used as a tracer to distinguish emissions from diesel trucks and other pollution sources. (3) The strongest relative response in WSOC CHON was for C 11 H 7 O 5 N 2 with an aromaticity equivalent (Xc) = 2.5 and DBE = 9, suggesting that dinitrophenol or methyl nitrophenol might be present. Moreover, C 39 H 76 O 8 N 1 with Xc = 0 and DBE = 2 was dominant in DMSOC CHON , suggesting the presence of carboxylic acids. (4) In both WSOC and DMSOC, long-chain aliphatic and organic sulfate compounds accounted for the largest proportion of S-containing compounds. However, the contents of condensed hydrocarbons and aromatic rings in DMSOC OS were higher than those in WSOC OS , which suggests that DMSOC OS has a strong optical absorption ability. Thus, this study effectively determined the POC compounds of diesel truck emissions and their possible structures, providing data for assessing the environmental effects of using diesel trucks. [Display omitted] • Molecular structures emitted from truck were differences between WSOC and DMSOC. • Condensed benzene and fatty acid were dominated in WSOC CHO and DMSOC CHO. • Dinitrophenol or methyl nitrophenol assumed as tracers for trucks emissions. [ABSTRACT FROM AUTHOR]

In this study, measurements of size-segregated particulate matter (PM) emitted from the combustion of rice straw, pine needles, and sesame stem were conducted in a laboratory chamber. The collected samples were used to analyze amounts of organic and elemental carbon (OC and EC), water-soluble organic carbon (WSOC), humic-like substances (HULIS), and ionic species. The light absorption properties of size-resolved water extracts were measured using ultraviolet-visible spectroscopy. A solid-phase extraction method was first used to separate the size-resolved HULIS fraction, which was then quantified by a total organic carbon analyzer. The results show that regardless of particle cut sizes, the contributions of size-resolved HULIS (=1.94 ×HULIS-C) to PM size fractions (PM0.32, PM0.55, PM1.0, and PM1.8) were similar, accounting for 25.2-27.6, 15.2-22.4 and 28.2-28.7% for rice straw, pine needle, and sesame stem smoke samples, respectively. The PM1.8 fraction revealed WSOC/OC and HULIS-C/WSOC ratios of 0.51 and 0.60, 0.44 and 0.40, and 0.50 and 0.60 for the rice straw, pine needle, and sesame stem burning emissions, respectively. Strong absorption with decreasing wavelength was found by the water extracts from size-resolved biomass burning aerosols. The absorption Ångström exponent values of the size-resolved water extracts fitted between 300 and 400 nm wavelengths for particle sizes of 0.32-1.0 μm were 6.6-7.7 for the rice straw burning samples, and 7.5-8.0 for the sesame stem burning samples. The average mass absorption efficiencies of size-resolved WSOC and HULIS-C at 365 nm were 1.09 (range: 0.89-1.61) and 1.82 (range: 1.33-2.06) m2/g·C for rice straw smoke aerosols, and 1.13 (range: 0.85-1.52) and 1.83 (range: 1.44-2.05) m2/g·C for sesame stem smoke aerosols, respectively. The light absorption of size-resolved water extracts measured at 365 nm showed strong correlations with WSOC and HULIS-C concentrations (R2=0.89-0.93), indicating significant contribution of HULIS component from biomass burning emissions to the light absorption of ambient aerosols.

To understand the characteristics of secondary organic aerosols (SOAs) and estimate their impact on water-soluble organic carbon (WSOC) in urban areas in Japan, we measured 17 organic tracers using gas chromatography–mass spectrometry from particulate matter with an aerodynamic diameter smaller than 2.5 μm collected at five urban sites in Japan during spring and summer. Most anthropogenic, monoterpene-derived, and isoprene-derived SOA tracers showed meaningful correlations with potential ozone in both these seasons. These results indicate that oxidants play an important role in SOAs produced during both seasons in urban cities in Japan. WSOC was significantly affected by anthropogenic and monoterpene-derived SOAs during spring and three SOA groups during summer at most of the sites sampled. The total estimated secondary organic carbons (SOCs), including mono-aromatic, di-aromatic, monoterpene-derived, and isoprene-derived SOCs, could explain the WSOC fractions of 39–63% in spring and 46–54% in summer at each site. Notably, monoterpene-derived and mono-aromatic SOCs accounted for most of the total estimated SOCs in both spring (85–93%) and summer (75–82%) at each site. These results indicate that SOAs significantly impact WSOC concentrations during both these seasons at urban sites in Japan.

The rapid industrialization and economic development in the Pearl River Delta (PRD) region of southern China have led to a substantial increase in anthropogenic emissions and hence frequent haze pollution over the past two decades. In early January 2017, a severe regional haze pollution episode was captured in the PRD region, with a peak PM 2.5 concentration of around 400 μg m−3, the highest value ever reported at this site. During the haze episode, elevated concentrations of oxygenated volatile organic compounds (OVOCs, 33 ± 16 ppbv) and organic matter (41 ± 15 μg m−3) were observed, indicating the enhanced roles of secondary organic aerosols (SOAs) in the formation of haze pollution. Water-soluble organic carbon (WSOC, 12.8 ± 5.5 μg C m−3) dominated the organic aerosols, with a WSOC/OC ratio of 0.63 ± 0.12 and high correlation (R = 0.85) with estimated secondary organic carbon (SOC), suggesting the predominance of a secondary origin of the measured organic aerosols during the haze episode. Four carboxylic acids (oxalic, acetic, formic, and pyruvic acids) were characterized in the aerosols (1.30 ± 0.38 μg m−3) and accounted for 3.6 ± 1.2% of WSOC in carbon mass, with oxalic acid as the most abundant species. The simultaneous measurements of volatile organic compounds (VOCs), OVOCs, and organic acids in aerosols at this site provided an opportunity to investigate the relationship between the precursors and the products, as well as the potential formation pathways. Water-soluble aldehydes and ketones, predominantly produced via the oxidation of anthropogenic VOCs (mainly propane, toluene, n-butane, and m, p-xylene), were the main contributors of the organic acids. The formation of OVOCs is largely attributed to gas-phase photochemical oxidation, whereas the WSOC and dicarboxylic acids were produced from both photochemistry and nocturnal heterogeneous reactions. These findings provided further insights into the oxidation and evolution of organic compounds during the haze pollution episode. Unlabelled Image • Simultaneous measurement of VOCs, OVOCs, and organic aerosol during a haze episode • Enhanced contribution of oxygenated organic matter in haze pollution • Secondary formation of OVOCs from industrial solvent and traffic-emitted VOCs • Photochemical and nocturnal heterogeneous processes are of comparable significance. • Aldehydes and ketones from VOCs oxidation are the main precursors of organic acids. [ABSTRACT FROM AUTHOR]

To understand the influences of emission sources, transport and environmental factors on the characteristics of organic carbonaceous aerosols in the marine area, organic carbon (OC) and water-soluble organic carbon (WSOC) were measured in atmospheric samples collected from the coastal region and over the Bohai and Yellow Seas from 2015 to 2016. Compared with the averages of 19.28 and 10.61 μg·m−3 in the coastal samples, the average concentrations of OC and WSOC decreased to 2.17 and 1.54 μg·m−3 in the marine aerosol samples, respectively. WSOC contributed 60% to OC in Qingdao, while 68.4% to OC over the ocean, suggesting that WSOC is likely influenced by the dissolved organic carbon (DOC) in surface seawater. The highest OC/EC ratios (6.56) were observed in the samples collected from the air masses originating from the north land source, indicating that OC mainly comes from anthropogenic sources. The OC concentrations in the air mass samples from marine sources were only 50% of those in the samples from terrestrial sources. A negative correlation between the WSOC and transport distance over the sea and decreased OC/EC ratios were observed, which indicated that the contribution of secondary organic carbon (SOC) to OC decreased during the transport from land to sea. OC increased by 88.5% under the influence of Asian dust, while WSOC did not exhibit substantial changes. The positive matrix factorization (PMF) model showed that anthropogenic sources were the major source of carbonaceous aerosols, contributing 70% of the OC in Qingdao. The positive correlation between OC and particulate matter (PM) suggested that the OC affected the air quality. • Organic aerosols contained approximately 60% of WSOC in TSP. • OC and WSOC decreased by 88.7% and 85.4% from land to sea, respectively. • Contribution of SOC to organic compounds decreased during the transport from land to sea. • Anthropogenic sources contributed 70% for organic aerosols. [ABSTRACT FROM AUTHOR]

Measurements for size-resolved chemical composition were made at the Anmyeon Island station on the western coast of the Republic of Korea between May 28 and June 20, 2016. This study determined the main chemical compositions of size-resolved particulate matter (i.e., organic carbon, elemental carbon, water-soluble organic carbon, water-soluble ions, and benzene carboxylic acids) from a total of eight chemically size-resolved sets using micro-orifice uniform deposit impactors. The sum of the species presents a prominent accumulation mode peak at a diameter of 0.56 μm without the coarse mode peak. In the accumulation mode, SO42− (49.3%) was the dominant particle component in the size range of 0.1–1.8 μm. Organic carbon and elemental carbon accounted for 13.5% and 0.4%, respectively. Benzene carboxylic acids indicate the accumulation mode peak at the diameter of 0.56 μm. The size-resolved equivalent ion concentration ratios between all measured cations and anions and the ion neutralization model, which uses four major ions, were compared. As a result, the concentration of Na+ is of importance in the accumulation mode for the equivalent ion concentration. [ABSTRACT FROM AUTHOR]

Levoglucosan (LG), water soluble organic carbon (WSOC) and potassium (K+), and the light absorption at 365 nm (Abs365) of the extracted WSOC are measured in PM2.5 samples collected from November 2011 to July 2013 at four coastal urban sites in southeast China (Fuzhou, Putian, Quanzhou and Xiamen). These species are markers of biomass burning and used to determine the contributions of biomass burning to the PM2.5 burden in these locations. LG and WSOC concentrations exhibited a clear seasonal pattern, with a large enhancement in winter and spring and a minimum in summer, and annual means across all sites of 59.2±46.8 ng m−3 and 2.69±1.21 µg C m−3, respectively. The distinctive seasonal patterns of LG and WSOC are more explained by the East Asian monsoon than the upwind varying emission sources according to the HYSPLIT backward trajectories and MODIS fire spots. Observations produced significant correlation (at the p

Despite the significant role water-soluble organic carbon (WSOC) plays in climate and human health, sources and formation mechanisms of atmospheric WSOC are still unclear; especially in some heavily polluted areas. In this study, near real-time WSOC measurement was conducted in Beijing for the first time with a particle-into-liquid-sampler coupled to a total organic carbon analyzer during the springtime, together with collocated online measurements of other chemical components in fine particulate matter with a 1 h time resolution, including elemental carbon (EC), organic carbon (OC), multiple metals, and water-soluble ions. Good correlations of WSOC with primary OC, as well as carbon monoxide, indicated that major sources of WSOC were primary instead of secondary during the study period. The positive matrix factorization model-based source apportionment results quantified that 68 ± 19% of WSOC could be attributed to primary sources, with predominant contributions by biomass burning during the study period. This finding was further confirmed by the estimate with the modified EC-tracer method, suggesting significant contribution of primary sources to WSOC. However, the relative contribution of secondary source to WSOC increased during haze episodes. The WSOC/OC ratio exhibited similar diurnal distributions with O3 and correlated well with secondary WSOC, suggesting that the WSOC/OC ratio might act as an indicator of secondary formation when WSOC was dominated by primary sources. This study provided evidence that primary sources could be major sources of WSOC in some polluted megacities, such as Beijing. From this study, it can be seen that WSOC cannot be simply used as a surrogate of secondary organic aerosol, and its major sources could vary by season and location.

Water-soluble organic carbon (WSOC) widely stored in glaciers from local and distant sources, and then released it to downstream environments under a warming climate. Climatic driven changes to glacial run-off are larger and represent an important flux of organic carbon. However, very few WSOC data are currently available to fully characterize WSOC variation in the temperate glacierized regions of the Tibetan Plateau (TP). This study first systematically evaluated the concentration characteristics and light absorbing property of WSOC, and insoluble particulate carbon (IPC) in snow and ice of a typical temperate glacier on Mt. Yulong. Average concentrations of WSOC were 0.61 ± 0.21 mg L−1 in Baishui glacier on Mt. Yulong. WSOC concentrations in surface aged snow were dramatically decreased with the time extension during the entire monsoon season due to extensive glacial melting and scavenging effects by meltwater. The MAC values of WSOC calculated at 365 nm was 6.31 ± 0.34 m2 g−1 on Mt. Yulong, and there exists distinct spectral dependence of MACwsoc within the wavelength range (260 - 700 nm). The low AAE330-400 values suggest the light absorption of WSOC is more spectrally neutral. The flux of WSOC in Baishui glacier was 0.99 gC m−2 yr−1, while the IPC flux was 4.77 gC m−2 yr−1. Total WSOC storage in the Baishui glacier was estimated to be 1.5 tone C and total IPC storage was 7.25 tone C (1 tone = 106 g). Moreover, glacial melting was reinforced by the soluble and insoluble light absorbing impurities (ILAIs) in glaciers, Baishui glacier can be considered as a fraction of carbon source under the scenario of a warming climate, more importantly, WSOC in snow and ice needs to be taken into account in calculating the radiative forcing of ILAIs and accelerating glacial melting. [ABSTRACT FROM AUTHOR]

Abstract To investigate the influences of anthropogenic activities on carbon aerosols, especially on water-soluble organic carbon (WSOC), PM 2.5 samples were collected at an urban site in a northern city of China during Spring Festival (SF), heating season (HS), and non-heating season (NHS). Carbonaceous species and ions (Ca2+, SO 4 2-, NO 3 -, etc.) were analyzed. Mass concentrations of WSOC and WSIC exhibited higher levels in SF and HS, and high WSOC/OC ratios (67.4%) on average were found. Stronger correlations between WSOC and K+, Cl- occurred in SF, which might due to contributions of firework emissions. Six major sources of PM 2.5 were quantified by PMF model, which contributed in aerosol mass differently in different periods: biomass & firework burning exhibited higher contribution (11.2%) in SF; crustal dust accounted for 19.4% during NHS; secondary particles contributed most (41.0%) in HS; during SF and HS, coal combustion devoted more to aerosol mass. Contributions to WSOC were in the order of vehicular exhaust (41.0% of WSOC) > coal combustion (29.3%) > secondary formation (17.0%) > biomass & firework burning (12.7%). The 82.0% of WIOC were from coal combustion and the rest were devoted by vehicular exhaust. Obvious peaks of firework burning contributions to WSOC were observed on SF's Eve and Lantern Festival. Coal combustion contributed to organic carbons highly in SF and HS. Results implied that anthropogenic activities contributions, like firework burning and coal combustion, significantly influenced the levels of PM 2.5 and WSOC. Highlights • Temporal trends of PM 2.5 , WSOC and relevant chemical species were investigated. • Correlations between WSOC and K+, Cl- indicated firework burning emission. • Source contributions of PM 2.5 , WSOC and WIOC were conducted by PMF. • The vehicular exhaust contributed maximally to WSOC, followed by coal combustion. • Peaks of firework contributions to WSOC occurred on New Year's Eve and Lantern Festival. [ABSTRACT FROM AUTHOR]

Long-term measurements of carbon in HUmic-LIke Substances (HULIS-C) of ambient size-segregated water soluble organic aerosols were performed using a ten-stage low-pressure Berner impactor from December 2014 to November 2015 at an urban background environment in Ljubljana, Slovenia. The mass size distribution patterns of measured species (PM - particulate matter, WSOC - water-soluble organic carbon and HULIS-C) for all seasons were generally tri-modal (primarily accumulation mode) but with significant seasonal variability. HULIS-C was found to have similar distributions as WSOC, with nearly the same mass median aerodynamic diameters (MMADs), except for winter when the HULIS-C size distribution was bimodal. In autumn and winter, the dominant accumulation mode with MMAD at ca. 0.65 μm contributed 83 and 97% to the total HULIS-C concentration, respectively. HULIS-C accounted for a large fraction of WSOC, averaging more than 50% in autumn and 40% in winter. Alternatively, during warmer periods the contributions of ultrafine (27% in summer) and coarse mode (27% in spring) were also substantial. Based on mass size distribution characteristics, HULIS-C was found to be of various sources. In colder seasons, wood burning was confirmed as the most important HULIS source; secondary formation in atmospheric liquid water also contributed significantly, as revealed by the MMADs of the accumulation mode shifting to larger sizes. The distinct difference between the spring and summer ratios of HULIS-C/WSOC in fine particles (ca. 50% in spring, but only 10% in summer) indicated different sources and chemical composition of WSOC in summer (e.g., SOA formation from biogenic volatile organic compounds (BVOCs) via photochemistry). The enlarged amount of HULIS-C in the ultrafine mode in summer suggests that the important contribution was most likely from new particle formation during higher emissions of BVOC due to the vicinity of a mixed deciduous forest; the higher contribution of HULIS-C in the coarse mode demonstrated that beside soil erosion other sources, such as pollen and plant fragments, could also be responsible. [ABSTRACT FROM AUTHOR]

In this study, the temporal evolution and sources of water-soluble organic carbon (WSOC) in submicron particles at an urban background site in Elche (Spain) were investigated. Measurements of PM 1 (N = 200) were carried out over one year (2021). Samples were analysed for organic carbon (OC), elemental carbon (EC), WSOC, levoglucosan, elements and major ions. A positive matrix factorization (PMF) analysis was performed in order to identify the sources of WSOC on an annual and a monthly basis. During the study period, traffic restrictions due to COVID-19 led to lower concentrations of PM 1 and carbonaceous compounds than expected. The WSOC annual average mass concentration was 0.95 μg⋅m−3, with maximum values during the colder months. The apportionment results indicate that the biomass burning (BB) source contributed 30.63% to WSOC levels, road traffic (RT) accounted for 23.90% of the WSOC, while the contribution of a source related to secondary organic aerosol formation (ammonium sulfate-AS) was 33.80%. Minor sources of WSOC were: soil dust (SD) and secondary nitrate (SN), which contributed 7.44% and 4.22%, respectively, to WSOC concentrations. The WSOC/OC ratio did not exhibit significant variations during the study period, since source contributions were similar for WSOC and OC. The highest values of this ratio were recorded in summer, due to the higher contribution from the AS source to WSOC concentrations. • Sources and monthly evolution of WSOC was analysed at an urban background site. • WSOC exhibited higher levels during the colder months when BB source peaked. • A source related to SOA formation is the responsible for a third of the WSOC. • Average WSOC to OC ratio was 0.46 and it was fairly steady troughout the year. [ABSTRACT FROM AUTHOR]

Anhydrosugars including levoglucosan and mannosan are the most effective organic tracers for biomass burning aerosol in the atmosphere. In this study, to investigate the contribution of biomass burning emissions to the aerosol burden in the Pearl River Delta (PRD) region, China, 24-hour integrated PM2.5 samples were collected simultaneously at four locations, (i) Guangzhou (GZ), (ii) Zhaoqing (ZQ) in Guangdong province, (iii) Hok Tsui (HT) and (iv) Hong Kong Polytechnic University (PU) in Hong Kong, in four seasons between 2006 and 2007. Levoglucosan and mannosan, together with water-soluble inorganic ions and water-soluble organic carbon (WSOC), were determined to elucidate the seasonal and spatial variations in biomass burning contributions. The concentrations of levoglucosan and mannosan were on average 82.4±123 and 5.8±8.6 ng m−3, respectively. The WSOC concentrations ranged from 0.2 to 9.4 µg m−3, with an average of 2.1±1.6 µg m−3. The relative contributions of biomass burning emissions to OC were 33% in QZ, 12% in GZ, 4% at PU and 5% at HT, respectively, estimated by the measured levoglucosan to organic carbon ratio (LG/OC) relative to literature-derived LG/OC values. The contributions from biomass burning emissions were in general 1.7–2.8 times higher in winter than those in other seasons. Further, it was inferred from diagnostic tracer ratios that a significant fraction of biomass burning emissions was derived from burning of hard wood and likely also from field burning of agricultural residues, such as rice straw, in the PRD region. Our results highlight the contributions from biomass/biofuel burning activities on the regional aerosol budget in South China.

Size-segregated PM 10 samples were collected in Guangzhou, China during autumn of 2014. Nine amines, including seven aliphatic amines and two heterocyclic amines, were detected using a gas chromatography-mass spectrometer after derivatization by benzenesulfonyl chloride. The total concentration of the nine amines (Ʃamines) was 79.6–140.9 ng m −3 in PM 10 . The most abundant species was methylamine (MA), which had a concentration of 29.2–70.1 ng m −3 . MA, dimethylamine (DMA), diethylamine (DEA) and dibutylamine (DBA) were the predominant amines in the samples and accounted for approximately 80% of Ʃamines in each size segment. Two heterocyclic amines, pyrrolidine (PYR) and morpholine (MOR), were detected in all samples and had average concentrations of 1.14 ± 0.37 and 1.89 ± 0.64 ng m −3 , respectively, in particles with aerodynamic diameters < 3 μm. More than 80% of Ʃamines were found in particles with diameters <1.5 μm, indicating that amines are mainly enriched in fine particles. All amines exhibited a bimodal distribution with a fine mode at 0.49–1.5 μm and a coarse mode at 7.2–10 μm. The maximum contributions of amines to particles (0.21%) and amines-N to water-soluble organic nitrogen (WSON) (3.1%) were found at the sizes < 0.49 μm. The maximum contribution of amines-C to water-soluble organic carbon (WSOC) was 1.6% over the size range of 0.95–1.5 μm. The molar ratio of Ʃamines to ammonium ranged from 0.0068 to 0.0107 in particles with diameters <1.5 μm, and the maximum ratio occurred in the smallest particles (diameter< 0.49 μm). The average dry deposition flux and velocity of Ʃamines in PM 10 were 7.9 ± 1.6 μg m −2 d −1 and 0.084 ± 0.0021 cm s −1 , respectively. The results of this study provide essential information on the contribution of amines to secondary organic aerosols and dry removal mechanisms in urban areas. [ABSTRACT FROM AUTHOR]

This study investigated the relationship between water-soluble organic compounds of ambient particulate matter (PM) and cellular redox activity collected from May 28 to June 20 of 2016 at the west coastal site in the Republic of Korea during the KORea-US Air Quality (KORUS-AQ) campaign. Automatic four-hour integrated samples operated at a flow rate of 92 L per minute for the analysis of organic carbon (OC), water-soluble organic carbon (WSOC), elemental carbon (EC), water-soluble ions (WSIs), and benzene carboxylic acids (BCAs) were collected on a 47 mm quartz fiber filter. The influence of atmospheric transport processes was assessed by the Weather Research and Forecasting (WRF) model. OC, EC, WSOC, and BCA were determined by SUNET carbon analyzer, total organic carbon (TOC) analyzer, and liquid chromatography-mass spectrometry mass spectrometry (LC-MSMS), respectively. Twenty-four-hour integrated samples were collected for reactive oxygen species (ROS) analysis using a fluorogenic cell-based method to investigate the main chemical classes of toxicity. The results illustrate that WSOC and specific water-soluble species are associated with the oxidative potential of particulate matter. Pairwise correlation scatterplots between the daily-averaged WSOC and ROS (r 2 of 0.81), and 135-BCA and ROS (r 2 of 0.84), indicate that secondary organic aerosol production was highly associated with ROS activity. In addition, X-ray spectral analysis together with secondary electron images (SEIs) of PM 2.5 particles collected during high ROS concentration events clearly indicate that water-soluble organic aerosols are major contributors to PM 2.5 mass. This study provides insight into the components of particulate matter that are drivers of the oxidative potential of atmospheric particulate matter and potential tracers for this activity. [ABSTRACT FROM AUTHOR]

Although Humic-LIke Substances (HULIS) are important contributors to the mass of organic aerosol in airborne particulate matter (PM), little is known about their chemical composition, while, their size-resolved optical properties have not been studied yet. Here, HULIS fractions were isolated from size-resolved aerosol samples (≤0.49, 0.49–0.95, 0.95–3 and 3–10 μm) collected in urban and suburban environments of four European cities during wintertime. The bulk ( i.e. , sum of all size fractions) concentration of HULIS ranged between 1.29 and 2.80 μg m −3 across sites with highest values in the ≤0.49 μm particle size fraction. The contribution of the carbon mass of HULIS (HULIS-C) to the water-soluble organic carbon content (WSOC) of PM was 32–43%, which is typical for urban sites affected by biomass burning. The Mass Absorption Efficiency (MAE), which characterizes the efficiency of absorbing solar energy per carbon mass of HULIS decreased with particle size, suggesting that the finest size fractions contain more light-absorbing chromophores, which could affect the light-absorbing ability of organic aerosols. The good correlation of HULIS with effective biomass tracers such as K + , as well as with secondary inorganic aerosol components, proposed that HULIS had both primary ( i.e. , biomass burning) and secondary sources. The Fourier Transfer Infrared coupled to Attenuation Total Reflectance (FTIR-ATR) spectra demonstrated prevalence of aromatic over carboxylic functional groups in most HULIS fractions, indicating contribution from coal combustion emissions in addition to fresh biomass burning aerosol. The new findings add to better understanding the sources and chemical structure of HULIS in urban and suburban environments. [ABSTRACT FROM AUTHOR]

This article presents the distribution of the dithiothreitol-based (DTT) redox activity of water-soluble airborne particulate matter (PM) from two urban sites in the city of Thessaloniki, northern Greece in four size ranges (<0.49, 0.49-0.97, 0.97-3.0 and >3 μm). Seasonal and spatial variations are examined. The correlations of the mass-normalized DTT activity with the content of PM in water-soluble organic carbon (WSOC) and non-water-soluble carbonaceous species, such as organic and elemental carbon, as well as with solvent-extractable trace organic compounds (polycyclic aromatic hydrocarbons and nitro-derivatives, polychlorinated biphenyls, organochlorines, polybrominated biphenyl ethers) and polar organic markers (dicarboxylic acids and levoglucosan), are investigated. Our study provides new and additional insights into the ambient size distribution of the DTT activity of the water-soluble fraction of airborne PM at urban sites and its associations with organic PM components. [ABSTRACT FROM AUTHOR]

This work reports the day-night differences of a suite of chemical species including elemental carbon (EC), organic carbon (OC), water-soluble organic carbon (WSOC), water-soluble organic nitrogen (WSON), selected polycyclic aromatic hydrocarbons (PAHs), and secondary inorganic ions (NO3-, SO42-, NH4+) in ambient fine particles (PM2.5) collected from 23 July to 23 August 2016 in Changzhou, China. Mass concentrations of PM2.5 and SO42- show a 10-20% increase during daytime, while NO3- concentration decreases by a factor of three from nighttime to daytime due to its semi-volatile nature. PAHs, EC, and WSON show higher mass concentration in the night too. Mass ratios of WSOC to OC are high in both day and night, indicating that secondary organic aerosol (SOA) formation could occur throughout the day, while the slightly higher ratio during daytime suggests a more significant contribution from daytime photochemical oxidation. Strong positive correlations between HULIS-C and WSOC, and HULIS-C with O3 both in day and night, imply that HULIS-C, similar to WSOC, is mainly composed of secondary species. HULIS-C accounted for a large fraction of WSOC, with an average of ~60%. Moreover, the average WSON concentrations are 1.08 and 1.46 μg/m³, constituting ~16% and ~18% of water-soluble total nitrogen in day and night, respectively. Correlation analyses suggest that WSON is also predominantly produced from secondary processes. PAHs concentrations are found to be very low in summer aerosols. Overall, our findings highlight the dominant contribution of secondary processes to the major aerosol components in Changzhou, suggesting proper measures to effectively reduce gaseous precursors are also important to improve air quality. [ABSTRACT FROM AUTHOR]

The chemical composition of the atmosphere changes rapidly due to the amount of air pollutants released every day. The aim of this research was to make an exploratory study on the chemical composition (metals and water-soluble organic fraction) of fine particulate matter (PM) in a region with tropical climate. Multiple sites, with and without the influence of the construction works for the World Cup and Olympic Games, were selected in Rio de Janeiro State, RJ, Brazil. PM samples were collected every 6 days from January to December 2011. This is the first PM data generated by RJ's monitoring network. The PM annual average concentrations in Rio de Janeiro ranged from 9 to 32 μg m. Metals originated from industrial (Cu, Cd, Pb) and traffic (Cr, Mn, Ni, V, and Zn) emissions, as well as those from natural emissions (Na, K, Ca, Ti, Al, Mg, Fe), were quantified. The concentrations of the metals analyzed ranged from 0.4 to 13,000 ng m. The highest concentrations found were related to metals present in the crust, such as Al (1.6 to 6.7 μg m). In the places where there was the presence of railroad minerals, Ca and Mg appeared in higher concentrations than in the other sites. Fe and PM annual and daily average were higher in areas under construction for urban mobility improvements or the Olympic arenas. Even though, the results for Ni, Pb, and Cu were 50% below WHO guidelines. Water-soluble organic carbon (WSOC) concentrations ranged from 0.8 to 4.9 μg m. The highest concentrations (2.4 to 4.9 μg m) were observed in urban areas with intense light vehicle fleet traffic as well as in areas of large industrial influence near highways with intense circulation of heavy vehicles. This is due to the fact that WSOC is mainly formed by the emissions from combustion processes. Studies are needed in order to assess to which extent the WSOC can increase the bioavailability of these and other metals. [ABSTRACT FROM AUTHOR]

PM 2.5 filter sampling was conducted on a daily basis for one year from 2011 to 2012 at an urban site in Beijing. One-third of the samples were subjected to chemical analysis, including water-soluble inorganic ions, organic carbon (OC), elemental carbon (EC) and water-soluble organic carbon (WSOC). The results show that OM (Organic Matter = OC × 1.6; average 50.8% of PM 2.5 ) was the most abundant species, followed by SNA (SO 4 2 − + NO 3 − + NH 4 + ; average 35%); however, SNA contributed more to PM 2.5 in summer and OM contributed more in other seasons. The concentrations of nitrate were higher in summer and autumn than that in winter, suggesting that nitrate had formed in acidic and ammonium-poor environments in summer. WSOC accounted for 26.6% of OC and 8.1% of PM 2.5 and exhibited distinct seasonal variations: the lowest concentration occurred in spring (3.90 ± 1.78 μg/m 3 ) and the highest in autumn (5.82 ± 3.73 μg/m 3 ). The higher WSOC/OC ratio in summer suggests that OC was more aged, oxidized and hygroscopic during this season. The seasonal trend of SOC (Secondary Organic Carbon) was the opposite of WSOC/OC, which may indicate that the OC/EC minimum ratio method was not suitable for estimating SOC in this study. Correlations between WSOC and K + , EC and inorganic ions indicated that WSOC was dominated by secondary formation, except that biomass burning was an important source in autumn. Aqueous chemical processes may play an important role in the formation of WSOC in winter. Meteorological conditions had an important influence on WSOC: positive correlations were observed between WSOC and relative humidity, but there was a negative correlation when humidity was higher than 80% in summer. [ABSTRACT FROM AUTHOR]

A total of 37 atmospheric aerosol samples were collected over the Yellow and Bohai Seas (YBS) during four cruises in autumn, winter, spring and summer from 2017 to 2018. The concentrations of organic carbon (OC) and water-soluble organic carbon (WSOC) ranged from 1.04 to 15.43 μg m−3 and 0.77–5.49 μg m−3, respectively, with higher values in autumn and winter than in spring and summer. WSOC contributed 68.49 % to OC in summer and 34.55 % in winter and was affected by temperature and relative humidity. Dicarboxylic acid showed a predominance of oxalic acid followed by malonic and then succinic acids. The contributions of secondary sources to OC and WSOC were 54 % and 65.3 %, respectively, indicating the importance of secondary aging in improving the water solubility of OC. The dry deposition flux of WSOC over the YBS was estimated to be 0.87 mg m−2 d−1, which might play a potential role in the marine carbon cycle. [Display omitted] • Concentrations of OC and WSOC in the marginal seas were high in autumn and winter and low in spring and summer. • Dicarboxylic acid showed a predominance of oxalic acid followed by malonic and then succinic acids. • High temperature and high relative humidity lead to higher WSOC/OC and diacid-C/WSOC ratios in summer than in winter. • Secondary source contributes more to WSOC than OC. • Dry deposition was an important source of DOC in marginal seawater. [ABSTRACT FROM AUTHOR]

The article presents the Dithiothreitol-based oxidative potential (OPDTT) of PM 2.5 from an urban site in São Paulo, Brazil, in relation to its chemical composition focused on organic carbon (WSOC), Humic-Like Substances (HULIS), water-soluble elements (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd and Pb), ionic species, polycyclic aromatic hydrocarbons (PAHs), and oxy- and nitro-PAH derivatives (OPAHs and NPAHs). Seasonal variations of the intrinsic (mass-normalized) oxidative potential (OPmDTT) and the extrinsic (air volume-normalized) oxidative potential (OP v DTT), as well as of targeted chemical components were investigated. Furthermore, a series of statistical analyses, including correlation, and multi linear regression (MLR) were performed to identify the most significant species contributing to the measured OPDTT. Although explaining a relatively small percentage of the OP variability (R2 = 0.389), the MLR model indicated HULIS as the major OPmDTT carrier contributing 58% on average. Two receptor modelling approaches were further employed for the source apportionment of OP v DTT (a) direct Positive Matrix Factorization (PMF), and (b) a combination of PMF of PM 2.5 mass concentrations followed by Multiple Linear Regression (PMF - MLR). Both approaches yielded meaningful, although somewhat different, results with direct PMF indicating vehicular emissions as the major contributor (76.3 ± 58.3%) of OP v DTT followed by industrial emissions (16.9 ± 17.7%), and biomass burning (7.3 ± 8.6%), whereas according to the PMF-MLR approach, the main contributors to OP v DTT were biomass burning (40.7 ± 26.3%), industrial emissions (24.3 ± 22.5%), vehicular emissions (20.5 ± 15.2%), and secondary aerosol (14.5 ± 15.0%). The study provides new and additional insights on the oxidative activity of ambient PM highlighting the importance of identifying its linkage with chemical constituents and emission sources for developing air quality control strategies aiming to protect human health. [Display omitted] • Dithiothreitol oxidative potential (OPDTT) of PM 2.5 was investigated in São Paulo. • OPDTT was an intrinsic property of PM 2.5 related to its composition than mass. • HULIS appeared to be a significant contributor to OPmDTT. • Direct PMF indicated vehicular emissions as the major source of OPvDTT. • The PMF - MLR approach indicated biomass burning as the major source of OPvDTT. [ABSTRACT FROM AUTHOR]

We characterised surface-active substances (SASs) in aqueous extract of atmospheric aerosols by using phase sensitive alternating current voltammetry. The electrochemical method has mainly been used for the quantification of surfactants in sea water but has not been applied to atmospheric aerosols yet. The advantage of the method is its simplicity and sensitivity that enables direct analysis of aerosol extracts without the need for sample concentration. Aerosol samples were collected at Middle Adriatic Martinska station influenced by different air masses as well as from urban (Zagreb, Croatia) and rural (K-puszta, Hungary) areas from late spring to early autumn in 2010. The highest SAS concentrations, expressed in equivalents of T-X-100, ranging from 0.34 to 0.91 µg m−3 were detected in urban samples. The SAS concentrations obtained for marine, regional and continental samples ranged from 0.14 to 0.31, 0.18 to 0.42 and 0.07 to 0.28 µg m−3, respectively. The SAS concentrations in K-puszta aerosols ranged from 0.13 to 0.46 µg m−3. Investigation of humic-like substances isolated from K-puszta samples (2008) confirmed their significant surfactant nature. Different SAS chemistry was noticed for urban and non-urban samples. Investigations at different pH revealed anionic character of SASs in aerosol samples.

The chemical characterization of water-soluble organic carbon in ash emitted from a coal combustion boiler has not been reported yet. A total of 5 ash samples were collected from the outlet of an electrostatic precipitator in a commercial 500 MW coal-fired power plant, with their chemical characteristics investigated. XAD7HP resin was used to quantify the hydrophilic and hydrophobic water-soluble organic carbons (WSOC), which are the fractions of WSOC that penetrate and remain on the resin column, respectively. Calibration results indicate that the hydrophilic fraction includes aliphatic dicarboxylic acids and carbonyls (4-5 carbons), phenols, aromatic acids, cyclic acid and humic acid. The average mass of the WSOC in the ash samples was found to depend on the bituminous coal type being burned, and ranged from 163 to 259 μg C/g of ash, which corresponds to 59-96 mg C of WSOC/kg of coal combusted. The WSOC mass accounted for 0.02-0.03 wt% of the used ash sample mass. Based on the flow rate of flue gas produced from the combustion of the blended coals in the 500 MW coal combustion boiler, it was estimated that the WSOC particles were emitted to the atmosphere at flow rates of 4.6-7.2 g C/hr. The results also indicated that the hydrophilic WSOC fraction in the coal burned accounted for 64-82% of the total WSOC, which was 2-4 times greater than the mass of the hydrophobic WSOC fraction.

Exploring the secondary formation of water-soluble organic carbon (WSOC) and its influencing factors is critical to understand the impact of WSOC on climate change and air quality. In this study, PM 2.5 samples were collected from Sep.2017 to Aug.2018 in Urumqi, Northwest China. These samples were analyzed for WSOC, organic and element carbon (OC, EC), and water-soluble ions. The levels of WSOC ranged from 0.57 to 19.7 μg C/m3 with an annual mean of 6.08 ± 3.50 μg C/m3, accounting for 53% of OC. The observed ratios of WSOC to OC (0.35–0.77) were within the range of those for biomass burning and secondary organic aerosol (SOA). In addition, WSOC was positively correlated with the biomass burning tracer (K+) and secondary species (sulfate, nitrate, and ammonium). All of these observational evidences indicated that atmospheric WSOC over Urumqi were mainly from biomass burning and SOA. Based on a K-tracer approach, we estimated WSOC from biomass burning (WSOC BB) and SOA (WSOC sec). Our results suggested that WSOC sec was dominated over WSOC BB in four seasons with the highest level in winter (8.22 ± 3.82 μg C/m3) and the lowest in summer (2.91 ± 1.63 μg C/m3). The WSOC sec concentrations and WSOC sec fractions in OC were high under the conditions of high relative humidity, low temperature and wind speed. WSOC sec was positively correlated with liquid water content (LWC) but exhibited no dependence on aerosol acidity (in-situ pH). This indicated that the heterogeneous formation of WSOC sec in the air of Urumqi was largely associated with LWC rather than acidity. • The level of WSOC in Urumqi was significant higher than of other humid cities, overall. • Biomass-burning and secondary formation contributed to the measured WSOC. • Promoted secondary formation of WSOC at high relative humidity, low temperature and wind speed. • WSOC sec was positively correlated with liquid water content (LWC) but exhibited no dependence on aerosol acidity. [ABSTRACT FROM AUTHOR]