Water-soluble Inorganic Species Research Articles

Temporal profile of ionic species and n-alkanes composition of PM10 in a rural environment of Western Himalaya

The temporal profile of PM10 and its composition comprising water-soluble ionic species and n-alkanes studied over the 14 months was segregated into three seasons: winter, summer, and monsoon. The average PM10 concentration exceeds the prescribed National PM10 limits in summer and winter. The PM10 concentration was highest in summer, followed by winter, and lowest in monsoon. Water-soluble inorganic ionic species— major cations (Ca2+, Mg2+, Na+, K+, and NH4+) and anions (F−, Cl−, NO3− and SO42−) contributed an average 30.7% to PM10. The ionic species displayed significant variation, with the highest concentration in winter and the lowest in the monsoon. The secondary inorganic ions, SO42−, NO3−, and NH4+, contributed 84% to the total ionic mass. The ion balance study revealed a strong correlation between anion and cation charge equivalents, suggesting their main contribution to PM10. The neutralization of NO3− + SO42− with NH4+ suggested, NH4+ being the main neutralizing species. n-alkanes concentration in PM10 was significant and showed seasonal variation, highest in the winters and lowest in monsoon. The source profiling of PM10 components, using statistical correlation, regression, and principal component analysis (PCA), revealed solid-fuel biomass, soil dust, and brick kilns and transported materials as major sources.

Chemical Characterization and Source Apportionment of PM10 Using Receptor Models over the Himalayan Region of India

This study presents the source apportionment of coarse-mode particulate matter (PM10) extracted by 3 receptor models (PCA/APCS, UNMIX, and PMF) at semi-urban sites of the Indian Himalayan region (IHR) during August 2018–December 2019. In this study, water-soluble inorganic ionic species (WSIIS), water-soluble organic carbon (WSOC), carbon fractions (organic carbon (OC) and elemental carbon (EC)), and trace elements of PM10 were analyzed over the IHR. Nainital (62 ± 39 µg m−3) had the highest annual average mass concentration of PM10 (average ± standard deviation at 1 σ), followed by Mohal Kullu (58 ± 32 µg m−3) and Darjeeling (54 ± 18 µg m−3). The annual total ∑WSIIS concentration order was as follows: Darjeeling (14.02 ± 10.01 µg m−3) > Mohal-Kullu (13.75 ± 10.21 µg m−3) > Nainital (10.20 ± 6.30 µg m−3), contributing to 15–30% of the PM10 mass. The dominant secondary ions (NH4+, SO42−, and NO3−) suggest that the study sites were strongly influenced by anthropogenic sources from regional and long-range transport. Principal component analysis (PCA) with an absolute principal component score (APCS), UNMIX, and Positive Matrix Factorization (PMF) were used for source identification of PM10 at the study sites of the IHR. All three models showed relatively similar results of source profiles for all study sites except their source number and percentage contribution. Overall, soil dust (SD), secondary aerosols (SAs), combustion (biomass burning (BB) + fossil fuel combustion (FFC): BB+FFC), and vehicular emissions (VEs) are the major sources of PM10 identified by these models at all study sites. Air mass backward trajectories illustrated that PM10, mainly attributed to dust-related aerosols, was transported from the Thar Desert, Indo-Gangetic Plain (IGP), and northwestern region of India (i.e., Punjab and Haryana) and Afghanistan to the IHR. Transported agricultural or residual burning plumes from the IGP and nearby areas significantly contribute to the concentration of carbonaceous aerosols (CAs) at study sites.

Pollution levels and health risk assessment of potentially toxic metals of size-segregated particulate matter in rural residential areas of high lung cancer incidence in Fuyuan, China.

The highest incidence and mortality rate of lung cancer in rural area of Fuyuan has been a research hotspot, and the pathogenesis is still unclear. Therefore, atmospheric particulate matters (APMs) samples were collected between 18 February and 01 March 2017, exploring water-soluble potentially toxic metals (WSPTMs) and water-soluble inorganic ionic species (WSIIs) levels, size distribution, sources, acidity and alkalinity, and potential carcinogenic and non-carcinogenic risks, hoping to provide scientific basic data to solve this problem.In our study, the average ratio of nitrate ion (NO3-)/sulfate ion (SO42-) within PM1.1, PM1.1-2.0, PM2.0-3.3, PM3.3-7.0, and PM>7.0 were 0.22, 0.18, 0.15, 0.34 and 0.36, respectively, that revealed that combustion sources contributed to PM were more significant. The anions in equilibrium (ANE) / cations in equilibrium (CAE) < 1 for all samples within PM1.1, PM2.0-3.3, PM3.3-7.0 indicate that the APMs were alkaline, but PM1.1-2.0 particulate matter shows weak acidity. SO42-prefers to combine with NH4+to form (NH4)2SO4, which hinders the formation ofNH4NO3, the remainingSO42-and NO3- to neutralize the K+,KNO3was formed at all particulate, however, K2SO4 can only be formed in PM<3.3. Arsenic (As) and Selenium (Se) were identified as the most enriched WSPTMs in all PM sizes, predominantly from anthropogenic emissions, were suggested that coal combustion is a significant source of PM-bound WSPTMs. Total WSPTMs exhibited high total carcinogenic risks (TCR) values (9.98 × 10-6, 1.06 × 10-5, and 1.19 × 10-5 for girls, boys and adults, respectively) in the smaller particles (< 1.1μm). Se was considered as the major contributor (63.60%) to carcinogenic risk (CR) in PM2.0 and had an inverse relationship with PM size that should be of prime concern.

Long-Term (2013–2018) Relationship of Water-Soluble Inorganic Ionic Species of PM2.5 with Ammonia and Other Trace Gases in Delhi, India

Long-Term (2013–2018) Relationship of Water-Soluble Inorganic Ionic Species of PM2.5 with Ammonia and Other Trace Gases in Delhi, India

Shipborne Observations of Chemical Characterization and Light Extinction of Aerosol Along the Yangtze River, China

The study of air quality over the Yangtze River is important for the pollution of urban agglomeration along the longest river in China. A comprehensive 15-day shipborne observation was conducted in the Yangtze River of the Jiangsu section in the summer of 2019. Through online observation and offline chemistry analysis of aerosol and gaseous pollutants, the result showed that the air pollution over the Yangtze River was more severe than that in surrounding cities. Sulfate, nitrate, and ammonium (SNA) dominated the water-soluble inorganic species and accounted for 35.0% ± 7.3% of the fine particle concentration (PM2.5) along the Yangtze River. The high concentration of sulfate in the droplet mode (0.56–1.0 μm) was due to the formation of sulfate through in-cloud processes under high sulfur dioxide (SO2) concentration by ship emission and high relative humidity along the river. The strong correlation between the measured mass absorption efficiency value by carbon analyzer and that simulated based on the assumption of core–shell suggested that the core–shell mode was the main composition form of aerosol in the Yangtze River. The scattering effect was the main part of the aerosol light extinction, and the scattering coefficient of 0.4- to 1.1-μm particles accounted for 85.0% of the total extinction coefficient. Positive matrix factorization model was applied for the source apportionment of particle size segment of main extinction contribution (0.4–2.1 μm), and the result showed that secondary nitrate, ship emission, coal combustion, fugitive dust, and biomass burning were the main sources of aerosols in the Yangtze River. After source reanalysis, the result indicated that the contribution of secondary nitrate from nitrogen oxide (NOx) by ship emission and coal combustion should not be ignored.

Temporal variations in the chemical composition of aerosols over the coastal Bay of Bengal

Variations in source, ionic composition and carbonaceous components of aerosols are expected in the atmosphere due to reversing the direction of winds from winter to summer over the coastal Bay of Bengal (BoB). To examine this monthly, samples were collected at the weekly interval between March 2016 and February 2017 in the coastal BoB. The air mass back trajectories suggested that the study region received aerosols from Indo-Gangetic Plain from October to February whereas from central India during June to September and south or southwest during March to May. A higher concentration of total suspended particulate matter (TSP) was observed from November to February (winter) compared to other months. The concentration of sulphate contributed more than half of water-soluble inorganic species followed by sodium, ammonium and nitrate. The dominant contribution of anthropogenic SO42− (>90%) to total SO42− was observed. The ambient elemental carbon loadings and organic carbon to EC ratios indicate the dominant contribution of biomass burning emissions in the study region. The significant contribution of non-sea salt sulphate and nss-K+ indicates a dominant contribution from the continental sources throughout the year. The mass ratio of NO3−/anthropogenic SO42− suggests stationary sources (i.e., coal burning in power plants) contribute significantly over vehicular emissions during the entire study period. The mass balance of ionic composition suggests the acidic nature of aerosols. The estimated secondary aerosols accounted for ∼50% of organic carbon and 7% of TSP in the study region. This study has implications for understanding the source, composition and nature of aerosols and possible impacts on coastal water upon its deposition.

Gridded distribution of total suspended particulate matter (TSP) and their chemical characterization over Delhi during winter.

In the present study, total suspended particulate matter (TSP) samples were collected at 47 different sites (47 grids of 5 × 5 km2 area) of Delhi during winter (January-February 2019) in campaign mode. To understand the spatial variation of sources, TSP samples were analyzed for chemical compositions including carbonaceous species [organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon (WSOC)], water-soluble total nitrogen (WSTN), water-soluble inorganic nitrogen (WSIN), polycyclic aromatic hydrocarbons (16 PAHs), water-soluble inorganic species (WSIS) (F-, Cl-, SO42-, NO2-, NO3-, PO43-, NH4+, Ca2+, Mg2+, Na+, and K+), and major and minor trace elements (B, Na, Mg, Al, P, S, Cl, K, Ca, Ti, Fe, Zn, Cr, Mn, Cu, As, Pd, F, and Ag). During the campaign, the maximum concentration of several components of TSP (996 μg/m3) was recorded at the Rana Pratap Bagh area, representing a pollution hotspot of Delhi. The maximum concentrations of PAHs were recorded at Udhyog Nagar, a region close to heavily loaded diesel vehicles, small rubber factories, and waste burning areas. Higher content of Cl- and Cl-/Na+ ratio (>1.7) suggests the presence of nonmarine anthropogenic sources of Cl- over Delhi. Minimum concentrations of OC, EC, WSOC, PAHs, and WSIS in TSP were observed at Kalkaji, representing the least polluted area in Delhi. Enrichment factor <5.0 at several locations and a significant correlation of Al with Mg, Fe, Ti, and Ca and C/N ratio indicated the abundance of mineral/crustal dust in TSP over Delhi. Principal component analysis (PCA) was also performed for the source apportionment of TSP, and extracted soil dust was found to be the major contributor to TSP, followed by biomass burning, open waste burning, secondary aerosol, and vehicular emissions.

Characterization and source analysis of water-soluble inorganic ionic species in PM2.5 during a wintertime particle pollution episode in Nanjing, China

Water-soluble inorganic ions (WSIIs) are major components of PM2.5, and play a prominent role in atmospheric acidification. In January 2019, a large-scale persistent particle pollution episode occurred in the Yangtze River Delta (YRD) region of China. High time resolution on-line monitoring of WSIIs in PM2.5 were conducted at the Atmospheric Environment Vertical Observation Station of Nanjing University by using In-situ Gas and Aerosol Compositions Monitor. From January 1 to 13, the mean concentration of WSIIs was 76.7 ± 48.2 μg·m−3. WSIIs accounted for 64.2% of PM2.5 concentration. Sulfate, nitrate and ammonium (SNA) were the major components of WSIIs, and accounted for 25.5%, 45.6% and 26.3%, respectively. The values of NO3−/SO42− increased from 1.37 to 2.86, indicating that the contribution of mobile sources to fine particle pollution was significantly enhanced than that of stationary sources. The main factors affecting the values of sulfur oxidation ratio (SOR) and nitrogen oxidation ratio (NOR) were gaseous precursor concentrations, relative humidity and air temperature. The values of SOR and NOR exceeded 0.1, implying the secondary transformation processes played critical roles during this pollution episode. To investigate the potential source areas of WSIIs in PM2.5, the Principal Component Analysis - Multiple Linear Regression (PCA-MLR) analysis and the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model were used. By using PCA-MLR, it was found that the main pollution sources in Nanjing were secondary transformation (58%), manmade dust (26%) and biomass combustion (16%). Based on the backward trajectory calculation, the potential source contribution function (PSCF) analysis and the concentration weighted trajectory (CWT) analysis, it was revealed that the air pollutants mainly came from the local sources in and around Nanjing. With the aggravation of pollution, the contribution of regional transport to PM2.5 concentrations decreased and the contribution of local emissions increased. Among the main components of WSIIs in Nanjing, NH4+ was mainly caused by agricultural activities, and generally came from Jiangsu, eastern Henan, southern Shandong, and northeastern Anhui. SO42− was mainly derived from coal burning in the nearby industrial areas or from the north through the long-distance transmission. NO3− mainly concentrated in the local areas, which was greatly affected by human activities. The weighted concentration weighted trajectory (WCWT) peak values of NH4+ and SO42− were about 10 μg·m−3, while that of NO3− was more than 20 μg·m−3, which further indicated that the local emission of NO3− was the main potential source. The findings can contribute to understand the behavior of WSIIs and their roles in the wintertime haze event, reveal potential source areas for the corresponding components, and enlighten beneficial suggestions for particle pollution prevention and control in high polluted areas.

Concentrations and size-distributions of water-soluble inorganic and organic species on aerosols over the Arctic Ocean observed during the US GEOTRACES Western Arctic Cruise GN01

Marine aerosols affect the climate directly and indirectly as well as serving as tracers of biogenic processes. Here we present the results from size-segregated and bulk aerosol samples collected from 2nd August to 10th October 2015 during the US GEOTRACES Arctic Ocean (GN01) expedition. Samples were analyzed for concentrations of major water-soluble organic and inorganic species, including acetate, formate, methanesulfonate (MSA), oxalate, propionate, chloride, nitrate, sulfate and major cations (Na+, K+, Mg2+, Ca2+, NH4+). Back-trajectory analysis was performed to categorize the wind patterns into three types; type 1, originating from the North Pacific and the Bering Sea, type–2, consisting entirely of marine Arctic air, and type 3, consisting of marine Arctic air mixed with air masses from the surrounding continents. Sea-salt was the major aerosol component, dominating in the coarse mode, 1.8–5.6 μm. Non-sea-salt sulfate and MSA were predominantly present in the fine mode, 0.18–0.32 μm, and MSA was associated with type 1 and type 2 air masses. The results from this study provide useful information on the origins and chemical processes involving these aerosol species over the Arctic in summer and help elucidate the significance of natural sources as contributors for the formation of cloud condensation nuclei.

Investigating Day and Nighttime Variability of Major Water-Soluble Inorganic Species and Role of Reactive Nitrogen Species in PM2.5 and PM10 - A Two Year Study

The study reports day and nighttime temporal variation of prominent water-soluble inorganic species (WSIS) of fine and coarse mode particulate matter at a site in central Delhi for 2012 and 2013. The two years’ concentrations of major ionic species (NH4+, K+, Ca2+ and Mg2+ and NO3-, SO42-) showed that mean levels of both ∑cations and ∑anions were higher in nighttime than daytime in both PM2.5 and PM10. Moreover, the difference of mean levels in daytime and nighttime was noticed higher in PM2.5 compared to PM10. Among anions, more variation was observed for NO3-, i.e., ~49% higher level in nighttime compared to daytime, while~9% higher values in the nighttime for SO42-. Higher variation of NO3- level might be due to active participation of NOx in daytime photo-oxidation process. Among cations,Ca2+ and Mg2+ showed higher concentration in daytime compared to nighttime. Higher day and nighttime variation of Ca2+ and Mg2+ in coarse particulate matter suggested their dominance in PM10 compared to PM2.5. In PM10, the highest Ca2+ concentration was observed in daytime summer and least in nighttime monsoon, indicating the role of loose soil and meteorological conditions. The higher daytime SO42- concentration in monsoon compared to summer show edits significant formation as secondary aerosols in fine mode. The reactive nitrogen species NO3- and NH4+ were correlated during the day and nighttime in PM2.5 and PM10.Moreover, NH4+ was highly correlated to SO42- and NO3-, mainly in the form of (NH4)2SO4 and NH4NO3.

2019년 11월 측정 광주광역시 대기 중 수용성 유 . 무기 입자의 크기분포 특성

2019년 11월 측정 광주광역시 대기 중 수용성 유 . 무기 입자의 크기분포 특성

How secondary inorganic aerosols from Delhi influence aerosol optical and radiative properties at a downwind sub-urban site over Indo-Gangetic Basin?

The particulate matters less than 10 μm sizes (PM10) were measured at a highly polluted urban environment of Delhi, and simultaneously at a downwind semi-urban site, Gual Pahari, in the north-west Indo-Gangetic Basin (IGB). The measurements were conducted during January–December 2008 to compare and contrast aerosol emissions, compositions and related optical and radiative properties for two different environments. While the total PM10 was about 30% lower at Gual Pahari as compared to Delhi, the total mass of water-soluble inorganic species (WSIs) was significantly enhanced (~23%) at Gual Pahari. Amongst WSIs, the major secondary inorganic species (SIs) were about 52% higher at Gual Pahari as compared to Delhi, with elevated levels in the post-monsoon/winter seasons. In contrast, the major crustal species were about 76% higher at Delhi as compared to Gual Pahari, with elevated levels in the summer/monsoon seasons. This indicates a strong inter-seasonal spatial variability in aerosol sources and compositions at these sites. Further, the simulations using aerosol optical model had resulted mean absorption coefficient (babs) and single scattering albedo (SSA) higher by about 50% and lower by about 18%, respectively, at Delhi (babs, 147 ± 63 M m−1 and SSA, 0.65 ± 0.12) as compared to Gual Pahari (babs, 73 ± 26 M m−1 and SSA, 0.79 ± 0.07). This reveals relative abundance of absorbing particles at Delhi compared to Gual Pahari. As a result, the estimated mean atmospheric forcing was 91 ± 23 W m−2 at Delhi, which was ~55% higher as compared to Gual Pahari. This is further corroborated with observed higher heating rate at Delhi (2.5 ± 0.7 K day−1) as compared to Gual Pahari (1.1 ± 0.4 K day−1). Our results highlight that diverse near-surface emissions together with atmospheric processing leads to strong inter-seasonal spatial heterogeneity in aerosol chemical, optical and radiative properties between the adjacent distinct sites. This has an important implication for a city-scale air pollution modeling.

Distributions of water-soluble ions in size-aggregated aerosols over the Southern Ocean and coastal Antarctica.

To investigate mass size distributions of water-soluble ions in aerosols in the marine boundary layer (MBL) over the Southern Ocean, size-segregated (0.056-18 μm in aerodynamic diameter) aerosols were collected on the 28th Chinese National Antarctic Research Expedition (CHINARE) cruise from November 2011 to March 2012. Major water-soluble inorganic and organic species in aerosols were analyzed by ion chromatography (IC). Results showed that high loadings of aerosol mass were observed over the western sector of the Southern Ocean, attributed to the high mass loadings of Na+ and Cl- in the particles >1.0 μm in diameter and high mass loadings of non-sea-salt (nss) SO42- and methanesulfonate (MSA) in the particles <1.0 μm in diameter. Nss-SO42- and MSA accounted for ∼40% of the total mass in aerosols with particle size <0.56 μm over the eastern sector of the Southern Ocean, while it was elevated to more than 60% over the western sector of the Southern Ocean that could be linked with high marine productivity reflected by high chlorophyll-a occurrence in surface waters in that region. MSA/nss-SO42- ratios showed an increasing trend as latitude increased in the southern hemisphere with a dramatic increase south of 60 °S and the variation of MSA may shape the spatial distribution of the ratios. High MSA concentration and MSA/nss-SO42- ratios were observed in west Antarctica, especially in the supermicron particles. A bimodal mass size distribution of total Ca2+ with a small peak in the 0.18-0.32 μm size range was observed, suggesting different sea spray aerosol (SSA) production mechanisms. Nss-SO42-, MSA was mainly enriched in the particle size range of 0.18 μm to 0.56 μm. The concentrations of formate and oxalate were low and detected only in certain size particles, mainly in the range <0.56-1.8 μm. Further studies should be conducted over the remote Southern Ocean to reveal marine ecosystem-aerosol-climate interactions.

Chemical characterization of wintertime aerosols over the Arabian Sea: Impact of marine sources and long-range transport

Abstract We examined here the compositional characteristics of total suspended particulate (TSP) samples collected along the east coast of the Arabian Sea during a winter cruise (SS379: 6–24 December 2018) to understand the extent of influence of air pollutants from terrestrial sources. The TSP samples (N = 17) were analyzed for water-soluble inorganic species (WSIS), elemental carbon (EC), organic carbon (OC) and water-soluble organic carbon (WSOC). Backward air mass trajectories and satellite-based fire counts revealed an influence of long-range transport of biomass burning emissions in the Indo-Gangetic Plain and southern India. Anthropogenic (82–97%) SO42− is the most abundant WSIS followed by Na+ and/or NH4+. Ambient EC loadings (0.5–2.4 μg m−3) and OC/EC ratios (2.5–10.5) are higher than usually expected for fossil-fuel combustion sources. Low mass ratios of NO3−/non-sea-salt SO42− (0.08–0.49), as well as high ratios of nss-K+/EC (0.14–1.18) and WSOC/OC (0.30–0.74), highlight the significance of coal combustion and biomass burning emissions in the regional influx of air pollutants to the Arabian Sea. The multiple linear regression analysis has indicated strong correlations among sea salt components (Na+, Cl− and Mg2+), carbonaceous components (OC, EC and WSOC), and anthropogenic WSIS (NH4+ and SO42−). Furthermore, we used minimum R-squared technique based primary OC/EC ratio in the EC-tracer method to estimate the contribution of secondary organic carbon (SOC) to OC (7–61%) and TSP mass (0.7–11%). Overall, the composition of TSP is characterized by 21 ± 10% of particulate organic matter, 2.3 ± 1.1% of EC, 21 ± 9% of anthropogenic WSIS and 43 ± 15% of unidentified fraction including dust. This study has implications for understanding the evolving nature of secondary inorganic and organic aerosols in the continental outflows.

Chemical Composition and Light Absorption of PM2.5 Observed at Two Sites near a Busy Road during Summer and Winter

To examine the difference in the major chemical composition of fine particulate matter (PM2.5) between two roadway sites, 24 h integrated PM2.5 samples were simultaneously collected both 15 m (Buk-Ku District Office (BKO) site) and 150 m (Chonnam National University campus (CNU) site) away from busy roads during the summer and winter periods; these samples were taken to determine the concentrations of organic and elemental carbon (OC and EC), water-soluble organic carbon (WSOC), and water-soluble inorganic species. In addition, the real-time aerosol light absorption coefficients (Abs) were measured using a dual-spot seven-wavelength aethalometer at the CNU site to evaluate the influence of traffic and biomass burning (BB) emissions on the concentrations of organic aerosol particles. The hourly NO2 concentration was also observed at an air pollution monitoring network that is about 2 km away from the CNU site. During summer, 24 h PM2.5 concentrations (PM2.5 episode) which exceeded the Korean PM2.5 standard (35 μg/m3) were linked to increases in organic matter (OM) and SO42− concentrations that accounted for on average 35–41% and 26–30%, respectively, of the PM2.5 at the two sites. The increased SO42− concentration was most likely attributable to the inflow of long-range transported aerosols, rather than local production, as demonstrated by both the MODIS (Moderate Resolution Imaging Spectroradiometer) images and transport pathways of air masses reaching the sites. On the other hand, the OM, WSOC, and EC concentrations were directly attributable to traffic emissions at the sampling sites, as supported by the tight correlation between the OC and EC. A small difference between the absorption Ångström exponent (AAE) values calculated at wavelengths of 370–950 nm (AAE370–950nm) and 370–520 nm (AAE370–520nm), and the poor correlation of absorption coefficient by brown carbon (BrC) at 370 nm (AbsBrC370nm) with K+ (R2 = 0.00) also suggest a significant contribution of traffic emissions to OM. However, the wintertime PM2.5 episode was strongly related to the enhanced OM and NO3− concentrations, which contributed 26–28% and 22–23% of the PM2.5 concentration, respectively. It is interesting to note that there were two distinct OC/EC ratios in winter: a lower OC/EC (~3.0), which indicates a significant contribution of traffic emissions to the OC and EC, and a higher OC/EC (~6.5), which suggests an additional influence of BB emissions as well as traffic emissions at the sites. Strong correlations between the OC and EC (R2 = 0.72–0.83) and the enhanced AAE370–520nm values compared to the AAE370–950nm support that BB emissions were also an important contributor to the wintertime OM concentrations as well as traffic emissions at the two sites. A good correlation between the gaseous NO2 and NO3− and meteorological conditions (e.g., low wind speed and high relative humidity) suggest that the heterogeneous oxidation of NO2 on moist particles could be an important contributor to wintertime particulate NO3− formation at the sites. The OC concentrations during summer and winter were higher at the BKO site, with a higher traffic flow and a shorter distance from the roadway than at the CNU site. However, there were slight differences in the concentrations of secondary inorganic species (NO3−, SO42−, and NH4+) between the sites during summer and winter.

Importance of gas-particle partitioning of ammonia in haze formation in the rural agricultural environment

Abstract. Ammonia in the atmosphere is essential for the formation of fine particles that impact air quality and climate. Despite extensive prior research to disentangle the relationship between ammonia and haze pollution, the role of ammonia in haze formation in high ammonia-emitting regions is still not well understood. Aiming to better understand secondary inorganic aerosol (sulfate, nitrate, ammonium – SNA) formation mechanisms under high-ammonia conditions, 1-year hourly measurement of water-soluble inorganic species (gas and particle) was conducted at a rural supersite in Shanghai. Exceedingly high levels of agricultural ammonia, constantly around 30 µg m−3, were observed. We find that gas-particle partitioning of ammonia (ε(NH4+)), as opposed to ammonia concentrations, plays a critical role in SNA formation during the haze period. From an assessment of the effects of various parameters, including temperature (T), aerosol water content (AWC), aerosol pH, and activity coefficient, it seems that AWC plays predominant regulating roles for ε(NH4+). We propose a self-amplifying feedback mechanism associated with ε(NH4+) for the formation of SNA, which is consistent with diurnal variations in ε(NH4+), AWC, and SNA. Our results imply that a reduction in ammonia emissions alone may not reduce SNA effectively, at least at rural agricultural sites in China.

Air quality of an urban school in São Paulo city.

A major campaign was carried out in indoor and outdoor environments in a school located in the university campus of the city of São Paulo. Elements, PAH, oxy-PAH, water-soluble ions and black carbon were determined and compared with preliminary campaigns. The results indicated that the concentrations of particles and organic compounds were higher indoors. Some high molecular weight compounds, attributed to vehicular emissions, were more abundant outdoors. The associated health risk was found to be low. 2-Methylanthraquinone and benzo(a)anthracene-7,12-dione were detected in the indoor samples, denoting the infiltration of vehicle exhaust. The observation of black carbon also corroborates the contribution of traffic emissions. For most of the elements, except for chromium, iron and manganese, the concentrations obtained in indoors were higher than outdoors, mainly due to soil resuspension. Chromium and manganese likely derived from emissions of the vehicle powered by mixtures of ethanol and gasoline. Water-soluble inorganic ions species denoted the influence of soil resuspension and human activities.

Seasonal variations and source apportionment of water-soluble inorganic ions in PM2.5 in Nanjing, a megacity in southeastern China

Daily PM2.5 samples were collected in Nanjing, a megacity in southeastern China, for a period of one-half of a month during every season from 2014~2015. Mass concentrations of nine water soluble inorganic ions (F−, Cl−, SO42−, NO3−, Na+, NH4+, K+, Mg2+ and Ca2+) were determined using ion chromatography to identify the chemical characteristics and potential sources of PM2.5. The mass concentrations of daily PM2.5 ranged from 31.0 to 242.9 μg m−3, with an annual average and standard deviation of 94.4 ± 31.1 μg m−3. The highest seasonal average of PM2.5 concentrations was observed during winter (108.5 ± 31.8 μg m−3), and the lowest average was observed during summer (85.0 ± 22.6 μg m−3). The annual average concentration of total water soluble inorganic ions was 39.82 μg m−3, accounting for 44.4% of the PM2.5. The seasonal variation in water soluble inorganic ions in PM2.5 reached its maximum during autumn and reached its minimum during spring. Sulfate, nitrate and ammonium were the dominant water soluble inorganic species, with their combined proportion of 82.0% of the total water soluble inorganic ions and 36.8% of the fine particles. Seasonal variations in aerosol acidity and chemical forms of secondary inorganic ions were discussed. The average ratio of NO3−/SO42− was 0.95. According to the results of principal component analysis, secondary sources, burning processes, and airborne dust were the dominant potential sources of PM2.5 in Nanjing.

Size-fractionated water-soluble ions during autumn and winter: Insights into volatile ammonium formation mechanisms in Shanghai, a megacity of China

Abstract Size-fractionated aerosols were collected by a Micro-Orifice Uniform Deposit Impactor at an urban site in Shanghai during the autumn and winter of 2014. The results showed that the average concentration of PM1.8 increased from 49 μg m−3 in autumn to 74 μg m−3 in winter. By contrast, the relative contribution of the water-soluble inorganic species decreased from 40% in autumn to 31% in winter. This finding suggests that the increase of organic matter (OM) greatly contributed to the deterioration of particle pollution in winter. Compared to autumn, the concentration of sulfate decreased whereas the concentration of NH4Cl increased significantly and became an important constituent of the fine particles in winter. The formation of nitrate in autumn became significant at [NH4+]/[SO42−] > 2, indicating that H2SO4 was fully neutralized by NH3 to form (NH4)2SO4. Our results showed that the regression between [NO3−]/[SO42−] and [NH4+]/[SO42−] drawn an unrealistic nitrate formation mechanism when the particulate NH4Cl was abundant. Replacing [NO3−] with {[NO3−]+[Cl−]} in the regression between [NO3−]/[SO42−] and [NH4+]/[SO42−], it is established that (NH4)2SO4 is preferentially formed before the excess available NH3 can react with HNO3 and HCl to form NH4NO3 and NH4Cl during wintertime. The concentrations of particulate sulfate and nitrate were not positively correlated with the ambient relative humidity, indicating that heterogeneous reactions on wet particles were not the key to haze formation in Shanghai during winter. Our results suggest that more studies are needed to understand the complex haze formation mechanisms in China.

Study of temporal variability and mass closure of PM2.5 and its chemical constituents during weak south-west monsoon

Ambient PM2.5 (n = 42) samples have been collected during a weak South-west (SW) monsoon (July‒September, 2015) from central part of the Indo-Gangetic Plain (IGP; at Kanpur). Organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), water-soluble inorganic species (WSIS) and metals have been measured in this study. Air-mass back trajectory (AMBT) analysis reveals atmospheric transport from three major pathways indicated as Type-1 (n = 24; traversing through western region), Type-2 (n = 8; traversing eastern region) and Type-3 (n = 10; terrestrial air-masses). Total carbonaceous aerosols (TCA), mineral dust (MD) and WSIS in Type-1 air-mass contributed 18.7 ± 8%, 40.3 ± 14.5% and 35.2 ± 13.4%, respectively to the PM2.5 mass. TCA, MD and WSIS mass fractions constituted 27.1 ± 13.2%, 29.1 ± 7.9% and 34.9 ± 10.7% in Type-2 air-mass and 25.2 ± 14.1%, 34.6 ± 14% and 33.3 ± 9.8% in Type-3 air-mass, respectively. Mineral dust percentage fraction and composition (based on Fe/Al ratio) suggests significant differences between Type-1 and Type-2 air-masses. Based on statistical two-tailed t-test, the mineral dust composition of Type-1 versus Type-3 and Type-2 versus Type-3 air-masses look near similar. However, average mass ratios of OC/EC (6.2–6.4), WSOC/OC (≈0.50; exception being difference in Type-2 versus Type-3) and K+BB/OC (0.05–0.07; K+BB: biomass burning derived potassium) look near similar in PM2.5 associated with all the three air-masses; indicating carbonaceous aerosols from well-mixed sources with dominant contribution from biomass burning emission. A significant abundance of organic aerosols and mineral dust in presence of high moisture content and their mixing over IGP has implications to perturbation in regional scale radiative forcing.