Concentrations Of Water-soluble Ions Research Articles

Conversion Characteristics of Combustible Particles from Coal-fired Flue Gas in WFGD and WESP

Monitoring of condensable particulate matter (CPM) emitted from stationary pollution sources has often been neglected. To reduce the emission of CPM, it is necessary to study its transformation rules in flue-gas cleaning devices. The results show that the wet flue gas desulfurization (WFGD) and wet electrostatic precipitator (WESP) have a good synergistic effect on the removal of CPM. The concentration of CPM in flue gas is higher than that of filterable particulate matter, but the concentration of total particulate matter (sum of the condensable particulate matter and filterable particulate matter) reaches ultra-low emission requirements. The organic mass concentration of CPM in the WFGD inlet and outlet is larger than that of inorganic components, which is equalized during the treatment of WESP. Based on measurements of the components and concentrations of water-soluble ions in the inorganic part of the CPM, PM0.3 can be joined during the CPM trapping process and an acid mist is generated during the condensable particulate matter formation. The acid mist is strengthened through the treatment of WFGD and WESP. The experiment results also show that SO42- is the main component of water-soluble ions in the inorganic part of CPM.

Analysis of Pollution Characteristics and Sources of PM2.5 Chemical Components in Chengdu in Winter

Day-night PM2.5 samples were continuously collected in Chengdu from January 1 to 20, 2017, and the concentrations of major chemical components (water-soluble ions and carbonaceous components) were measured in the laboratory. During the observation period, the average mass concentration of PM2.5 was (127.1±59.9) μg·m-3. The mass concentration of water-soluble ions was (56.5±25.7) μg·m-3 and SO42-, NO3-, and NH4+ were the most dominant ions with a concentration of (13.6±5.5), (21.4±12.0), and (13.3±5.7) μg·m-3, respectively, accounting for 85.6% of the water-soluble ions. The average mass concentrations of organic carbon (OC) and elemental carbon (EC) were 34.0 and 6.1 μg·m-3, respectively, accounting for 26.8% and 4.8% of the PM2.5 mass concentration, respectively. The comparison of the average day-night concentration shows that the daytime and nighttime mass concentrations of PM2.5 are (120.4±56.4) and (133.8±64.0) μg·m-3, respectively, and that the nighttime pollution is more serious. The SO42-, NO3-, and NH4+ concentrations are higher during the day than at night, which is related to daytime light, which promotes the formation of secondary ions. The Cl-, K+, OC, and EC concentrations increase significantly, which may be affected by increased emissions from coal and material combustion. Based on the literature review and comparison of the winter chemical composition of PM2.5 in Chengdu in recent years, the SO42- concentration significantly decreases from 50.6 μg·m-3 in 2010 to 13.6 μg·m-3 in 2017. The NO3- concentration changes little; it is maintained at~20 μg·m-3. The analysis of the acid-alkali ion balance shows that PM2.5 in Chengdu is alkaline due to the relative overgrowth of NH4+, which is different from previous partially acidic results. The average value of NO3-/SO42- is 1.57. Mobile sources have a greater impact on the PM2.5 pollution in Chengdu in winter. The correlation coefficients of OC and EC between daytime and nighttime are 0.82 and 0.90, respectively (P<0.01), which indicates that the OC and EC sources are consistent. The SOC estimation shows that the SOC concentrations during the day and night are 8.5 μg·m-3 and 11.9 μg·m-3, respectively, accounting for 28.1% and 30.8% of the OC, respectively. The K+/EC average value is 0.31 and the correlation coefficient between K+ and OC is 0.87 (P<0.01), indicating that biomass combustion has a certain influence on the carbonaceous aerosol in Chengdu in winter. The principal component analysis shows that the winter PM2.5 in Chengdu mainly originates from combustion sources (coal burning, biomass burning, etc.), secondary inorganic sources, and soil and dust sources. The contribution rates are 32.8%, 34.5%, and 21.5%, respectively.

Temporal distribution and source apportionment of PM2.5 chemical composition in Xinjiang, NW-China

Daily fine particulate matter samples were collected in Dushanzi district within four months from September 2015 to August 2016 and represent the four seasons. The samples were determined for major chemical components in PM2.5, including elements, water-soluble ions (WSIs) and the organic/elemental carbon (OC/EC). The results indicated that the annual mean PM2.5 concentration was 62.85 ± 43.5 μg m−3 in the Dushanzi district, with the highest seasonal average in winter (95.47 ± 61.7 μg m−3) and the lowest in summer (33.22 ± 17.7 μg m−3). The crustal elements were the most abundant elements and accounted for 96.51% of the total analyzed elements. Carcinogenic metals, such as Cr, Pb, As and Cd, originated from human activity, especially during winter. The highest total WSI concentration was 68.99 μg m−3 in winter, followed by autumn (16.32 μg m−3), spring (10.23 μg m−3) and summer (7.06 μg m−3). SO42−, NO3− and NH4+ were the most abundant WSIs in Dushanzi. Ion balance calculations showed that PM2.5 in winter was acidic; in autumn and spring alkaline; and in summer nearly neutral. Total carbonaceous aerosol (TCA) accounted for 34% of the PM2.5. The chemical mass closure (CMC) indicated that minerals and WSIs were the major fraction, accounting for 33.58% and 23.17% of PM2.5 mass concentration, respectively. Dushanzi was controlled by four major air masses, and the relative contributions of these air masses differ by season. Positive matrix factorization (PMF) analysis identified six sources including vehicle emission, biomass burning, coal combustion, industrial pollution, secondary aerosols and soil dust, with annual mean contributions of 9.43%, 10.86%, 18.45%, 12.15%, 18.26% and 30.85%, respectively. Moreover, the relative contributions of these identified sources varied significantly with the changing seasons.

Characteristics and formation mechanisms of autumn haze pollution in Chengdu based on high time-resolved water-soluble ion analysis.

To investigate the characteristics and formation mechanisms of haze pollution in the autumn season in the Sichuan Basin, hourly concentrations of water-soluble inorganic ions in PM2.5 (Na+, K +, NH4+, Mg2+, Ca2+, Cl-, NO3-, and SO42-) and major gaseous precursors (HCl, NH3, SO2, HONO, and HNO3) were measured by a gas and aerosol collector combined with ion chromatography (GAC-IC) from September to November 2017 at an urban site in Chengdu. The average mass concentration of total water-soluble ions was 36.9 ± 29.4μgm-3, accounting for 62.8% of PM2.5 mass. Nitrate was the most abundant ion, comprising 41.2% of the total ions, followed by sulfate (27.1%) and ammonium (18.1%), indicating the important contribution of motor vehicle emissions to PM2.5 in Chengdu. Secondary formation of inorganic ions and biomass burning emissions played a vital role in the haze pollution processes. The formation of nitrate aerosol was particularly dominant and exhibited the most substantial increase during haze processes. It was likely to be produced primarily through homogeneous reactions, whereas heterogeneous reactions dominated sulfate formation. Additionally, distinct differences in diurnal patterns of secondary inorganic ions between clean days and polluted days were observed, reflecting different formation characteristics under polluted conditions. Due to a large increase of acidic aerosols, most particles collected on polluted days were acidic, and ammonium in most samples existed mainly as NH4HSO4 and NH4NO3. Furthermore, backward-trajectory cluster analysis revealed that air masses originating from the northeast of Chengdu prevailed in the autumn season, and haze pollution was dominated mainly by short-distance transport within the Sichuan Basin.

Study on pollution behavior and sulfate formation during the typical haze event in Nanjing with water soluble inorganic ions and sulfur isotopes

The typical haze event in Nanjing was selected to study pollution behavior and sulfate formation by field measurement. Based on the concentrations of water soluble inorganic ions in PM2.5, pollution characteristics of the haze were investigated with phase clustering analysis. Besides, δ34S values of SO2 and sulfate in PM2.5 were determined in order to explore sulfur sources and sulfate formation. The result showed that PM2.5 pollution during the haze event was significantly serious, which was mainly from coal combustion, vehicle exhaust emission and biomass burning. Sulfate formation was attributed to aqueous phase sulfur oxidation reactions promoted by high relative humidity and NO2 concentration under the alkaline condition. The color of sky on 22 Dec. was ascribed to the combination of sunset glow and fine particles in high-moisture atmosphere. δ34S values of SO2 are found to be lower than those of sulfate in PM2.5 indicating there was presence of sulfur isotopic fractionation during SO2 oxidation. The average contribution of SO2 homogenous oxidation to sulfate was about 51.2% during the haze events. The ratio of SO2 heterogeneous and homogeneous oxidation to sulfate was mainly attributed to the concentrations of gaseous pollutants (NO2, SO2 and O3) and relative humidity of the atmosphere.

Size Distribution Characteristics of Water-Soluble Inorganic Ions During Summer and Autumn in Zhengzhou

To study the compositional characteristics of atmospheric particulates with different particle sizes in the central city of Zhengzhou, China, a Tisch graded impact sampler was used to sample atmospheric particulates in summer and autumn. The mass concentrations of water-soluble inorganic ions, including anions (Cl-, F-, NO3-, and SO42-) and cations (Na+, Ca2+, NH4+, K+, and Mg2+) were measured by ion chromatography, and the online ion chromatography-based analyzer MARGA monitored the real-time concentration of particulate nitrate. The results showed that the average concentration of water-soluble ions in Zhengzhou City was (70.9±52.1) μg·m-3 during the sampling period, and the order of water-soluble ion mass concentrations was NO3- > SO42- > NH4+ > Ca2+ > Na+ > Cl- > Mg2+ > K+ > F-; NO3-, SO42-, and NH4+ accounted for 79.9% of total water-soluble ions. The NO3- concentration was mainly concentrated in the 0.65-3.3 μm particle size segment, despite the SO42- concentration being concentrated in the ≤ 1.1 μm particle size segment in autumn or summer. Both NO3- and SO42- had a bimodal distribution in summer and autumn and were mainly distributed as fine particles. NH4+ showed seasonal variation with a bimodal distribution in summer and a unimodal distribution in autumn. Zhengzhou City had serious ozone pollution in summer, and O3 and NO3- showed the "staggered peak" phenomenon, indicating photochemical reactions in the atmosphere. In autumn, water-soluble inorganic ion concentration in particulate matter was high, and the ratio of[NO3-]/[SO42-] was higher than 0.5. The mobile source is an important source of particles. NOR and SOR peaks were on the 1.1-2.1 μm particle size segment in summer, whereas those in the 0.65-1.1 μm particle size segment occurred in autumn. The sulfur gas-to-grain conversion in summer was larger than that of nitrogen, contrary to the result in autumn.

Day-night variability of PM10 components at a Mediterranean urban site during winter

Daytime and nighttime PM10 samples were collected during winter at an urban site in Southeastern Spain. Samples were subsequently analyzed to determine the concentrations of water-soluble ions, carbonaceous species, and metals. PM10 daytime and nighttime concentrations were 26.1 and 20.6 μg/m3, respectively. This difference may be mainly attributed to the reduction in the number of vehicles during nighttime. Traffic-related components such as EC, Ca and other crustal elements, Cu or Zn, showed statistically significantly higher concentrations during daytime, suggesting that traffic emissions were more relevant than day-to-night differences in meteorological conditions. In contrast, no significant differences between daytime and nighttime levels of secondary inorganic ions (SO42−, NO3− and NH4+) were found. Primary and secondary organic carbon concentrations were estimated using the EC tracer method. As expected, POC levels were greater during the day due to increased vehicle exhaust emissions; conversely, higher SOC concentrations were registered during the nighttime period. This was most likely the result of a significant contribution of nighttime chemistry to the formation of secondary organic aerosols.

Mass Concentrations and Size Distributions of Water-soluble Inorganic Ions in Atmospheric Aerosols in Beibei District, Chongqing

In order to study the concentration and distribution characteristics of water-soluble inorganic ions in aerosol particles of the Beibei district of Chongqing, aerosol samples were collected with an Andersen cascade impactor between March 2014 and February 2015. Water-soluble inorganic ions, including Na+, NH4+, K+, Mg2+, Ca2+, F-, Cl-, NO3-, and SO42- were determined for different particle sizes (9.00, 5.80, 4.70, 3.30, 2.10, 1.10, 0.65, and 0.43 μm) using the ion chromatography method. Results showed that SO42-, NH4+, NO3-, Cl-, Na+, and K+ were mainly distributed in fine particles, while Mg2+, Ca2+, and F- were mainly present in coarse particles. SNA (SO42-, NH4+, and NO3-) exhibited clear unimodal distribution, with peaks in the droplet mode of 0.65-1.10 μm, mainly present in the form of (NH4)2SO4 and NH4NO3 in fine particles. The formation of SO42- is mainly attributed to in-cloud processes and partly to oxidation of SO2. Na+, Cl-, and Mg2+ exhibited bimodal distribution in coarse and fine particles; K+ was a single peak distribution in the range of 0.43-1.10 μm, while peaks of F- and Ca2+ concentrations were in coarse particles. Average annual concentrations of total water-soluble ions in PM2.1 and PM9.0 were (32.68±15.28) μg·m-3and (48.01±19.66) μg·m-3 over the observation period. Seasonal variations of PM2.1 and PM9.0concentrations decreased in the order of winter > spring > summer > autumn. This was the same for most ions, but a small number of ions (F-, Mg2+ and Ca2+) had a different pattern in the spring, summer, and winter. The SNA were the major components of water-soluble ions in PM2.1, and Ca2+ was the major component of water-soluble ions in PM9.0 besides SNA. The concentration of cations was significantly higher than that of anions' in PM2.1 and PM9.0, with a certain correlation between different ions. Emissions from motor vehicle exhaust, combustion processes, soil sources, and fugitive dust were the major sources of water-soluble ions in this area. The effect of air temperature on secondary ions is significant (P<0.05), but relative humidity and wind speed have no significant effect (P>0.05).

Analysis of Compositional Variation and Source Characteristics of Water-Soluble Ions in PM2.5 during Several Winter-Haze Pollution Episodes in Shenyang, China

From 18 February to 13 March 2014 and from 17 December 2016 to 27 January 2017, an online analyzer for monitoring aerosols and gases (MARGA) and an online single particle aerosol mass spectrometer (SPAMS) were used to measure and analyze the concentrations and sources of water-soluble (WS) ions in PM10, PM2.5, and gases (NH3, HNO3, HCl), in Shenyang City, China. During the field campaign, nine haze episodes (or smog episodes, total 582 h) were identified, with 960 identified as non-haze periods. The average mass concentrations of PM2.5 and total water-soluble ions (TWSIs) in PM2.5 during haze episodes were 131 μg·m−3 and 77.2 μg·m−3, 2.3 times and 1.9 times the values in non-haze periods, respectively. The average mass concentration of TWSIs in PM2.5 was 55.9 μg·m−3 (accounting for 55.9% of PM2.5 mass loading), 37.6% of which was sulfate, 31.7% nitrate, 20.0% ammonium, 6.6% chloride, 1.9% potassium, 1.4% calcium, and 0.8% magnesium throughout the campaign. Concentrations of sulfate, nitrate, and ammonium (SNA) secondary pollution ions increased rapidly during haze episodes to as much as 2.2 times, 3.0 times, and 2.4 times higher than during non-haze periods, respectively. Diurnal variations during non-haze periods were significant, while complex pollution was insignificant. Based on changes in the backward trajectories and concentrations of WS ions, the hazy episodes were divided into three types: complex, coal-burning, and automobile exhaust pollution. All complex episodes had high concentrations and greater contributions of ammonium nitrate from complex and automobile exhaust pollution, while the contribution of ammonium sulfate from coal-burning pollution was greater than that of ammonium nitrate. The correlation coefficients among SNA species were very high in complex pollution, with nitrate and sulfate the main forms present. The results of principal component analysis (PCA) were related to emissions from burning coal for heating and from long-range transmission in winter. In the case of exhaust pollution, NO3− accounted for the highest percentage of PM2.5, and NH4+ was more closely related to NO3− than to SO42−. Coal-burning pollution was the most common type of pollution in Shenyang. The contribution of sulfate was higher than that of nitrate. Based on PCA, the contribution of coal-burning emissions varied from 36.7% to 53.6% due to industry, soil sources, and other factors.

Characteristics and Source Apportionment of Water-soluble Ions in PM2.5 During Winter in Panjin

In order to study the characteristics and source of water-soluble ions in PM2.5 in Panjin, PM2.5 samples were collected at three sites in January of 2017, and the levels of eight ions (Na+, Mg2+, Ca2+, K+, NH4+, SO42-, Cl-, and NO3-) were determined by ICS-900 ion chromatograph. The characteristics of PM2.5, the water-soluble ion concentration, SOR and NOR calculation, and ion balance calculation were investigated, and a principal component analysis was conducted. The results showed that the concentration of PM2.5 and water-soluble ions followed a descending sequence of park > development zone > the second middle school. SO42-, NO3-, and NH4+ were the major components of the water-soluble ions at the three sampling sites. SOR and NOR values were all higher than 0.10, indicating that SO42- and NO3- were mainly converted from SO2 and NOx. The ion balance calculation demonstrated that the cationic and anion equivalents in Panjin had great correlation in winter. Further study showed that the atmosphere in the development zone presented as neutral and that in the cultural park and the second middle school presented as partially alkaline. The principal component analysis further indicated that the water-soluble ions were mainly derived from fuel combustion, biomass burning, secondary particles, and re-suspended dust in winter.

Characteristics and Source Apportionment of Water-soluble Inorganic Ions in Road Dust PM2.5 During Spring in Tianjin Using the Quadrat Sampling Method

In order to collect comprehensive information regarding the characteristics and sources of the water-soluble inorganic ions in road dust (RD) PM2.5 in Tianjin, samples of road dust were collected in April 2015 in Tianjin, and then re-suspended on filters using a NK-ZXF sampler. The concentrations of the major water-soluble inorganic ions were analyzed by ion chromatography. A correlation analysis, ratio method, and principal component analysis were used to analyze the sources of RD PM2.5. The results showed that the total water-soluble inorganic ion concentration in Tianjin accounted for 6.13%±2.32%, varying with different road types. Na+, K+, Mg2+, and Ca2+ showed high homology. NO3-/SO42- revealed that the main source of PM2.5 was mostly attributed to fixed sources. The principal component analysis showed that the main sources of RD PM2.5 in Tianjin were coal combustion, mobile sources, biomass burning, and construction dust.

Halogenated flame retardants (HFRs) and water-soluble ions (WSIs) in fine particulate matter (PM2.5) in three regions of South China

Halogenated flame retardants (HFRs) and water-soluble ions (WSIs) were investigated in fine particulate matter (PM2.5) collected from an urban site, a rural e-waste recycling (e-waste) site, and a background site in South China. Generally, the WSI concentrations were highest at the e-waste site and comparable at the other sites and secondary species (SO42−, NH4+, and NO3−) were dominant components at the three sites. The compositions and seasonal variations of WSIs at the e-waste site were distinct from those in the urban and background areas suggesting significant influence of e-waste recycling on PM2.5 components. Polybrominated diphenyl ethers (PBDEs) dominated the HFRs in PM2.5 from the e-waste site, and their concentrations (median = 883 pg/m3) were significantly higher than those at the urban (375 pg/m3) and background site (52.4 pg/m3). However, novel decabromodiphenyl ethane (DBDPE) was the primary HFRs in the urban air, with noticeably elevated concentrations (median = 356 pg/m3) compared to those in the other two areas (medians = 62.3 and 5.09 pg/m3). The composition profiles of HFRs in the background air followed those in the e-waste areas, with substantial contributions of legacy chemicals. This was explained by the prevailing NE wind, which favored atmospheric transport of HFRs from the e-waste recycling area to the background area. Correlation analysis showed that most HFRs in the urban air are associated with Cl−, implying an industrial emission sources. In the e-waste area, HFRs are associated with organic and elemental carbons (OC and EC) and K+, confirming a common source of e-waste recycling. Significant correlations between HFRs and EC and Cl− in the background air suggest that their occurrence in this region was attributed to both the e-waste and urban areas.

Boundary layer structure and scavenging effect during a typical winter haze-fog episode in a core city of BTH region, China

The vertical distribution of PM2.5 and meteorological parameters from ground to upper levels were observed simultaneously using meteorological tower, tethered balloons and aerosol laser radar in Dec of 2016 in the urban area of Tianjin and its southern district, Jinghai. The influence of the vertical structure of boundary layer on a typical haze-fog episode was analyzed. There existed long distance transport of PM in the high layers before the haze formed in Tianjin and the downward airflows brought the PM from the high layer to the ground. In the early stages of this episode, periodic temperature inversions occurred, leading to conspicuous diurnal variations in the vertical profile of the PM2.5. In the middle and late stages of this episode, strong inversion and thick humidity layer were sustained below 400 m, and there were no big daily changes in the vertical profiles of the PM2.5. During the rapid formation period of the fog, the inversion layer was damaged and turbulence was strengthened. During the stationary phase of the fog process, wind and turbulence in the boundary layer became weak again. Rime was the main weather-related, wet cleaning mechanism that lowered pollutants concentration during this fog episode. High concentrations of water soluble ions in the rime samples and the concentrations of those ions in ambient PM2.5 appeared significant decrease during the rime period, which illustrated the scavenging effect of rime.

Acidity of Aerosols during Winter Heavy Haze Events in Beijing and Gucheng, China

We investigated the acidity and concentrations of water-soluble ions in PM2.5 aerosol samples collected from an urban site in Beijing and a rural site in Gucheng, Hebei Province from November 2016 to January 2017 to gain an insight into the formation of secondary inorganic species. The average SO42–, NO3–, and NH4+ concentrations were 8.3, 12.5, and 14.1 μg m–3, respectively, at the urban site and 14.0, 14.2, and 24.2 μg m–3, respectively, at the rural site. The nitrogen and sulfur oxidation ratios in urban Beijing were correlated with relative humidity (with correlation coefficient r = 0.79 and 0.67, respectively) and the aerosol loadings. Based on a parameterization model, we found that the rate constant of the heterogeneous reactions for SO2 on polluted days was about 10 times higher than that on clear days, suggesting that the heterogeneous reactions in the aerosol water played an essential role in haze events. The ISORROPIA II model was used to predict the aerosol pH, which had a mean (range) of 5.0 (4.9–5.2) and 5.3 (4.6–6.3) at the urban and rural site, respectively. Under the conditions with this predicted pH value, oxidation by dissolved NO2 and the hydrolysis of N2O5 may be the major heterogeneous reactions forming SO42– and NO3– in haze. We also analyzed the sensitivity of the aerosol pH to changes in the concentrations of SO42–, NO3–, and NH4+ under haze conditions. The aerosol pH was more sensitive to the SO42– and NH4+ concentrations with opposing trends, than to the NO3– concentrations. The sensitivity of the pH was relatively weak overall, which was attributed to the buffering effect of NH3 partitioning.

Air quality assessment of Mandi Gobindgarh city of Punjab, India

The present study assessed the air quality of an industrial town Mandi Gobindgarh, one of the critically polluted areas specified by Central pollution control board, India. Air quality was assessed in terms of Indian Air Quality Index (IND-AQI) by analyzing concentration of the air pollutants like particulate matter (PM10, PM2.5), sulfur dioxide (SO2), and nitrogen dioxide (NO2). Half-yearly wind roses were prepared from wind data from October, 2013 to March, 2015 for selecting sites on the basis of prevailing wind direction and speed. On the basis of wind roses, land use pattern and industrial clusters, 11 sampling sites were selected, i.e., 7 were industrial, 2 were residential, and 1 was agricultural. AQI was calculated for different seasons from March, 2015 to February, 2016; on the basis of IND-AQI. Results indicate that pollutant responsible for maximum sites for higher AQI was PM10 and industrial sites were having “Poor” air quality, making area more susceptible to a large number of airborne disease. Annual cycle shows highest concentration of pollutants and water soluble ions to be higher in winter season and the lower during monsoon season. The concentration of water soluble ions for samples collected during winter season at commercial site was found to vary in the order of NH4+ > Cl− > SO42− > Na+ > Ca2+ > K+ > NO3− > Mg2+. Values of SO2/NO2 obtained vary from 1.23 to 1.99 at various selected sites which depict that the impacts of vehicular sources were marginally less, when compared to industrial sources.

Spatial and temporal characteristics of PM2.5 acidity during autumn in marine and coastal area of Bohai Sea, China, based on two-site contrast

In-situ pH of atmospheric particulate, defined as the pH value of aqueous phase in ambient aerosol, has been reported to have significant influence on the formation progress of secondary aerosol, especially through the heterogeneous pathway. In this study, PM2.5 samples were collected in the marine and costal area of Bohai Sea from September 8th to October 8th in 2013, with daytime and nighttime separated. Eight water-soluble ions including SO42−, NO3−, Cl−, NH4+, K+, Ca2+, Na+ and Mg2+ were analyzed by ion chromatography. The in-situ pH of PM2.5 was estimated using Aerosol Inorganics Model II, with meteorological parameters (temperature and relative humidity) and basic chemical composition data (concentrations of water-soluble ions) serving as input. Five indicators were conjunctively applied to describe the spatial and temporal characteristics of PM2.5 acidity over Bohai Sea during autumn. As a result, strong acidity was found in both marine and coastal area. Marine area had a stronger acidity under a more NH4+-deficiency and humid condition. And the difference of PM2.5 acidity between daytime and nighttime was more obvious in coastal area than that in marine area, with stronger acidity observed during the daytime. Local SO2 emission was identified as an important factor influencing the diurnal variation of aerosol acidity. Meanwhile, sulfurous species were identified as a mixture of NH4HSO4 and H2SO4 in marine area while a mixture of NH4HSO4 and (NH4)2SO4 in the coastal area. Analysis in the impact of aerosol acidity on nitrate formation has indicated that heterogeneous pathways were important in nitrate formation in coastal area of Bohai Sea as well as the homogeneous pathways. Capsule abstractPM2.5 was highly acidic around Bohai Sea, and the acidity of PM2.5 was stronger in marine area than coastal area during autumn.

Seasonal Variation and Source Apportionment of Water-Soluble Ions in PM2.5 in Quanzhou City

In this study, the seasonal characteristics of water-soluble ions (WSIs) present in fine particulate matter (PM2.5) in Quanzhou City were investigated. PM2.5 samples were collected at five different sites in the city from March 2014 to January 2015 and the concentrations of Na+, NH4+, K+, Ca2+, Mg2+, F-, Cl-, NO3-, and SO42- were determined by ion-exchange chromatography. In order to identify the sources of these WSIs, the positive matrix factorization (PMF) analysis was applied. The seasonal variations in total WSI concentrations were found to decrease in the order of spring > winter > summer > autumn. The ions SO42-, NO3-, and NH4+ were the major WSIs found in PM2.5, accounting for 90.3%±3.3%, 68.8%±11.7%, 78.9%±7.1%, and 74.0%±18.4% of the total amount of ions found in spring, summer, autumn, and winter, respectively. These results suggested that the level of secondary ions was relatively high in the spring season. The anion-to-cation ratio in each of the four seasons was less than one, which indicated that PM2.5 in Quanzhou City was slightly alkaline. Furthermore, NH4+ ions in PM2.5 mostly existed in the form of (NH4)2SO4, NH4HSO4, and NH4NO3 during spring and winter, while they were primarily found as NH4HSO4 and NH4NO3 in the summer and autumn seasons. PMF analysis revealed that marine salt, secondary sources, fugitive dust from construction, municipal incineration, and biomass burning were the main potential sources of the ionic components of PM2.5.

Chemical composition and droplet size distribution of cloud at the summit of Mount Tai, China

Abstract. The chemical composition of 39 cloud samples and droplet size distributions in 24 cloud events were investigated at the summit of Mt. Tai from July to October 2014. Inorganic ions, organic acids, metals, HCHO, H2O2, sulfur(IV), organic carbon, and elemental carbon as well as pH and electrical conductivity were analyzed. The acidity of the cloud water significantly decreased from a reported value of pH 3.86 during 2007–2008 (Guo et al., 2012) to pH 5.87 in the present study. The concentrations of nitrate and ammonium were both increased since 2007–2008, but the overcompensation of ammonium led to an increase in the mean pH value. The microphysical properties showed that cloud droplets were smaller than 26.0 µm and most were in the range of 6.0–9.0 µm at Mt. Tai. The maximum droplet number concentration (Nd) was associated with a droplet size of 7.0 µm. High liquid water content (LWC) values could facilitate the formation of larger cloud droplets and broadened the droplet size distribution. Cloud droplets exhibited a strong interaction with atmospheric aerosols. Higher PM2. 5 levels resulted in higher concentrations of water-soluble ions and smaller sizes with increased numbers of cloud droplets. The lower pH values were likely to occur at higher PM2. 5 concentrations. Clouds were an important sink for soluble materials in the atmosphere. The dilution effect of cloud water should be considered when estimating concentrations of soluble components in the cloud phase.

Dew water chemical composition and source characterization in the IGP outflow location (coastal Bhola, Bangladesh)

Dew water samples were collected during the winter season (December, 2014 to January, 2015) at an outflow location from the Indo-Gangetic Plain (IGP) to the Bay of Bengal (Coastal Bhola, Bangladesh). Physical properties of the dew water, including pH and electrical conductivity (EC), were measured. The concentrations of water soluble ions (Cl−, SO4 2−, NO3 −, HCO3 −, Na+, K+, Ca2+, and Mg2+) and trace metals (Zn, Fe, Mn, Cu, Cr, Pd, and Ni) were also measured. Source characterization of the chemical species was done by correlation analysis, enrichment factor analysis, percent source contribution calculation, and air mass trajectory analysis. The average pH and EC of the collected dew water were 6.81 and 154.80 μS cm−1, respectively. The average concentration of SO4 2− and NO3 − was 264.10 and 222.20 μeq L−1, respectively. The concentrations of water soluble ions followed the sequence: Ca2+ > Cl−> SO4 2 > Na+ > NO3 −> Mg2+ > K+ > HCO3 −. The concentrations of trace metals ranged in order with Zn > Fe > Mn > Cu, while the concentrations of Cr, Pb, and Ni were below detection limit in dew water. Regression analysis showed significant correlations among sea, soil, and anthropogenic species. High enrichment factors of SO4 2−, NO3 −, Zn, Mn, and Cu indicates anthropogenic sources. Percent source contribution of different species showed significant anthropogenic contribution for Cl−(1.80%), SO4 2−(83.5%), and NO3 −(99.3%). Air mass trajectory analysis supported that the regional urban pollutions have significant influence on the dew water chemistry at the coastal Bhola, Bangladesh.

Collateral variations between the concentrations of mercury and other water soluble ions in volcanic ash samples and volcanic activity during the 2014–2016 eruptive episodes at Aso volcano, Japan

During 2014–2016, the Aso volcano, located in the center of the Kyushu Islands, Japan, erupted and emitted large amounts of volcanic gases and ash. Two episodes of the eruption were observed; firstly Strombolian magmatic eruptive episodes from 25 November 2014 to the middle of May 2015, and secondly phreatomagmatic and phreatic eruptive episodes from September 2015 to February 2016. Bulk chemical analyses on total mercury (Hg) and major ions in water soluble fraction in volcanic ash fall samples were conducted. During the Strombolian magmatic eruptive episodes, total Hg concentrations averaged 1.69±0.87ngg−1 (N=33), with a range from 0.47 to 3.8ngg−1. In addition, the temporal variation of total Hg concentrations in volcanic ash varied with the amplitude change of seismic signals. In the Aso volcano, the volcanic tremors are always observed during eruptive stages and quiet interludes, and the amplitudes of tremors increase at eruptive stages. So, the temporal variation of total Hg concentrations could provide an indication of the level of volcanic activity. During the phreatomagmatic and phreatic eruptive episodes, on the other hand, total Hg concentrations in the volcanic ash fall samples averaged 220±88ngg−1 (N=5), corresponding to 100 times higher than those during the Strombolian eruptive episode. Therefore, it is possible that total Hg concentrations in volcanic ash samples are largely varied depending on the eruptive type. In addition, the ash fall amounts were also largely different among the two eruptive episodes. This can be also one of the factors controlling Hg concentrations in volcanic ash.