Application of ion chromatography to the determination of water-soluble inorganic and organic ions in atmospheric aerosols

A simple, sensitive and convenient ion chromatography(IC) method was established for the simultaneous determination of twelve water-soluble inorganic anions(F -, Cl -, NO - 2, NO - 3, SO 2- 3, SO 2- 4, PO 3- 4), and fifteen water-soluble organic ions(formate, acetate, MSA, oxalate, malonate, succinate, phthalates, etc.) in atmospheric aerosols. The linear concentrations ranged from 0.005 μg/m 3 to 500 μg/m 3(r = 0.999—0.9999). The relative standard deviation(RSD) were 0.43%—2.00% and the detection limits were from 2.7 ng/m 3 to 88 ng/m 3. The proposed method was successfully applied to the simultaneous determination of those inorganic ions and organic ions in PM 2.5 of Beijing.

On-line Measurement of Water-Soluble Ions in Ambient Particles

Combining the system of rapid collection of ambient particles and ion chromatography, the system of rapid collection of fine particles and ion chromatography （RCFP-IC） was established to automatically analyze on-line the concentrations of water-soluble ions in ambient particles. Here, the general scheme of RCFP-IC is described and its basic performance is tested. The detection limit of RCFP-IC for SO4^2-, NO3^-, NO2^-, Cl^- and F- is below 0.3μg m^-3. The collection efficiency of RCFP-IC increases rapidly with increasing sized particles. For particles larger than 300 nm, the collection efficiency approaches 100%. The precision of RCFP-IC is more than 90% over 28 repetitions. The response of RCFP-IC is very sensitive and no obvious cross-pollution is found during measurement. A comparison of RCFP-IC with an integrated filter measurement indicates that the measurement of RCFP-IC is comparable in both laboratory experiments and field observations. The results of the field experiment prove that RCFP-IC is an effective on-line monitoring system and is helpful in source apportionment and pollution episode monitoring.

Diurnal variations of water-soluble ions in PM_(2.5)in Shanghai

Thirty-six daily time interval PM2.5 samples were collected in different seasonal dates in urban Shanghai, and the concentrations of four anions （Cl- , NO3-, SO4^2-, C2O4^2-） and five cations （NH＋, Na＋, K＋, Ca2＋, Mg2＋） were analyzed with ion chromatography. Sulfate, nitrate and ammonium were found to be the dominant species, accounting for about 80% of the total ions. The daily nitrate to sulfate mass ratio ranged from 0.31 to 0.82, indicating that coal combustion was still the main pollution source in Shanghai. The equivalent ratio of ammonium to stun of nitrate and sulfate showed fixed diurnal variation pattern in all the sampling days with higher values in the nighttime, suggesting that fine particles in the night were more neutralized. The oxalate to sulfate ratio was lower in the winter sampling days than that in hotter summer and autumn sampling days. Oxalate was significantly correlated with sulfate in winter sampling days, but not in the summer and autumn, suggesting that the formation mechanism of oxalate and sulfate was similar in winter, however different in hot days.

Real-Time Observation on Water-Soluble Ions of PM_(2.5)in Beijing under the Influences of Different Air Masses in Summer

To further understand the variations of water-soluble ions in PM2.5 in Beijing,the authors observed their concentrations continuously and in high temporal resolution by the system for rapid collection of fine particles and ion chromatography(RCFP-IC) during 12–18 July 2010.These results combined with those of earlier backward trajectory research are used analyzed to determine the causes of concentration changes in water-soluble ions under the influences of two kinds of air masses in summer.The results indicate that concentrations of NO3-,SO42-,and NH4+ were influenced strongly by the continental air mass than by the marine air mass.Cl- and Na+ were not changed significantly.Because the sources of K+,Mg2+,and Ca2+ are mainly concentrated on land,their concentration levels were slightly higher under the control of continental air mass than that of the marine air mass.Variations of NO2- during the observation differed from those of other ions;its concentration was significantly higher under the influence of marine air mass.Moreover,the authors obtain the diurnal variations of eight water-soluble inorganic ions including NH4+,K+,Mg2+,Ca2+,Cl-,NO2-,NO3-,and SO42-.Diurnal variations of NH4+,NO3-,and Cl- showed single peak,which appeared before noon,while SO42- showed two peaks that appeared during rush hours.Those of Mg2+,Ca2+,and K+ showed single peak that appeared in the afternoon.That of NO2- showed with a peak appearing at sunrise and a valley appearing at sunset.

Water Soluble Ionic Species in the Atmospheric Fine Particulate Matters (PM2.5) in a Southeast Asian Mega City (Dhaka, Bangladesh)

Atmospheric fine particulate matters (PM2.5) were collected with an Envirotech Instrument (Model APM 550) at the roof of Khundkur Mukarram Hussain Science Building, University of Dhaka, Bangladesh between January and February, 2013. PM2.5 samples were collected on Quartz fiber filters during day and night time. Water soluble ions (sulfate, nitrate, phosphate, chloride, bromide, sodium, potassium and calcium) were analyzed with Ion Chromatography (Model 881, Metrohm Ltd., Switzerland) and Flame photometer (Model PFP7, Jenway, UK). Average PM2.5 mass was 136.1 μg&#183m&#453 during day time and 246.8 μg&#183m&#453 during night time with a total average of 191.4 μg&#183m&#453. Nighttime PM2.5 concentration was about double compared than that of daytime presumable due to the low ambient temperatures with high emissions from heavy duty vehicles. The 24-hour average PM2.5 mass (average of day and night) was about eight times higher than WHO (25.0 μg&#183m&#453) and about three times higher than DoE, Bangladesh (65.0 μg&#183m&#453) limit values. The total average concentrations of sulfate, nitrate, phosphate, bromide, chloride, sodium, potassium and calcium were 5.30, 7.75, 0.62, 0.16, 1.19, 1.30, 8.11, and 3.09 μg&#183m&#453, respectively. The concentrations of the water soluble ions were much higher during nighttime than daytime except nitrate, bromide and potassium. Excellent correlations were observed between sulfate and nitrate, sodium and chloride, bromide and phosphate indicating joint sources of origin. Potassium, sulfate, nitrate and calcium are the most dominant species in PM2.5. Water soluble ionic components in Dhaka contributed about 15% mass of the PM2.5. Ratio analysis showed that sodium and chloride were from mainly sea salt. Potassium has varieties of sources other than biomass burning. Sulfate and nitrate are mainly from fossil fuel origin. This is the first study of the day and night variation of the water soluble ionic species at the fine particulate matters (PM2.5) in Bangladesh.

Water soluble components of PM_(10) in Chongqing, China

The concentrations of water soluble ions (Na++, NH++-4, K++, Mg+{2+}, Ca+{2+}, NO+--3, Cl+-, and SO+{2-}-4) in PM-{10} samples collected on cellulose filters by a medium-volume cascade impactor were determined, which were obtained from three kinds of areas in Chongqing: industrial area (Jiulongpo district), commercial and residential area (Jiangbei district) and background area (Jinyun Mountain in the Beibei district). The results showed that except for the background site, the annual average values of PM-{10} are 23%-61% higher than the national air quality standard (GradeⅡ) ({0.1} mg/m+3), even that the value of the control site is still 20% higher than American standard ({0.05} mg/m+3). This implied that serious pollution of fine particles occurred in Chongqing. Nine kinds of soluble ions in water of PM-{10} were analyzed by ion chromatography (IC) and the annual average concentrations follow the order of >>>, and >>>>. Their values were different in these areas: the industrial area>the commercial and living area>the control area. As for NH++-4, K++, Ca+{2+}, NO+--3 and SO+{2-}-4, their seasonal average concentrations show a similar variation trend: the values in spring and fall were higher than those in summer and winter. The seasonal average concentrations of , , and are much lower than those of other ions. However, the concentrations of changed more greatly in different seasons than those of the other three ions. Correlation coefficients showed that the three areas have been polluted by coal smoke and dust to different extents, while some local resources of pollution should be taken into consideration as well.

A strategy based on water soluble coal tar pitches to construct MnO_(2)@C composite materials with high electrochemical performance

The water soluble coal tar pitches(WS-CTPs)were successfully prepared and used to construct the MnO_(2)@C composite materials by a hydrothermal method.It is interestingly observed that the structures and morphologies of MnO_(2)@C materials can be controlled by controlling the dosages of WS-CTPs and KMnO4.Meanwhile,it is aware that MnO_(2)exists in the MnO_(2)@C materials in an amorphous state.Compared with MnO_(2),MnO_(2)@C materials output a remarkable improvement in electrochemical performance.For instance,MnO_(2)@C-0.3 shows the storage capacity at 965.7 mA h g^(−1)after 300 cycles at a current density of 0.1 A g^(−1).In addition,after 600 cycles at a current density of 1.0 A g^(−1),the storage capacity of MnO_(2)@C-0.3 still keeps 450.3 mA h g^(−1),indicating that MnO_(2)@C-0.3 owns tremendous cycle stability at a high current density.In view of the fact that the coal tar pitches possess great cost advantages,the strategy of using WS-CTPs as a carbon source to cover the metal oxides is a competitive way to expand the application of metal oxides in the fabrication of electrodes of LIBs.

Comparative study on water-soluble inorganic ions in PM2.5 from two distinct climate regions and air quality

Recently, air quality has significantly improved in developed country, but that issue is of concern in emerging megacity in developing country.In this study, aerosols and their precursor gas were collected by NILU filter pack at two distinct urban sites during the winter and summer in Osaka, Japan and dry and rainy seasons in Ho Chi Minh City(HCMC),Vietnam.The aims are to investigate the contribution of water-soluble inorganic ions(WSIIs) to PM2.5, thermodynamic characterization and possible formation pathway of secondary inorganic aerosol(SIA).The PM2.5 concentration in Osaka(15.8 μg/m^3) is lower than that in HCMC(23.0 μg/m^3), but the concentration of WSIIs in Osaka(9.0 μg/m^3) is two times higher than that in HCMC(4.1 μg/m^3).Moreover, SIA including NH4^+, NO3^-and SO4^2-are major components in WSIIs accounting for 90% and 76%(in molar) in Osaka and HCMC,respectively.Thermodynamic models were used to understand the thermodynamic characterization of urban aerosols.Overall, statistical analysis results indicate that very good agreement(R2> 0.8) was found for all species, except for nitrate aerosol in HCMC.We found that when the crustal species present at high amount, those compositions should be included in model calculation(i.e.in the HCMC situation).Finally, we analyzed the characteristics of NH4^+– NO3^-– SO4^2-system.A possible pathway to produce fine nitrate aerosol in Osaka is via the homogeneous reaction between NH3 and HNO3, while nonvolatile nitrate aerosols can be formed by the heterogeneous reactions in HCMC.

Size distributions of aerosol and water-soluble ions in Nanjing during a crop residual burning event

To investigate the impact on urban air pollution by crop residual burning outside Nanjing, aerosol concentration, pollution gas concentration, mass concentration, and water-soluble ion size distribution were observed during one event of November 4-9, 2010. Results show that the size distribution of aerosol concentration is bimodal on pollution days and normal days, with peak values at 60- 70 and 200-300 nm, respectively. Aerosol concentration is 104 cm-3.nm-1 on pollution days. The peak value of spectrum distribution of aerosol concentration on pollution days is 1.5-3.3 times higher than that on a normal day. Crop residual burning has a great impact on the concentration of fine particles. Diurnal variation of aerosol concentration is trimodal on pollution days and normal days, with peak values at 03：00, 09：00 and 19：00 local standard time. The first peak is impacted by meteorological elements, while the second and third peaks are due to human activities, such as rush hour traffic. Crop residual burning has the greatest impact on SO2 concentration, followed by NO2, 03 is hardly affected. The impact of crop residual burning on fine particles （〈 2.1 μm） is larger than on coarse particles （〉 2.1 μm）, thus ion concentration in fine particles is higher than that in coarse particles. Crop residual burning leads to similar increase in all ion components, thus it has a small impact on the water-soluble ions order. Crop residual burning has a strong impact on the size distribution of K^＋, Cl^-, Na^＋, and F- and has a weak impact on the size distributions of NH4^＋, Ca^2＋, NO3^- and SO4^2-.

Characteristics of size distributions and sources of water-soluble ions in Lhasa during monsoon and non-monsoon seasons

To understand the physical and chemical characteristics, particle size distribution and sources of size-separated aerosols in Lhasa, which is located on the Tibetan Plateau(TP), six sizes of aerosol samples were collected in Lhasa in 2014. Ca^(2+), NH_4^+, NO_3^-,SO_4^(2-)and Cl-were the dominant ions. The ratio of cation equivalents(CE) to anion equivalents(AE) for each particle size segment indicated that the atmospheric aerosols in Lhasa were alkaline. SO_4^(2-)and NO_3^-could be neutralized by Ca^(2+), but could not be neutralized by NH_4^+, according to the [NH_4^+]/[NO_3^-+ SO_4^(2-)] and [Ca^(2+)]/[NO_3^-+ SO_4^(2-)] ratios. Mobile sources were dominant in PM_(0.95-1.5),PM_(1.5-3) and PM_(3-7.2), while stationary sources were dominant in the other three size fractions according to the [NO_3^-]/[SO_4^(2-)] ratios. The particle size distribution of all watersoluble ions during monsoon and non-monsoon periods was characterized by a bimodal distribution due to the different sources and formation mechanisms, and it was revealed that different ions had different sources in different seasons and different particle size segments by combining particle size distribution with correlation analysis. Source analysis of aerosols in Lhasa was performed using the Principal component analysis(PCA) for the first time, which revealed that combustion sources, motor vehicle exhaust, photochemical reaction sources and various types of dust were the main sources of Lhasa aerosols.Furthermore, Lhasa's air quality was also affected by long-distance transmission, expressed as pollutants from South Asia and West Asia, which were transmitted to Lhasa according to backward trajectory analysis.

Seasonal variations and size distributions of water-soluble ions in atmospheric aerosols in Beijing, 2012

The characteristics of water-soluble ions in airborne particulate matter in Beijing were investigated using ion chromatography. The results showed that the total concentrations of ions were 83.7 ± 48.9 μg/m3 in spring, 54.0 ± 17.0 μg/m3 in summer, 54.1 ± 42.9 μg/m3 in autumn, and 88.8 ± 47.7 μg/m3 in winter, respectively. Furthermore, out of all the ions, NO3-,SO42-and NH4＋accounted for 81.2% in spring, 78.5% in summer, 74.6% in autumn, and 76.3%in winter. Mg2＋and Ca2＋were mainly associated with coarse particles, with a peak that ranged from 5.8 to 9.0 μm. Na＋, NH4＋and Cl-had a multi-mode distribution with peaks that ranged from 0.43 to 1.1 μm and 4.7 to 9.0 μm. K＋, NO3-, and SO42-were mainly associated with fine particles, with a peak that ranged from 0.65 to 2.1 μm. The concentrations of Na＋, K＋,Mg2＋, Ca2＋, NH4＋, Cl-, NO3-and SO42-were 2.69, 2.32, 1.01, 4.84, 16.9, 11.8, 42.0, and 44.1 μg/m3 in particulate matter（PM） on foggy days, respectively, which were 1.4 to 7.3 times higher than those on clear days. The concentrations of these ions were 2.40, 1.66, 0.92, 4.95, 17.5,7.00, 32.6, and 34.7 μg/m3 in PM on hazy days, respectively, which were 1.2–5.7 times higher than those on clear days.

Size-resolved aerosol water-soluble ions at a regional background station of Beijing, Tianjin, and Hebei, North China

The characteristics of water-soluble ions in size-resolved particulate matter were investigated usingion chromatography at Shangdianzi, a regional background station of Beijing, Tianjin, and Hebei. Seasonal total concentrations of ions （Na＋, Mg2＋, IC, Ca2＋, NH＋4, Cl-, SO2-4 and NO-3） were 75.5 ± 52.9 μg/m3 in spring, 26.5 ± 12.3 Bg/m3 in summer, 22.7 ± 20.4 μg/m3 in autumn, and 31.1 ± 23.9 μg/m3 in winter, respectively. The secondary ions （NO3, SO2-4 and NH＋4）, mainly associated with fine particles, accounted for 84.2% in spring, 82.1% in summer, 81.5% in autumn and 76.3% in winter of all ions. Strong correlations were found between NH＋4 and SO2-4 （r = 0.95, p 〈 0.01） as well as NH＋4 and NO-3 （r = 0.90, p 〈 0.01） in fine particles; while in coarse particles, correlations between Mg2＋ and NO-3 （r = 0.80, p 〈 0.01）, and Ca2＋ and NO2＋ （r = 0.85, p 〈 0.01） were found. The concentrations of Na＋, IC, Mg2＋, Ca2＋, NH＋4, Cl-, NO3, and SC2-4 were 2.02, 0.81, 0.36, 1.65, 9.58, 4.01, 18.9, and 18.4 μg/m3 in particulate matter from southeast-derived air masses, which were typically 1.58-3.37 times higher than in northwest trajectories. Thus, concentrations of water-soluble ions at this background station were heavily influenced by regional transport of serious pollution derived from biomass burning, coal combustion, industrial and vehicle exhaust emissions from Beijing, Tianjin, and Hebei.

Emission of organic carbon, elemental carbon and water-soluble ions from crop straw burning under flaming and smoldering conditions

Emissions from major agricultural residues were measured using a self-designed combustion system. Emission factors （EFs） of organic carbon （OC）, elemental carbon （EC）, and water-soluble ions （WSIs） （K＋, NH4＋, Na＋, Mg2＋, Ca2＋, Cl-, NO3-, SO42–） in smoke from wheat and rice straw were measured under flaming and smoldering conditions. The OC1/TC （total carbon） was highest （45.8% flaming, 57.7% smoldering） among carbon fractions. The mean EFs for OC （EFOC） and EC （EFEC） were 9.2 ± 3.9 and 2.2 ± 0.7 g/kg for wheat straw and 6.4 ± 1.9 and 1.1 ± 0.3 g/kg for rice straw under flaming conditions, while they were 40.8 ± 5.6 and 5.8 ± 1.0 g/kg and 37.6 ± 6.3 and 5.0 ± 1.4 g/kg under smoldering conditions, respectively. Higher EC ratios were observed in particulate matter （PM） mass under flaming conditions. The OC and EC for the two combustion patterns were significantly correlated （p 〈 0.01, R = 0.95 for wheat straw; p 〈 0.01, R = 0.97 for rice straw）, and a higher positive correlation between OC3 and EC was observed under both combustion conditions. WSIs emitted from flaming smoke were dominated by Cl- and K＋, which contributed 3.4% and 2.4% of the PM mass for rice straw and 2.2% and 1.0% for wheat straw, respectively. The EFs of Cl- and K＋ were 0.73 ± 0.16 and 0.51 ± 0.14 g/kg for wheat straw and 0.25 ± 0.15 and 0.12 ± 0.05 g/kg for rice straw under flaming conditions, while they were 0.42 ± 0.28 and 0.12 ± 0.06 g/kg and 0.30 ± 0.27 and 0.05 ± 0.03 g/kg under smoldering conditions, respectively. Na＋, Mg2＋, and NH4＋ were vital components in PM, comprising from 0.8% （smoldering） to 3.1% （flaming） of the mass. Strong correlations of Cl- with K＋, NH4＋, and Na＋ ions were observed in rice straw and the calculated diagnostic ratios of OC/EC, K＋/Na＋ and Cl-/Na＋ could be useful to distinguishing crop straw burning from other sources of atmospheric pollution.

The spatial and temporal distribution and characteristics of inorganic ion concentrations of TSP in the Tarim Basin

Based on Total Suspended Particulates （TSP） observations of Tazhong, Tikanli, Kashi and Minfeng in 2009, combined wa- ter-soluble inorganic ion analyses, this paper studied the spatial and temporal distribution of TSP in the Tarim Basin and analyzed concentration characteristics. The results are as follows： （1） monthly average TSP concentrations shows a similar trend in Tazhong, Tikanli, Kashi and Minfeng with peak values in April-May and low values in November-December. As for the quarter average mass concentration trends, spring has the highest value, followed by summer and autumn, and winter is the lowest; （2） total annual concentration trend of water-soluble inorganic ions in TSP is as follows： Tazhong 〉 Tikanli 〉 Minfeng 〉 Kashi. SO4^2- concentra- tions are 58%, 50%, 54% and 51% of total ion concentration; Ca^2＋ concentrations are 13%, 16%, 16% and 11%; Na^＋ concentra- tions are 12%, 13%, 10% and 12% and Cl^- concentrations are 12%, 16%, 11% and 22%, respectively. Therefore, sulfate, calcium, sodium and chloride ions are the main inorganic components of TSP in the Tarim Basin; （3） the correlation coefficients of anions and cations in Tikanli, Minfeng, Kashi and Tazhong are 0.99, 0.99, 0.25 and 0.91, respectively; the average anion concentrations are 2.57, 2.12, 2.15 and 3.02 times the average cation concentrations, indicating that ions were unbalanced; （4） SO4^2-/NO3^- ratio is much larger than the ratio of coal-fired emissions SO4^2-/NO3^-, thus the impact of fixed emission sources in the four regions on the atmosphere is far greater than that of mobile emission sources.

Environmental significance and hydrochemical characteristics of rivers in the western region of the Altay Mountains,China

Analysis of environmental significance and hydrochemical characteristics of river water in mountainous regions is vital for ensuring water security.In this study,we collected a total of 164 water samples in the western region of the Altay Mountains,China,in 2021.We used principal component analysis and enrichment factor analysis to examine the chemical properties and spatiotemporal variations of major ions(including F-,Cl-,NO_(3)-,SO_(4)^(2-),Li+,Na+,NH4+,K+,Mg^(2+),and Ca^(2+))present in river water,as well as to identify the factors influencing these variations.Additionally,we assessed the suitability of river water for drinking and irrigation purposes based on the total dissolved solids,soluble sodium percentage,sodium adsorption ratio,and total hardness.Results revealed that river water had an alkaline aquatic environment with a mean pH value of 8.00.The mean ion concentration was ranked as follows:Ca^(2+)>SO_(4)^(2-)>Na+>NO_(3)->Mg^(2+)>K+>Cl->F->NH_(4)+>Li+.Ca^(2+),SO_(4)^(2-),Na+,and NO_(3)-occupied 83%of the total ion concentration.In addition,compared with other seasons,the spatial variation of the ion concentration in spring was obvious.An analysis of the sources of major ions revealed that these ions originated mainly from carbonate dissolution and silicate weathering.The recharge impact of precipitation and snowmelt merely influenced the concentration of Cl-,NO_(3)-,SO_(4)^(2-),Ca^(2+),and Na+.Overall,river water was in pristine condition in terms of quality and was suitable for both irrigation and drinking.This study provides a scientific basis for sustainable management of water quality in rivers of the Altay Mountains.

天津市2018—2020年春节PM_(2.5)中水溶性无机离子特征及重污染过程分析

为阐明大气污染重点整治和新冠疫情影响下我国华北地区城市春节期间重污染过程PM_(2.5)中水溶性无机离子变化特征及其影响因素,本研究结合气态前体物浓度和气象要素,对天津市2018—2020年连续3年春节假期的2次重污染过程PM_(2.5)中主要水溶性无机离子(WSIIs)浓度进行对比分析.结果表明,2018年和2020年春节假期PM_(2.5)平均浓度(98.32μg·m^(-3)和137.7μg·m^(-3))显著高于2019年(49.97μg·m^(-3)).PM_(2.5)平均浓度在污染期Ⅱ(2020年为206.5μg·m^(-3))是污染期Ⅰ(2018年98.32μg·m^(-3))的2.1倍;2次污染事件中NO_(2)浓度变化不大,而SO_(2)浓度在污染期Ⅱ(14.89μg·m^(-3))是污染期Ⅰ(30.04μg·m^(-3))的49.6%.SNA在WSIIs中占比超过77%,主要以NH_(4)NO_(3)、(NH_(4))_(2)SO_(4)形式存在,其中NH_(4)NO_(3)为最主要的无机盐,且污染期Ⅱ的NH_(4)NO_(3)浓度远高于污染期Ⅰ.此外,污染期Ⅱ的PM_(2.5)/CO、SOR、NOR均明显升高,表明更有效的SO_(4)^(2-)和NO_(3)^(-)形成过程是导致污染期Ⅱ中PM_(2.5)浓度偏高的主要原因之一.不利的边界层高度、相对湿度、风速等气象要素形成静稳、强逆温天气,导致大气环境容量减小,并使得污染期Ⅱ的二次无机气溶胶生成效率大幅提高,进而削弱了疫情效应与减排措施的影响.而污染期Ⅰ除了二次转化外,PM_(2.5)浓度可能更多受到区域传输等影响.

Composition and mixing state of water soluble inorganic ions during hazy days in a background region of North China

Knowledge of haze particles in background areas of North China is limited, although they have been studied well in urban settings. Atmospheric aerosol particles were collected at a background site in the North China Plain during 16–31 January, 2011. Water soluble inorganic ions of PM2.5 and physicochemical characteristics of individual particles on hazy and clean days were measured by Ion Chromatography(IC) and Transmission Electron Microscopy(TEM), respectively. Average PM2.5 mass concentration was 50.4±29.9 μg m?3 with 62.5±26.8 μg m?3 on hazy days and 19.9±11.5 μg m?3 on clean days. SO42?, NO3?, and NH4+ with a combined mass concentration of 19.0±11.5 μg m?3 accounted for 69.8%–89.4% of the total water soluble inorganic ions. Size distributions of SO42? and NH4+ showed one unimodal peak at 0.56–1.8 μm on hazy days, whereas NO3? appeared as bimodal peaks at 0.56–1.8 and 5.6–10 μm, respectively. Individual particle analyses showed that the dominant aerosols were a mixture of sulfate, nitrate, and carbonaceous species, which together determine their mixing states. 48-h air mass back trajectories on hazy days suggested that air masses crossed the polluted continental areas(such as Jing-jin-ji region and Shandong province) and entrained ground air pollutants 11–19 hours before reaching the background area. During long-range transport particles undergo ageing and tend to be internally mixed mainly due to condensation in the background atmosphere. Our results suggest that hygroscopic and optical properties of these aerosol particles in the background area differ substantially from those in urban areas.

第十四届全运会大气污染物减排措施对西安市气溶胶中水溶性离子和含碳组分的影响

人为源密集的城市是空气污染影响的主要区域,厘清城市地区排放源的变化与大气污染物浓度之间的影响作用机制,有助于协调我国大气污染防控与城市社会经济发展之间的关系。为研究第十四届全运会期间大气污染物减排措施对西安市大气污染物(PM_(2.5)、PM_(10)、SO_(2)、NO_(2)、O_(3)和CO)的影响,于2021年8月6日至10月1日使用在线监测仪器观测了环境六要素、气象要素和PM_(2.5)中的气溶胶化学组分(有机碳、元素碳和水溶性离子)。结果表明:大气污染物减排措施对主要污染物O_(3)和PM_(2.5)浓度日变化的影响不同,主要由温度对光化学过程的影响和扩散条件差异导致。O_(3)在减排措施实施期间晴天峰值浓度更高、持续时间更长、浓度变化更迅速。PM_(2.5)在减排措施实施前晴天白天的峰值浓度较高,并在减排措施实施期间晴天夜间的峰值浓度较高。大气污染物减排措施对PM_(2.5)中化学组分的影响不同,尤其是对有机碳的组成影响较大。与减排措施实施前晴天相比,减排措施实施期间晴天NO_(3)^(-)、SO_(4)^(2-)、NH_(4)^(+)、Cl^(-)、Ca^(2+)、Na^(+)和NO_(2)^(-)浓度降低了17.9%~71.8%,K^(+)、Mg^(2+)和元素碳浓度增加了1.9%~13.6%,有机碳浓度仅降低了1.0%,但是一次有机碳浓度增加了13.6%,二次有机碳浓度降低了4.7%。NO_(3)^(-)/SO_(4)^(2-)值在减排措施实施期间晴天(0.53)远低于减排措施实施前晴天(1.66),表明减排措施实施期间交通源的贡献显著降低。降雨对NO_(3)^(-)和NH_(4)^(+)的清除较弱,反而会增加其浓度,但对K^(+)、Mg^(2+)、Ca^(2+)和Na+的清除作用较强。NO_(3)^(-)、SO_(4)^(2-)和NH_(4)^(+)在减排措施实施前后均是水溶性离子最重要的组成,在水溶性离子中的占比为90.8%(减排措施实施前的晴天)~95.8%(减排措施实施期间的雨天)。二次有机碳是有机碳的主要组成,占比为75.5%(减排措施实施期间的雨天)~79.9%(减排措施实施前的晴天)。不同阶段的水溶性离子和含碳气溶胶浓度日变化特征不同。NO_(3)^(-)、SO_(4)^(2-)和NH_(4)^(+)浓度晴天的日变化为单峰型分布,雨天为多峰型分布。

离子色谱法测定电解电容器纸中水溶性氯化物的含量

采用抽提法对电解电容器纸进行前处理,再用离子色谱法对其中的水溶性氯化物进行测定。结果表明,氯离子的质量浓度在0.02~1.00μg/mL范围内与峰面积呈线性关系,相关系数大于0.999;对样品前处理方法进行了优化,并对优化后的方法进行了方法学验证,方法检出限为0.06 mg/kg,测定结果的相对标准偏差为7.04%(n=6),加标回收率为97.62%~101.95%,相对标准偏差为2.33%。该方法检出限较低,前处理过程简便、环保,用于实际样品分析,测定结果满意,适用于电解电容器纸中水溶性氯化物含量的测定。

北京地区重霾污染过程颗粒物酸度演变特征及其驱动机制

基于北京秋冬季重霾污染时期细颗粒物化学组分和气态前体物的小时观测数据,通过ISORROPIA II模型模拟颗粒物酸度,并利用敏感性分析方法研究颗粒物酸度的驱动因子。结果表明:2017~2019年秋冬季,北京3次重霾污染事件颗粒物pH的平均值分别为4.52±0.52、5.19±0.28和5.03±0.79;从清洁阶段到中度污染阶段和从中度污染阶段到重度污染阶段,颗粒物pH平均值分别下降0.72~1.07和0.3~1.03,即随着污染的加重,颗粒物pH呈现下降趋势;颗粒物pH对化学组分变化的响应不同,主要受TNHx[总铵(气态氨+颗粒态铵盐)]和SO_(4)^(2−)影响,受环境温度和湿度变化的影响有限;颗粒物pH对TNHx的敏感性依次高于SO_(4)^(2−)高于NO_(3)^(−),且高的TNHx水平会降低颗粒物pH对SO_(4)^(2−)(TNHx>47μg/m^(3))和NO_(3)^(−)(TNHx>30~40μg/m^(3))的敏感性;北京重霾污染时期,大气处于富氨状态,抬升颗粒物pH至4以上;在重霾污染事件中,颗粒物pH及变化的幅度与总铵水平和颗粒物pH对SO_(4)^(2−)、NO_(3)^(−)的敏感性有关,这为厘清二次气溶胶生成机制提供有效参考。