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.

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.

2008-2020年重庆城市站点降水污染及湿沉降通量的演变特征和影响因素

基于东亚酸沉降监测网(EANET)观测数据,结合气象数据和社会经济数据,分析了2008-2020年重庆市降水中电导率、pH值和水溶性离子浓度及沉降量的演变特征和影响因素。结果表明:2008-2020年重庆市降水的pH、电导率、水溶性离子、硫湿沉降通量、硝态氮湿沉降通量和铵态氮湿沉降通量平均值分别为5.33、8.64mS/m、37.03mg/L、2731kg/(km^(2)·a)、273kg/(km^(2)·a)和1748kg/(km^(2)·a)。降水中水溶性离子浓度大小排序为:SO_(4)^(2)>NO_(3)>Ca^(2+)>NH_(4)^(+)>Cl>K^(+)>Mg^(2+)>Na^(+)>F^(-),其中SO_(4)^(2-)、NO_(3)^(-)、Ca^(2+)和NH_(4)^(+)分别占总离子浓度的45.2%、23.9%、13.0%和11.7%。降水污染存在显著的年际和逐月变化,年际变化主要受到污染物排放源的影响,逐月变化则主要受气象条件的影响。2008-2014年强酸性降雨占比(52.37%)较高,降水污染较重;2015-2020年强酸性降雨占比显著降低(3.74%),降水污染显著改善。2008-2010年为硫酸型降水,在2011-2020年为硫酸、硝酸混合型降水。夏季降水较多、大气扩散条件较好,降水中的污染物浓度较低,降水电导率最低,pH最高;冬季反之,降水电导率最高,pH最低。不同水溶性离子浓度占比的逐月变化较小。污染物的浓度对湿沉降通量年际变化的影响要大于降水量的影响,降水量对湿沉降通量逐月变化的影响要大于污染物浓度的影响。

盐碱土壤水溶性Cl^(-)、NO_(3)^(-)、SO_(4)^(2-)离子提取与离子色谱仪同时测定技术研究

为建立盐碱土中水溶性Cl^(-)、NO_(3)^(-)和SO_(4)^(2-)的提取与离子色谱仪同时测定的方法,选取采自新疆和宁夏2个盐碱地土样进行正交试验,优化土壤水溶性阴离子浸提过程,水土比例对水溶性离子的测定结果影响显著。选择浸提条件为水土比例5∶1,振荡时间为3 min,浸提液离心后过0.45μm滤膜,待测液Cl^(-)、NO_(3)^(-)、SO_(4)^(2-)采用离子色谱同时测定。结果表明,离子色谱法测定3种离子线性范围均为0.2~20 mg/L;方法检出限Cl^(-)为0.18 mg/kg,NO_(3)^(-)为0.12 mg/kg,SO_(4)^(2-)为0.38 mg/kg。3种离子6次测定结果相对标准偏差均<5%;加标回收率90.6%~104%;11种不同地点的盐碱土土壤水溶性盐浸提液中Cl^(-)、NO_(3)^(-)、SO_(4)^(2-)的测定结果分别与电位滴定法、连续流动分析仪法、硫酸钡质量法测定数值之间具有较好的相关性。本方法的检出限、准确度、精密度能满足盐碱土土壤水溶性Cl^(-)、NO_(3)^(-)和SO_(4)^(2-)离子含量的同时测定,省时省力。

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.

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.

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.

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.

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。

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.

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。

昆明市PM_(2.5)中水溶性无机离子的化学特征及来源解析

为探究昆明市大气中水溶性无机离子的化学组分、季节差异及主要来源,本研究于2019年12月至2020年11月在云南大学进行PM_(2.5)样品采集,利用离子色谱仪分析样品中水溶性无机离子的质量浓度,并结合离子相关性分析、后向轨迹分析和主成分分析等方法,阐明了昆明市大气中PM_(2.5)及其水溶性无机离子的季节污染特征及来源.结果表明,采样期间各季节总水溶性无机离子浓度均值排序为春季((5.6±2.2)μg·m^(−3))>冬季((5.5±2.6)μg·m^(−3))>秋季((4.3±2.8)μg·m^(−3))>夏季((3.6±2.2)μg·m^(−3)),水溶性无机离子年质量浓度的均值从大到小为SO_(4)^(2−)>Ca^(2+)>NO_(3)^(−)>NH_(4)^(+)>K^(+)>Cl^(−)>Na^(+)>Mg^(2+)>F^(−),其中SO_(4)^(2−)、Ca^(2+)、NO_(3)^(−)和NH_(4)^(+)是主要的水溶性无机离子.Ca^(2+)主要源于土壤粉尘,其他三者由前体物(SO_(2)、NO_(x)和NH_(3))二次转化生成,主要受化石燃料燃烧排放影响.SOR和NOR全年均值分别为0.20和0.02,表明在相同的环境里,SO_(2)二次转化为SO_(4)^(2−)的过程更易发生,且在秋季转化速率最大(SOR=0.23).SO_(4)^(2−)、NO_(3)^(−)和NH_(4)^(+)在秋季主要以NH_(4)NO_(3)和(NH_(4))_(2)SO_(4)的形式存在,其他三季则以NH_(4)HSO_(4)和NH_(4)NO_(3)的形式存在.昆明市大气PM_(2.5)中水溶性无机离子在冬、秋和春季一致,主要来自二次源和生物质燃烧源,其次是工业源和土壤尘,而夏季则主要来自机动车尾气、生物质燃烧源和土壤尘.除本地排放的影响外,冬季和夏季受到来自缅甸、老挝和贵州污染气团的影响,春季污染气团来自缅甸、云南本地和贵州,而秋季则受到云南东部和南部地区的气团输送影响.

华中背景地区大气颗粒物中水溶性离子特征与来源解析

为探究华中背景地区大气PM_(2.5)中水溶性无机离子(WSIIs)的特征、形成机制及来源,本研究在金沙国家大气本底站进行了为期一年的采样观测.结果表明:PM_(2.5)年均质量浓度为(31.40±2.05)µg/m^(3),季节变化明显,冬季最高,夏季最低.二次无机气溶胶(SNA,即SO_(4)^(2-)、NO_(3)^(-)和NH_(4)^(+))是WSIIs的重要组成部分,春季、夏季、秋季和冬季SNA在WSIIs所占比例分别为84.0%、77.6%、79.8%和84.5%.研究期间阴阳离子物质的量当量比值(AE/CE)的平均值为0.91,PM_(2.5)呈现弱碱性.(NH_(4))2SO_(4)、NH_(4)NO_(3)和NH_(4)Cl是夏季离子形态的主要形式,而(NH_(4))2SO_(4)是春、秋、冬季的主要离子形态.硫氧化率(SOR)和氮氧化率(NOR)分别为0.48和0.14,与PM_(2.5)呈显著正相关,表明SO_(4)2-和NO_(3)-主要来自二次生成,二次转化是PM_(2.5)浓度上升重要原因.WSIIs的潜在来源和传输路径具有明显的季节特征,近距离输送气流的SOR和NOR均较大,污染物从源区向背景地区迁移过程中二次转化明显,来自西北或者正北方的远距离气团携带的污染物浓度较大,受到明显的区域传输影响.