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.

Concentrations,sources,and influential factors of water-soluble ions of atmospheric particles in Dunhuang Mogao Grottoes,a world heritage site in China

Atmospheric particle pollution is one of the major factors leading to degradation of ancient wall paintings,particularly heritage sites in arid and semi-arid regions.However,current systematic research on the changes,sources,and influential factors of atmospheric particulate matter and its water-soluble ion concentrations is not sufficient.Thus,the major water-soluble ion concentrations,sources,and influential factors of atmospheric particles PM_(2.5) and PM_(10)(particulate matter with an aerodynamic equivalent diameter≤2.5 and 10.0μm,respectively,in ambient air)were collected from Cave 16 and its ambient exterior environment in the Dunhuang Mogao Grottoes,China,between April 2015 and March 2016.Results showed that the concentrations of PM_(2.5) and PM_(10) inside and outside the cave were the highest in March 2016 and the lowest in December 2015.The higher particle concentration from March to May was related to the frequent occurrence of sand and dust events,and the lower particle concentration from June to September was associated with good diffusion conditions,increased precipitation,and an established cave shelterbelt.The concentration of particulate matter inside the cave was affected by the concentration of particles in the air outside the cave.Ca2+,NH+4,Na+,Cl-,and SO2-4were the main components of the total ions of PM_(2.5) and PM_(10) both inside and outside the cave.The total ions inside the cave were frequently affected by the disturbance of tourists'activities during the peak tourist season from May to August.Under the influence of dust,the total concentrations of Cl-,SO2-4,Na+,NH+4,and Ca2+in particles of different sizes inside and outside the cave increased,and the concentrations of Cl-,SO2-4,Na+,and Ca2+decreased during precipitation period.Backward air mass trajectory analysis suggested that the pollutants were mainly from Xinjiang,China.The pollutant sources of air particulates are straw burning,secondary pollution sources,soil dust,dry spring rivers,and tourist activities.

Sheath structure in plasma with two species of positive ions and secondary electrons

The properties of a collisionless plasma sheath are investigated by using a fluid model in which two species of positive ions and secondary electrons are taken into account. It is shown that the positive ion speeds at the sheath edge increase with secondary electron emission（SEE） coefficient, and the sheath structure is affected by the interplay between the two species of positive ions and secondary electrons. The critical SEE coefficients and the sheath widths depend strongly on the positive ion charge number, mass and concentration in the cases with and without SEE. In addition, ion kinetic energy flux to the wall and the impact of positive ion species on secondary electron density at the sheath edge are also discussed.

Characteristics of Aerosol Pollution Under Different Visibility Conditions in Winter in a Coastal Mega-City in China

To investigate chemical profiles and formation mechanisms of aerosol particles in winter haze events,comprehensive measurements including hourly concentrations of PM2.5 and water-soluble inorganic ions and related gasphase precursors were conducted via an online monitoring system from January to March of 2016 in Shenzhen,a coastal mega-city in south China.In this study,high concentrations of PM2.5,NO2 and lower levels of O3 were observed during haze periods in comparison with clear days(Visibility>15 km).The major secondary ionic species were NH+4、NO-3 and SO2-4,which varied significantly on haze and clear days.The ratio of NO-3/SO2-4 in haze days was greater than that on clear days and tended to be larger when air pollution became more serious.At the same time,compared with previous studies,it has been found that the ratio has been increasing gradually in Shenzhen,indicating that the motor vehicle exhaust emissions have a more and more important impact on air quality in Shenzhen.Sulfur oxidation rate(SOR)and nitrogen oxidation rate(NOR)was higher during the haze period than that in clean days,indicating efficient gas to particle conversion.Further analysis shows that high concentrations of sulfate might be explained by aqueous oxidation,but gas-phase reactions might dominate nitrate formation.This study also highlights that wintertime nitrate formation can be an important contributor to aerosol particles,especially during haze periods.

Hydrochemical Characteristics and Ion Transfer of Rainfall of Betula Platyphylla Secondary Forest in Xiaowutai Mountain

In order to study hydrochemical characteristics and ion transfer of annual rainfall of Betula platyphylla secondary forest,water samples of rainfall,throughfall,stemflow,litter infiltration water and slope runoff of Betula platyphylla secondary forest in the early growth stage,fastgrowing stage and growth decline stage in Shanjiankou watershed of Xiaowutai Mountain and nine indexes of pH,Ca^2+,Mg^2+,K+,Na+,Zn^2+,Mn^2+,Fe^2+ and Cu^2+ were determined.The results showed that:①The annual rainfall was weakly alkaline,and the ion concentration in different stages was obviously different.According to the ratio of the maximum concentration to the minimum concentration of the same ion,the rank was Mg^2+ > Mn^2+ >Na+ > K+ > Ca^2+ > Cu^2+ > Fe^2+ > Zn^2+.②Compared with the rainfall in the same period,in the early growth stage,Mg^2+,Mn^2+,Na+,K+,Ca^2+,Fe^2+ and Zn^2+ showed leaching loss in each distribution process.In the fastgrowing stage,Ca^2+,Mn^2+ and Fe^2+ showed leaching loss in each distribution process;Mg^2+ showed absorption,Na+ showed leaching loss in slope runoff and showed absorption in other process.K+ showed leaching loss in stemflow and showed absorption in other process.Zn^2+ showed absorption in stemflow and slope runoff and showed a little leaching loss in other process.In the late growth stage,Ca^2+,Mg^2+,Zn^2+,Mn^2+ and Fe^2+ showed leaching loss in each distribution process;Na+ and Cu^2+ showed absorption;K+ showed absorption in stemflow and showed leaching loss in other process.Most of the rainfall and metal ions in Betula platyphylla secondary forest were intercepted by litter layer.

A depressant for marmatite flotation:Synthesis,characterisation and floatation performance

This study synthesised a zincic salt(ZS)as a depressant for marmatite-galena separation.The effect of ZS on the flotation of marmatite and galena was investigated through micro-flotation tests.88.89%of the galena was recovered and 83.39%of the marmatite was depressed with ZS dosage of 750 mg·L^(−1)at pH=4.The depression mechanism of ZS on marmatite was investigated by a variety of techniques,including adsorption measurements,Fourier transform infrared(FTIR),X-ray photoelectron spectroscopic(XPS)analysis,and time of flight secondary ion mass spectrometry(ToF-SIMS).Results of adsorption tests and FTIR reveal that ZS adsorbed on marmatite surface and impeded the subsequent adsorption of butyl xanthate(BX).The results of XPS and ToF-SIMS indicate that the ZnO_(2)^(3-)released by ZS could be chemisorbed on the marmatite surface and depress marmatite flotation.

The Distortion of Energy Deposit Distribution of (12)～C Ions in Water

The transport process of 12C ions in water was studied with SRIM code and Geant4 toolkit. The SRIM results indicate that the transverse diffusion of 12C ion beam causes distortion of energy deposit along the beam direction. The distortion becomes more notable as the transverse diffusion increases. The simulation results of Geant4 indicate that the influence of secondary fragments on energy deposit distribution would be the main factor causing the distortion in higher energy range. In the region adjacent to the beam line where the contribution from 12C ions domi- nates, the contributions from secondary fragments are ignorable. The further from the beam axis the region locates, the larger the contributions from secondary fragments, until the contributions from secondary fragments are ignorable. The further from the beam axis the region locates, the larger the contributions from secondary fragments, until the contributions from secondary frag- ments exceed that of 12C. Among all the secondary fragments, the contributions of H, He and B ions are mostly notable. It is also found that some positron-emitting secondary fragments could be very useful for position emitting tomography （PET）.

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.

Ion Nonthermality Induced Nonlinear Dust Acoustic Wave Propagation in a Complex Plasma in Presence of Weak Secondary Electron Emission from Dust Grains

In this paper we have investigated the effect of ion nonthermality on nonlinear dust acoustic wave propagation in a complex plasma in presence of weak secondary electron emission from dust grains. Equilibrium dust charge in this case is negative. Dusty plasma under our consideration consists of inertialess nonthermal ions, Boltzman distributed primary and secondary electrons and negatively charged inertial dust grains. Both adiabatic and nonadiabatic dust charge variations have been taken into account. Our analysis shows that in case of adiabatic dust charge variation, at a fixed non-zero ion nonthermality increasing secondary electron emission decreases amplitude and increases width of the rarefied dust acoustic soliton whereas for a fixed secondary electron yield increasing ion nonthermality increases amplitude and decreases width of such rarefied dust acoustic soliton. Thus shape of the soliton may be retained if strength of both the secondary electron yield and the ion nonthermality are increased. Nonadiabatic dust charge variation shows that, at fixed non-zero ion nonthermality, increasing secondary electron emission suppresses oscillation of oscillatory dust acoustic shock at weak nonadiabaticity and pronounces monotonicity of monotonic dust acoustic shock at strong nonadiabaticity. On the other hand at a fixed value of the secondary electron yield, increasing ion nonthermality enhances oscillation of oscillatory dust acoustic shock at weak nonadiabaticity and reduces monotonicity of monotonic dust acoustic shock at strong nonadiabaticity. Thus nature of dust acoustic shock may also remain unchanged if both secondary electron yield and ion nonthermality are increased.

Feedback model of secondary electron emission in DC gas discharge plasmas

Feedback is said to exist in any amplifier when the fraction of output power in fed back as an input.Similarly,in gaseous discharge ions that incident on the cathode act as a natural feedback element to stabilize and self sustain the discharge.The present investigation is intended to emphasize the feedback nature of ions that emits secondary electrons（SEs）from the cathode surface in DC gas discharges.The average number of SEs emitted per incident ion and non ionic species（energetic neutrals,metastables and photons）which results from ion is defined as effective secondary electronemission coefficient（ESEEC,Eg）.In this study,we derive an analytic expression that corroborates the relation betweenEg and power influx by ion to the cathode based on the feedback theory of an amplifier.In addition,experimentally,we confirmed the typical positive feedback nature of SEEfrom the cathode in argon DC glow discharges.The experiment is done for three different cathode material of same dimension（tungsten（W）,copper（Cu）and brass）under identical discharge conditions（pressure：0.45 mbar,cathode bias：-600 V,discharge gab：15 cm and operating gas：argon）.Further,we found that theEg value of these cathode material controls the amount of feedback power given by ions.The difference in feedback leads different final output i.e the power carried by ion at cathode（Pi C￠∣）.The experimentally obtained value of Pi C￠∣is 4.28 W,6.87 W and9.26 W respectively for W,Cu and brass.In addition,the present investigation reveals that the amount of feedback power in a DC gas discharges not only affect the fraction of power fed back to the cathode but also the entire characteristics of the discharge.

Impact of Winter Transit Air Masses on the Sources and Composition Characteristics of Atmospheric Pollution in Hengyang

Through the integration and analysis platform of particulate matter components,a preliminary comparison was conducted on the pollution contribution of the three winter transit air masses in December to environmental quality,and the changes and related relationships of water-soluble ions and particulate matter elements were analyzed.The results showed that winter transit air masses had a significant impact on the air quality in Hengyang.In the quantitative comparison of the primary pollutant contribution during the transit period of air masses,local sources and transit sources each accounted for half,and the impact of transit source on ambient air quality was much greater than that of seasonal base increase.Fine particulate matter was closely related to secondary ions,and particulate matter was closely related to primary ions.The transit of air masses promoted the improvement of secondary ion conversion rate,and the unit increment of fine particulate matter was greater than that of particulate matter.During the transit period,the mass concentrations of most water-soluble ions and most particulate matter elements maintained synchronous growth,with a superimposed effect.The composition ratio of organic carbon and nitrate ions increased,while the composition ratio of ammonia and sulfate ions decreased.Both disposable ions and secondary conversions in the composition of PM_(2.5)had increases and decreases.The high conversion rate of nitrate and the high composition ratio of ammonia radical in Hengyang indicated that transportation source factors had a significant impact on the local environmental quality of Hengyang.

膜滤工艺中添加Fe^(2+)及在不同干燥工艺条件下对牛乳胶束酪蛋白的结构及功能性质的影响

利用膜滤工艺从脱脂鲜牛乳中制备胶束型酪蛋白,膜滤过程中添加不同浓度的Fe^(2+)水洗液,利用冷冻干燥及喷雾干燥制备出胶束酪蛋白浓缩物粉末,分析样品结构、吸油性、溶解性、乳化性、浊度及热稳定性等相关性质的变化。结果表明,不同干燥工艺及Fe^(2+)添加均对酪蛋白胶束二级结构产生了较显著的影响,其溶解性变化不大;在喷干工艺下,加入Fe^(2+)会使胶束酪蛋白热稳定性增加、浊度上升,改善了乳化性及乳化稳定性,增强吸油性;在冻干工艺下,加入Fe^(2+)同样会使胶束酪蛋白热稳定性增加、浊度上升,但是其吸油能力减小,乳化活力增大,添加0.1 mg/L Fe^(2+)时胶束酪蛋白乳化活力最佳。相关研究结果可为胶束酪蛋白食品开发提供参考依据。

新疆汉代羊毛织物染料的飞行时间二次离子质谱表征

汉代女性干尸着鲜艳的红-蓝-浅黄三色羊毛纤维编制的华丽服饰,本研究以织物片段作为研究样本,主要采用飞行时间二次离子质谱(TOF-SIMS)法对其染料进行表征。离子成像与高质量分辨数据显示:红色纤维表面产生汞同位素离子(^(202)Hg+和^(199)Hg+)、汞-硫离子(HgS^(+),m/z 234)、硫同位素离子(^(32)S−和^(34)S−)等,指示其染料属于天然无机矿物朱砂(HgS);蓝色纤维则出现目标化合物的准分子离子m/z 263([M+H]^(+)),以及合理的碎片离子系列,如m/z 235(C_(15)H_(11)N_(2)O^(+))和m/z 247(C_(16)H_(11)N_(2)O^(+))等,指示其呈色来自经典天然植物有机染料靛蓝(C_(16)H_(10)N_(2)O_(2),分子质量262.0742);浅黄纤维未检出有机染料(如姜黄)或无机染料(如铁黄),其呈色可能是白色羊毛自然老化陈旧所致。本工作表明,擅长微区原位与超高灵敏度检测的TOF-SIMS法既适用于有机染料分析,也适用于无机染料分析,该方法有望在考古和博物馆馆藏相关研究中获得广泛应用。

非均匀GaAs/AlGaAs量子阱红外探测器材料表征和器件性能研究

本文利用分子束外延(MBE)技术成功生长了GaAs/AlGaAs非均匀量子阱红外探测器材料,并对相关微结构作了细致表征。分析比较了非均匀量子阱结构和常规量子阱红外探测器性能差异,并对比研究了不同势阱宽度下非均匀量子阱红外探测器的性能变化。通过高分辨透射电子显微镜(HRTEM)结合能谱仪(EDS)对非均匀量子阱红外探测器材料微结构进行了分析,并利用二次离子质谱仪(SIMS)对非均匀势阱掺杂进行了表征。结果表明,该量子阱外延材料晶体质量很好,量子阱结构和掺杂浓度也与设计值符合较好。对于非均匀量子阱红外探测器,通过改变每个阱的掺杂浓度和势垒宽度,可以改变量子阱电场分布,而与传统的均匀量子阱红外探测器相比,其暗电流显著下降(约一个数量级)。在不同阱宽下,非均匀量子阱的跃迁模式发生改变,束缚态到准束缚态跃迁模式下(B-QB)的器件具有较高的黑体响应率以及较低的暗电流。

异质双碳源对LiMn_(0.8)Fe_(0.2)PO_(4)复合材料电化学性能的影响

采用水基流变相辅助的固相法,以异质碳蔗糖和石墨为碳源,合成了LiMn_(0.8)Fe_(0.2)PO_(4)/C复合材料,研究了不同石墨加入方式对所制复合材料电化学性能的影响,并对所制备的LiMn_(0.8)Fe_(0.2)PO_(4)/C复合材料进行了X射线衍射(XRD)、N_(2)吸附-脱附测试、扫描电子显微镜(SEM)、透射电子显微镜(TEM)等表征。结果表明,不同石墨包覆工艺对材料结构和电化学性能具有显著影响。前驱体煅烧后再加入石墨获得的样品纯度高,形貌呈均一的椭圆形,在0.1C下的放电比容量为149 mAh·g^(-1),达到其理论比容量的87%;在5C下最大的放电比容量为133 mAh·g^(-1);在2C倍率下经过300次循环后比容量维持在127 mAh·g^(-1),衰减率仅为1.9%,表现出了优良的循环稳定性。

基于原位液相飞行时间二次离子质谱的电化学固液界面研究

电化学界面是能源转换与存储、生物化学、传感器和腐蚀等领域的核心,研究电化学界面结构与性能的关系一直是电化学和化学测量学的热点与难点。本文重点介绍了基于高真空兼容微流控装置的原位液相飞行时间二次离子质谱(ToF-SIMS)技术的原理、特性,及其在电化学固液界面实时、原位探测方面的研究进展。随着微流控装置的进一步创新以及ToF-SIMS仪器的不断发展,原位液相ToF-SIMS将为电催化、电池等领域的复杂电化学固液界面研究提供重要手段。

基于质谱的单细胞分析技术研究新进展

细胞是生物体最基本的结构和功能单位。近年来,人们对细胞异质性的关注越来越多。为了分析细胞的这种异质性,避免单细胞信息被群体细胞的平均值所淹没,单细胞分析技术不断发展起来。由于单细胞的体积小,内含物质含量低且种类繁多,某些物质在细胞内的变化迅速,分析过程中不同物质之间相互干扰,造成了单细胞分析极具挑战性。基于质谱的单细胞分析技术具有通用性强、无需标记、高灵敏度、高分辨率、高选择性的优点,已逐渐在单细胞分析技术中脱颖而出,成为单细胞分析的理想工具。本文系统地总结了近5年来基于质谱的单细胞分析技术的最新进展,包括电喷雾电离质谱、激光解吸电离质谱、二次离子质谱、电感耦合等离子体质谱,并对未来的研究和技术方向进行展望,希望为单细胞质谱分析技术的研究提供参考。