Ions In PM2 Research Articles

Evaluating PM2.5 ionic components and source apportionment in Jinan, China from 2004 to 2008 using trajectory statistical methods

The mass concentrations and major chemical components of PM(2.5) in Jinan, Shandong Province, China from Dec. 2004 to Oct. 2008 were analyzed using backward trajectory cluster analysis in conjunction with the potential source contribution function (PSCF) model. The aim of this work was to study the inter-annual variations of mass concentrations and major chemical components of PM(2.5), evaluate the air mass flow patterns and identify the potential local and regional source areas that contributed to secondary sulfate and nitrate in PM(2.5) in Jinan. The annual mean concentrations of PM(2.5), sulfate and nitrate in 2004-2008 were almost the highest in the world. The most significant air parcels contributing to the highest mean concentrations of mass and secondary ions in PM(2.5) originated from the industrialized areas of Shandong Province. Clusters with a lower ratio of NO(3)(-)/SO(4)(2-) in PM(2.5) originated from the Yellow Sea, while a higher ratio was observed in the clusters passing through Beijing and Tianjin. PSCF modeling indicated that the provinces of Shandong, Henan, Jiangsu, Anhui and the Yellow Sea were the major potential source regions for sulfate, in agreement with the cluster analysis results. Regional and long-range transport of NH(4)NO(3) played an important role in the nitrate concentration of Jinan. By comparing the distributions of secondary sulfate and nitrate over three years, enhanced emission control management before and during the 29(th) Olympic Games led to a discernible decrease in source contributions from Beijing and its environs in 2007-2008.

Chemical composition and size distribution of wintertime aerosols in the atmosphere of Mt. Hua in central China

TSP, PM10 and size-segregated aerosols were collected at the summit (2060 m, a.s.l.) of Mt. Hua in central China during the winter of 2009, and determined for organic (OC) and elemental carbon (EC), pH of water-extracts and inorganic ions. OC in TSP and PM10 are 6.9 ± 2.9 and 5.9 ± 2.5 μg m−3, while EC in TSP and PM10 are 0.9 ± 0.6 and 0.9 ± 0.5 μg m−3, respectively. SO42−, NO3−, NH4+ and Ca2+ are major ions in PM10 with concentrations of 5.8 ± 3.7, 2.7 ± 1.6, 1.6 ± 0.9 and 1.5 ± 0.7 μg m−3, respectively. OC/EC ratios (8.2 ± 3.1 in TSP and 6.6 ± 1.8 in PM10) at the mountaintop are 2–4 times higher than those in lowland surface, suggesting an enhanced transformation of organics from gas- to solid- phase because of an increased photochemical oxidation and/or an increased condensation due to lower temperature, as well as an increased organic input from mountain plant emission. Air mass backward trajectories showed that compared with those derived from north/northwest China aerosols transported from the south contained higher concentrations of SO42− and NH4+ and lower concentrations of Ca2+. Size distributions of NH4+ and K+ presented as an accumulation mode with a peak at 0.7–1.1 μm, in contrast to Ca2+ and Mg2+, which maximized at the size 4.7–5.8 μm as a coarse mode. SO42− and NO3− showed a bimodal pattern with a large peak at the range 0.7–1.1 μm and a small peak at the size of 4.7–5.8 μm, whereas Na+ and Cl− displayed a bimodal pattern with two equivalent peaks in the fine (<2.1 μm) and coarse (≥2.1 μm) ranges. pH values of the water-extracts demonstrate that aerosols originate from southern China are more acidic than those from the north/northwest, and the particles with a diameter of 0.7–1.1 μm are most acidic.

Effect of traffic loading on particle-bound water-soluble ions and carbons collected near a busy road and at an urban site

This study examines size-resolved particle-bound water-soluble ions and carbons (element carbon (EC) and organic carbon (OC)) collected near a busy road and at an urban site. The traffic-related fine and coarse particles were collected using two manual dichotomous samplers (Dichots) equipped with Quartz filters. The PM2.5/PM2.5−10 value during rush hour (3.57) exceeded that during slack time (2.72). During weekdays and weekends, although the roadside PM2.5 concentration correlated well with traffic flow (R2= 0.91 and 0.81, respectively), the roadside PM2.5−10 concentration did not. The lowest second aerosol concentrations were observed from 19:00 to 21:00 during weekdays and weekends. The average content of total water-soluble ions in PM2.5 was 30.7% and 35.7% for weekday and weekend samples, respectively (a total average of 33.2%). In PM2.5, the content of NO− 3 (8.95-11.0%) exceeded that of SO2− 4 (7.08–8.10%) at the roadside site. Conversely, the content of PM2.5-bound SO2− 4 was higher than that of PM2.5-bound NO− 3 at the urban site. The mean content of PM2.5-bound TC was 35.8%, while that of PM2.5−10-bound TC was 15.9%. Moreover, the R2 values of traffic flow versus PM2.5-bound EC concentration on weekdays and weekends were 0.89 and 0.56, respectively, and were 0.82 and 0.38, respectively, for those of traffic flow versus PM2.5-bound OC concentration.

Diurnal variations of water-soluble ions in PM2.5 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−, SO42−, C2O42− and five cations (NH4+, 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 sum 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.

Organic nitrogen in PM&amp;lt;sub&amp;gt;2.5&amp;lt;/sub&amp;gt; aerosol at a forest site in the Southeast US

Abstract. There is growing evidence that organo-nitrogen compounds may constitute a significant fraction of the aerosol nitrogen (N) budget. However, very little is known about the abundance and origin of this aerosol fraction. In this study, the concentration of organic nitrogen (ON) and major inorganic ions in PM2.5 aerosol were measured at the Duke Forest Research Facility near Chapel Hill, NC, during January and June of 2007. A novel on-line instrument was used, which is based on the Steam Jet Aerosol Collector (SJAC) coupled to an on-line total carbon/total nitrogen analyzer and two on-line ion chromatographs. The concentration of ON was determined by tracking the difference in concentrations of total nitrogen and of inorganic nitrogen (determined as the sum of N-ammonium and N-nitrate). The time resolution of the instrument was 30 min with a detection limit for major aerosol components of ~0.1 μg m−3. Nitrogen in organic compounds contributed ~33% on average to the total nitrogen concentration in PM2.5, illustrating the importance of this aerosol component. Absolute concentrations of ON, however, were relatively low (&lt;1.0 μg m−3) with an average of 0.16 μg m−3. The absolute and relative contribution of ON to the total aerosol nitrogen budget was practically the same in January and June. In January, the concentration of ON tended to be higher during the night and early morning, while in June it tended to be higher during the late afternoon and evening. Back-trajectories and correlation with wind direction indicate that higher concentrations of ON occur in air masses originating over the continental US, while marine air masses are characterized by lower ON concentrations. The data presented in this study suggests that ON has a variety of sources, which are very difficult to quantify without information on chemical composition of this important aerosol fraction.

Composition profile of oxygenated organic compounds and inorganic ions in PM2.5 in Hong Kong

Environment context.Oxygenated organic compounds are active constituents in ambient aerosols, affecting their hygroscopic properties and other interactions with water. We have measured 29 oxygenated organic compounds, together with inorganic ions and other major aerosol constituents, in ambient samples collected under various synoptic conditions in Hong Kong. These composition profiles of water-soluble matter provide valuable data for modelling and theoretical studies of aerosol–water interactions. Abstract. This study reports a comprehensive dataset of oxygenated compounds, inorganic ions and other major aerosol constituents in fine particulate matter (2.5 μm) in the urban atmosphere of Hong Kong in periods of different synoptic weather conditions during 2003–05. The oxygenated compounds quantified include C2–C10 dicarboxylic acids, C3–C9 ketoacids and C2–C3 dicarbonyls, their combined concentrations accounting for 3.2–18.2% of water-soluble organic carbon on a carbon mass basis. Six C2 and C3 oxygenated compounds, namely oxalic acid, malonic acid, glyoxylic acid, pyruvic acid, glyoxal, and methyl glyoxal, dominate this suite of oxygenated compounds, accounting for 75% of the total quantified oxygenated species. Good correlations were observed among most of the quantified oxygenated compounds, suggesting that a relatively stable abundance distribution exists under varying synoptic conditions. These composition profiles provide a comprehensive dataset for use in modelling and theoretical studies of aerosol–water interactions, secondary aerosol formation pathways, and speciated organic mass distributions.

Characterization of PM 2.5, PM 2.5–10 and PM > 10 in ambient air, Yokohama, Japan

This study elucidated the characteristics of ambient PM 2.5, PM 2.5–10 and PM > 10 with water soluble ions, i.e., Cl −, NO 3 −, SO 4 2−, Na +, NH 4 +, K +, Mg 2+ and Ca 2+ and carbonaceous aerosol, i.e., EC and OC in above size fractions from the samples collected for the period of 2007–2008. The total numbers of PM 2.5, PM 2.5–10 and PM > 10 samples collected with MCI sampler were 91, 87 and 79, respectively. The ambient particulate samples were collected twice in a week for a period of 24 h at the roof of a three-storied building in Yokohama National University. The annual arithmetic mean concentrations of PM 2.5, PM 2.5–10 and PM > 10 were 20.6, 9.6 and 5.1 µg m − 3 , respectively. The results of the daily PM 2.5 concentrations indicated that 67% of the daily PM 2.5 exceeded USEPA National Ambient Air Quality Standards (NAAQS) (15 µg m − 3 ) while 95% in respect of WHO ambient air quality guidelines (10 µg m − 3 ). The concentrations of water soluble ions in PM 2.5, PM 2.5–10 and PM > 10 accounted for 40%, 31% and 19%, respectively. The estimation of non-sea-salt particles implies that the major sources of water soluble ions in PM 2.5 are anthropogenic. On the other hand, a large proportion of sea salt particles contributes to PM 2.5–10 and PM > 10 . Spearman correlation indicated that the concentrations of OC and EC in PM 2.5 can originate from similar type of sources. However, the concentration of OC and EC in PM 2.5–10 and PM > 10 can have multiple sources. In addition, some atmospheric reactions were also characterized in this study.

Continuous observations of water-soluble ions in PM2.5 at Mount Tai (1534 m a.s.l.) in central-eastern China

Near real-time measurements of PM2.5 ionic compositions were performed at the summit of the highest mountain in the central-eastern plains in the spring and summer of 2007 in order to characterize aerosol composition and its interaction with clouds. The average concentrations of total water soluble ions were 27.5 and 36.7 μg m−3, accounting for 44% and 62% of the PM2.5 mass concentration in the spring and summer, respectively. A diurnal pattern of SO 4 2- , NH 4 + and NO 3 - was observed in both campaigns and attributed to the upslope/downslope transport of air mass and the development of the planetary boundary layer (PBL). The average SO2 oxidation ratio (SOR) in summer was 57% (±27%), more than twice that in spring 24% (±16%); the fine nitrate oxidation ratio (NOR) was comparable in the two seasons (9 ± 6% and 11 ± 10% in summer and spring, respectively). This result indicates strong summertime production of sulfate aerosol. A principal component analysis shows that short-range and long-range transport of pollution, cloud processing, and crustal source were the main factors affecting the variability of the measured ions (and other trace gases and aerosols) at Mt. Tai. Strong indications of biomass burning were observed in summer. Cloud scavenging rates showed larger variations for different ions and in different cloud events. The elevated concentrations of the water soluble ions at Mt. Tai indicate serious aerosol pollution over the North China plain of eastern China.

Acidic gases, NH 3 and secondary inorganic ions in PM 10 during summertime in Beijing, China and their relation to air mass history

In the summers of 2002–2003, acidic gases, ammonia and water-soluble ions in PM 10 were measured in Beijing. The mean concentrations of HCl, HONO, HNO 3, SO 2 and NH 3 are 0.6, 3.6, 1.9, 14.1 and 16.6 μg m −3, respectively, and 2.2, 14.6, 19.3 and 8.9 μg m −3 for Cl - , NO 3 - , SO 4 2 - and NH 4 + in PM 10. The concentrations of secondary ions in PM 10 are found to have strong dependence on the pathway of trajectories. The most frequent southerly air flow is connected with high concentrations of secondary water-soluble ions during summertime. Other trajectories with northwest and north direction lead to lower concentrations of secondary ions. Hebei and Shandong Provinces and the Tianjin Municipality are the main source areas for sulfate as identified by Potential Source Contribution Function. This result emphasizes that the non-Beijing sources play an important role in the sulfate mass concentration in the urban atmosphere of Beijing and validates conclusions based on model calculations for the region.

Acidic gases, ammonia and water-soluble ions in PM 2.5 at a coastal site in the Pearl River Delta, China

Real-time measurements of acidic trace gases (HCl, HNO 3, HONO, and SO 2), ammonia, and water-soluble ions in PM 2.5 were conducted at Xinken, a coastal site downwind of Guangzhou, from 4 October to 4 November 2004, as part of the Pearl River Delta (PRD) intensive field campaign. The average concentrations of HCl, HONO, HNO 3, SO 2, and NH 3 are 2.8, 2.9, 6.3, 55.4, and 7.3 μg m −3, respectively, and 2.4, 7.2, 24.1, and 9.2 μg m −3 for Cl −, NO 3 −, SO 4 2−, and NH 4 + in PM 2.5. The diurnal variations of both HCl and HNO 3 showed higher concentrations during daytime and lower concentrations at night, and aerosol Cl − and NO 3 − showed an opposite diurnal patterns to HCl and HNO 3. The diurnal variation of NH 3 showed the similar pattern to that of aerosol NH 4 + with lower concentration during daytime and higher concentration at night. The average concentration of SO 2 during daytime was higher than that at night. The transportation of urban plumes to the sampling site could explain the higher concentration of SO 2 during daytime. HONO showed a clear diurnal variation with lower concentration during daytime and higher concentration at night. The HONO concentrations were positively correlated with the particle surface area concentrations, suggesting the formation of HONO through the heterogeneous conversion on particle surfaces could be significant. The ionic charge balance analysis included the cations derived from filter measurements indicates that the contribution of the cations in fine particle (PM 1.8) to the charge balance is not pronounced. The theoretical equilibrium constant ( K e) of NH 4NO 3 is higher than the observed concentration product ( K m=[NH 3]×[HNO 3]) during daytime, and lower than K m at night. This indicates that the atmospheric conditions during the sampling period did not favor the formation of NH 4NO 3 during daytime.

Influence of meteorological conditions and particulate matter on visual range impairment in Jinan, China

To understand the influence of aerosol particles and meteorological conditions on visual range in Jinan, the capital of Shandong Province, China, PM(2.5) and PM(10) samples were collected from November 2004 to September 2005. The mass concentrations of PM(2.5) and PM(10), concentrations of water-soluble ions in PM(2.5) and concentrations of black carbon (BC) in the atmosphere were analyzed. The decrease of visual range in Jinan results from the combined influence of PM(2.5), PM(10) and meteorological conditions. For the period studied, the average light extinction coefficient, b(ext), which was estimated from an equation developed by the IMPROVE network was 292 Mm(-1). Ammonium sulfate was the major contributor to visual range impairment, accounting for 41%, while ammonium nitrate, particulate organic matter (POM) and BC made comparable contributions accounting for 20%, 22% and 18%, respectively. This highlights the significance of secondary particles ((NH(4))(2)SO(4), NH(4)NO(3), POM) in visual range impairment in Jinan. The data from this study are also compared with the long-term variations of visual range in Jinan from 1961 to 2005.

PM 2.5–10, PM 2.5 and associated water-soluble inorganic species at a coastal urban site in the metropolitan region of Rio de Janeiro

The concentrations of PM 2.5−10, PM 2.5 and associated water-soluble inorganic species (WSIS) were determined in a coastal site of the metropolitan region of Rio de Janeiro, Southeastern Brazil, from October 1998 to September 1999 ( n=50). Samples were dissolved in water and analyzed for major inorganic ions. The mean (± standard deviation; median) concentrations of PM 2.5−10 and PM 2.5 were, respectively, 26 (± 16; 21) μg m −3 and 17 (± 13; 14) μg m −3. Their mean concentrations were 1.7–1.8 times higher in dry season (May–October) than in rainy season (November–April). The WSIS comprised, respectively, 34% and 28% of the PM 2.5−10 and PM 2.5 masses. Chloride, Na + and Mg 2+ were the predominant ions in PM 2.5−10, indicating a significant influence of sea-salt aerosols. In PM 2.5, SO 4 2− (∼97% nss-SO 4 2−) and NH 4 + were the most abundant ions and their equivalent concentration ratio (SO 4 2−/NH 4 + ∼1.0) suggests that they were present as (NH 4) 2SO 4 particles. The mean concentration of (NH 4) 2SO 4 was 3.4 μg m −3. The mean equivalent PM 2.5 NO 3 − concentration was eight times smaller than those of SO 4 2− and NH 4 +. The PM 2.5 NO 3 − concentration in dry season was three times higher than in rainy season, probably due to reaction of NaCl (sea salt) with HNO 3 as a result of higher levels of NO y during the dry season and/or reduced volatilization of NH 4NO 3 due to lower wintertime temperature. Chloride depletion was observed in both size ranges, although more pronouncely in PM 2.5.

Origin of trace elements and inorganic ions in PM 10 aerosols to the South of Mexico City

Measurements of trace metals and inorganic ions were carried out on PM 10 aerosols. Sampling was made in the southern section of downtown Mexico City. Samples were collected with an Andersen PM 10 high volume sampler, on glass fiber filters. The ions SO 4 2−, NO 3 −, Cl −, and NH 4 + were analyzed by ion chromatography, Na +, K +, Ca 2+ and Mg 2+ by flame atomic absorption spectroscopy and the trace metals using an atomic absorption spectrometer with a graphite furnace attachment. The results indicated that SO 4 2− was the most abundant ion, and with respect to trace metals, Pb had the highest concentration in spite of the fact that lead tetraethyl content in gasoline is prohibited by Mexican Federal Law. Pearson's correlation, applied to all data, showed a high correlation among SO 4 2−, NO 3 − and NH 4 +, indicating a common anthropogenic origin. In addition the correlation found between Na + and K + indicated a crustal origin. No correlation among the trace metals was found. The scatter plots showed a high neutralization of SO 4 2− and NO 3 − by NH 4 +, (NH 4) 2SO 4 and NH 4NO 3 were the major species formed. Enrichment factors were calculated using K as a reference and the results reflected the possible origins of the elements: crustal or anthropogenic. In order to gain a better insight into the origin of trace metals and major inorganic ions, a Principal Component Analysis was applied to the results for 10 elements and 4 ions, for the years 2003 and 2004. Sources of anthropogenic species, such as industries and vehicles are discussed.

Seasonal variation of ionic species in fine particles at Qingdao, China

Totally nine measurement campaigns for ambient particles and SO 2 have been conducted during the period of 1997–2000 in Qingdao in order to understand the characteristics of the particulate matter in coastal areas of China. The mass fractions of PM 2.5, PM 2.5−10 and PM >10 in TSP are 49%, 25% and 26%, respectively. The size distribution of particles mass concentrations in Qingdao shows bi-modal distribution. Mass fraction percentages of water-soluble ions in PM 2.5, PM 2.5−10 and PM >10 decreased from 62% to 35% and 21%. In fine particles, sulfate, nitrate and ammonium, secondary formed compounds, are major components, totally accounting for 50% of PM 2.5 mass concentration. The ratios of sulfate, chloride, ammonium and potassium in PM 2.5 for heating versus non-heating periods are 1.34, 1.80, 1.56 and 1.44, respectively. The ratio of nitrate is 3.02 and this high ratio could be caused by reduced volatilization at lower temperature. Sulfate concentrations are higher than nitrate in PM 2.5. The chemical forms of sulfate and nitrate are probably (NH 4) 2SO 4 and NH 4NO 3 and chloride depletion was observed. Backward trajectory analysis reflected possible influence of air pollutant transport to Qingdao local aerosol pollution.