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Atmosphere, Volume 7, Issue 4 (April 2016) – 13 articles

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1584 KiB  
Review
Review on the Projections of Future Storminess over the North Atlantic European Region
by Tina Mölter, Dirk Schindler, Axel Tim Albrecht and Ulrich Kohnle
Atmosphere 2016, 7(4), 60; https://doi.org/10.3390/atmos7040060 - 22 Apr 2016
Cited by 53 | Viewed by 9876
Abstract
This is an overview of the results from previously published climate modeling studies reporting on projected aspects of future storminess over the North Atlantic European region (NAER) in the period 2020–2190. Changes in storminess are summarized for seven subregions in the study area [...] Read more.
This is an overview of the results from previously published climate modeling studies reporting on projected aspects of future storminess over the North Atlantic European region (NAER) in the period 2020–2190. Changes in storminess are summarized for seven subregions in the study area and rated by a categorical evaluation scheme that takes into account emission scenarios and modeling complexity in the reviewed studies. Although many of the reviewed studies reported an increase in the intensity of high-impact wind speed and extreme cyclone frequency in the second half of the 21st century, the projections of aspects of future storminess over the NAER differed regionally. There is broad consensus that the frequency and intensity of storms, cyclones, and high-impact wind speed will increase over Central and Western Europe, and these changes will probably have the potential to produce more damage. In contrast, future extratropical storminess over Southern Europe is very likely to decrease. For Northern and Eastern Europe the results of the evaluation are inconclusive, because there is an indication of increasing as well as decreasing development of the evaluated aspects of future storminess. Concerning the storm track, we found indications of a likely north- and eastward shift in most assessed studies. Results from three studies suggest a northeastward shift of the North Atlantic Oscillation. Full article
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3130 KiB  
Article
Coherent Momentum Exchange above and within a Scots Pine Forest
by Manuel Mohr and Dirk Schindler
Atmosphere 2016, 7(4), 61; https://doi.org/10.3390/atmos7040061 - 21 Apr 2016
Cited by 9 | Viewed by 5460
Abstract
Biorthogonal decomposition (BOD) is used to detect and study synchronous coherent structures occurring at multiple levels in the vertical momentum flux (u′w′) within and above a planted Scots pine forest during a 12-week continuous measurement period. In this study, the presented method allowed [...] Read more.
Biorthogonal decomposition (BOD) is used to detect and study synchronous coherent structures occurring at multiple levels in the vertical momentum flux (u′w′) within and above a planted Scots pine forest during a 12-week continuous measurement period. In this study, the presented method allowed for the simultaneous detection and quantification of the number of coherent structures (N), their duration (D) and separation (S) at five measurement heights (z1–z5) covering the range z1/h = 0.11 to z5/h = 1.67, with h being the mean stand height at the measurement site. Results presented for five different exchange regimes (C1–C5) and for four different atmospheric stability conditions (stable, transition to stable, near-neutral, forced convection) demonstrate that during the measurement period, above-canopy momentum flux was only to a limited extent involved in the evolution of spatiotemporal momentum flux patterns found within the below-canopy space. Fully-coupled turbulent momentum exchange over the investigated height range occurred during 19% of all analyzed half-hourly datasets. Across the analyzed exchange regimes, the median contribution of strong sweeps and ejections to total momentum transfer above the canopy varied between 30% and 39% while covering 28%–32% of the time. In the below-canopy space, the contribution of coherent structures varied between 19% and 21% while covering the same amount of time. This suggests that momentum transfer through synchronous coherent structures is very efficient above the forest canopy, but attenuated in the below-canopy space. Since the majority of the presented results agrees well with the results from previous studies that analyzed coherent structures at single levels, the BOD is a promising tool for the consistent investigation of synchronous coherent structures at multiple measurement heights. Full article
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10500 KiB  
Article
Prediction of a Visible Plume from a Dry and Wet Combined Cooling Tower and Its Mechanism of Abatement
by Kazutaka Takata, Takenobu Michioka and Ryoichi Kurose
Atmosphere 2016, 7(4), 59; https://doi.org/10.3390/atmos7040059 - 20 Apr 2016
Cited by 12 | Viewed by 8408
Abstract
Heated moist air from a cooling tower forms a visible plume and needs to be predicted, not only for the performance design of the cooling tower, but also for environmental impact assessments. In this study, a computational fluid dynamics analysis is conducted to [...] Read more.
Heated moist air from a cooling tower forms a visible plume and needs to be predicted, not only for the performance design of the cooling tower, but also for environmental impact assessments. In this study, a computational fluid dynamics analysis is conducted to predict the scale of a visible plume rising from a cross flow cooling tower with mechanical draft (provided by a rotating fan). The results of computational fluid dynamics analysis are verified by comparing predictions with an actual observed plume. The results show that the predicted visible plume represents the observed plume in an error range of 15%–20%, which is permissible for designing a cooling tower. Additionally, the mixing condition of heated dry air and moist air under dry and wet combined operation is examined, and the condition is thought to affect the scale of the visible plume. It is found that, in the case of a mechanical-draft cooling tower, the fan has a mixing function which performs the complete mixing of wet and dry air, and this suggests that the generation of the plume can be determined by the intersection of the operation line and saturation line. Additionally, the effect of external wind on the scale of the visible plume is large, especially for dry and wet combined operation. Full article
(This article belongs to the Special Issue Air Pollution in the Asia-Pacific Region)
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1926 KiB  
Article
Wintertime Residential Biomass Burning in Las Vegas, Nevada; Marker Components and Apportionment Methods
by Steven G. Brown, Taehyoung Lee, Paul T. Roberts and Jeffrey L. Collett
Atmosphere 2016, 7(4), 58; https://doi.org/10.3390/atmos7040058 - 19 Apr 2016
Cited by 19 | Viewed by 5281
Abstract
We characterized residential biomass burning contributions to fine particle concentrations via multiple methods at Fyfe Elementary School in Las Vegas, Nevada, during January 2008: with levoglucosan on quartz fiber filters; with water soluble potassium (K+) measured using a particle-into-liquid system with [...] Read more.
We characterized residential biomass burning contributions to fine particle concentrations via multiple methods at Fyfe Elementary School in Las Vegas, Nevada, during January 2008: with levoglucosan on quartz fiber filters; with water soluble potassium (K+) measured using a particle-into-liquid system with ion chromatography (PILS-IC); and with the fragment C2H4O2+ from an Aerodyne High Resolution Aerosol Mass Spectrometer (HR-AMS). A Magee Scientific Aethalometer was also used to determine aerosol absorption at the UV (370 nm) and black carbon (BC, 880 nm) channels, where UV-BC difference is indicative of biomass burning (BB). Levoglucosan and AMS C2H4O2+ measurements were strongly correlated (r2 = 0.92); K+ correlated well with C2H4O2+ (r2 = 0.86) during the evening but not during other times. While K+ may be an indicator of BB, it is not necessarily a unique tracer, as non-BB sources appear to contribute significantly to K+ and can change from day to day. Low correlation was seen between UV-BC difference and other indicators, possibly because of an overwhelming influence of freeway emissions on BC concentrations. Given the sampling location—next to a twelve-lane freeway—urban-scale biomass burning was found to be a surprisingly large source of aerosol: overnight BB organic aerosol contributed between 26% and 33% of the organic aerosol mass. Full article
(This article belongs to the Special Issue Air Quality and Source Apportionment)
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3083 KiB  
Article
Effect of Pollution Controls on Atmospheric PM2.5 Composition during Universiade in Shenzhen, China
by Nitika Dewan, Yu-Qin Wang, Yuan-Xun Zhang, Yang Zhang, Ling-Yan He, Xiao-Feng Huang and Brian J. Majestic
Atmosphere 2016, 7(4), 57; https://doi.org/10.3390/atmos7040057 - 14 Apr 2016
Cited by 13 | Viewed by 5389
Abstract
The 16th Universiade, an international multi-sport event, was hosted in Shenzhen, China from 12 to 23 August 2011. During this time, officials instituted the Pearl River Delta action plan in order to enhance the air quality of Shenzhen. To determine the effect of [...] Read more.
The 16th Universiade, an international multi-sport event, was hosted in Shenzhen, China from 12 to 23 August 2011. During this time, officials instituted the Pearl River Delta action plan in order to enhance the air quality of Shenzhen. To determine the effect of these controls, the current study examined the trace elements, water-soluble ions, and stable lead isotopic ratios in atmospheric particulate matter (PM) collected during the controlled (when the restrictions were in place) and uncontrolled periods. Fine particles (PM2.5) were collected at two sampling sites in Shenzhen: “LG”—a residential building in the Longgang District, with significant point sources around it and “PU”—Peking University Shenzhen Graduate School in the Nanshan District, with no significant point sources. Results from this study showed a significant increase in the concentrations of elements during the uncontrolled periods. For instance, samples at the LG site showed (controlled to uncontrolled periods) concentrations (in ng·m−3) of: Fe (152 to 290), As (3.65 to 8.38), Pb (9.52 to 70.8), and Zn (98.6 to 286). Similarly, samples at the PU site showed elemental concentrations (in ng·m−3) of: Fe (114 to 301), As (0.634 to 8.36), Pb (4.86 to 58.1), and Zn (29.5 to 259). Soluble Fe ranged from 7%–15% for the total measured Fe, indicating an urban source of Fe. Ambient PM2.5 collected at the PU site has an average 206Pb/204Pb ratio of 18.257 and 18.260 during controlled and uncontrolled periods, respectively. The LG site has an average 206Pb/204Pb ratio of 18.183 and 18.030 during controlled and uncontrolled periods, respectively. The 206Pb/204Pb ratios at the PU and the LG sites during the controlled and uncontrolled periods were similar, indicating a common Pb source. To characterize the sources of trace elements, principal component analysis was applied to the elements and ions. Although the relative importance of each component varied, the major sources for both sites were identified as residual oil combustion, secondary inorganic aerosols, sea spray, and combustion. The PM2.5 levels were severely decreased during the controlled period, but it is unclear if this was a result of the controls or change in meteorology. Full article
(This article belongs to the Special Issue Air Quality and Source Apportionment)
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4430 KiB  
Article
Assessment of Air Quality Status in Wuhan, China
by Jiabei Song, Wu Guang, Linjun Li and Rongbiao Xiang
Atmosphere 2016, 7(4), 56; https://doi.org/10.3390/atmos7040056 - 13 Apr 2016
Cited by 19 | Viewed by 7276
Abstract
In this study, air quality characteristics in Wuhan were assessed through descriptive statistics and Hierarchical Cluster Analysis (HCA). Results show that air quality has slightly improved over the recent years. While the NO2 concentration is still increasing, the PM10 concentration shows [...] Read more.
In this study, air quality characteristics in Wuhan were assessed through descriptive statistics and Hierarchical Cluster Analysis (HCA). Results show that air quality has slightly improved over the recent years. While the NO2 concentration is still increasing, the PM10 concentration shows a clearly downward trend with some small fluctuations. In addition, the SO2 concentration has steadily decreased since 2008. Nevertheless, the current level of air pollutants is still quite high, with the PM10 and NO2 levels exceeding the air quality standard. Seasonal variation exists consistently for all the pollutants, with the highest concentration in winter and the lowest in summer. Cluster analysis evidenced that nine urban monitoring sites could be classified into three clusters. Cluster I consists of only the LY site, which is located in the famous East Lake scenic area with the best air quality. Cluster II corresponds to three monitoring sites with heavily trafficked roads nearby, where relatively severe NO2 pollution occurred. Cluster III is comprised of the remaining five sites, characterized by PM10 and SO2 pollution. Full article
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2592 KiB  
Article
Spatio-Temporal Characteristics in the Clearness Index Derived from Global Solar Radiation Observations in Korea
by Yeonjin Jung, Hana Lee, Jaemin Kim, Youngbum Cho, Jhoon Kim and Yun Gon Lee
Atmosphere 2016, 7(4), 55; https://doi.org/10.3390/atmos7040055 - 12 Apr 2016
Cited by 12 | Viewed by 5864
Abstract
The spatio-temporal characteristics of the clearness index (KT) were investigated using daily global solar irradiance measurements (290–2800 nm) for the period of 2000–2014 at 21 sites in Korea, a complex region in East Asia with a distinct monsoon season and [...] Read more.
The spatio-temporal characteristics of the clearness index (KT) were investigated using daily global solar irradiance measurements (290–2800 nm) for the period of 2000–2014 at 21 sites in Korea, a complex region in East Asia with a distinct monsoon season and heavy aerosol loading year-round. The annual mean KT value for all sites is 0.46, with values of 0.63 and 0.25 for clear and overcast skies, respectively. The seasonal variations in monthly average KT show a minimum of 0.37 in July at all sites except for Jeju, where the value was 0.29 in January. The maximum value (KT = 0.51) is observed in October, followed by a secondary peak (KT = 0.49) during February–April. The lowest KT value (KT = 0.42) was observed at both the Seoul and Jeju sites, and the highest (KT = 0.48) in the southeastern regions. Increases in average KT exceeding 4% per decade were observed in the middle and southeastern regions, with the maximum (+8% per decade) at the Daegu site. Decreasing trends (<−4% per decade) were observed in the southwestern regions, with the maximum (−7% per decade) at the Mokpo site. Cloud amount, relative humidity, and aerosol optical depth together explained 57% of the variance in daily mean KT values. The contributions of these three variables to variations in KT are 42%, 9% and 6%, respectively. Thus, the variations in KT in Korea can be primarily attributed to the presence of clouds and water vapor, with relatively weak aerosol effects. Full article
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1520 KiB  
Article
Exposure to Particle Matters and Hazardous Volatile Organic Compounds in Selected Hot Spring Hotels in Guangdong, China
by Qiusheng He, Qi Song, Yulong Yan, Zhichun Wang, Lili Guo and Xinming Wang
Atmosphere 2016, 7(4), 54; https://doi.org/10.3390/atmos7040054 - 11 Apr 2016
Cited by 9 | Viewed by 4846
Abstract
In Guangdong province, many hot springs were exploited and developed into popular places for tourist. In addition, hotels have been set up near hot spring sites to attract people, including local citizens, to spend their spare time inside these so-called “spring hotels”. In [...] Read more.
In Guangdong province, many hot springs were exploited and developed into popular places for tourist. In addition, hotels have been set up near hot spring sites to attract people, including local citizens, to spend their spare time inside these so-called “spring hotels”. In our study, indoor air quality was investigated in four hot spring hotels in Guangdong province, China. Measured indoor pollutants included CO2, CO, PM10, PM2.5 and Volatile Organic Compounds (VOCs). As the result show, high concentrations of carbon dioxide might be attributed to poor ventilation; and the variations of indoor PM10, PM2.5 concentrations were related to occupants’ activities. Alpha-pinene and toluene were the most common VOC species in the hot spring hotels other than monocyclic aromatic hydrocarbons like Benzene, Toluene, Ethylbenzene and Xylenes (BTEX), which were at medium levels among the reported indoor pollutants. High cancer risk of benzene in the newly decorated rooms should be seriously taken into consideration in the future. Indoor to Outdoor air concentration ratios (I/O) for CO2 and VOCs were higher than 1, indicating their strong indoor sources. Negative correlations were found between indoor CO2 and all the other compounds, and VOCs were shown to be significantly correlated (p < 0.01) to each other, including aromatic hydrocarbons and mono-terpenes. For indoor and outdoor air compounds, correlation coefficients among all compounds did not show a significant correlation, which indicated that these pollutants had different sources. Principal components analysis by SPSS showed that indoor materials, inhabitants’ activities and respiration, cleaning products and outdoor sources were the main sources of indoor detected pollutants in hot spring hotels. Full article
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4296 KiB  
Article
Long-Range Transport of SO2 from Continental Asia to Northeast Asia and the Northwest Pacific Ocean: Flow Rate Estimation Using OMI Data, Surface in Situ Data, and the HYSPLIT Model
by Junsung Park, Jaeyong Ryu, Daewon Kim, Jaeho Yeo and Hanlim Lee
Atmosphere 2016, 7(4), 53; https://doi.org/10.3390/atmos7040053 - 08 Apr 2016
Cited by 10 | Viewed by 5911
Abstract
This present study suggests a method to calculate the SO2 flow rate from a source area to receptor areas on a regional scale using Ozone Monitoring Instrument (OMI) SO2 products, surface in situ SO2 data, and the hybrid single particle [...] Read more.
This present study suggests a method to calculate the SO2 flow rate from a source area to receptor areas on a regional scale using Ozone Monitoring Instrument (OMI) SO2 products, surface in situ SO2 data, and the hybrid single particle Lagrangian integrated trajectory (HYSPLIT) model. The method was implemented to calculate the SO2 flow rate from continental Asia to northeast Asia and the Northwest Pacific Ocean. For the high SO2 events when SO2 was transported from continental Asia to Japan via the Korean Peninsula on 22–24 December 2006, the long-range transported SO2 flow rates were 14.0 (21.0) Mg·h−1 OMI·gird−1 at Gangneung (Seoul) in Korea and 4.2 (5.3) Mg·h−1 OMI·gird−1 at Hiroshima (Kumamoto) in Japan. For the long-range transport of SO2 from continental Asia to the Northwest Pacific Ocean on 6–7 October 2008 (9–11 October 2006), the flow rates were 16.1 (16.2) Mg·h−1 OMI·gird−1 at Hokkaido, Japan (Vladivostok, Russia) and 5.6 (16.7) Mg·h−1 OMI·gird−1 at the Aleutian Islands, Northwest Pacific Ocean (Bering Sea). The mean rates of decrease in the SO2 flow rate per 1000 km were also calculated between continental Asia and the receptor areas. Uncertainties in the flow rate estimates were also assessed and discussed. Full article
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225 KiB  
Article
Impact of Climate Change on Natural Snow Reliability, Snowmaking Capacities, and Wind Conditions of Ski Resorts in Northeast Turkey: A Dynamical Downscaling Approach
by Osman Cenk Demiroglu, Mustafa Tufan Turp, Tugba Ozturk and Mehmet Levent Kurnaz
Atmosphere 2016, 7(4), 52; https://doi.org/10.3390/atmos7040052 - 06 Apr 2016
Cited by 27 | Viewed by 7544
Abstract
Many ski resorts worldwide are going through deteriorating snow cover conditions due to anthropogenic warming trends. As the natural and the artificially supported, i.e., technical, snow reliability of ski resorts diminish, the industry approaches a deadlock. For this reason, impact assessment studies [...] Read more.
Many ski resorts worldwide are going through deteriorating snow cover conditions due to anthropogenic warming trends. As the natural and the artificially supported, i.e., technical, snow reliability of ski resorts diminish, the industry approaches a deadlock. For this reason, impact assessment studies have become vital for understanding vulnerability of ski tourism. This study considers three resorts at one of the rapidly emerging ski destinations, Northeast Turkey, for snow reliability analyses. Initially one global circulation model is dynamically downscaled by using the regional climate model RegCM4.4 for 1971–2000 and 2021–2050 periods along the RCP4.5 greenhouse gas concentration pathway. Next, the projected climate outputs are converted into indicators of natural snow reliability, snowmaking capacity, and wind conditions. The results show an overall decline in the frequencies of naturally snow reliable days and snowmaking capacities between the two periods. Despite the decrease, only the lower altitudes of one ski resort would face the risk of losing natural snow reliability and snowmaking could still compensate for forming the base layer before the critical New Year’s week. On the other hand, adverse high wind conditions improve as to reduce the number of lift closure days at all resorts. Overall, this particular region seems to be relatively resilient against climate change. Full article
(This article belongs to the Special Issue Tourism Climatology)
7814 KiB  
Article
Influence of Trans-Boundary Air Pollution on the Urban Atmosphere in Fukuoka, Japan
by Ayako Yoshino, Akinori Takami, Kei Sato, Atsushi Shimizu, Naoki Kaneyasu, Shiro Hatakeyama, Keiichiro Hara and Masahiko Hayashi
Atmosphere 2016, 7(4), 51; https://doi.org/10.3390/atmos7040051 - 30 Mar 2016
Cited by 21 | Viewed by 7923
Abstract
To understand the influence of trans-boundary air pollution on the air quality of Fukuoka, the mass concentration and chemical composition of fine particulate matter (PM) were observed at urban (Fukuoka) and rural (Fukue Island) sites in the northern Kyushu area in Japan. Chemical [...] Read more.
To understand the influence of trans-boundary air pollution on the air quality of Fukuoka, the mass concentration and chemical composition of fine particulate matter (PM) were observed at urban (Fukuoka) and rural (Fukue Island) sites in the northern Kyushu area in Japan. Chemical composition was measured using an aerosol mass spectrometer. Organic aerosol (OA) data were analyzed by the positive matrix factorization (PMF) method. Sulfate and low-volatile oxygenated OA (LV-OOA) were dominant for all of the PM2.5 mass variations on Fukue Island, where the trans-boundary air pollution is dominant in the winter-spring season. In Fukuoka, however, sulfate accounted for the largest fraction of total chemical species under high PM2.5 mass concentrations (>35 µg·m−3), while organics and nitrate made up a large fraction under low PM2.5 (<10 µg·m−3). Under the high PM2.5 condition, LV-OOA was also dominant. This indicates that high PM2.5 mass concentrations were attributed to the long-range transport of air pollution. Although the trans-boundary air pollution prevails in the winter-spring season, high sulfate concentrations were observed in the summer of 2012. In addition to the volcanic activities and photochemical reactions, long-range, trans-boundary air pollutions are influential factors not only in winter-spring but also in summer. Full article
(This article belongs to the Special Issue Air Pollution in the Asia-Pacific Region)
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4309 KiB  
Article
Effect of Additional Structure on Effective Stack Height of Gas Dispersion in Atmosphere
by Takenobu Michioka, Koichi Sada and Kazuki Okabayashi
Atmosphere 2016, 7(4), 50; https://doi.org/10.3390/atmos7040050 - 24 Mar 2016
Cited by 1 | Viewed by 5718
Abstract
Wind-tunnel experiments were conducted to evaluate the effect of additional structure (building, sea wall and banking) on the effective stack height, which is usually used in safety analyses of nuclear power facilities in Japan. The effective stack heights were estimated with and without [...] Read more.
Wind-tunnel experiments were conducted to evaluate the effect of additional structure (building, sea wall and banking) on the effective stack height, which is usually used in safety analyses of nuclear power facilities in Japan. The effective stack heights were estimated with and without the additional structure in addition to the reactor building while varying several conditions such as the source height, the height of additional structure and the distance between the source position and the additional structure. When the source height is equivalent to the reactor building height, the additional structure enhances both the vertical and horizontal gas dispersion widths and decreases the ground gas concentration, and it means that the additional structure does not decrease the effective stack height. When the source height is larger than the reactor height, the additional structures might affect the effective stack height. As the distance between the source and the additional structure decreases, or as the height of the additional structure increases, the structure has a larger effect on the effective stack height. Full article
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3214 KiB  
Article
Seasonal Variations and Correlation Analysis of Water-Soluble Inorganic Ions in PM2.5 in Wuhan, 2013
by Ting Huang, Juan Chen, Weituo Zhao, Jixiong Cheng and Shenggao Cheng
Atmosphere 2016, 7(4), 49; https://doi.org/10.3390/atmos7040049 - 23 Mar 2016
Cited by 43 | Viewed by 6269
Abstract
Daily PM2.5 and water-soluble inorganic ions (NH4+, SO42−, NO3, Cl, Ca2+, Na+, K+, Mg2+) were collected at the Hongshan Air Monitoring Station at [...] Read more.
Daily PM2.5 and water-soluble inorganic ions (NH4+, SO42−, NO3, Cl, Ca2+, Na+, K+, Mg2+) were collected at the Hongshan Air Monitoring Station at the China University of Geosciences (Wuhan) (30°31′N, 114°23′E), Wuhan, from 1 January to 30 December 2013. A total of 52 effective PM2.5 samples were collected using medium flow membrane filter samplers, and the anionic and cationic ions were determined by ion chromatography and ICP, respectively. The results showed that the average mass concentration of the eight ions was 40.96 µg/m3, which accounted for 62% of the entire mass concentration. In addition, the order of the ion concentrations was SO42− > NO3 > NH4+ > Cl >K+ > Ca2+ > Na+ > Mg2+. The secondary inorganic species SO42−, NO3 and NH4+ were the major components of water-soluble ions in PM2.5, with a concentration of 92% of the total ions of PM2.5, and the total concentrations of the three ions in the four seasons in descending order as follows: winter, spring, autumn, and summer. NH4+ had a significant correlation with SO42− and NO3, and the highest correlation coefficients were 0.943 and 0.923 (in winter), while the minimum coefficients were 0.683 and 0.610 (in summer). The main particles were (NH4)2SO4 and NH4NO3 in PM2.5. The charge of the water-soluble ions was nearly balanced in PM2.5, and the pertinence coefficients of water-soluble anions and cations were more than 0.9. The highest pertinence coefficients were in the spring (0.9887), and the minimum was in summer (0.9459). That is, there were more complicated ions in PM2.5 in the summer. The mean value of NO3/SO42− was 0.64, indicating that stationary sources of PM2.5 had a greater contribution in Wuhan. Full article
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