Search Results (9)

A one-year observation campaign from December 2020 to December 2021 was carried out in Jinan, a city that previously suffered from severe fine particulate matter (PM_2.5) pollution. The meteorological parameters and ambient concentrations of the air pollutants were recorded, and PM_2.5 samples were collected during the campaign. The inorganic chemical compositions of the PM_2.5 samples were measured, identifying 8 water-soluble ions (WSIs) and 15 trace metals. Pollution events, including 7 dust events (DEs) and 19 secondary inorganic events (SIEs), were identified and classified. The inorganic chemical compositions of the pollution events were characterized, summarized, and concluded. The low ratio of WSIs to PM_2.5, high concentrations of Ca²⁺ and Mg²⁺, and significant increases in trace metals were the dominant characteristics of PM_2.5 during DEs. The high concentrations of SO₄²⁻, NO₃⁻, and NH₄⁺; the high ratio of secondary ions to WSIs; and the high ratio of WSIs to PM_2.5 were the dominant characteristics of PM_2.5 during SIEs. Even though, recently, the PM_2.5 pollution in Jinan has not been as severe as pollution from a dozen years ago, it still exists, just at lower frequencies and pollution levels. This investigation provides the characteristics of PM_2.5 pollution under dramatically improved conditions and various ideas for the management and control of PM_2.5 pollution. Full article

The mitigation of aerosol pollution is a great challenge in many cities in China, due to the complex sources and formation mechanism of particulate matter (PM) in different seasons. To understand the particular features of pollution in China and formulate different targeted policies, aerosol samples of PM_2.5 were collected from January to October of 2018 in Longyou. The temporal profile of the meteorological parameters and the concentrations of water-soluble inorganic ions (WSIs) and organic matter (OM) were characterized. An Aerodyne High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-TOF-AMS) was also applied to further analyze the composition of water-soluble organic carbon (WSOC). The sources of WSOC were resolved by positive matrix factorization (PMF) analysis. The origin of air parcels and potential sources of WSOC were analyzed using a backward trajectory and potential source contribution function (PSCF). Winds from the northeast dominated each sampling period, and the relative humidity did not show a significant difference. The results showed that the proportion of OM in PM_2.5 was the highest in summer and decreased in spring, autumn, and winter in turn. Four organic aerosol (OA) factors, including a hydrocarbon-like factor, a coal combustion factor, and two oxygenated OA factors, were identified in the WSOC by means of PMF analysis. The hydrocarbon-like OA (HOA) contributed the majority of the WSOC in summer, while the contribution of the coal-combustion OA (CCOA) increased significantly in winter, suggesting the presence of different sources of WSOC in different seasons. The air parcels from the north of China and Zhejiang province contributed to the CCOA in winter, while those from the marine regions in the south and southeast of China mainly contributed to the HOA during spring and summer. The weighted PSCF (WPSCF) analysis showed that the regions of east Zhejiang province were the main contributors, which means that local and regional emissions were the most probable source areas of WSOC. It implied that not only were the emissions control of both local and regional emissions important but also that the transport of pollutants needed to be sufficiently well accounted for to ensure the successful implementation of air pollution mitigation in Longyou. Full article

In order to identify the pollution characteristics and sources of PM_2.5 in Urumqi, fine particulate matter samples were collected from September 2017 to August 2018, and the water-soluble ions (WSIs), organic carbon (OC), elemental carbon (EC), polycyclic aromatic hydrocarbons (PAHs), and metal elements were analyzed. The results indicate that the annual mass concentration of PM_2.5 in Urumqi was 158.85 ± 15.11 μg/m³, with the highest seasonal average in autumn (180.49 ± 87.22 μg/m³) and the lowest in summer (148.41 ± 52.60 μg/m³). SO₄²⁻ (13.58 ± 16.4 μg/m³), NO₃⁻ (13.46 ± 17.5 μg/m³), and NH₄⁺ (10.88 ± 12.2 μg/m³) were the most abundant WSIs, and the secondary inorganic ions (SNA = SO₄²⁻ + NO₃⁻ + NH₄⁺) accounted for 87.23% of the WSIs. The NO₃⁻/SO₄²⁻ ratio indicates that the contribution of stationary sources was dominant. The annual concentrations of OC and EC were 12.00 ± 4.4 µg/m³ and 5.00 ± 3.5 µg/m³, respectively, the OC/EC ratios in winter (2.55 ± 0.7), spring (3.43 ± 1.3), and summer (3.22 ± 1.1) were greater than 2, and there was the formation of secondary organic carbon (SOC). The correlation between OC and EC in spring in Urumqi (R² = 0.53) was low. In the PM_2.5, Al and Fe were the most abundant elements. The highest mass concentration season occurred in autumn, with mass concentrations of 15.11 ± 10.1 µg/m³ and 8.33 ± 6.9 µg/m³, respectively. The enrichment factor (EF) shows that most of the metal elements come from natural sources, and the Cd element mainly comes from anthropogenic sources. PAHs with a middle molecular weight were the main ones, and the annual average annual mass concentration of the PAHs was 451.35 ng/m³. The positive matrix factor model (PMF) source analysis shows that there are five main sources of PM_2.5 in Urumqi, including crustal minerals, biomass combustion, coal combustion, vehicular transport, and secondary aerosols. The distribution percentages of these different sources were 19.2%, 10.2%, 12.1%, 8.2%, and 50.3%, respectively. Full article

We investigated water-soluble ions (WSIs) of aerosol samples collected from 2016 to 2017 in Lanzhou, a typical semi-arid and chemical-industrialized city in Northwest China. WSIs concentration was higher in the heating period (35.68 ± 19.17 μg/m³) and lower in the non-heating period (12.45 ± 4.21 μg/m³). NO₃⁻, SO₄²⁻, NH₄⁺ and Ca²⁺ were dominant WSIs. The concentration of SO₄²⁻ has decreased in recent years, while the NO₃⁻ level was increasing. WSIs concentration was affected by meteorological factors. The sulfur oxidation and nitrogen oxidation ratios (SOR and NOR) exceeded 0.1, inferring the vital contribution of secondary transformation. Meanwhile higher O₃ concentration and temperature promoted the homogeneous reaction of SO₂. Lower temperature and high relative humidity (RH) were more suitable for heterogeneous reactions of NO₂. Three-phase cluster analysis illustrated that the anthropogenic source ions and natural source ions were dominant WSIs during the heating and non-heating periods, respectively. The backward trajectory analysis and the potential source contribution function model indicated that Lanzhou was strongly influenced by the Hexi Corridor, northeastern Qinghai–Tibetan Plateau, northern Qinghai province, Inner Mongolia Plateau and its surrounding cities. This research will improve our understanding of the air quality and pollutant sources in the industrial environment. Full article

Sulfate, nitrate and ammonium (SNA) are the dominant components of water-soluble ions (WSIs) in PM2.5, which are of great significance for understanding the sources and transformation mechanisms of PM2.5. In this study, daily PM2.5 samples were collected from September 2017 to August 2018 within the Guiyang urban area and the concentrations of the major WSIs in the PM2.5 samples were characterized. The results showed that the average concentration of SNA (SO₄²⁻, NO₃⁻, NH₄⁺) was 15.01 ± 9.35 μg m⁻³, accounting for 81.05% (48.71–93.76%) of the total WSIs and 45.33% (14.25–82.43%) of the PM2.5 and their possible chemical composition in PM2.5 was (NH₄)₂SO₄ and NH₄NO₃. The highest SOR (sulfur oxidation ratio) was found in summer, which was mainly due to the higher temperature and O₃ concentrations, while the lowest NOR (nitrogen oxidation ratio) found in summer may ascribe to the volatilization of nitrates being accelerated at higher temperature. Furthermore, the nitrate formation was more obvious in NH₄⁺-rich environments so reducing NH₃ emissions could effectively control the formation of nitrate. The results of the trajectory cluster analysis suggested that air pollutants can be easily enriched over short air mass trajectories from local emission sources, affecting the chemical composition of PM2.5. Full article

As one of the biggest cities in North China, Jinan has been suffering heavy air pollution in recent decades. To better characterize the ambient particulate matter in Jinan during heavy pollution periods, we collected daily PM_2.5 (particulate matter with aerodynamic diameters equal to or less than 2.5 μm) filter samples from 15 October 2017 to 31 January 2018 and analyzed their chemical compositions (including inorganic water-soluble ions (WSIs), carbonaceous species, and inorganic elements). The daily average concentration of PM_2.5 was 83.5 μg/m³ during the sampling period. A meteorological analysis revealed that both low wind speed and high relative humidity facilitated the occurrence of high PM_2.5 pollution episodes. A chemical analysis indicated that high concentrations of water-soluble ions, carbonaceous species, and elements were observed during heavy pollution days. The major constituents of PM_2.5 in Jinan were secondary aerosol particles and organic matter based on the results of mass closure. Chemical Mass Balance (CMB) was used to track possible sources and identified that nitrate, sulfate, vehicle exhaust and coal fly ash were the main contributors to PM_2.5 during heavy pollution days in Jinan, accounting for 25.4%, 18.6%, 18.2%, and 13.3%, respectively. Full article

To clarify the aerosol optical properties under different pollution levels and their impacting factors, hourly organic carbon (OC), elemental carbon (EC), and water-soluble ion (WSI) concentrations in PM_2.5 were observed by using monitoring for aerosols and gases (MARGA) and a semicontinuous OC/EC analyzer (Model RT-4) in Wuhan from 9 to 26 January 2018. The aerosol extinction coefficient (b_ext) was reconstructed using the original Interagency Monitoring of Protected Visual Environment (IMPROVE) formula with a modification to include sea salt aerosols. A good correlation was obtained between the reconstructed b_ext and measured b_ext converted from visibility. b_ext presented a unimodal distribution on polluted days (PM_2.5 mass concentrations > 75 μg⋅m⁻³), peaking at 19:00. b_ext on clean days (PM_2.5 mass concentrations < 75 μg⋅m⁻³) did not change much during the day, while on polluted days, it increased rapidly starting at 12:00 due to the decrease of wind speed and increase of relative humidity (RH). PM_2.5 mass concentrations, the aerosol scattering coefficient (b_scat), and the aerosol extinction coefficient increased with pollution levels. The value of b_ext was 854.72 Mm⁻¹ on bad days, which was 4.86, 3.1, 2.29, and 1.28 times of that obtained on excellent, good, acceptable, and poor days, respectively. When RH < 95%, b_ext exhibited an increasing trend with RH under all pollution levels, and the higher the pollution level, the bigger the growth rate was. However, when RH > 95%, b_ext on acceptable, poor and bad days decreased, while b_ext on excellent and good days still increased. The overall b_ext in Wuhan in January was mainly contributed by NH₄NO₃ (25.2%) and organic matter (20.1%). The contributions of NH₄NO₃ and (NH₄)₂SO₄ to b_ext increased significantly with pollution levels. On bad days, NH₄NO₃ and (NH₄)₂SO₄ contributed the most to b_ext, accounting for 38.2% and 27.0%, respectively. Full article

Understanding of the characteristics of water-soluble inorganic ions (WSI) in fine particulate matter (PM_2.5) emitted during forest fires has paramount importance due to their potential effect on ecosystem acidification. Thus, we investigated the emission factors (EFs) of ten most common WSI from combustion of leaves and branches of ten dominant tree species in Chinese boreal and sub-tropical forests under smoldering and flaming combustion stages using a self-designed combustion unit. The results showed that EF of PM_2.5 was three times higher for the boreal (6.83 ± 0.67 g/kg) than the subtropical forest (1.97 ± 0.34 g/kg), and coniferous species emitted 1.5 times more PM_2.5 (5.35 ± 0.64 g/kg) than broadleaved species (3.45 ± 0.37 g/kg). EF of total WSI was 1.27 ± 0.08 g/kg for the boreal and 1.08 ± 0.07 g/kg for the subtropical forest and 1.28 ± 0.09 and 1.07 ± 0.06 g/kg for broadleaved and coniferous species, respectively. Individual ionic species also varied significantly between forest types and species within forest types, and K⁺ and Cl⁻ were the dominant ionic species in PM_2.5, accounting for 25% and 30% for the boreal forest and 23% and 27% for the subtropical forest, respectively. Emissions of NO₂⁻ and SO₄²⁻ were the lowest, accounting for 3% and 5% for the boreal forest and 4% for each of the subtropical forests, respectively. Combustion of leaves emitted significantly more ionic species (1.29 ± 0.05g/kg) than branches (1.05 ± 0.07 g/kg), and smoldering consistently emitted more ionic species (1.49 ± 0.09 g/kg) than flaming combustion (0.88 ± 0.03 g/kg). The cation to anion ratio was ≥1.0, suggesting that the particulate matter is neutral to alkalescent. As a whole, our findings demonstrate that forest fire in these regions may not contribute to ecosystem acidification despite the emission of a considerable amount of WSI during forest fires. Full article

As the new core region of the haze pollution, the terrain effect of sub-basin and water networks over the Twin-Hu Basin (THB) in the Yangtze River Middle-Reach (YRMR) had great impacts on the variations and distributions of air pollutants. In this study, trace gases (NH₃, HNO₃, and HCl), water-soluble ions (WSIs), organic carbon (OC), and elemental carbon (EC) were measured in PM_2.5 from 9 January to 27 January 2018, in Wuhan using monitoring for aerosols and gases (MARGA) and a semi-continuous OC/EC analyzer (Model RT-4). The characteristics of air pollutants during a haze episode were discussed, and the PM_2.5 sources were quantitatively analyzed on haze and non-haze days using the principal component analysis/absolute principal component scores (PCA/APCS) model. The average PM_2.5 concentration was 122.61 μg·m⁻³ on haze days, which was 2.20 times greater than it was on non-haze days. The concentrations of secondary water soluble ions (WSIs) including NO₃⁻, SO₄²⁻, and NH₄⁺ increased sharply on haze days, which accounted for 91.61% of the total WSIs and were 2.43 times larger than the values on non-haze days. The heterogeneous oxidation reactions of NO₂ and SO₂ during haze episodes were proven to be the major sources of sulfate and nitrate in PM_2.5. On haze days, the concentrations of EC, primary organic carbon (POC), and secondary organic carbon (SOC) were 1.68, 1.69, and 1.34 times larger than those on non-haze days, the CO, HNO₃, and NH₃ concentrations enhanced and relatively low SO₂, O₃, and HNO₂ levels were observed on haze days. The diurnal variations of different pollutants distinctly varied on haze days. The PM_2.5 in Wuhan primarily originated from the secondary formation, combustion, dust, industry, and vehicle exhaust sources. The source contributions of the secondary formation + combustion sources to PM_2.5 on haze days were 2.79 times larger than the level on non-haze days. The contribution of the vehicle exhaust + combustion source on haze days were 0.59 times the value on non-haze days. This description is supported by a summary of how pollutant concentrations and patterns vary in the THB compared to the variations in other pollution regions in China, which have been more completely described. Full article