Atmospheric PM2 Research Articles

Chemical Characteristics of Atmospheric PM10 and PM2.5 at a Rural Site of Lijiang City, China.

Emissions from biomass burning are very serious in Southeast Asia and South Asia in April. In order to explore the effect of long-range transport of biomass emissions from the Indochina Peninsula in Southwest China during the period of the southeast monsoon season and to find out the main pollution sources in local atmospheric PM2.5, a field campaign was conducted from 6–26 April 2011 in Lijiang, China. Twenty-four-hour PM10 and PM2.5 filter samples were collected, and inorganic ions, elements, and carbonaceous components (including organic carbon (OC) and elemental carbon (EC), polycyclic aromatic hydrocarbons (PAHs) and nitrated PAHs (NPAHs)) were measured. The monthly mean mass concentrations of particulate matter (PM) were 40.4 and 14.4 μg/m3 for PM10 and PM2.5, respectively. The monthly mean concentrations of OC and EC in PM10 were 6.2 and 1.6 μg/m3, respectively. The weekly mean concentrations of ∑PAHs and ∑NPAHs were 11.9 ng/m3 and 289 pg/m3, respectively, in atmospheric PM10 of Lijiang. The diagnostic ratios of PAH and NPAH isomers were used to analyze the sources of PAHs and NPAHs in PM10. The ratios of Benz(a)anthracene/(Chrysene+Benz(a)anthracen), Fluoranthene/(Fluoranthene+Pyrene) and Indeno(1,2,3-cd)pyrene/(Benzo(g,h,i)perylene+Indeno(1,2,3-cd)pyrene) were 0.45 ± 0.04, 0.61 ± 0.01, and 0.53 ± 0.03, respectively, indicating the contribution from coal combustion and biomass burning. The 1-nitropyrene/Pyrene (1-NP/Pyr) ratio was 0.004 ± 0.001, suggesting that the contribution to NPAHs mainly came from coal combustion. Sulfate was the most prominent inorganic ionic species, with monthly mean levels of 2.28 and 1.39 μg/m3 in PM10 and PM2.5, respectively. The monthly mean mass ratios of NO3−/SO42− were 0.40 and 0.23 in PM10 and PM2.5, respectively, indicating that the contribution of atmospheric anions from coal combustion sources was much more important than that from other sources. Based on the relatively high SO42− concentrations and low NO3−/SO42− ratios, combined with the data analysis of isomer ratios of PAHs and NPAHs, we can conclude that coal combustion, traffic, and dust were the major contributors to local atmospheric PM in Lijiang city, while biomass burning may also have contributed to local atmospheric PM in Lijiang city to some degree.

The Effects of Fireworks Discharge on Atmospheric PM2.5 Concentration in the Chinese Lunar New Year.

Discharging fireworks during the Chinese Lunar New Year celebrations is a deep-rooted custom in China. In this paper, we analyze the effect of this cultural activity on PM2.5 concentration using both ground observations and satellite data. By combining remote sensing data, the problem of uneven spatial distribution of ground monitoring has been compensated, and the research time span has been expanded. The results show that the extensive firework displays on New Year’s Eve lead to a remarkable increase in nationwide PM2.5 concentration, which were 159~223% of the average level, indicating the instantaneous effect far exceeds that of any other factor over the whole year. However, the averaged PM2.5 concentrations of the celebration period were 0.99~16.32 μg/m3 lower compared to the average values of the corresponding pre-celebration period and post-celebration period, indicating the sustained effect is not very significant. The implementation of firework prohibition policies can greatly reduce the instantaneous PM2.5 increase, but no obvious air quality improvement is observed over the entire celebration period. Combining these findings and the cultural significance of this activity, we recommend that this custom is actively maintained, using new technologies and scientific governance programs to minimize the negative effects.

Characterisation of Atmospheric Particulate Matter from Opencast Coal Mining Activities and Adjacent Communities

Standard source apportionment techniques for atmospheric particulate (PM) collected near opencast coal mines provide less accurate results, as the inorganic mineral components in the overburden and at adjacent residential locations are similar. This study explores the use of the stable carbon (C) and nitrogen (N) isotope ratios (13C/12C and 15N/14N) and thermal optical methods to differentiate sources of carbonaceous material in the atmospheric PM samples from the opencast coal mines and adjacent communities. Both techniques allow a clear distinction between atmospheric PM samples from the opencast coal mines and communities to be made, although distinguishing between the contributions of coal combustion, liquid fuel combustion and the domestic use of biomass for requires further analysis.

Influence of start-up phase of an incinerator on inorganic composition and lead isotope ratios of the atmospheric PM10

A municipal solid waste incinerator (MSWI) was installed in a peripheral area of the city of Turin. In this study, we evaluated the contribution of this plant to the massive concentration of PM10, to its chemical composition and to the distribution of the lead isotopes during the start-up phase.We assessed the inorganic composition of PM10 collected in the vicinity of the Turin incinerator by inductively coupled plasma atomic emission spectroscopy (ICP-AES), magnetic sector inductively coupled plasma mass spectrometer (SF-ICP-MS) and ion chromatography (IC). The lead isotope ratios in PM10 samples were determined by SF-ICP-MS by a method developed and optimized using experimental design approach. Element trends and data chemometric treatment evidence that the vehicular traffic, increased in this area due to the opening of the MSWI plant, and, to a lesser degree, the direct incinerator emissions influence As, Cd, Cr, Cu, Ba, Mo, Pb, Sn and Zn concentrations. As a whole, however, the element concentrations in PM10 and the Enrichment Factors (EFs) were comparable with the values reported for other urban sites and target pollutant concentrations of MSWI emissions, namely Cd, Cr, Cu and Pb, were lower than in PM10 emitted from older MSWIs. This confirms that incinerators of new installation have a lower impact on atmospheric PM10 composition thanks to stricter current legislation and up-to-date technologies. The lead isotope ratios investigation allowed to distinguish the diverse sources (crustal, vehicular traffic and MSWI) that influence lead concentration in PM10 collected near incinerator during start-up phase.

Spatiotemporal variation of ambient bioaerosols in a large and industrialized metropolis of Iran and their association with PM2.5 and meteorological factors

The presence of bioaerosols in the airborne fine particulate matters (PM2.5) has raised public concern due to their pathogenic effects on human. The objective of this study was to investigate the levels of airborne bacteria and fungi and their association with PM2.5 and meteorological parameters in Isfahan. Air samples were collected from seven different locations of Isfahan city using SKC pumps connected to glass impingers containing a buffer solution and analyzed by the cell culture method. The meteorological variables were obtained from the provincial meteorological office, and the data of atmospheric PM2.5 were taken from the Department of Environment. The highest and the lowest bacterial levels were found at station 7 (114.4 (40–254.2) CFU/m3) and station 3 (39.6 (12–67.5) CFU/m3), respectively. While, the highest and the lowest fungal levels were observed at station 5 (61.1 (22.5–117)) and station 4 (26.9 (0–50)) CFU/m3, respectively. The most predominant bacteria were Gram-positive bacilli, and that for fungi were Dematiaceous and Yeast. The microbial levels varied between various months and the mean concentration of 76 CFU/m3 for bacteria and 46 CFU/m3 for fungi were obtained. The average of airborne PM2.5 concentrations was 25 µg/m3, with mean maximum occurring in the cold season. A positive association between PM2.5 and bioaerosols levels were observed, while the correlation between PM2.5 and meteorological parameters was not significant (P < 0.05). Air temperature significantly impacted both the airborne bacterial and fungal concentration (P < 0.05). Also, there was a strong correlation between the bacteria level and wind speed (P < 0.05).

Distinct chemical and mineralogical composition of Icelandic dust compared to northern African and Asian dust

Abstract. Iceland is a highly active source of natural dust. Icelandic dust has the potential to directly affect the climate via dust–radiation interaction and indirectly via dust–cloud interaction, the snow/ice albedo effect and impacts on biogeochemical cycles. The impacts of Icelandic dust depend on its mineralogical and chemical composition. However, a lack of data has prevented an accurate assessment of the role of Icelandic dust in the Earth system. Here, we collected surface sediment samples from five major Icelandic dust hotspots. Dust aerosols were generated and suspended in atmospheric chambers, and PM10 and PM20 fractions were collected for further analysis. We found that the dust samples primarily consist of amorphous basaltic materials ranging from 8 wt % (from the Hagavatn hotspot) to 60 wt %–90 wt % (other hotspots). Samples had relatively high total Fe content (10 wt %–13 wt %). Sequential extraction of Fe to determine its chemical form shows that dithionite Fe (Fe oxides such as hematite and goethite) and ascorbate Fe (amorphous Fe) contribute respectively 1 %–6 % and 0.3 %–1.4 % to the total Fe in Icelandic dust. The magnetite fraction is 7 %–15 % of total Fe and 1 %–2 wt % of PM10, which is orders of magnitude higher than in mineral dust from northern Africa. Nevertheless, about 80 %–90% of the Fe is contained in pyroxene and amorphous glass. The initial Fe solubility (ammonium acetate extraction at pH 4.7) is from 0.08 % to 0.6 %, which is comparable to low-latitude dust such as that from northern Africa. The Fe solubility at low pH (i.e. pH 2) is significantly higher than typical low-latitude dust (up to 30 % at pH 2 after 72 h). Our results revealed the fundamental differences in composition and mineralogy of Icelandic dust from low-latitude dust. We attribute these differences to the low degree of chemical weathering, the basaltic composition of the parent sediments and glacial processes. Icelandic dust contributes to the atmospheric deposition of soluble Fe and can impact primary productivity in the North Atlantic Ocean. The distinct chemical and mineralogical composition, particularly the high magnetite content (1 wt %–2 wt %), indicates a potentially significant impact of Icelandic dust on the radiation balance in the subpolar and polar regions.

Ambient fine particulate matter aggravates atherosclerosis in apolipoprotein E knockout mice by iron overload via the hepcidin-ferroportin axis

AimsExposure to fine particulate matter (PM2.5) is correlated to atherosclerosis, but the mechanism remains largely undefined. Iron overload is a significant contributor to atherosclerosis, and iron homeostasis is highly regulated by the hepcidin-ferroportin (FPN) axis. Here we aimed to investigate the association between iron overload and PM2.5-induced atherosclerotic mice. Main methodsApolipoprotein E knockout (ApoE−/−) mice were randomly assigned to filtered air (FA group) or PM2.5 (PM2.5 group) for 3-month inhalation. Daily PM2.5 mass concentrations, serum levels of ferritin, iron, pro-atherosclerotic cytokines and lipid profiles, atherosclerotic lesion areas, hepcidin, FPN and iron depositions in atherosclerotic lesions, hepcidin, FPN mRNA and protein expressions in the aorta were detected, respectively. Key findingsThe daily average concentration of atmospheric PM2.5 was 68.2 ± 21.8 μg/m3. Serum levels of ferritin, iron, VEGF, MCP-1, IL-6, TNF-α, TC and LDL-C, atherosclerotic lesion areas, hepcidin and iron depositions in atherosclerotic lesions, hepcidin mRNA and protein expressions in the PM2.5 group were observably higher than those in the FA group. Nevertheless, FPN deposition in atherosclerotic lesions, FPN mRNA and protein expressions in the aorta of the PM2.5 group were markedly lower than those of the FA group. SignificancePM2.5 inhalation could exacerbate the formation and development of atherosclerosis in ApoE−/− mice, the potential mechanisms may be partly associated with iron overload via the hepcidin-FPN axis, as well as iron-triggered systemic inflammation and hyperlipidemia.

Characterization of nitroaromatic compounds in atmospheric particulate matter from Beijing

Nitroaromatic compounds (NACs) have received much attention as a kind of toxic and important light-absorbing components in atmospheric PM2.5. In order to clarify the chemical composition, concentration levels and sources of NACs in the atmosphere, PM2.5 samples were collected from April 2016 to April 2017 in Beijing. Selective and non-targeted analytical method based on liquid chromatography-Orbitrap MS (LC-Orbitrap MS) was used to characterize atmospheric NACs for the first time. A total of 190 NACs were quantified and semi-quantified with authentic standards or surrogates, of which 165 NACs were identified tentatively. Nitro-polyaromatic compounds (NPCs) were identified and semi-quantified for the first time, including nitronaphthol, nitroacenaphthenol, nitrofluorenol, nitroaceanthrylenol, nitropyrenol and their methyl derivatives, etc. The seasonal average concentrations of total NACs were from 10.8 in summer to 100 ng/m3 in winter, which was higher than in many other areas. Nitrophenols (NP) and nitrocatechols (NC) were the most abundant NACs species, and the proportion to total NACs were 31% and 32%, respectively. The seasonal average concentration of NPCs ranged from 1.5 in summer to 9.6 ng/m3 in winter with an annual average contribution of 12%, which cannot be ignored. In winter, the contribution of NACs to organic matter (OM) and PM2.5 were up to 2.88‰ and 1.59‰, respectively. Four major sources were assigned, coal combustion and secondary formation had the highest contribution of 35%, followed by biomass combustion (32%), dust (18%), and transportation (6%).

Oxidative potential of atmospheric PM10 at five different sites of Ahmedabad, a big city in Western India.

The current study presents the oxidative potential (OP) along with a wide range of chemical speciation of particulate matter with an aerodynamic diameter less than 10 μm (PM10) at five sites representing different environments in Ahmedabad, a big city in western India. On an average, PM10 concentrations were 116±36, 228±43, 133±29, 101±21, and 70±20μgm-3; volume-normalized OP (OPV) were 2.51±0.71, 5.62±0.68, 2.69±0.76, 2.14±0.41, and 1.55±0.51nmol DTT min-1 m-3; and mass-normalized OP (OPM) were 22±3, 25±5, 21±6, 21±2, and 22±3pmol DTT min-1 μg-1 over Bapunagar (backward residential area), Narol (industrial), Paldi (bus transport hub), Income Tax (huge running traffic) and Science City (posh residential area), respectively. Overall, OPV showed a significant linear correlation with PM10, whereas OPM showed near uniformity with increasing PM10. Although the OPM values were similar, the site-to-site variability in PM10 concentration reflects the corresponding health risks associated with PM10 exposure for the people living in these areas. Further, a noticeable temporal variation in OPM at Narol and Paldi suggests that species with diverse OPM contributed to PM10 on different days. A strong linear relationship between the ratio of OPV to the mass concentration of organic carbon (OPOC) and the ratio of m/z 43 signal to total water-soluble organic aerosols (WSOA) signals (f43) suggests that the fossil-fuel combustion derived WSOA have higher OP. Furthermore, the relationships of OP with water-soluble trace metals and brown carbon are also investigated and discussed in this paper. Nitrogenous organic compounds particularly emitted from the traffic-related sources in Paldi and Income Tax have higher OPOC than those emitted from other sources over Bapunagar, Narol, and Science City.

Bioavailability of elements in atmospheric PM2.5 during winter episodes at Central Eastern European urban background site

The analysis of bioavailability and potential risk to human health of trace and minor elements bound to atmospheric PM2.5 was carried out at an urban background site in Warsaw, Poland during a 40-day winter period. The samples were sequentially extracted into four different fractions: water soluble (F1), reducible (F2), oxidizable (F3) and residual (F4) for the chemical fractionation of 8 elements: As, Cd, K, Mn, Pb, Sb, Ti and Zn, and further analyzed using inductively coupled plasma mass spectrometry in each fraction. The average PM2.5 mass concentration of 31.81 μg/m3 (±19.73 μg/m3) was exceeding daily WHO air quality guideline, while concentrations rose up to 50–70 μg/m3 during episode days. Total concentrations of all analyzed elements were higher during the episode periods, with the highest increases for K, Pb (2 times) and Cd (1.7 times). All elements exhibited high bioavailability, as well as very high (K, Ti, Zn) and high (As, Cd, Mn, Pb, Sb) risk assessment code, with both features rising in episodic days up to 20% and more than 60%, respectively. Cancer risk for adults resulted from inhalation exposure to the most bioavailable fractions (F1 and F2) of human carcinogen As. It was higher than the precautionary criterion (1 · 10−6) and increased during the days with elevated PM2.5 levels.

Chemical compositions and the impact of sea salt in atmospheric PM1 and PM2.5 in the coastal area

The 11.5-h samples were collected at a coastal site and an urban site in the coastal area, Qingdao. PM1- and PM2.5-bound water-soluble inorganic ions (WSIIs), organic carbon (OC) and element carbon (EC) were analyzed in January and July 2019. PM2.5-bound elements were determined in July 2019. The results showed that the ∑WSIIs, OC and EC concentrations at the coastal site were significantly lower than those at the urban site, and their concentrations in winter were significantly higher than those in summer. Sea salt concentrations in PM2.5 were significantly higher than those in PM1 and were significantly correlated with the concentrations of secondary inorganic aerosol (SIA) and secondary organic carbon (SOC). The mean concentrations of total elements were 1258.35 ± 1033.43 and 1669.27 ± 808.53 ng m−3 at the coastal site and urban site, respectively. The health risk assessments for elements implied that the total non-carcinogenic risks via inhalation can be ignored and the total carcinogenic risks were within an acceptable level. Positive matrix factorization model (PMF) indicated secondary inorganic aerosols (31.13%), biomass burning (28.98%), aged sea salt (21.60%), coal combustion (10.91%) and crustal dust (7.39%) were major sources of WSIIs, OC and EC. Coal and biomass burning sources played more obvious roles at the urban site in winter but secondary inorganic aerosols and aged sea salt made more apparent contributions at the coastal site. The contribution of aged sea salt source was significantly increased from winter to summer. While the contributions of secondary inorganic aerosols, biomass burning, coal combustion and crustal dust were decreased. The concentration-weighted trajectory (CWT) model suggested that local areas from Shandong Province were important for secondary inorganic aerosols, biomass burning and coal combustion. The major source regions of aged sea salt source were the Yellow Sea, Jiangsu, Anhui and Eastern Shandong Provinces. Crustal dust was dominantly originated from Western Shandong Province.

Seasonal variations in PM10 inorganic composition in the Andean city

Particulate matter (PM) is one of the key pollutants causing health risks worldwide. While the preoccupation for increased concentrations of these particles mainly depends on their sources and thus chemical composition, some regions are yet not well investigated. In this work the composition of chemical elements of atmospheric PM10 (particles with aerodynamic diameters ≤ 10 µm), collected at the urban and suburban sites in high elevation tropical city, were chemically analysed during the dry and wet seasons of 2017–2018. A large fraction (~ 68%) of PM10 composition in Quito, Ecuador is accounted for by water-soluble ions and 16 elements analysed using UV/VIS spectrophotometer and Inductively Coupled Plasma—Optical Emission Spectroscopy (ICP-OES). Hierarchical clustering analysis was performed to study a correlation between the chemical composition of urban pollution and meteorological parameters. The suburban area displays an increase in PM10 concentrations and natural elemental markers during the dry (increased wind intensity, resuspension of soil dust) season. Meanwhile, densely urbanized area shows increased total PM10 concentrations and anthropogenic elemental markers during the wet season, which may point to the worsened combustion and traffic conditions. This might indicate the prevalence of cardiovascular and respiratory problems in motorized areas of the cities in the developing world.

Atmospheric PM2.5 blocking up autophagic flux in HUVECs via inhibiting Sntaxin-17 and LAMP2

Despite of growing evidence linking PM2.5 exposure to autophagic activity in various human cells, the functional significance of PM2.5 exposure affecting autophagy in the pathogenesis of human cardiovascular disease and the underlying molecular mechanisms remain unclear. In this study, the effects of ambient PM2.5 (with final concentration 0, 1, 5, 25 µg/mL) on the autophagic activity in human umbilical vein endothelial cells (HUVECs) were systematically studied. The results showed that the internalized PM2.5 mainly localized in the membrane-surrounded vacuoles in the cytoplasm. Compared with the negative control, dose-dependent increase of autophagosomes, puncta and protein levels of LC3-II and p62, and both dose- and time-dependent increase of AKT phosphorylation, with inversely time-dependent reduction of Beclin 1, ATG3 and ATG5 proteins, were presented in the PM2.5-treated HUVECs, indicating a clear impairment of autophagic degradation in the PM2.5-exposed HUVECs. Meanwhile, increase in lysosomes, LAMP1, proteases of CTSB and CTSD, and protein phosphorylation of ERK1/2 and TFEB was identified in the PM2.5-treated HUVECs, showing a PM2.5-mediated enhancement in lysosomal activity. A novel finding in this study is that both Sntaxin-17 and LAMP2, two key proteins involved in the control of membrane fusion between autophagosome and lysosome, were significantly decreased in the PM2.5-exposed HUVECs, suggesting that the fusion of autophagosome-lysosome was blocked up. Collectively, ambient PM2.5 exposure may block up the autophagic flux in HUVECs through inhibiting the expression of Sntaxin-17 and LAMP2. Autophagic activity in HUVECs is a useful biomarker for assessing risks of environmental factors to human cardiovascular health.

Occurrence and human exposure assessment of organophosphate esters in atmospheric PM2.5 in the Beijing-Tianjin-Hebei region, China

Organophosphate esters (OPEs) in atmospheric fine particles (PM2.5) were comprehensively investigated in the Beijing-Tianjin-Hebei (BTH) region from April 2016 to March 2017. The concentrations of Σ8OPEs in all the five sampling sites ranged from 90 to 8291 pg/m3 (mean 1148 ± 1239 pg/m3; median 756 pg/m3). The highest level (median 1067 pg/m3) was found at one of the urban sites in Beijing, followed by Tianjin (746 pg/m3) and Shijiazhuang (724 pg/m3). Tris(2-chloroethyl) phosphate (TCEP) and tri[(2R)-1-chloro-2-propyl] phosphate (TCPP) were the dominant compounds across the five sampling locations. Generally, the concentrations of chlorinated OPEs were relatively higher in summer than in winter (p < 0.05), but no significant seasonal difference was discovered for non-chlorinated individual OPEs. The concentrations of tri-n-butyl phosphate (TBP), TCEP, TCPP and triphenyl phosphate (TPP) were positively correlated with the meteorological parameters (i.e. temperature and relative humidity) (p < 0.05), indicating an evident influence of meteorological condition on OPE distribution. We observed a negative correlation (p < 0.05) between octanol-air partition coefficients (logKoa) and the ratio of PM2.5-bound OPE concentrations to total suspended particulates-bound OPE concentrations, suggesting that physicochemical properties affect the particle-size distribution of OPEs. Furthermore, the median value of cancer hazard quotients (HQs) of TCEP was higher than TBP and tris(2-ethylhexyl) phosphate (TEHP). The health risk assessment showed that HQ values for children were ~1.6 times higher than those for adults. Relatively higher health risk induced by PM2.5-bound OPEs via inhalation was found during severe hazy days than in clear days.

Low-dose combined exposure of carboxylated black carbon and heavy metal lead induced potentiation of oxidative stress, DNA damage, inflammation, and apoptosis in BEAS-2B cells

Black carbon (BC) and heavy metal lead (Pb), as typical components of atmospheric PM2.5, have been shown to cause a variety of adverse health effects. However, co-exposure to BC and Pb may induce pulmonary damage by aggravating toxicity via an unknown mechanism. This study aimed to investigate the combined toxicity of carboxylated black carbon (c-BC) and lead acetate (Pb) on human bronchial epithelial cells (BEAS-2B) at the no-observed-adverse-effect level (NOAEL). Cells were exposed to c-BC (6.25 μg/mL) and Pb (4 μg/mL) alone or their combination, and their combined toxicity was investigated by focusing on cell viability, oxidative stress, DNA damage, mitochondrial membrane potential (MMP), apoptosis, and cellular inflammation. Factorial analyses were also used to determine the potential interactions between c-BC and Pb. The results suggested that the combination of c-BC and Pb could significantly increase the production of reactive oxygen species (ROS), malondialdehyde (MDA), and lactate dehydrogenase leakage (LDH) and decrease the activities of glutathione (GSH) and superoxide dismutase (SOD). The excessive oxidative stress could increase the levels of inflammatory cytokine IL-6 and TNF-α, and induce oxidative DNA damage and dissipation of MMP. Moreover, the results also suggested that the combined group could enhance the cellular apoptotic rate and the activation of apoptotic markers like caspase-3, caspase-8, and caspase-9. The factorial analysis further demonstrated that synergistic interaction was responsible for the combined toxicity of c-BC and Pb co-exposure. Most noticeably, the co-exposure of c-BC and Pb could induce some unexpected toxicity, even beyond the known toxicities of the individual compounds in BEAS-2B cells at the NOAEL.

Wavelet periodic and compositional characteristics of atmospheric PM2.5 in a typical air pollution event at Jinzhong city, China

To investigate the contributions of atmospheric particulate matter less than 2.5 μm in aerodynamic diameter (PM2.5) to heavy air pollution events in Fen-Wei Plain, China and identify their sources, a combination of wavelet analysis and low-atomic number (Z) particle electron probe X-ray microanalysis (EPMA) was utilized in a typical haze episode lasting 10 days (from Nov. 11 to 20, 2016) at Jinzhong, an inland city adjacent to Taiyuan, the capital of Shanxi Province. A 3-layer wavelet decomposition filtration was performed using the daubechies wavelet functions (db6) and the distribution of the real wavelet transformation coefficients and variance of wavelet series for various pollutants within 240 h was plotted. Five dominant periods of PM2.5 in mass concentration were observed, peaking at 101 h, 144 h, 50–51 h, 27–28 h, and 18 h in sequence from high to low in the wavelet variance chart. They were similar to those of PM10, SO2, and CO and partially overlapped with those of NO2, but different from those of O3, implying that PM2.5 have the same sources as PM10, SO2, and CO and have complicated relations with O3 and NO2. It was further found that the chemical compositions of PM2.5 in the dominant periods made great changes compared to the non-dominant periods. The relative number abundance of elemental carbon (EC) and droplets rich in CNOS (likely the mixture of carbonaceous matter with secondary aerosols such as NH4NO3 and (NH4)2SO4/NH4HSO4) in the first and second dominant period were significantly higher than that in other periods. It is concluded that coal and biomass combustion and secondary particles are still the main contributors to the wintertime heavy air pollution events in Fen-Wei Plain, suggesting that the wavelet analysis combined with low-Z particle EPMA is useful in examination of atmospheric particulate matter's origin, evolution, and roles played in haze events.

Enhanced elemental sulfur recovery and nitrogen removal through coupling of sulfide-dependent denitrification and anammox processes during ammonium- and sulfide-laden waste stream treatment

Influence of anammox process on autotrophic denitrification was investigated in this study, during simultaneous ammonium, nitrate and sulfide treatment. Elemental sulfur production and nitrogen removal by sulfide-dependent denitrifier (S-den) and mixed culture (S-den-anammox) were compared. Accumulation of nitrite (100%) and elemental sulfur (46.3%) was achieved at pH 7.0 and 30 °C with S2O32−/NO3− ratio of 1:1 by autotrophic denitrifier. Enhanced elemental sulfur production (56.5%–99.5%) by autotrophic denitrifier was obtained after coupling with anammox process. Total nitrogen removal increased to 80.5% in mixed culture reactor, which was 72.0% in anammox reactor. N2O emission in anammox reactor was not affected (<0.5% gaseous nitrogen) after coupling with autotrophic denitrification. Therefore, this study demonstrated enhanced elemental sulfur recovery and nitrogen removal through coupling of sulfide-dependent denitrification and anammox processes, which might be a potential technology for water eutrophication and corrosion control, and atmospheric acid rain, PM2.5 and global warming control.

Seasonal Characteristics and Source Analysis of Water-soluble Inorganic Ions in PM2.5 in Suqian City

To study the seasonal pollution characteristics and sources of water-soluble inorganic ions in atmospheric PM2.5 in Suqian City, 171 samples were collected at three monitoring points, which were in the water vapor channel, from May 2017 to January 2018. The mass concentrations of PM2.5 and nine water-soluble inorganic ions were analyzed. The results showed that the annual average concentration of water-soluble inorganic ions in PM2.5 in Suqian City was (44.08±34.61) μg ·m-3, accounting for 41.8% of PM2.5. The concentrations of these species were in the order of ρ(NO3-) > ρ(SO42-) > ρ(NH4+) > ρ(ρl-) > ρ(Na+) > ρ(Ca2+) > ρ(K+) > ρ(F-) > ρ(Mg2+); NO3-, SO42-, and NH4+ accounted for 75.6% of the total water-soluble ions. The annual average ratio of ρ(NO3-) to ρ(SO42-) was 1.53±0.88, indicating that mobile sources contributed more to PM2.5 pollution. Based on the correlation analysis of NH4+ and SO42-, NO3- may exist in the form of (NH4)2 SO4, NH4HSO4, or NH4NO3. According to the principal component analysis, secondary transformation, industrial pollution, biomass burning, and dust were the major sources of water-soluble inorganic ions. PM2.5concentrations were positively related to relative humidity in winter. Water vapor transmission is more likely to promote PM2.5 accumulation in winter.

Isomerization and Degradation of Levoglucosan via the Photo-Fenton Process: Insights from Aqueous-Phase Experiments and Atmospheric Particulate Matter

So far, studies on the conversion of stereochemistry under photo-Fenton conditions and their atmospheric implication are still rare. Here, we found that the biomass burning marker, the chiral compound levoglucosan (L), undergoes oxidative degradation under photo-Fenton conditions and can be isomerized into mannosan (M) and galactosan (G) simultaneously. Among the formic acid, acetic acid, and oxalic acid in the degradation products of levoglucosan, it was found that the yield of formation of formic acid in the photo-Fenton pathway can be as high as 86%. It is worth noting that both levoglucosan and its isomers are present in the atmosphere and their concentrations are strongly correlated. At the same time, the range of their concentration ratios, L/(G + M), measured in the photo-Fenton experiments in the laboratory was found to agree well with that measured in atmospheric PM2.5 samples. However, the sources of L, G, and M in the atmosphere are complex, and the photo-Fenton reaction may be an essential pathway for the distribution of L, G, and M in the atmosphere.

Maize residue effects on PM2.5, PM10, and dust emission from agricultural land

Atmospheric particulate matter and dust from agricultural land significantly affect air quality and human health in nearby residential areas. To quantify these air pollutants, it is important to estimate the vertical atmospheric particulate matter PM2.5, PM10, and dust flux using observations and validated models. To the authors´ knowledge, this has previously not been performed for semi-humid agricultural areas in China. For this purpose, we used wind tunnel tests together with field observations and the validated WEAM simulation model to assess vertical PM2.5, PM10, and dust flux from an experimental agricultural area. Four maize residue management procedures were included in the experiments, namely, conventional tillage (CT), remaining flat residue (FR), remaining standing stubble (MS), and a combination of flat residue and standing stubble (SR). Results showed that: (1) the modified WEAM model adequately simulated the vertical PM10 and dust flux from agricultural land with the four residue managements and the vertical PM2.5 flux from soils of CT and MS; (2) the vertical PM2.5, PM10, and dust flux decrease with increase of density and height of standing maize residue >10 cm, and increase with increase height of standing maize residue <10 cm; (3) the vertical PM2.5, PM10, and dust flux decrease with increase of flat residue coverage, and the threshold coverage of flat maize residue varies linearly with the wind speed; and (4) a combination of standing and flat maize residue is needed to prevent vertical PM2.5, PM10, and dust flux at wind speed 12−24 ms−1. It can be concluded that flat or standing maize residue may reduce dust emission to the National Environment Air Quality Standard when the wind speed is <16 ms−1. A combination of flat and standing maize residue (>30 cm, denser than 5 cm, and coverage >45 %) is needed for higher wind speed. The study provides an approach to control PM2.5, PM10, and dust emission from agricultural areas and ways to better manage of crop residue.