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Blackwater events are frequently reported over the world and become a serious environmental problem. However, the mechanisms of blackwater occurrence are not fully understood yet. This study simulated the process of blackwater with the combined pollution in an orthogonal experiment, which had 4 factors (TOC, TP, NH4+-N, and NO3--N) and 4 levels (None, Low, Middle, and High). Results showed that the process of water condition changes was divided into two parts, which were "exogenous" and "algae-derived" blackwater, and the influence of four different pollutants on the occurrence of the blackwater was ranked as follows: TOC > TP > NO3--N > NH4+-N. With the increase of organic matter addition, the anaerobic condition in water was prolonged and the concentration of Fe2+ had a significant increase. In addition, under the None phosphorus condition, the descent rates of DO and COD in the water were reduced, and the algae bloom was obviously deferred. Moreover, the addition of organic matter or phosphorus changed the microbial community structure and led to different water processes. Particularly, only on the condition of the high content of TOC and phosphorus, the diversity of sulfate-reducing bacteria (e.g., Pseudomonas, Paludibacter, and Bacteroides) increased significantly, which accounted for 51.4%, causing the significant production of S2- in the water. Water's lack of phosphorus showed a low rate of decomposition of organic matter, which might be the result of a considerable increase in the abundance of aerobic Trichococcus and Malikia. This study shows that organic matter and phosphorus have synergistic effect on blackwater occurrence. In the treatment of blackwater, the exogenous pollutant control should reduce the discharge of organic pollutants, and endogenous control should focus on phosphorus abatement and reduce nitrogen control.

Amines in fine particles constitute a significant fraction of secondary organic aerosols and have adverse effects on air quality and human health. To understand the chemical composition, variation characteristics, and potential sources of fine particulate amines in the coastal area in northern China, field sampling and chemical analysis were conducted in coastal Qingdao in the winter of 2018 and 2019. A total of 15 major amines were identified and quantified by using an ultra-high-performance liquid chromatography coupled with mass spectrometry. The average concentration of total amines in PM

16 nitrated polycyclic aromatic hydrocarbons (NPAHs) and 5 oxygenated polycyclic aromatic hydrocarbons (OPAHs) in PM2.5 at two locations in Northern China were analyzed by Gas Chromatography-Mass Spectrometry (GC-MS). Sampling was conducted at an urban site in Shandong University in Jinan (SDU) and a suburban site in Qixingtai in Jinan (QXT) in March, June, September and December in 2016. Overall, the concentrations of NPAHs and OPAHs were higher at SDU (1.88 and 9.49 ng/m3, respectively) than QXT (1.57 and 6.90 ng/m3, respectively), and the NPAHs and OPAHs concentrations were significantly higher during the winter than the other seasons at both sites. The incremental lifetime cancer risk (ILCR) values were lower than 10−6 for all sites, seasons and age groups (ranging between 1.85E-08 and 2.56E-07), so there was no risk of carcinogenesis due to exposure to these pollutants. Total cancer risk at SDU was higher than QXT and NPAHs have the highest carcinogenic risk for adults aged from 30 to 70 years. The positive matrix factorization (PMF) results revealed that coal/biomass combustion, diesel vehicle emissions, gasoline vehicle emissions and secondary formation were the main sources of NPAHs and OPAHs at SDU and QXT. Coal/biomass combustion contributed more in spring, autumn and winter; diesel vehicle emission contributed the most in summer; secondary formation made greatest contributions in winter; the contributions of gasoline vehicle emission were similar in summer, autumn and winter. Diagnostic ratios clearly demonstrated that secondary formation is more active in winter than in other seasons, and the reactions of PAHs and OH radical were the dominant secondary formation pathway at both SDU and QXT. In addition, the potential source contribution function (PSCF) identified that the Beijing-Tianjin-Hebei region, Shandong province, Bohai Sea, Yellow Sea, Anhui province and Henan province were the main source regions of NPAHs and OPAHs in Jinan.

Short-chain chlorinated paraffins (SCCPs) were added to the Stockholm Convention on Persistent Organic Pollutants (POPs) at the eighth meeting of the conference of the parties in 2017. As a consequence, increasing environmental attention and international regulation on SCCPs is expected in the future. Inhalation uptake of particulate matter (PM) was an important exposure pathway for POPs into the human body. In the present study, a total of eighty PM2.5 samples were collected in the four seasons of the year at an urban site (Shandong University, Jinan) in Shandong province to investigate the seasonal changes of SCCPs and their inhalation exposure risks to human health. The concentrations of SCCPs ranged from 9.80 to 105 ng m−3, with the mean value of 38.7 ng m−3. The highest concentrations of SCCPs were detected in winter, while the lowest concentrations were in summer. SCCPs concentrations were positively correlated with the mass concentrations of PM2.5 (r = 0.629, p

The PM2.5 samples at an urban site (JN) and a suburban site (QXT) were simultaneously collected in a heavily polluted city in North China Plain (Jinan) from March to December in 2016, and eighteen polycyclic aromatic hydrocarbons (PAHs) were analyzed. The annual average ∑PAHs concentrations were 39.8 ± 36.6 and 23.6 ± 14.0 ng m–3 at JN and QXT, respectively, with the highest concentrations observed during winter. PHE and CHY were the two most abundant PAHs, accounting for 31.1% at JN and 34.2% at QXT. Source apportionment analyses from the results of Principal Component Analysis (PCA) revealed that coal/biomass combustion and vehicle emission were the major PAH sources in PM2.5. The ratio of LMW + MMW (LMW: low molecular weight; MMW: middle molecular weight) PAHs to ∑PAHs at JN was significantly lower (p < 0.001) than that at QXT, indicating coal/biomass burning made more significant contribution to suburban area than that to urban area. Conversely, vehicle emission worked more effectively to urban area. The total benzo[a]pyrene (BaP) equivalent concentration (BaPeq) of PAHs (gas + particle phases) was 9.66 times higher than the standard value (1.00 ng m–3) and mainly originated from PAHs in particles (93.1%) with the highest contributor of Benzo(a)pyrene (BaP, 60.8%) at the urban site of Jinan in winter. The total incremental lifetime cancer risk (ILCR) assessment suggested that all age groups may have potential health risk at JN in winter except for infant. The Concentration Weighted Trajectory (CWT) model indicated that local emission and short-distance transport were the main sources of PAHs during spring and winter, and long-range transport played a key role on PAH concentrations in summer and autumn.

Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic and mutagenic. They bounded in atmospheric fine (PM2.5) and submicron (PM1) particles severely affect human health. To characterize 18 PAHs at a background site (Mount Tai) in the heavily polluted North China Plain (NCP), PM1 and PM2.5 samples were collected in the autumn of 2014. The sampling periods were classified into clean conditions and polluted conditions according to PM2.5 concentration. Biomass burning condition was selected from polluted conditions to clarify the impact of biomass burning to PAHs concentrations. The concentrations of ∑18 PAHs were 14.5 and 24.5 ng m–3 and the contents were 515 and 607 µg g–1 in PM1 and PM2.5, respectively. Three-ring PAHs were the primary contributors to the total PAHs. The major PAHs sources at Mount Tai were pyrogenic and traffic emission. Diesel combustion played more significant role to the emission of PM1-bound PAHs, while wood burning source was more obvious for PM2.5-bound PAHs. PAHs concentrations and cancer risks were the highest during biomass burning condition compared with those during polluted and clean conditions. The lifetime accumulated cancer risk of PM1-bound PAHs was considered to be acceptable, whereas it elevated to “potential risk” (10−6) for adults (30–70 years old) exposed to PM2.5-bound PAHs. The Concentration-weighted trajectory (CWT) model indicated long-distance transport from Northwest China was the major source of PM1-bound PAHs under the clean conditions. Compare with clean conditions, PAHs were more strongly influenced by short-distance transported air masses from the South of Shandong Province under the polluted conditions.

Some derivatives of polycyclic aromatic hydrocarbons (PAHs) such as chlorinated and brominated PAHs (Cl/BrPAHs), nitrated and oxygenated PAHs (N/OPAHs) have attracted significant concern due to their high toxicity. Knowledge of the profiles, formation mechanisms, and potential sources of these toxic chemicals near the industrial complexes is essential for their pollution control and management. In this study, we monitored Cl/BrPAHs, N/OPAHs, and PAHs at 24 sampling sites near a heavily industrialized area (steel, chemical, and rubber plants) using passive air samplers during the heating period (7 December 2019 to 15 April 2020) and the non-heating period (2 June 2020 to 4 October 2020). The total average concentrations of 16 BrPAHs, 8 ClPAHs, 17 NPAHs, 6 OPAHs, and 18 PAHs during both sampling periods were 471 pg/m

Paired indoor and outdoor measurements of 16 NPAHs and 5 OPAHs in PM2.5 were conducted at urban and suburban sites during January 2016 in Jinan, China. The concentrations of both indoor and outdoor NPAHs and OPAHs were higher at the urban site compared with the suburban site. 9N-ANT (16–42%), 2+3N-FLA (15–51%), 2N-PYR (6–20%), and 1N-PYR (4–6%) were the dominant NPAHs at all sites, and 9-FO (61–81%) was the most abundant OPAHs. Solid fuel combustion, motor vehicle exhausts, and secondary generation were the main sources of the PAH derivatives in this study area. The I/O ratios of 90% of NPAHs and OPAHs at the first urban indoor site (abbreviated as URI1, Green Tree Inn) and the suburban indoor site (abbreviated as SUI, the Seven Star Hotel) were 1.00, which was likely due to cooking activities occurring near the measurement site. Measurements of outdoor 2+3N-FLA/1N-PYR revealed mainly primary emission at the urban site and secondary sources at the suburban site, the average ratios were 3.76 and 12.22, respectively. The average ratio of 2+3N-FLA/2N-PYR at all sites was 3.3, indicating that the OH-initiated reaction was the dominant secondary formation pathway. Nighttime ratios of 2+3N-FLA/1N-PYR were significantly higher than the daytime ratios at all sites. The difference was especially pronounced during heavily polluted conditions at the suburban site, which suggests that heavy pollution and nighttime conditions promote secondary production. Additionally, the cancer risk was highest in urban outdoor (abbreviated as URO) when the population expose to the level as the outdoor air in the urban. The risk suggested that adults may be at a higher cancer risk.

Fourteen nitro-PAHs and five oxy-PAHs associated with PM2.5 and PM1.0 were analyzed by GC-MS/MS at Mount Tai, China. 85% of the nitro-PAHs and 65% of oxy-PAHs were found in PM1.0. The combined concentration of nitro-PAHs in PM2.5 was highest in air masses associated with biomass burning (270.50pg/m3) compared with measurements from heavily polluted days (93.21pg/m3) and clean days (81.22pg/m3). A similar trend was also reflected in measurements of PM1.0. 9-FO, 9,10-ANQ, and 1-NALD were the most abundant oxy-PAHs in both PM2.5 and PM1.0 at Mount Tai. The concentration of 2+3N-FLA was markedly increased compared with other species on heavily polluted days and biomass burning days, and 9N-ANT was more concentrated in measurements from days with biomass burning emissions. Secondary generation of nitro-PAHs was also more active during periods with biomass burning. The main formation pathway of nitro-PAHs during the sampling campaign was through reactions with OH radicals, but NO3 radicals also played a significant role at night. The incremental lifetime cancer risk (ILCR) was highest during periods with biomass burning, indicating that biomass burning has a significant impact on human health. By analyzing the results of back trajectory clustering under different meteorological conditions, we determined that a large area of straw burning in the North China Plain (NCP) was the dominant source of nitro and oxy-PAHs at Mount Tai during the measurement campaign.

The chemical compositions in PM2.5 in metropolitan areas have obtained lots of attentions, of which concerns of airborne trace elements are relatively lacking. Here, PM2.5 samples were collected simultaneously in one year at four urban sites (Zibo (ZB), Zaozhuang (ZZ), Qingdao (QD) and Jinan (JN (Shandong University)), and a rural site (JN (Miaopu)) in Shandong province. 25 elements (Al, Na, Cl, Mg, Si, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Sr, Cd, Ba and Pb) in PM2.5 were measured by wavelength dispersive X-ray fluorescence spectrometer (WDXRF). Most trace elements (Al, Na, Cl, Mg, Si, Ca, Ti, Mn, Fe, Co, Ni, As, Se, Br, Cd, Ba and Pb) exhibited the highest levels at ZB and the lowest at QD. Meanwhile, they presented obvious seasonal variations with the highest concentrations in winter or spring and the lowest in summer. S and K were the most abundant elements in the area. In the non-crustal trace metal elements, Zn, Pb and Mn presented the highest concentrations. Positive matrix factorization (PMF) modeling revealed that secondary formation, coal combustion and industry emissions were the main sources in the region. The health risk assessments suggested that at the five sites Cd (diet) for adults, Pb and Co for children, and Mn (diet) for both adults and children (at ZB and SDU sites) had non-carcinogenic risks. As and Pb for adults and children existed carcinogenic risks, especially Pb for children. The sources of these elements with health risks were further explored. Notably, Cd, As and Pb should be paid special attention in the area due to their high concentrations in aerosol water exceeding the acceptable health risks, especially Pb.

To better understand the influence of dust storms on nitrogen polycyclic aromatic hydrocarbons (NPAHs) and oxygen polycyclic aromatic hydrocarbons (OPAHs), PM2.5 was collected using prebaked quartz filters at Shandong University, Jinan, China, in spring 2016. The concentrations of 16 NPAHs and 5 OPAHs in PM2.5 were measured using gas chromatography-mass spectrometry. The highest concentration of NPAHs was recorded during dust storm 1 (DS1; 4.62 ng m–3), which was higher than those recorded during haze (2.28 ng m–3) and on clear days (0.17 ng m–3). The concentrations of 2+3N-FLA and 9N-ANT were considerably higher during haze and dust storms. The total concentration of OPAHs was highest during haze (7.72 ng m–3) and was 2–4.2 times higher than those during DS1, dust storm 2 (DS2), dust storm 3 (DS3) (all 2.38–3.07 ng m–3) and on clear days (1.82 ng m–3). The three most abundant OPAHs were 9-fluorenone, 9,10-anthraquinone, and naphthalene-1-aldehyde during all studied periods. The 2+3N-FLA/1N-PYR ratio indicated that NPAHs were dominated by secondary generation throughout the sampling period and that dust storm days were more conducive to the secondary generation of NPAHs than were hazy days. During dust storms, NPAHs and OPAHs were influenced by long-distance transport originating in Mongolia and Inner Mongolia. NPAHs and OPAHs in PM2.5 were mainly derived from vehicle exhausts, solid fuel combustion, secondary generation, and crustal sources throughout the sampling period. The highest ∑BaPeq value (0.0928 ng m–3) was recorded during DS2. The incremental lifetime cancer risk and total risk on hazy days and the three dust storm episodes were higher than those on clear days.

There has been a significant decline in SO2, the main precursor of sulfate, in North China over the past decade due to strict sulfur removal measures, whereas the amount of photochemical oxidants such as ozone has continued to increase in this region. In this study, we examined temporal variation in the concentrations of fine sulfate in urban Ji’nan in North China from 2008 till 2015. Over this period, the sulfate concentration decreased by –3.86 ± 2.50 µg m–3 yr–1 (–10.0% yr–1), which is slower that the rate of decrease for SO2 during the same period (–11.6% yr–1). Nevertheless, the sulfur oxidation ratio and the concentrations of ozone and calcium (an indicator of dust particles) increased over this period. An analysis of the seasonal and diurnal variations in sulfate and the related parameters in 2015 indicated that the ambient sulfate concentration was largely influenced by the amount of SO2, atmospheric oxidants, aerosol loading, and meteorological conditions. A detailed investigation of the production of sulfate in eight case studies found that the observed sulfate production rate was in the range of 1.1–10.8 µg m–3 h–1. Numerical calculations revealed that SO2 oxidation by OH and H2O2 was a major contributor to sulfate production during the daytime in warm seasons. At all times of the day in cold seasons and at nighttime in warm seasons, the heterogeneous SO2 reaction on aerosol surfaces contributed 30.1%–65.7% of the sulfate production. The increasing amount of ozone and dust particles in this region, which are associated with photochemical pollution and urban dust emissions, are responsible for the slower decrease in sulfate concentration. Therefore, photochemical smog and urban dust should receive adequate attention in order to mitigate the sulfate pollution.

Carbonyl compounds, an important category of volatile organic compounds (VOCs), play important roles in ozone (O 3 ) formation and atmospheric chemistry. To better understand the characteristics and sources of carbonyl compounds and their effects on O 3 formation, C 1 -C 8 carbonyls were measured at Mount Tai, the highest mountain in the North China Plain (NCP), in summer 2014. Acetone (3.57 ± 0.55 ppbv), formaldehyde (3.48 ± 0.98 ppbv) and acetaldehyde (1.27 ± 0.78 ppbv) are the three most abundant species, comprising as high as 90% of the total observed compounds. Isovaleraldehyde (0.37 ± 0.17 ppbv) presents another important carbonyl compound despite its high reactivity. Comparison with the observations available in China highlights the serious situation of carbonyls pollution in the NCP region. The sources of carbonyls are dominated by photo-oxidation of VOCs during the daytime and regional transport at night. Secondary sources from oxidation of hydrocarbons contribute on average 44% of formaldehyde, 31% of acetone, 85% of acetaldehyde, 78% of benzaldehyde, and 84% of isovaleraldehyde, demonstrating the dominant role of secondary formation in the ambient carbonyl levels. Formaldehyde, acetaldehyde and isovaleraldehyde are the most important contributors to the OH reactivity and O 3 production among the measured carbonyls. This study shows that carbonyl compounds contribute significantly to the photochemical pollution in the NCP region and hence understanding their sources and characteristics is essential for developing the science-based O 3 pollution control strategies.

International audience; To explore the spatial and chemical characteristics of PM2.5 pollution and the influence of fireworks displays on PM2.5 and its chemical components in rural areas in Central and East China, PM2.5 samples were collected at three rural sites and one suburban site in Henan and Shandong provinces during the 2016 Chinese New Year, and the chemical composition of PM2.5, including water-soluble inorganic ions (WSIIs), organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC) and trace elements (TEs) was analysed. The concentrations of PM2.5 at the four sites were significantly higher than the Grade I national standard of 35 μg/m3, indicating serious PM2.5 pollution in rural and suburban areas. The contributions of secondary WSIIs to total WSIIs at the four sites were lower than in urban areas. The TEs in XP and LC were significantly enriched in PM2.5. A significant difference was found in the main chemical compositions of different sites. Fireworks displays directly increased the concentrations of PM2.5 and many chemicals, especially K+, Cl−, K, Cl, S, Cu and Sr, and concentrations of NO3− and NH4+ ions peaked after the fireworks period in the three rural sites, indicating the influence of firecrackers on the secondary formation of the precursors of NO2. The ratio of WSOC/OC decreased during fireworks displays, indicating the direct influence of firecrackers on water insoluble organic matter. Fireworks-related ions were a key component of the aerosol at the four sites during fireworks displays, accounting for 28–38% of the total measured species.

The relationships between polycyclic aromatic hydrocarbons (PAHs) in PM2.5 in outdoor and indoor environments of hotels were examined in Jinan, China from January 6, 2016 to January 29, 2016. The mean concentrations of ∑PAHs for all sampling sites showed the following ascending order: suburban indoor (SUI, 39.58 ng m–3), first urban indoor near a busy traffic road (URI1; 3 m, 63.26 ng m–3), suburban outdoor (SUO, 67.96 ng m–3), urban outdoor (URO, 105.30 ng m–3), and second urban indoor far away from the traffic roads (URI2 > 320 m, 115.63 ng m–3). The indoor/outdoor (I/O) ratios of URI1 and SUI were all less than 1, indicating that the PAHs were mainly infiltrated from the outdoor environment. At URI2, 2-ring and some 3- and 4-ring PAHs were mainly produced indoors due to cooking, whereas the 5–7-ring PAHs were mainly infiltrated from the outdoor environment. The diagnostic ratios and principal component analysis indicated that emissions from combustion of coal, biomass, diesel fuel and gasoline were the main sources of PAHs in the study area. The impacts of health risk assessment of PAHs suggested that the health risks in the outdoor environment were more severe than those in the indoor environment and the health risks in urban area were significantly higher than those in the suburban area in Jinan.

International audience; To investigate the chemical characteristics and sources of size-segregated particles in the background region, PM1.0, PM2.5 and PM10 samples were collected in Tuoji Island (TI) during the winter of 2014. Water-soluble inorganic ions (WSIIs) including Na+, NH4+, K+, Mg2 +, Ca2 +, Cl−, NO3− and SO42 −, organic carbon (OC) and elemental carbon (EC) and water-soluble organic carbon (WSOC) were analysed. The average mass concentrations of PM1.0, PM2.5 and PM10 were 44.5 μg/m3, 62.0 μg/m3 and 94.4 μg/m3, respectively, and particles were importantly enriched in PM1.0. Secondary WSIIs (NH4+, NO3− and SO42 −) were the most abundant species, and their contribution was highest in PM1.0. The average values of NOR and SOR were more than 0.1 in PM1.0, suggesting that secondary formation of SO42 − and NO3− from the gas precursors SO2 and NO2 occurred in PM1.0. Secondary organic carbon accounted for 62.3% in PM1.0, 61.9% in PM1.0–2.5 and 48.9% in PM2.5–10 of OC, formed mainly in the fine mode. The particles concentrations were mainly affected by air mass from the North China Plain, especially the air mass from the southwest of Shandong province, which had low speed and altitude.

Nitrated phenols are a major class of brown carbon in the atmosphere and have adverse effects on human and plants health. They are emitted from combustion sources or produced by oxidation of phenolic precursors. In this study, fine particulates, total suspended particulates, and gas-phase samples were collected in urban Jinan in winter, spring, and summer, and UHPLC-MS analysis was used to determine 8 phenolic compounds and 12 nitrated phenols in these samples. The seasonal average concentrations of total phenolic compounds and total nitrated phenols were in the ranges of 2.6–18.7 ng m−3 and 13.5–105.4 ng m−3, respectively. The concentrations of phenolic compounds and nitrated phenols were highest in winter, followed (in decreasing order) by spring, and summer. Phenol and salicylic acid were the most abundant phenolic species in both gaseous and particulate samples. 4-Nitrophenol was the most abundant nitrated phenols in particulate matters, followed by 4-nitrocatechol and 5-nitrosalicylic acid, while 4-nitrophenol and 2,4-dinitrophenol were the dominant species in the gas phase. The distributions of phenolic compounds and nitrated phenols in fine and coarse particles and in gas and particle phases were largely dependent on the aerosol size distribution, the ambient temperature, and the compound volatility. More of them were distributed in fine particles and gas-phase in summer than in spring. It was found that phenol, catechol, methyl-catechols, 4-nitrophenol, and methyl-nitrophenols mainly derived from coal combustion, while biomass burning was the main source of cresols, 2,6-dimethyl-4-nitrophenol, 4-nitrocatechol, and methyl-nitrocatechols. In addition, secondary formation contributed the largest fraction of nitrosalicylic acids and vehicle exhaust was the major source of cresols, 2,6-dimethyl-4-nitrophenol, and 4-methyl-2,6-dinitrophenol. Further correlation analysis revealed positive correlations between nitrated phenols and corresponding phenolic precursors, indicating the important roles that phenolic precursors played in the secondary formation and abundance of nitrated phenols in the atmosphere.

Eighteen polycyclic aromatic hydrocarbons (PAHs) and fourteen nitrated PAHs (NPAHs) in PM2.5 samples were collected during the 2016 Chinese New Year's holiday (CNY) at one suburban and three rural sites in Shandong and Henan Provinces. The PAH and NPAH concentrations were highest at the suburban site. The rural PAH concentrations in Qingzhou (QZ), Heze (HZ), and Liaocheng (LC) were higher than those measured at many other urban sites, indicating that PAHs pollution was notably higher in the suburban and rural sites during this festive period. Elevated PAH concentrations were observed during fireworks periods, but fireworks burning was not a significant or direct PAHs or NPAHs source based on molecular profiles and diagnostic ratios. The measured PAHs and NPAHs at the sampling sites mainly originated from coal and biomass burning. The increased concentrations during CNY's Eve may be related to behavioural changes during the period. Secondary formation of NPAHs mainly occurred via OH radical chemistry at all four sites. Fireworks burning did not increase secondary formation of NPAHs. ∑BaPeq concentrations exhibited strong correlations with PAHs concentrations, and the highest and lowest concentrations were observed in QZ and Xiping (XP), respectively. The incremental lifetime cancer risk (ILCR) was calculated to be between 10-6 and 10-4 for 1-70 years old persons, with the highest risks observed in the adult (30-70 years) and the toddler (1-6 years) groups.

Field measurements were conducted near Qingdao Port to characterize the particulate air pollutants, assess the spatial and seasonal characteristics of the pollutants, and identify the contribution from ship traffic emissions. By utilizing multiple statistical methods and data collected at two sites in Qingdao, we comprehensively explored the PM2.5 seasonal characteristics and source apportionments of different PM2.5 constituents, especially those originating from ship emissions, and identified potential source regions for samples collected in Qingdao. In this study, 118 concurrent daily PM2.5 samples were collected from August 2018 to May 2019 at a port site (QH) and a coastal background site (BG). Vanadium (V) and Nickel (Ni) are the dominant metal elements from crude oil and crude oil combustion emissions. The significant correlations between V and Ni at both sampling sites, indicating that shipping emissions have a significant impact on the port and background area. Additionally, Ni and other metals showed significant correlations at the BG site, implying Ni also emission from the land-based oil at this site. The positive matrix factorization (PMF) model identified six main sources for the PM2.5 samples in Qingdao, and they are coal combustion, industrial emissions/mineral dust, marine vessel emissions, secondary aerosols/biomass burning, sea salt/crustal emissions, and vehicle exhaust, respectively. Marine vessel emissions were the dominant contributor to PM2.5 in Qingdao during the sampling periods (25.05%). The potential source contribution function (PSCF) analysis suggested that the Yellow Sea and Jiaodong Peninsula were the major sources regions for PM2.5 in Qingdao. The Yellow Sea and Bohai Sea were the potential source regions for shipping emissions in Qingdao. Therefore, efforts to control shipping emissions should be strengthened not only at the Qingdao Port but also in surrounding ports.

The radiative absorption enhancement of ambient black carbon (BC), by light-refractive coatings of atmospheric aerosols, constitutes a large uncertainty in estimates of climate forcing. The direct measurements of radiative absorption enhancement require the experimentally-removing the coating materials in ambient BC-containing aerosols, which remains a challenge. Here, the absorption enhancement of the BC core by non-absorbing aerosol coatings was quantified using a two-step removal of both inorganic and organic matter coatings of ambient aerosols. The mass absorption cross-section (MAC) of decoated/pure atmospheric BC aerosols of 4.4±0.8m(2)g(-1) was enhanced to 9.6±1.8m(2)g(-1) at 678-nm wavelength for ambiently-coated BC aerosols at a rural Northern China site. The enhancement of MAC (EMAC) rises from 1.4±0.3 in fresh combustion emissions to ~3 for aged ambient China aerosols. The three-week high-intensity campaign observed an average EMAC of 2.25±0.55, and sulfates were primary drivers of the enhanced BC absorption.

Volatile organic compounds (VOCs) were measured at a rural site in the North China Plain during summer 2013, which focused on VOCs characteristics and impact of biomass burning. Alkanes and halocarbons made the largest contribution to the sum of the mixing ratio of each VOC compound (total VOCs). Most VOC species mixing ratios had similar day-to-day variability, indicating that the air mass at the sampling site had small local perturbation. Accumulation of pollutants due to biomass burning and advection of plumes from urbanized areas upwind had important impact on diurnal variation patterns of the VOC group. Ethylbenzene/m,p-xylene ratio and its relationship with O3 indicated that sampling site received an aged air parcel. The aromatics and alkenes were the dominant contributors to total ozone formation potential (OFP). The top 5 VOC species based on OFP were toluene, isoprene, ethene, propene and n-Hexane. During the biomass burning period, VOCs had higher OFP values, especially the aromatics and alkynes. The backward trajectories indicated that extensive transport of biomass burning from the Shandong and Hebei provinces had an important effect on VOCs pollution levels.

An analysis of 12 polycyclic aromatic hydrocarbons (PAHs) in PM2.5 (particulate matter with a diameter smaller than 2.5 microns) samples collected at Yucheng, Shandong, in June 2013 was conducted to determine the concentrations, composition, sources, and associated cancer risk. The results revealed that the average PAH concentration was higher during haze episodes (28.28 ± 8.35 ng m−3) when compared to non-haze episodes (23.68 ± 4.17 ng m−3), and diagnostic ratio and principal component analyses indicate that the predominant sources of PAHs were from fossil fuel and coal combustion, likely from vehicle emissions and industrial sources and biomass burning. Coal combustion and biomass burning contributed significantly more during haze episodes, whereas liquid fossil fuel combustion (e.g. petroleum) was the dominant contributor during the non-haze periods. In addition, back-trajectory calculations revealed that the long-distance transport of air masses from regions with industrial pollution and biomass burning contributed significantly to the concentrations of PAHs in the region. The concentration of high molecular weight PAHs (HMW-PAHs) increased from 62.3 % under non-haze conditions to 67.9 % during the haze periods. The benzo[a]pyrene-equivalent carcinogenic potency value during haze episodes was higher (7.09 ng m−3) than that during non-haze (5.64 ng m−3) periods and adults over 30 years old in the Shandong province are at an increased risk of cancer from PAHs.

Characteristics and transformation of nitrous acid (HONO) and particulate nitrite were investigated with high time-resolution field measurements at an urban site in Ji'nan, China from Nov. 2013 to Jan. 2014. During the sampling period, averages of 0.35ppbv HONO and 2.08μgm(-3) fine particulate nitrite were observed. HONO and particulate nitrite exhibited similar diurnal variation patterns but differed in the time at which concentration peaks and valleys occurred. Elevated nocturnal HONO concentration peaks were mainly associated with primary emissions from vehicle exhaust and secondary formation via heterogeneous reactions of NO2. In fresh air masses dominated by vehicle emissions, the average HONO/NOx ratio was 0.58%. The nocturnal heterogeneous reactions of NO2 contributed to about half of the elevated HONO concentration peaks, with the conversion rates in the range of 0.05% to 0.96%h(-1). Meanwhile, a large amount of particulate nitrite, which greatly exceeded the concentration of the gas-phase HONO, was also produced through the heterogeneous reactions of NO2. The large yields of particulate nitrite were facilitated by abundant ammonia and particulate cations in urban Ji'nan. Notably, in the daytime, particulate nitrite acted as a potential source of HONO, especially in conditions of low humidity and acidic aerosols, which possibly has subsequent effects on photochemistry in the boundary layer.

Seventeen polycyclic aromatic hydrocarbons (PAHs) and eight nitrated PAHs (NPAHs) in PM2.5 and conventional gaseous pollutants exhausted from 54 in-use gasoline vehicles encompassing different emission standards (China 1 to China 5) were tested on the chassis and engine dynamometric test bench. With the increase of emission standards, a decrease in the emissions of PM2.5-bound PAHs and NPAHs was detected. The emission factors (EFs) of total PAHs and NPAHs in PM2.5 emitted by the vehicles with a mileage of >100,000 km were greater than that emitted by the vehicles with driving mileage of

Daytime and nighttime PM2.5 samples were collected at a road tunnel located in Qingdao, China. The mass concentrations and chemical compositions of polycyclic aromatic hydrocarbons (PAHs), nitrated PAHs (NPAHs) and oxygenated-PAHs (OPAHs) were analysed to determine the variation characteristics and sources. The concentrations in exit were obviously higher than those of entrance in the tunnel. Fluoranthene (FLT) and Pyrene (PYR) were the most abundant PAHs, 2 + 3-nitrofluoranthene (2 + 3N-FLA), 1-nitropyrene (1N-PYR) and 2-nitropyrene (2N-PYR) were the dominant NPAHs, and 9-fluorenone (9-FO) and 9,10-anthraquinone (9,10-ANQ) were the most abundant OPAHs. The high rings (4–6 rings) PAHs accounted for over 90% of the total PM2.5-bound PAH concentrations, most of which were considered as motor vehicle emissions. Based on the diagnostics ratios and PCA results, the most important sources of PAHs and NPAHs were estimated as gasoline and diesel vehicles emissions in the tunnel. In addition, non-exhausts (such as road dust, brake line, asphalt and tires wear) also had some contributions to PAHs and NPAHs. The average emission factors were 60.98, 9.02 and 8.47 μg veh−1 km−1 for total PM2.5-bound PAHs, NPAHs and OPAHs, respectively. The emission factors of high rings (4–6 rings) PAHs were greater than those with low rings (2–3 rings). 1N-PYR had the highest emission factor in all measured NPAHs, while the emission factors for the two highest OPAHs were 9-FO and 9,10-ANQ in this tunnel.

International audience; Ambient measurements of PM2.5-bounded polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs (NPAHs), and oxy-PAHs (OPAHs) were conducted during the summer in Jinan, China, an urban site, and at Tuoji island and Mt. Tai, two background locations. 3.5 h and 11.5 h sampling intervals in daytime and nighttime were utilized to research the diurnal variations of PAHs, NPAHs, and OPAHs. The concentrations of PAHs, NPAHs, and OPAHs were highest at the urban site and lowest at the marine site. The diurnal patterns of PAHs and NPAHs at the urban and marine sites were dissimilar to those observed at the mountain site partly due to the influence of the boundary layer. Vehicle emissions at the urban site made a large contribution to high molecular weight PAHs. 1N-PYR and 7N-BaA during morning and night sampling periods in JN were relatively high. Fossil fuel combustion and biomass burning were the main sources for all three sites during the sampling periods. The air masses at the marine and mountain sites were strongly impacted by photo-degradation, and the air masses at the marine site were the most aged. Secondary formation of NPAHs was mainly initiated by OH radicals at all the three sites and was strongest at the marine site. Secondary formation was most efficient during the daytime at the urban and mountain sites and during morning periods at the marine site. The average excess cancer risk from inhalation (ECR) for 70 years' life span at the urban site was much higher than those calculated for the background sites.

Regional ozone (O3) pollution has drawn increasing attention in China over the recent decade, but the contributions from urban pollution and biogenic emissions have not been clearly elucidated. To better understand the formation of the regional O3 problem in the North China Plain (NCP), intensive field measurements of O3 and related parameters were conducted at a rural site downwind of Ji'nan, the capital city of Shandong province, in the summer of 2013. Markedly severe O3 pollution was recorded, with the O3 mixing ratios exceeding the Chinese national ambient air quality standard on 28 days (a frequency of 78%) and with a maximum hourly value of 198 ppbv. Extensive regional transport of well-processed urban plumes to the site was identified. An observation-constrained chemical box model was deployed to evaluate in situ photochemical O3 production on two episodes. The results show that the in situ formation accounted for approximately 46% of the observed O3 accumulation, while the remainder (~ 54%) was contributed by regional transport of the O3-laden urban plumes. The in situ ozone production was in a mixed controlled regime that reducing either NOx or VOCs would lead to a reduction of ozone formation. Biogenic VOCs played an important role in the local ozone formation. This study demonstrates the significant mixed effects of both anthropogenic pollution from urban zones and biogenic emission in rural areas on the regional O3 pollution in the NCP region, and may have general applicability in facilitating the understanding of the formation of secondary pollution over China.

Indoor and outdoor concentrations of PM2.5-associated perchlorate (ClO4(-)) and chlorate (ClO3(-)) were investigated in Jinan, China, and size-resolved perchlorate and chlorate were studied in Kumamoto, Japan. The average outdoor PM2.5-associated concentrations of perchlorate and chlorate were 4.18 ng m(-3) and 2.82 ng m(-3), respectively, in Jinan. Perchlorate and chlorate were mainly distributed in fine particles, and their approximate PM2.5-associated concentrations were 0.04 ng m(-3) and 4.14 ng m(-3), respectively, in Kumamoto. The ratios of ClO3(-)/ClO4(-) ranged from 18.72 to 360.22 in Kumamoto and from 0.03 to 7.45 in Jinan. The highest concentration of perchlorate (173.76 ng m(-3)) was observed on Spring Festival Eve. This finding and the significant correlation between perchlorate and fireworks-related components (Cl(-) and K(+)) indicated that the fireworks display was a significant source of perchlorate in Jinan. The indoor concentrations of perchlorate and chlorate in Jinan were 3.54 ng m(-3) (range, 0.14-125.14 ng m(-3)) and 0.94 ng m(-3) (range, 0.10-1.80 ng m(-3)), respectively. In the absence of an indoor source of perchlorate, the occurrence of indoor concentrations higher than those found outdoors was a common effect of individual fireworks displays near the sampling sites, coupled with meteorological influences and poor indoor diffusion conditions. The exposure risks of perchlorate and chlorate indoors indicated that the potential risk of perchlorate exposure to children during fireworks displays is deserving of concern.

Indoor/outdoor and diurnal/nocturnal variations in PM 2.5 and associated water-soluble ions and polycyclic aromatic hydrocarbons (PAHs) were examined in a business office during the summer and autumn of 2010 in Jinan, China. Both indoor and outdoor PM 2.5 levels were higher than the value recommended by the WHO, and outdoor sources were found to be the major contributors to indoor PM 2.5 . SO 4 2− , NO 3 − and NH 4 + were the dominant water-soluble ions in both indoor and outdoor particles. During daytime, NO 3 − mainly came from indoor sources, which was related to the temperature difference between the indoor and outdoor air. During daytime, the 15 monitored PAHs were all largely from indoor sources, while during nighttime, the 3 –4-ring PAHs were mainly generated indoors and the 5–6-ring PAHs predominantly came from the outdoor air. The diurnal/nocturnal variations of PAHs suggested that gas/particle partitioning driven by temperature makes a significant contribution to the variation in PAH concentrations. The diagnostic ratios revealed that biomass burning had an important contribution to outdoor PAH concentrations in autumn. The results of a risk assessment of PAH pollution suggested that indoor PAHs present more carcinogenic and mutagenic risks during daytime. Our results indicated that serious indoor air pollution in a business office presents a high health risk for workers.

The Yellow River Delta is a crucial background site that is located in a heavily polluted area in China. Carbonaceous aerosol concentrations were measured using 2.5-μm-diameter particle (PM2.5) samples collected from the Yellow River Delta, Shandong Province, China, from January 2011 to November 2011 by using the thermal/optical reflectance method. In the Yellow River Delta, the organic carbon (OC) concentration ranged from 0.74 to 27.51 μg/m3; the annual average concentration was 7.61 μg/m3. Moreover, the elemental carbon (EC) concentration ranged from 0.16 to 15.00 μg/m3; the annual average concentration was 2.98 μg/m3. In addition, the carbonaceous aerosols concentrations were the highest in winter and lowest in summer. The EC tracer method showed that the secondary OC (SOC) contribution to the total carbonaceous concentration tended to be higher in winter than in other seasons. An analysis of carbonaceous showed that haze was derived from different matter in different seasons, particularly haze in winter was dominated by OC, EC, and SOC. The Yellow River Delta can be considered a background site because of the strong correlation between OC and EC (R2 = 0.83–0.97). Furthermore, the OC/EC ratios for cold seasons (winter and spring) were higher than those for warm seasons (summer and autumn), suggesting that the OC originated from biomass burning in nearby villages in cold seasons. Back trajectories indicated that short-distance air mass from region area contribute most to the sample site. However, the highest carbon concentrations during haze days were related to the air mass travelled through the Bohai rin Rim except in summer haze episodes. Based on the entire sampling period, the air mass travelled through the polluted areas of Beijing and Hebei Province toward the Yellow River Delta may contribute most to carbonaceous species due to long-range transport.

Severe PM2.5 pollution was observed frequently on the North China Plain, and nitrate contributed a large fraction of the elevated PM2.5 concentrations. To obtain a comprehensive understanding of the formation pathways of these fine particulate nitrate and the key factors that affect these pathways, field measurements of fine particulate nitrate and related air pollutants were made at a rural site on the North China Plain in the summer of 2013. Extremely high concentrations of fine particulate nitrate were frequently observed at night and in the early morning. The maximum hourly concentration of fine particulate nitrate reached 87.2 m gm � 3 . This concentration accounted for 29.9% of the PM

Particulate chloride can be converted to nitryl chloride (ClNO2) through heterogeneous reactions with dinitrogen pentoxide (N2O5), and photolysis of ClNO2 affects atmospheric oxidative capacity. However, the characteristics and sources of chloride, especially those with an anthropogenic origin, are poorly characterized, which makes it difficult to evaluate the effects of ClNO2 on radical chemistry and air quality in polluted regions. Aerosol composition data from the literature were compiled to derive the spatial distributions of particulate chloride across China, and hourly aerosol composition data collected at a highly polluted inland urban site in eastern China and at a coastal site in southern China were analysed to gain further insights into non-oceanic sources of chloride. The results show that particulate chloride is concentrated mainly in fine particles and that high chloride loadings are observed in the inland urban areas of northern and western China with higher Cl-/Na+ mass ratios (2.46 to 5.00) than sea water (1.81), indicative of significant contributions from anthropogenic sources. At the inland urban site, the fine chloride displays distinct seasonality, with higher levels in winter and summer. Correlation analysis and positive matrix factorization (PMF) results indicate that coal combustion and residential biomass burning are the main sources (84.8%) of fine chloride in winter, and open biomass burning is the major sources (52.7%) in summer. The transport of plumes from inland polluted areas leads to elevated fine chloride in coastal areas. A simulation with WRF-Chem model confirmed a minor contribution of sea-salt aerosol to fine chloride at the inland site during summer with winds from the East Sea. The widespread sources of chloride, together with abundant NOx and ozone, suggest significant ClNO2 production and subsequent enhanced photochemical processes over China.

Particle number concentration was measured in 2011 in the Yellow River Delta (YRD) of eastern China. The objectives were to study the number size distribution characteristics of ambient aerosols and the meteorological effects on the particle physical characterisation, in addition to investigating the new particle formation (NPF) events in the Yellow River Delta. The particle formation rates and growth rates of the newborn particles were evaluated to identify the new particle formation events. The annual median total number concentration (5–10,000 nm) was 10,349 cm−3, with a maximum concentration in autumn and lowest in winter. A higher number concentration was observed for Aitken mode particles than for accumulation and nucleation mode particles. Higher temperature and lower humidity could favour the homogeneous nucleation. With increasing wind speed, the Aitken and accumulation mode particle numbers decreased obviously, and the particle sizes were reduced. Higher particle number concentrations were associated with southeast local air masses which passed from polluted area, and smaller diameter peaks were associated with northern air masses. In total, 26 new particle formation events were recorded during the 120 days of measurements, and this frequency was slightly lower than that observed in other cities in China. The mean growth and formation rates were calculated as 5.3 nm h−1 and 6.6 cm−3 s−1, respectively. High SO2 and O3 concentrations might have contributed to the increase in nucleation mode particles in the NPF events.

To better understand the pollution characteristics and potential sources of PM2.5 ionic components at the Yellow River Delta (YRD), a semicontinuous measurement was conducted to observe water-soluble ions in PM2.5 at a nature reserve in Dongying of Shandong province, China, in 2011. The results showed that SO4 2−, NO3 −, and NH4 + were the dominant ionic species (constituting 93 % of the total ionic mass) with their annual average concentrations of 22.48, 12.77, and 11.21 μg/m3, respectively. These three ion concentrations were generally lower than those observed in major cities in China but higher than those in other rural and nature reserve sites. Ion concentrations exhibited large seasonal variations, and maximum values were observed in summer. SO4 2− concentration presented a daytime peak in summer, autumn, and winter, while in spring, a relative flat diurnal cycle was observed. NO3 − concentration changed with that of SO4 2− during most of measurement period. Transport from surrounding areas contributed to the diurnal cycle of secondary ions. In addition, photochemical reaction and thermodynamic equilibrium played important roles on the diurnal variation of SO4 2− and NO3 −, respectively. The aerosol at the YRD was weakly acidic, and it was most acidic in winter. A cluster analysis showed that fine particle pollution at the YRD was mainly affected by southwest local emissions and northern middle- to long-distance transport.

The size-fractionated characteristics of particulate polycyclic aromatic hydrocarbons (PAHs) were studied from January 2011 to October 2011 using a Micro-orifice Uniform Deposit Impactor (MOUDI) at the Yellow River Delta National Nature Reserve (YRDNNR), a background site located in the North China Plain. The average annual concentration of total PAHs in the YRDNNR (18.95 ± 16.51 ng/m(3)) was lower than that in the urban areas of China; however, it was much higher than that in other rural or remote sites in developed countries. The dominant PAHs, which were found in each season, were fluorene (5.93%-26.80%), phenanthrene (8.17%-26.52%), fluoranthene (15.23%-27.12%) and pyrene (9.23%-16.31%). A bimodal distribution was found for 3-ring PAHs with peaks at approximately 1.0-1.8 μm and 3.2-5.6 μm; however, 4-6 ring PAHs followed a nearly unimodal distribution, with the highest peak in the 1.0-1.8 μm range. The mass median diameter (MMD) values for the total PAHs averaged 1.404, 1.467, 1.218 and 0.931 μm in spring, summer, autumn and winter, respectively. The toxicity analysis indicated that the carcinogenic potency of particulate PAHs existed primarily in the1.8 μm size range. Diagnostic ratios and PCA analysis indicated that the PAHs in aerosol particles were mainly derived from coal combustion. In addition, back-trajectory calculations demonstrated that atmospheric PAHs were produced primarily by local anthropogenic sources.

Intensive firecracker/firework displays during Chinese New Year (CNY) release fine particles and gaseous pollutants into the atmosphere, which may lead to serious air pollution. We monitored ambient PM2.5 and black carbon (BC) concentrations at a regional background site in the Yellow River Delta region during the CNY in 2011. Our monitoring data and MOUDI images showed that there was a haze event during the CNY. Daily average PM2.5 concentration reached 183 μg m− 3 during the CNY, which was six times higher than that before and after the CNY. Similarly, the black carbon (BC) concentrations were elevated during the CNY. In order to confirm whether the firecracker/firework related emission is the main source of the haze particles, we further analyzed the morphology and chemical composition of individual airborne particles collected before, during and after the CNY by using transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy (TEM/EDS). We found that sulfate and organic-rich particles were dominant in the atmosphere before and after the CNY. In contrast, K-rich sulfates and other metal (e.g., Ba-rich, Al-rich, Mg-rich, and Fe-rich) particles were much more abundant than ammoniated sulfate particles during the CNY. These data suggest that it was the aerosol particles from the firecracker/firework emissions that induced the regional haze episode during the CNY. In individual organic and K-rich particles, we often found more than two types of nano-metal particles. These metal-bearing particles also contained abundant S but not Cl. In contrast, fresh metal-bearing particles from firecrackers generated in the laboratory contained abundant Cl with minor amounts of S. This indicates that the firecracker/firework emissions during the CNY significantly changed the atmospheric transformation pathway of SO2 to sulfate.

Ambient fine particulate matter (PM2.5) and volatile organic compounds (VOCs) collected at Mt. Tai in summer 2014 were analysed and the data were used to identify the contribution of biogenic and anthropogenic hydrocarbons to secondary organic aerosols (SOA) and their sources and potential source areas in high mountain regions. Compared with those in 2006, the 2014 anthropogenic SOA tracers in PM2.5 aerosols and VOC species related to vehicular emissions exhibited higher concentrations, whereas the levels of biogenic SOA tracers were lower, possibly due to decreased biomass burning. Using the SOA tracer and parameterisation method, we estimated the contributions from biogenic and anthropogenic VOCs, respectively. The results showed that the average concentration of biogenic SOA was 1.08 ± 0.51 μg m-3, among which isoprene SOA tracers were dominant. The anthropogenic VOC-derived SOA were 7.03 ± 1.21 μg m-3 and 1.92 ± 1.34 μg m-3 under low- and high-NOx conditions, respectively, and aromatics made the greatest contribution. However, the sum of biogenic and anthropogenic SOA only contributed 18.1-49.1% of the total SOA. Source apportionment by positive matrix factorisation (PMF) revealed that secondary oxidation and biomass burning were the major sources of biogenic SOA tracers. Anthropogenic aromatics mainly came from solvent use, fuel and plastics combustion and vehicular emissions. However, for > C6 alkanes and cycloalkanes, vehicular emissions and fuel and plastics combustion were the most important contributors. The potential source contribution function (PSCF) identified the Bohai Sea Region (BSR) as the major source area for organic aerosol compounds and VOC species at Mt. Tai.

Daily PM 2.5 samples were collected simultaneously at an urban site (SD) and a rural site (MP) in Jinan, China from March 2006 to February 2007. The samples were analyzed for major inorganic and organic water-soluble ions, 24 elements and carbonaceous species to determine the spatial and temporal variations of PM 2.5 mass concentrations and chemical compositions and evaluate their contributions to visibility impairment. The annual average concentrations of PM 2.5 were 148.71 μg m −3 and 97.59 μg m −3 at SD and MP, respectively. The predominant component of PM 2.5 was (NH 4 ) 2 SO 4 at SD and organic mass at MP, which accounted for 28.71% and 37.25% of the total mass, respectively. The higher SOR (sulfur oxidation ratio) and ratios of OC/EC at SD indicated that the formation of secondary inorganic ions and secondary organic aerosols (SOA) could be accelerated in the urban area. Large size (NH 4 ) 2 SO 4 and large size organic mass were the most important contributors to visibility impairment at SD and MP, accounting for 43.80% and 41.02% of the light extinction coefficient, respectively.

To determine the characteristics of carbonaceous aerosols in rural areas of the North China Plain, field measurements were conducted at Yucheng (YC) in the summers of 2013 and 2014. The concentrations of carbonaceous aerosols at YC exhibited clear diurnal variation, with higher concentrations in the early morning and at night and lower concentrations during the afternoon hours. The mass-balance method designed for particulate matter smaller than 2.5μm (PM2.5) was used to calculate the organic matter (OM)/organic carbon (OC) ratio. The value obtained, 2.07±0.05, was suggested as a reference to estimate organics in PM2.5 in rural areas of the North China Plain. Biomass burning was identified to be a significant source of carbonaceous aerosols; approximately half of the samples obtained at YC were affected by biomass burning during summer 2013. Case studies revealed that biomass burning accounted for up to 52.6% of the OC and 51.1% of the elemental carbon in PM2.5 samples. The organic coatings observed on sulphur-rich and potassium-rich particles indicated the formation of secondary organic aerosols (SOA) from the oxidation of precursor volatile organic compounds (VOCs) during the aging of smoke released from biomass burning. Based on the evolution of the VOCs, the contribution of VOCs oxidation to SOA concentration was 3.21 and 1.07μgm(-3)ppm(-1) CO under conditions of low nitrogen oxide (NOx) and high NOx, respectively. Aromatics (e.g. benzene, toluene, xylene and ethylbenzene) made the greatest contribution to SOA concentration (88.4% in low-NOx conditions and 80.6% in high-NOx conditions). The results of the study offer novel insights into the effects of biomass burning on the carbonaceous aerosols and SOA formation in polluted rural areas.

To better understand secondary aerosol pollution and potential source regions, semi-continuous measurement of water-soluble ions in PM2.5 was performed from December 2007 to October 2008 in Jinan, the capital of Shandong Province. The data was analyzed with the aid of backward trajectory cluster analysis in conjunction with redistributed concentration field (RCF) model and principal component analysis (PCA). SO 4 2 − , NO 3 − and NH 4 + were the most abundant ionic species with annual mean concentrations (±standard deviations) of 38.33 (±26.20), 15.77 (±12.06) and 21.26 (±16.28) μg m−3, respectively, which are among the highest levels reported in the literatures in the world. Well-defined seasonal and diurnal patterns of SO 4 2 − , NO 3 − and NH 4 + were observed. The fine sulfate and nitrate oxidation ratios (SOR and NOR) were much higher in summer (SOR: 0.47 ± 0.13; NOR: 0.28 ± 0.03) than those in other seasons (SOR: 0.17–0.30; NOR: 0.12–0.14), indicating more extensive formations of SO 4 2 − and NO 3 − in summer. The most frequent air masses connected with high concentrations of SO 4 2 − , NO 3 − and NH 4 + originated from Shandong Province in spring, autumn and winter, while from the Yellow Sea in summer, and then slowly traveled in Shandong Province to Jinan. RCF model indicated that Shandong Province was the main potential source region for SO 4 2 − and NO 3 − and other potential source regions were also identified including the provinces of Hebei, Henan, Anhui and Jiangsu and the Yellow Sea. Principal component analysis indicated that the major sources contributing to PM2.5 pollution were secondary aerosols, coal/biomass burnings and traffic emissions.

Aerosol size distributions, trace gas, and PM(2.5) concentrations have been measured in urban Jinan, China, over 6 months in 2007 and 2008, covering spring, summer, fall, and winter time periods. Number concentrations of particles (10-2,500 nm) were 16,200, 13,900, 11,200, and 21,600 cm( -3) in spring, summer, fall, and winter, respectively. Compared with other urban studies, Jinan has higher number concentrations of accumulation-mode particles (100-500 nm) and particles (10-2,500 nm), but lower concentrations of ultrafine particles (10-100 nm). The number, surface and volume concentrations, and size distributions of particles showed obvious seasonal variation and are also influenced by traffic emissions. Through correlation analysis, traffic emissions are proposed to be a more important contributor to Atkien-mode and accumulation-mode particles than coal firing. Around midday, the presence of nanoparticles and new particle formation is limited to pre-existing particles from traffic emissions and the mass transport of particles from suburban and rural areas. Compared with other studies in urban areas of Europe and the USA, the variation of particle number concentration and related gas concentration in Jinan between weekdays and weekends is smaller and the reasons has been deduced.

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.

To better understand the sources and potential source regions of PM2.5, a field study was conducted from January 2011 to November 2011 at a background site, the Yellow River Delta National Nature Reserve (YRDNNR) in the North China Plain. Positive matrix factorisation (PMF) analysis and a potential source contribution function (PSCF) model were used to assess the data, which showed that YRDNNR experienced serious air pollution. Concentrations of PM2.5 at YRDNNR were 71.2, 92.7, 97.1 and 62.5 μg m(-3) in spring, summer, autumn and winter, respectively, with 66.0% of the daily samples exhibiting higher concentrations of PM2.5 than the national air quality standard. PM2.5 mass closure showed remarkable seasonal variations. Sulphate, nitrate and ammonium were the dominant fractions of PM2.5 in summer (58.0%), whereas PM2.5 was characterized by a high load of organic aerosols (40.2%) in winter. PMF analysis indicated that secondary sulphate and nitrate (54.3%), biomass burning (15.8%), industry (10.7%), crustal matter (8.3%), vehicles (5.2%) and copper smelting (4.9%) were important sources of PM2.5 at YRDNNR on an annual average. The source of secondary sulphate and nitrate was probably industrial coal combustion. PSCF analysis indicated a significant regional impact on PM2.5 at YRDNNR all year round. Local emission may be non-negligible at YRDNNR in summer. The results of the present study provide a scientific basis for the development of PM2.5 control strategies on a regional scale.

International audience; Haze episodes often hit urban cities in China recently. Here, we present several continuous haze episodes with extremely high PM2.5 levels that occurred over several weeks in early 2013 and extended across most parts of the northern and eastern China—far exceeding the Beijing–Tianjin–Hebei region. Particularly, the haze episode covered ~ 1 million km2 on January 14, 2013 and the daily averaged PM2.5 concentration exceeded 360 μg m− 3 in Ji'nan. The observed maximum hourly PM2.5 concentration in urban Ji'nan reached 701 μg m− 3 at 7:00 am (local time) in January 30. During these haze episodes, several fog events happened and the concurrent fog water was found to be seriously polluted. For the fog water collected in Ji'nan from 10:00 pm in January 14 to 11:00 am in January 15, sulfate, nitrate, and ammonium were the major ions with concentrations of 1.54 × 106, 8.98 × 105, and 1.75 × 106 μeq L− 1, respectively, leading to a low in-situ pH of 3.30. The sulfate content in the fog sample was more than 544 times as high as those observed in other areas. With examination of the simultaneously observed data on PM2.5 and its chemical composition, the fog played a role in scavenging and removing fine particles from the atmosphere during haze episodes and thus was seriously contaminated. However, the effect was not sufficient to obviously cleanse air pollution and block haze episodes.