Seasonal variations of transport pathways and potential sources of PM2.5 in Chengdu,China (2012–2013)

PM_2.5 in Chengdu showed clear seasonal and diurnal variation. 5, 5, 5 and 3 mean clusters are generated in spring, summer, autumn, and winter. Short-distance air masses are important pathways in Chengdu. Emissions within the Sichuan Basin contribute significantly to PM_2.5 pollution. Long-range transport from Southern Xinjiang is a dust invasion path to Chengdu. Seasonal pattern of transport pathways and potential sources of PM_2.5 in Chengdu during 2012–2013 were investigated based on hourly PM_2.5 data, backward trajectories, clustering analysis, potential source contribution function (PSCF), and concentration-weighted trajectory (CWT) method. The annual hourly mean PM_2.5 concentration in Chengdu was 97.4 mg·m^–3. 5, 5, 5 and 3 mean clusters were generated in four seasons, respectively. Short-distance air masses, which travelled within the Sichuan Basin with no specific source direction and relatively high PM_2.5 loadings (>80 mg·m^–3) appeared as important pathways in all seasons. These short pathways indicated that emissions from both local and surrounding regions of Chengdu contributed significantly to PM_2.5 pollution. The cities in southern Chengdu were major potential sources with PSCF>0.6 and CWT>90 mg·m^–3. The northeastern pathway prevailed throughout the year with higher frequency in autumn and winter and lower frequency in spring and summer. In spring, long-range transport from southern Xinjiang was a representative dust invasion path to Chengdu, and the CWT values along the path were 30-60 mg·m^–3. Long-range transport was also observed in autumn from southeastern Xinjiang along a northwesterly pathway, and in winter from the Tibetan Plateau along a westerly pathway. In summer, the potential source regions of Chengdu were smaller than those in other seasons, and no long-range transport pathway was observed. Results of PSCF and CWT indicated that regions in Qinghai and Tibet contributed to PM_2.5 pollution in Chengdu as well, and their CWT values increased to above 30 mg·m^-3 in winter.     

Local and regional contributions to PM2.5 in the Beijing 2022 Winter Olympics infrastructure areas during haze episodes

• Regional transportation contributed more than local emissions during haze episodes. • Short-range regional transportation contributed the most to the PM_2.5 in the OIAs. • Low wind speeds and low PBLHs led to higher local contributions to Beijing. The 2022 Winter Olympics is scheduled to take place in Beijing and Zhangjiakou, which were defined as OIAs (Olympic infrastructure areas) in this study. This study presents the characteristics and source apportionment of PM_2.5 in the OIAs, China. The entire region of mainland China, except for the OIAs, was divided into 9 source regions, including four regions in the BTH(Beijing-Tianjin-Hebei) region, the four provinces surrounding the BTH and the remaining areas. Using CAMx/PSAT, the contributions of the nine regions to the PM_2.5 concentration in the OIAs were simulated spatially and temporally. The simulated source apportionment results showed that the contribution of regional transportation was 48.78%, and when PM_2.5 concentration was larger than 75 μg/m³ central Hebei was the largest contributor with a contribution of 19.18%, followed by Tianjin, northern Hebei, Shanxi, Inner Mongolia, Shandong, southern Hebei, Henan and Liaoning. Furthermore, the contribution from neighboring regions of the OIAs was 47.12%, which was nearly twice that of long-range transportation. Haze episodes were analyzed, and the results presented the importance of regional transportation during severe PM_2.5 pollution periods. It was also found that they were associated with differences in pollution sources between Zhangjiakou and Beijing. Regional transportation was the main factor affecting PM_2.5 pollution in Zhangjiakou due to its low local emissions. Stagnant weather with a low planetary boundary layer height and a low wind velocity prevented the local emitted pollutants in Beijing from being transported outside, and as a result, local emissions constituted a larger contribution in Beijing.     

Photolysis and photooxidation of typical gaseous VOCs by UV Irradiation: Removal performance and mechanisms

UV photodegradation of 27 typical VOCs was systematically investigated. Contribution of photolysis and photooxidation to VOCs removal was identified. Gaseous VOC could be partially converted to particles by 185/254 nm UV irradiation. The mineralization and conversion of 27 VOCs by UV irradiation were reported. Photodegradation by ultraviolet irradiation (UV) is increasingly applied in volatile organic compound (VOC) and odor gas treatments. In this study, 27 typical VOCs, including 11 hydrocarbons and 16 hydrocarbon derivatives, at 150–200 ppm in air and nitrogen gas were treated by a laboratory-scale UV reactor with 185/254 nm irradiation to systematically investigate their removal and conversion by UV irradiation. For the tested 27 VOCs, the VOC removal efficiencies in air were within the range of 13%–97% (with an average of 80%) at a retention time of 53 s, which showed a moderate positive correlation with the molecular weight of the VOCs (R = 0.53). The respective contributions of photolysis and photooxidation to VOC removal were identified for each VOC. According to the CO₂ results, the mineralization rate of the tested VOCs was within the range of 9%–90%, with an average of 41% and were negatively correlated to the molecular weight (R = -0.63). Many of the tested VOCs exhibited high concentration particulate matters in the off-gases with a 3–283 mg/m³ PM₁₀ range and a 2–40 mg/m³ PM_2.5 range. The carbon balance of each VOC during UV irradiation was analyzed based on the VOC, CO₂ and PM₁₀ concentrations. Certain organic intermediates and 23–218 ppm ozone were also identified in the off-gases. Although the UV technique exhibited a high VOC removal efficiency, its drawbacks, specifically low mineralization, particulate matters production, and ozone emission, must be considered prior to its application in VOC gas treatments.     

Temporal variation of PM2.5-associated health effects in Shijiazhuang,Hebei

•Annual mean PM_2.5 in Shijiazhuang were 87, 95, and 82 µg/m³ in 2015–2017. •Health risk of cardiovascular system was higher than respiratory system. •Premature mortality attributed to PM_2.5 was 5088 people in 2017. •ΔMort and YLL reduced by 84.2% and 84.6% when PM_2.5 reduced to 10 µg/m³. •Health risks due to PM_2.5 were severe in Shijiazhuang in 2015–2017. Shijiazhuang is one of the cities in the North China Plain. In recent decades, this city has experienced high levels of fine particulate matter (PM_2.5), which have potentially significant effects on human health. In this study, the health effects of PM_2.5 exposure in Shijiazhuang were estimated by applying an integrated exposure-response model. Premature mortality, years of life lost (YLL), and the mortality benefits linked to reduced levels of PM_2.5 were quantified for the period 2015–2017. In 2015, 2016, and 2017, cerebrovascular diseases caused the highest premature mortality (2432, 2449, and 2483, respectively), followed by ischemic heart diseases (1391, 1479, and 1493, respectively), lung cancer (639,660, and 639, respectively), and chronic obstructive pulmonary diseases (533, 519, and 473, respectively). Notably, the total number of premature deaths caused by PM_2.5 exposure in Shijiazhuang in 2015, 2016, and 2017 were 4994, 5107, and 5088, respectively. Moreover, the YLL in the same years were 47001, 47880 and 47381, respectively. Interestingly, the YLL per 1000 females was lower than that per 1000 males. Finally, we noted that premature mortality and YLL decreased by 84.2% and 84.6% when the PM_2.5 levels diminished to 10 µg/m³. Overall, the results of this study improve our understanding of how high PM_2.5 concentrations affect human health and suggest the application of more stringent measures in Shijiazhuang to alleviate the associated health risks.     

Relations between indoor and outdoor PM2.5 and constituent concentrations

Factors impacting indoor-outdoor relations are introduced. Sulfate seems a fine tracer for other non-volatile species. Particulate nitrate and ammonium desorb during outdoor-to-indoor transport. OC load increases during the transport due to sorption of indoor SVOCs. Outdoor PM_2.5 influences both the concentration and composition of indoor PM_2.5. People spend over 80% of their time indoors. Therefore, to assess possible health effects of PM_2.5 it is important to accurately characterize indoor PM_2.5 concentrations and composition. Controlling indoor PM_2.5 concentration is presently more feasible and economic than decreasing outdoor PM_2.5 concentration. This study reviews modeling and measurements that address relationships between indoor and outdoor PM_2.5 and the corresponding constituent concentrations. The key factors in the models are indoor-outdoor air exchange rate, particle penetration, and deposition. We compiled studies that report I/O ratios of PM_2.5 and typical constituents (sulfate (SO₄^2-), nitrate (NO₃^-), ammonium (NH₄⁺), elemental carbon (EC), and organic carbon (OC), iron (Fe), copper (Cu), and manganese (Mn)). From these studies we conclude that: 1) sulfate might be a reasonable tracer of non-volatile species (EC, Fe, Cu, and Mn) and PM_2.5 itself; 2) particulate nitrate and ammonium generally desorb to gaseous HNO₃ and NH₃ when they enter indoors, unless, as seldom happens, they have strong indoor sources; 3) indoor-originating semi-volatile organic compounds sorb on indoor PM_2.5, thereby increasing the PM_2.5 OC load. We suggest further studies on indoor-outdoor relationships of PM_2.5 and constituents so as to help develop standards for healthy buildings.     

Collaborative control of fine particles and ozone required in China for health benefit

● Increased DAAO offsets 3/4 of the decrease of DAAP in 2013–2020. ● DAAO increases are mainly due to O₃ concentration increase and population aging. ● Health benefit from PM_2.5 reduction after 2017 is larger than that before 2017. ● Reducing PM_2.5 concentration by 1% results in 0.6% reduction of DAAP. ● Reducing O₃ concentration by 1% results in 2% reduction of DAAO. PM_2.5 concentration declined significantly nationwide, while O₃ concentration increased in most regions in China in 2013–2020. Recent evidences proved that peak season O₃ is related to increased death risk from non-accidental and respiratory diseases. Based on these new evidences, we estimate excess deaths associated with long-term exposure to ambient PM_2.5 and O₃ in China following the counterfactual analytic framework from Global Burden Disease. Excess deaths from non-accidental diseases associated with long-term exposure to ambient O₃ in China reaches to 579 (95% confidential interval (CI): 93, 990) thousand in 2020, which has been significantly underestimated in previous studies. In addition, the increased excess deaths associated with long-term O₃ exposure (234 (95% CI: 177, 282) thousand) in 2013–2020 offset three quarters of the avoided excess deaths (302 (95% CI: 244, 366) thousand) mainly due to PM_2.5 exposure reduction. In key regions (the North China Plain, the Yangtze River Delta and the Fen-Wei Plain), the former is even larger than the latter, particularly in 2017–2020. Health benefit of PM_2.5 concentration reduction offsets the adverse effects of population growth and aging on excess deaths attributed to PM_2.5 exposure. Increase of excess deaths associated with O₃ exposure is mainly due to the strong increase of O₃ concentration, followed by population aging. Considering the faster population aging process in the future, collaborative control, and faster reduction of PM_2.5 and O₃ are needed to reduce the associated excess deaths.     

PM2.5 over North China based on MODIS AOD and effect of meteorological elements during 2003‒2015

• The Taihang Mountains was the boundary between high and low pollution areas. • There were one high value center for PM_2.5 pollution and two low value centers. • In 2004, 2009 and after 2013, PM_2.5 concentration was relatively low. Over the past 40 years, PM_2.5 pollution in North China has become increasingly serious and progressively exposes the densely populated areas to pollutants. However, due to limited ground data, it is challenging to estimate accurate PM_2.5 exposure levels, further making it unfavorable for the prediction and prevention of PM_2.5 pollutions. This paper therefore uses the mixed effect model to estimate daily PM_2.5 concentrations of North China between 2003 and 2015 with ground observation data and MODIS AOD satellite data. The tempo-spatial characteristics of PM_2.5 and the influence of meteorological elements on PM_2.5 is discussed with EOF and canonical correlation analysis respectively. Results show that overall R² is 0.36 and the root mean squared predicted error was 30.1 μg/m³ for the model prediction. Our time series analysis showed that, the Taihang Mountains acted as a boundary between the high and low pollution areas in North China; while the northern part of Henan Province, the southern part of Hebei Province and the western part of Shandong Province were the most polluted areas. Although, in 2004, 2009 and dates after 2013, PM_2.5 concentrations were relatively low. Meteorological/topography conditions, that include high surface humidity of area in the range of 34°‒40°N and 119°‒124°E, relatively low boundary layer heights, and southerly and easterly winds from the east and north area were common factors attributed to haze in the most polluted area. Overall, the spatial distribution of increasingly concentrated PM_2.5 pollution in North China are consistent with the local emission level, unfavorable meteorological conditions and topographic changes.     

Impacts of emissions and meteorological changes on China’s ozone pollution in the warm seasons of 2013 and 2017

O₃ increment is mainly caused by changes in meteorology rather than emissions. Emission reduction is effective to reduce O₃ nationwide, especially in summer. Strengthened NO_x controls are necessary to meet the ambient O₃ standard. We have quantified the impacts of anthropogenic emissions reductions caused by the Air Pollution Control Action Plan and changes in meteorological fields between 2013 and 2017 on the warm-season O₃ concentration in China using a regional 3D chemical transport model. We found that the impact on daily maximum eight-hour (MDA8) O₃ concentration by the meteorological variation that mostly increased O₃ was greater than that from emission reduction, which decreased O₃. Specifically, the control measures implemented since 2013 in China have reduced SO₂, NO_x, PM_2.5, and VOC emissions by 33%, 25%, 30%, and 4% in 2017, while NH₃ emissions have increased by 7%. The changes in anthropogenic emissions lowered MDA8 O₃ by 0.4–3.7 ppb (0.8%–7.6%, varying by region and month), although MDA8 O₃ was increased slightly in some urban areas (i.e. North China) at the beginning/end of warm seasons. Relative to 2013, the average 2 m temperature in 2017 shows increments in North, North-east, East, and South China (0.34℃–0.83℃) and decreases in Central China (0.24℃). The average solar radiation shows increments in North, North-east, and South China (7.0–9.7 w/m²) and decreases in Central, South-west, and North-west China (4.7–10.3 w/m²). The meteorological differences significantly change MDA8 O₃ by -3.5–8.5 ppb (-8.2%–18.8%) with large temporal variations. The average MDA8 O₃ was slightly increased in North, North-east, East, and South China. The response surface model suggests that the O₃ formation regime transfers from NO_x-saturated in April to NO_x-limited in July on average in China.     

Understand the local and regional contributions on air pollution from the view of human health impacts

• PM_2.5-related deaths were estimated to be 227 thousand in BTH & surrounding regions. • Local emissions contribute more to PM_2.5-related deaths than PM_2.5 concentration. • Local controls are underestimated if only considering its impacts on concentrations. • Rural residents suffer larger impacts of regional transport than urban residents. • Reducing regional transport benefits in mitigating environmental inequality. The source-receptor matrix of PM_2.5 concentration from local and regional sources in the Beijing-Tianjin-Hebei (BTH) and surrounding provinces has been created in previous studies. However, because the spatial distribution of concentration does not necessarily match with that of the population, such concentration-based source-receptor matrix may not fully reflect the importance of pollutant control effectiveness in reducing the PM_2.5-related health impacts. To demonstrate that, we study the source-receptor matrix of the PM_2.5-related deaths instead, with inclusion of the spatial correlations between the concentrations and the population. The advanced source apportionment numerical model combined with the integrated exposure–response functions is used for BTH and surrounding regions in 2017. We observed that the relative contribution to PM_2.5-related deaths of local emissions was 0.75% to 20.77% larger than that of PM_2.5 concentrations. Such results address the importance of local emissions control for reducing health impacts of PM_2.5 particularly for local residents. Contribution of regional transport to PM_2.5-related deaths in rural area was 22% larger than that in urban area due to the spatial pattern of regional transport which was more related to the rural population. This resulted in an environmental inequality in the sense that people staying in rural area with access to less educational resources are subjected to higher impacts from regional transport as compared with their more resourceful and knowledgeable urban compatriots. An unexpected benefit from the multi-regional joint controls is suggested for its effectiveness in reducing the regional transport of PM_2.5 pollution thus mitigating the associated environmental inequality.     

Enrichment and transfer of polycyclic aromatic hydrocarbons (PAHs) through dust aerosol generation from soil to the air

● Compositional patterns of PAHs in dust aerosol vary from soil during dust generation. ● The EF of PAH in dust aerosol is affected by soil texture and soil PAH concentration. ● The sizes of dust aerosol play an important role in the enrichment of HMW-PAHs. Polycyclic aromatic hydrocarbons (PAHs) are major organic pollutants in soil. It is known that they are released to the atmosphere by wind via dust aerosol generation. However, it remains unclear how these pollutants are transferred through the air/soil interface. In this study, dust aerosols were generated in the laboratory using soils (sandy loam and loam) with various physicochemical properties. The PAH concentrations of these soils and their generated dust aerosol were measured, showing that the enrichment factors (EFs) of PAHs were affected by soil texture, PAH contamination level, molecular weight of PAH species and aerosol sizes. The PAHs with higher EFs (6.24–123.35 in dust PM_2.5; 7.02–47.65 in dust PM₁₀) usually had high molecular weights with more than four aromatic rings. In addition, the positive correlation between EFs of PAHs and the total OC_aerosol content of dust aerosol in different particle sizes was also statistically significant (r = 0.440, P < 0.05). This work provides insights into the relationship between atmospheric PAHs and the contaminated soils and the transfer process of PAHs through the soil-air interface.     

Secondary aerosol formation in winter haze over the Beijing-Tianjin-Hebei Region,China

• Characteristics and interannual variation of aerosol pollution are illustrated. • Mechanisms of secondary aerosol formation in winter haze of North China are reviewed. • Directions in future studies of secondary aerosol formation are provided. Severe haze pollution occurs frequently in the winter over the Beijing-Tianjin-Hebei (BTH) region (China), exerting profound impacts on air quality, visibility, and human health. The Chinese Government has taken strict mitigation actions since 2013 and has achieved a significant reduction in the annual mean PM_2.5 concentration over this region. However, the level of secondary aerosols during heavy haze episodes showed little decrease during this period. During heavy haze episodes, the concentrations of secondary aerosol components, including sulfate, nitrate and secondary organics, in aerosol particles increase sharply, acting as the main contributors to aerosol pollution. To achieve effective control of particle pollution in the BTH region, the precise and complete secondary aerosol formation mechanisms have been investigated, and advances have been made about the mechanisms of gas phase reaction, nucleation and heterogeneous reactions in forming secondary aerosols. This paper reviews the research progress in aerosol chemistry during haze pollution episodes in the BTH region, lays out the challenges in haze formation studies, and provides implications and directions for future research.     

PM2.5 concentration declining saves health expenditure in China

● Monthly hospitalization expenses are sensitive to increases in PM_2.5 exposure. ● The increased PM_2.5 causes patients with CHD and LRI to stay longer in the hospital. ● The impact of PM_2.5 on total expenses for stroke is greater in southern China. ● Males may be more sensitive to air pollution than females. Air pollution has been a severe issue in China. Exposure to PM_2.5 has adverse health effects and causes economic losses. This study investigated the economic impact of exposure to PM_2.5 pollution using monthly city-level data covering 88.5 million urban employees in 2016 and 2017. This study mainly focused on three expenditure indicators to measure the economic impact considering lower respiratory infections (LRIs), coronary heart disease (CHD), and stroke. The results show that a 10 µg/m³ increase in PM_2.5 would cause total monthly expenses of LRIs, CHD, and stroke to increase by 0.226%, 0.237%, and 0.374%, respectively. We also found that LRI, CHD, and stroke hospital admissions increased significantly by 10%, 8.42%, and 5.64%, respectively. Furthermore, the total hospital stays of LRIs, CHDs, and strokes increased by 2.49%, 2. 51%, and 1.64%, respectively. Our findings also suggest heterogeneous impacts of PM_2.5 exposures by sex and across regions, but no statistical evidence shows significant differences between the older and younger adult subgroups. Our results provide several policy implications for reducing unequal public health expenditures in overpolluted countries.     

Diverse bacterial populations of PM2.5 in urban and suburb Shanghai,China

• Urban aerosols harbour diverse bacterial communities in Shanghai. • The functional groups were associated with nitrogen, carbon, and sulfur cycling. • Temperature, SO₂, and wind speed were key drivers for the bacterial community. Airborne bacteria play key roles in terrestrial and marine ecosystems and human health, yet our understanding of bacterial communities and their response to the environmental variables lags significantly behind that of other components of PM_2.5. Here, atmospheric fine particles obtained from urban and suburb Shanghai were analyzed by using the qPCR and Illumina Miseq sequencing. The bacteria with an average concentration of 2.12 × 10³ cells/m³, were dominated by Sphingomonas, Curvibacter, Acinetobacter, Bradyrhizobium, Methylobacterium, Halomonas, Aliihoeflea, and Phyllobacterium, which were related to the nitrogen, carbon, sulfur cycling and human health risk. Our results provide a global survey of bacterial community across urban, suburb, and high-altitude sites. In Shanghai (China), urban PM_2.5 harbour more diverse and dynamic bacterial populations than that in the suburb. The structural equation model explained about 27%, 41%, and 20%–78% of the variance found in bacteria diversity, concentration, and discrepant genera among urban and suburb sites. This work furthered the knowledge of diverse bacteria in a coastal Megacity in the Yangtze river delta and emphasized the potential impact of environmental variables on bacterial community structure.     

PVDF ultrafiltration membranes of controlled performance via blending PVDF-g-PEGMA copolymer synthesized under different reaction times

PVDF blended different graft ratio of PVDF-g-PEGMA were systematically studied. Tuning the amphiphilic copolymer synthesis time to control membrane performance. The PVDF membrane with PVDF-g-PEGMA at 19 h possesses most surface oxygen content. The synthesis time of PVDF-g-PEGMA at 9 h is good for high flux UF membrane. Polyvinylidene fluoride grafted with poly(ethylene glycol) methyl ether methacrylate (PVDF-g-PEGMA) was synthesized using atomic transfer radical polymerization (ATRP) at different reaction times (9 h, 19 h, and 29 h). The corresponding conversion rates were 10%, 20% and 30%, respectively. PVDF was blended with the copolymer mixture containing PVDF-g-PEGMA, solvent and residual PEGMA under different reaction times. In this study, we explored the effect of the copolymer mixture additives with different synthesis times on cast membrane performance. Increasing the reaction time of PVDF-g-PEGMA causes more PVDF-g-PEGMA and less residual PEGMA to be found in the casting solution. Incremental PVDF-g-PEGMA can dramatically increase the viscosity of the casting solution. An overly high viscosity led to a delayed phase inversion, thus hindering PEGMA segments in PVDF-g-PEGMA from migrating to the membrane surface. However, more residual PEGMA contributed to helping more PEGMA segments migrate to the membrane surface. The pure water fluxes of the blended membrane with reaction times of 9 h, 19 h, and 29 h are 5445 L·m⁻²·h⁻¹, 1068 L·m⁻²·h⁻¹and 1179 L·m⁻²·h⁻¹, respectively, at 0.07 MPa. Delayed phase inversion can form smaller surface pore size distributions, thus decreasing the water flux for the membranes with PVDF-g-PEGMA at 19 h and 29 h. Therefore, we can control the membrane pore size distribution by decreasing the reaction time of PVDF-g-PEGMA to obtain a better flux performance. The membrane with PVDF-g-PEGMA at 19 h exhibits the best foulant rejection and cleaning recovery due to its narrow pore size distribution and high surface oxygen content.     

Impact of anthropogenic heat emissions on meteorological parameters and air quality in Beijing using a high-resolution model simulation

• The Large scale Urban Consumption of energY model was updated and coupled with WRF. • Anthropogenic heat emissions altered the precipitation and its spatial distribution. • A reasonable AHE scheme could improve the performance of simulated PM_2.5. • AHE aggravated the O₃ pollution in urban areas. Anthropogenic heat emissions (AHE) play an important role in modulating the atmospheric thermodynamic and kinetic properties within the urban planetary boundary layer, particularly in densely populated megacities like Beijing. In this study, we estimate the AHE by using a Large-scale Urban Consumption of energY (LUCY) model and further couple LUCY with a high-resolution regional chemical transport model to evaluate the impact of AHE on atmospheric environment in Beijing. In areas with high AHE, the 2-m temperature (T₂) increased to varying degrees and showed distinct diurnal and seasonal variations with maxima in night and winter. The increase in 10-m wind speed (WS₁₀) and planetary boundary layer height (PBLH) exhibited slight diurnal variations but showed significant seasonal variations. Further, the systematic continuous precipitation increased by 2.1 mm due to the increase in PBLH and water vapor in upper air. In contrast, the precipitation in local thermal convective showers increased little because of the limited water vapor. Meanwhile, the PM_2.5 reduced in areas with high AHE because of the increase in WS₁₀ and PBLH and continued to reduce as the pollution levels increased. In contrast, in areas where prevailing wind direction was opposite to that of thermal circulation caused by AHE, the WS₁₀ reduced, leading to increased PM_2.5. The changes of PM_2.5 illustrated that a reasonable AHE scheme might be an effective means to improve the performance of PM_2.5 simulation. Besides, high AHE aggravated the O₃ pollution in urban areas due to the reduction in NO_x.     

Characterization of CANON reactor performance and microbial community shifts with elevated COD/N ratios under a continuous aeration mode

COD/N at low ratios (0–0.82) improved N removals of CANON. CANON performance decreased after COD/N up to 0.82. The relative abundance of AOB decreased continuously with increasing COD/N. AOB outcompeted at a high COD load led to CANON failure. The relative abundance of AnAOB decreased and increased with increasing COD/N. The effects of increasing COD/N on nitrogen removal performance and microbial structure were investigated in a SBR adopting a completely autotrophic nitrogen removal over nitrite process with a continuous aeration mode (DO at approximately 0.15–0.2 mg/L). As the COD/N increased from 0.1 to≤0.59, the nitrogen removal efficiency (NRE) increased from 88.7% to 95.5%; while at COD/N ratios of 0.59–0.82, the NRE remained at 90.7%–95.5%. As the COD/N increased from 0.82 to 1.07, the NRE decreased continuously until reaching 60.1%. Nitrosomonas sp. (AOB) and Candidatus Jettenia (anammox bacteria) were the main functional genera in the SBR. As the COD/N increased from 0.10 to 1.07, the relative abundance of Nitrosomonas decreased from 13.4% to 2.0%, while that of Candidatus Jettenia decreased from 35% to 9.9% with COD/N<0.82 then increased to 45.4% at a COD/N of 1.07. Aerobic heterotrophic bacteria outcompeted AOB at high COD loadings (650 mg/L) because of oxygen competition, which ultimately led to deteriorated nitrogen removal performance.     

Enhanced triallyl isocyanurate (TAIC) degradation through application of an O3/UV process: Performance optimization and degradation pathways

• UV/O₃ process had higher TAIC mineralization rate than O₃ process. • Four possible degradation pathways were proposed during TAIC degradation. • pH impacted oxidation processes with pH of 9 achieving maximum efficiency. • CO₃^2– negatively impacted TAIC degradation while HCO₃^– not. • Cl^– can be radicals scavenger only at high concentration (over 500 mg/L Cl^–). Triallyl isocyanurate (TAIC, C₁₂H₁₅N₃O₃) has featured in wastewater treatment as a refractory organic compound due to the significant production capability and negative environmental impact. TAIC degradation was enhanced when an ozone(O₃)/ultraviolet(UV) process was applied compared with the application of an independent O₃ process. Although 99% of TAIC could be degraded in 5 min during both processes, the O₃/UV process had a 70%mineralization rate that was much higher than that of the independent O₃ process (9%) in 30 min. Four possible degradation pathways were proposed based on the organic compounds of intermediate products identified during TAIC degradation through the application of independent O₃ and O₃/UV processes. pH impacted both the direct and indirect oxidation processes. Acidic and alkaline conditions preferred direct and indirect reactions respectively, with a pH of 9 achieving maximum Total Organic Carbon (TOC) removal. Both CO₃^2– and HCO₃^– decreased TOC removal, however only CO₃^2– negatively impacted TAIC degradation. Effects of Cl^– as a radical scavenger became more marked only at high concentrations (over 500 mg/L Cl^–). Particulate and suspended matter could hinder the transmission of ultraviolet light and reduce the production of HO· accordingly.     

Comparison of membrane fouling in ultrafiltration of down-flow and up-flow biological activated carbon effluents

The UF membrane fouling by down- and up-flow BAC effluents were compared. Up-flow BAC effluent fouled the membrane faster than down-flow BAC effluent. The combined effects dominated irreversible fouling. The extent of fouling exacerbated by inorganic particles was higher. The TMP, permeate flux, and normalized membrane flux during 21 days of UF of DBAC and UBAC effluents. Fouling during ultrafiltration of down- and up-flow biological activated carbon effluents was investigated to determine the roles of polysaccharides, proteins, and inorganic particles in ultrafiltration membrane fouling. During ultrafiltration of down- flow biological activated carbon effluent, the trans-membrane pressure was≤26 kPa and the permeate flux was steady at 46.7 L?m⁻²?h⁻¹. However, during ultrafiltration of up-flow biological activated carbon effluent, the highest trans-membrane pressure was almost 40 kPa and the permeate flux continuously decreased to 30 L?m⁻²?h⁻¹. At the end of the filtration period, the normalized membrane fluxes were 0.88 and 0.62 for down- and up-flow biological activated carbon effluents, respectively. The membrane removed the turbidity and polysaccharides content by 47.4% and 30.2% in down- flow biological activated effluent and 82.5% and 22.4% in up-flow biological activated carbon effluent, respectively, but retained few proteins. The retention of polysaccharides was higher on the membrane that filtered the down- flow biological activated effluent compared with that on the membrane that filtered the up-flow biological activated carbon effluent. The polysaccharides on the membranes fouled by up-flow biological activated carbon and down- flow biological activated effluents were spread continuously and clustered, respectively. These demonstrated that the up-flow biological activated carbon effluent fouled the membrane faster. Membrane fouling was associated with a portion of the polysaccharides (not the proteins) and inorganic particles in the feed water. When there was little difference in the polysaccharide concentrations between the feed waters, the fouling extent was exacerbated more by inorganic particles than by polysaccharides.     

Identify the contribution of vehicle non-exhaust emissions: a single particle aerosol mass spectrometer test case at typical road environment

● A single particle observation was conducted in a high traffic flow road environment. ● Major particle types were vehicle exhausts, coal burning, and biomass burning. ● Contribution of non-exhaust emissions was calculated via PMF. ● Proportion of non-exhaust emissions can reach 10.1 % at road environment. A single particle aerosol mass spectrometer (SPAMS) was used to accurately quantify the contribution of vehicle non-exhaust emissions to particulate matter at typical road environment. The PM_2.5, black carbon, meteorological parameters and traffic flow were recorded during the test period. The daily trend for traffic flow and speed on TEDA Street showed obvious “M” and “W” characteristics. 6.3 million particles were captured via the SPAMS, including 1.3 million particles with positive and negative spectral map information. Heavy Metal, High molecular Organic Carbon, Organic Carbon, Mixed Carbon, Elemental Carbon, Rich Potassium, Levo-rotation Glucose, Rich Na, SiO₃ and other categories were analyzed. The particle number concentration measured by SPAMS showed a good linear correlation with the mass concentrations of PM_2.5 and BC, which indicates that the particulate matter captured by the SPAMS reflects the pollution level of fine particulate matter. EC, ECOC, OC, HM and crustal dust components were found to show high values from 7:00–9:00 AM, showing that these chemical components are directly or indirectly related to vehicle emissions. Based on the PMF model, 7 major factors are resolved. The relative contributions of each factor were determined: vehicle exhaust emission (44.8 %), coal-fired source (14.5 %), biomass combustion (12.2 %), crustal dust (9.4 %), ship emission (9.0 %), tires wear (6.6 %) and brake pads wear (3.5 %). The results show that the contribution of vehicle non-exhaust to particulate matter at roadside environment is approximately 10.1 %. Vehicle non-exhaust emissions are the focus of future research in the vehicle pollutant emission control field.     

Characteristic and correlation analysis of influent and energy consumption of wastewater treatment plants in Taihu Basin

Poor biodegradability and insufficient carbon source are discovered from influent. Influent indices presented positively normal distribution or skewed distribution. Average energy consumption of WWTPs in Taihu Basin was as high as 0.458 kWh/m³. Energy consumption increases with the increase in influent volume and COD reduction. The total energy consumption decreases with the NH₃-N reduction. The water quality and energy consumption of wastewater treatment plants (WWTPs) in Taihu Basin were evaluated on the basis of the operation data from 204 municipal WWTPs in the basin by using various statistical methods. The influent ammonia nitrogen (NH₃-N) and total nitrogen (TN) of WWTPs in Taihu Basin showed normal distribution, whereas chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), suspended solid (SS), and total phosphorus (TP) showed positively skewed distribution. The influent BOD₅/COD was 0.4%–0.6%, only 39.2% SS/BOD₅ exceeded the standard by 36.3%, the average BOD₅/TN was 3.82, and the probability of influent BOD₅/TP>20 was 82.8%. The average energy consumption of WWTPs in Taihu Basin in 2017 was 0.458 kWh/m³. The specific energy consumption of WWTPs with a daily treatment capacity of more than 5 × 10⁴ m³ in Taihu Basin was stable at 0.33 kWh/m³. A power function relationship was observed between the reduction in COD and NH₃-N and the specific energy consumption of pollutant reduction, and the higher the pollutant reduction is, the lower the specific energy consumption of pollutant reduction presents. In addition, a linear relationship existed between the energy consumption of WWTPs and the specific energy consumption of influent volume and pollutant reduction. Therefore, upgrading and operation with less energy consumption of WWTPs is imperative and the suggestions for Taihu WWTPs based on stringent discharge standard are proposed in detail.