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There has been controversy regarding the air pollutants emitted from sources closely related to the activities of daily life in China, such as cooking, setting off fireworks, sacrificial incense and joss paper burning, and barbecue (which have been named the five missing sources – FMSs), and the extent to which they impact the outdoor air quality. To date, due to the lack of both an activity dataset and emission factors, there have been no estimations of the emission of air pollutants from FMSs. In this work, we have attempted to combine questionnaire data, various statistical data, and data on points of interest to obtain a relatively complete set of activity data. The emission factors (EFs) of carbonaceous aerosols were tested in our lab. Emission inventories of carbonaceous aerosols with a high spatial–temporal resolution for FMSs were then established, and the spatial variation trend and driving forces were discussed. From 2000 to 2018, organic carbon (OC) emissions were in the range of 4268–4919 t. OC emissions from FMSs were between 1.5 ‰ and 2.2 ‰ of the total emissions in China. Black carbon (BC), elemental carbon (EC), and brown carbon (BrC) absorption cross-section (ACSBrC) emissions from FMSs were in the ranges of 22.6–43.9 t, 213–324 t, and 14.7–35.6 Gm2, respectively. Their emissions tended to be concentrated in certain periods and areas. The OC emission intensities in central urban areas were 3.85–50.5 times those in rural areas (due to the high density of human activity), while the ACSBrC emissions in rural regions accounted for 63.0–79.5 % of the total emissions (resulting from uncontrolled fireworks). A mass of fireworks led to much higher ACSBrC and EC emissions on Chinese New Year's Eve, with respective values that were 1444 and 262 times their corresponding yearly averages. Significant (p<0.01) correlations between the population's income and pollutant emissions were also found: these correlations were positive (r=0.94) and negative (r=-0.94) for urban and rural regions, respectively, indicating the necessity to regulate residents' lifestyles and increase residents' income in respective urban and rural regions. This study provides firsthand data to identify emissions, variation trends, and impacting factors from the FMSs. This is helpful for modeling works on air quality, the climate effect, and human health risks during specific periods or in specific regions as well as for modifying emission control policies. The data compiled in this work can found at https://doi.org/10.6084/m9.figshare.19999991.v2 (Cheng et al., 2022).

The use of organic hole transport layer (HTL) Spiro-OMeTAD in various solar cells imposes serious stability and cost problems, and thus calls for inorganic substitute materials. In this work, a novel inorganic MnS film prepared by thermal evaporation has been demonstrated to serve as a decent HTL in high-performance Sb2(S,Se)3 solar cells, providing a cost-effective all-inorganic solution. A low-temperature air-annealing process for the evaporated MnS layer was found to result in a significant positive effect on the power conversion efficiency (PCE) of Sb2(S,Se)3 solar cells, due to its better-matched energy band alignment after partial oxidation. Impressively, the device with the optimized MnS HTL has achieved an excellent PCE of about 9.24%, which is the highest among all-inorganic Sb2(S,Se)3 solar cells. Our result has revealed that MnS is a feasible substitute for organic HTL in Sb-based solar cells to achieve high PCE, low cost, and high stability.

MoS2 thin film is deposited on ITO/CdS substrate by in-situ hydrothermal method, which is expected to be a potential absorber material for planar heterojunction solar cell due to its high absorber coefficient and carrier mobility. The CdS buffer layer provides a robust template for the quasi-epitaxial growth of MoS2 with (0 0 2) preferred orientation by enjoying the analogical hexagonal structures and the shared sulfur atoms, resulting in a benign interface of CdS/MoS2. Then a device with ITO/TiO2/CdS/MoS2/Carbon-Ag structure is assembled after coating carbon-Ag electrode. The effects of the growth characteristics, morphology changes and optical properties of MoS2 on the device performance are studied systematically. Finally, a primary efficiency of 0.12% is achieved using a P-type MoS2 absorber with a thickness of 305 nm, exhibiting an outstanding stability. The one-dimensional solar cell capacitance simulator (SCAPS) is further used to reveal the bottleneck of device performance. After optimizing the doping density (1 × 1015 cm−3) and defect density (

Hydrothermal deposition is emerging as a highly potential route for antimony-based solar cells, in which the Sb2(S,Se)3 is typically in situ grown on a common toxic CdS buffer layer. The narrow band gap of CdS causes a considerable absorption in the short-wavelength region and then lowers the current density of the device. Herein, TiO2 is first evaluated as an alternative Cd-free buffer layer for hydrothermally derived Sb2S3 solar cells. But it suffers from a severely inhomogeneous Sb2S3 coverage, which is effectively eliminated by inserting a Zn(O,S) layer. The surface atom of sulfur in Zn(O,S) uniquely provides a chemical bridge to enable the quasi-epitaxial deposition of Sb2S3 thin film, confirming by both morphology and binding energy analysis using DFT. Then the results of the first-principles calculations also show that Zn(O,S)/Sb2S3 has a more stable structure than TiO2/Sb2S3. The resultant perfect Zn(O,S)/Sb2S3 junction, with a suitable band alignment and excellent interface contact, delivers a remarkably enhanced JSC and VOC for Sb2S3 solar cells. The device efficiency with the TiO2/Zn(O,S) buffer layer boosts from 0.54% to 3.70% compared with the counterpart of TiO2, which has a champion efficiency of Cd-free Sb2S3 solar cells with a structure of ITO/TiO2/Zn(O,S)/Sb2S3/Carbon/Ag by in situ hydrothermal deposition. This work provides a guideline for the hydrothermal deposition of antimony-based films upon a nontoxic buffer layer.

The less improvement of ambient visibility suspects the government’s efforts on alleviating PM2.5 pollution. The COVID-19 lockdown reduced PM2.5 and increased visibility in Wuhan. Compared to pre-lockdown period, the PM2.5 concentration decreased by 39.0 μg m−3, dominated by NH4NO3 mass reduction (24.8 μg m−3) during lockdown period. The PM2.5 threshold corresponding to visibility of 10 km (PTV10) varied in 54–175 μg m−3 and an hourly PM2.5 of 54 μg m−3 was recommended to prevent haze occurrence. The lockdown measures elevated PTV10 by 9–58 μg m−3 as the decreases in PM2.5 mass scattering efficiency and optical hygroscopicity. The visibility increased by 107%, resulted from NH4NO3 extinction reduction. The NH4NO3 mass reduction weakened its mutual promotion with aerosol water and increased PM2.5 deliquescence humidity. Controlling TNO3 (HNO3 + NO3−) was more effective to reduce PM2.5 and improve visibility than NHx (NH3 + NH4+) unless the NHx reduction exceeded 11.7–17.5 μg m−3.

There has been controversy about the air pollutants emitted from sources closely related to people's daily life (such as cooking, fireworks burning, sacrificial incenses and joss paper burning, and barbecue, named as five missing sources, FMS) impacting the outdoor air quality to what extent. Till now, there is no emission estimation of air pollutants from FMS, as the missing of both activity dataset and emission factors. We attempted to combine the questionnaire data, various statistical data, and data of points of interest to obtain a relatively complete set of activity data. The emission factors (EFs) of carbonaceous aerosols were tested in our lab. Then, the emission inventories of carbonaceous aerosol with the high spatial-temporal resolution for FMS were established firstly, and the spatial-variation trend and driving forces were discussed. From 2000 to 2018, organic carbon (OC) increased from 4268 t to 4919 t. The OC emission from FMS was 1.48–2.18 ‰ of its total emission in China. The emissions of black carbon, element carbon (EC), and brown carbon absorption cross-section (ACSBrC) emissions from FMS were in the ranges of 22.6–43.9 t, 213–324 t, and 14.7–35.6 Gm2, respectively. Their emissions tended to concentrate in special periods and areas. The OC emission intensities in central urban areas were 3.85–50.5 times that of rural areas due to the high density of human activities. While the ACSBrC emissions in rural regions accounted for 63.0–79.5 % of the total emission result from uncontrolled fireworks burning. A mass of fireworks burning led to extremely higher ACSBrC and EC emissions on Chinese New Year’s eve, as 1444 and 262 times their corresponding yearly average values. Interestingly, significant (p

Antimony chalcogenide Sb2(S, Se)3 is attracting a lot of attention as photovoltaic absorber owing to its rewarding photoelectric properties, low toxicity, and earth abundance. However, its device efficiency is still limited by the absorber material quality and device interface recombination. In this work, a fluorine-doped tin oxide (FTO) substrate with ultra-thin SnO2 layer and a low-cost stabilized carbon paste are introduced as a front and back contact layer respectively in Sb2(S, Se)3 based planar solar cells. Over 5.2 % efficiency is demonstrated in the structure of FTO/SnO2/CdS/Sb2(S, Se)3/Carbon/Ag, where the Sb2(S, Se)3 is prepared by hydrothermal technique. The complementary device physics characterizations reveal that the interfacial recombination between TCO and CdS is significantly suppressed by the introduction of ultra-thin SnO2 layer, which is profited from the leakage protection and bandgap offset engineering by its high resistivity and suitable conduction band minimum. Meanwhile, the successful adoption of the low-cost stabilized carbon as a back contact here shows an enormous potential to replace the conventional organic hole transport materials and noble metal. We hope this work can provide positive guidance to optimize Sb2(S, Se)3 based planar solar cells in the future.

Atmospheric ammonia (NH

The use of organic hole transport layer (HTL) Spiro-OMeTAD in various solar cells imposes serious stability and cost problems, and thus calls for inorganic substitute materials. In this work, a novel inorganic MnS film prepared by thermal evaporation has been demonstrated to serve as a decent HTL in high-performance Sb

In this work, a three-step (sulfurization-selenization-sulfurization) annealing process was designed to optimize the surface constitution of Cu2ZnSn(S, Se)4 (CZTSSe) thin films, which was prepared by oxide nanoparticles-based approach. The devices with the Mo/CZTSSe/CdS/ZnMgO/ZnO:Al/Al structure were fabricated and their performances were studied. The additional post-sulfurization with low toxicity sulfur powder has negligible impact on the structure, morphology and composition of CZTSSe bulk, however, it improves open circuit voltage of device significantly. The open circuit voltage can be increased significantly from 408 mV (without surface sulfurization) to 497 mV (with surface sulfurization). This is benefited from the increase of surficial sulfur content and the broadening of the surface band-gap of the CZTSSe thin film. The result is confirmed by X-ray photoelectron spectroscopy analysis. Such a crucial three-step annealing process promotes the power conversion efficiency from 4.71% (2-step) to 6.37% (3-step), which is the champion efficiency of oxide precursor derived CZTSSe solar cell.

Residential coal combustion is one of the main sources of ambient polycyclic aromatic hydrocarbons (PAHs). Updating its emission estimation is limited by the shortages of emission factors, especially for them in different particle sizes and from different combustion conditions. PAH emission factors (EFs) for nine size-segregated particle segments emitted from smoldering and flaming combustion of residential coals (four kinds of raw coals (RCs) and three kinds of honeycomb coal briquettes (HCBs)) were obtained in China, using a dilution sampling system. EFs of PAHs for the flaming and smoldering of HCB ranged from 1.32 to 2.04 mg kg−1 and 0.35 to 5.36 mg kg−1, respectively. The EFs of PAHs for RC flaming combustion varied from 0.50 to 218.96 mg kg−1. About 53.5–96.4% and 47.4–90.9% of PAHs concentrated in PM2.1 and PM1.1, respectively. Different fuel types and combustion conditions strongly affected the PAH EFs. The PAH EF for the RC was 0.3 times that for HCB in Guizhou, which implied that PAH EFs for RC combustion were not always higher than those from HCB burning. For different combustion conditions, the PAH EFs from flaming were more than 2.5 times higher than those from smoldering for HCB except in the Anhui region. Results indicated that current PAH EFs may not be universal, which may bias the establishment of control policies for toxic pollutants emitted from domestic coal burning. On average, 73.2 ± 15.5% of total PAH potential toxicity risks were concentrated in submicron particles. More size-segregated PAH EFs for residential coal combustion should be investigated considering combustion conditions with a uniform sampling method in China.

Residential coal combustion (RCC) emission exhibited obvious daily variation, while no real-time estimation of air pollutants from RCC has been reported, as the shortages of corresponding activity dataset and emission factors with high time resolution. A real-time monitoring platform for RCC emission was established. Hourly emission factors of 18 typed of TEs from eleven kinds of chunk coals and nine kinds of honeycomb coals burning in China were obtained. The monthly and hourly coal consumption amounts were calculated with reference and our field survey. Then the hourly TEs emission inventories from RCC were established in China. GEOS-Chem and Risk Quotients Models were utilized to map the spatialized health risks of hazardous elements, including the gridded hazard index and carcinogenic risk. The result indicated that the EFs of TEs would be underestimated if the tests only consider flaming conditions. Cu, K, Ca, Zn, and Co were the top five elements from RCC, with corresponding emission amounts as 1397.7, 1054.0, 676.0, 623.5 and 420 tons in 2017, respectively. K, Ti, Fe, Sn, and Sb showed hourly peak values under flaming dominated periods, accounting for 48.2%, 45.9%, 31.8%, 42.8%, and 33.8% of their daily emissions. Other elements (e.g., V, Co, As, Hg and Pb) exhibited higher emissions under smoldering dominated period in nighttime, accounting for 22.2%, 32.9%, 27.6%, 34.7%, and 28.4% of their daily emissions. TEs emission from RCC closely follows the habits of human daily cooking and heating activity. The national HI were lower than the acceptable level (HI ≤ 1) except Sichuan Province (up to 1.2). Higher carcinogenic risks (≥1 × 10-6) occurred in parts of Sichuan, Shanxi, Hunan and Hubei, which were up to 2.0 × 10-5. The high-resolution TEs emission inventories could be useful for future modeling works on the formation and evolution of air pollution and are helpful for human exposure assessment.

Accurate source markers, source profiles and species-based emission factors (EFs) are currently the key limitations for source apportionment and emission inventory researches. Fine particles (PM2.5) were collected from stack gases of eight types of stationary sources with a dilution sampling system. The mass percentages and EFs of 89 kinds of chemical species in PM2.5 including water-soluble ions, elements, carbonaceous species and molecular organic species were obtained. Results showed that water-soluble ions (8%–54%) and elements (5%–45%) were the dominant chemical species. Palmitic acid (0.19%–0.62%) and stearic acid (0.21%–0.59%) were the most abundant organic species. PM2.5 source profiles of the eight sources were different from each other with the coefficient of divergence values all higher than 0.4. The addition of organic species could help to further distinguish them. The indicatory chemical components and specific species ratios were obtained by both a statistical equation and randomForest. These indicatory chemical components (e.g. F− for glass factory) and species ratios (e.g. K+/Mg2+ & OC/Mg for pharmaceutical factory) improved the current knowledges of their indicatory performance in source identification of ambient PM2.5. The EFs of PM2.5 from the eight stationary sources ranged from 0.019 to 51.6 kg t−1 of fuel used. The EFs of PM2.5 from the pharmaceutical factory were about 70–2600 times higher than other seven types of sources due to the lack of dust-removing devices. Certain EFs measured in this study were about 10–36,000 times lower than corresponding EFs estimated in previous studies which didn't perform field measurements, indicating the necessity for improving emission inventories continuously. This study contributes to identifying emission sources of PM2.5 especially for subtypes of stationary sources and to establishing species-based emission inventories.

Atmospheric ammonia (NH3) is one of the most crucial precursors of secondary inorganic aerosols. However, its emission control is still weakness over China. NH3 emission inventories of 2015 with and without considering a set of refined emission reduction strategies covering seven major NH3 emission sources were constructed in Central China. GEOS-Chem model simulations were conducted to quantify the benefits of NH3 emission reduction on PM2.5 mitigation in four typical months (January, April, July and October). The results showed that these control strategies could reduce approximately 47.0% (152 Gg) of the total NH3 emissions in Hubei Province, with the agricultural (livestock and fertilizer application) source being reduced the most (133 Gg). NH3 had a significant nonlinear relationship with sulfate, nitrate, ammonium and PM2.5. NH3 emission reduction exerted less effect on sulfate mitigations (the annual average sensitivity was 4.5%), but it obviously alleviated nitrate, ammonium and thus PM2.5, with the annual average sensitivities of 81.9%, 34.8% and 22.0%, respectively. The average provincial concentrations of PM2.5 were alleviated by 11.2% in January, 10.6% in October, 10.2% in April and 9.3% in July through NH3 emission reduction by 47.0%. The reduction benefits were more pronounced in high NH3 emission areas, such as Yichang, with the PM2.5 reduction of 14.4% in January. This research could provide scientific support for formulating NH3 emission reduction policies to further mitigate PM2.5 pollution.

Residential coal combustion (RCC) emission demonstrates obvious daily variation, while no real-time estimation of air pollutants from RCC has been reported, as the limitation of hourly activity data and emission factors. With a dilution sampling system, a high-precision electronic balance, and an Aethalometer Model AE33, a real-time monitoring platform for RCC emission was established. Hourly emission factors (EFs) of BC and absorption emission factors (AEFs) of BrC from eleven kinds of chunk coals and nine kinds of honeycomb coals burning in China were obtained. The monthly and hourly coal consumption amounts were calculated with the activity data from literature reviews and a field survey. The first hourly BC and absorption cross section of BrC emission inventories from RCC were established in China. The historical emission trends (2003–2017) indicated that the policy has rapidly controlled the emission of BC and ACSBrC from RCC in urban area (26.7% and 31.8% decreased, respectively in 2013). While in rural areas, their emission continually increased by 1.2% ~ 5.3% until more strict law enacted in 2017. Emissions of BC and ACSBrC in winter seasons were 60.1 Gg and 1064.1 Gm2, which accounted for 54.3% and 55.1% of the total BC and ACSBrC emissions correspondingly. The peak values of hourly emission of BC and ACSBrC (in 370 nm) normally appeared at 19:00–23:00, accounting for 43.0% and 41.5% of their total daily emission. The low emission periods were at cooking times including 7:00, 12:00, and 17:00 of a day and the whole emission of BC and ACSBrC for the three periods accounted for 1.8% and 2.3% of their daily emission. This high-resolution BC and ACSBrC emission inventories can be useful for future modeling works on the formation and evolution of a haze event, the smoke aging and transportation, as well as corresponding climate and human health effects.

Germanium selenide (GeSe), a IV-VI chalcogenide containing earth-abundant and low-toxic elements, has attracted increasing interest as a potential absorber material for photovoltaics due to its excellent optical and electrical properties. In this work, a simple and effective magnetron sputtering method was proposed to deposite GeSe precursor thin films using GeSe alloy target. Subsequently, the as-deposited samples were post-annealed in vacuum atmosphere. The effects of different annealing temperatures on crystallinity, morphology and phase transformation of the as-prepared films were systematically investigated. It has been revealed that phase-pure and uniform GeSe thin films were obtained through the self-decomposition of slight GeSe2 impurity at 400 °C. Finally, a prototypical FTO/CdS/GeSe/C-Ag solar cell with 220 mV open circuit voltage and 0.05% power conversion efficiency was fabricated, which suggests the potential of sputtering processed GeSe thin film for low cost solar cell.

Ternary Cu2SnS3 (CTS) thin films have attracted lots of attention due to its low cost, nontoxic element for solar cell. However, Tin losses always happen during sulfurization, which will affect the phase purity and morphology of CTS thin films and relevant solar cell. In this work, a low cost oxides route was used to prepare CTS thin films. The influences of sulfurizaton temperature on the crystal structure, morphology and composition were studied carefully. From the XRD, SEM and EDX results, it was found that the stable oxides were conducive to alleviate the Sn loss even at the higher sulfurization temperature (580 °C). Meanwhile, the crystal structure evolution along annealing temperature was also observed from mixed phase (Monoclinic and Tetragonal) to single phase Monoclinic. The Monoclinic CTS thin films sulfurized at 580 °C were used to fabricate CTS solar cell with Mo/CTS/CdS/ZnO/AZO/Ag structure, exhibiting efficiency of 0.16%. The comparable Voc of 300 mV was achieved by benefiting from the precise composition control. Besides, the photoelectric properties of the device were carefully studied as well. This study provides a low-cost and facile strategy for the fabrication of Sn-loss free CTS solar cells.

Groundwater contamination with high arsenic (As) levels has caused serious health problem in Jianghan Plain. This study presents a framework to evaluate the results and their probable influencing factors of non-carcinogenic risk and carcinogenic risk in Shahu Village. An appropriate health risk assessment for residents exposing to As through ingestion and dermal contact pathways is also discussed in the paper. Hazard quotient (HQ) and target cancer risk (TR) are adopted to compute the non-carcinogenic and carcinogenic effects for residents, respectively. Monte Carlo simulation technique is used to quantify the uncertainty of the risk assessment. The assessment results show that the HQs and TRs of 10-m-deep and 25-m-deep wells exhibit seasonal variations with higher values in rainy season and lower values in dry season. The HQ values exceeding 1 at the depths of 10 (from 0.09 to 23.21 m) and 25 m (from 0.29 to 130.55 m) account for 61 and 94%, respectively, which associate with the As contents distribution in the aquifer sediments. The estimated TR values at the depths of 10 (from 3.86E−05 to 1.04E−02) and 25 m (from 1.32E−04 to 5.87E−02) exceeding the highest acceptable standard (10−4) account for 95 and 100%, respectively. Comparison of the two exposure pathways, the ingestion exposure contributes much more than the dermal contact exposure for both non-carcinogenic risk and carcinogenic risk. The results of sensitivity analysis indicate that a more accurate measurement and better definition of probability distributions for As concentration in the groundwater can increase the accuracy of health risk assessment in Jianghan Plain. The findings demonstrate the importance of the drinking water safety, and the government should take measures to ensure the drinking water safety.

The inhibition and removal of the SnS2 impurity phase in the kesterite Cu2ZnSnS4 (CZTS) layer is a major challenge for the improvement of CZTS solar cells; this impurity phase can critically damage device performance by forming a diode and a barrier for carrier collection. However, the formation and growth mechanism of SnS2 is incomplete and the common etching treatment with (NH4)2S is problematic because of its toxic characteristics. In this study, the formation and growth of large-size SnS2 sheets were observed to occur on the surface of the CZTS thin film via condensation during the cooling process. Sequently, a novel and benign peeling process was carried out using a sticky tape to effectively remove the SnS2 formed on the surface, resulting in a uniform CZTS thin film. A maximum efficiency of 4.3% of the oxides-derived CZTS device was obtained after this mechanical exfoliation, which is nearly eleven times that of the device without stripping. It was confirmed that this surface treatment is an effective and green way to remove the SnS2 impurity, which largely improved the performance of the CZTS device and may guide the preparation of pure phase CZTS thin films.

The earth-abundant material CuSbS2 (CAS) exhibits excellent optical and electrical properties as a potential absorber material for thin-film solar cells. However, the preparation of phase-pure CAS is still challenging due to the multi-phase characters of Cu-Sb-S system and antimony (Sb) loss during the annealing. In this work, an oxides nanoparticles-derived route is first investigated to synthesize CAS thin film. The Sb loss can be alleviated slightly by increasing sulfurization pressure. To control the film composition and phase purity, the effect of Cu/Sb ratios on the phase evolution is carefully investigated, and phase formation mechanism is then well established. Finally, the phase-pure CAS thin film with large grains is prepared with the sufficient Sb provided as a sacrificial material. An obvious photoelectric response of CAS thin film and its related solar cell are observed, suggesting a potential strategy for the fabrication of CAS solar cells from oxides nanoparticles ink.

Petrochemical industry (PI) is an important emission sector of anthropogenic volatile organic compounds (VOCs). The health impacts of VOCs from PI have caused a wide attention by both scientists and publics. In this study, compositions, sources and health risks of VOCs at a typical petrochemical industrial park along the middle reach of Yangtze River were studied. The total VOC concentrations were in the range of 5.59 to 541 ppbv with a mean value of 54.8 ppbv. Alkanes (41.4 ± 15.7%) were the predominant group, followed by alkenes (19.9 ± 18.3%), OVOCs (14.7 ± 9.26%), halo hydrocarbon (11.2 ± 6.42%), aromatics (8.17 ± 5.08%), and acetylene (4.54 ± 2.80%). Compound-specific health risk results showed that acrolein and 1,3-butadiene had the highest non-carcinogenic risk (expressed by hazard ratio, HR: 22.8) and carcinogenic risk (expressed by lifetime cancer risk, LCR: 6.7 × 10−3), respectively. Positive matrix factorization (PMF) model identified four VOC sources including fuel evaporation, industrial sources, ethylene industry and regional background with the average contributions of 35.6%, 12.0%, 26.5% and 25.9%, respectively. The receptor-originated approach combining the PMF model and conventional methods (HR and LCR) was used to assess the source-specific health risks. The non-cancer risks of four VOC sources were above safe level with regional background contributing most (38.3% or 4.91) to HR. The cancer risks of the four sources were below the tolerable level (

GeSe is considered as a potential absorber material for thin film solar cells owing to its ideal band gap, strong light absorption, remarkable air durability, Earth-abundance and non-toxic constituents. However, the high vapor pressure of GeSe at a temperature below its melting point makes it difficult to synthesize a high-quality GeSe film. To alleviate this limitation, in this work, a thermal evaporation combining a novel sandwiching post-annealing method was introduced to deposit high quality GeSe thin films with (100)-orientation. The self-assembling mechanism of the highly oriented GeSe film was carefully investigated by the systematic experiments and confirmed by the lowest total energy of the (100) crystal plane. Finally, the fully-inorganic, low-cost and non-toxic planar device with the superstrate configuration of FTO/TiO2/GeSe/carbon/Ag was also successfully fabricated. Notably, as a result, an impressive open circuit voltage (VOC) of 340 mV (maximum: 456 mV) was achieved, which is the highest VOC of GeSe solar cells reported so far. Furthermore, through current-voltage, capacitance-voltage profiling and drive level capacitance profiling measurements, it was demonstrated that the limiting factors of the GeSe solar cell performance were the narrow depletion width (138 nm) and the drastic recombination at the TiO2/GeSe interface.

Molecular solution with the metal-thiourea complex is a facile and effective route for Cu2SnS3 (CTS) thin film deposition. However, its stability is still challenging due to flexible metal salts precursors. Here we report a strategy to enhance the stability of the Cu–Sn–S molecular solution that use bivalent Sn to suppress the oxidation of the S2- of thiourea via the redox reaction. The self-stabilizing mechanism has been carefully revealed by the systematic experiments and confirmed by the spontaneous reaction process of metal-thiourea system. It demonstrates that Sn with a low valence state weakens the transfer of lone pair electrons from thiourea to Cu2+ and Sn4+ ions, alleviating the sulfur precipitates from thiourea oxidation because of the easily reducible character of Sn2+ ion. The solution with Sn2+ antioxidant additive can be stored for a long time under air ambient, which is then spin-coated and sulfurized with Sn powder compensation. The uniform CTS thin film with composition control is finally achieved and delivers a device efficiency of 1.15%. This work provides a guide on stabilizing the solution precursor for chalcogenide thin film deposition.

Aerosol size distribution, chemical components and their mixing state are key factors impacting the optical properties of aerosols. The researches on optical properties closure and sources for size-segregated aerosols are still scattered. A sampling campaign covering a summer harvest period was conducted in Nanjing, considering the influence of open biomass burning (BB) on optical properties of size-resolved aerosol. Two parallel FA-3 samplers were employed to collect nine size-segregated particles (0.43–10 μm), with water-soluble ions, carbonaceous components and elements analyzed. Aerosol light absorption (bap) and scattering (bsp) coefficients were synchronously online monitored. Results indicated that sulfate, nitrate and ammonium (SNA), crustal materials (CM) and organic matter (OM) were the main contributors of aerosol mass, totally accounting for 61.3%–81.4%. On hazy days, PM1.1 occupied 82.3% of the total estimated bsp by Mie model, with SNA and OM accounting for 40.9% and 16.2%, respectively. PM1.1 contributed 61.7% of the total estimated bap with EC accounting for 41.6%. Positive matrix factorization modeling indicated that vehicle emission contributed most (13.1%–52.9%) to bap especially for particles with diameter smaller than 0.43 μm. On hazy days, BB was the main source for bsp, contributing to 24.7% (for particle within 1.1–2.1 μm)-38.2% (0.65–1.1 μm), then followed by secondary inorganic aerosol, contributing to 16.3% (1.1–2.1 μm)-18.8% (0.65–1.1 μm). For the summer harvest period, the open BB impacts obviously on bsp rather than bap, promoting the haze formation. The temporal variations of aerosol externally mixed ratio and significant negative correlations between the mixed ratio and OC/EC also verified that fresh BB emissions deteriorated the visibility. This study highlights the different roles of aerosol chemical components and emission sources impacting optical properties for size-resolved aerosols, which is helpful to give more accurate visibility improvement strategies.

The absence of emission factors (EFs) with high-time resolution primarily hinders developing high time-resolution emission inventory for air pollutants, which further restricted the accuracy of air quality modeling, especially for a pollution process. The real-time emission concentration of volatile organic compounds (VOCs) in the combustion process of eleven kinds of residential biomass fuels (RBFs) were studied using a high-resolution proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS). The dynamic EFs for 18 types of VOCs were firstly obtained with the records of fuel consuming amounts by a balance of high precision. The RBFs burning lasted for about 3–15 min for each experiment with 53–130 g fuels burned. The VOCs concentrations of biomass combustion varied in 0–10 ppm, and exhibited single peak values at about 1–4 min for the entire burning processes. Aldoketones accounted for the largest proportion of the 18 types of VOCs (46.6%–53.6%), followed by methanol (29.2%–44.6%) and alkene (26.2%–31.7%). The real-time EFs of VOCs from RBFs burning firstly decreased to the lowest value of 0.001–3.84 mg/g, and then increased to about 0.23–148 mg/g until the end of combustion processes. The VOCs EFs of all biomass combustion in flaming (1.65 ± 1.55 mg/g) were lower than those in smoldering (16.0 ± 11.3 mg/g). The benzene to toluene (B/T) ratios peaked at 100–200 s of biomass burning processes and changed in 0.07–4.06 for different burning stages. It should be noted that isoprene which was always regarded as the marker for VOCs emitted from biogenic evaporation, can also be released from biomass fuels burning, with real time EFs of 3.16 ± 5.16 mg/g. Its emission amounts and relative importance from combustion sources should be assessed. The high time-resolution of VOCs emission concentrations, emission factors and specific species ratios provide new datasets. They would be useful for dynamic source apportionment and developing high-time resolution emission inventory of VOCs.

Source profiles of volatile organic compounds (VOCs) emitted from the evaporation of various fuels, industrial raw materials, processes and products are still limited in China. The impact of ambient temperature on the VOC released from these fugitive emission sources has also been rarely reported. In order to establish VOC source profiles for thirteen volatile emission sources, a sampling campaign was conducted in Central China, and five types of sources were investigated both in winter and summer. The dominant VOC groups varied in different sources, and they were alkanes (78.6%), alkenes (53.1%), aromatics (55.1%), halohydrocarbons (80.7%) and oxygenated VOCs (OVOCs) (76.0%), respectively. Ambient temperature showed different impacts on VOC source profiles and specific species ratios. The mass percentages of halohydrocarbons emitted from color printing and waste transfer station in summer were 42 times and 20 times higher than those in winter, respectively. The mass percentages of OVOCs emitted from car painting, waste transfer station and laundry emission sources were much higher in summer (7.9-27.8%) than those in winter (0.8-2.6%). On the contrary, alkanes from color printing, car painting and waste transfer stations were about 11, 4 and 5 times higher in winter than those in summer, respectively. The coefficient of divergence values for the source profiles obtained in winter and summer ranged in 0.3-0.7, indicating obvious differences of source profiles. Benzene/toluene ratio varied in 0.00-0.76, and it was in the range of 0.02-0.50 in winter and 0.04-0.52 in summer for the same sources, respectively. Hexanal, isobutene, m,p-xylene, toluene, 2-methylacrolein, styrene, 1-hexane and cis-2-butene dominated the ozone formation potentials (OFP). The OFP summer/winter differences were 5-320 times by MIR method and 1-79 times by Propy-Equiv method, respectively. This study firstly gave direct evidence that ambient temperature modified the mass percentages of VOC species obviously. It is important for improving VOC source apportionment and chemical reactivity simulation.

Mitigation of ozone in urban agglomerations of developing countries remains challenging, due partly to inadequate knowledge of the relative importance of local sources versus transboundary transport, aggravated by lack of synchronous measurements of ozone and precursors. Here we investigate the spatial-temporal characteristics of ozone and its precursors measured synchronously at five cities of Wuhan City Cluster (WCC) in Central China during the high-ozone months of May–June 2018, facilitated by multiple models of different complexities. We find substantial cross-city diversities in the measured maximum daily averaged 8-h (MDA8) ozone, nitrogen oxides (NOx = NO + NO2), volatile organic compounds (VOCs), VOCs/NOx ratios, and ozone formation potentials of VOCs, which are tied to distinctive local emission sources. GEOS-Chem simulations suggest that local anthropogenic emissions contribute 26.8–29.5% of ozone in each city averaged over May–June 2018, with higher values during ozone episodes (up to 32.0%). Transboundary transport from non-WCC Asian regions (18.5–19.2%) contributes much more than cross-city transport within WCC (2.5–3.1%) to ozone concentrations in the five cities. The contributions of background ozone from non-Asian anthropogenic emissions and global natural sources reach 48.9–51.6%. Thus local mitigation actions alone can substantially reduce city-level ozone; whereas the majority of ozone must be mitigated by country-wide or worldwide collaborations. Collaborations within an urban agglomeration alone may not effectively mitigate ozone.

After releasing the Air Pollution Prevention Control and Action Plan (APPC) in China since 2013, the role of source emission control strategies and meteorological conditions on the reduction of air pollutants has received wide attention. Using an Aethalometer (AE31), equivalent black carbon (eBC) was monitored for 5.5-year after the APPC at Wuhan, a megacity in Central China, to identify its levels, sources, and variations trends. eBC varied in the range of 0.03–12.3 μg m−3, with the highest and lowest values in January (1.98 ± 1.70 μg m−3) and July (0.87 ± 0.61 μg m−3), respectively. The Kolmogorov-Zurbenk (KZ) filter and multiple-linear-regression were adopted to isolate the impacts of source emission control strategies and meteorological conditions on eBC variation. A long-term linear trend showed that emission-related reduction (7.79% yr−1) rather than meteorology-related reduction (4.51% yr−1) dominated the decreasing of eBC in the past years. Combining the KZ filter and Aethalometer model, the trends of eBC from fossil fuel combustion (eBCff) and biomass burning (eBCbb) were calculated. eBCbb and eBCff both showed decreasing trends with the reduction rates of 7.78% yr−1 and 7.76% yr−1, respectively. Backward trajectory analysis indicated that the air masses transported to the observational site from different regions in China all showed decreasing trend (1.64–18.7% yr−1) for eBC due to both the reduction from eBCbb (5.74–16.0% yr−1) and eBCff (7.38–19.7% yr−1), suggesting the positive role of pollution control measures in migrating air pollution across China.

Wuhan was the first city to adopt the lockdown measures to prevent COVID-19 spreading, which improved the air quality accordingly. This study investigated the variations in chemical compositions, source contributions, and regional transport of fine particles (PM2.5) during January 23–February 22 of 2020, compared with the same period in 2019. The average mass concentration of PM2.5 decreased from 72.9 μg m−3 (2019) to 45.9 μg m−3 (2020), by 27.0 μg m−3. It was predominantly contributed by the emission reduction (92.0%), retrieved from a random forest tree approach. The main chemical species of PM2.5 all decreased with the reductions ranging from 0.85 μg m−3 (chloride) to 9.86 μg m−3 (nitrate) (p, Graphical abstract Unlabelled Image, Highlights • Differences in PM2.5 chemical species and sources since lockdown were reported. • Primary emission reduced while secondary formation enhanced since lockdown. • Emission reduction dominated the improvement of air quality in Wuhan during lockdown.

The contributions to aerosols and major chemical compositions (e.g. water-soluble ions-WSIs) from residential coal combustion (RCC) are still now existing large uncertainty in air quality modeling. The lake of reliable emission inventories for primary WSIs from RCC in China with measured emission factors (EFs) adopted is a major obstacle. With simulating burning test and dilution sampling method, this study detected the emission factors of nine size-segregated aerosols (0.43–10 μm) and associated WSIs emission factors from residential honeycomb briquettes and chunk coal burning, considering smoldering and flaming combustion status. Then a 1 km × 1 km grid cell-based emission inventory of RCC, including size-segregated particles and associated WSIs in China was established. The contributions of RCC to ambient fine particles were estimated by GEOS-Chem model. Results indicated that compared with anthracite coal combustion emission, bituminous coal burning emission can reduce the EFs of particles, while may increase the EFs of WSIs. The averaged EF of WSIs from honeycomb coal combustion was found 1.15 times higher than those for chunk coal burning. The total emission amounts of NH4+, Na+, K+, Mg2+, Ca2+, Cl−, NO3− and SO42− in PM2.1 from residential coal combustion in 2015 were 1915.3, 101.8, 1180.8, 50.1, 96.8, 4956.1, 552.4 and 7430.3 t, respectively, totally accounting for 2.03% of PM2.1. SO42− was the most important WSIs in fine particles released from RCC, occupied by 45.6% of the total WSIs. GEOS-Chem simulation indicated that RCC emission in China averagely accounted for 25.7% of ambient PM2.5 and 7.1% for sulfate. Our results show that RCC emission is an important source for primary PM2.5 and sulfate, suggesting the primary emission of WSI should be included in air quality modeling. More EFs monitoring of RCC of different types and regions in China should be conducted, for updating emission inventory and optimizing modeling results.

Black carbon (BC), from the incomplete combustion sources (mainly fossil fuel, biofuel and open biomass burning), is chemically inertness and optical absorbance in the atmosphere. It has significant impacts on global climate, regional air quality, and human health. During the transportation, its physical-chemical characteristics, optical properties and sources would change dramatically. To investigate the BC properties (i.e., mass concentration, sources and optical properties) during the intra-regional transport between the south edge of North China Plain (SE-NCP) and Central China (CC), simultaneous observations of BC at a megacity (Wuhan, WH) in CC, three borderline cities (Xiangyang, XY, Suixian, SX and Hong'an, HA, distributing from the west to east) between SE-NCP and CC and a city (Luohe, LH) in SE-NCP were conducted during the typical winter haze episodes. Using Aethalometer, the highest equivalent BC (eBC) mass concentrations and aerosol absorption coefficients (σabs) were found in the city (LH) at SE-NCP, followed by the borderline cities (XY, SX and HA) and megacity (WH). The levels, sources, optical properties (i.e., σabs and absorption Ångström exponent, AAE) and geographic origins of eBC were different between clean and pollution episodes. Compared to clean days, the higher eBC levels (increased by 26.4–163 %) and σabs (increased by 18.2–236 %) were found during pollution episodes due to more combustion of fossil fuel (contributing for 51.1–277 %), supported by the decreased AAE (by 7.40–12.7 %). Non-parametric wind regression (NWR) and concentration-weighted trajectory (CWT) results showed that the geographic origins of biomass burning (BCbb) and fossil fuel (BCff) combustion derived BC were different. Based on cluster analysis of trajectories, air parcels from south direction dominated for border sites during clean days, with contributions of 46.0–58.2 %, while trajectories from the northeast had higher contributions (37.5–51.2 %) during pollution episodes. At the SE-NCP site (LH), transboundary influences from south direction (CC) exhibited more frequent impact (with the air parcels from this direction contributed 47.8 % of all the parcels) on the ambient eBC levels during pollution episodes. At WH, eBC was mainly from the northeast transport route during the whole observation period. Two transportation cases showed that from upwind to downwind direction, the mass concentrations of eBC, BCbb and BCff all increased, while AAE decreased. This study highlighted that intra-regional prevention and control for dominated sources of specific sites should be considered to improve the regional air quality.

East Lake is a shallow lake (in Wuhan, China) where cyanobacteria blooms occurred frequently from 1970 to 1985. During the study period, all Carlson trophic state index values were > 50, indicating that East Lake is in a eutrophic state. In this study, phycocyanin concentrations were measured through phycocyanin fluorometry for rapid assessment of cyanobacterial abundance. The smoothing splines of the optimal generalized additive model (GAM) indicated that Secchi depth (SD), total phosphorus (TP) and dissolved oxygen (DO) concentrations, electrical conductivity (EC), chemical oxygen demand (COD), and ratios of total nitrogen (TN) to TP (TN:TP) were the main environmental factors in a moderate nonlinear relationship with cyanobacterial phycocyanin concentrations in East Lake. The shape of the GAM smoother can be used to quantify the relationship between a response variable and an explanatory variable in the scatterplot. Phycocyanin concentrations were sharply and negatively related to both SD and EC when the SD was 20–80 cm and EC was > 270 mg/L. Phycocyanin concentrations increased with concentrations of TP, DO, and COD. Phycocyanin concentrations increased sharply with TP concentrations when TP concentrations were > 0.10 mg/L and approached to a constant when DO concentrations were > 8.20 mg/L. Approximately, 85% of the phycocyanin concentrations were negatively correlated with TN:TP of

To meet high performances of automotive time-triggered CAN (TTCAN) real-time control bus, a key problem is how to distribute time windows within system matrix of TTCAN, a new harmonic periods makeup (HPM) scheduling optimization algorithm based on average loading was proposed and the scheduling strategy was explained concretely. The HPM scheduling algorithm aimed to make event-triggered messages gain the maximum transmission times by minimizing the space occupied by time-triggered messages. A scheduling tool for TTCAN networks that generates a valid scheduling table using HPM was presented. Finally, a PSA message set is introduced to validate the algorithm,through optimization for the message set, the time performances of event triggered messages and then the whole system performances get improved.