Atmospheric nitrous oxide (N2O) is one of the principal greenhouse gases and the largest ozone-depleting substance in the stratosphere. The growth of the atmospheric N2O burden has been mainly attributed to emissions from agricultural fields. However, N2O emissions measured by using conventional static chambers (CSCs) usually suffer from serious artifacts that influence the estimations of the global N2O budget. In this study, N2O fluxes from an agricultural field in the North China Plain (NCP) were comparably measured by using CSCs, CSCs with dehumidification, and open-top dynamic chambers (OTDCs) to reveal the artifact of humidity accumulation inside CSCs on N2O emissions. The air relative humidity and topsoil moisture inside the CSCs were found to be significantly higher than those inside the OTDCs and over/in the field, leading to the CSCs' overestimation of N2O emissions by factors of 2.3-3.6. The overestimation of N2O emissions by CSCs was further verified by soil simulation experiments in a flow tube by flushing the soil with varying air humidity. The results of this study underscore that future efforts should prioritize validating the estimates of N2O emissions from key sources using minimally intrusive methods like dynamic chambers or micrometeorological methods.

Carbonyl compounds are significant in atmospheric chemistry and human health, yet their sources, especially in rural areas, remain incompletely characterized. Long-term measurements (June 2020-July 2021) at a rural site in the North China Plain (NCP) identified formaldehyde, acetaldehyde, and acetone as the dominant carbonyls, collectively accounting for 71 % of the total. Concentrations exhibited distinct seasonal patterns, with the highest levels observed for all three compounds during autumn. Analysis of C1/C2 ratios and correlation analysis indicated anthropogenic emissions as the primary source overall. Notably, during autumn, strong mutual correlations among formaldehyde, acetaldehyde, and acetone were observed, contrasting with weaker correlations to CO and O3. Supplementary experiments confirmed that mechanical corn stover crushing releases substantial amounts of carbonyls. These convergent findings demonstrate that large-scale seasonal agricultural activities, particularly corn stover crushing and agricultural machinery during harvest periods, constitute a major and previously underappreciated source of carbonyl emissions in the NCP region, necessitating greater attention in emission inventories and mitigation strategies. Furthermore, integrated lifetime cancer risk (ILTCR) and hazard quotient (HQ) assessments indicated that formaldehyde concentrations pose a potential lifetime carcinogenic risk to the local population.

The application of nitrogen fertilizers in agricultural fields can lead to the release of nitrogen-containing gases (NCGs), such as NOx, NH3 and N2O, which can significantly impact regional atmospheric environment and contribute to global climate change. However, there remain considerable research gaps in the accurate measurement of NCGs emissions from agricultural fields, hindering the development of effective emission reduction strategies. We improved an open-top dynamic chambers (OTDCs) system and evaluated the performance by comparing the measured and given fluxes of the NCGs. The results showed that the measured fluxes of NO, N2O and NH3 were 1 %, 2 % and 7 % lower than the given fluxes, respectively. For the determination of NH3 concentration, we employed a stripping coil-ion chromatograph (SC-IC) analytical technique, which demonstrated an absorption efficiency for atmospheric NH3 exceeding 96.1 % across sampling durations of 6 to 60 min. In the summer maize season, we utilized the OTDCs system to measure the exchange fluxes of NO, NH3, and N2O from the soil in the North China Plain. Substantial emissions of NO, NH3 and N2O were recorded following fertilization, with peaks of 107, 309, 1239 ng N/(m2·s), respectively. Notably, significant NCGs emissions were observed following sustained heavy rainfall one month after fertilization, particularly with NH3 peak being 4.5 times higher than that observed immediately after fertilization. Our results demonstrate that the OTDCs system accurately reflects the emission characteristics of soil NCGs and meets the requirements for long-term and continuous flux observation.

In recent years, ozone has become one of the key pollutants affecting the urban air quality. Direct catalytic decomposition of ozone emerges as an effective method for ozone removal. Field experiments were conducted to evaluate the effectiveness of exterior wall coatings with ozone decomposition catalysts for ozone removal in practical applications. ANSYS 2020R1 software was first used for simulation and analysis of ozone concentration and flow fields to investigate the decomposition boundary of these wall coatings. The results show that the exterior wall coatings with manganese-based catalysts can effectively reduce the ozone concentration near the wall coating. The ozone decomposition efficiency is negatively correlated with the distance from the coating and the decomposition boundary range is around 18 m. The decomposition boundary will increase with the increase of temperature, and decrease with the increase of the wind speed and the relative humidity. These results underscore the viability of using exterior wall coatings with catalysts for controlling ozone pollution in atmospheric environments. This approach presents a promising avenue for addressing ozone pollution through self-purifying materials on building external wall.

Peroxyacetyl nitrate (PAN) is an important photochemical pollutant in the troposphere, whereas long-term measurements are scarce in rural areas in North China Plain (NCP), resulting in unclear seasonal variations and sources of PAN in rural NCP. In this study, we conducted a 1-year observation of PAN during 2021-2022 at the rural NCP site. The average concentrations of PAN were 1.10, 0.75, 0.65, and 0.88 ppbv in spring, summer, autumn, and winter, respectively, with a 1-year average of 0.81 ± 0.60 ppbv. Calculations indicate that the loss of PAN through thermal decomposition in summer accounts for 43.2% of the total formed PAN, which is an important reason for the low concentration of PAN in summer. We speculate that since the correlation between PAN and O3 in winter is significantly lower than that in other seasons, the observed regional transport of PAN cannot be ignored in winter. Through budget analysis, regional transport accounted for 12.8% and 55.9% of the observed PAN on the spring and winter pollution days, respectively, which showed that regional transport played key roles during the photochemical pollution of the rural NCP in winter. The potential source contribution function revealed that the transported PAN mainly comes from southern Hebei in spring. In winter, the transported PAN was mainly from Langfang, Hengshui, and southern Beijing. Our findings may aid in understanding PAN variations in different seasons in rural areas and highlight the impact of regional transport on the PAN budget.

Gaseous nitrous acid (HONO) is a critical contributor to daytime hydroxyl radical in the troposphere. Livestock farming has been recognized as an overlooked HONO source, but the lack of detailed flux measurements from livestock and poultry wastes would cause uncertainties in modeling its environmental impacts. Here, based on field flux measurements and laboratory experiments, we observed substantial HONO emissions from the composting of swine feces and chicken manure in the warm season, which might be mainly attributed to nitrification process in livestock and poultry wastes. The HONO emission from chicken manure was found to be much higher than that from swine feces, and the higher NH3 emission but lower N2O and NO emissions from chicken manure were also observed. Considering that the interaction among these nitrogen species during nitrification process, the obviously lower HONO emission from swine feces was likely to be explained by the lack of the total ammonia nitrogen and H+ donors in swine feces. Temperature is also a key factor that influences the HONO emission from livestock wastes. In addition, the total HONO emission from swine feces in China was estimated to be approximately 107.7 Gg-N/yr according to the national swine amounts, which is comparable to the national soil HONO emissions, underscoring its non-negligible contribution to regional air quality. Therefore, effective emission control of HONO from livestock and poultry wastes should be carried out to further improve air quality in China.

As the predominant pollutant in North China during the summer months, ozone (O3) exhibits strong oxidizing capabilities. Long-term exposure of crops to ozone will cause a decrease in various physiological indicators, affect crop yields, and pose a serious threat to food security. The North China Plain, the primary region for summer maize production in China, is afflicted by ozone pollution. In order to explore the effects of increasing O3 concentration on the physiological characteristics and photosynthetic characteristics of summer maize, this study took summer-sown maize as the research object and carried out the ozone exposure experiment with open-top chamber (OTCs). The response of maize to O3 exposure was studied by measuring the damage, physiological indexes and photosynthetic indexes in the silking stage (late July to late August) and filling stage (late August to mid-September). The results indicated the following: (1) Prolonged exposure to high O3 concentrations exacerbated leaf chlorosis and damage. (2) The increase in O3 concentration caused lipid peroxidation. The content of malondialdehyde was significantly increased by 32.6%~122.56%. At the same time, chlorophyll was destroyed and decreased by 2.17% to 4.86%. Under ozone exposure, ascorbic acid content was significantly increased by 7.58%~35.69%. The antioxidant indexes of maize were more sensitive during the filling stage. (3) Under O3 exposure, photosynthetic rate, stomatal conductance and intercellular carbon dioxide concentration decreased significantly, indicating that the influence of O3 on maize was mainly due to stomatal limitation. Water use efficiency and transpiration rate decreased significantly. The water use efficiency decreased by 12.84%~35.62%, which led to the weakening of the carbon fixation ability of maize and affected the normal growth and development of maize.

Surface ozone pollution is a significant environmental problem. In addition to the control of ozone precursors, direct catalytic decomposition of ozone is an effective control method with broad prospects. At present, the evaluation of the ozone decomposition performance of catalysts is typically performed in the laboratory, and the lack of scientific evaluation means to apply them to complex ambient atmosphere limits the practical application of ozone removal catalysts. Here, we devised a new evaluation method for ozone catalytic decomposition materials in the ambient atmosphere that can comprehensively evaluate the influence of various factors in the

Deep learning models are widely used for PM2.5 prediction. However, neglecting temporal and spatial characteristics leads to low prediction accuracy. In this work, a new deep learning model (RCG - Attention model) was developed, which combines the residual neural network (ResNet) and the convolution gated recurrent network (ConvGRU) and is applied to extract the spatio - temporal features for predicting PM2.5 concentration over the subsequent 24 h. The ResNet extracts the spatial distribution features of pollutants, and the ConvGRU extracts temporal features. The spatial and temporal features are fused by the multi - head attention mechanism to obtain multi - dimensional features. These features are finally fed into a series of fully connected layers to predict the future results. Incorporating these chemical components enhances the scientific validity of the dataset and strengthens the inherent logical connections among variables. The Mean Absolute Error (MAE), Mean Absolute Percentage Error (MAPE), Root Mean Square Error (RMSE), and R - squared (R2) results indicate that the prediction performance of the RCG - Attention model surpasses that of other baseline models. The model demonstrates superior prediction performance across multiple monitoring stations, suggesting robust generalization capabilities and adaptability for various regions in one city. The SHAP results show that PM10, NO2, RH, NO3-, OC and NH4+ are significant influencing features. The RCG - Attention model provides a comprehensive solution for PM2.5 concentration prediction by integrating spatial and temporal feature extraction with chemical components.

Rate coefficients for the reactions of OH radicals with C-3-C-11 alkanes were determined using the multivariate relative-rate technique. A total of 25 relative-rate coefficients at room temperature and 24 Arrhenius expressions in the temperature range of 273-323 K were obtained. Notably, a new room temperature relative-rate coefficient for 3-methylheptane that had not been previously reported was determined, and the obtained kOH value (in units of 10(-12) cm(3) molec.(-1) s(-1)) was 7.71 +/- 0.35. Interestingly, whilst results for n-alkanes agreed well with available structure-activity relationship (SAR) calculations of Kwok and Atkinson (1995), Neeb (2000), Wilson et al. (2006), Jenkin et al. (2018), and McGillen et al. (2020), the three cycloalkanes (cyclopentane, methylcyclopentane, cyclohexane) and one branched alkane (2,2,4-trimethylpentane) were found to be less reactive than predicted by the SAR approach. Conversely, the SAR estimates for 2,3-dimethylbutane were approximately 25 % lower than the experimental values, with the exception of those estimated by the Wilson group, highlighting that there may be additional factors that govern the reactivity of highly branched alkanes that are not captured by current SAR techniques. Arrhenius expressions (in units of cm(3) molec.(-1) s(-1)) for the reactions of various branched alkanes with OH radicals were determined for the first time: 2-methylheptane, 1.37 +/- 0.48x10(-11)exp[-209 +/- 100/T, and 3-methylheptane, 3.54 +/- 0.45x10(-11)exp]-374 +/- 49/T. The reactivity relation of saturated alkanes with OH radicals and chlorine atoms was obtained: log(10)(k(Cl+alkanes)=0.569xlog(10)k((OH+alkanes)))-3.111 (R-2 = 0.86). In addition, the rate coefficients for the 24 previously studied OH + alkanes reactions were consistent with existing literature values, demonstrating the reliability and efficiency of this method for the simultaneous investigation of gas-phase reaction kinetics.

Atmospheric ammonia (NH3) plays an important role in secondary inorganic aerosol formation. Understanding the temporal variations, sources, and environmental influences of NH3 is conducive to better formulate PM2.5 pollution control strategies for policy-makers. Here, we performed a comprehensive field campaign with the measurements of NH3 and related parameters at a rural site of the North China Plain (NCP) in winter of 2017. The results showed that residential coal combustion contributed dominantly to NH3 during the entire observation period, resulting in the obviously high average concentration of NH3 (31.2 ± 24.6 ppbv). The sensitivity tests of pH-NHx during the three different pollution periods suggested that the rural site was always in the NHx-rich atmosphere where high levels of NHx increased the particle pH inefficiently. Nevertheless, the particle pH still elevated by 1.5-2.2 units at the excessive NHx levels during the three pollution periods. In addition, the HONO/NO2 ratios were found to correlate linearly with NH3 concentrations, implying the acceleration effect of NH3 on HONO production from NO2 heterogeneous reactions. After considering the NH3-enhanced uptake coefficient of NO2 in the nocturnal HONO budget, the unknown source of HONO could be fully explained. Therefore, more attentions should be given for effective emission control of NH3 to improve air quality throughout the NCP, especially in the rural areas.

The surface atmospheric O3 concentration in Kunming shows a significant upward trend, with high values mainly occurring in March–May. Volatile organic compounds (VOCs) are one of the most important precursors of O3. However, the sources of VOCs are complex and difficult to identify. In order to understand the pollution levels, the spatial distribution characteristics, and possible sources of VOCs, we conducted simultaneous offline sampling at representative sites in six different functional areas of Kunming using SUMMA canisters for one week. The VOC samples were analyzed via GC/MS. The VOC data were analyzed (using the feature ratio method, ozone formation potential (OFP), and Positive Matrix Factorization (PMF) model). Some important conclusions were drawn. Firstly, VOCs during the spring in Kunming were mainly derived from oxygenated VOCs, aromatic hydrocarbons, and halogenated hydrocarbons, with significant spatial differences. Secondly, we found that the potential for atmospheric ozone formation is higher in Kunming for aromatic hydrocarbons and oxygenated VOCs. Finally, the results of the Positive Matrix Factorization model (PMF) showed that Kunming’s ambient atmospheric VOCs mainly originate from anthropogenic source emissions. These conclusions can provide useful reference information for O3 pollution control in Kunming.

Field measurements of volatile organic compounds (VOCs) were conducted simultaneously at an urban site and one industrial park site in Beijing in summer. The VOCs concentrations were 94.3 ± 157.8 ppbv and 20.7 ± 8.9 ppbv for industrial and urban sites, respectively. Alkanes and aromatics were the major contributors to VOCs in industrial site, while oxygenated volatile organic compounds (OVOCs) contributed most in urban site. The most abundant VOC species were n-pentane and formaldehyde for industrial site and urban site, respectively. The calculated ozone formation potential (OFP) and OH loss rates (LOH) were 621.1 ± 1491.9 ppbv (industrial site), 102.9 ± 37.3 ppbv (urban site), 22.0 ± 39.0 s−1 (industrial site) and 5.3 ± 2.2 s−1 (urban site), respectively. Based on the positive matrix factorization (PMF) model, solvent utilization I (34.1 %), solvent utilization II (27.9 %), mixture combustion source (19.3 %), OVOCs related source (9.6 %) and biogenic source (9.1 %) were identified in the industrial site, while OVOCs related source (27.8 %), vehicle exhaust (22.1 %), solvent utilization (19.3 %), coal combustion (16.0 %) and biogenic source (14.8 %) were identified in the urban site. The results of O3-VOCs-NOx sensitivity indicated that O3 formation were respectively under the VOC-limited and NOx-limited conditions in Beijing urban and industrial regions. Additionally, aromatics accounted remarkable SOA formation ability both in the two sites, and SOA potentials of xylene, toluene and ethylbenzene as the indicator species for the solvent utilization in industrial site were remarkable higher than those obtained in urban regions. The hazard index values in the industrial and urban sites were 1.72 and 3.39, respectively, suggesting a high non-carcinogenic risks to the exposed population. Formaldehyde had the highest carcinogenic risks in the two sites, and the cumulative carcinogenic risks in the industrial site and urban site were 1.95 × 10−5 and 1.21 × 10−5, respectively.

Particulate nitrate (NO3-) has currently become the major component of fine particles in the North China Plain (NCP) during winter haze episodes. However, the contributions of formation pathways to ground NO3- in the NCP are not fully understood. Herein, the NO3- formation pathways were comprehensively investigated based on model simulations combined with two-month field measurements at a rural site in the winter NCP. The results indicated that the nocturnal chemistry of N2O5 hydrolysis aloft could contribute evidently to ground NO3- at the rural site during the pollution episodes with high aerosol water contents, achieving the contribution percentages of 25.2-30.4% of the total. In addition to the commonly proposed vertical mixing of breaking nocturnal boundary layer in the early morning, two additional transport pathways (frontal downdrafts and downslope mountain breezes) in the nighttime were found to make higher contributions to ground NO3-. Considering the dominant role (69.6-74.8%) of diurnal chemistry in NO3- formation, reduction of NOx emissions in the daytime may be an effective control measure for reducing regional NO3- in the NCP.

居民使用煤炭等固体燃料采暖或炊事时常排放出大量污染物,不仅会造成严重的空气污染,还严重影响居民身体健康和生命安全,受到国际社会的长期关注.本文基于居民燃煤污染物组成和煤的燃烧机理,探讨了污染物的产生及排放规律;结合居民燃煤炉灶类型,综述了居民煤炭主要燃烧技术的原理及优缺点;针对居民散煤的清洁燃烧,从居民用煤标准、清洁燃烧技术选择、清洁燃烧炉灶的科学评价几方面提出建议.

Continuous measurements of volatile organic compounds (VOCs) were conducted at an urban site in Tai'an, Shandong province of China from 15 May to 10 June 2019. The concentration of total VOCs (TVOCs) was 28.73 +/- 15.20 ppbv, and oxygenated VOCs (OVOCs) comprised the dominant proportion (46.4%) among five VOC groups. The most abundant VOC species was formaldehyde, followed by propane, ethane, acetaldehyde, acetone and ethylene. Six VOC sources were identified by positive matrix factorization (PMF) model, including coal combustion (26.2%), OVOCs-related source (20.2%), liquefied petroleum gas (LPG) usage (18.9%), vehicle emission (17.1%), biogenic source (11.1%) and solvent usage (6.5%). The results of conditional bivariate probability function (CBPF) showed that LPG usage, vehicle exhaust and solvent usage were mainly affected by local emissions, while other three sources were greatly affected by regional transmission. Based on the China Ambient Air Quality Standard, O-3 episode and non-O-3 episode days were identified, and the concentrations of TVOCs were 32.80 +/- 15.78 ppbv (O-3 episode days) and 24.01 +/- 14.47 ppbv (non-O-3 episode days), respectively. During different O-3 pollution episodes, OVOCs contributed the highest proportion to VOC concentration and ozone formation potential (OFP), while aromatics contributed the greatest potential for secondary organic aerosol potential (SOAP). Moreover, coal combustion and LPG usage were significantly associated with the increase in VOC pollution on O-3 episode days.

Volatile organic compounds (VOCs) tend to be consumed by atmospheric oxidants, resulting in substantial photochemical loss during transport. An observation-based model was used to evaluate the influence of photochemical loss of VOCs on the sensitivity regime and mechanisms of ozone formation. Our results showed that a VOC-limited regime based on observed VOC concentrations shifted to a transition regime with a photochemical initial concentration of VOCs (PIC-VOCs) in the morning. The net ozone formation rate was underestimated by 3 ppb h−1 (∼36 ppb d−1) based on the measured VOCs when compared with the PIC-VOCs. The relative contribution of the RO2 path to ozone production based on the PIC-VOCs accordingly increased by 13.4 %; in particular, the contribution of alkene-derived RO2 increased by approximately 10.2 %. In addition, the OH–HO2 radical cycle was obviously accelerated by highly reactive alkenes after accounting for photochemical loss of VOCs. The contribution of local photochemistry might be underestimated for both local and regional ozone pollution if consumed VOCs are not accounted for, and policymaking on ozone pollution prevention should focus on VOCs with a high reactivity.

Owing to the implementation of air pollution control actions, anthropogenic emissions in Beijing have changed in recent years. Understanding the impact of changes in anthropogenic emissions on O3 and PM2.5 trends is helpful for developing air quality management strategies. Herein, we investigated the variations of air pollutants in summer over Beijing using long-term data sets from 2014 to 2019, and explored the responses of O3 and PM2.5 trends to changes in anthropogenic emissions based on multiple linear regression (MLR) analysis and WRF-Chem model. The results indicated a significant decrease in PM2.5, but a near constant level of O3 during 2014-2019. The decrease rate of PM2.5, which was lower than that of SO2, might be due to the effect of NO2 on atmospheric PM2.5. Both the slightly increasing correlations between PM2.5 and NO2 and the WRF-Chem model simulations implied that atmospheric PM2.5 in Beijing is trending to be more sensitive to NOx than SO2. The emissions of NOx and VOCs from industry and transportation were found to make great contribution to O3 production in Beijing. Due to the titration of NOx in VOC-limited regime, the relatively low emission ratios of NOx and VOCs from industry and transportation in Beijing provided convincing evidence for the persistently high O3 concentrations during 2014-2019. However, the noticeable increase of the O3 trends in other areas (e.g., Hebei, Tianjin) could be explained by the significant decline in the emission ratios of NOx and VOCs from anthropogenic emissions especially industry during 2014-2019. Controlling the emission of NOx can substantially reduce PM2.5 pollution, but may aggravate O3 pollution, and thus effective VOC emission control strategies need to be considered for simultaneously controlling O3 and PM2.5 pollution in Beijing and other regions of China.

Tropospheric ozone (O-3) pollution is increasing in the Beijing-Tianjin-Hebei (BTH) region de-spite a significant decline in atmospheric fine aerosol particles (PM2.5) in recent years. How-ever, the intrinsic reason for the elevation of the regional O-3 is still unclear. In this study, we analyzed the spatio-temporal variations of tropospheric O-3 and relevant pollutants (PM2.5, NO2, and CO) in the BTH region based on monitoring data from the China Ministry of Ecology and Environment during the period of 2014-2019. The results showed that summertime O-3 concentrations were constant in Beijing (BJ, 0.06 pg/(m(3).year)) but increased significantly in Tianjin (TJ, 9.09 pg/(m(3).year)) and Hebei (HB, 6.06 pg/(m(3).year)). Distinct O-3 trends between Beijing and other cities in BTH could not be attributed to the significant decrease in PM2.5 (from-5.08 to-6.32 pg/(m(3).year)) and CO (from-0.053 to-0.090 mg/(m(3).year)) because their decreasing rates were approximately the same in all the cities. The relatively stable O-3 con-centrations during the investigating period in BJ may be attributed to a faster decreasing rate of NO2 (BJ:-2.55 pg/(m(3).year); TJ:-1.16 pg/(m(3).year); HB:-1.34 pg/(m(3).year)), indicating that the continued reduction of NOx will be an effective mitigation strategy for reducing regional O-3 pollution. Significant positive correlations were found between daily maximum 8 hr average (MDA8) O-3 concentrations and vehicle population and highway freight trans-portation in HB. Therefore, we speculate that the increase in rural NOx emissions due to the increase in vehicle emissions in the vast rural areas around HB greatly accelerates regional O-3 frmation, accounting for the significant increasing trends of O-3 in HB. (C) 2022 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Gas-phase hydrogen peroxide (H2O2) plays an important role in atmospheric chemistry as an indicator of the atmospheric oxidizing capacity. It is also a vital oxidant of sulfur dioxide (SO2) in the aqueous phase, resulting in the formation of acid precipitation and sulfate aerosol. However, sources of H2O2 are not fully understood especially in polluted areas affected by human activities. In this study, we reported some high H2O2 cases observed during one summer and two winter campaigns conducted at a polluted rural site in the North China Plain. Our results showed that agricultural fires led to high H2O2 concentrations up to 9 ppb, indicating biomass burning events contributed substantially to primary H2O2 emission. In addition, elevated H2O2 and O3 concentrations were measured after fertilization as a consequence of the enhanced atmospheric oxidizing capacity by soil HONO emission. Furthermore, H2O2 exhibited unexpectedly high concentration under high NOx conditions in winter, which are closely related to multiphase reactions in particles involving organic chromophores. Our findings suggest that these special factors (biomass burning, fertilization, and ambient particles), which are not well considered in current models, are significant contributors to H2O2 production, thereby affecting the regional atmospheric oxidizing capacity and the global sulfate aerosol formation.