Regional background ozone estimation for China through data fusion of observation and simulation.

Regional background ozone (O3_RBG) is an important component of surface ozone (O3). However, due to the uncertainties in commonly used Chemical Transport Models (CTMs) and statistical models, accurately assessing O3_RBG in China is challenging. In this study, we calculated the O3_RBG concentrations with the CTM - Brute Force Method (BFM) and constrained the results with site observations of O3 with the multiple linear regression (MLR) model. The annual average O3_RBG concentration in China region in 2020 is 35 ± 4 ppb, accounting for 81 ± 5 % of the maximum 8-h average O3 (MDA8 O3). We applied the random forest and Shapley additive explanations based on meteorological standardization techniques to separate the contributions of meteorology and natural emissions to O3_RBG. Natural emissions contribute more significantly to O3_RBG than meteorology in various Chineses regions (30-40 ppb), with higher contributions during the warm season. Meteorological factors show higher contributions in the spring and summer seasons (2-3 ppb) than the other seasons. Temperature and humidity are the primary contributors to O3_RBG in regions with severe O3 pollution in China, with their individual impacts ranging from 30 % to 62 % of the total impacts of all meteorological factors in different seasons. For policy implications, we tracked the contributions of O3_RBG and local photochemical reaction contributions (O3_LC) to total O3 concentration at different O3 levels. We found that O3_LC contribute over 45 % to MDA8 O3 on polluted days, supporting the current Chinese policy of reducing O3 peak concentrations by cutting down precursor emissions. However, as the contribution of O3_RBG is not considered in the policy, additional efforts are needed to achieve the control groal of O3 concentration. As the implementation of stringent O3 control measurements in China, the contribution of O3_RBG become increasingly significant, suggesting the need for attention to O3_RBG and regional joint prevention and control.

[Source Analysis of Ozone and Its Precursors in Zibo Based on 3-D Air Quality Model].

Based on the ISAM module in the WRF-CMAQ model, this study analyzed the source contribution(both regional and sectoral) of O3 and its precursors(NO2 and VOCs) in Zibo in June 2021. Days with a maximum daily 8-h average(MDA8) O3 higher(lower) than 160 µg·m-3 were defined as polluted(clean) days. Differences in the source contribution between clean days and polluted days were compared, and a typical pollution period was selected for further process analysis. The results showed that NO2 in Zibo mainly came from local emissions in summer, with a relative contribution of 45.1%. Vehicle emissions(33.8%) and natural sources(20.7%) were the primary NO2 sources. VOC contributions from natural sources, solvent usage, and the petrochemical industry were significant, with a total contribution of 78.5%. The MDA8 contribution from local sources was 21.4%, whereas the impact of regional transport(32%) and surrounding cities(26.8%) was also substantial. Among local emission sources, vehicle emissions, the power industry, and the building materials industry contributed 10.9%-18.8% to local MDA8. On O3 pollution days, the MDA8 contribution from local emissions and surrounding cities increased. However, the relative contributions from local sources were similar under different pollution conditions.

Modeling of secondary organic aerosols (SOA) based on two commonly used air quality models in China: Consistent S/IVOCs contribution but large differences in SOA aging.

Secondary organic aerosol (SOA) is an important component of atmospheric fine particulate matter (PM2.5), with contributions from anthropogenic and biogenic volatile organic compounds (AVOC and BVOC) and semi- (SVOC) and intermediate volatility organic compounds (IVOC). Policymakers need to know which SOA precursors are important but accurate simulation of SOA magnitude and contributions remain uncertain. Findings from existing SOA modeling studies have many inconsistencies due to differing emission inventory methodologies/assumptions, air quality model (AQM) algorithms, and other aspects of study methodologies. To address some of the inconsistencies, we investigated the role of different AQM SOA algorithms by applying two commonly used models, CAMx and CMAQ, with consistent emission inventories to simulate SOA concentrations and contributions for July and November 2018 in China. Both models have a volatility basis set (VBS) SOA algorithm but with different parameters and treatments of SOA photochemical aging. SOA generated from BVOC (i.e., BSOA) is found to be more important in southern China. In contrast, SOA generated from anthropogenic precursors is more prevalent in the North China Plain (NCP), Yangtze River Delta (YRD), Sichuan Basin and Central China. Both models indicate negligible SOA formation from SVOC emissions compared to other precursors. In July, when BVOC emissions are abundant, SOA is predominantly contributed by BSOA (except for NCP), followed by IVOC-SOA (i.e., SOA produced from IVOC) and ASOA (i.e., SOA produced from anthropogenic VOC). In contrast, in November, IVOC became the leading SOA contributor for all selected regions except PRD, illustrating the important contribution of IVOC emissions to SOA formation. While both models generally agree in terms of the spatial distributions and seasonal variations of different SOA components, CMAQ tends to predict higher BSOA, while CAMx generates higher ASOA concentrations. As a result, CMAQ results suggest that BSOA concentration is always higher than ASOA in November, while CAMx emphasizes the importance of ASOA. Utilizing a conceptual model, we found that different treatment of SOA aging between the two models is a major cause of differences in simulated ASOA concentrations. The step-wise SOA aging scheme implemented in the CAMx VBS (based on gas-phase reactions with OH radical and similar to other models) exhibits a strong enhancement effect on simulated ASOA concentrations, and this effect increases with the ambient organic aerosol (OA) concentrations. The CMAQ aerosol module implements a different SOA aging scheme that represents particle-phase oligomerization and has smaller impacts on total OA. Different structures and/or parameters of the SOA aging schemes are being used in current models, which could greatly affect model simulations of OA in ways that are difficult to anticipate. Our results indicate that future control policies should aim at reducing IVOC emissions as well as traditional VOC emissions. In addition, aging schemes are the major driver in CMAQ vs. CAMx treatments of ASOA and their resulting predicted mass. More sophisticated measurement data (e.g., with resolved OA components) and/or chamber experiments (e.g., investigating how aging influences SOA yields) are needed to better characterize SOA aging and constrain model parameterizations.

Underestimation of biomass burning contribution to PM2.5 due to its chemical degradation based on hourly measurements of organic tracers: A case study in the Yangtze River Delta (YRD) region, China.

Biomass burning (BB) has significant impacts on air quality and climate change, especially during harvest seasons. In previous studies, levoglucosan was frequently used for the calculation of BB contribution to PM2.5, however, the degradation of levoglucosan (Lev) could lead to large uncertainties. To quantify the influence of the degradation of Lev on the contribution of BB to PM2.5, PM2.5-bound biomass burning-derived markers were measured in Changzhou from November 2020 to March 2021 using the thermal desorption aerosol gas chromatography-mass spectrometry (TAG-GC/MS) system. Temporal variations of three anhydro-sugar BB tracers (e.g., levoglucosan, mannosan (Man), and galactosan (Gal)) were obtained. During the sampling period, the degradation level of air mass (x) was 0.13, indicating that ~87 % of levoglucosan had degraded before sampling in Changzhou. Without considering the degradation of levoglucosan in the atmosphere, the contribution of BB to OC were 7.8 %, 10.2 %, and 9.3 % in the clean period, BB period, and whole period, respectively, which were 2.4-2.6 times lower than those (20.8 %-25.9 %) considered levoglucosan degradation. This illustrated that the relative contribution of BB to OC could be underestimated (~14.9 %) without considering degradation of levoglucosan. Compared to the traditional method (i.e., only using K+ as BB tracer), organic tracers (Lev, Man, Gal) were put into the Positive Matrix Factorization (PMF) model in this study. With the addition of BB organic tracers and replaced K+ with K+BB (the water-soluble potassium produced by biomass burning), the overall contribution of BB to PM2.5 was enhanced by 3.2 % after accounting for levoglucosan degradation based on the PMF analysis. This study provides useful information to better understand the effect of biomass burning on the air quality in the Yangtze River Delta region.

Differences between VOCs and NOx transport contributions, their impacts on O3, and implications for O3 pollution mitigation based on CMAQ simulation over the Yangtze River Delta, China.

The relationship between O3 and its precursors during urban polluted episodes remains unclear. In this study, the simultaneous source apportionment of VOCs, NOx, and O3 over the Yangtze River Delta (YRD) region during the O3 polluted episode on July 24-30, 2018, was performed based on the Integrated Source Apportionment Method (ISAM) embedded in the Community Multiscale Air Quality Modeling System (CMAQ). The results of the ISAM were compared with those of the Brute Force Method (BFM) and Positive Matrix Factorization (PMF). Furthermore, the differences between the transport contributions of VOCs and NOx, and their impacts on O3 were analyzed. The results indicate that observations of VOCs species can be well captured by simulated VOCs, and the ISAM has a significant advantage in the source apportionment of VOCs, especially for sources emitting highly reactive species. In the clean and polluted periods, the local contribution percentages of VOCs in urban sites ranged from 60 % to 77 %, much higher than those of NOx (31 %-43 %) and O3 (16 %-33 %). NOx and O3 have strong transport abilities with high and close contribution percentages, which are highly correlated, mainly because oxygen atoms produced by the photolysis of NO2 in the aged air mass combined rapidly with O2 to form O3 during transport. The VOCs chemical loss caused by the oxidation of OH radicals during transport makes the ability of VOCs for long-distance transport much weaker than that of NOx. Furthermore, owing to the sufficient aging of VOCs, those contributed by long-distance transport have little effect on O3. To a certain extent, controlling one's NOx emissions can help other cities more, while controlling one's VOCs emissions can help itself more. Therefore, it is recommended to attach enough importance to joint prevention and control of NOx among cities and even long-distance areas to alleviate regional O3 pollution.

Experiment investigation on effects of elastic modulus on cavitation erosion of silicone rubber.

Research into cavitation phenomena in various fields shows that the elastic modulus of a boundary has a potential impact on cavitation erosion. To obtain the direct relationship between the elastic modulus of the boundary and cavitiation erosion, single-layer samples with different chemical composition and moduli, and double-layer samples with different elastic moduli and the same surface layer material, were prepared with silicone rubber. The results of cavitation experiments on single-layer samples, show that the coating chemical composition and mechanical properties together affect the cavitation morphology of the coating, and dominant factors vary with erosion stage. Through the cavitation test of double-layer samples, it was found that there is a positive correlation between the elastic modulus of the coating and the degree of cavitation. This study helps us to understand the relationship between coating elastic modulus and cavitation more directly, and provides theoretical and technical guidance for the application of anti-cavitation for elastic coating in engineering.

Angle-Only Cooperative Orbit Determination Considering Attitude Uncertainty.

In this paper, a novel concept for cooperative orbit determination (OD) using inter-spacecraft angle-only measurements is proposed. Different from the conventional cooperative OD that only estimates orbit states, the attitude of the observer spacecraft is considered by incorporating the attitude into the estimated vector. The observability of a two-spacecraft system is analyzed based on the observability matrix. Observability analysis reveals that inter-spacecraft angle-only measurements are inadequate to estimate both the attitude and the orbit states in two-body dynamics. The observability of the two-spacecraft system can be improved by considering high-order gravitational perturbation or executing an attitude maneuver on the observer spacecraft. This is the first time that we present the observability analysis and orbit estimation results for a two-spacecraft system considering attitude uncertainty for the observer. Finally, simulation results demonstrate the effectiveness of the proposed method. The results in this paper can be potentially useful for autonomous managements of a spacecraft constellation and formation.

Developed compositional source profile and estimated emissions of condensable particulate matter from coal-fired power plants: A case study of Yantai, China.

The emission and environmental impact of condensable particulate matter (CPM) from coal-fired power plants (CFPPs) are of increasing concern worldwide. Many studies on the characteristics of CPM emission have been conducted in China, but its source profile remains unclear, and its emission inventory remains high uncertainty. In this work, the latest measurements reported in the latest 33 studies for CPM inorganic and organic species emitted from CFPPs in China were summarized, and then a compositional source profile of CPM for CFPPs was developed for the first time in China, which involved 10 inorganic species and 71 organic species. In addition, the CPM emission inventory of CFPPs in Yantai of China was developed based on surveyed activity data, continuous emission monitoring system (CEMS), and the latest measurement data. The results show that: (1) Inorganic species accounted for 77.64 % of CPM emitted from CFPPs in Yantai, among which SO42- had the highest content, accounting for 23.74 % of CPM, followed by Cl-, accounting for 11.95 %; (2) Organic matter accounted for 22.36 % of CPM, among which alkanes accounted for the largest proportion of organic fraction (72.7 %); (3) Emission concentration method (EC) and CEMS-based emission ratio method (ERFPM,CEMS) were recommended to estimate CPM emissions for CFPPs; (4) The estimated CPM emission inventories of Yantai CFPPs in 2020 by the EC method and the ERFPM,CEMS method were 1231 tons and 929 tons, respectively, with uncertainties of -34 % ∼ 33 % and -27 % ∼ 57 %, respectively; (5) CPM emissions were mainly distributed in the northern coastal areas of Yantai. This developed CPM source profile and emission inventory can provide basic data for assessing the impacts of CPM on air quality and health. In addition, this study can provide an important methodology for developing CPM emission inventories and CPM emission source profiles for stationary combustion sources in other regions.

Assessing the contribution of open crop straw burning to ground-level ozone and associated health impacts in China and the effectiveness of straw burning bans.

In recent years, ozone pollution in China has been shown to increase in frequency and persistence despite the concentrations of fine particulate matter (PM2.5) decreasing steadily. Open crop straw burning (OCSB) activities are extensive in China and emit large amounts of trace gases during a short period that could lead to elevated ozone concentrations. This study addresses the impacts of OCSB emissions on ground-level ozone concentration and the associated health impact in China. Total VOCs and NOx emissions from OCSB in 2018 were 798.8 Gg and 80.6 Gg, respectively, with high emissions in Northeast China (31.7%) and North China (23.7%). Based on simulations conducted for 2018, OCSB emissions are estimated to contribute up to 0.95 µg/m3 increase in annual averaged maximum daily 8-hour (MDA8) ozone and up to 1.35 µg/m3 for the ozone season average. The significant impact of OCSB emissions on ozone is mainly characterized by localized and episodic (e.g., daily) changes in ozone concentration, up to 20 µg/m3 in North China and Yangtze River Delta region and even more in Northeast China during the burning season. With the implementation of straw burning bans, VOCs and NOx emissions from OCSB dropped substantially by 46.9%, particularly over YRD (76%) and North China (60%). Consequently, reduced OCSB emissions result in an overall decrease in annual averaged MDA8 ozone, and reductions in monthly MDA8 ozone could be over 10 µg/m3 in North China. The number of avoided premature death due to reduced OCSB emissions (considering both PM2.5 and ozone) is estimated to be 6120 (95% Confidence Interval: 5320-6800), with most health benefits gained over east and central China. Our results illustrate the effectiveness of straw burning bans in reducing ozone concentrations at annual and national scales and the substantial ozone impacts from OCSB events at localized and episodic scales.

Highly time-resolved measurements of elements in PM2.5 in Changzhou, China: Temporal variation, source identification and health risks.

The temporal variation, sources, and health risks of elemental composition in fine particles (PM2.5) were explored using online measurements of 19 elements with a time resolution of 1 h at an urban location in Changzhou, China, from December 10, 2020 to March 31, 2021. The mass concentration of PM2.5 was 50.1 ±â€¯32.6 µg m-3, with a range of 3-218 µg m-3. The total concentration of 19 elements (2568 ±â€¯1839 ng m-3) accounted for 5.1 % of PM2.5 mass concentration. S, Cl, Si, and Fe were the dominant elementary species, accounting for 90 % of total element mass concentrations during the whole campaign. Positive matrix factorization (PMF) model was applied to identify the major emission sources of elements in PM2.5. Seven factors, named secondary sulfate mixed with coal combustion, Cl-rich, traffic, iron and steel industry, soil dust, fireworks, and shipping, were identified. The major sources for elements were iron and steel industry, followed by soil dust and secondary sulfate mixed with coal combustion, explaining 32.0 %, 23.5 % and 16.7 % of the total source contribution, respectively. The total hazard index (HI) of elements was 3.01 for children and 1.18 for adults, much greater than the admissible level (HI = 1). The total carcinogenic risk (CR) in Changzhou was estimated to be 5.87 × 10-5, which was above the acceptable CR level (1 × 10-6). Among the calculated metal elements, Cr, Co and As have higher carcinogenic risk, and Co was found to trigger the highest noncarcinogenic risk to Children. Our results indicate that industrial emission is the dominant CR contributor, emphasizing the necessity for stringent regulation of industry sources. Overall, our study provides useful information for policymakers to reduce emissions and health risks from elements in the Yangtze River Delta region.

[Characteristics of Soil NO Emissions in the Yangtze River Delta Region for Year 2018].

Soil NO emissions represent an important source of atmospheric nitric oxide (NO) and play an important role in atmospheric chemistry. Based on the latest BDSNP algorithm, this study estimated the soil NO emissions over the Yangtze River Delta region for the year 2018 and further analyzed the associated temporal and spatial variations and uncertainties. The results showed that the annual soil NO emissions in 2018 over the YRD region was 213.6 kt, accounting for 7.3% of the total anthropogenic NOx emissions. Areas with high emissions were mainly concentrated in northern Anhui Province and most parts of Jiangsu Province. In terms of monthly variations, soil NO emissions peaked in June, accounting for 19.9% of the annual emissions and 19.7% of anthropogenic NOx emissions in June. In terms of daily variations, soil NO emissions peaked around 16:00 and accounted for 5.5% of daily emissions. Soil NO emissions came from three components:soil background, nitrogen fertilizer application, and nitrogen deposition. Nitrogen fertilizer application was the main source of soil NO emissions, accounting for up to 77.8%. With the in-depth reduction in NOx emissions from motor vehicles and industries, the importance of soil NO emissions will become increasingly prominent.

Visibility, aerosol optical depth, and low-visibility events in Bangkok during the dry season and associated local weather and synoptic patterns.

Visibility and aerosol optical depth (AOD) characterization, and their relationship with PM10 and local and synoptic meteorology, were studied for January-March in 2014 and 2015 over Bangkok. Visibility degradation intensifies in the dry season as compared to the wet season due to increase in PM10 and unfavorable meteorological conditions. The average visibility is lower in January and February as compared to the other months. Relatively higher AOD in March despite lower PM10 is attributed to the synergetic effect of moderate relative humidity, secondary aerosols, elevated aerosol layer due to summertime convection, and biomass burning. Larger variability in visibility and PM10 in winter months is due to more synoptic weather fluctuations while AOD shows similar variability for all months attributed partly to fires. Higher PM10 and moderate-to-high relative humidity cause lower visibility in the morning while it improves in afternoon as PM10 and relative humidity decrease. AOD is higher in the afternoon as compared to that in the morning and evening as it is less sensitive to diurnal change in aerosols and meteorology at the surface level. Visibility and AOD relationships with PM10 are dependent on relative humidity. Weaker winds lead to lower visibility, higher PM10, and higher AOD irrespective of wind direction. Stronger winds improve visibility and decrease PM10 for all directions while AOD is higher for all directions except eastern and northeastern. The back-trajectory results show that the transport of pollutant and moist air is coupled with the synoptic weather and influence visibility and AOD. Two low-visibility events were investigated. The first event is potentially caused by the combined effect of local emissions and their accumulation due to stagnant weather conditions, secondary aerosols, and forest fires in the nearby regions. The second event can be attributed to the local emission and fires in the nearby area with hygroscopic growth of aerosols due to moist air from the Gulf of Thailand. Based on these findings, some policy implications have also been given.

Modeling the impacts of land use/land cover change on meteorology and air quality during 2000-2018 in the Yangtze River Delta region, China.

The land use/land cover (LULC) change in the fast-developing city clusters of China exhibits impacts on both the meteorology and air quality. However, this effect, especially in the Yangtze River Delta (YRD), has not been well quantified. In this study, the LULC data are extracted from Landsat satellite imageries for year 2000 and 2018 for the YRD region. The Weather Research and Forecasting with Chemistry (WRF/Chem) model is applied to investigate the impact of historical LULC change on regional meteorology and air pollution over the YRD region during the past two decades. Two simulation scenarios are performed with two sets of LULC data to represent the pre-urbanization (LULC of year 2000) and the most recent urban pattern (LULC of year 2018). Results indicate that rapid urbanization leads to an increase of monthly mean 2-m temperature by 0.4-2.1 °C but decrease of the 10-m wind speed by 0.5-1.3 m/s in urban areas; the maximum increase of daytime planetary boundary layer height (PBLH) in July and November is 289 and 132 m, respectively. Affected by favorable changes in the meteorological conditions due to LULC change, the PM2.5 concentrations in most urban areas show a decreasing trend, especially during the nighttime in summer. On the contrary, surface ozone (O3) concentration in urban areas has increased by 7.2-9.8 ppb in summer and 1.9-2.1 ppb in winter. Changes in O3 concentration are inversely proportional to changes in NOx and the spatial distribution of PM2.5. Areas with higher O3 concentration are consistent with areas of higher temperature and lower wind speed. Our findings reveal that LULC changes during the past years bring observable changes in air pollutant concentrations, which should not be neglected in the YRD region regarding air quality trends as well as policy evaluations under the warming threat.

[Role of Land Use Changes on Ammonia Emissions from Agricultural Ecosystems in the Yangtze River Delta Region from 2000 to 2018].

Based on Landsat satellite remote sensing images, this study interprets land use changes in the Yangtze River Delta (YRD) region from 2000 to 2018. Combined with changes in nitrogen fertilizer application, the changes in ammonia emissions from farmland ecosystem due changes in land use and nitrogen fertilizer application were further investigated. The results show that along with the rapid urbanization process, the area of cultivated land in the YRD region has gradually decreased from 276269 km2 (49% of total land area) in 2000 to 244001 km2 (44%) in 2018. The effects of changes in land use and nitrogen fertilizer application on ammonia emissions from farmland ecosystems mainly include emissions from soil background and nitrogen fertilizer application. From 2000 to 2018, ammonia emissions due to the application of nitrogen fertilizer decreased from 690 kt·a-1 to 541 kt·a-1 (relative decrease by 22%), while the ammonia emissions from the soil background reduced from 32 kt·a-1 to 29 kt·a-1 (decrease by 9%). During the past 20 years, urbanization in the YRD region has accelerated, and the area of cultivated land and the total amount of nitrogen fertilizer application have significantly reduced, thus resulting in reductions in ammonia emissions from the farmland ecosystem.

Hourly measurement of PM2.5-bound nonpolar organic compounds in Shanghai: Characteristics, sources and health risk assessment.

Fine particulate matter (PM2.5)-bound nonpolar organic compounds (NPOCs), including polycyclic aromatic hydrocarbons (PAHs) and alkanes, are commonly used as typical molecular markers for detailed source identification. Online thermal desorption aerosol gas chromatography-mass spectrometry (TAG) system can obtain ambient data with hourly resolution, which is of great importance for investigating the diurnal characteristics and refined source identification of NPOCs. From June to October 2020, hourly ambient aerosol samples were collected and analyzed to investigate the characteristics and sources of 14 PAHs and 15 alkanes (C21-C35) in PM2.5 using TAG at a suburban site of Baoshan district in Shanghai, China. The average concentration of summed PAHs and alkanes during the sampling period was 1.27 ± 1.4 ng/m3 and 8.87 ± 3.46 ng/m3, respectively, in which Benzo[b]fluoranthene (BbF), Benzo[ghi]perylene (BghiP) and Indeno[1,2,3-cd]pyrene (IcdP) are the dominant PAHs species, with n-Heptacosane (C27), n-Nonacosane (C29) and n-Hentriacontane (C31) being the most abundant n-alkane species. Carbon preference index (CPI) and carbon maximum (Cmax) number indicated that the sources of alkanes shifted from biogenic-oriented (such as plant wax) in the summer to anthropogenic-dominated (such as fossil fuels) in the autumn. Results from trajectory cluster analysis and potential source contribution function (PSCF) modeling showed that alkanes were mainly from the middle and lower reaches of the Yangtze River Plain including Anhui, Jiangxi, and Zhejiang provinces, while PAHs were mainly from northeastern China. Positive Matrix Factorization (PMF) model results indicated that gasoline (41.48%) and diesel (21.82%) were the two major sources of PM2.5-bound PAHs in summer and fall of 2020 in Shanghai, followed by coal consumption or catering (19.96%) and biomass burning (16.74%). Diurnal variation of PAHs sources resolved by PMF showed characteristic features consistent with the corresponding anthropogenic activities. For example, gasoline vehicle exhaust showed higher concentrations during traffic rush hours; while coal consumption or catering presented higher concentrations during lunch times from 10:00 to 12:00. In addition, the TAG data coupling with PMF also can be capable for source appointment of short-duration episodes. Health risk assessment showed that adult women were at greater lifetime cancer risk (ILCR) than people in other age groups, and people may subject to higher health risks at morning and night time. This work demonstrates that hourly NPOCs measured by TAG are uniquely specific on refined source identification and investigation into the characteristics of diurnal variations.

Assessment of the effects of straw burning bans in China: Emissions, air quality, and health impacts.

Open biomass burning (OBB) plays an important role in air pollution and climate change by releasing short-term but intensive amounts of particulate matter and gaseous air pollutants. During past years, policies with respect to prohibition on open straw burning have been issued in China in order to mitigate the air pollution problems and the effectiveness of these straw burning bans in different regions remains to be evaluated. In this study, open crop straw burning (OCSB) emissions during 2010-2018 were analyzed based on a commonly used emission inventory with high spatial and temporal resolution. High emissions concentrated over Northeast China (31.8% of national total PM2.5 emissions in 2018), East China (24.0%), and North China (16.6%). Simulations based on an integrated meteorology-air quality modeling system and an exposure-response function show that OCSB emissions could increase monthly PM2.5 concentration by as much as 10 µg/m3 during burning seasons in Northeast China and were associated with 4741 premature deaths in 2018. Spatial heterogeneities were observed with respect to the trends of OCSB emissions during 2010-2018. In East China, North China, and Central China, OCSB emissions showed a general declining trend since 2013 while an opposing increasing trend was observed in Northeast China with peak emissions in 2017. Comparing 2013 (before intensive implementation of straw burning bans) and 2018 (after), national total PM2.5 emissions from OCSB activities decreased by 46.9%, ranging from -14.1% to +70% depending on the specific regions. Northeast China is the only region that showed higher OCSB emissions in 2018 compared to 2013, probably associated with the relatively delayed implementation of the straw burning bans. Avoided number of premature deaths due to reduced OCSB emissions was estimated to be 4256 on a national scale, with most health benefits gained in East and Central China. Results from this study demonstrate the importance of OCSB contribution to PM2.5 concentrations and spatial heterogeneities exist in terms of the effectiveness of the straw burning bans in reducing OCSB emissions and gained health benefits.

Anthropogenic emissions of atomic chlorine precursors in the Yangtze River Delta region, China.

Chlorine radical plays an important role in the formation of ozone and secondary aerosols in the troposphere. It is hence important to develop comprehensive emissions inventory of chlorine precursors in order to enhance our understanding of the role of chlorine chemistry in ozone and secondary pollution issues. Based on a bottom-up methodology, this study presents a comprehensive emission inventory for major atomic chlorine precursors in the Yangtze River Delta (YRD) region of China for the year 2017. Four primary chlorine precursors are considered in this study: hydrogen chloride (HCl), fine particulate chloride (Cl-) (Cl- in PM2.5), chlorine gas (Cl2), and hypochlorous acid (HClO) with emissions estimated for twelve source categories. The total emissions of these four species in the YRD region are estimated to be 20,424 t, 15,719 t, 1556 and 9331 t, respectively. The emissions of HCl are substantial, with major emissions from biomass burning and coal combustion, together accounting for 68% of the total HCl emissions. Fine particulate Cl- is mainly emitted from industrial processing, biomass burning and waste incineration. The emissions of Cl2 and HClO are mainly associated with usage of chlorine-containing disinfectants, for example, water treatment, wastewater treatment, and swimming pools. Emissions of each chlorine precursor are spatially allocated based on the characteristics of individual source category. This study provides important basic dataset for further studies with respect to the effects of chlorine chemistry on the formation of air pollution complex in the YRD region.

[Emission Inventory of Intermediate Volatility Organic Compounds(IVOCs) from Biomass Burning in the Yangtze River Delta During 2010-2018].

Intermediate volatility organic compounds (IVOCs) are important precursors of secondary organic aerosols (SOA) but are currently not included in the conventional emissions inventories. Biomass burning represents an important source of IVOCs that could contribute to SOA formation. This study estimated the IVOC emissions from biomass burning in the Yangtze River Delta (YRD) region from 2010 to 2018 based on the fire inventory from NCAR (FINN) and the IVOCs/primary organic aerosol (POA) ratio reported in literature. During this period, the total number of fire events over the YRD region presented a declining trend, with an average of 104 fire events detected per year. During 2016-2018, the average number of fire events was approximately 6000 per year, which was 60% less than that prior to 2016. In terms of the monthly variation, the period from May to August was the period with the most fires observed, which was followed by a small peak in October. The results calculated based on the IVOCs/POA ratio method showed that the IVOC emissions from biomass burning exhibited large differences with different combinations of POA/OC and IVOCs/POA ratios, ranging from a maximum of 305.7×104 t to as small as 10.5×104 t. Monte Carlo simulation revealed that the uncertainties associated with the IVOCs/POA ratio method range from -99% to 68%.

Recent Advances on the Model, Measurement Technique, and Application of Single Cell Mechanics.

Since the cell was discovered by humans, it has been an important research subject for researchers. The mechanical response of cells to external stimuli and the biomechanical response inside cells are of great significance for maintaining the life activities of cells. These biomechanical behaviors have wide applications in the fields of disease research and micromanipulation. In order to study the mechanical behavior of single cells, various cell mechanics models have been proposed. In addition, the measurement technologies of single cells have been greatly developed. These models, combined with experimental techniques, can effectively explain the biomechanical behavior and reaction mechanism of cells. In this review, we first introduce the basic concept and biomechanical background of cells, then summarize the research progress of internal force models and experimental techniques in the field of cell mechanics and discuss the latest mechanical models and experimental methods. We summarize the application directions of cell mechanics and put forward the future perspectives of a cell mechanics model.

Derivatization of Levoglucosan for Compound-Specific δ 13C Analysis by Gas Chromatography/Combustion/Isotope Ratio Mass Spectrometry.

Levoglucosan is a thermal decomposition product of cellulose in particulate matter. δ 13C value of levoglucosan could be used in studying the combustion mechanisms and chemical pathways. In order to introduce a minimum number of carbon atoms, based on the stereostructure of levoglucosan, a two-step derivatization method with methylboronic acid and MSTFA was developed and carefully optimized. The recommended reaction temperature is 70°C; the reaction time is 60 min for MBA and 120 min for MSTFA derivatization; and the molar ratio of levoglucosan : MBA : MSTFA is 1 : 1: 100 and 1 : 1: 120 and the reagent volume ratio of MSTFA : pyridine is between 1 : 3 and 1 : 4. The developed method achieved excellent reproducibility and high accuracy. The differences in the carbon isotopic compositions of the target boronate trimethysilylated derivative between the measured and calculated ranged from 0.09 to 0.36‰. The standard deviation of measured δ 13C value of levoglucosan was between 0.22 and 0.48‰. The method was applied to particle samples collected from the combustion of cellulose at four different temperatures. δ 13C values of levoglucosan in particle samples generated from a self-made combustion setup suggesting that combustion temperature play a little role on isotope fractionation of levoglucosan, although 13C enriched in levoglucosan during the combustion process.