Real-World Emission Characteristics of Full-Volatility Organics Originating from Nonroad Agricultural Machinery during Agricultural Activities.

Nonroad agricultural machinery (NRAM) emissions constitute a significant source of air pollution in China. Full-volatility organics originating from 19 machines under 6 agricultural activities were measured synchronously. The diesel-based emission factors (EFs) for full-volatility organics were 4.71 ± 2.78 g/kg fuel (average ± standard deviation), including 91.58 ± 8.42% volatile organic compounds (VOCs), 7.94 ± 8.16% intermediate-volatility organic compounds (IVOCs), 0.28 ± 0.20% semivolatile organic compounds (SVOCs), and 0.20 ± 0.16% low-volatility organic compounds (LVOCs). Full-volatility organic EFs were significantly reduced by stricter emission standards and were the highest under pesticide spraying activity. Our results also demonstrated that combustion efficiency was a potential factor influencing full-volatility organic emissions. Gas-particle partitioning in full-volatility organics could be affected by multiple factors. Furthermore, the estimated secondary organic aerosol formation potential based on measured full-volatility organics was 143.79 ± 216.80 mg/kg fuel and could be primarily attributed to higher-volatility-interval IVOCs (bin12-bin16 contributed 52.81 ± 11.58%). Finally, the estimated emissions of full-volatility organics from NRAM in China (2021) were 94.23 Gg. This study provides first-hand data on full-volatility organic EFs originating from NRAM to facilitate the improvement of emission inventories and atmospheric chemistry models.

Reduced soil multifunctionality and microbial network complexity in degraded and revegetated alpine meadows.

Understanding how microbial processes develop and change in alpine meadow soils is key to global initiatives toward environmental sustainability and local land management. Yet, how microbial interactions mediate soil multifunctionality in disturbed and managed alpine meadows remains understudied. Here, we investigated multiple community metrics, particularly microbial network properties and assembly processes, of soil bacterial and fungal communities and their links to certain soil functions along a degradation-restoration sequence of alpine meadows in the Qinghai-Tibetan Plateau. Meadow degradation caused significant declines in soil hydraulic conductivity (e.g., higher bulk density, reduced soil porosity and water content) and nitrogen availability, leading to lowered soil multifunctionality. Meadow degradation only caused weak changes in microbial abundance, alpha diversity, and community composition, but remarkably reduced bacterial network complexity, to a less extent for fungal network properties. Short-term artificial restoration with productive grass monocultures did not restore soil multifunctionality, in turn even destabilized bacterial network and favored pathogenic over mutualistic fungi. Soil fungi community are more stable than bacteria in disturbed alpine meadows, and they evolved with distinct assembly strategies (stochastic-dominant versus deterministic-driven processes, respectively). Further, microbial network complexity, positively and better predicts soil multifunctionality than alpha diversity. Our work shows how microbial interaction complexity may enhance soil multifunctionality in degraded alpine meadow ecosystems, noting that meadow restoration with low plant species diversity may failed in restoring multiple ecosystem functions. These findings would help predict the outcomes of global environmental changes and inform management strategies in regional grassland conservation and restoration.

Vehicle emissions of primary air pollutants from 2009 to 2019 and projection for the 14th Five-Year Plan period in Beijing, China.

Over the past decade, the emission standards and fuel standards in Beijing have been upgraded twice, and the vehicle structure has been improved by accelerating the elimination of 2.95 million old vehicles. Through the formulation and implementation of these policies, the emissions of carbon monoxide (CO), volatile organic compounds (VOCs), nitrogen oxides (NOx), and fine particulate matter (PM2.5) in 2019 were 147.9, 25.3, 43.4, and 0.91 kton in Beijing, respectively. The emission factor method was adopted to better understand the emissions characteristics of primary air pollutants from combustion engine vehicles and to improve pollution control. In combination with the air quality improvement goals and the status of social and economic development during the 14th Five-Year Plan period in Beijing, different vehicle pollution control scenarios were established, and emissions reductions were projected. The results show that the emissions of four air pollutants (CO, VOCs, NOx, and PM2.5) from vehicles in Beijing decreased by an average of 68% in 2019, compared to their levels in 2009. The contribution of NOx emissions from diesel vehicles increased from 35% in 2009 to 56% in 2019, which indicated that clean and energy-saving diesel vehicle fleets should be further improved. Electric vehicle adoption could be an important measure to reduce pollutant emissions. With the further upgrading of vehicle structure and the adoption of electric vehicles, it is expected that the total emissions of the four vehicle pollutants can be reduced by 20%-41% by the end of the 14th Five-Year Plan period.

Real-world emission characteristics of carbonyl compounds from agricultural machines based on a portable emission measurement system.

Emissions of carbonyl compounds from agricultural machines cannot be ignored. Carbonyl compounds can cause the formation of ozone (O3) and secondary organic aerosols, which can cause photochemical smog to form. In this study, 20 agricultural machines were tested using portable emission measurement system (PEMS) under real-world tillage processes. The exhaust gases were sampled using 2,4-dinitrophenylhydrazine cartridges, and 15 carbonyl compounds were analyzed by high-performance liquid chromatography. Carbonyl compound emission factors for agricultural machines were 51.14-3315.62 mg/(kg-fuel), and were 2.58 ± 2.05, 0.86 ± 1.07 and 0.29 ± 0.20 g/(kg-fuel) for China 0, China II and China III emission standards, respectively. Carbonyl compound emission factor for sowing seeds of China 0 agricultural machines was 3.32 ± 1.73 g/(kg-fuel). Formaldehyde, acetaldehyde and acrolein were the dominant carbonyl compounds emitted. Differences in emission standards and tillage processes impact ozone formation potential (OFP). The mean OFP was 20.15 ± 16.15 g O3/(kg-fuel) for the China 0 emission standard. The OFP values decreased by 66.9% from China 0 to China II, and 67.4% from China II to China III. The mean OFP for sowing seeds of China 0 agricultural machines was 25.92 ± 13.84 g O3/(kg-fuel). Between 1.75 and 24.22 times more ozone was found to be formed during sowing seeds than during other processes for China 0 and China II agricultural machines. Total carbonyl compound emissions from agricultural machines in China was 19.23 Gg in 2019. The results improve our understanding of carbonyl compound emissions from agricultural machines in China.

Chemical characterization of volatile organic compounds (VOCs) emitted from multiple cooking cuisines and purification efficiency assessments.

Cooking process can produce abundant volatile organic compounds (VOCs), which are harmful to environment and human health. Therefore, we conducted a comprehensive analysis in which VOCs emissions from multiple cuisines have been sampled based on the simulation and acquisition platform, involving concentration characteristics, ozone formation potential (OFP) and purification efficiency assessments. VOCs emissions varied from 1828.5 to 14,355.1 µg/m3, with the maximum and minimum values from Barbecue and Family cuisine, respectively. Alkanes and alcohol had higher contributions to VOCs from Sichuan and Hunan cuisine (64.1%), Family cuisine (66.3%), Shandong cuisine (69.1%) and Cantonese cuisine (69.8%), with the dominant VOCs species of ethanol, isobutane and n-butane. In comparison, alcohols (79.5%) were abundant for Huaiyang cuisine, while alkanes (19.7%), alkenes (35.9%) and haloalkanes (22.9%) accounted for higher proportions from Barbecue. Specially, carbon tetrachloride, n-hexylene and 1-butene were the most abundant VOCs species for Barbecue, ranging from 8.8% to 14.6%. The highest OFP occurred in Barbecue. The sensitive species of OFP for Huaiyang cuisine were alcohols, while other cuisines were alkenes. Purification efficiency assessments shed light on the removal differences of individual and synergistic control technologies. VOCs emissions exhibited a strong dependence on the photocatalytic oxidation, with the removal efficiencies of 29.0%-54.4%. However, the high voltage electrostatic, wet purification and mechanical separation techniques played a mediocre or even counterproductive role in the VOCs reduction, meanwhile collaborative control technologies could not significantly improve the removal efficiency. Our results identified more effective control technologies, which were conductive to alleviating air pollution from cooking emissions.

Ten-year emission characteristics of atmospheric pollutants from incineration of sacrificial offerings in China.

The incineration of sacrificial offerings is a significant widely practiced custom that is also a kind of neglected air pollution source in China. Our results showed that the emission factors of particulate matter, SO2, CO, NOx, and VOCs emitted from the incineration of sacrificial offerings with purification systems were reduced by 95%, 19%, 9%, 82%, and 42%, respectively, compared with those without a purification system, revealing a significant effect of the flue gas purification system on reducing particulate matter and gaseous pollutants. The emission level of air pollutants from the incineration of sacrificial offerings remained stable before 2013 and then showed a remarkable decrease after the implementation of China´s Air Pollution Prevention Action Plan in 2013. The emissions of TSP (total suspended particulate), PM10, PM2.5, and NOx in 2009 were 8222, 6106, 5656 and 15,878 ton, respectively, obviously higher than 3434, 2551, 2305 and 8579 ton in 2019. Such trend was affected by both the quantity of incineration and the installation rate of purification systems after the Emission Standard of Air Pollutants for Crematory (GB 13801-2015) issued in China. Distinct spatial distribution of atmospheric pollutants from incineration of sacrificial offerings was found with higher in the east and south of China than the west and north of China, which is proportional to the regional economy and population. The maximum ground-level concentration typically occurred at 0.12-0.2 km from the pollution source, posing potential health risks to people entering and exiting funeral and burial sites and nearby residents.

Fine particulate matter (PM2.5/PM1.0) in Beijing, China: Variations and chemical compositions as well as sources.

Particulate matter (i.e., PM1.0 and PM2.5), considered as the key atmospheric pollutants, exerts negative effects on visibility, global climate, and human health by associated chemical compositions. However, our understanding of PM and its chemical compositions in Beijing under the current atmospheric environment is still not complete after witnessing marked alleviation during 2013-2017. Continuous measurements can be crucial for further air quality improvement by better characterizing PM pollution and chemical compositions in Beijing. Here, we conducted simultaneous measurements on PM in Beijing during 2018-2019. Results indicate that annual mean PM1.0 and PM2.5 concentrations were 35.49 ± 18.61 µg/m3 and 66.58 ± 60.17 µg/m3, showing a positive response to emission controls. The contribution of sulfate, nitrate, and ammonium (SNA) played an enhanced role with elevated PM loading and acted as the main contributors to pollution episodes. Discrepancies observed among chemical species between PM1.0 and PM2.5 in spring suggest that sand particles trend to accumulate in the range of 1-2.5 µm. Pollution episodes occurred accompanied with southerly clusters and high formation of SNA by heterogeneous reactions in summer and winter, respectively. Results from positive matrix factorization (PMF) combined with potential source contribution function (PSCF) models showed that potential areas were seasonal dependent, secondary and vehicular sources became much more important compared with previous studies in Beijing. Our study presented a continuous investigation on PM and sources origins in Beijing, which provides a better understanding for further emission control as well as a reference for other cities in developing countries.

Significant but Spatiotemporal-Heterogeneous Health Risks Caused by Airborne Exposure to Multiple Toxic Trace Elements in China.

Airborne trace elements (TEs) pose a notable threat to human health due to their toxicity and carcinogenicity, whereas their exposures and associated health risks in China remain unclear. Here, we present the first nationwide assessment of spatiotemporal exposure to 11 TEs in China by coupling a bottom-up emission inventory with a modified CMAQ model capable of TE simulation. Associated health risks of 11 TEs are then evaluated using a set of risk assessment models. Our results show that the CMAQ model could reasonably reproduce the spatiotemporal variations of 11 TEs in China compared to observations. We find significant but spatiotemporal-heterogeneous cancer risks associated with high-level exposure of TEs in China. Gridded cell concentrations of hexavalent chromium, arsenic, and nickel in eastern and central China usually exceed China's air quality standard limits, resulting in significant cancer risks that affected over 85% of the entire population in China in 2015. National annual mean population-weighted concentrations of 11 TEs decrease by 9.8-35.6% from 2012 to 2015, largely attributed to emission reduction from coal combustion. Our study provides critical insights for policymakers to implement stricter measures to alleviate health burdens and benefit relevant epidemiological research on airborne TEs.

Variation characteristics of fine particulate matter and its components in diesel vehicle emission plumes.

A rapid reaction occurs near the exhaust nozzle when vehicle emissions contact the air. Twenty diesel vehicles were studied using a new multipoint sampling system that is suitable for studying the exhaust plume near the exhaust nozzle. The variation characteristics of fine particle matter (PM2.5) and its components in diesel vehicle exhaust plumes were analyzed. The PM2.5 emissions gradually increased with increasing distance from the nozzle in the plume. Elemental carbon emissions remained basically unchanged, organic carbon and total carbon (TC) increased with increasing distance. The concentrations of SO42-, NO3- and NH4+ (SNA) directly emitted by the vehicles were very low but increased rapidly in the exhaust plume. The selective catalytic reduction (SCR) reduced 42.7% TC, 40% NO3- emissions, but increased 104% SO42- and 36% NH4+ emissions, respectively. In summary, the SCR reduced 29% primary PM2.5 emissions for the tested diesel vehicles. The NH4NO3 particle formation maybe more important in the plume, and there maybe other forms of formation of NH4+ (eg. NH4Cl). The generation of secondary organic carbon (SOC) plays a leading role in the generation of secondary PM2.5. The SCR enhanced the formation of SOC and SNA in the plume, but comprehensive analysis shows that the SCR more enhanced the SNA formation in the plume, which is mainly new particles formation process. The inconsistency between secondary organic aerosol (SOA) and primary organic aerosol definitions is one of the important reasons for the difference between SOA simulation and observation.

Non-Negligible Stack Emissions of Noncriteria Air Pollutants from Coal-Fired Power Plants in China: Condensable Particulate Matter and Sulfur Trioxide.

In this study, we investigated the emission characteristics of condensable particulate matter (CPM) and sulfur trioxide (SO3) simultaneously through ammonia-based/limestone-based wet flue gas desulfurization (WFGD) from four typical coal-fired power plants (CFPPs) by conducting field measurements. Stack emissions of filterable particulate matter (FPM) all meet the Chinese ultralow emission (ULE) standards, whereas CPM concentrations are prominent (even exceed 10 mg/Nm3 from two CFPPs). We find that NH4+ and Cl- increase markedly through the ammonia-based WFGD, and SO42- is generally the main ionic component, both in CPM and FPM. Notably, the occurrence of elemental Se in FPM and CPM is significantly affected by WFGD. Furthermore, the established chemical profiles in FPM and CPM show a distinct discrepancy. In CPM, the elemental S mainly exists as a sulfate, and the metallic elements of Na, K, Mg, and Ca mainly exist as ionic species. Our results may indicate that not all SO3 are included in CPM and they co-exist in stack plume. With the substantial reduction of sulfur dioxide (SO2), S distributed in SO3, CPM, and FPM becomes non-negligible. Finally, the emission factors of CPM and SO3 under typical ULE technical routes fall in the ranges of 74.33-167.83 and 48.76-86.30 g/(t of coal) accordingly.

Migration and Emission Characteristics of Ammonia/Ammonium through Flue Gas Cleaning Devices in Coal-Fired Power Plants of China.

To investigate the up-to-date migration and emission characteristics of NH3/NH4+ in coal-fired power plants (CFPPs) after implementing ultralow emission retrofitting, typical air pollution control devices (APCDs) in CFPPs, including flue gas denitrification, dust collectors, combined wet flue gas desulfurization (WFGD), and wet precipitators are involved in field measurements. The results show that most of the excessive injected and/or unreacted ammonia from the flue gas denitrification system, whether selective catalytic reduction (SCR) or selective noncatalytic reduction (SNCR), is converted into particle-bound NH4+ (>91%), and the rest (less than 9%) is carried by flue gas in the form of gaseous NH3, with a concentration value of 0.15-0.54 mg/(N m3) at the denitrification outlet. When passing through dust collectors, particle-bound NH4+ concentration decreases substantially along with the removal of particle matter. In WFGD, the dissolution and volatilization effects affect the gaseous ammonia concentration, which decreases when using limestone slurry and a 20% solution of ammonia as a desulfurization agent, while liquid ammonia solution with a high concentration (99.8%) may cause the flue gas NH3 concentration to increase considerably by 13 times. Particle-bound NH4+ concentration is mainly influenced by the relative strength of desulfurization slurry scouring and flue gas carrying effects and increases 2.84-116 times through ammonia-based WFGD. Furthermore, emission factors of NH3 for combinations of APCDs are discussed.

Fine particulate matter pollution in North China: Seasonal-spatial variations, source apportionment, sector and regional transport contributions.

Large areas of mainland China have been suffering frequently from heavy haze pollution during the past years, which feature high concentrations of fine particulate matter (PM2.5, particulate matters with aerodynamic diameters less than 2.5 µm) and low visibility. Moreover, these areas manifested strong regional complex pollution characteristics, particularly in North China including Beijing and the five surrounding provinces (BSFP). In this study, by using the localized comprehensive emission inventory of BSFP region in 2012 as an input, the Comprehensive Air Quality Model with Extensions-Particulate Matter Source Apportionment Technology (CAMx/PSAT) was used to assess the seasonal variations and source apportionment of PM2.5 in the highly polluted BSFP region, with a specific focus on the sectoral and sub-regional contributions to PM2.5 in Beijing during winter and summer. Results showed that the PM2.5 concentrations of BSFP region was higher in winter than that in summer. And the heavily polluted area in BSFP region shrinked noticeably in summer, compared with winter. As for source apportionment of PM2.5, residential and remaining industrial sectors constituted the top two sources of PM2.5 mass concentrations in Beijing. In addition, agricultural source represented a major contributor to ammonium, whereas transportation and power sectors constituted major sources to nitrates. In terms of contributions from sub-regions, the local sources ranked as the dominant contributors to PM2.5 in Beijing, while the main external contributions originated from the surrounding areas, such as Hebei and Shandong. Results of daily source apportionment to PM2.5 in Beijing showed that sub-regional long-distance transport became stronger when haze pollution was severe, in which contribution from remaining industrial sector would be higher than that of other periods. The results will allow for an improved understanding of the causes and origins of heavy regional PM2.5 pollution, and thus will benefit the development of effective joint control policies and identification of key polluting emission categories in North China and ultimately serve as references for other highly polluted megacities in the world.

Combination of Colour Duplex and Contrast Enhanced Ultrasound as an Alternative to Computed Tomography Angiography in Isolated Mesenteric Artery Dissection Surveillance.

OBJECTIVES: The aim was to investigate the effectiveness of colour duplex ultrasound (CDU) plus contrast enhanced ultrasound (CEUS) vs. computed tomography angiography (CTA) for surveillance in patients with isolated mesenteric artery dissection (IMAD). METHODS: Patients who underwent CDU, CEUS, and CTA for surveillance of IMAD between January 2012 and May 2019 were included in the study. The accuracy of CDU, CEUS, and CTA for determining the morphological characteristics of IMAD was analysed. RESULTS: A total of 42 patients undergoing 76 total imaging examinations during follow up were included. Both CTA and CDU plus CEUS demonstrated the thrombosed false lumen for 28 (36.8%) examinations and the dissecting aneurysm for 20 (26.3%) examinations (both κ = 1.0). The diameter of the dissecting aneurysm was 5.03 ± 1.25 mm using CDU and CEUS vs. 5.27 ± 1.23 mm on CTA (coefficient of consistency, 0.997; p < .001). The entry points were visualised by CDU and CEUS for 20 (26.3%) examinations and by CTA for 14 (18.4%) examinations (κ = 0.769); no re-entry points were visualised by CDU and CEUS for any examinations but re-entry points were visualised by CTA for two (2.6%) examinations. The minimum inner diameter was 2.80 ± 1.30 mm on CDU and CEUS vs. 2.52 ± 1.29 mm on CTA (coefficient of consistency, 0.999; p < .001). The peak systolic velocities were 128.2 ± 13.0 cm/s at diagnosis and 98.7 ± 4.9 cm/s after one month (p < .001). CONCLUSIONS: The combination of CDU and CEUS can be used in place of CTA for the surveillance of IMAD.

Effects of Wet Flue Gas Desulfurization and Wet Electrostatic Precipitators on Emission Characteristics of Particulate Matter and Its Ionic Compositions from Four 300 MW Level Ultralow Coal-Fired Power Plants.

To achieve ultralow-emission (ULE) standards, wet electrostatic precipitators (WESP) installed downstream from wet flue gas desulfurization (WFGD) have been widely used in Chinese coal-fired power plants (CFPPs). We conducted a comprehensive field test study at four 300 MW level ULE CFPPs, to explore the impact of wet clean processing (WFGD and WESP) on emission characteristics of three size fractions of particulate matter (PM: PM2.5, PM10-2.5, and PM>10) and their ionic compositions. All these CFPPs are installed with limestone-based/magnesium-based WFGD and followed by WESP as the end control device. Our results indicate that particle size distribution, mass concentration of PM, and ionic compositions in flue gas change significantly after passing WFGD and WESP. PM mass concentrations through WFGD are significantly affected by the relative strength between desulfur slurry scouring and flue gas carrying effects. Concentrations of ions in PM increase greatly after passing WFGD; especially, SO42- in PM2.5, PM10-2.5, and PM>10 increase on average by about 1.4, 3.9, and 8.3 times, respectively. However, WESP before the stack can effectively reduce final PM emissions and their major ionic compositions. Furthermore, emission factors (kg/(t of coal)) of PM for different combinations of air pollution control devices are presented and discussed.

Emissions of volatile organic compounds from Chinese coal-fired power plants: Characteristics, source profile, inventories, and impacts.

Volatile organic compounds (VOCs) are key precursors for secondary organic aerosols (SOA) and ozone, imposing severe impacts on human health and environment. Considering the massive coal consumption, coal fired power plants (CFPPs) in China are non-negligible VOCs contributors, whose emission characteristics remain inadequately understood. Here, we investigated emission characteristics of 117 VOCs by field tests in four typical CFPPs, and a latest localized CFPPs source profile was compiled by integrating literature reviews. Then speciated-VOCs emission inventories for 2018-2022 were established based on dynamic emission factors and unit-level activity data. The results suggested that oxygenated VOCs (OVOCs) constituted the dominant group (76.5 %), with propionaldehyde (32.0 %) and formaldehyde (24.5 %) being the predominant species. OVOCs (93.2 %) and aromatics (77.4 %) were identified as the primary contributors to ozone and SOA, respectively. Driven by both the rise in coal consumption and technological advancements, nationwide VOCs emissions decreased from 83,393 t in 2018 to 53,251 t in 2022. Regional disparities and varying rates of decline in provincial emissions were evident, with VOCs emissions predominantly concentrated in northern and eastern provinces. Neimenggu, Shandong, Shanxi, Jiangsu, and Guangdong were identified as the top five provinces with the highest emissions. We believe this study would be conducive to a more comprehensive understanding and effective control of VOCs emissions from CFPPs in China.

Database of emission factors of volatile organic compound (VOC) species in motor vehicle exhaust in China.

The synergistic strategy for fine particulate matter (PM2.5) and O3 pollution prevention and control has emerged as a pivotal approach in combating air pollution. Volatile organic compounds (VOCs) serve as crucial precursors to both O3 and secondary organic aerosols (SOAs), with motor vehicles representing one of their significant sources. In this study, a standard for establishing a database of VOC species emission factors for motor vehicles was developed, and a database containing 134 VOC species was constructed through field tests and literature surveys. The VOC emissions of light-duty gasoline passenger vehicles (LDGPVs) comprised primarily alkanes and aromatics. The VOC emissions of light-duty diesel trucks (LDDTs) comprised mostly alkanes. Regarding low-speed trucks, 3-wheel vehicles, medium-duty diesel trucks (MDDTs) and heavy-duty diesel trucks (HDDTs), their VOC emissions comprised mainly oxygenated volatile organic compounds (OVOCs). The update of emission standards resulted in a reduction in VOC species emission factors while altering the composition of VOCs. Attention should be directed toward isopentane, benzene and dichloromethane emitted by LDGPVs, dodecane, undecane, ethene and propene emitted by LDDTs, and acetaldehyde emitted by HDDTs. VOC species originating from LDGPVs were more dispersed than those originating from LDDTs and HDDTs. In addition, variations in VOC species were observed among motor vehicles with different fuel types. Toluene, ethene, benzene, m,p-xylene, isopentane, hexanal, ethyne and 1,2,4-trimethylbenzene were the predominant VOC species emitted by gasoline vehicles. Diesel vehicles emitted mainly dodecane, formaldehyde, propene, undecane, acetaldehyde, ethene, decane and benzene. The results could enhance our comprehension of the emission characteristics of VOC species originating from motor vehicles and provide data support and a scientific foundation for achieving synergistic PM2.5 and O3 pollution prevention and control.

Characteristics and reduction assessment of GHG emissions from crop residue open burning in China under the targets of carbon peak and carbon neutrality.

Driven by the goal of carbon peak and carbon neutrality, greenhouse gas (GHG) emissions from the crop residue open burning (CROB) in China cannot be ignored. In this study, we have established a high-resolution (0.05° × 0.05°) GHG emissions inventory (including CO2, CH4, and N2O) of CROB from 2012 to 2021 in China based on the VIIRS data and official statistics. To improve the results accuracy, we compared the two commonly used bases for grid allocation, fire counts (FC) and fire radiative power (FRP), in the construction of high-resolution inventory. In 2012, GHG emissions are overestimated by 599 t CO2e per grid on average in 24,577 grids, and underestimated by 1096 t CO2e per grid on average in 13,546 grids based on FC compared to FRP. Then, we characterized the spatial and temporal distribution of GHG emissions from CROB by using the FRP-based method. From 2012 to 2021, total GHG emissions from CROB in China have decreased by 31.2 %, of which the East and South-Central China contributed 22.51 and 9.12 Tg CO2e of GHG reductions, while the Northeast China contributed 10.73 Tg CO2e of GHG growth, respectively. In addition, GHG emissions from CROB on the time scale are mainly concentrated in April, June, and October, with variations between years and regions influenced by the policy, climate, and farmers' perceptions. Finally, we assessed the GHG emission reductions from CROB under different scenarios in the future. By 2060, GHG emissions would be significantly reduced by 57.3 %-77.9 % compared to 2021 under effective control measures. We believe the results will be of great significance for GHG policy formulation and emission reduction potential assessment.

Classification for thyroid nodule using ViT with contrastive learning in ultrasound images.

The lack of representative features between benign nodules, especially level 3 of Thyroid Imaging Reporting and Data System (TI-RADS), and malignant nodules limits diagnostic accuracy, leading to inconsistent interpretation, overdiagnosis, and unnecessary biopsies. We propose a Vision-Transformer-based (ViT) thyroid nodule classification model using contrast learning, called TC-ViT, to improve accuracy of diagnosis and specificity of biopsy recommendations. ViT can explore the global features of thyroid nodules well. Nodule images are used as ROI to enhance the local features of the ViT. Contrast learning can minimize the representation distance between nodules of the same category, enhance the representation consistency of global and local features, and achieve accurate diagnosis of TI-RADS 3 or malignant nodules. The test results achieve an accuracy of 86.9%. The evaluation metrics show that the network outperforms other classical deep learning-based networks in terms of classification performance. TC-ViT can achieve automatic classification of TI-RADS 3 and malignant nodules on ultrasound images. It can also be used as a key step in computer-aided diagnosis for comprehensive analysis and accurate diagnosis. The code will be available at https://github.com/Jiawei217/TC-ViT.

Real-world emission characteristics of semivolatile/intermediate-volatility organic compounds originating from nonroad construction machinery in the working process.

Detailed emission characterization of semivolatile/intermediate-volatility organic compounds (S/IVOCs) originating from nonroad construction machines (NRCMs) remains lacking in China. Twenty-one NRCMs were evaluated with a portable emission measurement system in the working process. Gas phase S/IVOCs were collected by Tenax TA tubes and analyzed via thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). Particle phase S/IVOCs were collected by quartz filters and analyzed via GC-MS. The average emission factors (EFs) for fuel-based total (gas + particle phase) IVOCs and SVOCs of the assessed NRCMs were 221.45 ± 194.60 and 11.68 ± 10.67 mg/kg fuel, respectively. Compared to excavators, the average IVOC and SVOC EFs of loaders were 1.32 and 1.55 times higher, respectively. Compared to the working mode, the average IVOC EFs under the moving mode (only moving forward or backward) were 1.28 times higher. The IVOC and SVOC EFs for excavators decreased by 69.06% and 38.37%, respectively, from China II to China III. These results demonstrate the effectiveness of emission control regulations. In regard to individual NRCMs, excavators and loaders were affected differently by emission standards. The volatility distribution demonstrated that IVOCs and SVOCs were dominated by gas- and particle-phase compounds, respectively. The mode of operation also affected S/IVOC gas-particle partitioning. Combined with previous studies, the mechanical type significantly affected the volatility distribution of IVOCs. IVOCs from higher volatile fuels are more distributed in the high-volatility interval. The total secondary organic aerosol (SOA) production potential was 104.36 ± 79.67 mg/kg fuel, which originated from VOCs (19.98%), IVOCs (73.87%), and SVOCs (6.15%). IVOCs were a larger SOA precursor than VOCs and SVOCs. In addition, normal (n-) alkanes were suitably correlated with IVOCs, which may represent a backup solution to quantify IVOC EFs. This work provides experimental data support for the refinement of the emission characteristics and emission inventories of S/IVOCs originating from NRCMs.

Real-world emission characteristics and inventory of volatile organic compounds originating from construction and agricultural machinery.

Volatile organic compound (VOC) emissions originating from nonroad mobile sources constitute an important but uncertain source of secondary organic aerosols (SOAs) and ozone (O3). In this study, we investigated the emission factors (EFs) of 120 individual VOC species for 40 machines via gas chromatography-mass spectrometry/flame ionization detection and high-performance liquid chromatography. The results showed that the diesel-based VOC EF for the tested machines was 4.18 ± 2.55 (average ± standard deviation) g/kg fuel, dominated by alkanes (38.20 % ± 18.08 %) and oxygenated VOCs (OVOCs; 30.94 % ± 15.71 %). The machine type, rated power, emission standards, and operating conditions affected the emissions of VOCs and their components, and this effect maybe mostly depends on the fuel combustion efficiency. The VOC species were primarily distributed in the C1-C2 and C4-C6 (based on the carbon number) and B4-B6 (based on the saturated vapor concentration) intervals. Furthermore, the estimated formation potential (FP) values of SOAs and O3 from VOCs were 21.02 ± 15.57 mg/kg fuel and 15.96 ± 11.87 g/kg fuel, respectively. VOC control based on the SOA formation potential (SOAFP) and ozone formation potential (OFP) could be more effective in the mitigation of fine particulate matter (PM2.5) and O3 pollution because the top 5 species ranked by percentage contribution accounted for 83.09 % ± 9.59 % and 51.78 % ± 14.38 % of the estimated SOAFP and OFP, respectively. Finally, the emission estimates showed that the VOC emissions originating from construction and agricultural machinery in China (2020) reached 64.05 and 95.24 Gg, respectively. We provide species-specific VOC EFs and detailed emission characteristics to facilitate a comprehensive understanding of gas emissions originating from nonroad mobile sources and an update of emission inventories and atmospheric chemistry models.