Quantitative relationship between the structures and properties of VOCs and SOA formation on the surfaces of acidic aerosol particles.

In this research, all the efforts, based on a series of molecular dynamics simulations on the interfacial process between VOC-contaminated air and acidic sulfate, were made to find how the structures and properties of VOCs are related to the formation of SOAs. The experimental fractional aerosol coefficients (FACs) were used to quantify the SOA formation and 14 VOC species were chosen based on the atmosphere inventory and the FAC magnitude. Finally, the quantitative relationship (QR) was found through the FAC as a function of the two variables the total valid interactions (Tg) and the diffusion coefficient (D), with R square 0.94. Meanwhile, the effect of water was explored and the QR was proved to be rational and reliable. The QR not only explained the SOA formation capacity of VOCs, but could also predict the SOA formation of new molecules.

Implications of ozone transport on air quality in the Sichuan Basin, China.

Ozone pollution is formed through complex chemical and physical processes closely associated with emissions, photochemical reactions, and meteorological conditions. The objective of this study is to quantify the contributions of meteorological chemical formation, vertical transport, and horizontal transport to air quality during spring and summer in different regions of the Sichuan Basin. The Community Multi-scale Air Quality (CMAQ) with the Integrated Process Rate (IPR) was employed to simulate the months of April and July 2021 in the Sichuan Basin. The results indicate that both the spring and summer chemical formation of ozone in the urban centre show negative values, while the surrounding urban areas contribute positively, with chemical formation ranging from 0 to 10 µg·m-3. The maximum ozone level due to horizontal transport in the urban centre exceeds 20 µg·m-3, whereas horizontal transport in the surrounding urban areas exhibits negative values, with transport contributions concentrated within the range of -5 to 0 µg·m-3. The vertical transport in the central and southern parts of the basin shows positive values, with transport contributions ranging from 0 to 10 µg·m-3, and the urban centre exhibits relatively stronger vertical transport with contributions ranging from 10 to 20 µg·m-3. Although the chemical formation contribution in the urban centre is relatively small due to high nitrogen oxide emissions, vertical and horizontal transport play significant roles and are among the key factors contributing to ozone pollution formation.

[Analysis of the Impact of Fireworks on Air Quality During the Spring Festival in Chengdu from 2019 to 2022].

Based on the observation data of air quality and PM2.5 components, the influence of fireworks on pollutant concentrations, PM2.5 components, and secondary transformation during the Spring Festival period from 2019 to 2022 in Chengdu were analyzed. The results indicated that the fireworks had a greater impact on the concentration of SO2, PM2.5, and PM10 than the other pollutants. During the centralized discharge of fireworks from 2019 to 2022, the average hourly concentrations of SO2, PM2.5, and PM10 increased by 6.7, 105.0, and 117.4 µg·m-3, with an increase of 135%, 236%, and 203%, respectively. During the centralized discharge period of fireworks, the contributions of fireworks to the SO2, PM2.5, and PM10 concentration were 10.0%-34.0%, 28.1%-31.3%, and 27.8%-34.6%, respectively. The impact time of fireworks on air quality decreased slightly, from 42 h in 2019 to 38 h in 2022; however, the impact on PM2.5 concentration fluctuated, and the impact in 2022 was similar to that in 2019. The main components of fireworks were K, Cl, Al, K+, and Cl-; the concentrations of these components were high and increased rapidly during the concentrated discharge, accounting for 5%-18% of PM2.5, with an increase rate of 87%-1511%. The discharge of fireworks had little effect on NH4+, V, Cd, and Co, and the variation range was within±20%. Throughout the pollution period during the Spring Festival, the mass concentrations of the main components of fireworks were 4.9-31.7 times and 7.4-68.2 times that of the heavy pollution and good weather before the Spring Festival, and their proportions increased by 4%-8%. Secondary sources; fireworks; and biomass burning, coal burning, and industry were the main sources of PM2.5 during the 2019-2022 Spring Festival. The contribution rate of fireworks and biomass combustion was 13%-25%, with higher contribution rates in 2019 and 2022. From the perspective of the impact of meteorological conditions on fireworks discharge, high humidity, low wind speed, and low temperature will intensify the impact of firework discharge on air quality and vice versa. Wind speed mainly affected Al, K+, Cl-, and SO42-, whereas relative humidity mainly affected secondary components such as NO3- and NH4+.

Cellulose Nanofiber-Assisted Dispersion of Halloysite Nanotubes via Silane Coupling Agent-Reinforced Starch-PVA Biodegradable Composite Membrane.

HNTs (halloysite nanotubes) are widely used in reinforcing material, often used in material reinforcement and particle loading. However, their easy agglomeration causes them to have great limitations in application. In this work, two kinds of silane coupling agents (KH560 and KH570) were introduced to graft the CNF/HNT (cellulose nanofiber) nanoparticles used to reinforce the starch-polyvinyl alcohol (PVA) composite membranes. The mechanical properties, water resistance properties and thermal performance of the composite membrane were tested. The results showed that the CNF/HNTs nanoparticle system modified by two silane coupling agents enhanced the tensile strength (TS) of the starch-PVA composite membranes by increments of 60.11% and 68.35%, and, in addition, the water resistance of starch-PVA composite membrane improved. The introduction of chemical bonds formed associations and a compact network structure, which increased the thermal stability and the crystallinity of the starch-PVA composite membrane. In the study, we creatively used CNF to disperse HNTs. CNF and HNTs were combined under the action of the silane coupling agent, and then mixed into the starch-PVA membranes matrix to prepare high-performance degradable biological composite membranes.

Carbon Reduction of the Three-Year Air Pollution Control Plan under the LEAP Model Using a GREAT Tool in Panzhihua, China.

In the context of global warming and climate change, various international communities have set different reduction targets for carbon emissions. In 2020, China proposed that CO2 emissions will peak by 2030 and reached a critical period in which carbon reduction is a key strategic direction. Sichuan Academy of Environmental Sciences published the "Panzhihua Three-Year Iron Fist Gas Control Action Plan" in 2021. The measures implemented in the plan only address general considerations of conventional pollutants in the atmosphere. This study established the Panzhihua LEAP model based on the GREAT tool and built four simulation scenarios, including pollutant treatment upgrade (PTU), traffic improvement (TI), boiler remediation (BR), and baseline scenarios for industrial sources, mobile sources, and industrial boilers in policy implementation. It provided a supportive basis for the development of environmental protection measures in Sichuan province to increase the efficiency of carbon emission reduction. The quantitative analysis of the simulation results for the five years from 2020 to 2024 was conducted to discuss the intrinsic links between carbon emissions and energy consumption, market storage, and demand under different scenarios. It concluded that the BR and TI scenarios benefit carbon reduction, while the PTU scenario negatively impacts it. This study provided recommendations for analyzing the carbon footprint at a city-wide level, quantifying the relationship between the implementation of relevant environmental measures and carbon emissions, which are available for policy development that incorporates carbon reduction considerations and offers relevant support for future research.

Study on Emission Characteristics and Emission Reduction Effect for Construction Machinery under Actual Operating Conditions Using a Portable Emission Measurement System (Pems).

With the acceleration of urban construction, the pollutant emission of non-road mobile machinery such as construction machinery is becoming more and more prominent. In this paper, a portable emissions measurement system (PEMS) tested the emissions of eight different types of construction machinery under actual operating conditions and was used for idling, walking, and working under the different emission reduction techniques. The results showed that the pollutant emission of construction machinery is affected by the pollutant contribution of working conditions. According to different emission reduction techniques, the diesel oxidation catalyst (DOC) can reduce carbon monoxide (CO) by 41.6-94.8% and hydrocarbon (HC) by 92.7-95.1%, catalytic diesel particulate filter (CDPF) can reduce particulate matter (PM) by 87.1-99.5%, and selective catalytic reduction (SCR) using urea as a reducing agent can reduce nitrogen oxides (NOx) by 60.3% to 80.5%. Copper-based SCR is better than vanadium-based SCR in NOx reduction. In addition, the study found that when the enhanced 3DOC + CDPF emission reduction technique is used on forklifts, DOC has a "low-temperature saturation effect", which will reduce the emission reduction effect of CO and THC. The use of Burner + DOC + CDPF emission reduction techniques and fuel injection heating process will increase CO's emission factors by 3.2-3.5 and 4.4-6.7 times compared with the actual operating conditions.

Site location optimization of regional air quality monitoring network in China: methodology and case study.

Regional air quality monitoring networks (RAQMN) are urgently needed in China due to increasing regional air pollution in city clusters, arising from rapid economic development in recent decades. This paper proposes a methodological framework for site location optimization in designing a RAQMN adapting to air quality management practice in China. The framework utilizes synthetic assessment concentrations developed from simulated data from a regional air quality model in order to simplify the optimal process and to reduce costs. On the basis of analyzing various constraints such as cost and budget, terrain conditions, administrative district, population density and spatial coverage, the framework takes the maximum approximate degree as an optimization objective to achieve site location optimization of a RAQMN. An expert judgment approach was incorporated into the framework to help adjust initial optimization results in order to make the network more practical and representative. A case study was used to demonstrate the application of the framework, indicating that it is feasible to conduct site optimization for a RAQMN design in China. The effects of different combinations of primary and secondary pollutants on site location optimization were investigated. It is suggested that the network design considering both primary and secondary pollutants could better represent regional pollution characteristics and more extensively reflect temporal and spatial variations of regional air quality. The work shown in this study can be used as a reference to guide site location optimization of a RAQMN design in China or other regions of the world.

Rapid degradation of tetracycline hydrochloride by heterogeneous photocatalysis coupling persulfate oxidation with MIL-53(Fe) under visible light irradiation.

This work demonstrates a facile route to assemble MIL-53(Fe) by solvothermal method. Sulfate radical-based advanced oxidation processes (SR-AOPs) coupling with photocatalysis based on MIL-53(Fe) were investigated under visible light. The catalytic effect of MIL-53(Fe) for the degradation of tetracycline hydrochloride (TC-HCl) was systematically studied, as well as the reusability of the catalyst and the effect of operating parameters. The results indicated that 99.7 % of TC (300 mg/L) could be degraded within 80 min in the SR-AOPs coupling with photocatalysis processes, as compared to 71.4 % for the SR-AOPs and only 17.1 % for the photocatalysis. The trapping experiments and electron spin-resonance spectroscopy (ESR) showed the photogenerated electrons of MIL-53(Fe) under visible light irritation were trapped by persulfate to generated sulfate radicals which effectively suppressed the recombination of photogenerated carriers. And also, the SO4- could be formed by the conversion between Fe (Ⅲ) and Fe (Ⅱ) in MIL-53(Fe). Moreover, OH and O2- generated by the reaction increased significantly due to the increase of SO4- which generated more OH and reduced photogenerated carrier recombination respectively. Thus, the degradation efficiency of TC-HCl was improved. Furthermore, the degradation pathway for TC-HCl was proposed using the theoretical calculations and liquid chromatography coupled with mass spectrometry.

[Analysis of Characteristics of Water-soluble Ions in PM2.5 in Chengdu Based on the MARGA].

Water-soluble ions in PM2.5 were serially on-line monitored using the MARGA sampling and measurement system in Chengdu in 2019. Pollution characteristics of water-soluble ions were analyzed using the meteorological monitoring data. The results show that variations in the concentrations of eight water-soluble ions were consistent with the variations in PM2.5 in Chengdu. The annual average mass concentration of the total water-soluble ions was (20.2±12.7) µg ·m-3, accounting for 48.6% of the PM2.5 mass, which indicates that water-soluble ions were the major components of PM2.5. The mass concentrations of all the ions were in the order of NO3- > SO42- > NH4+ > Cl- > Ca2+ > K+ > Mg2+ > Na+. The annual average mass concentration of secondary ions was (20.2±12.7) µg ·m-3, accounting for 87.2% of total water-soluble ions. The concentrations of total water-soluble ions in different seasons were in the order of winter > spring ≈ autumn > summer. Monthly variations in total water-soluble ion concentrations followed a U-shaped curve; mass concentrations were the highest in January and December and lowest from June to August. Monthly variations in the concentrations of NO3-, SO42-, NH4+, Cl-, Na+, and K+ were consistent with the total water-soluble ion concentrations, while the concentrations of Ca2+ and Mg2+ were the highest in June. Visibility declined with the increase in the concentration of water-soluble ions, especially secondary water-soluble ions regardless of the rainfall. Light rain (accumulated rainfall in 24 h <10 mm) had no scavenging effect on water-soluble ions, while moderate and heavy rainfall had a significant effect. There was a significant positive correlation between NO3-, SO42-, and NH4+ (all the correlation coefficients were over 0.7), indicating that the mechanisms of evolution of secondary water-soluble ions in the atmosphere are highly similar to each other. The annual mean values of SOR and NOR were 0.42 and 0.12, respectively, which were negatively correlated with temperature and O3 and positively correlated with humidity, indicating that the main source of SO42- was heterogeneous oxidation reactions in the liquid phase and the main source of NO3- was heterogeneous oxidation reactions at night. The annual mean values of CE/AE and NR were 1.2 and 1.1, respectively, indicating that most aerosols in the study area were relatively alkaline. The atmospheric environment of Chengdu is rich in ammonia; thus, (NH4)2 SO4 and NH4NO3 were the main forms of secondary ions.

[Emission Inventory and Characteristics of Anthropogenic Air Pollution Sources Based on Second Pollution Source Census Data in Sichuan Province].

In this research, the activity data of Sichuan Province were collected using bottom-up and top-down methods. According to the second survey of pollution sources, the activity data of industrial source includes information of 11020 boilers and 60078 industrial enterprises. Data of 19152 industrial enterprises were collected in Chengdu, accounting for 32% of the total number of enterprises in Sichuan Province. The anthropogenic air pollutant emission inventory of 9 km×9 km was developed for Sichuan Province in 2017 with the use of appropriate emission estimation methods. The results showed that the total emission of SO2,NOx,CO,PM10,PM2.5,BC,OC,VOCs, and NH3 in Sichuan were 308.6×103, 725.7×103, 3131.2×103, 927.6×103, 422.4×103, 30.2×103, 72.0×103, 600.9×103, and 887.1×103 t. The fixed combustion source and process source mainly contributed as sources of SO2. The main source of CO was the process source and mobile source. Further, the dust source and process source were the main sources of PM10 and PM2.5, and the dust source was the largest source of BC and OC contributions. The emission sources of the VOCs were primarily the process sources, mobile sources and solvent use sources. The NH3 emissions were mainly from livestock and poultry breeding and nitrogen fertilizer applications. The spatial distribution results showed that the pollutants were mainly concentrated in the densely populated Sichuan basin and Panzhihua region, where industry and agriculture were relatively developed. The high value points are concentrated along the Deyang-Chengdu-Meishan-Leshan line in Chengdu Plain. The emission inventory established in this study still has certain uncertainties, and the accuracy of activity level data acquisition should be further enhanced. Moreover, pollutant emission factor testing should be carried out for typical pollution sources, and grid emission inventory should be improved to provide scientific support for the prevention and control of air pollution in Sichuan Province in the future.

[Characteristics and Formation Mechanism of Three Haze Pollution Processes in Chengdu in Winter].

Based on the online monitoring data of gaseous pollutants and components in PM2.5 from Chengdu super observatory of atmospheric environment, the meteorological factors and component characteristics of three haze pollution process in Chengdu from 2019 to 2020 were analyzed. The CMB model was adopted to simulate the sources and variation trends of PM2.5 pollution during the study period, and the causes of each pollution process were analyzed. The results showed that all the three pollution processes occurred under adverse meteorological conditions, where the relative humidity and temperature continued to rise and the wind speed and boundary layer height continued to decrease. The average daily relative humidity was greater than 70%, average daily temperature was greater than 8℃, average daily wind speed was less than 0.8 m ·s-1, and average daily boundary layer height was less than 650 m. During the three events of pollution, the main components were NO3-, OC, NH4+, and SO42-. Among them, the mass concentration and proportion of NO3- increased by 1.47-2.09 and 0.22-0.35 times, respectively, during the pollution period as compared to those during the clean period. NO3- was a key component of PM2.5 pollution during winter in Chengdu. During the three pollution processes, the mean values of SOR and NOR were 0.40 and 0.27, respectively, and the secondary transformation degree of SO2 and NOx was high. The conversion of SO2 to SO42- was mainly dominated by heterogeneous oxidation at night, and the conversion of NOx to NO3- was dominated by heterogeneous hydrolysis. The characteristics of the three processes were slightly different. Process Ⅰ showed evident secondary nitrate-dominated characteristics. During the period of rising PM2.5 concentration in process Ⅱ, it was mainly affected by coal emissions, but during the periods of high PM2.5 concentration, it was mainly affected by NO3-. Process Ⅲ was also a nitrate-dominated process, but emissions of fossil fuel combustion had increased during certain polluted periods. Secondary nitrate, secondary sulfate, motor vehicles, and coal combustion were the main pollution sources during the study period. The PM2.5 concentration was positively correlated with the contribution of secondary nitrate and negatively correlated with the contribution of dust source.

[Fine Particulate Matter Source Profile of Typical Industries in Sichuan Province].

An electrical low pressure impactor particle monitor was used to monitor typical industries in Sichuan Province, such as cement, glass, ceramic, brick-tile, coal-fired boiler, biomass boiler, power plant, and steel industry. Fine particulate matter source profiles of each industry were developed based on the laboratory analysis. The results showed that Si, Ca, and Mg were the major elements of building industry particulate matter emission. Sulfate emission from double sodium-calcium was higher than from other desulfurization technologies in the building industry. The main chemical components of PM2.5 from power plants were SO42-, Ca2+, NH4+, Mg, and Si, while OC, Al, Si, and Ca were the main chemical components of PM2.5 from coal-fired boilers. The content of OC was the most abundant in biomass briquette boiler particulate matter emissions, followed by K and EC. In term of the biomass fuel boiler PM2.5 source profile, OC, EC, and Cl- were the major chemical components. Ca was the largest component of PM2.5 from the steel industry, accounting for 18.11% of the total PM2.5 emission, followed by SO42-, Na+, and Fe.

[Agricultural Ammonia Emission Inventory and Its Spatial Distribution in Sichuan Province from 2005 to 2014].

Based on the urban activity data and emission factors, agricultural ammonia emission inventory was developed for Sichuan province from year 2005 to 2014. Meanwhile, its historical trends, spatial distribution and the relationship between agricultural ammonia emission and PM10 concentration were analyzed. The results showed that the highest emission was estimated to be 111.9×104 t in 2006, which was reduced to 95.5×104 t in 2014. The interannual variation characteristics were different for 21 cities in Sichuan, the annual emission of Chengdu, Meishan, Zigong, Luzhou, Yibin, Panzhihua, Aba and Ganzi changed largely in the study period. Livestock source and nitrogen fertilizers were the major contributors, accounting for 72%-79% and 20%-27% of the total agricultural NH3 emission respectively. Hog, poultry and cow were the major contributors under the category of livestock sources for the most cities. It's worth mentioning that rabbit was the largest contributor in Zigong, accounting for 39% of the total livestock NH3 emission. The urban and sub-urban areas of Chengdu, the northeastern and southern part of Sichuan were the hot-spots for agricultural NH3 emission. In term of spatial distribution, there were higher emissions in the east of Sichuan and other suburban and rural areas. There was a good agreement between agricultural NH3 emission and PM10 concentration, indicating agricultural NH3 emission played an important role in the particle formation.

[Emission Inventory of Crop Residues Field Burning and Its Temporal and Spatial Distribution in Sichuan Province].

Based on the collected activity data, the 2012 emission inventory of crop residues field burning in Sichuan province was developed through the emission factor approach. Besides, the temporal and spatial distribution of pollutant emissions was also analysed in this paper. The results showed that the total emissions of SO2, NO(x), NH3, CH4, NMVOC, CO, PM2.5, EC and OC from crop residues field burning in Sichuan province in the year of 2012 were 1 210, 12 185, 2 827, 20 659, 40 463, 292 671, 39 277, 1 984 and 10 215 t, respectively; The rice straw, wheat straw, corn straw and oil rape straw were four major contributors to pollutant emissions, with a total contribution about 88% - 94%; Crop residues field burning emissions were affected by agricultural harvesting. Temporally, the emissions were concentrated in July and August with a small peak in May; Spatially, the Chengdu plain, the Northern area and the Eastern area of Sichuan province were the highest emission areas, while the Western area had relatively low emissions; The key uncertain sources included emission factors and parameters used for estimating crop burning amounts.

Industrial sector-based volatile organic compound (VOC) source profiles measured in manufacturing facilities in the Pearl River Delta, China.

Industrial sector-based VOC source profiles are reported for the Pearl River Delta (PRD) region, China, based source samples (stack emissions and fugitive emissions) analyzed from sources operating under normal conditions. The industrial sectors considered are printing (letterpress, offset and gravure printing processes), wood furniture coating, shoemaking, paint manufacturing and metal surface coating. More than 250 VOC species were detected following US EPA methods TO-14 and TO-15. The results indicated that benzene and toluene were the major species associated with letterpress printing, while ethyl acetate and isopropyl alcohol were the most abundant compounds of other two printing processes. Acetone and 2-butanone were the major species observed in the shoemaking sector. The source profile patterns were found to be similar for the paint manufacturing, wood furniture coating, and metal surface coating sectors, with aromatics being the most abundant group and oxygenated VOCs (OVOCs) as the second largest contributor in the profiles. While OVOCs were one of the most significant VOC groups detected in these five industrial sectors in the PRD region, they have not been reported in most other source profile studies. Such comparisons with other studies show that there are differences in source profiles for different regions or countries, indicating the importance of developing local source profiles.