Experimental Investigation on Ablation Behaviors of CFRP Laminates in an Atmospheric Environment Irradiated by Continuous Wave Laser

In order to understand the ablation behaviors of CFRP laminates in an atmospheric environment irradiated by continuous wave laser, CFRP laminates were subjected to a 1080-nm continuous wave laser (6-mm laser spot diameter), with different laser power densities carried out in this paper. The internal delamination damage in CFRP laminates was investigated by C-Scan. The rear- and front-face temperature of CFRP laminates were monitored using the FLIR A 655 sc infrared camera, and the rear-face temperature was monitored by K type thermocouples. The morphology of ablation damage, the area size of the damaged heat affected zone (HAZ), crater depth, thermal ablation rate, mass ablation rate, line ablation rate, etc., of CFRP laminates were determined and correlated to the irradiation parameters. It is found that the area size of the damage HAZ, mass ablation rate, line ablation rate, etc., increased as the laser power densities. The dimensionless area size of the damaged HAZ decreased gradually along the thickness direction of the laser irradiation surface.

The Atmospheric Environment Effects of the COVID-19 Pandemic: A Metrological Study

Since the COVID-19 outbreak, the scientific community has been trying to clarify various problems, such as the mechanism of virus transmission, environmental impact, and socio-economic impact. The spread of COVID-19 in the atmospheric environment is variable and uncertain, potentially resulting in differences in air pollution. Many scholars are striving to explore the relationship between air quality, meteorological indicators, and COVID-19 to understand the interaction between COVID-19 and the atmospheric environment. In this study, we try to summarize COVID-19 studies related to the atmospheric environment by reviewing publications since January 2020. We used metrological methods to analyze many publications in Web of Science Core Collection. To clarify the current situation, hotspots, and development trends in the field. According to the study, COVID-19 research based on the atmospheric environment has attracted global attention. COVID-19 and air quality, meteorological factors affecting the spread of COVID-19, air pollution, and human health are the main topics. Environmental variables have a certain impact on the spread of SARS-CoV-2, and the prevalence of COVID-19 has improved the atmospheric environment to some extent. The findings of this study will aid scholars to understand the current situation in this field and provide guidance for future research.

[Emission Characteristics of Gas-and Particle-Phase Polycyclic Aromatic Hydrocarbons from Cooking]

Polycyclic aromatic hydrocarbons (PAHs) play a key role in the formation of secondary organic areole and ozone. This study sampled three commercial Chinese restaurants and a food plant in Shenzhen to analyze the emission characteristics of PAHs, especially the alkyl PAHs in both gas and particle phases. The results showed that the ρ(total PAHs)in the particle and gas phase were (1381.6±140.5) ng·m^-3, (1030.2±116.4) ng·m^-3, (908.3±111.9) ng·m^-3, and (838.0±93.5) ng·m^-3 in the food plant, Sichuan, Cantonese, and Zhejiang restaurants, respectively. More than 60% of the PAHs were distributed in the gas phase, especially the lower molecular weight PAHs (lower than Chrysene). The gas phase proportion of naphthalene was the highest, with over 75% of it distributed in the gas phase. However, the PAHs with a higher molecular weight than that of benzo(b)fluorescence were mainly distributed in the particle phase. The total concentration of alkyl PAHs emitted from cooking was much lower than that of the corresponding parent PAHs, and the distribution characteristics of alkyl PAHs were quite different from those of other emission sources. The linear fitting of lgK_p and lgP_L showed that the slopes of the three commercial restaurants ranged from -0.25 to -0.28, whereas for the food plant, the value was -0.18, which indicates that the gas-particle partitioning of PAHs were not in equilibrium.

[Wildfire smoke injection heights in China based on multi-angle imaging spectroradiometer (MISR) observations]

Smoke injection height is a key driving factor for plume transport, which determines the lifetime of smoke aerosol in the atmosphere, transport path and diffusion along with the wind, and impacts on atmospheric environment. In this study, raw data obtained from the latest multi-angle imaging spectroradiometer (MISR) plume height project was extracted and analzyed. The variation of smoke injection heights of wildfire in China was investigated with statistical analysis methods. The effects of fire characteristics (combustion biomass type and fire radiative power) on the smoke injection height were explored. Meanwhile, the influence of smoke injection heights on the atmospheric environment was discussed based on the proportion of higher injection height plumes and the value of smoke aerosol optical depth (AOD). The results showed that smoke injection heights from wildfire ranged from 345 to 7719 m, with 57.1% of which ranging from 500 to 1000 m. Except for an abnormally high value of smoke injection height from a large grassland fire, the rest of smoke injection heights were lower than 3000 m. The biomass type for combustion was an important factor affecting smoke injection heights. The injection heights of the plume caused by forest fire were the highest and had the greatest variability. Smoke injection heights increased with the fire radiation power, but with obvious dispersion (R²=0.19). By setting a simple threshold, the proportion of higher injection plumes which might cause long-distance transportation of air pollutants in China was 10.5%. Combined with the analysis of smoke AOD, it was found that the average smoke injection height from cropland burning was the lowest, but their smoke caused the highest regional air pollution. In contrast, although forest fires could produce the highest smoke injection height, their smoke had a lower average value of AOD, which indicated a relatively weak impact of forest fires on regional air quality.

[Optimization Method and Case Study of Air Pollution Emission Spatial Pattern]

Few of the current methods of improving air quality, including end-pipe treatment, industrial, energy and transportation structure adjustments, are from the viewpoint of the spatial pattern optimization of pollutant emissions. Therefore, based on factors such as natural environment, human health, pollutant transmission capability, and meteorological diffusion conditions, our research group used the threshold approach, natural breaks, spatial erasure, and other methods to define the layout area suitable for atmospheric pollution sources. Based on these results, the emissions pattern was optimized to achieve air quality improvement. Taking Guangdong Province as an example, we examined the application of the emissions pattern optimization of air quality improvement and atmospheric environment zoning. The results indicate that the first class area of environmental air quality accounts for 9% of total province area, the densely populated area accounts for 3%, the sensitive area of the national air quality monitor stations accounts for 15%, the pollutant accumulation area accounts for 22%, and the layout area suitable for atmospheric pollution sources primarily distributed in the west part of the province accounts for 60%. By shifting the non-thermal power industrial sources into those area, the concentration level of PM_2.5 will decrease by 4% at the provincial scale and 10% at the city scale. Emissions pattern optimization has become an innovative aided support technology for the continuous improvement of air quality. In practical applications, it can be combined with energy and industrial structure adjustments, pollution control technology enhancements, and cross-regional prevention and control to formulate the most feasible air quality improvement plan.

[Review of Screening and Applications of Organic Tracers in Fine Particulate Matter]

Specific organic compounds within atmospheric particulate matter are indicators of specific pollution sources and, as such, can be used to differentiate inputs from various air pollution emissions sources in urban areas. Therefore, many studies have been conducted to detect organic particulate matter and screen the associated organic tracers that provide provenance information. This review provides a brief summary of the emission characteristics of biomass burning, cooking, fossil fuel combustion, and traffic. The particular marker compounds that carry provenance information for these four emission sources are discussed and diagnostic ratios are calculated to discuss the use of organic tracers in source apportionment. The shortcomings and new directions of using source tracer screening are also discussed.

Regional and Urban-Scale Environmental Influences of Oceanic DMS Emissions over Coastal China Seas

Marine biogenic dimethyl sulfide (DMS) is an important natural source of sulfur in the atmosphere, which may play an important role in air quality. In this study, the WRF-CMAQ model is employed to assess the impact of DMS on the atmospheric environment at the regional scale of eastern coastal China and urban scale of Shanghai in 2017. A national scale database of DMS concentration in seawater is established based on the historical DMS measurements in the Yellow Sea, the Bohai Sea and the East China Sea in different seasons during 2009~2017. Results indicate that the sea-to-air emission flux of DMS varies greatly in different seasons, with the highest in summer, followed by spring and autumn, and the lowest in winter. The annual DMS emissions from the Yellow Sea, the Bohai Sea and the East China Sea are 0.008, 0.059, and 0.15 Tg S a⁻¹, respectively. At the regional scale, DMS emissions increase atmospheric sulfur dioxide (SO₂) and sulfate (SO42−) concentrations over the East China seas by a maximum of 8% in summer and a minimum of 2% in winter, respectively. At the urban scale, the addition of DMS emissions increase the SO₂ and SO42− levels by 2% and 5%, respectively, and reduce ozone (O₃) in the air of Shanghai by 1.5%~2.5%. DMS emissions increase fine-mode ammonium particle concentration distribution by 4% and 5%, and fine-mode nss-SO42− concentration distributions by 4% and 9% in the urban and marine air, respectively. Our results indicate that although anthropogenic sources are still the dominant contributor of atmospheric sulfur burden in China, biogenic DMS emissions source cannot be ignored.

[Emission Characteristics of Particulate Organic Matter from Cooking]

Cooking is an important source of atmospheric particulate organic matter (POM). In this study, four Chinese restaurants in Shenzhen (west style, dim-sim restaurant, worker's canteen, and Korean cuisine) were sampled to examine the chemical composition of POM and research molecular tracers. The result showed that more than 60% of the PM_2.5 mass was due to organic compounds. For the quantified organic compounds, the results indicated that fatty acids, dicarboxylic acids, and n-alkanes were the major organic compounds emitted from all cooking styles, PAHs, sterols, and monosaccharide anhydrides were found at relatively low levels. The composition of POM was strongly influenced by cooking style. The cooking styles of the west and Korean restaurant emitted the most abundant fatty acids, n-alkanes, and PAHs, but the least sterols and monosaccharide anhydrides, whereas the dim-sim restaurant and worker's canteen displayed the opposite results. The values of Fla/(Fla+Pyr) and LG/(Gal+Man) provided candidate tracers for cooking because they were less influenced by the cooking styles and were significantly different from other pollutant sources. Furthermore, cooking contributed significant amounts of fatty acids and dicarboxylic acids to atmospheric PM in Shenzhen.

Corrosion Behavior of SMA490BW Steel and Welded Joints for High-Speed Trains in Atmospheric Environments

Currently, high-speed trains work under various atmospheric environments, and the bogie as a key component suffers serious corrosion. To investigate the corrosion behavior of bogies in industrial atmospheric environments, the periodic immersion wet/dry cyclic corrosion test for SMA490BW steel and automatic metal active gas (MAG) welded joints used for bogies was conducted in the present work. Corrosion weight loss rate, structure, and composition of rust layers as well as electrochemistry parameters were investigated. The results showed that the corrosion weight loss rate decreased with increasing corrosion time; furthermore, the corrosion weight loss rate of the welded joints was lower than that of SMA490BW steel. The XRD results showed that the rust layers formed on SMA490BW steel and its welded joints were mainly composed of α-FeOOH, γ-FeOOH, Fe₂O₃, and Fe₃O₄. The observation of surface morphology indicated that the rust layers of the welded joints were much denser and had a much finer microstructure compared with those of SMA490BW steel. After corrosion for 150 h, the corrosion potential of the welded joints with rust layers was higher than that of SMA490BW steel. In short, the welded joints exhibited better corrosion resistance than SMA490BW steel because of the higher content of alloy elements, as shown in this work.

Atmospheric Environment Vulnerability Cause Analysis for the Beijing-Tianjin-Hebei Metropolitan Region

Assessing and quantifying atmospheric vulnerability is a key issue in urban environmental protection and management. This paper integrated the Analytical hierarchy process (AHP), fuzzy synthesis evaluation and Geographic Information System (GIS) spatial analysis into an Exposure-Sensitivity-Adaptive capacity (ESA) framework to quantitatively assess atmospheric environment vulnerability in the Beijing-Tianjin-Hebei (BTH) region with spatial and temporal comparisons. The elaboration of the relationships between atmospheric environment vulnerability and indices of exposure, sensitivity, and adaptive capacity supports enable analysis of the atmospheric environment vulnerability. Our findings indicate that the atmospheric environment vulnerability of 13 cities in the BTH region exhibits obvious spatial heterogeneity, which is caused by regional diversity in exposure, sensitivity, and adaptive capacity indices. The results of atmospheric environment vulnerability assessment and the cause analysis can provide guidance to pick out key control regions and recognize vulnerable indicators for study sites. The framework developed in this paper can also be replicated at different spatial and temporal scales using context-specific datasets to support environmental management.

[Air Quality Subarea Management:A Case Study of Guangdong Province]

To meet the requirements of regional air quality management (AQM), the Air Quality Subarea Management (AQSM) system was proposed. A case study was conducted for Guangdong Province. By using the method of air quality numerical simulation and satellite remote sensing inversion analysis, the key factors were selected from the meteorological simulation field, the pollutant concentration simulation field, and the satellite image interpretation to form the index system for AQSM. On this basis, a hierarchical cluster analysis method was used to divide Guangdong Province into three types of AQSM:Strict Control Subarea, Continuous Improvement Subarea, and Coordinated Development Subarea. It was shown that the Strict Control Subarea, Continuous Improvement Subarea, and Coordinated Development Subarea in Guangdong Province covered 16.3%, 28.0%, and 55.7%, respectively. The Strict Control Subarea in the Pearl River Delta, Eastern Guangdong, Western Guangdong, and Northern Guangdong accounted for 27.9%, 19.3%, 4.4%, and 12.5%, respectively, and the subarea should implement the most stringent AQM policies to promote air quality improvement. The Continuous Improvement Subarea in the Pearl River Delta, Eastern Guangdong, Western Guangdong, and Northern Guangdong accounted for 34.4%, 15.8%, 7.8%, and 34.5%, respectively, and the subarea should implement relatively strict AQM policies to ensure sustained and stable standards. The Coordinated Development Subarea in the Pearl River Delta, Eastern Guangdong, Western Guangdong, and Northern Guangdong accounted for 37.7%, 64.9%, 87.8%, and 53.0%, respectively, and the subarea could implement more liberal AQM policies to ensure relatively good air quality. In general, the strict AQM policies in Guangdong Province should be mainly concentrated in the Pearl River Delta region, followed by Northern Guangdong, Eastern Guangdong, and Western Guangdong in order.

Environmental Change in the Agro-Pastoral Transitional Zone, Northern China: Patterns, Drivers, and Implications

Chengde city is located in the agro–pastoral transitional zone in northern China near the capital city of Beijing, which has experienced large-scale ecological construction in the past three decades. This study quantitatively assessed the environmental changes in Chengde through observation records of water resources, water environment, atmospheric environment, and vegetation activity and investigated the possible causes. From the late 1950s to 2002, the streamflow presented a downward trend induced by climate variability and human activities, with contribution ratios of 33.2% and 66.8%, respectively. During 2001–2012, the days of levels I and II air quality presented clear upward trends. Moreover, the air pollutant concentration was relatively low compared with that in the adjacent areas, which means the air quality has improved more than that in the neighboring areas. The water quality, which deteriorated during 1993–2000, began to improve in 2002. The air and water quality changes were closely related to pollutant emissions induced by anthropogenic activities. During 1982–2012, the vegetation in the southeastern and central regions presented restoration trends, whereas that in the northwestern area showed degradation trends. The pixels with obvious degradation trends correlated significantly with annual mean temperature and annual precipitation. Ecological engineering also played a positive role in vegetation restoration. This analysis can be beneficial to environment managers in the active response and adaptation to the possible effects of future climate change, population growth, and industrial development and can be used to ensure sustainable development and environmental safety.