Vertical Distribution Characteristics Research Articles

Vertical Pollution Characteristics and Source Analysis of Soil PAHs in Different Land Use Types

In order to study the vertical pollution characteristics of polycyclic aromatic hydrocarbons (PAHs) in soils of different land use types in suburban areas of Nanjing, 15 types of controlled PAHs were studied in each section (0-100 cm) of soils from six different land use types, including a vegetable field, forestland, residential area, urban land, paddy field, and industrial area. The vertical distribution and composition characteristics, influencing factors, and sources of PAHs were analyzed. The results showed that:the total concentrations of Σ15PAHs in the six sampling site profiles were as follows:vegetable field (69.3-299.2 μg·kg-1), forestland (20.8-128.3 μg·kg-1), residential area (30.7-142.1 μg·kg-1), urban land (185.6-1728.7 μg·kg-1), paddy field (208.3-693.0 μg·kg-1), and industrial area (165.6-739.2 μg·kg-1). There was no pollution in the residential area or forestland and a light pollution level in the vegetable field, medium pollution level in the paddy field and industrial area, and more serious pollution in the urban land. Soil PAHs were mainly distributed in the surface or subsurface layer, except in the residential area and urban land; however, they were still detected in the deep layers, and high-molecular-weight PAHs were dominant in most depths and sampling sites. The vertical distribution and migration of PAHs in soils were affected by molecular characteristics and component concentrations of PAHs, soil physical and chemical properties, and land use types. PMF source analysis indicated that coke sources, traffic sources, and coal combustion sources from human activities were the main sources of PAHs in this study region.

Study of Relative Humidity Vertical Distribution Characteristics before Precipitation by Microwave Radiometer Data over Southeast China

We investigated the relative humidity (RH) vertical distribution characteristics before precipitation using microwave radiometer measurements over southeast China in 2021. The superposed epoch method is used to analyze the profile and vertical statistical characteristics and evolution of RH during precipitation events. There is a shallow, high-humidity area on the ground, with a thickness of about 0.1–0.2 Km, from 12 to 8 h before precipitation. An obvious dry layer appears in the lower layer near the ground 8–0 h before precipitation, with a thickness of about 1 km and humidity of less than 80%, which continues until the appearance of precipitation. The water vapor content in the air begins to accumulate and the humidity increases before the occurrence of LRs, MRs, and HRs, classified by total rainfall. The SDPs, MDPs, and LDPs, which are classified by precipitation duration, showed more obvious and significant characteristics of humidity increase. The statistical analysis of the 44 precipitation cases shows that the relative humidity on the ground and in the air increases significantly before precipitation, and the vertical distribution of the relative humidity and the increase in the water vapor content in the air have a more direct and obvious impact on the precipitation duration. The deep and high-humidity area of 2–4 km is conducive to maintaining the precipitation process for a long time.

Dissolved Oxygen and Water Temperature Drive Vertical Spatiotemporal Variation of Phytoplankton Community: Evidence from the Largest Diversion Water Source Area.

In order to study the vertical distribution characteristics of phytoplankton in the Danjiangkou Reservoir, the water source of the Middle Route Project of the South-North Water Diversion, seven sampling sites were set up in the Reservoir for quarterly sampling from 2017 to 2019, and water environment surveys were conducted simultaneously. The results showed that 157 species (including varieties) were identified, belonging to 9 phyla and 88 genera. In terms of species richness, Chlorophyta had the largest number of species, accounting for 39.49% of the total species. The Bacillariophyta and Cyanobacteria accounted for 28.03% and 13.38% of the total species, respectively. From the whole Danjiangkou Reservoir, the total phytoplankton abundance varied from 0.09 × 102 to 20.01 × 106 cells/L. In the vertical distribution, phytoplankton were mainly observed in the surface-thermospheric layer (I-II layer) and the bottom layer, while the Shannon-Wiener index showed a trend of gradually decreasing from the I-V layer. The Surfer model analysis showed that there was no significant stratification in the Q site's water temperature (WT) and dissolved oxygen (DO) levels in the water diversion area during the dynamic water diversion process. A canonical correspondence analysis (CCA) showed that DO, WT, pH, electrical conductivity (Cond), chemical oxygen demand (CODMn), total phosphorus (TP), ammonia nitrogen (NH4+-N), and total nitrogen (TN) had significant effects on the vertical distribution of phytoplankton (p < 0.05). A partial Mantel analysis showed that the vertical distribution of the phytoplankton community was related to WT, and the phytoplankton community structure at the other sites, except for Heijizui (H) and Langhekou (L), was affected by DO. This study has positive significance for exploring the vertical distribution characteristics of a phytoplankton community in a deep-water dynamic water diversion reservoir.

Distribution characteristics of radionuclides (137Cs, 239+240Pu, 237Np, and 241Am) in vertical vegetation zone in Changbai Mountain, China

Changbai Mountain has vegetation distribution characteristics, which is an important location in northeast China to study the variation characteristics of radionuclides with vegetation distribution. Soils from three vegetation zones of mixed broadleaf and coniferous forest (MBCF), coniferous forest (CF), and alpine birch forest (ABF) in Changbai Mountain were collected to measure the artificial radionuclides of 239+240Pu, 237Np, and 241Am by SF-ICP-MS, as well as 137Cs by anti-Compton HPGe. The mean values of 240Pu/239Pu and 237Np/239Pu atomic ratios, 241Am/239+240Pu and 137Cs/239+240Pu activity ratios were 0.19 ± 0.02, 0.37 ± 0.23, 0.56 ± 0.31, 22 ± 17, respectively, indicating that the global fallout was the main source of 239+240Pu, 237Np, 137Cs and 241Am in these regions. 137Cs, 239+240Pu, 237Np, and 241Am activities in the samples are 1.1–218, 0.065–9.1, (0.018–2.9) × 10-3, and 0.039–2.0 Bq/kg, respectively. The activities of 137Cs, 239+240Pu, and 237Np in the surface soil have a similar distribution characteristic, i.e. CF > MBCF > ABF, and 241Am is CF > ABF > MBCF. The simulation results of the CDE model suggest that the migration of these radionuclides is dominant in Changbai Mountain forest soil. The inventories of 137Cs, 239+240Pu, 237Np, and 241Am in the soil cores are 1263–20843, 110–1425, 0.017–0.38, and 91–493 Bq/m2, respectively. The inventories distribution of these nuclides in the vegetation zone were as follows: 137Cs and 239+240Pu had similar distribution characteristics as ABF > CF > MBCF; 237Np as CF > MBCF > ABF; 241Am as ABF > MBCF > CF. These results showed that the content, accumulated inventory, and vertical distribution characteristics of these radionuclides were influenced by the vegetation zone distribution in the Changbai Mountain.

Risk Assessment of Heavy Metals in Soils from Four Different Industrial Plants in a Medium-Sized City in North China.

Laboratory experiments were carried out to analyze 39 soil samples collected from four industrial areas in Xuzhou City using inductively coupled plasma mass spectrometry and atomic fluorescence spectrometry. The descriptive statistics of heavy metals (HMs) in the soil profiles showed that the HM content at three depths was highly variable, and most coefficients of variation (CVs) showed moderate variability. The enrichment of Cd at all depths exceeded the risk screening value, and Cd pollution occurred in four plants. The enrichment of the other HMs at three depths was mainly concentrated in the pharmaceutical plant A and chemical plant C. It was found that the different HMs had different vertical distribution characteristics. For the different industrial plants, the raw materials and products not only made the spatial distribution characteristics of the HMs different, but also caused the HM types and contents to differ. The average single pollution indices of Cd in plant A, iron-steel plant B, and plant C indicated a slight pollution level. The other seven HMs in A, B, and C and all HMs in chemical plant D belonged to the safe category. The mean values of the Nemerow pollution index in the four industrial plants belonged to the warning category. The analysis showed that none of the HMs posed potential noncarcinogenic health risks, and only the carcinogenic health risks of Cr in plants A and C were unacceptable. The carcinogenic effect of Cr through the inhalation intake of resuspended soil particulates and that of Cd, Ni, and As via direct oral ingestion were the main exposure pathways.

Three-dimensional distribution characteristics of multiple pollutants in the soil at a steelworks mega-site based on multi-source information

Soil pollution at steelworks mega-sites has become a severe environmental issue worldwide. However, due to the complex production processes and hydrogeology, the soil pollution distribution at steelworks is still unclear. This study scientifically cognized the distribution characteristics of polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), and heavy metals (HMs) at a steelworks mega-site based on multi-source information. Specifically, firstly, 3D distribution and spatial autocorrelation of pollutants were obtained by interpolation model and local indicators of spatial associations (LISA), respectively. Secondly, the characteristics of horizontal distribution, vertical distribution, and spatial autocorrelations of pollutants were identified by combining multi-source information such as production processes, soil layers, and properties of pollutants. Horizontal distribution showed that soil pollution in steelworks mainly occurred in the front end of the steel process chain. Over 47% of PAHs and VOCs pollution area were distributed in coking plants and over 69% of HMs in stockyards. Vertical distribution indicated that HMs, PAHs, and VOCs were enriched in the fill, silt, and clay layers, respectively. Spatial autocorrelation of pollutants was positively correlated with their mobility. This study clarified the soil pollution characteristics at steelworks mega-sites, which can support the investigation and remediation of steelworks mega-sites.

Data for vertical distribution char acteristics of the super typhoon gust factor based on a 356-m high meteorological gradient tower

Data for vertical distribution char acteristics of the super typhoon gust factor based on a 356-m high meteorological gradient tower

Accumulation, Migration, and Transformation of Soil Phosphorus in Facility Agriculture and Its Influencing Factors

The aim of this study was to apply phosphorus fertilizer scientifically and reasonably and reduce the pollution risk to the facility agricultural environment. Taking the facility agriculture concentration area in Daxing District of Beijing as the research object, the phosphorus content in soil (0-100 cm) of the facility agriculture profile with different planting years was measured and analyzed to explore the characteristics of phosphorus accumulation, migration, and transformation. The results showed that the contents of total phosphorus and available phosphorus in the surface soil of facility agriculture varied widely, which was significantly higher than that in the surrounding grain field soil, which was mainly related to the amount of phosphorus applied by farmers in different planting years. With the increase in soil depth, the contents of total phosphorus and available phosphorus decreased gradually, showing surface aggregation ω (total phosphorus) ranging from 0.38 to 2.58 g·kg-1 and ω (available phosphorus) ranging from 1.60 to 256.00 mg·kg-1. With the increase in planting years, the contents of soil total phosphorus and available phosphorus first increased and then decreased, reached a peak in approximately 15 years, then gradually decreased, tended to be stable, and generally remained at a high level. Inorganic phosphorus was mainly concentrated in the surface soil of the facility agriculture, in which Ca-P accounted for the largest proportion of inorganic phosphorus, up to 98.38%; Ca10-P was the main form of Ca-P, up to 78.70% of Ca-P, and Ca2-P accounted for the smallest proportion, only 9.50% of Ca-P. The contents of different forms of inorganic phosphorus showed the vertical distribution characteristics of enrichment in the surface soil and a decrease downward. There were differences in the proportion of different forms of inorganic phosphorus to total phosphorus in different soil depths, in which the change in Ca-P was obvious, whereas the change in Fe-P and 0-P was not significant, indicating that the migration and transformation of Fe-P and O-P in the facility agricultural soil was poor, and the migration and transformation of inorganic phosphorus was mainly Ca-P. According to the correlation and path analysis, the direct path coefficient of Ca2-P to available phosphorus was the largest (0.787), which was not only the main source of soil available phosphorus but also the main form of inorganic phosphorus migration and transformation. Under the condition of protected cultivation, soil phosphorus showed a large accumulation trend, the availability of Ca10-P was low, and the accumulation was large. How to improve this portion of phosphorus sources is the key to the management of protected soil phosphorus.

Vertical Distribution Characteristics of Boundary Layer Volatile Organic Compounds in Autumn in the Mixed Industrial and Rural Areas over the Northern Suburb of Nanjing

Based on the sounding data of VOCs in the lower troposphere (0-1000 m) in the northern suburb of Nanjing in the autumn of 2020, the vertical profile distribution, diurnal variation, and photochemical reactivity of VOCs in this area were analyzed. The results showed that the volume fraction of VOCs decreased with the increase in height (72.1×10-9±28.1×10-9-56.4×10-9±24.8×10-9). Alkanes at all heights accounted for the largest proportion (68%-75%), followed by aromatics (10%-12%), halohydrocarbons (10%-11%), alkenes (3%-7%), and acetylene (2%). The diurnal variation of the boundary layer had a great influence on the VOCs profile. The lower boundary layer in the morning and evening caused the volume fraction of VOCs to accumulate near the ground and lower in the upper layer. The vertical distribution of VOCs was more uniform in the afternoon. In the morning, the volume fraction proportion of alkenes (alkanes) with strong (weak) photochemical reactivity decreased (increased) with the increase in height, indicating that the photochemical aging of VOCs in the upper layer was significant. In the afternoon, the vertical distribution of VOCs volume fraction and OFP in the lower troposphere were more uniform. Affected by the surrounding air masses with different sources, the volume fraction and component proportion of VOCs at each height were significantly different. The alkanes in rural air masses were vertically evenly distributed, and the proportion increased gradually with the height. The vertical negative gradient of VOCs volume fraction in the urban air mass was the largest, the volume fraction of VOCs near the ground was high, and it was rich in aromatics. The proportion of aromatics increased with the increase in VOCs volume fraction between 200-400 m height of industrial air mass. The near-surface VOCs volume fraction of the highway traffic air mass was high, and alkanes accounted for the largest proportion.

Spatial distribution characteristics and prediction of fluorine concentration in groundwater based on driving factors analysis.

Excess fluoride (F-) in groundwater can be hazardous to human health. A total of 360 ground water samples was collected from northern Anhui, China, to study the levels, distribution, and source of F-. And on this basis, predicting the spatial distribution of F- in a wider scale space. The range of F- was 0.1-5.8 mg/L, with a mean value of 1.2 mg/L, and 26.4 % of the samples exceeded the acceptable level of 1.5 mg/L. Moreover, the water-rock interaction (fluorite dissolution) and cation alternate adsorption were considered to be two main driving factors of high F- in groundwater. To further illustrate the spatial effects, the BME-RF model was established by combining the main environmental factors. The spatial distribution of F- was quantitatively predicted, and the response to environmental variables was analyzed. The R2 of BME-RF model reached 0.93, the prediction results showed that the region with 1.0-1.5 mg/L of F- accounts for 47.2 % of the total area. The predicted F- content of nearly 70 % of groundwater in this area has exceeded 1.0 mg/L, which was dominated by Na+ and HCO3- type. The spatial variability of F- in the study area was mainly affected by hydrogeological conditions, and the vertical distribution characteristics were related to the spatial variation of slope, distance from runoff, and hydrochemical types. The results of the study provide new insights into the F- concentration prediction in underground environment, especially in the borehole gap area.

Long-term characteristics of vertical distribution of precipitation in different seasons in Taiwan based on observational station data

&lt;p&gt;不同於過往區域降水研究僅在水平空間上討論地區性的降水分布，本研究利用各海拔高度的降水觀測資料，聚焦於臺灣各地區在不同時節和不同海拔高度的降水資訊。藉由這些分析，可瞭解除了地區降水的平均分布外，亦可知其在時間和垂直空間上的分布特徵以及相關的形成機制，並為後續研究提供參考。&lt;/p&gt; &lt;p&gt;分析結果顯示，梅雨季時的臺灣西北部，滯留鋒附近的劇烈中尺度對流系統向西移入陸地，會在平地至高山形成強降水。夏季時雖然颱風也帶來廣泛性的強降水，然而另一降水來源的熱對流系統卻偏好發展於較低海拔高度，使得兩者的貢獻加總後，夏季降水量隨海拔高度上升而漸增，但高山地區降水卻又減少。西南部整體降水情況與西北部類似，降水主要集中在梅雨季和夏季，不同之處在於西南部位於西南季風的迎風面，因此該地區雨季整體降水量比其他地區更多。此外，夏季時除了颱風本身可為西南部各海拔高度帶來強降水，颱風環流和西南季風形成的暖濕西南氣流也會在迎風面山坡造成災害性強降水，然而高山地區卻因為可降水含量不足，因此雨水相對減少，使得夏季降水量極值主要出現在海拔2000 m以下區域。&lt;/p&gt; &lt;p&gt;東半部的降水多集中在夏季至秋季，形成與西半部明顯不同的降水季節特徵。梅雨季時儘管滯留鋒也會為東北部各海拔高度帶來明顯降水，然而由於位處鋒面對流系統移入路徑的背風側，因此旺盛對流系統不易發展而較少強降水。夏季時由於東北部位於西南季風的背風側，因此熱對流系統也較不易發展，然而該地區位於侵臺颱風的前線，颱風可為各海拔高度帶來強降水，補充夏季時的雨量來源。秋季由於環境風場漸轉為東北季風，季風本身或與颱風形成的共伴效應會在蘭陽平原的迎風面山坡帶來可觀降水，然而高山由於可降水含量下降，使得整體降水量高值集中在海拔2000 m以下地區。東南部與東北部的情況類似，卻因為整體地勢高度較為低矮，地形抬升作用造成降水的效果較不理想，以及並非如東北部般位於東北季風的直接迎風面，因此整體降水量比起東北部較低些。&lt;/p&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;&lt;p&gt;Unlike previous researches mainly examining regional precipitation in horizontal space, this study focuses on vertical spatial distribution characteristics of regional precipitation during the rainy season through analyzing precipitation observation data at various altitudes in Taiwan, which provides useful messages for future studies in terms of temporal and vertical distributions of regional precipitation as well as related mechanisms.&lt;/p&gt; &lt;p&gt;During the Meiyu season in the northwest, the stationary front accompanying mesoscale convective systems moves westward into the land, leading to heavy precipitation at all altitudes. In summer, typhoons bring extensive precipitation to lowland and mountainous areas, while the convection system, another main source of precipitation in this season, tends to develop at lower altitudes. Hence, the overall summer rainfall increases with height but gradually decreases in the mountains. The rainy condition in the southwest is similar to that in the northwest, which also mainly occurs in the Meiyu season and summer. Aside from this similarity, the overall rainfall in the southwest during the rainy season reaches another level as compared to other regions since this area is located on the windward side of the summer monsoon. In addition to typhoons with considerable precipitation at all altitudes in the southwest, the typhoon-monsoon-induced southwesterly flow also causes disastrous precipitation on the windward slopes; however, insufficient precipitable water vapor at high altitudes reduces precipitation in the mountains. All these contribute to a typical summer rainfall pattern with extreme values mainly seen at lower altitudes below 2000 meters.&lt;/p&gt; &lt;p&gt;Most of the water precipitates in the eastern coast in summer and fall, showing a huge dissimilarity from the western coast. During the Meiyu season, the northeast is on the leeward side of the stationary front, which does not benefit frontal convection systems to further develop and therefore less frequent heavy precipitation is the result. Although the northeast is also on the leeward side of the summer monsoon, this region receives plentiful rainfall from most of the invading typhoons due to its location and therefore the tropical cyclone becomes a main water source at all altitudes. In fall, since the environmental wind field gradually changes to the northeasterly, the northeasterly alone or the accompanied effect with the typhoon brings considerable precipitation on the windward slopes of the Yilan Plain, while most of the rainfall restricts at lower altitudes below 2000 meters. The precipitation pattern in the southeast somewhat resembles that in the northeast, yet the uplift effect caused by the topography does not effectively produce much precipitation due to the relatively low terrain in the southeast. In addition, the location of this region is not on the direct windward side of the northeasterly, which further creates a relatively unfavorable condition for rain to generate.&lt;/p&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;

Uncovering Network Heterogeneity of China’s Three Major Urban Agglomerations from Hybrid Space Perspective-Based on TikTok Check-In Records

Urban agglomeration is an essential spatial support for the urbanization strategies of emerging economies, including China, especially in the era of mediatization. From a hybrid space perspective, this paper invites TikTok cross-city check-in records to empirically investigate the vertical and flattened distribution characteristics of check-in networks of China’s three major urban agglomerations by the hierarchical property, community scale, and node centrality. The result shows that (1) average check-in flow in the Yangtze River Delta, Beijing-Tianjin-Hebei, and Pearl River Delta network decreases in descending order, forming a Z-shaped, single-point radial, and N-shaped structure, respectively. (2) All three urban agglomerations exhibit a nexus community structure with the regional high-flow cities as the core and the surrounding cities as the coordinator. (3) Geographically proximate or recreation-resource cities have a high degree of hybrid spatial accessibility, highlighting their nexus role. Finally, the article further discusses the flattened evolutionary structure of the check-in network and proposes policy recommendations for optimizing check-in networks at both the digital and geospatial levels. The study gains from the lack of network relationship perspective in the study of location-based social media and provides a novel research method and theoretical support for urban agglomeration integration in the context of urban mediatization.

Vertical Magnetic Field Distribution Characteristics of Triple-Peak Halbach Array PMG and Its Engineering Application in HTS Maglev Train

The maglev train has a broad application prospect in the field of high-speed transportation, which is based on the high-temperature superconductor permanent magnet guideway (HTS-PMG) maglev system. The optimized design of the permanent magnet guideway (PMG) configuration is of great significance to improve the overall performance of the system and reduce the cost. In this article, a triple-peak Halbach array PMG is proposed, which is suitable for the HTS-PMG maglev system based on square single-seed melt-texture YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7-</sub> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">_x</i> block with a width of 40 mm. Through theoretical calculations, the influence of structural parameters of triple-peak Halbach array PMG on the vertical magnetic field distribution characteristics is revealed, that is, increasing the proportion of horizontally magnetized permanent magnet (vertically magnetized permanent magnet) is conducive to enhancing the vertical magnetic field in the regions close to (far away from) PMG. Furthermore, combined with the engineering application of HTS-PMG maglev train, an optimized triple-peak Halbach array PMG sample is fabricated. And the reliability of the theoretical model of triple-peak Halbach array PMG is verified by simulation and experimental measurements. Based on the optimized PMG, a full-scale HTS-PMG maglev train test line with a length of 22 m and a standard gauge of 1.435 m (in China) is built up, and the manned test is successfully carried out, which shows the feasibility of the triple-peak Halbach array PMG in large-scale engineering application of the HTS-PMG maglev train.

Understanding of groundwater evolution through chemical and age dating information in the Yongding River alluvial fan in Beijing

Groundwater plays important roles in human community development and the urbanization process as the results of global environmental change and rapid population growth. A clear understanding of the vertical and horizontal spatial distribution characteristics of groundwater and sediment is the premise of efficient groundwater resource management and utilization in alluvial plains. To explore the evolution process of groundwater and the distribution of sediment in the Yongding River (YDR) alluvial fan, a typical profile from Mentougou to Fengheying was chosen to conduct an extensive hydrogeological investigation with multiple hydrochemical, isotopic, and age dating analyses, which represents one of the most typical hydrogeological units in the YDR alluvial fan. The analysis results show that (i) along the profile, the water’s chemistry type gradually changes from HCO3-Ca·Mg to HCO3-Na. The contents of coarse grain gradually decrease while fine particles regularly increase. Also, a similar evolution trend is found in the vertical direction. (ii) The annual renewable rate of groundwater is &amp;gt; 10% in the upper fan, 2%–8% nearby Daxing, and &amp;lt; 2% in Fengheying. (iii) In the proximal fan area, the average flow velocity of the single and double layer is about 65 m yr−1 and of approximately 18.9 m yr−1. From the mid fan to distal fan, the value of velocity and hydraulic conductivity decreases from 12.4 m yr−1 to 3.75 m yr−1 and from 8.54 m yr−1 to 0.64 m yr−1, respectively. (iv) The 14C analysis results indicate that the age of shallow and deep groundwater ranges from 5a to 60a and from 4000a to 12000a, respectively. The groundwater age increases with depth in the vertical direction and increases from northwest to southeast along in the alluvial fan in the horizontal direction. Understanding the evolution process of sediment and hydrochemistry in the YDR alluvial fan provides a valuable reference for groundwater resource development, utilization, and pollution prevention in the alluvial fan.

The Vertical Distribution of VOCs and Their Impact on the Environment: A Review

Volatile organic compounds (VOCs) play an important role in atmospheric chemistry. Primary VOCs take part in chemical and photochemical reactions, contributing to ozone (O3) and secondary organic aerosol (SOA) formation, which may cause air pollution problems. High VOC concentrations might lead to dizziness, nausea, headaches, genotoxicity, reproductive weakness, and other diseases harmful to human health. Several studies have been performed to analyze the components, variations, or sources of VOCs at the ground level. In contrast, studies of the vertical distribution characteristics of VOCs are scarce, and the VOC potential for O3 formation in the boundary layer is not yet well understood. To better understand the VOC vertical variation regularities and related reasons in temporal and spatial dimensions, thus to deepen the understanding of their effects on O3 and SOA formation in the vertical direction and to identify the existing gaps in VOC vertical distributions, this study reviewed VOC sampling techniques, VOC vertical distribution characteristics, VOC diffusion models, and effects caused by VOCs. This work can be a valuable reference for decision making regarding environmental and health problems.

Research on Lidar Network Observation of Aerosol and Pollution in Beijing 2022 Winter Olympics

During the Beijing Winter Olympics, three sets of aerosol lidar in different regions were used to conduct continuous observations to study the optical properties and vertical distribution characteristics of atmospheric aerosol. Based on the lidar data and sun photometer data, the accurate lidar ratio was determined to improve the inversion accuracy of the aerosol backscattering coefficient. The influence of meteorological conditions such as temperature, relative humidity, wind speed, and wind direction on the optical properties of aerosol were analyzed, and the type of aerosol was classified by the depolarization ratio of aerosol particles and CALIPSO data. Furthermore, the backward trajectory analysis, potential source contribution function (PSCF), and concentration weighted trajectories (CWT) were employed to explore the sources and transport mechanisms of pollutants. The analysis found that the extinction coefficient under the atmospheric boundary layer during the Winter Olympics had a spatial distribution pattern of high value in the southeast and low value in the northwest. The occurrence of aerosol pollution events is not only caused by local emissions, but is also related to regional transmission.

3D-VDNet: Exploiting the vertical distribution characteristics of point clouds for 3D object detection and augmentation

• Vertical distribution characteristics (VDCs) of point clouds are robust to point-sparsity and provide semantic information. • Decorating the pillars with VDCs and semantic label is conducive to robust and discriminative feature extraction. • The adaptive object augmentation (AOA) paradigm overcomes the conflict between augmented objects and corresponding scenes. • 3D-VDNet significantly outperforms the baseline in all classes (Car, Pedestrian, and Cyclist). • The AOA paradigm with a stable performance across detector types (voxel- or point-based). Accurate 3D object detection is limited by the sparsity of LiDAR-based point clouds. The vertical distribution characteristics (VDCs) of point clouds in pillars are robust to point-sparsity and provide informative semantic information on objects. Based on this, we propose a novel 3D object detection framework where the VDCs of point clouds are exploited to optimize feature extraction and object augmentation. More specifically, a Spatial Feature Aggregation module is proposed to perform robust feature extraction by decorating pillars with the VDCs. To spatially enhance semantic embeddings, we employ VDCs to construct a voxelized semantic map, acting as an additional input stream. Moreover, we develop an Adaptive Object Augmentation (AOA) paradigm, which adopts the VDC searching of suitable ground regions to “paste” virtual objects, thus avoiding conflicts with new scenes. Extensive experiments on the KITTI dataset demonstrate that our framework can significantly outperform the baseline, achieving 3.74%/1.59% moderate AP improvements on the Car 3D/BEV benchmarks with 38 FPS inference speed. Furthermore, we prove the stable performance of our AOA module across different detectors.

Vertical variation of atmospheric particulate matter under different pollution levels in the suburbs of Tianjin based on unmanned aerial vehicle

ABSTRACT An unmanned aerial vehicle equipped with an isokinetic sampling device and a portable aerosol particle size spectrometer was used to detect atmospheric particles at different altitudes in the suburbs of Tianjin. In January 2017, four flight tests under different air conditions were conducted, and the Severe polluted and Excellent levels were classified according to the air quality index of the State-controlled site. Changes in mass concentration with altitude, and the vertical distribution of mass concentration and number concentration spectrum were analyzed. Results showed that under the Severe polluted condition, the concentration of particulate matter (PM) decreased significantly within 200 m, and became stable above 400 m. Two peaks at 260 m and 400 m were observed – they were attributed to local emissions and transportation of nearby areas. When the mass concentration significantly increased, the greatest contributor was particles with a size of 15–30 μm. As altitude increased, PM with the size of less than 1 μm accounted for the largest proportion. Regarding number concentration, the main particle size was less than 0.35 μm. Under the Excellent condition, particles less than 0.35 μm in size were the most important components in mass and number concentrations. Correlation analysis of meteorological factors and backward trajectory indicated that pollution was caused by particle concentration transport in several provinces and the particle accumulation due to temperature inversion.Implications: Study on the vertical structure of air pollutants was very important for understanding the occurrence and development of regional heavy pollution. Unmanned aerial vehicles (UAVs) was an efficient method for its easy operation, good stability, high flexibility and safety, and was introduced to observe the vertical distribution characteristics of particle concentration under different weather conditions. This study provided the number concentration spectra and the mass concentration spectra at different height, and would give some support for the precise control of air pollution.

A New Algorithm of Atmospheric Boundary Layer Height Determined from Polarization Lidar

Accurately determining the atmospheric boundary layer height (ABLH) is needed when one is addressing the air quality-related issues in highly urbanized areas, as well as when one is investigating issues that are related to the emission and transport of dust aerosols over the source region. In this study, we propose a new ABLH retrieval method, which is named ADEILP (ABLH that is determined by polarization lidar); it is based on the short-term polarized lidar observation that took place during the intensive field campaign in July 2021 in Tazhong, the hinterland of Taklimakan Desert. Furthermore, we conducted comparisons between the ABLH that was identified using a radiosonde (ABLHsonde), the ABLH that was identified by ERA5 (ABLHERA5) and the ABHL that was identified by ADELIP (ABLHADELIP), and we discussed the implications of the dust events. The ADELIP method boasts remarkable advancements in two parts: (1) the lidar volume linear depolarization ratio (VLDR) that represented the aerosol type was adopted, which is very effective in distinguishing between the different types of boundary layers (e.g., mixing layer and residual layer); (2) the idea of breaking up the entire layer into sub-layers was applied on the basis of the continues wavelet transform (CWT) method, which is favorable when one is considering the effect of fine stratification in an aerosol layer. By combining the appropriate height limitations, these factors ensured that there was good robustness of the ADELIP method, thereby enabling it to deal with complex boundary layer structures. The comparisons revealed that ABLHADELIP shows good consistency with ABLHsonde and ABLHERA5 for non-dust events. Nevertheless, the ADELIP method overestimated the stable boundary layer and underestimated the heights of the mixing layer. The dust events seem to be a possible reason for the great difference between ABLHERA5 and ABLHsonde. Thus, it is worth suggesting that the influence that is caused by the differences of the vertical profile in the ERA5 product should be carefully considered when the issues on dust events are involved. Overall, these findings support the climatological analysis of the atmosphere boundary layer and the vertical distribution characteristics of aerosols over typical climatic zones.

Iron-bound organic carbon dynamics in peatland profiles: The preservation equivalence of deep and surface soil

More than half of the carbon pools in peatlands are stored in the soil layers below 30 cm, yet little is known about the carbon stabilizing factors at these depths. Although iron oxide minerals are considered to be important for stabilizing organic carbon (OC), their role in the preservation of OC in peatlands, especially in the deep layers, is poorly understood. Here, we collected 1 m soil profiles from six peatlands in Central and West China to quantitatively study the vertical distribution characteristics of iron-bound OC (Fe-bound OC), and the influencing physicochemical properties of the soil. The results showed that the content of reactive iron (FeR) was enriched in the top layer and decreased gradually with depth. While Fe-bound OC was positively correlated with FeR, its concentration did not decrease with depth in the peat profile. There were no obvious trends in the distributions of FeR and Fe-bound OC with water level fluctuations in the peat profile. In addition, the proportion of Fe-bound OC to soil organic carbon in the deep peat (31 to 100 cm) was equivalent to that in the surface peat (0 to 30 cm), indicating that iron oxide mineral provides comparable protection of OC in both layers. According to upper estimates of global peatland carbon storage (612 Pg), it could be predicted that 23.81 ± 11.75 Pg of OC is protected by association with FeR. These results indicated that iron oxide minerals are the effective "rusty sink" of OC sequestration in peatland, and a key factor for its long-term preservation. The results from this study make a valuable contribution to the carbon dynamics knowledgebase for peatlands, and provide a basis for improved predictive simulations.