The risk characteristics of heavy metals in urban soil of typical developed cities in China.

With the rapid development of China's industrial economy, heavy metals continue to accumulate in the environment, which has created serious threats for the ecological environment and human health. This study collected 50 surface soil samples in Nanjing, a typical developed city in China, and the contents of Al, Ca, Fe, Mg, Mn, Ni, Ti, Cd, Cr, Cu, Pb, and Zn in the samples were determined. Combined with the ecological risk index and the health risk assessment model, the risk of soil heavy metals in Nanjing was comprehensively evaluated. The results show that the variation coefficients of Pb and Cu are distinctly large, and these elements are all slightly polluting. Children are at a high risk of exposure in various ways, among which Pb and Cu elements have a high risk of causing non-carcinogenic issues. The results of the correlation analysis showed that the content changes of Pb, Zn, and Cu had extremely significant correlations, indicating that they may have the same source. The results of the principal component analysis showed that industrial sources in Nanjing contributed the most heavy metals, reaching 34.4%. The second largest source was from parent material and fertilizer, which contributed 32.3% and 19.6%, respectively. The sources with the lowest contributions were from weathering and deposition, which reached 13.7%. The results of this study will provide guidance and reference for risk-source analysis, early warning, and management of soil heavy metals in developed cities.

Land Cover Change in the Central Region of the Lower Yangtze River Based on Landsat Imagery and the Google Earth Engine: A Case Study in Nanjing, China.

Urbanization in China is progressing rapidly and continuously, especially in the newly developed metropolitan areas. The Google Earth Engine (GEE) is a powerful tool that can be used to efficiently investigate these changes using a large repository of available optical imagery. This work examined land-cover changes in the central region of the lower Yangtze River and exemplifies the application of GEE using the random forest classification algorithm on Landsat dense stacks spanning the 30 years from 1987 to 2017. Based on the obtained time-series land-cover classification results, the spatiotemporal land-use/cover changes were analyzed, as well as the main factors driving the changes in different land-cover categories. The results show that: (1) The obtained land datasets were reliable and highly accurate, with an overall accuracy ranging from 88% to 92%. (2) Over the past 30 years, built-up areas have continued to expand, increasing from 537.9 km2 to 1500.5 km2, and the total area occupied by built-up regions has expanded by 178.9% to occupy an additional 962.7 km2. The surface water area first decreased, then increased, and generally showed an increasing trend, expanding by 17.9%, with an area increase of approximately 131 km2. Barren areas accounted for 6.6% of the total area in the period 2015-2017, which was an increase of 94.8% relative to the period 1987-1989. The expansion of the built-up area was accompanied by an overall 25.6% (1305.7 km2) reduction in vegetation. (3) The complexity of the key factors driving the changes in the regional surface water extent was made apparent, mainly including the changes in runoff of the Yangtze River and the construction of various water conservancy projects. The effects of increasing the urban population and expanding industrial development were the main factors driving the expansion of urban built-up areas and the significant reduction in vegetation. The advantages and limitations arising from land-cover mapping by using the Google Earth Engine are also discussed.

The Hiroshima memory complex.

The atomic bomb attack on Hiroshima on August 6, 1945 is one of the most powerful global memories. While the literature on global memories has greatly expanded in recent decades, Hiroshima remains surprisingly understudied. In addressing this lacuna, this paper develops a new theoretical prism for the study of global memories. It argues that the Hiroshima memory cannot be understood in isolation, but rather as the hub in a broader memory complex. This complex is the result of symbolic dialogues that connect Hiroshima with such different events, situations, and memories as Nanjing, Pearl Harbor, the Cold War, and so on. The paper demonstrates how these dialogues have been forged, often in the context of substantial controversy. While distinctly sociological in orientation, the paper takes its main theoretical inspiration from cultural, literary, and history scholars such as Jan and Aleida Assmann, Sebastian Conrad, Astrid Erll, Ann Rigney, Michael Rothberg, Aby Warburg and Mikhael Bakhtin.

[Review on diagnostic criteria of hepatic sinusoidal obstruction syndrome].

Hepatic sinusoidal obstruction syndrome (HSOS) is a kind of hepatic vascular disease which is characterized by damage to hepatic sinusoidal endothelial cells, centrilobular hepatic vein and/or interlobular vein, resulting in stenosis or lumen occlusion, hepatic injury and acute sinusoidal portal hypertension. Generally, most patients with HSOS have mild manifestations, but in severely ill patients, the disease can lead to multiple organ dysfunction/failure, and the mortality rate can be as high as 70%-80%. Therefore, it is important to identify and treat HSOS as soon as possible. This paper introduces the current clinical diagnostic criteria of HSOS, including the Modified Seattle and Baltimore Criteria along with "Nanjing Criteria", and reviews their characteristics, scope of application and limitations.

Expert consensus on the clinical management of pyrrolizidine alkaloid-induced hepatic sinusoidal obstruction syndrome.

Hepatic sinusoidal obstruction syndrome (HSOS) is a hepatic vascular disease presenting with abdominal distension, pain in the hepatic region, ascites, jaundice, and hepatomegaly. In China, this disease is often associated with the oral intake of plants that contain pyrrolidine alkaloids. The existing guidelines are limited to HSOS associated with hematopoietic stem cell transplantation in Western countries. The Hepatobiliary Diseases Committee of the Chinese Society of Gastroenterology convened an expert consensus conference on the diagnosis and treatment of PA-HSOS to evaluate current research in China and abroad. The "Nanjing criteria" developed by the committee to diagnose PA-HSOS include a confirmed history of PA-containing plant use and (i) abdominal distention and/or pain in the hepatic region, hepatomegaly, and ascites; (ii) elevation of serum total bilirubin or abnormal laboratory liver tests; (iii) evidence on enhanced computed tomography or magnetic resonance imaging; or (iv) pathological evidence that rules out other known causes of liver injury. Supportive symptomatic treatment, anticoagulant therapy, and placement of a transjugular intrahepatic portosystemic shunt for patients who do not respond to medical treatment are effective for the treatment of PA-HSOS. The benefits of glucocorticoids and prostaglandin E1 in PA-HSOS are not clear.

Urinary levels, composition profile and cumulative risk of bisphenols in preschool-aged children from Nanjing suburb, China.

Due to the extensive use in consumer products, the bisphenols (BPs) pollution in the environments has aggravated and people are frequently exposed to BPs. In this research, four BPs, i.e., bisphenol A (BPA), bisphenol F (BPF), bisphenol S (BPS) and bisphenol AF (BPAF), were determined in urine samples collected from Gaochun District preschool-age children and the concentrations, distribution profiles, potential sources and cumulative risk assessment of the target compounds were studied. Total concentrations of 4 BPs ranged from 2 to 3113.1 ng/L, with the average concentration of 648.6 ng/L. BPA was the predominant congener (accounting for 94%), followed by BPS. Correlation analysis indicated a negative relationship between BPA and BPAF (R = -0.273, p < 0.05). The estimated daily intakes suggested that young females were more sensitive to BPs. Moreover, the cumulative risk for hazard quotient (HQ) of BPA has been evaluated and the results showed that no high risk had occurred. It provided basic information on the occurrence and human exposure to urinary BPs of preschool aged children from Gaochun District.

Investigation on the carbon sequestration capacity of vegetation along a heavy traffic load expressway.

Carbon sequestration by vegetation plays an important role in the global carbon cycle. More emphasis on the carbon sequestration of roadside vegetation will help to reduce the total carbon emissions from the transportation sector. In the current study, the Shanghai-Nanjing G42 expressway in east China was selected to investigate and calculate the carbon sequestration of roadside vegetation including trees, shrubs and herbs. Findings of the current study revealed that the total carbon sequestration of all the vegetation was about 97,000 tons per year. Results also indicated that trees have a higher carbon sequestration capacity (γ) in unit land area compared to shrubs and herbs. The γ value of most of the shrubs was lower than that of tree; however, species such as Nerium indicum, Jasminum mesnyi and Forsythia suspense have better carbon sequestration capacity than some other tree species. The γ value of herbs was too low, compared with trees and shrubs. The findings of the current study will be of great benefit to make the vegetation planting strategy for express highways in the areas with similar geographic characteristics and climate.

[Combination of serum PSA assay, multi-parametric MRI and targeted prostate biopsy for prostate cancer screening in Nanjing].

OBJECTIVE: To investigate the exact prevalence of PCa among males in Nanjing and search for a mode of PCa screening suitable for the specific conditions. METHODS: From January to December 2018, we collected serum samples and clinical information from 6 903 men aged ≥50 years taking physical examination in 16 community health service centers in Nanjing. We proposed multi-parametric MRI (mpMRI) for those with serum PSA ≥4 µg/L, transperineal systematic biopsy and MRI/ultrasound fusion targeted prostate biopsy for those who scored ≥3 points on the Prostate Imaging-Reporting and Data System Version 2 (PI-RADS v2), transperineal systematic biopsy only for those with a PI-RADS v2 score of <3 and serum PSA ≥10 µg/L, and follow-up examinations every 6 months for those with a PI-RADS v2 score of <3 and serum PSA <4 µg/L. RESULTS: Among the 6 903 male subjects, 835 (12.1%) were found with serum PSA≥4 µg/L; 229 (77.4%) of the 296 men that received mpMRI scored ≥3 points on PI-RADS v2; and 79 (53.4%) of the 148 males that underwent prostate biopsy were diagnosed with PCa, with a total detection rate of 1.14% in all the subjects. Of the 77 patients with complete pathological data, 73 (94.8%) were found with clinically significant PCa, 30 (39.0%) with localized, 41 (53.2%) with locally advanced and 6 (7.8%) with metastatic malignancy, 6 (7.8%) in stage Ⅰ, 21 (27.3%) in stage Ⅱ, 34 (44.2%) in stage Ⅲ and 16 (20.8%) in stage Ⅳ. There were 47 (66.2%) high-risk, 18 (25.4%) moderate-risk and 6 (8.5%) low-risk cases among those with localized or locally advanced PCa. CONCLUSIONS: The prevalence of PCa in Nanjing deserves considerable attention, and PCa screening is highly necessary in the high-risk population, for which the combination of serum PSA assay, mpMRI and targeted prostate biopsy may be an ideal method.

Change of the structure and the digestibility of myofibrillar proteins in Nanjing dry-cured duck during processing.

BACKGROUND: To investigate the change of bioavailability and structure of myofibrillar proteins during Nanjing dry-cured duck processing, carbonyl content, sulfhydryl (SH) group, disulfide (SS) group, sodium dodecyl sulfate polyacrylamide gel electrophoresis, surface hydrophobicity, secondary structures and in vitro digestibility were determined. RESULTS: During processing, carbonyl content and surface hydrophobicity increased; SH turned into SS group; α-helix turned into ß-sheet and random coil fractions. Protein degradation occurred during dry-curing and drying-ripening stages. The in vitro digestibility of pepsin and pancreatic proteases increased during the salt curing stage and decreased during the drying-ripening stage. CONCLUSION: The increase of digestibility could be attributed to the mild oxidation, degradation and unfolding of proteins while the decrease of digestibility was related to the intensive oxidation and aggregation of proteins. Protein degradation was not a main factor of digestibility during the drying-ripening stage. Results demonstrated that the bioavailability loss of myofibrillar proteins in Nanjing dry-cured duck occurred during the stage of drying-ripening instead of curing. © 2017 Society of Chemical Industry.

Spatiotemporal distribution and dynamic modeling of atmospheric gaseous polycyclic aromatic hydrocarbons in a rapidly urbanizing city: Nanjing, China.

Multiple studies have evaluated the concentration and lung cancer risk of polycyclic aromatic hydrocarbons (PAHs). However, the monitoring and dynamic modeling of PAHs with a high resolution were relatively insufficient. We investigated the spatiotemporal distribution of gaseous PAH concentrations using passive air samplers with high sampling density in an industrial city of Nanjing, China (January and October 2015) and found that the gaseous PAH concentrations in western Nanjing were higher than those in eastern Nanjing, mainly because of emission source distribution and wind action. There were notable seasonal changes in PAH concentrations: winter > autumn > spring > summer. We developed an atmospheric PAH dynamic model with a high resolution of 1 km2 based on the advection-diffusion equation and coupled with an emissions inventory and atmospheric transportation processes. Acenaphthene was selected as a proxy for gaseous PAHs. The modeled acenaphthene concentrations were similar to the concentrations measured. Moreover, we used the model to identify the impact of meteorological factors on gaseous PAHs via scenario analysis and found that a narrow-range temperature change and even heavy rainfall may not significantly affect atmospheric gaseous PAH concentrations, whereas the wind played an important part in transferring PAHs and changing their geographic distribution.

Variation of River Islands around a Large City along the Yangtze River from Satellite Remote Sensing Images.

River islands are sandbars formed by scouring and silting. Their evolution is affected by several factors, among which are runoff and sediment discharge. The spatial-temporal evolution of seven river islands in the Nanjing Section of the Yangtze River of China was examined using TM (Thematic Mapper) and ETM (Enhanced Thematic Mapper)+ images from 1985 to 2015 at five year intervals. The following approaches were applied in this study: the threshold value method, binarization model, image registration, image cropping, convolution and cluster analysis. Annual runoff and sediment discharge data as measured at the Datong hydrological station upstream of Nanjing section were also used to determine the roles and impacts of various factors. The results indicated that: (1) TM/ETM+ images met the criteria of information extraction of river islands; (2) generally, the total area of these islands in this section and their changing rate decreased over time; (3) sediment and river discharge were the most significant factors in island evolution. They directly affect river islands through silting or erosion. Additionally, anthropocentric influences could play increasingly important roles.

A Case Study Investigating the Relational Well-Being of International Students at Hohai University Nanjing, Jiangsu Province of China.

This study acknowledges the growing importance of international student mobility and examines the relational well-being of international students at Hohai University in Nanjing, China. Understanding the complexities of interactions among international students is essential for their well-being and the university's overall success, since this tendency continues to increase. By examining the distinct possibilities and problems faced by international students at Hohai University and considering elements including cultural distinctiveness, the campus environment, interpersonal dynamics, and support networks, the study fills a research void. For this purpose, 150 international students at Hohai University participated in semi-structured interviews and 10 participants participated in unstructured interviews as part of the mixed-methods approach to obtain in-depth information. Hence, the descriptive data were analyzed using SPSS and qualitative analyses were performed using NVIVO. According to preliminary findings derived from quantitative data, important results emphasize the significant impact of homesickness (0.143, T value: 5.931) and the positive correlation of relational well-being (0.146), highlighting their significance. The effect of the language barrier is also significant (0.125, T value: 4.378), whereas loneliness has little bearing (0.011, T value: 0.847). Additionally, the highest concern of the international students (M = 8.35; SD = 1.43) was making connections with local students. Additionally, (M = 8.21; SD = 1.15) international students favored Hohai University, which provided a welcoming atmosphere for intercultural dialogue. The Foreign Student Office, social events, cultural exchange programs, counseling services, and peer support networks are just a few examples of the support structures and networks crucial to international students' general well-being. At the same time, the cultural hurdles, including the language barrier and loneliness, seemed to be the challenge. The study concludes by shedding light on the relational well-being of international students at Hohai University and highlighting the importance of community-building and supporting actions. The results provide insightful information that will help the institution better respond to the particular difficulties that international students encounter, creating a more welcoming and stimulating atmosphere. This study establishes the foundation for further research in comparable contexts and advances our understanding of relational well-being in the context of experiences for overseas students.

[Transport and Potential Sources Regions of Double High Pollution in Nanjing by Different Synoptic Situations].

Based on the hourly concentration data of fine particulate matter （PM2.5） and ozone （O3） in Nanjing from 2015 to 2019， the synoptic situation that occurred in Nanjing， in which high PM2.5 and high O3 coexisted （hereinafter referred to as double high pollution （DHP））， was typed using T-mode principal component analysis. Additionally， the backward trajectory clustering analysis method， potential source contribution method （PSCF）， and concentration weight trajectory analysis method （CWT） were used to study the transport paths and potential source region distribution of the DHP of Nanjing by different synoptic situations. The synoptic situations favorable to the DHP in Nanjing were the control of weak low-pressure type （Type1） and high-pressure center （Type2）. Synoptic situations could have had an effect on the directional origin of the backward trajectory. In Type1， the Nanjing area was affected by two low pressures in the northeast and southwest， and the clustering trajectories of the Nanjing air mass mainly came from the eastern and western directions. The average concentrations of PM2.5 and O3 in the trajectory were 83.48 µg·m-3 and 106.85 µg·m-3， respectively. In Type 2， Nanjing and its surroundings were at the edge of the high-pressure center， and the air mass cluster trajectories mainly came from the north and east. The average concentrations of PM2.5 and O3 in the trajectory were 94.47 µg·m-3 and 92.32 µg·m-3， respectively. Most of the two types of backward trajectories belonged to short and medium-distance regional transportation， indicating that the pollution of neighboring provinces was one of the main factors affecting the DHP in Nanjing. PSCF and CWT analysis showed that the distribution of the most important potential sources of PM2.5 and O3 in Type1 and Type2 were not completely consistent， which indicates that the two pollutants did not come from the same area in the DHP.

How Do Tourists' Value Perceptions of Food Experiences Influence Their Perceived Destination Image and Revisit Intention? A Moderated Mediation Model.

The food experience is an important part of the tourism experience. Although it is crucial to comprehend the significance of tourists' perception of food experiences, there is a scarcity of research investigating the impact of tasting local food on tourists' perceptions and behaviors. This study employs structural equation modeling to empirically examine the relationship between tourists' value perceptions of food experiences, their perceived destination image, and their revisit intention. In addition, the moderating effects of tourists' genders on the aforementioned relationships are also explored. A renowned restaurant brand, Nanjing Impressions, which specializes in offering the unique cuisine of the city of Nanjing, China, is chosen as the research case. A grand total of 500 questionnaires were distributed, and, out of these, 458 questionnaires were deemed legitimate and kept for further analysis. The results indicate that the functional, social, emotional, cultural, and health values of local food experienced by tourists have significant positive impacts on their perceived destination image and revisit intention. Moreover, perceived destination image partially mediates the relationships between tourists' value perceptions of food experiences and their revisit intention. Gender is found to partially moderate the relationships between the proposed constructs. The current study offers noteworthy theoretical contributions and provides valuable practical suggestions for tourism destination managers.

Exploring Dynamic Changes in HIV-1 Molecular Transmission Networks and Key Influencing Factors: Cross-Sectional Study.

BACKGROUND: The HIV-1 molecular network is an innovative tool, using gene sequences to understand transmission attributes and complementing social and sexual network studies. While previous research focused on static network characteristics, recent studies' emphasis on dynamic features enhances our understanding of real-time changes, offering insights for targeted interventions and efficient allocation of public health resources. OBJECTIVE: This study aims to identify the dynamic changes occurring in HIV-1 molecular transmission networks and analyze the primary influencing factors driving the dynamics of HIV-1 molecular networks. METHODS: We analyzed and compared the dynamic changes in the molecular network over a specific time period between the baseline and observed end point. The primary factors influencing the dynamic changes in the HIV-1 molecular network were identified through univariate analysis and multivariate analysis. RESULTS: A total of 955 HIV-1 polymerase fragments were successfully amplified from 1013 specimens; CRF01_AE and CRF07_BC were the predominant subtypes, accounting for 40.8% (n=390) and 33.6% (n=321) of the specimens, respectively. Through the analysis and comparison of the basic and terminal molecular networks, it was discovered that 144 sequences constituted static molecular networks, and 487 sequences contributed to the formation of dynamic molecular networks. The findings of the multivariate analysis indicated that the factors occupation as a student, floating population, Han ethnicity, engagement in occasional or multiple sexual partnerships, participation in anal sex, and being single were independent risk factors for the dynamic changes observed in the HIV-1 molecular network, and the odds ratio (OR; 95% CIs) values were 2.63 (1.54-4.47), 1.83 (1.17-2.84), 2.91 (1.09-7.79), 1.75 (1.06-2.90), 4.12 (2.48-6.87), 5.58 (2.43-12.80), and 2.10 (1.25-3.54), respectively. Heterosexuality and homosexuality seem to exhibit protective effects when compared to bisexuality, with OR values of 0.12 (95% CI 0.05-0.32) and 0.26 (95% CI 0.11-0.64), respectively. Additionally, the National Eight-Item score and sex education experience were also identified as protective factors against dynamic changes in the HIV-1 molecular network, with OR values of 0.12 (95% CI 0.05-0.32) and 0.26 (95% CI 0.11-0.64), respectively. CONCLUSIONS: The HIV-1 molecular network analysis showed 144 sequences in static networks and 487 in dynamic networks. Multivariate analysis revealed that occupation as a student, floating population, Han ethnicity, and risky sexual behavior were independent risk factors for dynamic changes, while heterosexuality and homosexuality were protective compared to bisexuality. A higher National Eight-Item score and sex education experience were also protective factors. The identification of HIV dynamic molecular networks has provided valuable insights into the characteristics of individuals undergoing dynamic alterations. These findings contribute to a better understanding of HIV-1 transmission dynamics and could inform targeted prevention strategies.

Hepatitis E virus genotype 4, Nanjing, China, 2001-2011.

During 2001-2011, hepatitis E virus (HEV) was found in the blood of patients in Nanjing, China. All HEV-positive patients had virus genotype 4; subgenotype 4a was predominant. The effective population of HEV in Nanjing increased in ≈1980 and continued until ≈2003 when it plateaued.

Temporal and spatial patterns of small vertebrate roadkill in a supercity of eastern China.

An assessment of animal roadkill can help develop road mitigation measures. This article is the first to report data on animal-vehicle collisions (AVCs) in Nanjing, a supercity in eastern China. The research was conducted on a 224.27 km stretch of nine roads in Nanjing. In the period, between November 2020 and October 2021, 26 fortnightly monitoring missions were conducted to gather roadkill carcasses so that we could analyze their temporal and spatial distribution patterns. A total of 259 carcasses were collected, comprising 22 different species, of which 46.42% were mammals and 48.81% were birds. Cats and dogs are the most roadkill mammals, and blackbirds and sparrows are the most roadkill birds. The temporal analysis demonstrated that the peak of vertebrate roadkill occurred from May to July. Spatial analysis showed that the distribution patterns of vertebrate roadkill on different roads varied with a generally non-random distribution and aggregation. By mapping accidents using kernel density analysis, we were able to pinpoint locations that were at high risk for roadkill. Due to the fortnightly survey, our results would underestimate the casualties, even if, our study suggests that the problem of car accidents due to animals should be a cause for concern, and the results of the analysis of temporal and spatial patterns contribute to the establishment of mitigation measures.

Considerations on the impact of "source-sink" landscape pattern changes on urban thermal environment and cooling efficiency: a case study of Nanjing, China.

The urban heat island effect caused by rapid urbanization has had a great impact on human health and ecological environment. The evolution of landscape patterns often affects regional thermal characteristics at the local scale. How to rationally allocate land cover types from the perspective of urban planning is a huge challenge. This paper takes Nanjing, a typical "stove city" in China, as an example to study the impact of landscape pattern changes on the urban thermal environment. Firstly, based on the "source" landscape "/sink" landscape identified by the "source-sink" landscape index, on this basis, the contributions of the "source-sink" landscape and its effects are calculated, and the temporal and spatial evolution laws are analyzed. Second, we study the cooling effect of different characteristic landscapes. The results show that the change of landscape pattern is closely related to the urban thermal environment, and the expansion of built-up areas is the main reason for the urban thermal environment. With the development of urbanization, the "source-sink" landscape structure in most districts and counties has aggravated the heat island effect, and the ratios of "sink" and "source" landscape contribution ratios with strong levels are concentrated in the suburban areas. The results of cooling efficiency research show that the cooling range of forest land is larger than that of water bodies. At the same time, we found that the cooling efficiency of the sink landscape is the highest when the area of the sink landscape is 0.18-0.9 hm2 and the shape index is between 1 and 4. The research results can provide feasible and practical scientific suggestions for the planning and ecological construction of Nanjing.

[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.

[Analysis of O3 Pollution Characteristics, Formation Sensitivity, and Transport Impact in Southern Nanjing].

As one of the most important city clusters in China, surface ozone (O3) pollution in the Yangtze River Delta (YRD) Region has become a prominent air quality problem in recent years. Online observations of ambient O3, nitrogen oxides (NOx), and volatile organic compounds (VOCs) were conducted in southern Nanjing from July-September 2020 and April-May 2021. On this basis, the pollution characteristics of O3 were analyzed. The O3-VOCs-NOx sensitivity and the transport influence of its precursors were further discussed using models. The frequency statistics of the daily maximum 8-hour moving average (DMA-8h O3) and hourly concentration (O3-1h) showed that O3 pollution in southern Nanjing was more serious than that in urban areas. Three typical O3 pollution episodes were selected during the whole observation period, which included August 16th-27th, 2020; September 3rd-11th, 2020; and May 17th-25th, 2021. The O3-VOCs-NOx sensitivities in these three pollution episodes were analyzed using the observation-based model (OBM). The results of the relative incremental reactivity (RIR) and empirical kinetics modeling approach (EKMA) showed that the sensitivities of O3 formation in the three pollution episodes were in the NOx-limited regime, the transition regime, and the VOCs-limited regime, respectively. This difference in O3-VOCs-NOx sensitivity reflects that the site may have been influenced by transport. Therefore, the potential source contribution function (PSCF) and the concentration weighted trajectory (CWT) method were further used to analyze the potential source areas of NOx, VOCs, and O3 in these three pollution episodes. The results showed that there were obvious regional transport effects of NOx, VOCs, and O3 in these three pollution episodes. The location of potential sources differed in these three pollution episodes, which were affected by the eastern cities of the Lishui site; the urban area of Nanjing and eastern area of Anhui Province; and the urban area of Nanjing and the middle of the YRD Region, respectively. The impact of transport on O3 and its precursors also indicated the necessity of regional joint prevention and control of O3 pollution in the YRD Region.