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1.
Arch Public Health ; 82(1): 175, 2024 Oct 07.
Article in English | MEDLINE | ID: mdl-39375748

ABSTRACT

BACKGROUND: As the second most populous country in the world, China has a huge demand for health human resources. Over the past decade, the Chinese government has continuously increased investment in the health sector and implemented relevant policies and systems in an attempt to enhance the overall quantity and equity of health human resources. This study aims to analyze the equity and developmental trends in the allocation of health human resources in China from 2012 to 2021, providing reference and theoretical support for the government's further optimization of health human resources allocation. METHODS: This study collected health human resources data from 31 provinces, municipalities, and autonomous regions in China from 2012 to 2021. The methods employed included Lorenz curves, Gini coefficients, and agglomeration degree analysis, which examined the developmental trends and equity of health human resources from the perspectives of population and geographical. RESULTS: This study found that over the past decade, there has been a significant increase in the total quantity of health human resources in China, accompanied by an improvement in equity, although disparities still exist. There are notable variations in the distribution of health human resources based on geographical area, with disparities between different regions. Relative shortages of health human resources are observed in western regions, while some areas in the eastern and central regions exhibit an abundance or surplus of health human resources. CONCLUSION: Overall, health human resources in China have experienced stable development, with an incremental improvement in allocation equity, yet there remains considerable room for progress. It is imperative to continue strengthening policy guidance and regulation to facilitate the rational flow of health human resources, narrow regional disparities, and achieve the goal of universal health coverage.

2.
ACS Biomater Sci Eng ; 2024 Oct 07.
Article in English | MEDLINE | ID: mdl-39373188

ABSTRACT

Hydroxyapatite nanoparticles (nHA) have gained attention as potential intracellular drug delivery vehicles due to their high binding affinity for various biomolecules and pH-dependent solubility. Yet, the dependence of nHA cytocompatibility on their physicochemical properties remains unclear since numerous studies have revealed starkly contrasting results. These discrepancies may be attributed to differences in size, shape, crystallinity, and aggregation state of nHA, which complicates fundamental understanding of the factors driving nHA cytotoxicity. Here, we hypothesize that nHA cytotoxicity is primarily driven by intracellular calcium levels following the internalization of nHA nanoparticles. By investigating the cytotoxicity of spherical nHA with different crystallinity and dispersity, we find that both lower crystallinity and increased agglomeration of nHA raise cytotoxicity, with nanoparticle agglomeration being the more dominant factor. We show that the internalization of nHA enhances intracellular calcium levels and increases the production of reactive oxygen species (ROS). However, only subtle changes in intracellular calcium are observed, and their physiological relevance remains to be confirmed. In conclusion, we show that nHA agglomeration enhances ROS production and the associated cytotoxicity. These findings provide important guidelines for the future design of nHA-containing formulations for biomedical applications, implying that nHA crystallinity and especially agglomeration should be carefully controlled to optimize biocompatibility and therapeutic efficacy.

3.
Food Chem ; 463(Pt 3): 141309, 2024 Sep 17.
Article in English | MEDLINE | ID: mdl-39326307

ABSTRACT

Ultrasonic compaction, also known as ultrasonic agglomeration, is an emerging technology that represents a novel alternative for food agglomeration; it is of great interest to the food industry. This review aims to gather information on the physicochemical, organoleptic, microbiological, and structural changes generated by ultrasound and study the fundamentals of agglomeration and ultrasound in different food matrices. In addition, chemical changes are reported in some nutrients related to conformational changes, such as the disintegration of diacylglycerides into monoacylglycerols, disordering of the crystalline region of starch granules to the amorphous phase, disruption of the membrane in plant cells, and transient or permanent modification of the protein structure (3D folding). The increasing development of patents can provide an insight into the potential of ultrasonic agglomeration applications in the food industry.

4.
Environ Geochem Health ; 46(11): 455, 2024 Sep 25.
Article in English | MEDLINE | ID: mdl-39320603

ABSTRACT

The accurate identification of pollutant sources and their spatial distribution is crucial for mitigating soil heavy metals (SHMs) pollution. However, the receptor model struggles to effectively categorize pollutant sources and pinpoint their locations and dispersion trends. We propose a novel comprehensive framework that combines a receptor model, random forest (RF), affinity propagation (AP) algorithm, and bivariate local indicator of spatial association (BLISA), to optimize the traditional approach for tracing SHMs sources in industrial regions. We apportioned SHMs sources using a receptor model combined with RF, while BLISA combined with AP methods were employed to accurately locate the source areas and identify their dispersion tendencies. The results revealed that SHMs originated from mixed sources of equipment manufacturing agglomeration and agricultural activities (59.0%), geological background (30.5%), and emissions from heavily-polluting industries (10.5%). The pollution sources of soil Cd and Pb were located near specific industries, showing characteristics of multi-site concurrent pollution diffusion influenced by their proximity to industrial sites. The spatial distribution of Cr, Cu, and Zn sources was concentrated in high-density urban industrial areas, transitioning from point to nonpoint sources, with diffusion patterns influenced by the spatial agglomeration effect of industries. Our enhanced framework accurately identifies the location of SHMs sources and their dispersion tendencies, thereby improving regional soil pollution management.


Subject(s)
Algorithms , Environmental Monitoring , Metals, Heavy , Soil Pollutants , Metals, Heavy/analysis , Soil Pollutants/analysis , Environmental Monitoring/methods , Spatial Analysis , Environmental Pollution/analysis , China , Models, Theoretical , Soil/chemistry
5.
Chemosphere ; 365: 143277, 2024 Oct.
Article in English | MEDLINE | ID: mdl-39260594

ABSTRACT

Despite our growing awareness of micro-and nanoplastics presence in food and beverages, the fate of nanoplastics (NPs) in the human gastrointestinal tract (GIT) remains poorly investigated. Changes of nanoplastics size upon digestive conditions influence the potential of absorption through the intestine. In this study, polymer nanoparticles with different physicochemical properties (size, surface and chemistry) were submitted to gastrointestinal digestion (GID) simulated in vitro. Their agglomeration behaviour was measured with a unique set of analytical approaches, allowing to study NPs' interactions with the digestive enzymes. Smaller NPs agglomerated more, narrowing the overall particle size distribution of smaller and larger NPs. NPs of different polymers exhibited heteroagglomeration. Digestive enzymes interact with the NPs, forming large but fragile agglomerates. In presence of the enzymes, even acid-functionalized NPs, typically stable in harsh conditions, agglomerated similarly to the non-functionalized PS NPs. These results highlight the role of the GID in increasing the effective size of ingested NPs, potentially reducing their ability to pass through the cell membranes. Our findings address a critical knowledge gap in nanoplastics oral uptake potential, providing a solid technical foundation for their characterization.


Subject(s)
Digestion , Gastrointestinal Tract , Nanoparticles , Particle Size , Gastrointestinal Tract/metabolism , Humans , Nanoparticles/chemistry , Polymers/chemistry , Plastics/chemistry
6.
J Environ Manage ; 369: 122330, 2024 Oct.
Article in English | MEDLINE | ID: mdl-39226808

ABSTRACT

Extreme meteorological events and rapid urbanization have led to serious urban flooding problems. Characterizing spatial variations in flooding susceptibility and elucidating its driving factors are essential for preventing damages from urban pluvial flooding. However, conventional methods, limited by spatial heterogeneity and the intricate mechanisms of urban flooding, frequently demonstrated a deficiency in precision when assessing flooding susceptibility in dense urban areas. Therefore, this study proposed a novel framework for an integrated assessment of urban flood susceptibility, based on a comprehensive cascade modeling chain consisting of XGBoost, SHapley Additive exPlanations (SHAP), and Partial Dependence Plots (PDP) in combination with K-means. It aimed to recognize the specific influence of urban morphology and the spatial patterns of flooding risk agglomeration under different rainfall scenarios in high-density urban areas. The XGBoost model demonstrated enhanced accuracy and robustness relative to other three benchmark models: RF, SVR, and BPDNN. This superiority was effectively validated during both training and independent testing in Shenzhen. The results indicated that urban 3D morphology characteristics were the dominant factors for waterlogging magnitude, which occupied 46.02 % of relative contribution. Through PDP analysis, multi-staged trends highlighted critical thresholds and interactions between significant indicators like building congestion degree (BCD) and floor area ratio (FAR). Specifically, optimal intervals like BCD between 0 and 0.075 coupled with FAR values between 0.5 and 1 have the potential to substantially mitigate flooding risks. These findings emphasize the need for strategic building configuration within urban planning frameworks. In terms of the spatial-temporal assessment, a significant aggregation effect of high-risk areas that prone to prolonged duration or high-intensity rainfall scenarios emerged in the old urban districts. The approach in the present study provides quantitative insights into waterlogging adaptation strategies for sustainable urban planning and design.


Subject(s)
City Planning , Models, Theoretical , Urbanization , Climate Change
7.
Environ Technol ; : 1-13, 2024 Sep 21.
Article in English | MEDLINE | ID: mdl-39306689

ABSTRACT

Fire smoke, consisting of solid particles and liquid droplets, poses risks of asphyxiation, poisoning, making it a significant contributor to fire-related fatalities and environmental pollution. The exploration of effective smoke control methods represents a vital approach to reducing the threat of fire smoke to public health and safety. This study aims to determine the characteristics of elimination for the fire smoke generated from burning four typical materials, thereby validating the universality of electric agglomeration smoke elimination technology. The results indicate that the elimination efficiency of electric agglomeration varies with the material type of the smoke. The rate of change in smoke transmittance from fast to slow is: polyvinyl chloride (PVC), polystyrene (PS), wood, and styrene butadiene rubber (SBR), respectively. With an external potential of 4 kV, PVC smoke reaches the safe threshold after 12.1 s, while SBR smoke achieves it in just 4.9 s. Analysis of the microscopic morphology of agglomerates with scanning electron microscopy (SEM) reveals that particle size distribution is an important factor affecting electric agglomeration elimination. This is because larger initial particles carry a greater charge, enabling the formation of larger agglomerates for more efficient removal. This study provides theoretical guidance for the practical application of electric agglomeration in eliminating smoke particles.

8.
Sci Rep ; 14(1): 22234, 2024 Sep 27.
Article in English | MEDLINE | ID: mdl-39333208

ABSTRACT

Firm location studies traditionally assume that this is business that attracts other business to a given location. They focus on knowledge transfers between the most productive and innovative firms and analyse agglomeration economies arising from matching, learning and sharing mechanisms. We argue that the population density also attracts firms to the place. Therefore, we extend this stream of research by using the concept of economies of density to discuss the effects of the attraction of firms by population. Our study explores the existence of the hierarchical causal mechanism that occurs when 2nd line firms understood as non-innovative, less productive retail and service businesses together with human settlement create an environment that attracts 1st line firms - the most innovative and productive businesses. We show that population density and business agglomeration jointly affect the location of firms in different sectors and should be considered as complementary rather than substitutable attraction factors.

9.
Front Public Health ; 12: 1476339, 2024.
Article in English | MEDLINE | ID: mdl-39314793

ABSTRACT

Introduction: This study aims to explore the impact of economic agglomeration on the urban prosperity through economies of scale and agglomeration, it may also affect the public health of the agglomeration area. Methods: This paper takes 280 cities in China as the research object, and explores the impact of economic agglomeration on public health through a two-way fixed effects model, instrumental variable method, and generalized moment estimation. Results: The results indicate that: (1) the improvement of China's economic agglomeration can significantly promote urban public health, and economic agglomeration is a prerequisite for the improvement of urban public health, but there is no reverse causal relationship. (2) The enhancement of economic agglomeration in Northeast China has the greatest promotion effect on public health, followed by the eastern, western, and central regions; The economic agglomeration enhancement of the pilot medical group in closely connected cities has a greater promoting effect on public health than the pilot medical group in non-closely connected cities. (3) Empirical results based on micro sample data show that the improvement of economic agglomeration will also promote the increase of the number of public hospitals in cities. Discussion: This study emphasizes the important role of economic accumulation in the improvement of urban public health and provides empirical support for future economic development policies and practices.


Subject(s)
Economic Development , Public Health , China , Humans , Public Health/economics , Cities , Urban Health/economics , Urban Health/statistics & numerical data , Urban Population/statistics & numerical data
10.
Sci Total Environ ; 954: 176402, 2024 Sep 18.
Article in English | MEDLINE | ID: mdl-39304138

ABSTRACT

This study firstly examines the quality of marine eco-environment in Africa using Tapio decoupling model, and analyzes the sustainability level of the development of "population agglomeration - marine environment - economic growth". Secondly, a series of econometric tools, such as ARDL, FMOLS, AMG model and DH panel causality test, are used to investigate the long- and short-term impacts of economic growth, population agglomeration, marine capture and energy consumption on the African marine eco-environment, and to analyze the differences between the sub-regions in Africa. The results indicate that: Adebayo and Kirikkaleli (2021) (Adebayo and Kirikkaleli, 2021) the decoupling state of "population-environment" has shifted from expansive negative decoupling to more optimized strong decoupling, and "economy-environment" has gradually changed from strong negative decoupling and expansive negative decoupling to strong decoupling. Ali et al. (2017) (Ali et al., 2017) There existed a bi-directional causal relationship between the degree of marine environment degradation and economic growth, population agglomeration, marine capture and energy consumption. Al-Mulali and Sab (2012) (Al-Mulali and Sab, 2012) In the short term, the economic EKC hypothesis does not hold in North and West Africa, while Central, East and Southern Africa are consistent with the EKC hypothesis. In the long term, the EKC hypothesis is valid in Central, East and Southern Africa, while is not valid in North and West Africa. Overall, reducing population agglomeration levels, marine fishing and energy consumption might mitigate marine environmental degradation in Africa.

11.
Sci Rep ; 14(1): 20520, 2024 Sep 03.
Article in English | MEDLINE | ID: mdl-39227480

ABSTRACT

The aim of this paper is to explore whether and how urban road transport (URT) development affects haze pollution. One of the innovations of this paper is that URT development is measured by road accessibility with novel digital elevation model datasets, which have been used by few scholars. The endogenous problem caused by revere causality issue in the relationship between URT development and haze pollution is also considered. Based on the panel data of prefecture-level cities of Yangtze River Delta (YRD) region in China from 2011 to 2018, this paper uses long-lagged values of URT development as the instrumental variable, employing the two-stage least squares (2SLS) method. The study shows that URT development leads to an increase of haze pollution. Moreover, mechanism tests based on moderating and mediating models support the finding that decreasing haze pollution resulted from better connection effects, while rising agglomeration effects tend to bring about increasing haze pollution, and the latter effect is larger in magnitude than the former. Current URT development may have long-term negative consequences for livability of YRD cities, and urban decision makers should reconsider the effectiveness of the current road transport investment and construction.

12.
J Mol Graph Model ; 132: 108838, 2024 Nov.
Article in English | MEDLINE | ID: mdl-39153377

ABSTRACT

In this paper, the geometric analysis of carbon nanotubes (CNTs) without external loading is carried out by energy method. Based on the theory of molecular mechanics, an improved mechanical model is proposed to predict the energy of armchair carbon nanotubes under stress-free conditions, and the diameter of CNTs is estimated according to the principle of minimum energy. The results show that the diameter obtained by the improved model is larger, but basically consistent with that obtained by conformal mapping. The inversion energy term is added to the modified model, and the inversion energy term related to atomic curvature is characterized by the conization angle. It can be seen from the error that the inversion energy of carbon nanotubes can not be neglected in the stress-free state, especially in the case of small diameter. The agglomeration of nanotubes is one of the important factors, which affects the effective elastic modulus of nanocomposites. Here, a new micro-mechanics model consisting of both agglomeration of CNTs and pure matrix is also presented to analyze its effect on the effective elastic modulus. It is noted from the results that the stiffness of nanocomposites is very sensitive to the CNTs agglomeration.


Subject(s)
Nanocomposites , Nanotubes, Carbon , Polymers , Nanotubes, Carbon/chemistry , Polymers/chemistry , Nanocomposites/chemistry , Elastic Modulus , Models, Molecular , Thermodynamics
13.
J Environ Manage ; 368: 122109, 2024 Sep.
Article in English | MEDLINE | ID: mdl-39126843

ABSTRACT

Understanding the characteristics of waterlogging in urban agglomeration is essential for effective waterlogging prevention and management, as well as for promoting sustainable urban development. Previous studies have predominantly focused on the driving mechanisms of waterlogging in urban agglomeration at a single scale, but urban agglomeration space has greater spatio-temporal heterogeneity, it is often difficult to fully reveal such characteristics at a single scale. Consequently, this study endeavors to explore the spatio-temporal evolution characteristics and underlying mechanisms of waterlogging incidents within urban agglomerations by adopting a multi-scale analytical approach. The results indicate that: (1) The waterlogging degree and high-density zones increase in the GBA, and the waterlogging points are spatially polycentric. However, the waterlogging point in Hong Kong is decreasing. (2) The influence of ISP and AI on waterlogging is dominant at all scales, followed by RE and Slope. ISP∩Slope and ISP∩RE are the key interactions for waterlogging. (3) The aggregation of waterlogging decreases with grid scale, and the influence of land cover factors on waterlogging increases with grid scale. Moreover, the findings at the grid scale outperformed those at the watershed scale, indicating that the grid scale is more conducive to the investigation of waterlogging in urban agglomerations. This research broadens our comprehension of the mechanisms behind waterlogging in urban agglomeration and provide references for policy decisions on waterlogging prevention and mitigation within urban agglomerations.


Subject(s)
Bays , Hong Kong , China , Macau , Urbanization
14.
J Environ Manage ; 368: 122177, 2024 Sep.
Article in English | MEDLINE | ID: mdl-39137641

ABSTRACT

Carbon sequestration is vital to maintaining carbon neutrality and mitigating climate change's impact on humans and the environment. As the government's role in eco-advocacy is primarily designed to safeguard the environment, this paper discusses the impact of government environmental regulations on carbon sequestration. By analyzing 286 cities from 2000 to 2019 in China, we propose that government environmental regulation can lead to a 0.77% increase in carbon sequestration. Additionally, industrial agglomeration and industrial structure advancement are regarded as viable channels. As a result of the differences in city types, government intervention, and public concern across different cities, the impact is likely to vary as well.


Subject(s)
Carbon Sequestration , Climate Change , China , Cities , Humans , Environmental Policy , Carbon
15.
J Environ Manage ; 368: 122261, 2024 Sep.
Article in English | MEDLINE | ID: mdl-39186853

ABSTRACT

The Sustainable Development Goals (SDGs) are essential measure for preserving the balance between human well-being and natural ecosystems. The benefit of preserving ecosystems health play a crucial role in promoting the SDGs by providing stable ecosystem services (ESs). However, the ecological health of mountainous cities is vulnerable, with relative low ecological resilience. To investigate the conflict between ecosystems and sustainable development, this study takes the Chengdu-Chongqing Urban Agglomeration as the study area. The major tasks and results in this study include: (1) using the entropy weighting method and the InVEST model, we combined remote sensing, geographic, and statistical data to quantify three types of SDGs (economic, social, environmental) and four ESs (water yield, soil conservation, habitat quality, carbon storage), and establish a localized sustainable development assessment framework that is applicable to the Chengdu-Chongqing Urban Agglomeration. The results show that from 2014 to 2020, the three types of SDGs exhibited an overall upward trend, with the lowest values occurring in 2016. The gap between different counties has narrowed, but significant regional differences still remain, indicating an unbalanced development status quo. Among the 142 counties, water yield and soil conservation values show a consistent downward trend but occupies significant interannual variations, while habitat quality and carbon storage values increases consistently each year. (2) using Spearman's nonparametric correlation analysis and multiscale geographically weighted regression model to explore the temporal variation and spatial heterogeneity of correlations between county ESs and SDGs. The results showed significant heterogeneity in the spatial trade-offs and synergies between ESs and SDGs, with two pairs of synergies weakening, seven pairs of trade-offs increasing, and the strongest negative correlation between Economic Sustainable Development Goals and habitat quality. (3) we applied the self-organizing mapping neural networks to analyze the spatial clustering characteristics of ESs-SDGs. Based on the spatial clustering effects, we divides the Chengdu-Chongqing Urban Agglomeration into four zones, and different zones have different levels of ESs and SDGs. The targeted strategies should be adopted according to local conditions. This work is of great practical importance in maintaining the stability and sustainable development of the Chengdu-Chongqing Urban Agglomeration ecosystem and provides a scientific reference for the optimal regulation of mountainous cities.


Subject(s)
Cities , Conservation of Natural Resources , Ecosystem , Sustainable Development , Soil , China
16.
J Environ Manage ; 369: 122238, 2024 Oct.
Article in English | MEDLINE | ID: mdl-39208749

ABSTRACT

Agricultural carbon emissions pose a significant challenge in combating climate change and achieving sustainable development objectives. These emissions predominantly stem from the decisions made by stakeholders, and the potential economic and social benefits associated with agricultural product brands determine their capacity to influence stakeholder behavior. This study utilizes panel data from 30 provinces in China spanning from 2008 to 2021 to examine the impact of agricultural product brands on agricultural carbon emission intensity and its underlying mechanisms. The findings indicate that: (1) Agricultural product brands contribute to lowering agricultural carbon emission intensity within a region, while also exerting a negative spillover effect on neighboring areas. (2) Agricultural product brands foster a decline in agricultural carbon emission intensity by bolstering the agricultural industry agglomeration. (3) Agricultural scale operation exhibits a threshold effect between agricultural product brands and agricultural carbon emission intensity, with the mitigation effect becoming increasingly pronounced as the threshold range expands. The research findings can offer valuable insights into leveraging the advantages of agricultural product brands to facilitate the reduction of agricultural carbon emissions.


Subject(s)
Agriculture , Carbon , Climate Change , Carbon/chemistry , China
17.
Heliyon ; 10(15): e35262, 2024 Aug 15.
Article in English | MEDLINE | ID: mdl-39161820

ABSTRACT

The "Broadband China" has enabled China to achieve leapfrog development in the construction of its high-speed broadband networks, thereby accelerating the development of digital infrastructure and unleashing the potential for financial sector growth. This has created a strong impetus for economy to shift towards high-quality development. An in-depth understanding of the empirical correlation between the development of digital infrastructure and financial progress is absent, leaving an unexplored domain of research concerning the impact of the "Broad China" strategy on financial agglomeration (Finagg), financial scale (Finscal), and digital finance (Digfina). In order to evaluate the dynamic impacts of this policy on financial development, this research builds a multi-period difference in differences (DID) model using panel data from 269 prefecture-level cities between 2011 and 2020. The study concludes that the "Broadband China" policy significantly fosters the growth of Finagg, Finscal, and Digfina, in China, and found that the "Broadband China" policy has a significant impact on the regional heterogeneity of financial agglomeration and digital finance. There are significant variations in the effects of this policy on different regions, while the regional heterogeneity differences in the impact on financial scale are relatively small. Additionally, the three mediating variables of technological innovation, fund support, and talent agglomeration play a mediating role in the mechanism of digital infrastructure on financial development.

18.
Sci Rep ; 14(1): 19628, 2024 Aug 23.
Article in English | MEDLINE | ID: mdl-39179730

ABSTRACT

Transport accessibility is crucial for defining urban clusters and evaluating a region's centrality and connectivity. To foster equitable growth in urban conglomerates, it is crucial to understand the relationship between transport accessibility and regional development. This study introduces the concept of 'regional efficiency'-the effectiveness of converting regional inputs into outputs-determined via the super-efficiency Data Envelopment Analysis methodology, to assess the progression of regional development. Employing a combination of bivariate spatial autocorrelation and spatial regression analysis, this research elucidates the spatial dynamics between transport accessibility and regional efficiency, both at macro and micro levels. A binary Logit model identifies the factors affecting the Moran's I correlation between regional efficiency and transport accessibility. Based on the diverse urban characteristics within a single conglomerate, tailored development strategies are suggested. Focusing on the Yangtze River Delta Urban Agglomeration in China as a case study, four distinct spatial clusters-High-High (HH), Low-Low (LL), High-Low (HL), and Low-High (LH)-are identified, based on the local correlation between regional efficiency and transport accessibility. The findings reveal that regions with a High-High Moran's I correlation between road accessibility and regional efficiency predominantly located in the eastern sectors of the Yangtze River Delta, exhibiting effective regional efficiency. These regions are characterized by superior road accessibility, aligning well with their regional efficiency metrics. For air accessibility, cities classified under the HH category, including Shanghai and its neighboring cities, demonstrate a significant spatial correlation with regional efficiency. Population density and urban tier are key predictors of the significance of the Moran's I correlation between road accessibility and regional efficiency. In contrast, for air accessibility, these factors assume an inverse role. The identified cluster types (HH, LL, LH, and HL) are proposed as predictive indicators for the significance of the Moran's I relationship between air accessibility and regional efficiency.

19.
Sci Total Environ ; 950: 175068, 2024 Nov 10.
Article in English | MEDLINE | ID: mdl-39094651

ABSTRACT

Chengdu Plain Urban Agglomeration (CPUA) is one of the most serious areas suffering from ozone pollution in China. A comprehensive field observation focused on the ozone production rate and its sensitivity was conducted at CPUA in the summer of 2019. Six sampling sites were set and two ozone pollution episodes were recognized. The daily maximum 8-h average (MDA8) O3 concentration reached 137.9 ppbv in the urban sites during the ozone pollution episode. Peak concentration of O3 was closely related to intense solar radiation, high temperatures, and precursor emissions. The OH-HO2-RO2 radical chemistry and ozone production rate (P(O3)) were calculated using an observation-based model (OBM). The daily peak OH concentration varied in the range of 3-13 × 106 molecules cm-3, and peak HO2 and RO2 were in the range of 2-14 × 108 molecules cm-3 during ozone pollution episodes. During the ozone pollution episode, the average maximum of P(O3) in suburban sites (about 30 ppbv h-1.) was compared with urban sites, and the maximum of P(O3) was 18 ppbv h-1 in rural sites. The relative incremental reactivity (RIR) results demonstrate that it was a VOCs-limited regime in the central urban area of Chengdu, with NOx suppression effect in some regions. In the southern neighboring suburb of Chengdu, it was VOCs-limited as well. However, the northern suburban area was a transition region. In the remote rural areas of the southern CPUA, it was highly NOx-limited. Local ozone production driven by the photochemical process is crucial to the ozone pollution formation in CPUA. The geographically differentiated recognition of the ozone regime found by this study can help to tailor control strategies for local conditions and avoid the negative effects of a one-size-fits-all approach.

20.
Sci Total Environ ; 950: 175399, 2024 Nov 10.
Article in English | MEDLINE | ID: mdl-39127211

ABSTRACT

Evaluating the differences in evapotranspiration between urban and surrounding non-urban areas (i.e., ∆ET) has critical implications for urban ecological planning and water resources management. However, it is unclear how the magnitude of changes in ∆ET caused by urbanization varies under different climatic conditions in China. Here, using the remotely ET estimates at 1 km spatial resolution, we firstly estimated the magnitude of changes in ∆ET and then quantified the main driving factors influencing variations in ∆ET of 7 national-level urban agglomerations (UAs) across China during 2003-2020. Results showed that all annual ETurban values were smaller than ETnon-urban of 7 UAs, and the absolute ∆ET values of cities in South China were generally higher than those in North China. There is an apparent effect of urbanization on ∆ET increase in Guanzhong Plain City Group, Central Plain UA and Guangdong-Hong Kong-Macao Greater Bay Area (GHKMGBA), while ∆ET decrease in Chengdu-Chongqing City Group and Yangtze River Delta (YRDUA) were primarily due to the climate change. The suppressing effects of temperature and NDVI on ∆ET decrease in YRDUA were enhanced, and the promoting effect of GDP on ∆ET increase in GHKMGBA was weakened. Considering nonstationary features, urbanization appears to heighten extreme ∆ET by 0.83 %, 4.83 % and 10.39 % under 5-year, 20-year, and 50-year return periods over all the 7 UAs, respectively. Collectively, our findings confirm that urbanization is a significant factor that leads to ∆ET increase, and the factors affecting the response of urban water circulation system need to be deeply decomposed.

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