Pearl River Research Articles

Local ecological knowledge reveals an undocumented population of Reeves’ butterfly lizard (Leiolepis reevesii) in Zhuhai, China

Though widespread and categorized as least concern by the IUCN Red List, Reeves’s butterfly lizard (Leiolepis reevesii) is considered critically endangered in China. Up-to-date data are warranted to inform future assessments and conservation measures. Through local ecological knowledge surveys and corroborated by field surveys, we discovered an undocumented L. reevesii population on Qi’ao Island of Zhuhai City, Guangdong Province, China. This discovery is the first record of the species in the Pearl River Delta since the early 2010s and represents the only remaining population from the vicinity of its type locality. It was reported to be very rare on the island now and has been extirpated from most of its previous range due to overharvesting, habitat loss and degradation. Our findings also raised concerns about the erosion of local ecological knowledge among local communities. Urgent conservation action and education campaigns are required to prevent further declines and raise awareness of this important and threatened population.

Amplified Secondary Organic Aerosol Formation Induced by Anthropogenic–Biogenic Interactions in Forests Around Megacities

AbstractThe amplification effect of anthropogenic‐biogenic interactions on secondary organic aerosol (SOA) formation remains debated, particularly regarding the impact of anthropogenic emissions on biogenic SOA (BSOA) formation in forests near megacities. This study concurrently measured typical biogenic and anthropogenic SOA tracers during day and night at the summit (1,690 m a.s.l.) and foot (200 m a.s.l.) of the Nanling mountains, a large subtropical forest adjacent to the Pearl River Delta (PRD) in southern China. Results revealed unexpectedly high concentrations of BSOA tracers (149.9 ± 70.5 ng m−3 at the summit and 109.7 ± 51.2 ng m−3 at the foot), surpassing those at most other background sites worldwide. Daytime BSOA tracer levels at the foot were consistent with nighttime levels, whereas the summit showed significantly higher concentrations at night. Nighttime correlations between O₃ and BSOA tracers at the summit suggest that high O₃ levels stimulate BSOA formation. Conversely, a negative correlation between O₃ and isoprene derived SOA (SOAI) tracers at the foot indicates that other oxidants may also influence SOAI formation. BSOA tracer concentrations rose significantly with the arrival of anthropogenic pollutants (e.g., SO₂ and NO₂), indicating that anthropogenic pollution amplifies BSOA formation by enhancing aerosol acidity (pH < 3). This amplification effect could be mitigated by the reduction of aerosol acidity due to increased NH₃ and relative humidity (RH). Our findings provide valuable insights into the interactions between anthropogenic and biogenic emissions on SOA formation and vertical distribution in forests surrounding megacities.

Structural Characteristics of Expressway Carbon Emission Correlation Network and Its Influencing Factors: A Case Study in Guangdong Province

Understanding the spatial correlation of transportation carbon emissions and their influencing factors is significant in achieving an overall regional carbon emission reduction. This study analyzed the structure characteristics of the expressway carbon emission correlation network in Guangdong Province and examined its influencing factors with intercity expressway traffic flow data using social network analysis (SNA). The findings indicate that the correlation network of expressway carbon emissions in Guangdong Province exhibited a “core-edge” spatial pattern. The overall network demonstrated strong cohesion and stability, and a significant difference existed between the passenger vehicle and freight vehicle carbon emission networks. The positions and roles of different cities varied within the carbon emission network, with the Pearl River Delta (PRD) cities being in a dominant position in the carbon network. Cities such as Guangzhou, Foshan, and Dongguan play the role of “bridges” in the carbon network. The expansion of differences in GDP per capita, industrial structure, technological level, and transportation intensity facilitates the formation of a carbon emission network. At the same time, geographical distance between cities and policy factors inhibit them. This study provides references for developing regional collaborative carbon emission governance programs.

Analysis of the Prevalence of Bacterial Pathogens and Antimicrobial Resistance Patterns of Edwardsiella piscicida in Largemouth Bass (Micropterus salmoides) from Guangdong, China

To gain insights into the prevalence and antimicrobial resistance patterns of major bacterial pathogens affecting largemouth bass (Micropterus salmoides) in the Pearl River Delta (PRD) region, Guangdong, China, a study was conducted from August 2021 to July 2022. During this period, bacteria were isolated and identified from the internal organs of diseased largemouth bass within the PRD region. The antimicrobial resistance patterns of 11 antibiotics approved for use in aquaculture in China were analyzed in 80 strains of Edwardsiella piscicida using the microbroth dilution method. The results showed that 151 bacterial isolates were obtained from 532 samples, with E. piscicida (17.29%, 92/532), Aeromonas veronii (4.70%, 25/532), and Nocardia seriolae (2.26%, 12/532) being the main pathogens. Notably, E. piscicida accounted for the highest proportion of all isolated bacteria, reaching 60.92% (92/151), and mainly occurred from November to April, accounting for 68.48% (63/92) of the cases. The symptoms in largemouth bass infected with E. piscicida included ascites, enteritis, and hemorrhaging of tissues and organs. The drug sensitivity results showed that the resistance rates of all E. piscicida strains to ciprofloxacin, all sulfonamides, thiamphenicol, florfenicol, enrofloxacin, doxycycline, flumequine, and neomycin were 96.25%, 60–63%, 56.25%, 43.75%, 40%, 32.5%, 16.25%, and 1.25%, respectively. In addition, 76.25% (61/80) of these strains demonstrated resistance to more than two types of antibiotics. Cluster analysis revealed 23 antibiotic types (A–W) among the 80 isolates, which were clustered into two groups. Therefore, tailored antibiotic treatment based on regional antimicrobial resistance patterns is essential for effective disease management. The findings indicate that in the event of an Edwardsiella infection in largemouth bass, neomycin, doxycycline, and flumequine are viable treatment options. Alternatively, one may choose drugs that are effective as determined by clinical drug sensitivity testing.

Geochemical characteristics and origin of crude oil and natural gas in different areas of Wenchang-A Sag, Pearl River Mouth Basin, South China Sea

Geochemical characteristics and origin of crude oil and natural gas in different areas of Wenchang-A Sag, Pearl River Mouth Basin, South China Sea

Source apportionment of organic carbon and black carbon in the surface sediments of the Pearl River Estuary and its adjacent South China Sea: insight from stable carbon and nitrogen isotopes

Coastal estuaries and adjacent continental shelf seas constitute vital global carbon reservoirs, and the sources and transformations of organic carbon in these regions are crucial to global biogeochemical cycles and climate change. This study investigated the total organic carbon (TOC), total nitrogen (TN), black carbon (BC), and their stable carbon and nitrogen isotopes (δ15NTN, δ13CTOC, δ13CBC) in the surface sediments of the Pearl River Estuary (PRE) and its adjacent northern South China Sea (NSCS) aiming to assess the impact of human activities on organic carbon dynamics in these areas. Results showed that the highest TOC concentrations occurred in the inner PRE due to intense human activities, and decreased seaward. The west side of the PRE exhibited higher TOC levels than the east side, which was attributed to differences in hydrodynamic processes and human activities. The westward flow of the Pearl River diluted water, which carried terrestrial organic matter inputs due to the influence of the Coriolis effect and intense local human activities, was a primary contributor to higher TOC levels on the west side (terrestrial source). In contrast, increased productivity and intensive mariculture activities on the east side predominated as sources of organic matter (marine source). Similar to the TOC, BC and TN sources were mainly influenced by human activities. δ15NTN distribution shows that TN in the east side of PRE mainly originated from industrial wastewater input from the Pearl River, while in the east side TN was mainly from domestic sewage discharge. Additionally, BC sources have shifted from primarily biomass combustion in the 1990s to fossil fuel emissions presently. Isotopic analysis revealed that over 70% of BC originated from fossil fuel inputs and C3 plant combustion, highlighting the significant influence of human activities in the PRE and adjacent NSCS, and underscoring the need for effective management and protection of the eco-environment in these regions.

Coexistence mechanisms and individual trophic niche variation between functionally analogous non-native and native carp species

Understanding the mechanisms that promote coexistence between functionally analogous non-native and native species that share similar prey is important for predicting the ecological consequences of their competitive interactions. Theory predicts that species coexistence is facilitated by stabilizing mechanisms that enhance inter-specific trophic niche partitioning, and/ or the equalizing mechanisms that reduce differences in the average fitness. Inter-specific niche partitioning, influenced by the ecological opportunity in prey resources, also affects intra-specific niche partitioning and individual niche expansion. These theories were tested using the non-native mrigal carp Cirrhinus mrigala and its congener native mud carp C. molitorella that coexist across the Pearl River basin, Southern China, with their trophic interactions analysed using DNA metabarcoding on fish gut contents sampled across the basin in both the dry and wet seasons of 2019 and 2021. The results revealed that the inter-specific trophic niche overlap was lower than their intra-specific trophic niche overlap, suggesting their coexistence was supported by stabilizing mechanisms. The ecological opportunity in prey resources was driving inter-specific niche partitioning and this partitioning then positively influenced intra-specific niche partitioning and individual niche expansion, especially in mrigal carp that had larger body sizes and occupied higher trophic positions at constricted individual niches. Fish body size also affected inter-specific niche partitioning and the relationship between inter- and intra-specific niche partitioning, with positive effects on both in mrigal carp but negative effects on both in mud carp. The results thus provide a mechanistic explanation on how closely related non-native and native species coexist and highlight the importance of dietary plasticity in facilitating the invasion of non-native species.

A data-driven ISM-BN model for safety analysis of inland shipping in the Pearl River Basin

Inland shipping of the Pearl River plays an important role in the Chinese shipping system. To ensure navigation safety, we collect reports of maritime accidents from 2015 to 2022 in the Pearl River basin. This article extracts influencing factors by collecting the experience of inland waterway safety navigation and analyzing accident reports. Then, this paper uses the interpretative structural modeling method (ISM) to build a correlation model. Using a data-driven Bayesian network (BN), it analyzes the impact of various factors on the safety navigation in the Pearl River. The model validation is completed by compared with tree augmented naive Bayes classifiers (TAN) network using the same validation samples, through validation with the test set, the prediction accuracy has improved by 25%. The results indicate factors such as vessel type, accident month, accident day and time, etc. have a significant impact on the safety of navigation in the inland Pearl River waterway. The method used can identify important risk factors for accidents and the average predictive probability of validation samples reaches 87.03%. These research results could be extended to maritime management efforts in the Pearl River Basin.

Socialist urbanism and cultural infrastructure facilities in China: Cities of the Pearl River Delta and the Guangzhou cultural infrastructure facilities plan, 2003–07

The construction of “cultural infrastructure facilities” (wenhua jichu sheshi) in China – auditoria, exhibition halls, libraries, museums, performance centers – for state administration of culture and information originated in the 1950s with Sino-Soviet exchange and has continued throughout the reform era. However, scholarship on urban development in China, embedded in discourses of capitalism and modern planning, generally does not recognize this category of infrastructure construction by contemporary city governments. To address the lacunae, this article analyzes the history of cultural infrastructure facilities in socialist urbanism, their transfer to the People’s Republic of China from the Soviet Union, the conditions of socialist realism, and the continuity of cultural infrastructure construction since the 1980s. Evidence from the Guangzhou Cultural Infrastructure Facilities Projects Plan (2003 – 07) and cultural facilities sites in the new city center projects of Shenzhen, Shunde, and Dongguan demonstrate how the party-state prioritizes the planning and construction of cultural infrastructure facilities. Contemporary architectural designs for new cultural buildings represent the international aesthetic of reform while cultural facilities continue to house and display party-sanctioned culture and information for the people.

The Impact of Urbanization on the Socio-Economic Status of Rural Migrants in China - A Comparison and Analysis for the Pearl River Delta and Yangtze River Delta Regions

The Pearl River Delta and Yangtze River Delta regions in China are two key areas of rapid economic development, and research has found that a large number of migrants from rural areas have been formed as a result of the rapid development of the urban agglomerations in the region, however, there is still a certain research gap on the comparison of the rural labour force populations of the two regions due to the different attractiveness of the rural transfer population in the two regions as well as the differences in the various local policies. Therefore, this paper reads the literature to compare the impact of the progress of urbanization in the Pearl River Delta and Yangtze River Delta on the economic status of rural migrants in China. The study finds that the Yangtze River Delta mainly attracts high-end technical talents while the Pearl River Delta attracts more migrant workers. Therefore, the governments of the two regions need to implement practical policies to provide migrants with corresponding protection.

The fate of atenolol in wastewater treatment plants of representative densely urban agglomerations in China.

Atenolol (ATL) that can decrease heart rate and reduce renin release is extensively used in the treatment of hypertension, angina, and other diseases. ATL's popularity has therefore drawn attention to its environmental behavior and potential impacts. Wastewater treatment plants (WWTPs) are the main collection point for ATL entering the water environment, highlighting the necessity of studying its fate in the environment. In this study, five WWTPs with different processes in China's representative densely urban agglomerations (Pearl River Delta [PRD] region) were selected as certain representative sampling sites to investigate the fate of ATL in the WWTPs over four seasons. Results showed that ATL concentration in the influent of these WWTPs was 146.5-918.6ng/L and the corresponding concentration in the effluent was 43.0-534.1ng/L, achieving a certain degree of removal. The seasonal ATL removal performance varied greatly among these WWTPs, Liede, Tai Po, and Sha Tin WWTPs showed better removal stability. Meanwhile, the average ATL removal rates in Tai Po (83.36%) and Sha Tin (81.67%) were higher than those in the Futian (71.24%), Liede (55.44%), and Stonecutters Island WWTPs (44.96%). The primary treatment capacity of Futian WWTP was better than that of Tai Po and Sha Tin WWTPs in removing ATL, while the performance of secondary treatment was opposite. Moreover, Zahn-Wellens test demonstrated that ATL could be almost completely degraded after 30 days and some protonated molecules (e.g., m/z 145 and m/z 190) metabolites were formed, indicating that degradation may play a role in ATL removal in WWTPs.

Variation characteristics and the influences of urbanization on hourly intense precipitation before and after monsoon onset over the Pearl River Delta.

The distinct spatiotemporal characteristics of the hourly intense precipitation (HIP) over the Pearl River Delta (PRD) and the impact of urbanization before and after the monsoon onset from 1972 to 2021 have been investigated using the hourly rain gauge data, nighttime lights data, and land use data. The results show a significant decreasing trend of HIP during the pre-monsoon onset period and a notable increasing trend during the post-monsoon onset period over the past five decades. However, compared to rural areas, rapid urbanization in the PRD after the mid-1990s weakens the HIP reduction, especially in the inland cities of PRD before the onset of the monsoon and enhances the HIP increase, particularly in the southeast inland and west coast cities after the onset of the monsoon. After rapid urbanization, the peak time of HIP has been postponed from 14 LST to 17 LST during the pre-monsoon onset period. HIP tends to occur more frequently in urban areas in the morning (10-12 LST) and evening (19-24 LST) compared to rural areas. In contrast, the impact of urbanization on the diurnal variation of HIP is not obvious during the post-monsoon period, despite higher frequencies of HIP occurring during the daytime (10-15 LST) in the urban areas after rapid urbanization. These findings provide valuable insights for forecasting HIP in urban agglomerations.

Factors influencing carbon and water use efficiency in changing environments

IntroductionVegetation plays a crucial role in terrestrial ecosystems, acting as a vital link connecting the lithosphere, hydrosphere, and atmosphere in terms of energy flow and material cycling. Changes in surface vegetation significantly regulate the water cycle, energy flow within terrestrial surfaces, and global carbon balance.MethodsThis study focuses on nine major river basins in China to quantitatively investigate the impacts of climate factors, vegetation dynamics, and land use changes on carbon use efficiency (CUE) and water use efficiency (WUE).ResultsThe primary controlling factors of WUE trends are NDVI (average contribution: 33.75% ± 6.90%) and VPD (average contribution: 28.04% ± 3.98%). NDVI predominates in the Haihe, Yellow River, Yangtze River, Pearl River, and Songliao River basins, while shortwave radiation (Srad) dominates in the southeastern rivers and inland river areas, and humidity (Shum) in the southwestern river basins. For CUE trends, the main controlling factors are Srad (average contribution: 36.46% ± 3.40%) and precipitation (Pre) (average contribution: 26.72% ± 5.20%). NDVI negatively influences the Huaihe River and southeastern river basins, while Pre negatively influences the Songliao River and Yellow River basins, and Srad negatively influences the Huaihe and southwestern river basins. Pre predominates in the Huaihe, Songliao, Haihe, southwestern river basins, and inland river areas, while Srad predominates in the Pearl River, Yangtze River, and Yellow River basins.DiscussionClimate factors and vegetation dynamics have significant regional impacts on WUE and CUE across different river basins, especially the roles of NDVI and VPD on WUE, and Srad and precipitation on CUE. These differences underscore the importance of developing region-specific management strategies to optimize ecosystem services in each basin.

Water security assessment and prediction for coastal Urban Agglomeration: a case study in the Pearl River Delta, east China

Water security assessment and prediction for coastal Urban Agglomeration: a case study in the Pearl River Delta, east China

County-Level Spatiotemporal Dynamics and Driving Mechanisms of Carbon Emissions in the Pearl River Delta Urban Agglomeration, China

Encouraging cities to take the lead in achieving carbon peak and carbon neutrality holds significant global implications for addressing climate change. However, existing studies primarily focus on the urban scale, lacking more comprehensive county-level analyses, which hampers the effective implementation of differentiated carbon mitigation policies. Therefore, this study focused on the Pearl River Delta urban agglomeration in China, adopting nighttime light data and socio-economic spatial data to estimate carbon emissions at the county level. Furthermore, trend analysis, spatial autocorrelation analysis, and Geodetector were adopted to elucidate the spatiotemporal patterns and influencing factors of county-level carbon emissions. Carbon emissions were predominantly concentrated in the counties on the eastern bank of the Pearl River Estuary. Since 2010, there has been a deceleration in the growth rate of carbon emissions in the region around the Pearl River Estuary, with some counties exhibiting declining trends. Throughout the study period, construction land expansion consistently emerged as a predominant factor driving carbon emission growth. Additionally, foreign direct investment, urbanization, and fixed asset investment each significantly contributed to the increased carbon emissions during different development periods.

Community-level trophic characteristics and interactions between native and non-native fish: The example of the Lower Pearl River Basin of China

Aquatic ecosystems can harbour more than one non-native fish species and this can represent a threat due to trophic interactions with native fishes. However, research on interactions amongst multiple co-occurring native and non-native fish remains scarce. In this study, 551 organisms from 44 native fish, 11 non-native fish, 35 macroinvertebrates (of which one was non-native), together with 162 samples of basal resources were collected from six rivers of the Lower Pearl River Basin of China. Nitrogen and carbon stable isotope analysis was used to calculate community-wide trophic metrics and the degree of trophic overlap between native and non-native fish at both the community and functional feeding group level, together with diet composition. At the community level, there was a high degree of trophic niche overlap between native and non-native fish as a result of similarities in trophic characteristics. At the functional feeding group level, both native and non-native functional feeding groups demonstrated the capacity to occupy the niche space of each other. A significant trophic niche overlap, exceeding 50%, was found between non-native detritivorous and omnivorous fish, suggesting competition. The difference in diet composition between some native and non-native fish depended on the category of diet source across the rivers, suggesting dietary segregation. Albeit limited, the present findings suggest that trophic interaction between native and non-native fish is likely to reach a dynamic equilibrium status in the community owing to trophic segregation of fish species and the antagonistic effects amongst non-native fish.

Evaluation of green development of energy consumption in the Pearl River Delta urban agglomeration based on radial basis function neural network

AbstractThe study utilizes the RBF neural network model to evaluate the green development of the Pearl River Delta urban agglomeration, revealing a consistent increase in development levels from 2005 to 2020 despite notable inter‐city variations. The model adeptly handles complex interactions within urban green development, offering insights into comprehensive impacts and aiding in policy evaluation and optimization. It provides urban planners and decision‐makers with data‐driven support, enhancing the scientific basis and stability of policy‐making.

Riverine sediment geochemistry and its dispersal pattern on the western Sunda Shelf

Understanding sediment provenance in continental shelf basins is essential for reconstructing paleoenvironmental changes, enhancing insights into sedimentary dynamics, and elucidating their contributions to the global carbon cycle. To decipher sediment provenances and enhance comprehension of the sediment dispersal patterns and the factors governing geochemical compositions on the Sunda Shelf, we conducted an exhaustive analysis of trace elemental concentrations and the isotopic ratios of strontium (87Sr/86Sr) and neodymium (εNd) in the silicate fractions of 35 surface sediment samples. These samples were collected from the western Sunda Shelf and its proximate major river end-members, namely, the Mekong, Rajang, Pahang, and Kelantan Rivers. Through the application of various statistical methodologies, including classical cluster analysis, Principal Component Analysis (PCA), the La-Sc-Th discrimination diagram, and an array of elemental ratios, we identified three distinct geochemical provinces on the Sunda Shelf. Each province is defined by unique geochemical signatures indicative of varied sediment sources or provenances. This distinction was primarily attributed to pronounced sediment heterogeneity, reflecting lithologic variances from the diverse river end-members. In pursuit of a holistic understanding of sediment provenance in the region, SrNd isotopic data was also integrated from prior studies encompassing the eastern Sunda Shelf and the southern South China Sea. By utilizing the SrNd mixing model, complemented with Monte-Carlo simulations, we estimated the sediment contributions from surrounding river end-members to the southern South China Sea basin. According to the model, the Mekong River emerges as the principal sedimentary source of the Sunda continental shelf and the southern South China Sea, attributed to its substantial sediment outputs. Additionally, the model has identified significant contributions from the Rajang, Pahang, and Kelantan rivers, particularly in offshore regions near their estuaries. Further, this study revealed the previously underappreciated influence of South China's rivers, namely the Red and Pearl Rivers, on the eastern Sunda Shelf and deeper southern South China Sea region beyond the continental shelf. This study not only delineates the dominant sediment sources influencing the Sunda Shelf and the South China Sea but also underscores the importance of considering a broad spectrum of river end-members to understand sedimentary dynamics in an active marine environment.

Distribution, sorption patterns, and outflows of riverine microplastics-affiliated linear alkylbenzenes and polycyclic aromatic hydrocarbons in a dynamic coastal zone.

Microplastics (MPs) pollution has emerged as a global concern. To mitigate the potential threats by MPs, particularly to coastal regions, it is crucial to comprehend the environmental behavior of MPs and their affiliated chemicals. In the present study, we collected floating MPs using a Manta net (0.33 mm mesh size) in a one-year sampling event in 2022 from the eight major estuaries in the Pearl River Delta, China, and also from five coastal sites in August and December in the same year. Nineteen linear alkylbenzenes (∑19LAB) and 16 polycyclic aromatic hydrocarbons (∑16PAH) affiliated with MPs were measured. The mean concentrations of MPs-affiliated ∑19LAB and ∑16PAH were 6710 (range: 3400-12300) and 5310 (range: 817-19,600) ng g-1, respectively, at the estuarine sites, and were 4920 (range: 2400-7600) and 2610 (range: 911-7890) ng g-1, respectively, at the coastal sites. Significant correlations were found between logarithmic MPs-water partition coefficients (log Kpw) and logarithmic suspended particulate matter-water partition coefficients (log Kd) values for LABs and PAHs, indicating analogous partitioning dynamics for MPs and suspended particulate matter with water. The annual riverine outflows were 1170 and 414 g for ∑19LAB and ∑16PAH, respectively. Although the riverine outflows of LABs and PAHs carried by MPs remain negligible compared to those by suspended particulate matter, an upward trend was identified between 2018 and 2022. Notably, the riverine input of LABs and PAHs carried by suspended particulate matter to the coastal ocean decreased from 2005/2006 to 2022, due to a combination of improved technological processes and energy structures.

Spatiotemporal estimation of surface NO2 concentrations in the Pearl River Delta region based on TROPOMI data and machine learning

Nitrogen dioxide (NO2) is a major air pollutant, and its concentration data are crucial for the study of air pollution and its impact on the environment. Although satellite data provide an effective method for estimating surface concentrations on a large scale through integrated modeling, the estimation of surface NO2 concentrations is hampered by the substantial amount of missing satellite data. This restricts in-depth studies of surface NO2 pollution. This study aims to reconstruct the missing data on tropospheric NO2 vertical column density from the TROPOspheric Monitoring Instrument (TROPOMI NO2). Subsequently, the reconstructed TROPOMI NO2 data and other predictor variables were utilized to estimate the daily surface NO2 concentrations at a 1 km resolution for the Pearl River Delta (PRD) region. The TROPOMI NO2 reconstruction models and the surface NO2 estimation model were both developed using the XGBoost algorithm. Additionally, comparative experiments were conducted between the XGBoost model and other traditional machine learning models, and the performances of the XGBoost model were evaluated through 10-fold cross-validation (CV) sample-based and site-based evaluations. The results indicate that the sample-based and site-based CV R2 values were 0.873 and 0.709, respectively. The feature importance scores indicate that TROPOMI NO2 was the most significant variable contributing to the estimation model. This indicates that the reconstruction of TROPOMI NO2 data and the development of an Extreme Gradient Boosting (XGBoost) model are suitable for the spatiotemporal estimation of surface NO2 concentrations in the PRD region, effectively reflecting the spatiotemporal distribution and evolution of surface NO2 concentrations in the area.