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This study examines the polymorphous role of the Chinese provincial government in planning, financing, and constructing intercity railways in the Pearl River Delta region. Provincial governments claim absolute ownership in railway planning and land development surrounding railway stations. Informed by the state-theoretical perspective, we developed a conceptual framework that examines the city-regional governance of Chinese states with an emphasis on their capacity for regulation. Provincial governments selectively bargain with ministries and municipalities during development and they are flexible in the multi-scalar politics of railway projects. Their competence lies in their initiatives to gain knowledge of local land development. Our findings suggest that the polymorphous role of the provincial government extends beyond its usual function as a mediator in central-local relations and that its strategic nature reflects the complexity of China's state powers and regulatory regimes. Meanwhile, local authorities pursue urban growth and central ministries aspire to exert their regulations on localities. [ABSTRACT FROM AUTHOR]

The advancement of urbanization has led to a decline in the ecological function and environmental quality of cities, seriously reducing the services and sustainable development capacity of urban ecosystems. The construction of the National Forest Urban Agglomeration of China is conducive to alleviating the ecological and environmental problems brought about by rapid urbanization and promoting sustainable urban development. A time series analysis of ecological network changes can quickly and effectively explore the development and changes of ecological spatial patterns over time. Identifying ecological protection and restoration areas in urban agglomerations is an important way to promote ecosystem restoration and optimize ecological networks. This paper takes the Pearl River Delta forest urban agglomeration as the research area, uses multi-source remote sensing data from 2000 to 2020 (every 5 years), identifies ecological sources based on the morphological spatial pattern analysis (MSPA) method, generates ecological corridors based on the minimum cumulative resistance (MCR) model, constructs a time series ecological network pattern in the Pearl River Delta region, and analyzes the evolution process of the ecological network pattern over time. The results indicate that over time, the core green area in the ecological network pattern of the Pearl River Delta first decreased and then increased, and the complexity of ecological corridors first decreased and then increased. The main reason is that the urbanization process in the early 21st century led to severe ecological fragmentation. Under the promotion of the national forest urban agglomeration construction, the ecological network pattern of the Pearl River Delta was restored in 2015 and 2020. The time series analysis of the ecological network pattern in the Pearl River Delta region of this research confirms the effectiveness of the construction of forest urban agglomerations, providing a scientific reference for the identification of ecological networks and optimization of spatial patterns in forest urban agglomerations. [ABSTRACT FROM AUTHOR]

Between 1958 and 1999, notable lithic localities recorded prehistoric activities in Xiqiao Town of Nanhai District, Foshan City, Guangdong Province, from which double-shouldered and microlith-stone artefacts were uncovered. Currently, the "Xiqiaoshan site" is recognized as a substantial Neolithic quarry and processing location, dating back to 4 ‒ 7 ka B P. Subsequently, from 2011 to 2022, we conducted multiple geological environmental surveys and analyses on Xiqiaoshan Mountain. A well-preserved Quaternary stratigraphic profile was discovered north of Fuxian village in the southeast foothills of Xiqiaoshan Mountain. The sedimentological, geochemical, and geochronological results indicate the presence of two primary sedimentary strata in the Fuxian locality. The upper unit comprises the Holocene swamp facies, with a calibrated AMS14C dating range from 5052‒ 5409 a B P; whereas, the lower unit comprises the late Pleistocene alluvial-diluvial strata, with a calibrated AMS14C dating range from 38420‒40502 a B P, and an optically stimulated luminescence (OSL) dating range of 41.977 ‒ 43.796 ka B P. Late Pleistocene strata yielded two sand-gravel layers containing Paleolithic artefacts, which are marked as layers A1 and A2. The predominant artefacts in lower layer A1 include larger scrapers, pointed tools, tongue-shaped edged tools, and small flake tools, such as various scrapers, denticulates, notches, knives, utilized flakes, and cores, including tanged axe-shaped knives. In the upper layer A2, backed or tanged knives appear more frequently. The other small flake tools from this layer (A2) were not significantly different from those in lower layer A1. One bifacially prepared core for producing small elongated flakes is of particular interest for this artefact. Based on the average deposition rate, the computational age of the A1 layer was 46.511‒ 47.325 ka B P, whereas that of the A2 layer was 41.977‒42.167 ka B P. Although the number of artefacts within the Holocene sediments (>5 ka B P) overlying the late Pleistocene strata is limited, the characteristics of inheritance and development are still evident in the types of artefacts. The discovery presented in this study has completely updated and extended the connotation of Xiqiaoshan National Geopark and "Xiqiaoshan culture, "breaking through the late Pleistocene Paleolithic remains records with exact dating in the Pearl River Delta region for the first time. Therefore, a ground-breaking discovery can accurately trace the footsteps of modern humans in the coastal areas of South China from 40‒50 ka. It also reveals the rich features of lithic industry and the developmental characteristics and evolution of its cultural connotations during this period. The present study shows that during the relatively warm and humid conditions of marine isotope stages 3 (MIS3) interglacial period and the subsequent cold and arid stage of MIS2, human population in the Fuxian locality encountered environmental challenges and adopted new subsistence strategy, which is of great significance for understanding modern human responses and adaptations to global and regional environmental and climate change. [ABSTRACT FROM AUTHOR]

With global change and urban expansion, the city's vulnerable to climate-induced disasters is increasing significantly. Addressing this challenge has become a global priority and there is an urgent need to improve the resilience and adaptability. We focused on the climate adaptability of cities in the Pearl River Delta (PRD) in the southeastern China, and employed the entropy-weighting method and TOPSIS model to assess city's adaptability to climate in three levels, exposure, sensitivity, and adaptation. Then, we applied the Obstacle and Geodetector model to identify the challenges of the cities and elucidate the primary drivers of the changes in climate adaptability from 2000 to 2020. This study shows a significant increase in climate adaptation within the PRD region over the past two decades, especially for economy-prosperous cities such as Shenzhen and Guangzhou that show significant improvement. Spatially, central cities are more adaptable than western cities. The density of urban drainage pipes, doctors per 1000 people, and GDP per capita are the main obstacles. The explanatory power of the number of invention patents and fixed investments persists in surpassing that of the heat index and other factors. This interaction underscores the imperative for integrated strategies aimed at fostering both socio-economic development and climate adaptability. It emphasizes the need to tailor urban planning approaches to the specific characteristics of cities in different locations and stages of development, thereby enhancing their capacity to adapt to climate change. [ABSTRACT FROM AUTHOR]

Reservoir-type drinking water sources in the Pearl River Delta ensure a safe urban water supply; thus, land-use changes are important factors affecting these aquatic environments. In this study, we investigated the water source areas of medium and large reservoirs in the Pearl River Delta to determine the contributions and trends of land-use changes within reservoir drinking water source areas to the reservoir water quality. First, we analyzed dynamic land-use changes in reservoir-type water sources in the Pearl River Delta region from 1980 to 2020. We then used the gray relational analysis method to determine the relationship between land use and water quality changes. We analyzed changes in the main water quality factors in the Dajingshan Reservoir (Zhuhai) and determined the relationship between changes in land use and the reservoir water quality index over the past 20 years using correlation and redundancy analyses. The results indicate that paddy fields, dry land, forest land, and water areas were the main land-use types around reservoir-type drinking water sources in the Pearl River Delta. Although construction land and water areas expanded, paddy fields, dry land, and forest land areas decreased. The land transfer trend was mainly from forest and cultivated land to production and living land (e. g. 1980-2020), construction land) and water areas. With the implementation of the policy, the aforementioned land-use transformation began to slow. Regionally, the risk sources of non-point source pollution in the study area gradually decreased, but still accounted for 9.48% of total land use in 2020. The water quality of reservoir sources in the Pearl River Delta improved; however, nitrogen pollution remains problematic. Gray relational analysis indicates that land-use changes and water quality were correlated (in order of decreasing strength): construction land > agricultural land > forest land. Non-point source pollution caused by land use remains an important influencing factor. The Dajingshan Reservoir water quality is seriously polluted, as the total nitrogen exceeded the standard during several months, and nitrogen and phosphorus pollution gradually increased over time. Nitrogen and phosphorus were the main pollutants in the reservoir. Big mountain reservoir redundancy, correlation, and partial least squares regression analyses indicate that the land use type and water quality index were correlated, forest land and the nitrogen/phosphorus water quality index were negatively correlated, and construction and agricultural land were significantly positively correlated, which had a positive effect on the total nitrogen concentration. The influence of land-use patterns on non-point source pollution remains an uncontrollable factor. The specific effects of land-use changes on water quality are complex; therefore, further modeling should investigate the mechanism by which the water supply quality is influenced to improve reservoir water quality, ensure the safety of the regional water supply, and provide support for ecological restoration measures in protected areas. [ABSTRACT FROM AUTHOR]

Determining the chemical characteristics of atmospheric precipitation and its source contributions is critical for improving atmospheric environmental quality and water security. In this study, we analyzed the pH, Electrical Conductivity (EC), and major ion concentrations of precipitation from 2000 to 2021 at 29 monitoring stations in the Pearl River Delta (PRD), which typically experiences acid rain. Correlation analysis, the Positive Matrix Factorization (PMF) model, and other statistical methods were used to analyze the correlations between the major ion concentrations and their source contributions. The results indicate that the pH, EC, and Fractional Acidity (FA) of precipitation from 2000 to 2021 ranged from 4.66 ± 0.18 to 5.91 ± 0.45, from 1.63 ± 0.59 to 5.49 ± 1.62 mS/m, and from 0.05 ± 0.06 to 0.19 ± 0.13, respectively. The pH exhibited interannual variations (first decreasing and then increasing), whereas EC and FA exhibited the opposite trend. The total ion concentrations in precipitation ranged from 166.63 ± 46.56 to 631.48 ± 212.83 μeq/L, which first increased and then decreased. The weighted equivalent ion concentrations were in order of SO2 - 4 > Ca2+ > NH+ 4 > NO- 3 > Cl- > Na+ > K+ > Mg2+ > F-. SO2 - 4, NO- 3, Ca2+, and NH+ 4 were the main ions, accounting for 72.98% of the total concentration. The ratio of the SO2 - 4 concentration to the total concentration decreased from 32.71% in 2000 to 14.33% in 2021, whereas NO- 3 increased from 9.03% to 13.74% during the same period. The ratio of SO2 - 4 to NO- 3 concentrations (SO2 - 4 / NO- 3) decreased by 65.95% from 2000 to 2021. After 2008, the SO2 - 4/NO- 3 values ranged from 0.5 to 3, and precipitation shifted from a sulfuric acid type to a mixed sulfuric-nitric acid type. This change indicates that increased NOx emissions in the PRD under urbanization and agricultural intensification altered the structure of precipitation pollution and further increased the complexity of regional air pollution. The ions were highly significantly positively correlated, of which NO- 3 and SO2 - 4 had the strongest positive correlation (r=0.69‒0.74). Generally, NOx and SO2 are emitted together and enter precipitation via overlapping pathways. Of the six ion sources, coal combustion had the highest contribution rates (a>60%) to SO2 - 4 and F-, while secondary inorganic salts contributed 82.30% of the NO- 3. Agriculture, sea salt, biomass combustion, and dust contributed > 70% of the NH+ 4, Na+, K+, and Ca2+. The contribution rates of secondary inorganic salts to SO2 - 4, Cl-, and NH+ 4 were also greater than 25%. Owing to the increase in motor vehicles driven by urbanization, the impacts of secondary inorganic salt sources on ions in precipitation have become more extensive, and controlling NOx emissions to effectively control secondary pollution sources is urgently required. [ABSTRACT FROM AUTHOR]

China's environmental turn is diversifying the country's urbanisation trajectories. Previously abstracted and exploited as a vast land reserve for urban expansion, the countryside of China now captures the imagination of a growing crowd of green-loving urbanites with its ecological and cultural resources, propelling a new, environmentalised form of urbanisation. In the Pearl River Delta, the development of rural greenways has driven this urbanisation, in which rural lives and landscapes have evolved in response to their encounters with urban users of the greenways. Based on the late John Friedmann's multidimensional understanding of China's urbanisation, this paper unpacks four aspects of changes brought about by greenway-driven urbanisation in the Pearl River Delta's countryside since the 2010s, namely, economic diversification, institutional adaptation, physical reconfiguration, and sociocultural transformation. These changes underscore the need for research on China's urban-rural relations to pay more attention to the growing centrality of the environment in the politics and practices of urbanisation. [ABSTRACT FROM AUTHOR]

This paper revisits China's city-regionalism based on a multi-scalar reading of state entrepreneurialism, with a special focus on the transition from the Pearl River Delta (PRD) to the Greater Bay Area (GBA). We first propose a multi-scalar theoretical framework of state entrepreneurialism to comprehend China's city-regional development. At the national scale, the central state maintains planning centrality by establishing normative goals through national political mandates and orchestrating socio-spatial reconfiguration of city-regions using various planning techniques (e.g., zoning, annexation, connectivity, and place-making), which demonstrates state spatial selectivity. At the local scale, city-regional development, led by the local state, pivots on the mandates and resorts to market instruments. Place-specific contexts and development trajectories give rise to distinctive 'regional models' and contingent socio-spatial processes. From a historical-geographical perspective, these contingent socio-spatial processes represent both the outcome of and the precondition for successive waves of state spatial selectivity in city-regional development. Building upon the dynamic interplay between state spatial selectivity and contingent socio-spatial processes, we present a periodised analysis to delve into the ongoing transformation from the PRD to the GBA. Amidst evolving global-local conjunctures and shifting national political mandates, state spatial selectivity within the PRD-to-GBA transformation is categorised into three periods: (1) 1980s to early 1990s: exploiting zoning technologies to institutionalise exceptionality within delimited areas for undertaking market-oriented experiments; (2) mid-1990s to 2000s: empowering entrepreneurial cities to drive market-oriented development while managing their size, internal hierarchy, and external connections; and (3) 2010s onwards: an intensified planning centrality at the national scale and the reinvention of zoning technologies to emphasise relationality, reshaping the urban-regional and cross-border dynamics of the GBA within an 'integration' framework. In conclusion, this paper reflects on the variegated geographies of China's city-regionalism – the socio-spatially distinctive, temporally evolving and ultimately polymorphic, multi-scalar construction of Chinese city-regions. [ABSTRACT FROM AUTHOR]

Between 1958 and 1999, notable lithic localities recorded prehistoric activities in Xiqiao Town of Nanhai District, Foshan City, Guangdong Province, from which double-shouldered and microlith-stone artefacts were uncovered. Currently, the "Xiqiaoshan site" is recognized as a substantial Neolithic quarry and processing location, dating back to 4‒7 ka B P. Subsequently, from 2011 to 2022, we conducted multiple geological environmental surveys and analyses on Xiqiaoshan Mountain. A well-preserved Quaternary stratigraphic profile was discovered north of Fuxian village in the southeast foothills of Xiqiaoshan Mountain. The sedimentological, geochemical, and geochronological results indicate the presence of two primary sedimentary strata in the Fuxian locality. The upper unit comprises the Holocene swamp facies, with a calibrated AMS14C dating range from 5052‒5409 a B P; whereas, the lower unit comprises the late Pleistocene alluvial-diluvial strata, with a calibrated AMS14C dating range from 38420‒40502 a B P, and an optically stimulated luminescence (OSL) dating range of 41.977‒43.796 ka B P. Late Pleistocene strata yielded two sand-gravel layers containing Paleolithic artefacts, which are marked as layers A1 and A2. The predominant artefacts in lower layer A1 include larger scrapers, pointed tools, tongue-shaped edged tools, and small flake tools, such as various scrapers, denticulates, notches, knives, utilized flakes, and cores, including tanged axe-shaped knives. In the upper layer A2, backed or tanged knives appear more frequently. The other small flake tools from this layer (A2) were not significantly different from those in lower layer A1. One bifacially prepared core for producing small elongated flakes is of particular interest for this artefact. Based on the average deposition rate, the computational age of the A1 layer was 46.511‒47.325 ka B P, whereas that of the A2 layer was 41.977‒42.167 ka B P. Although the number of artefacts within the Holocene sediments (>5 ka B P) overlying the late Pleistocene strata is limited, the characteristics of inheritance and development are still evident in the types of artefacts. The discovery presented in this study has completely updated and extended the connotation of Xiqiaoshan National Geopark and "Xiqiaoshan culture,"breaking through the late Pleistocene Paleolithic remains records with exact dating in the Pearl River Delta region for the first time. Therefore, a ground-breaking discovery can accurately trace the footsteps of modern humans in the coastal areas of South China from 40‒50 ka. It also reveals the rich features of lithic industry and the developmental characteristics and evolution of its cultural connotations during this period. The present study shows that during the relatively warm and humid conditions of marine isotope stages 3 (MIS3) interglacial period and the subsequent cold and arid stage of MIS2, human population in the Fuxian locality encountered environmental challenges and adopted new subsistence strategy, which is of great significance for understanding modern human responses and adaptations to global and regional environmental and climate change.

Determining the chemical characteristics of atmospheric precipitation and its source contributions is critical for improving atmospheric environmental quality and water security. In this study, we analyzed the pH, Electrical Conductivity (EC), and major ion concentrations of precipitation from 2000 to 2021 at 29 monitoring stations in the Pearl River Delta (PRD), which typically experiences acid rain. Correlation analysis, the Positive Matrix Factorization (PMF) model, and other statistical methods were used to analyze the correlations between the major ion concentrations and their source contributions. The results indicate that the pH, EC, and Fractional Acidity (FA) of precipitation from 2000 to 2021 ranged from 4.66 ± 0.18 to 5.91 ± 0.45, from 1.63 ± 0.59 to 5.49 ± 1.62 mS/m, and from 0.05 ± 0.06 to 0.19 ± 0.13, respectively. The pH exhibited interannual variations (first decreasing and then increasing), whereas EC and FA exhibited the opposite trend. The total ion concentrations in precipitation ranged from 166.63 ± 46.56 to 631.48 ± 212.83 μeq/L, which first increased and then decreased. The weighted equivalent ion concentrations were in order of SO42- > Ca2+ > NH4+ > NO3- > Cl- > Na+ > K+ > Mg2+ > F-. SO42-, NO3-, Ca2+, and NH4+ were the main ions, accounting for 72.98% of the total concentration. The ratio of the SO42- concentration to the total concentration decreased from 32.71% in 2000 to 14.33% in 2021, whereas NO3- increased from 9.03% to 13.74% during the same period. The ratio of SO42- to NO3- concentrations (SO42-/NO3-) decreased by 65.95% from 2000 to 2021. After 2008, the SO42-/NO3- values ranged from 0.5 to 3, and precipitation shifted from a sulfuric acid type to a mixed sulfuric-nitric acid type. This change indicates that increased NOx emissions in the PRD under urbanization and agricultural intensification altered the structure of precipitation pollution and further increased the complexity of regional air pollution. The ions were highly significantly positively correlated, of which NO3- and SO42- had the strongest positive correlation (r=0.69‒0.74). Generally, NOx and SO2 are emitted together and enter precipitation via overlapping pathways. Of the six ion sources, coal combustion had the highest contribution rates (a>60%) to SO42- and F-, while secondary inorganic salts contributed 82.30% of the NO3-. Agriculture, sea salt, biomass combustion, and dust contributed > 70% of the NH4+, Na+, K+, and Ca2+. The contribution rates of secondary inorganic salts to SO42-, Cl-, and NH4+ were also greater than 25%. Owing to the increase in motor vehicles driven by urbanization, the impacts of secondary inorganic salt sources on ions in precipitation have become more extensive, and controlling NOx emissions to effectively control secondary pollution sources is urgently required.

Reservoir-type drinking water sources in the Pearl River Delta ensure a safe urban water supply; thus, land-use changes are important factors affecting these aquatic environments. In this study, we investigated the water source areas of medium and large reservoirs in the Pearl River Delta to determine the contributions and trends of land-use changes within reservoir drinking water source areas to the reservoir water quality. First, we analyzed dynamic land-use changes in reservoir-type water sources in the Pearl River Delta region from 1980 to 2020. We then used the gray relational analysis method to determine the relationship between land use and water quality changes. We analyzed changes in the main water quality factors in the Dajingshan Reservoir (Zhuhai) and determined the relationship between changes in land use and the reservoir water quality index over the past 20 years using correlation and redundancy analyses. The results indicate that paddy fields, dry land, forest land, and water areas were the main land-use types around reservoir-type drinking water sources in the Pearl River Delta. Although construction land and water areas expanded, paddy fields, dry land, and forest land areas decreased. The land transfer trend was mainly from forest and cultivated land to production and living land (e.g.1980-2020), construction land) and water areas. With the implementation of the policy, the aforementioned land-use transformation began to slow. Regionally, the risk sources of non-point source pollution in the study area gradually decreased, but still accounted for 9.48% of total land use in 2020. The water quality of reservoir sources in the Pearl River Delta improved; however, nitrogen pollution remains problematic. Gray relational analysis indicates that land-use changes and water quality were correlated (in order of decreasing strength): construction land > agricultural land > forest land. Non-point source pollution caused by land use remains an important influencing factor. The Dajingshan Reservoir water quality is seriously polluted, as the total nitrogen exceeded the standard during several months, and nitrogen and phosphorus pollution gradually increased over time. Nitrogen and phosphorus were the main pollutants in the reservoir. Big mountain reservoir redundancy, correlation, and partial least squares regression analyses indicate that the land use type and water quality index were correlated, forest land and the nitrogen/phosphorus water quality index were negatively correlated, and construction and agricultural land were significantly positively correlated, which had a positive effect on the total nitrogen concentration. The influence of land-use patterns on non-point source pollution remains an uncontrollable factor. The specific effects of land-use changes on water quality are complex; therefore, further modeling should investigate the mechanism by which the water supply quality is influenced to improve reservoir water quality, ensure the safety of the regional water supply, and provide support for ecological restoration measures in protected areas.

During the stage of high-quality development, the orderly promotion of citizenization of the floating population is crucial to ensure the high-quality population development and sustainable socio-economic growth of our country. In this study, dynamic monitoring survey data of China's floating population in 2017 were referenced to categorize the settlement intentions of this population group into three types (viz., short term, long term, and permanent) according to their expected residence duration. Subsequently, the mobility and residential characteristics of this population were analyzed by using a multinomial logistic regression model to examine differences in their demographic and family characteristics, mobility patterns, economic status, and social integration. The findings are as follows: (1) Dongguan and Huizhou, located on the east bank of the Pearl River and primarily driven by manufacturing industries, have a significant proportion of populations with short-term settlement intentions. By contrast, cities with lower living costs or more comprehensive services are more likely to attract long-term residents. (2) The inter-provincial floating population tends to flow into Shenzhen, with individuals migrating a short distance being more predominant. Long-distance inter-provincial migrants have a stronger intention to settle permanently. Within the province, the floating population tends to flow into Guangzhou, displaying a certain degree of geographical proximity in city choices and a tendency to stay long term or permanently. (3) Groups characterized by female sex, older age, higher educational level, marital status, longer inflow time, non-work-related inflow reasons, and higher income level tend to take up long-term or permanent residence at their destination. Conversely, lower levels of these characteristics are associated with shorter stays. Higher degrees of social integration can promote permanent settlement intentions among inter-provincial migrants compared with the effect on their intra-provincial counterparts. (4) Each factor has different effects on groups with the same settlement intention within and outside the province, as reflected in the varying impacts of educational level, marital status, income level, and migration reasons on inter- and intra-provincial floating populations. This study breaks through the traditional binary division model of settlement intentions, enhancing our understanding of floating populations through the "short-term residence–long-term residence–permanent settlement" categorization method. The Pearl River Delta region, one of the areas with the largest concentration of the floating population and the highest degree of economic development in China, serves as a critical case study. Understanding the flow and residence patterns of this population in this region will help government departments implement relevant policies and safeguarding measures tailored to different settlement intentions, thereby improving urban operational efficiency.

During the stage of high-quality development, the orderly promotion of citizenization of the floating population is crucial to ensure the high-quality population development and sustainable socio-economic growth of our country. In this study, dynamic monitoring survey data of China's floating population in 2017 were referenced to categorize the settlement intentions of this population group into three types (viz., short term, long term, and permanent) according to their expected residence duration. Subsequently, the mobility and residential characteristics of this population were analyzed by using a multinomial logistic regression model to examine differences in their demographic and family characteristics, mobility patterns, economic status, and social integration. The findings are as follows: (1) Dongguan and Huizhou, located on the east bank of the Pearl River and primarily driven by manufacturing industries, have a significant proportion of populations with short-term settlement intentions. By contrast, cities with lower living costs or more comprehensive services are more likely to attract long-term residents. (2) The inter-provincial floating population tends to flow into Shenzhen, with individuals migrating a short distance being more predominant. Long-distance inter-provincial migrants have a stronger intention to settle permanently. Within the province, the floating population tends to flow into Guangzhou, displaying a certain degree of geographical proximity in city choices and a tendency to stay long term or permanently. (3) Groups characterized by female sex, older age, higher educational level, marital status, longer inflow time, non-work-related inflow reasons, and higher income level tend to take up long-term or permanent residence at their destination. Conversely, lower levels of these characteristics are associated with shorter stays. Higher degrees of social integration can promote permanent settlement intentions among interprovincial migrants compared with the effect on their intra-provincial counterparts. (4) Each factor has different effects on groups with the same settlement intention within and outside the province, as reflected in the varying impacts of educational level, marital status, income level, and migration reasons on inter- and intra-provincial floating populations. This study breaks through the traditional binary division model of settlement intentions, enhancing our understanding of floating populations through the "short-term residence–long-term residence– permanent settlement" categorization method. The Pearl River Delta region, one of the areas with the largest concentration of the floating population and the highest degree of economic development in China, serves as a critical case study. Understanding the flow and residence patterns of this population in this region will help government departments implement relevant policies and safeguarding measures tailored to different settlement intentions, thereby improving urban operational efficiency. [ABSTRACT FROM AUTHOR]

Cellular automata (CA) models have been extensively employed to predict and understand the spatiotemporal dynamics of land use. Driving factors play a significant role in shaping and driving land-use changes. Mining land-use transition rules from driving factors and quantifying the contribution of driving factors to land-use dynamics are fundamental aspects of CA simulation. However, existing CA models have limitations in obtaining accurate transition rules and reliable interpretations simultaneously for multiple land-use simulations. In this study, we constructed a CA model based on a tree-based deep learning algorithm, deep cascade forest (DCF), to improve multiple land-use simulations and driving factors analysis. The DCF algorithm was utilized to mine accurate multiple land-use transition rules without overfitting to improve CA simulation accuracy. Additionally, a novel ensemble mean decrease of impurity (MDI) factor importance analysis method (DCF-MDI), which leverages the cascade structure of the DCF model, was proposed to qualify the contribution of each driving factor to land-use dynamics stably and efficiently. To evaluate the effectiveness of the proposed DCF-CA, we applied the model to simulate land-use distributions and explore the driving mechanisms of land-use dynamics in the Pearl River Delta (PRD), China, from 2000 to 2010. Compared to existing models, the proposed DCF-CA model exhibits the highest accuracy (FoM = 23.79%, PA = 39.77%, UA = 36.35%, OA = 91.50%), which demonstrates its superiority in mining accurate transition rules for capturing multiple land-use dynamics. Factor importance analysis reveals that the proposed DCF-MDI method yields more stable ranking orders and lower standard deviation of contribution weights (<0.10%) compared to the traditional method, indicating its robustness to random disturbances and effectiveness in elucidating the driving mechanisms of land-use dynamics. The DCF-CA model proposed in this study, demonstrating high simulation accuracy and reliable interpretability simultaneously, can provide substantial support for sustainable land use management. [ABSTRACT FROM AUTHOR]

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Rotifers are essential invertebrates in freshwater ecosystems. Rotifer community structure reflects the environmental changes. To assess the diversity of rotifers in the Pearl River Delta, we investigated the rotifer community structure in different water bodies types using morphology and DNA metabarcoding. A total of 101 species in 30 genera were recorded. 82 rotifer species were identified by morphology and 31 by OTUs based on DNA metabarcoding. Only 40% (2 orders), 42.9% (9 families), 29.7% (11 genera), and 4% (4 species) were shared by the two identification methods. Primers and imperfect rotifer databases might be responsible for the low annotation of rotifer OTU species. The community structure of rotifer morphospecies and OTUs in the Pearl River Delta changed with seasonal and spatial distribution. Heatmaps showed that different rotifer species responded differently to environmental factors. Our results show that DNA metabarcoding provides complementary rather than identical estimates compared to traditional approaches for rotifers. However, if widely validated and improved, this approach could be a useful alternative for practical applications of rotifers as bioindicators. In the future, environmental DNA metabarcoding is promising for the large-scale study and assessment of rotifer diversity. [ABSTRACT FROM AUTHOR]

Knowledge on natural background levels (NBLs) of aluminum (Al) in groundwater can accurately assess groundwater Al contamination at a regional scale. However, it has received little attention. This study used a combination of preselection and statistic methods consisting of the oxidation capacity and the boxplot iteration methods to evaluate the NBL of shallow groundwater Al in four groundwater units of the Pearl River Delta (PRD) via eliminating anthropogenic‐impacted groundwaters and to discuss driving factors controlling high NBLs of Al in groundwater in this area. A total of 280 water samples were collected, and 18 physico‐chemical parameters including Redox potential, dissolved oxygen, pH, total dissolved solids, HCO3−, NH4+, NO3−, SO42−, Cl−, NO2−, F−, K+, Na+, Ca2+, Mg2+, Fe, Mn, and Al were analyzed. Results showed that groundwater Al NBLs in groundwater units A‐D were 0.11, 0.16, 0.15, and 0.08 mg/L, respectively. The used method in this study is acceptable for the assessment of groundwater Al NBLs in the PRD, because groundwater Al concentrations in various groundwater units in residual datasets were independent of land‐use types, but they were opposite in the original datasets. The dissolution of Al‐rich minerals in sediments/rocks was the major source for groundwater Al NBLs in the PRD, and the interaction with Al‐rich river water was secondary one. The high groundwater Al NBL in groundwater unit B was mainly attributed to the acid precipitation and the organic matter mineralization inducing the release of Al in Quaternary sediments. By contrast, the high groundwater Al NBL in groundwater unit C mainly was ascribed to the release of Al complexes such as fluoroaluminate from rocks/soils into groundwater induced by acid precipitation, but it was limited by the dissolution of Mg minerals (e.g., dolomite) in aquifers. This study provides not only useful groundwater Al NBLs for the evaluation of groundwater Al contamination but also a reference for understanding the natural geochemical factors controlling groundwater Al in urbanized deltas such as the PRD. Practitioner Points: The natural background level (NBL) of groundwater aluminum in the Pearl River Delta (PRD) was evaluated.The dissolution of aluminum‐rich minerals in sediments/rocks was the major source for groundwater aluminum NBLs in the PRD.The acid precipitation and organic matter mineralization contribute to high groundwater Al NBL in the groundwater unit B.The acid precipitation contributes to high groundwater Al NBL in the groundwater unit C, while dissolution of magnesium minerals limits it. [ABSTRACT FROM AUTHOR]

This anonymized Research Note reports qualitative observations and interview evidence to explore the operation of a U-pick lychee orchard located in China’s Pearl River Delta. Observation reveals the ironic juxtaposition of an owner-built cottage on a forested hillside surrounded by an intensively planned, densely populated urban environment featuring high-rise apartment towers. Field data show that informality, social networks, and petty entrepreneurialism are all manifest in urban agriculture, lychee production, labor, and land tenure. This Research Note illustrates the interstitial porosity that exists within the incorporated bounds of an urban area with informal economic activity adjacent to formal occupations and hillside orchards in the shadows of high-rise apartment towers. [ABSTRACT FROM AUTHOR]

With increasing air and sea temperatures, the thermodynamic environments over the oceans are becoming more favourable for the development of intense tropical cyclones (TCs) with rapid intensification (RI). The South China coastal region consists of highly densely populated cities, especially over the Pearl River Delta (PRD) region. Intense TCs maintaining their strength or the RI of TCs close to the coastal region can present substantial forecasting challenges and have significant potential impacts on the coastal population. This study investigates the effect of sea-surface and sub-surface temperatures and salinity on the intensification of five TCs, namely Super Typhoon Hato in 2017, Super Typhoon Mangkhut in 2018, and Typhoon Talim, Super Typhoon Saola, and Severe Typhoon Koinu in 2023, which have significantly affected the South China coastal region and triggered high TC warning signals in Hong Kong in the past few years. This analysis utilised the Hong Kong Observatory's TC best-track and intensity data, along with sea temperature and salinity profiles generated using the China Ocean ReAnalysis version 2 (CORA2) product from the National Marine Data and Information Service of China. It was found that high sea-surface temperatures (SST) of 30 °C or above for a depth of about 20 m, low sea-surface salinity (SSS) levels of 33.8 psu or below for a depth of at least 20 m, and strong salinity stratification of at least 0.6 psu per 100 m depth might offer useful hints for predicting the RI of TCs over the western North Pacific and the South China Sea (SCS) in operational forecasting, while noting other contributing environmental factors and synoptic flow patterns conducive to RI. This study represents the first documentation of sub-surface salinity's impact on some intense TCs traversing the SCS during 2017–2023 based on an observational study. Our aim is to supplement operational techniques for forecasting RI with some quantitative guidance based on upper-level ocean observations of temperatures and salinity, on top of well-known but more rapidly changing dynamical factors like low-level convergence, weak vertical wind shear, and upper-level divergent outflow, as forecasted with numerical weather prediction models. This study will also encourage further research to refine the analysis of quantitative contributions from different RI factors and the identification of essential features for developing AI models as one way to improve the forecasting of TC RI before the TC makes landfall near the PRD, with due consideration given to the effect of freshwater river discharge from the Pearl River. [ABSTRACT FROM AUTHOR]

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The Pearl River Delta (PRD) has undergone rapid urbanization over the past three decades, leading to significant changes in urban flood risk and resilience. This study addresses the critical need to understand evolution trend of urban flood risk and resilience in the PRD for both pre-urbanization (1990) and post-urbanization (2020) periods. Using 12 indices integrated within the different frameworks, the spatial and temporal evolution of risk and resilience over the past 30 years are analyze. Six new evaluative indicators are introduced to capture spatial characteristics and their evolutionary trends more accurately. Findings reveal the spatial distribution of urban flood risk and resilience. And the results further indicate that high-risk and low-resilience areas have expanded, become more interconnected, and exhibited increased fragmentation and complexity, while spatial aggregation has decreased. High-risk areas particularly show a trend of spreading southward, whereas low-resilience areas have remained relatively stable. Strategies involving green infrastructure to reduce the interconnection of flood risk patches, urban planning to limit the expansion of risk regions, and adaptive management to handle the complexity of flood-prone areas are proposed. This study provides insights into the spatiotemporal evolution of flood risk and resilience, offering valuable guidance for urban planners and policymakers.

The transfers of potential toxic elements (PTEs) from root soil to rice grains and its driving factors are of major worldwide concern. And it is still not clear whether the parent material has influence on the transfers of PTEs in soil. Thus, the aim of this study is to investigate the transfers of PTEs in soil‐rice system from different parent materials area, identify its driving factors and evaluate human health risk. 157 sets of root soil and rice grains samples collected from the areas with quaternary sediments, acidic magmatic rocks and terrigenous clastic rocks in the Pearl River Delta, China. Pearson correlation analysis, discriminant analysis, redundancy analysis, path analysis and human health risk model were utilized for data processing and analysis. The results reveal that parent materials play a primary role affecting the transfers of PTEs in soil‐rice system, and its influence on transfers of PTEs is achieved by governing physicochemical properties of soil. And physicochemical parameters like MgO, SiO2, Al2O3, TFe2O3, and organic matter (OM) exerted significant influence on transfers of PTEs. The influences of some physicochemical parameters on the transfers of PTEs are most significantly in the area of quaternary sediments. The values of the total non‐carcinogenic and the total carcinogenic risks for children and adults caused by rice consumption are much higher than the corresponding risk limits, and the main contributing elements are Pb, As, and As, Cd, respectively. The human health risks caused by rice consumption are greatest in the area with quaternary sediments. [ABSTRACT FROM AUTHOR]

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Objective To evalute the drug resistance characteristics of tuberculosis(TB) patients of all ages in Guangdong Province during 2014-2020, and provide prevention and treatment strategies of tuberculosis. Method We used 39, 048 clinical isolates of Mycobacterium tuberculosis (MTB) belonging to patients with confirmed TB from 2014 to 2020, from 32 TB drug-resistant surveillance sites in Guangdong Province, and we retrospectively analyzed the laboratories data of patients with drug-resistant TB, and grouped patients by age and region, to explore the trend of drug-resistance of MTB clinical isolates, the trend and incidence differences of multi-resistant TB (including monodrug-resistant TB (MR-TB), polydrug-resistant TB (PDR-TB), multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB)), and resistance characteristics of MTB clinical isolates to drugs in focus (rifampicin and ofloxacin). Result The differences in the resistance rates of MTB clinical isolates to nine antituberculosis drugs among patients at 32 TB drug resistance surveillance sites in Guangdong Province from 2014 to 2020 were not statistically significant (P > 0.05). The rates of MR-TB, PDR-TB, MDR-TB, XDR-TB, and total resistance isolates of MTB clinical isolates were 14.46%, 5.16%, 5.16%, 4.58%, and 1.29%, respectively. he pediatric group had a higher MR rate (15.4%) than the adult and geriatric groups, while the adult and geriatric groups had higher MDR rates (5.0% and 5.0%, respectively). The geriatric group also had a higher XDR rate (2.1%), with statistically significant differences (P < 0.001). The rates of MR-TB (14.8%), PDR-TB (5.3%), MDR-TB (4.7%), XDR-TB (1.4%), ofloxacin resistance (11.33%) and rifampicin resistance (6.92%) of MTB clinical isolates were higher in patients from the Pearl River Delta than in other regions of Guangdong Province, with statistically significant differences (P < 0.001). Conclusion According to the data from the surveillance sites, the epidemiological trend of drugresistant TB in Guangdong Province is leveling off during the period 2014-2020. However, the incidence of drug-resistant TB is higher in specific populations (e.g. children and the elderly), and the incidence of drug-resistant TB and the rate of drug resistance to drugs in focus are higher in the Pearl River Delta than in other regions of Guangdong Province, necessitating further investigation and the development of novel prevention and control strategies. [ABSTRACT FROM AUTHOR]

• The seasonal difference of ozone distribution in the inland and coastal areas is significant in the PRD. • The ozone pollution is expanding from the center to southwest in the PRD and spreading from autumn to winter and spring time. • The increasing duration of continuous ozone pollution in some cities raises a great challenge for further mitigation. Surface ozone (O 3) is a major air pollutant and draw increasing attention in the Pearl River Delta (PRD), China. Here, we characterize the spatial-temporal variability of ozone based on a dataset obtained from 57 national monitoring sites during 2013-2019. Our results show that: (1) the seasonal difference of ozone distribution in the inland and coastal areas was significant, which was largely affected by the wind pattern reversals related to the East Asian monsoon, and local ozone production and destruction; (2) the daily maximum 8hr average (MDA8 O 3) showed an overall upward trend by 1.11 ppbv/year. While the trends in the nine cities varied differently by ranging from -0.12 to 2.51 ppbv/year. The hot spots of ozone were spreading to southwestern areas from the central areas since 2016. And ozone is becoming a year-round air pollution problem with the pollution season extending to winter and spring in PRD region. (3) at the central and southwestern PRD cities, the percentage of exceedance days from the continuous type (defined as ≥3 days) was increasing. Furthermore, the ozone concentration of continuous type was much higher than that of scattered exceedance type (<3 days). In addition, although the occurrence of continuous type starts to decline since 2017, the total number of exceedance days during the continuous type is increasing. These results indicate that it is more difficult to eliminate the continuous exceedance than the scatter pollution days and highlight the great challenge in mitigation of O 3 pollution in these cities. [ABSTRACT FROM AUTHOR]

Global warming is a global issue closely linked to sustainability, and power systems around the world are facing immense pressure due to global warming. The purpose of this study is to investigate the impact of global warming on non-industrial electricity consumption in China's Pearl River Delta. The Weather Research and Forecasting (WRF) model is employed to dynamically downscale and simulate summer climate change characteristics during historical periods and future warming scenarios of 1.5/2 °C. Then, in order to dynamically investigate the changes in non-industrial electricity consumption in cities after warming, we developed a non-industrial electricity consumption estimation model based on degree days and GDP. The regression model can well reproduce non-industrial electricity consumption in summer. Under future warming scenarios of 1.5/2 °C, the results indicate an annual growth trend in non-industrial electricity consumption due to global warming. Under a 1.5 °C warming scenario, non-industrial electricity consumption in both Guangzhou and Zhuhai increases, with Guangzhou experiencing a larger increase of about 10 terawatt-hours (TWh) compared to the historical period. However, under a 2 °C warming scenario, non-industrial electricity consumption in both cities slightly decreases compared to the 1.5 °C warming scenario, with a maximum decrease of 874 million kilowatt-hours. [ABSTRACT FROM AUTHOR]

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[Objective] The driving forces of the spatial distribution and spato-temporal changes in fractional vegetation coverage (FVC) in the Pearl River delta were analyzed in order to provide a scientific reference for the protection of the ecological environment in the region. [Methods] A binary pixel model was used with Landsat 5 TM and Landsat 8 OLI data to invert the vegetation coverage of the Pearl River delta in 2000, 2005, 2010, 2015, and 2020. The spatial pattern and spatio-temporal changes in FVC in the Pearl River delta were analyzed. Annual precipitation, average annual temperature, population density, and land use data during the five study periods were analyzed using correlation coefficients and the geographical detector method. [Results] ① Vegetation coverage in the Pearl River delta was lower in the middle of the region and higher in the marginal regions. Vegetation coverage was lower in Foshan, Zhongshan, Zhuhai, Southwestern Guangzhou, Dongguan City, and Shenzhen City, and higher in Zhaoqing, Jiangmen City, and Huizhou City. Overall, vegetation coverage increased over time, with 64.99% of the total area showing increases in vegetation coverage. There were stage differences in time, and the area with highest vegetation coverage (more than 80%) increased most significantly during 2010—2015. ② There were obvious regional differences in the driving factors of FVC. Annual precipitation and land use had more inhibiting effects than promoting effects, and average annual temperature and population density had more promoting effects than inhibiting effects. ③ The spatial pattern factor detection of FVC showed that the explanatory power of land use degree was the strongest, while the interactive detection showed that the explanatory power of annual average temperature and land use degree interaction was the highest. For the explanatory power of annual precipitation, annual precipitation and annual temperature interaction showed a weakening trend in the time series of 2000, 2005, 2010, 2015, and 2020. The explanatory power of other influencing factors and their interactions showed an increasing trend. The spatial-temporal FVC change factor detection also indicated that the explanatory power of land use degree change was the strongest, while the interactive detection indicated that annual precipitation change and land use degree interaction had the highest explanatory power. [Conclusion] Land use degree was the dominant factor affecting the temporal and spatial changes of vegetation coverage in the Pearl River delta. Human influence continues to increase, and the interaction of the two factors is significantly greater than the effect of a single factor.

The international non-tariff trade protection against China has gradually increased since 2018, hindering technology trade. Under the impact of the new trade protection, we still know little about how the electronic communication industry (as one of the strategic high-tech industries)changes the innovation cooperation relationship and the innovation performance. Owing to the failure of geographical research to integrate trade protection into the existing research framework from an institutional perspective, the trade protection literature and the innovation geography literature do not intersect. However, the trade geography literature has not paid enough attention to the evolution of industrial innovation in China in recent years and has not taken into account the heterogeneity of the industry-college-institute cooperation and innovation relationship and its impact on regional industrial innovation performance. Based on the 2014-2021 US Export Control Regulations and the invention patent data of the electronic communication industry in the Pearl River Delta, this study uses descriptive statistics, a Quadratic Assignment Procedure, and a negative binomial regression model. It explores both the mechanism and effect of a new round of trade protection on industry-college-institute cooperation and their joint impact on cooperative innovation performance. The study finds that the structure of the industry-college-institute cooperative innovation relationship in the electronic communication industry of the Pearl River Delta has gradually decentralized, and its heterogeneity growth tends to stall. The new round of trade protection significantly regulates geographical proximity, deteriorating the geographical scale of cooperative innovation. The regression results show that under the impact of trade protection, the heterogeneity of industry-college-institute cooperation changes from positive to negative, and the inverted U-shaped relationship has reached a significant level. Trade protection changes the influence of social and cognitive proximities and of geographical proximity on cooperative innovation performance, and the moderating effect of trade protection is highlighted by the positive effect of strengthening geographical proximity on industry-college-institute cooperation and innovation performance. The above findings remind us of the need to further refine and optimize innovation support policies. Therefore, the study puts forward some targeted policy suggestions, namely, to formulate innovation support policies suitable for the internal and externalized innovation transaction costs of different types of enterprises, strengthen the dominant role of enterprises in innovation, and promote cross-regional cooperation. To a certain extent, it can inform the decision-making by China's regional strategic industries around ending the international technology trade blockade and achieving high-quality independent innovation and technical cooperation.

The advancement of urbanization has led to a decline in the ecological function and environmental quality of cities, seriously reducing the services and sustainable development capacity of urban ecosystems. The construction of the National Forest Urban Agglomeration of China is conducive to alleviating the ecological and environmental problems brought about by rapid urbanization and promoting sustainable urban development. A time series analysis of ecological network changes can quickly and effectively explore the development and changes of ecological spatial patterns over time. Identifying ecological protection and restoration areas in urban agglomerations is an important way to promote ecosystem restoration and optimize ecological networks. This paper takes the Pearl River Delta forest urban agglomeration as the research area, uses multi-source remote sensing data from 2000 to 2020 (every 5 years), identifies ecological sources based on the morphological spatial pattern analysis (MSPA) method, generates ecological corridors based on the minimum cumulative resistance (MCR) model, constructs a time series ecological network pattern in the Pearl River Delta region, and analyzes the evolution process of the ecological network pattern over time. The results indicate that over time, the core green area in the ecological network pattern of the Pearl River Delta first decreased and then increased, and the complexity of ecological corridors first decreased and then increased. The main reason is that the urbanization process in the early 21st century led to severe ecological fragmentation. Under the promotion of the national forest urban agglomeration construction, the ecological network pattern of the Pearl River Delta was restored in 2015 and 2020. The time series analysis of the ecological network pattern in the Pearl River Delta region of this research confirms the effectiveness of the construction of forest urban agglomerations, providing a scientific reference for the identification of ecological networks and optimization of spatial patterns in forest urban agglomerations.

Severe salt intrusion has occurred in Peal River Estuary in recent years. It deteriorates water supply quality in the surrounding regions. Rapid and accurate prediction of salt intrusion length is of great significance for optimizing the layout of water intake in river sections. The theoretical relationship between salt intrusion length and runoff was inquired based on the salt conservation equation. And the hydrodynamic-salinity model was established to analyze the response characteristics of salt intrusion to runoff. Then the response model of salt intrusion length and runoff in Modaomen was proposed. Different semi-empirical models are contrasted under the same hydrological conditions to investigate the applicability in the Modaomen estuary. The results show that the salinity boundary presents an S-shaped distribution under different flow combinations. The salt intrusion length L and the upstream runoff Q present a power-exponent function relationship in theory. It is available to predict the salt intrusion length by using semi-empirical models. The conclusion shows that Savenije model and L-Q model perform well, the variation of the real landform and the characteristics of power are taken into account in the model. Moreover, the models are of high efficiency and accuracy, and can be used as a rapid assessment tool in salinity disaster of Modaomen estuary. [ABSTRACT FROM AUTHOR]

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Urban agglomerations are becoming increasingly important in driving economic development in China. Accurate representation of the economic development status and spillover effects of cities within an urban agglomeration is the foundation of and an effective approach for promoting the coordinated development of that agglomeration. However, current studies of economic spillovers tend to focus on urban agglomerations as a whole, and there is a lack of scrutiny and validation of research data. Therefore, this study proposes a framework for detecting economic spillover effects within an urban agglomeration based on a prolonged night-time light dataset. Firstly, we explored the most suitable night-time light index to characterize the economic status. Then, we used this index to construct the economic network and hierarchical structure of the urban agglomeration. Finally, we explored the heterogeneity of spillover effects under the hierarchical structure. The results of a case study in the Pearl River Delta (PRD) urban agglomeration show that (1) the total night-time light in built-up areas (BNTL) has the highest Pearson correlation coefficient with GDP, which is 0.82; (2) there is an obvious hierarchical structure within the PRD; (3) there are significant and sustained economic spillover effects among the core cities, with Guangzhou–Foshan and Shenzhen–Dongguan having more obvious spillover effects; and (4) the economic spillover effects within the three metropolitan areas have different characteristics. The Guangzhou–Foshan–Zhaoqing metropolitan area is closely linked, to apparent differences in the pace of spillover effects. The Shenzhen–Dongguan–Huizhou metropolitan area has strong close linkages, with strong synchronization of spillover effects. The Zhuhai–Zhongshan–Jiangmen metropolitan area has not yet formed a stable synergistic development relationship. Overall, the framework can effectively reveal the hierarchical structure and different characteristics of economic spillovers within urban agglomerations, which can provide a scientific reference for policy making related to the coordinated development of such agglomerations. [ABSTRACT FROM AUTHOR]

[Objective] The aim of this study is to explore the spatial structure pattern and spatial-temporal change rule of land use ecological risk in the Pearl River Delta (PRD) region, and then to provide scientific support for the sustainable utilization of land resources and ecological security. [Methods] A land-use ecological risk assessment model was constructed with landscape metrics, and land-use ecological risk indexes at multiple scales in the Pearl River Delta in 2000, 2010 and 2020 were measured by this model. Then, the semi-variogram, spatial autocorrelation and GIS spatial analysis methods were used to determine appropriate research scales and explore the spatiotemporal characteristics of land-use ecological risk at these scales. [Results] (1) The 3 km quadratic scale was the best research scale, and the small watershed scale was also appropriate. At both scales, the spatial variability of land-use ecological risk from 2000 to 2010 was mainly influenced by structural factors, i.e., there was a strong spatial autocorrelation. (2) The land-use ecological risk in the study area generally had strong positive spatial agglomeration characteristics, but the degree of agglomeration trended to weaken. The local spatial agglomeration characteristics of most units were relatively stable. The distribution of high-high agglomeration and low-low agglomeration areas were obvious, and the distribution of low-high agglomeration and high-low agglomeration areas were sporadic and did not change much. (3) The degree of land-use ecological risk had gradually decreased. Low-risk level and lower-risk level were dominant risks and the distribution areas were increasing, while the areas above medium-risk level were decreasing. [Conclusion] The overall land use ecological risk in the PRD region showed positive spatial clustering characteristics, and the level of land use ecological risk gradually decreased, and the results of this study can provide decision-making reference for the optimal use of regional land space and ecological risk control. [ABSTRACT FROM AUTHOR]

Using the daily ground temperature and air temperature data from 30 meteorological stations in northern Guangdong and the Pearl River Delta from 1970 to 2021, the present study analyzed the spatial distribution, seasonal changes, and interannual changes of ground-air temperature difference (surface temperature minus air temperature) under the background of climate change. The results show that: (1) The annual average ground-air temperature difference between northern Guangdong and the Pearl River Delta in the past 50 years is between 1.97 and 3.21 °C, showing a zonal distribution pattern with higher temperature in the north and lower temperature in the south. (2) The maximum ground-air temperature difference is 3.25 °C in summer and the minimum is 1.71 °C in winter. The temperature difference in the Pearl River Delta in winter is larger than that in northern Guangdong, while in summer it is the opposite. (3) Dongguan in the Pearl River Delta is the city with the most obvious downward trend in winter and summer, with decline rates of 0.35 °C/(10 a) and 0.66 °C/(10 a), respectively. By contrast, the most obvious increase is found in Zengcheng in the Pearl River Delta and Renhua in northern Guangdong, with increase rates of 0.30 °C/(10 a) and 0.32 °C/(10 a), respectively. (4) In the past 50 years, the annual average ground-air temperature difference between northern Guangdong and the Pearl River Delta has shown an insignificant downward trend, with a decrease rate of 0.061 °C/(10 a). An increasing trend is found in northern Guangdong with an increase rate of 0.3 °C/(10 a), whereas a downward trend is found in the Pearl River Delta with a decrease rate of 0.16 °C/(10 a). (5) The monthly variation of the ground-air temperature difference in northern Guangdong has a single-peak structure, while that in the Pearl River Delta has a double-peak structure. The minimum ground-air temperature difference between the two places is in March, the peak in northern Guangdong is in July, and the peak in the Pearl River Delta is in July and October. Moreover, the annual average temperature and the ground-air temperature difference in summer in the Pearl River Delta both changed abruptly in 1992. There are differences in the spatio-temporal distribution of ground-air temperature difference between northern Guangdong and the Pearl River Delta. [ABSTRACT FROM AUTHOR]

The international non-tariff trade protection against China has gradually increased since 2018, hindering technology trade. Under the impact of the new trade protection, we still know little about how the electronic communication industry (as one of the strategic high-tech industries)changes the innovation cooperation relationship and the innovation performance. Owing to the failure of geographical research to integrate trade protection into the existing research framework from an institutional perspective, the trade protection literature and the innovation geography literature do not intersect. However, the trade geography literature has not paid enough attention to the evolution of industrial innovation in China in recent years and has not taken into account the heterogeneity of the industry-college-institute cooperation and innovation relationship and its impact on regional industrial innovation performance. Based on the 2014-2021 US Export Control Regulations and the invention patent data of the electronic communication industry in the Pearl River Delta, this study uses descriptive statistics, a Quadratic Assignment Procedure, and a negative binomial regression model. It explores both the mechanism and effect of a new round of trade protection on industry-college-institute cooperation and their joint impact on cooperative innovation performance. The study finds that the structure of the industry-college-institute cooperative innovation relationship in the electronic communication industry of the Pearl River Delta has gradually decentralized, and its heterogeneity growth tends to stall. The new round of trade protection significantly regulates geographical proximity, deteriorating the geographical scale of cooperative innovation. The regression results show that under the impact of trade protection, the heterogeneity of industrycollege-institute cooperation changes from positive to negative, and the inverted U-shaped relationship has reached a significant level. Trade protection changes the influence of social and cognitive proximities and of geographical proximity on cooperative innovation performance, and the moderating effect of trade protection is highlighted by the positive effect of strengthening geographical proximity on industry-college-institute cooperation and innovation performance. The above findings remind us of the need to further refine and optimize innovation support policies. Therefore, the study puts forward some targeted policy suggestions, namely, to formulate innovation support policies suitable for the internal and externalized innovation transaction costs of different types of enterprises, strengthen the dominant role of enterprises in innovation, and promote crossregional cooperation. To a certain extent, it can inform the decision-making by China's regional strategic industries around ending the international technology trade blockade and achieving high-quality independent innovation and technical cooperation. [ABSTRACT FROM AUTHOR]

The spatial-temporal pattern of auto manufacturing has attracted scholars' great interests. The Pearl River Delta (PRD) is an important part of the Guangdong-Hong Kong-Macao Greater Bay Area, which is one of the world's four major bay areas. However, there is little study on the spatial-temporal pattern of auto manufacturing and its dynamics in the this area. Based on the economic census employment data of the nine cities in 2013 and 2018, the density, Theil Index and Global Moran's Index are employed to discuss the characteristics of auto manufacturing distribution in PRD during 2013-2018. It founds that: The density of the PRD and the east bank of the Pearl River is high. The density of Shenzhen, Guangzhou and Foshan is higher, and the density of two core cities (Guangzhou and Shenzhen) suburbs and the seven city centers with auto enterprises is higher. Distribution of auto manufacturing had become more uncorrelated. The degree of concentration is moderate and decreasing. Global production network theory of extra-firms--auto lead firms and governments bargaining strategy determines the distribution of assemblers in Guangzhou, Shenzhen and Foshan city of the around Pearl River area and the east bank. As a result, the density of districts (majority of them in the suburbs) in these two regions and three major cities with assemblers is higher. Extra-firms--auto parts and district governments bargaining strategy, inter-firms--auto lead firms and suppliers partnership strategy, and intra-firms--auto lead firms coordination strategy decided the initial distribution of the auto parts in those districts around or within two hours' driver from their upstream suppliers mainly assemblers. However, with the governments of industrial parks without assemblers providing more preferential land, tax and other policies to parts enterprises in the bargaining process, auto parts dispersed more, the density of these districts with industrial parks usually in the city centre of seven cities except Guangzhou and Shenzhen became higher, the spatial distribution increased uncorrelated, the degree of concentration was medium and showed a downward trend. [ABSTRACT FROM AUTHOR]

Based on the municipal panel data from 2010 to 2020, a coupling coordination model was constructed to explore the spatial and temporal evolution of the coupling coordination level of science and technology innovation (STI) and urban resilience in the Pearl River Delta (PRD). The conclusion shows In terms of urban resilience, the PRD city cluster as a whole shows a fluctuating upward trend, with obvious internal differences among cities, creating a spatial distribution pattern of "high in the middle and low at the eastern and western edges". In terms of the level of STI, the PRD city cluster as whole shows a wave-like upward trend, with significant differences within the region, forming a circling development pattern centered on Guangzhou and Shenzhen. The degree of coupling and coordination between STI and urban resilience in PRD city clusters has generally risen slowly, realizing the leap from dissonance to relative coordination. However, the absolute values of each city need to be further improved, and the remaining eight cities except Shenzhen are at the stage of barely/primary coordination. Intercity differentiation is obvious, forming a "center-periphery" circle pattern. Finally, this paper constructs a policy system from the three dimensions of promoting the development of the two systems themselves, formulating the coupled and coordinated development plan of the two, and narrowing the regional development gap. [ABSTRACT FROM AUTHOR]

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Food self-sufficiency has long been regarded as essential for understanding and managing urban and regional food systems; however, few studies have examined the food self-sufficiency of megacity regions within a comprehensive framework that distinguishes different types of agricultural land (i.e., arable land, horticultural landscapes, and waters). To fill these gaps, we took the Pearl River Delta as a case study and quantified the foodsheds of different types of agricultural land by calculating the land footprint of food consumption. On this basis, food self-sufficiency is defined as the ratio of available and required agricultural area for regional food demand. The results indicated that the self-sufficiency level provided by the arable land in the Pearl River Delta is low and cannot realize self-sufficiency at the regional and urban levels. The horticultural landscapes can provide self-sufficiency at the regional level, whereas the regions with water cannot, as their foodsheds extend over the boundary of the Pearl River Delta. For arable land, establishing a localized regional food system requires expanding the foodshed size. These findings provide evidence that megacity regions may face increasing difficulties in achieving self-sufficiency in the near future. This research can improve policymakers' understanding of the sustainability and resilience of regional food systems in megacity regions. [ABSTRACT FROM AUTHOR]

The methods of deep seismic sounding (DSS) and dense nodal array (DNA) are based on the same observation systems and instruments. DSS offers advantages in constructing velocity models of the crust and upper mantle, whereas DNA is used to build crustal geometric models. Combining DSS and DNA can effectively enhance the deep earth exploration techniques. This study provides an example of such integration. We applied the teleseismic receiver function imaging method to the continuously recorded data from the DSS profile L1 and constructed a crustal geometric structure model for the Pearl River Delta. The study revealed the following characteristics of the crustal structure and fault zone: (1) the crustal thickness is 28–30 km, thinning gradually southeast of the Wuchuan-Sihui fault; (2) the average crustal VP/VS is ~1.73 near the Wuchuan-Sihui fault, but < 1.70 in other segments; and (3) a low-velocity zone exists in the upper to middle crust, horizontally separated by the Enping-Kaiping fault zone. These results suggest that the crust of the Pearl River Delta region has undergone significant thinning. The low average crustal VP/VS and lower crustal VP indicate that this is mainly caused by the lower crust thinning. We propose that the Wuchuan-Sihui and Enping-Kaiping faults dip eastward into the deep crust and may penetrate the Moho. The formation and evolution of these faults are controlled by thermal uplift and the southeastern extension of the lithospheric mantle. Joint exploration using DSS and DNA provides multi-parameter and multi-scale constraints on the crust and upper mantle structures, offering significant insights into the interface properties, fault extension, and melt flow distribution. The combined DSS and DNA techniques has broad applications in deep structural probing and mineral resource exploration.

Since the 2008 global financial crisis, the United States, Britain, Germany, and other developed Western countries have regarded manufacturing as a driving force for economic revitalization. The United States proposed the concept of advanced manufacturing and issued a series of policies to ensure its leading position in the manufacturing industry by promoting the development of advanced manufacturing. Advanced manufacturing is the only way for China to move from a large manufacturing country to a powerful manufacturing country, and it is also the direction of manufacturing development. Therefore, it has received great interest from officials and academics. However, as it is difficult to define the categories of advanced manufacturing in national statistical standards, only a few studies have focused on the definition and policies of advanced manufacturing and a case study on the spatial-temporal patterns at the urban level under the influence of local policies. There have been no studies on the spatial-temporal pattern of advanced manufacturing at the regional level and its influencing factors to promote the development of regional advanced manufacturing clusters. The spatial-temporal patterns of the advanced manufacturing distribution at the regional level are not only affected by local policies, but also related to the characteristics of each city within the region and the agglomeration and spillover characteristics of enterprises between different cities. How these factors affect the regional level of advanced manufacturing distribution and the spatial-temporal characteristics warrants further research. Based on four sets of economic census employment data at the district-level in 2004, 2008, 2013, 2018, this study uses the density, growth rate, Theil index, and Global Moran's Index to explore the spatial-temporal pattern of advanced manufacturing distribution in the Pearl River Delta and its influence factors. It found that (1) the density around the Pearl River area and the east bank is higher than that of the peripheral area and the west bank, but the growth rate of four parts is similar during the whole period and it appear negative during between 2014 and 2018. (2) the density of nine cities in order are: Shenzhen> Dongguan> Zhongshan> Foshan> Zhuhai> Guangzhou> Huizhou> Jiangmen> Zhaoqing; the growth rate of nine cities are: Zhaoqing> Huizhou> Shenzhen> Foshan> Zhuhai> Zhongshan> Dongguan> Guangzhou> Jiangmen, and that of Shenzhen, Foshan, Zhongshan, Dongguan and Guangzhou is negative between 2014 and 2018. (3)spatial distribution evolves from "core-multiple edges" to "core-multiple subcores-multiple edge", the density of Guangzhou and Shenzhen appears suburbanization, density of districts becomes higher, growth rate of districts gets lower and that of 84% districts are negative between 2014 and 2018, Global Moran's Index is high but decreasing, Theil Index is above-moderate and increasing. Government encouragement policies of regions and cities, urban characteristics of location advantage and port advantage, and enterprise characteristics of agglomeration economy promote advanced manufacturing agglomeration, increased density, high spatial distribution, and multiple core emergence; The government optimization policies of digitalization and environmental regulation, and the enterprise characteristics of spillover effects lead to the suburbanization of big cities, the negative growth of the Pearl River Delta region from 2014 to 2018, and the decreasing trend of spatial distribution correlation. This study focuses on the spatial-temporal patterns of advanced manufacturing distribution representing the development direction of manufacturing and its influencing factors in the Pearl River Delta to provide a reference for government decision-making at all levels in the Pearl River Delta, to formulate policies to promote the development of advanced manufacturing, enhance the economic strength of the Pearl River Delta, and realize China's dream of becoming a powerful manufacturing country.

Nitrogen (N) has received attention as an indicator of water quality and pollution. However, there is still a lack of systematic research on the influence of temperature. An experiment was conducted with five tanks containing sediments from the Pearl River Delta region of China and distilled water to assess the release of N from sediments under controlled conditions; temperatures from 10 to 30 °C were assessed. Results show that the effect of temperature on N in the water column and sediment is nonlinear. NO3-N was affected at temperatures between 20 and 25 °C in shallow sediments (1–3 cm below the sediment–water interface) with rapid increase concentration, while NH4-N concentration in water column was decreased significantly with increased temperature between 10 and 15 °C. NO3-N was dominant at temperatures from 25 to 30 °C. However, the presence of NH4-N in a water body can inhibit its release, thus the relationship between the diffusive flux with temperature is not linear. The relationship between N diffusive flux at the sediment–water interface was described by Polynomial2D and Lorentz2D models. HIGHLIGHTS General relationship for nitrogen concentration in the water column.; Distribution of nitrogen in water column and sediment with temperature.; Nitrogen flux at the sediment–water interface at different temperatures.; Effects of dissolved oxygen, pH, on nitrogen release from sediments.; Nitrogen pollution control measures in different seasons.;

Cellular automata (CA) models have been extensively employed to predict and understand the spatiotemporal dynamics of land use. Driving factors play a significant role in shaping and driving land-use changes. Mining land-use transition rules from driving factors and quantifying the contribution of driving factors to land-use dynamics are fundamental aspects of CA simulation. However, existing CA models have limitations in obtaining accurate transition rules and reliable interpretations simultaneously for multiple land-use simulations. In this study, we constructed a CA model based on a tree-based deep learning algorithm, deep cascade forest (DCF), to improve multiple land-use simulations and driving factors analysis. The DCF algorithm was utilized to mine accurate multiple land-use transition rules without overfitting to improve CA simulation accuracy. Additionally, a novel ensemble mean decrease of impurity (MDI) factor importance analysis method (DCF-MDI), which leverages the cascade structure of the DCF model, was proposed to qualify the contribution of each driving factor to land-use dynamics stably and efficiently. To evaluate the effectiveness of the proposed DCF-CA, we applied the model to simulate land-use distributions and explore the driving mechanisms of land-use dynamics in the Pearl River Delta (PRD), China, from 2000 to 2010. Compared to existing models, the proposed DCF-CA model exhibits the highest accuracy (FoM = 23.79%, PA = 39.77%, UA = 36.35%, OA = 91.50%), which demonstrates its superiority in mining accurate transition rules for capturing multiple land-use dynamics. Factor importance analysis reveals that the proposed DCF-MDI method yields more stable ranking orders and lower standard deviation of contribution weights (