Water-quality responses and management-oriented spatial thresholds in a complex river-estuary continuum.

In this paper, according to the fieldwork and statistic analysis, the issues for the relativity between airborne microbes and environmental factors in Pearl River delta’ Urban Agglomeration, Guangdong are discussed using ecological method in order to research on health prevention and environment control measures in Pearl River delta’ Urban. The results show that as follow:(1) The average content of airborne microbes (fungi and bacteria) in Guangzhou and Dongguan is higher than other 6 cities in Pearl River delta’ Urban; the content of bacteria is higher than fungi; outdoor content is higher than indoor content; the average content of airborne microbe in the area without greenbelt is higher than the area with greenbelt; the average content of airborne microbe are higher during spring and summer than other seasons. (2) There are obvious relativity between the average content of airborne microbes (fungi and bacteria) and environment factors (wind speed, humidity, temperature, total suspended particulate (Tsp); Furthermore, most of those have positive or negative linear relationship. (3) There are also obvious relativity between the average content of airborne microbes (fungi and bacteria) and the number of person flowrate, car flowrate and condition of afforestation, population density.

This paper takes the PRD (Pearl River Delta) urban agglomeration as the research object and improves the gravity models to estimate and analyze synergetic development potential of exhibition economy in eight major PRD cities. Firstly, it makes a factual analysis of the overall development trends and characteristics of exhibition economy in China, and introduces the development status of exhibition economy in the PRD Economic Circle. Secondly, it constructs indicator systems for the development evaluation of exhibition economy and evaluates comprehensive development capacity of exhibition economy in the eight PRD cities. Thirdly, gravity models are improved to calculate the synergetic development potential of exhibition economy in the eight PRD cities. Research Results: The PRD Economic Circle consists of three parts, namely, Guang-Fo-Zhao Economic Circle, Shenzhen-Dongguan-Huizhou Economic Circle and Zhuhai-Zhongshan-Jiangmen Economic Circle. Wherein, Guang-Fo-Zhao Economic Circle is centered on Guangzhou while Shenzhen-Dongguan-Huizhou Economic Circle and Zhuhai-Zhongshan-Jiangmen Economic Circle are centered on Shenzhen. Research Proposals: The local government should establish administrative departments for the synergetic development of exhibition economy in the PRD urban agglomeration, rationalize the allocation of exhibition economic resources, optimize synergetic development structures of exhibition economy, explore characteristic images of cities and integrate them into the PRD Economic Circle; promote synergetic development of exhibition economy in the PRD urban agglomeration, thereby enhancing domestic and international competitiveness of the exhibition industry and driving robust growth of regional economy. Innovations of the paper are described below: it studies synergetic development of exhibition economy in the PRD urban agglomeration for the first time, explores the integration of exhibition economy in urban agglomerations of different levels, seeks solutions for the common development of exhibition economy in urban agglomerations and makes strategic planning for the development of exhibition economy in the PRD urban agglomeration. Currently, there are few researches on the synergetic development of exhibition economy in urban agglomerations of China.

A novel nonlinear direct-mapping approach for multiple time scale driving force analysis of surface water quality variations under intense human interference

The spatial response mechanism of hydrology and water quality of large river-connected lakes is very complicated. In this study, we developed a spatial response analysis method that couples wavelet correlation analysis (WTC) with self-organizing maps (SOM), revealing the spatial response and variation of water level and water quality in Poyang Lake, China's largest river-connected lake, over the past decade. The results show that: (1) there was significant spatial heterogeneity in water level and quality during the dry seasons (2010-2018) compared to other hydrological stages. (2) We identified a more pronounced difference in response of water level and quality between northern and southern parts of Poyang Lake. As the distance increases from the northern lake outlet, the impact of rising water levels on water quality deterioration intensified during the dry seasons. (3) The complex spatial heterogeneity of water level and quality response in the dry seasons is primarily influenced by water level fluctuations from the northern region and the cumulative pollutant entering the lake from the south, which particularly leads to the reversal of the response in the central area of Poyang Lake. The results of this study can contribute to scientific decision-making regarding water environment zoning management in large river-connected lakes amidst complex environment conditions.

Wildfires are landscape scale disturbances that can significantly affect hydrologic processes such as runoff generation and sediment and nutrient transport to streams. In Fall 2016, multiple large drought‐related wildfires burned forests across the southern Appalachian Mountains. Immediately after the fires, we identified and instrumented eight 28.4–344 ha watersheds (four burned and four unburned) to measure vegetation, soil, water quantity, and water quality responses over the following two years. Within burned watersheds, plots varied in burn severity with up to 100% tree mortality and soil O‐horizon loss. Watershed scale high burn severity extent ranged from 5% to 65% of total watershed area. Water quantity and quality responses among burned watersheds were closely related to the high burn severity extent. Total water yield (Q) was up to 39% greater in burned watersheds than unburned reference watersheds. Total suspended solids (TSS) concentration during storm events were up to 168 times greater in samples collected from the most severely burned watershed than from a corresponding unburned reference watershed, suggesting that there was elevated risk of localized erosion and sedimentation of streams. NO3‐N concentration, export, and concentration dependence on streamflow were greater in burned watersheds and increased with increasing high burn severity extent. Mean NO3‐N concentration in the most severely burned watershed increased from 0.087 mg L−1in the first year to 0.363 mg L−1(+317%) in the second year. These results suggest that the 2016 wildfires degraded forest condition, increasedQ, and had negative effects on water quality particularly during storm events.

Under mounting global pressure for carbon emission mitigation, China—currently the world's largest carbon emission contributor—confronts the critical challenge of reconciling emission reduction targets with sustained economic growth and progressive enhancement of citizens' living standards. Adopting a land-intensive utilization framework, this paper systematically investigates the relationship between urban intensive land use (UILU) and carbon emissions (CEs) in China's three major eastern urban agglomerations—the Beijing-Tianjin-Hebei (BTH), the Yangtze River Delta (YRD), and the Pearl River Delta (PRD). Methodologically, standard deviation ellipse analysis, the HR coordination model, and the Environmental Kuznets Curve (EKC) were employed to identify viable emission reduction pathways. Key findings from the 2005–2021 study period reveal four principal patterns: (1) UILU levels across the three urban agglomerations demonstrate an overall upward trajectory; Inter-agglomeration disparities exhibit phased transitional characteristics, following a “contraction-expansion-contraction” sequence, whereas intra-agglomeration disparities manifest persistent widening trends. Spatial analysis through standard deviation ellipses demonstrates distinct orientation patterns: the BTH exhibits a predominant northeast-southwest alignment; the YRD displays northwest-southeast orientation; and the PRD maintains an approximate east-west axis. (2) CEs across the three urban agglomerations demonstrated an overall increasing trajectory, stabilizing during the final phase of the study period. Spatiotemporal analysis revealed distinct orientation patterns: the BTH's standard deviation ellipse maintained a northeast-southwest alignment, while the YRD and PRD exhibited northwest-southeast orientations. (3) The HR coordination degree displayed moderate fluctuation with an overall ascending trajectory, demonstrating hierarchical coordination levels: YRD > PRD > BTH. (4) EKC analysis delineates distinct morphological patterns: The EKC curves for UILU and CEs in the BTH and PRD demonstrated an inverse N-shaped pattern, with turning points at 0.14 and 0.49 for the BTH, 0.13 and 0.44 for the PRD, respectively. In contrast, the EKC relationship for the YRD follows a U-shaped curve with a turning point at 0.20.

Natural resources such as land, air, and water lay a critical foundation for the sustainable development of an urban community. The Pearl River Delta (PRD) is one of the most developed and rapidly developing regions in China, with abundant natural resources in water, intertidal zones, aquatic products, and a significant coastal estuary habitat. The PRD also covers two Special Administrative Regions (Hong Kong and Macao) and two Special Economic Zones (Shenzhen and Zhuhai), critically positioning it domestically and abroad. However, the increasing development of the economy has put pressure on the security of its water resources. These resources have sharply deteriorated in the PRD as the result of a mass and unordered overuse of water and soil resources and the lack of coordinated efforts among different functional departments. Various problems related to the water environment (such as flooding, rapid development of the deposition, water pollution, saltwater intrusion, and waterway atrophy) have directly threatened the social stability, sustainable development of the economy, and the supply of water in the region. To date, the population affected by a shortage of high-quality water has reached 16 million due to pollution of the water supply source in Guangdong province. At this time, the water pollution in the PRD has resulted in ever-increasing economic and environmental losses. Pollution coverage includes Hong Kong, Macao, and Guangdong and, because governmental functions and scientific technologies among these regions differ, there is little in the way of efficient, cooperative efforts to fully make use of their individual advantages to protect the water environment in the PRD. Moreover, the diversity and complexity of the problems even interfere with the abilities of functional departments within one region (e.g., flood prevention, pollution abatement, and channel maintenance) to make decisions and formulate protection policies using advanced spatial technologies such as remote sensing (RS) and geographic information systems (GIS). Consequently, the water environment in the PRD lacks unified and synergistic operations, and water resource protection is restricted to satisfying the demands of economic development and the requirements of sustainable development. To date, it is clear that cooperation amongst Guangdong, Hong Kong, and Macao should be strengthened. More research is also essential, specifically regarding the reduction of gross pollution emissions by 8 to 10 percent. In addition, the water environmental protection of the PRD has engaged with the Integrative Planning of the Environmental Protection in the PRD (2009-2020). This emphasizes strengthening the regional collaborative linkages, constructing an integrative platform of environmental monitoring, and realizing the shared and collaborative management of environmental information among different departments. With this in mind, the study on constructing a unified and synergistic system for water environment analysis in the PRD area are proposed as interdisciplinary and comprehensive research using multiple methods and fields. Based on the analysis of the fusion techniques of multisource, multi-date, and isomerous images, a database for integrating remote sensing monitoring data of water quality and quantity, actual measurement data, and relevant basic geographical data (watercourse data, section data, and a Digital Elevation Model) will be developed. Combining the research on general analytical methods and models, the capsulation mechanism of analytical methods and models will be designed. Lastly, using GIS integration techniques, an integrative monitoring demonstrative platform of water quality and quantity will be developed to assist collaborative research and decision making among the functional departments of the three regions. The goal is to promote the sustainable use of the water resources in the PRD, to achieve sustainable economic development and to increase the informatization of the PRD region. The construction of the system consists of four parts.

Innovation is an important factor to improve the quality of economic growth, and amplifying the innovation spatial spillover effect is an important measure to support the development of innovation. Scholars have carried out diversified research on the innovation spatial spillover effect, but there is still practical significance for deepening the research on the spatial spillover effect. In particular, the multi-angle comparative study in different regions still has research value, especially for the field of urban agglomeration integration. The spatial econometric model is a common method to measure spatial spillover effect. In order to carry out a multi-angle comparative study of innovation spatial spillover effects in different regions, this study takes two typical integrated urban agglomerations of the Yangtze River Delta and the Pearl River Delta in China as the object, and conducts a comparative study of the evolutionary characteristics of innovation spatial spillover effects based on urban scale data and the spatial econometric model. Differently from previous studies, invention patents are adopted to characterize the innovation level. The results show that there are significant positive innovation spatial spillover effects in the Yangtze River Delta and the Pearl River Delta, and the spatial spillover effect in the Yangtze River Delta is stronger. The spatial spillover effect exhibits significant spatiotemporal heterogeneity. For example, the spatial spillover effect in the core region and the fringe region of the urban agglomeration exhibits a positive effect, but the Yangtze River Delta is stronger than the Pearl River Delta. As an important innovation, the spatial spillover effects both exhibit the evolutionary characteristics of “inverted U-shape” based on the changes in geographical distance, and the spatial spillover effect of the Yangtze River Delta is always larger. Based on the empirical research, we propose promoting high-quality development by strengthening urban agglomeration cooperation, realizing urban agglomeration expansion in an orderly way, and improving the macro-political system.

In Pearl River Delta (PRD), river water quality has deteriorated gradually due to population increase and ongoing industrialization and urbanization. In this study, multivariate statistic methods were used to assess water quality spatial pattern and to identify characteristics of water quality variation in the PRD. Water quality monitoring of the PRD during the year 2005 and 2008 was conducted at 25 different stations. Seventeen water quality parameters were analyzed for further studying. Results of one-way analysis of variance (ANOVA) indicated that all the parameters except air temperature, water temperature and zinc showed significant difference among monitoring stations in both dry and wet season. Monitoring stations in the PRD were separately classified into three statistically significant clusters at (D link/D max) < 2 in dry and wet season, respectively. The three clusters indicated the similarity and dissimilarity of river water quality among 25 monitoring stations, corresponding to heavy pollution, moderate pollution and slight pollution. Thus, the results of this study are useful to evaluate water quality and manage water resources in the PRD.

In the context of climate change, studying the ecological efficiency (EE) of urban agglomerations is of great significance in promoting sustainable development. First, night light data are used as the expected output to build an evaluation index system based on the five major urban agglomerations, namely, the Yangtze River Delta, Pearl River Delta, Beijing–Tianjin–Hebei, the middle reaches of the Yangtze River, and Chengdu–Chongqing urban agglomerations. Second, the super-efficient Epsilon-based (super-EBM) model and the input–output redundancy rates are used to measure the EE of the five major urban agglomerations from 2006 to 2018. Then, their spatial differences are explored with the help of the Gini coefficient. Finally, the spatial differences in the EE drivers of urban agglomerations are analyzed using Geodetector. The results reveal the following. (1) The EE of the five major urban agglomerations present the decline fluctuation trend of “∧”. However, this trend has slowed down. From the perspective of urban agglomeration, Beijing–Tianjin–Hebei &gt; The Pearl River Delta &gt; Chengdu–Chongqing &gt; Yangtze River Delta &gt; the middle reaches of the Yangtze River. The lowest efficiency of the Yangtze River’s middle reaches has “high investment, low output, and high pollution” characteristics. (2) The EE of the five major urban agglomerations had weak synergistic development and noticeable spatial differences. The primary sources are inter-group differences and hypervariable density. (3) From the perspective of influencing, the difference in technological innovation levels (TEC) is the single leading factor in the differences in the EE space of urban agglomerations. In addition, the interaction combination of industrial structure upgrades (IDS) and traffic infrastructure (TRAF) is a crucial combination driver. However, the core influencing factors of spatial differences in EE in five urban agglomerations are heterogeneous. Among them, the nature-influencing factors of the EE space differences in the Beijing–Tianjin–Hebei and the Chengdu–Chongqing urban agglomerations are environmental regulations (ER). Meanwhile, the influencing factor in the Yangtze River Delta urban agglomeration is the development of urbanization (URB). Moreover, the prominent factor in the middle reaches of the Yangtze River and the Pearl River Delta urban agglomerations is foreign direct investment (FDI). On this basis, this study aims to promote ecological civilization construction in urban agglomerations and optimize regional integrated spatial patterns.

In the Pearl River Delta (PRD), river water quality deteriorates continually due to the population increase and ongoing industrialization and urbanization. In this study, a water quality management paradigm based on the seasonal variation is proposed. For better exploring the seasonal change of water quality, wavelet analysis was used to analyze the division of dry and wet seasons in the PRD during 1952–2009. Then water quality seasonal variation in 2008 and relevant impact factors were analyzed by multivariate statistic methods as a case to make some management measures. The results show that there are some differences of dry and wet seasons division among different years. Wet season mainly appear from April to September, which occupy the largest proportion among the 58 years (about 70%) and then followed by the wet season from May to October (about 13.8% of the total years). As to the water quality of 2008, significant differences exist between dry and wet seasons for 17 water quality parameters except TP, ${\rm NO}_{3}^{- } $, Fe2+, and Zn2+. Levels of parameters pH, EC, CODMn, BOD5, ${\rm NH}_{4}^{ + } $, ${\rm SO}_{4}^{2- } $, and Cl− in dry season are much higher than those in wet season. In dry season the variations of river water quality are mainly influenced by domestic sewage, industrial effluents, and salt water intrusion. While in wet season, except the aforementioned pollution sources, drainages from cultivated land and livestock farm are also the main factors influencing water pollution. Thus, water quality management measures are proposed in dry and wet seasons, respectively. The results obtained from this study would further facilitate water quality protection and water resources management in the PRD.

The Pearl River Delta (PRD) is a major economic and manufacturing area in South China. Using the comprehensive and authoritative monitoring data, this study conducted a systematic review of the regularity of marine disasters (e.g., storm surges, saltwater intrusions, and red tides), water quality variations, water quality risk assessments and wastewater treatment in seven sections of the Pearl River Estuary (PRE). The total water resources in the PRD have been a decreasing in recent years. Seasonal marine disasters occur frequently, causing loss of life and economic damage. A monitoring and early-warning system was constructed to provide a scientific basis for dealing marine disasters response. Based on the water quality monitoring data from the seven main PRE sections from 2015 to 2020, chemical properties, heavy metal concentrations and comprehensive pollution indices were selected as indicators. The water quality of the seven PRE sections, flowing westward into the South China Sea improved over time. According to a water quality risk assessment, Yamen the estuary nearest the sea is at the highest risk. The PRD had a wastewater treatment rate of 97.37%, which was equal to the average of Guangdong Province. These findings can be used to predict future trends in estuarine water, quality and inform future studies of water quality variations in the PRD.

Analysis of structural evolution and its influencing factors of the high-speed railway network in China's three urban agglomerations

Riparian zones serve as the interface between streams and the surrounding landscape, and the presence and health of riparian zone vegetation is critical to maintaining water quality in urban ecosystems. In recent years, light detection and ranging (LiDAR) has been used to characterize vegetation structure, and vegetation structural diversity has been tied to key ecosystem functions across ecosystems including productivity and nutrient dynamics. However, the extent to which LiDAR-derived structural diversity metrics reflect the functioning of riparian zones in urban environments remains poorly understood. Here we show that LiDAR-derived structural diversity metrics provide scalable assessments of riparian zone functioning in a mixed-use agricultural-urban stream system. Using elastic net models, we found that structural metrics, including vegetation area index (VAI), vertical complexity index (VCI), and 95th percentile vegetation height, are strong predictors of nitrate ( adj. R² = 0.741), phosphate ( adj. R² = 0.465), and total suspended solids ( adj. R² = 0.436) when assessed at the full upstream riparian network scale. Models at local spatial scales performed poorly, emphasizing that riparian vegetation structure impacts water quality cumulatively across entire stream networks rather than at immediate upstream reaches. Land cover variables, including percent grassland and developed area, also remained important, highlighting that vegetation structure alone does not fully control water quality. By demonstrating the viability of LiDAR-derived structural diversity metrics in assessing riparian zone functioning, this study advances remote sensing-based monitoring efforts for urban riparian zones and can help direct field-based efforts to restore riparian zone health.

To investigate the differences in water quality response to landscape features at multiple spatial and temporal scales for different lake types， the Dianchi Lake （Tectonic Lake） in Kunming， Yunnan Province and Fushun West Lake （Hecheng Lake） in Zigong， Sichuan Province were used as the objects of the study. Land use types and landscape pattern indices were extracted at five spatial scales of 200， 400， 600， 800， and 1 000 m buffer zones of the Dianchi Lake basin in Kunming and 20， 40， 60， 80， and 100 m buffer zones of the Fushun West Lake Basin. Combined with lake water quality data from the wet season （July 2022） and dry season （April 2023）， the correlation analysis and the redundancy analysis （RDA） were used to quantitatively compare the differences in the multi-temporal and spatial scale responses of water quality to landscape characteristics between two types of lakes. The results showed that： ① All land use types of Fushun West Lake were urban land， and the land use types of Kunming Dianchi were richer， in which urban land was dominant. The landscape fragmentation of both lakes decreased with the increase of spatial scale. Due to the different landscape characteristics of the two lake basins， their water quality was better in the dry season than in the wet season， and the water quality of Fushun West Lake was better than that of Kunming Dianchi. ② Fushun West Lake had the highest explanation rate of the landscape characteristics to the water quality at the scale of 60 m lakeshore buffer zone in the dry season， whereas Kunming Dianchi had the strongest response to the landscape characteristics in the wet season and 800 m lakeshore buffer zone. The response of water quality to the landscape characteristics of Kunming Dianchi was higher than that of Fushun West Lake. ③ There were significant differences in the response of water quality of varying lake types to different landscape features at different spatial and temporal scales. In this study， the urban land was a "sink" landscape of water quality in the Dianchi Lake basin in both dry and wet seasons， while the Fushun West Lake basin was a typical "source" landscape. Forest land was a "source" of polluted water quality at multiple spatial and temporal scales in the Kunming Dianchi basin， with a negative correlation between buffer scale and most water quality indicators at more distant lakeshore zones during the dry season. Patch density was the most critical indicator affecting water quality in Dianchi and Fushun West Lake watersheds. Moreover， the landscape shape index had a greater impact on the water quality of Fushun West Lake than that of Kunming Dianchi. By studying the differences in the response of water quality of different lake types at multiple spatial and temporal scales， this study helps to better predict and respond to the potential impacts of environmental changes on water resources and ecosystems. It also provides a scientific basis for the development of more precise and effective water resource management and protection policies by optimizing the allocation of water resources and strengthening ecological protection and environmental governance.