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In the Guangdong-Hong Kong-Macao Greater Bay Area (GBA), microplastic pollution in urban rivers is a prominent problem due to the developed economy and high industrial intensity. Using the Xiaohai River, Hanxi River and Dongguan Canal in Dongguan City, an important node city in the GBA, as an example, microplastic characteristics, drivers and ecological risks in the surface water of three rivers were investigated. Results showed that the average abundance of rivers in the wet period (1646.22 ± 154.73 items/m3) was 4.7 times higher than that in the dry period (351.09 ± 34.2 items/m3). Microplastics were mainly in the form of fragments and fibers, with a size range of 30–500 μm, and appeared transparent with white color. The microplastic polymer types PE, PP, PET and PA accounted for more than 70%. There are large differences in the characteristics of microplastic pollution during different hydrological periods. Redundancy analysis showed that the distribution of plastics, chemical materials, packaging and printing industries along the rivers dominated the differences in microplastic abundance. The electronic information industry contributed most to the composition of microplastic polymer types. The polymer hazard index, pollution load index, and potential ecological risk index for rivers indicate a medium-high risk classification or higher. Therefore, the industrial layout along the urban rivers should be rationalized, the disposal of microplastics in wastewater should be increased, and the use of green plastic products should be promoted. This study provides support for the management of microplastic pollution in urban surface water in the GBA. [Display omitted] • Rivers' microplastic abundance in the wet period was higher than that in dry period. • Industrial distribution affects rivers' microplastic abundance. • Microplastics from chemical materials and paper industries are dominated by PE. • The ecological risk of microplastic in reservoir is greater than that in rivers. • Focus needs to be placed on the microplastic pollution at river confluence. [ABSTRACT FROM AUTHOR]

• A hybrid method was proposed to classify coastal wetlands. • The coastal wetlands in GBA have undergone dramatic changes in the past 30 years. • The developed model has satisfactory performance in accurancy. Coastal wetlands play a vital role in coastline protection. Coastal landscape of the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) has changed drastically. In order to explore the process and law of coastal landscape dynamics in GBA, in this research, multi-temporal Landsat images and proposed hybrid object-based image analysis and multi-level decision tree classification were applied to monitor the changing trends and current status of the coastal landscape in GBA from 1988 to 2018. There were 5818.58 km2 of natural wetlands in 2018, including mangroves (39.62 km2), tidal flats (73.64 km2), rivers (161.65 km2), and shallow seas (5543.67 km2). Due to the influence of anthropogenic activities, natural wetlands showed a decreasing trend, while artificial wetlands and non-wetlands have been increasing. Results indicated that the landscape in the study area showed a trend of fragmentation, the degree of landscape aggregation weakened, the dominant patches were scattered, the shape became more and more complex, and the landscape heterogeneity increased. Then, a future land use simulation model was used to simulate the coastal landscape change trends of GBA in 2028 under four scenarios. The mangrove has the fastest growth rate of 1.47 km2/a under wetland protection scenario. The tidal flat and paddy field would increase under scenarios of the wetland protection and farmland protection, respectively. The construction land has the fastest growth rate under the economic development scenario and would be 47.56 km2/a. Woodland, dry land, and culture ponds are further transformed into other landscape types, while rivers, shallow seas, and reservoirs/ponds have no obvious change. [ABSTRACT FROM AUTHOR]

Water, energy and food (WEF) are closely intertwined. The complex interaction can form the nexus risk due to WEF scarcity. The WEF scarcity nexus risk can cause severe economic losses to adjacent regions through regional trade chains. Investigating the spatial transmission process can help understand regional vulnerability to the WEF scarcity nexus risk. Thus, this research proposes a systematic framework of the WEF scarcity nexus risk monetization method, ecological network analysis (ENA), entropy weight model (EWM) and technique for order preference by similarity to an ideal solution (TOPSIS) to analyze the generation, evolution, transmission and evaluation of WEF scarcity nexus risk. The aims are to intuitively show the harm of WEF scarcity nexus risk through risk monetization and quantitatively analyze WEF scarcity-induced risk spatial transmission. The results indicated that the water-energy-food (W-E-F) scarcity nexus risk was a critical factor restricting regional economic development. Resource-scarce regions/sectors transferred WEF scarcity nexus risk to certain neighboring partners through network trade to ensure local demands. Especially in highly resource-dependent regions (e.g., Guangdong-Hong Kong-Macao region), Hong Kong and Macao would transfer much of the local WEF scarcity nexus risk to Guangdong province, making potential economic losses in Guangdong more significant than local losses. Instead of considering Guangdong, Hong Kong and Macao as competitors, the WEF scarcity nexus risk could be reduced if the three regions worked in a coordinated pattern. Such cooperation has implications for optimizing the industrial structure and sustainable development goals for clean water, affordable energy and food security. [ABSTRACT FROM AUTHOR]

Plastic production and consumption in China are larger than others in the world, and the challenge of microplastic pollution is widespread. With the development of urbanization in the Guangdong-Hong Kong-Macao Greater Bay Area, China, the environmental pollution of microplastics is becoming an increasingly prominent issue. Here, the spatial and temporal distribution characteristics, sources, and ecological risks of microplastics were analyzed in water from an urban lake, Xinghu Lake, as well as the contribution of rivers. Importantly, the roles of urban lakes for microplastics were demonstrated through the investigations of contributions and fluxes for microplastic in rivers. The results showed that the average abundances of microplastics in water of Xinghu Lake were 4.8 ± 2.2 and 10.1 ± 7.6 particles/m3 in wet and dry seasons, and the average contribution degree of the inflow rivers was 75%. The size of microplastics in water from Xinghu Lake and its tributaries was concentrated in the range of 200–1000 μm. In general, the average comprehensive potential ecological risk indexes of microplastics in water were 247 ± 120.6 and 273.1 ± 353.7 in wet and dry seasons, which the high ecological risks of them were found through the adjusted evaluation method. There were also mutual effects among microplastic abundance, the concentrations of total nitrogen and organic carbon. Finally, Xinghu Lake has been a sink for microplastics both in wet and dry seasons, and it would be a source of microplastics under the influence of extreme weather and anthropogenic factors. [Display omitted] • The abundances of microplastic from the urban lake in dry season were higher than that in wet season. • The high-risk status of microplastics was found in the urban lake. • Rivers significantly contributed to the accumulation of microplastic in the urban lake. • The urban lake was a sink for microplastics both in wet and dry seasons. [ABSTRACT FROM AUTHOR]

Water, energy, and food resources are indispensable and irreplaceable resources for the survival and development of human society. This study systematically assessed the three resources system in Guangdong, Hong Kong, and Macao based on constructed direct and nexus-oriented, multi-regional input-output, and ecological network analysis models. Various network analysis (e.g., control, utility, hierarchy, and robustness) was adopted to identify the critical factors of inter-regional resources trade from a perspective of supply-demand. The results indicated that Guangdong, Hong Kong, and Macao have complex control linkages in the three resources trade network, and Guangdong is the key to improving the three resources network structure. The three resources network existed highly competition and exploitation in the three regions. Industrial development is unbalanced and competitive for the three resources. The wholeness water-energy-food trade network of the three regions stayed in a positive environment, but the positive effect level was relatively weak. The three resources network robustness in the three regions is at a medium level. Hong Kong and Macao's water-energy-food network systems have a high vulnerability, and the lowest system robustness was food-related energy in Hong Kong. Finally, we provide some measures to help the sustainable development of the water-energy-food resource system in the three regions, such as cross-regional coordinated management, integration industries development, seawater toilets-flushing, sea rice, and renewable energy. • A comprehensive methodology framework was applied to water-energy-food nexus. • The multi-regional network model for water-energy-food nexus is proposed. • Various network analysis indicators were to assess the complex network trade. [ABSTRACT FROM AUTHOR]