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Rivers in urbanised cities are often polluted, black, and odorous, with poor water quality and deteriorated ecology. Despite many river restoration studies, assessments of ecological responses to river restoration practices remain scant. Benthic animals are useful biological indicators showing the change and succession of river ecosystems; however, previous studies have mainly focussed on a few target species without considering overall ecosystem integrity. Here, we used a multi-index biological assessment method, benthic index of biological integrity (B-IBI) to assess ecological responses to river restoration of the Shahe River in subtropical region of China. Spatiotemporal changes in the macrobenthos community structure after restoration were monitored to explore species succession. We found that the number of macrobenthos species increased from 16 to 42, with the emergence of some pollution-sensitive species during the restoration period. Molluscs showed widespread recovery, and their relative proportions almost doubled from 12.5% to 24.4%. Oligochaetes and chironomids were the pioneer species in the recovering communities, while gastropod molluscs and pollution-sensitive aquatic insects were transitional species that first settled during the initial recovery period. Based on our survey data, 25 candidate metrics were selected, and five core metrics (total taxa, Simpson diversity index, percentage of crustaceans and molluscs, percentage of predators, and percentage of collector-gatherers) were identified after screening to establish the B-IBI. Our analysis revealed a distinct improvement in the overall health of the river, with the proportions of "excellent" and "good" sites increasing from zero to 28.6% and from 14.3% to 42.9%, respectively. A correlation analysis indicated that water flow, molluscs, and total phosphorus content were the three drivers of ecological recovery in the Shahe River. Overall, our study demonstrates the importance of governance and restoration of rivers in tropical and subtropical cities, and provides valuable evidence that can guide the design and evaluation of river restoration works., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

As an important water purification and seepage measure for sponge cities, biofiltration systems have been widely used in their construction in China. In order to identify the heavy metal accumulation, pollution, and its potential environmental risk in the biofiltration systems, this study examined the heavy metal contents and spatial distribution characteristics by taking the biofiltration systems of Yuelai new town, Chongqing, the first demonstration area of sponge city construction in China, as the research object, and conducted a risk evaluation of the pollution level and ecological environment in this new town using the contamination factor (CF), geo-accumulation Index ( I geo ), and potential ecological risk coefficient (PERC). The results showed that, except for Mn, the average contents of Cu, Zn, Pb, Ni, and Cd in the biofiltration systems of Yuelai new town were 4.14, 1.77, 4.98, 1.23, and 6.51 times higher than the soil background values of Chongqing. In terms of spatial distribution, the contents of heavy metals in biofiltration systems along the roads in different functional areas showed great differences. The contents of Cu, Zn, Mn, Pb, Ni, and Cd in the industrial area were significantly higher than those of the same types of heavy metals in the biofiltration systems in other areas ( P <0.05). The CF and I geo showed that the pollution level of heavy metals was ranked as follows:Mn

Water is essential for human activities and economic development, and the water environment significantly influences ecological balance and global climate. China and Southeast Asia are the most populous areas in the world, and their water resources are deteriorating day by day. We focus on five representative cities such as, Beijing, Jakarta, Hanoi, Kathmandu and Manila to investigate water-environmental problems with the ultimate goal of providing recommendations for sustainable urban water management. The study found that (1) the water environment of all cities has been polluted to varying levels, while the pollution has improved in Beijing and Jakarta, and the situation in other regions is severe. (2) The aquatic biodiversity has reduced, and its pollution is mainly caused by organic pollutants and decreasing river flow. In addition, numerous people live in megacities without access to clean surface water or piped drinking water, which greatly increases the use of groundwater. Further, frequent floods in the world leads to serious damage to urban infrastructure and further deterioration of water environment quality. To address these problems, countries and organizations have begun to construct wastewater treatment plants and develop water-saving technology to ensure healthy and sustainable development of water environment. The results and practical recommendations of this study can provide scientific insights for future research and management strategies to address water quality challenges during ongoing policy debates and decision-making processes., (© 2021. The Author(s) under exclusive licence to Royal Swedish Academy of Sciences.)

The tourism economy is regarded as an effective way to realize regional sustainable development. Hence, it is of great significance to explore whether and how tourism economy can alleviate regional carbon emission intensity. To this end, a structural equation model (SEM) reflecting the multiple pathways of the carbon emission reduction effect of tourism economy was constructed based on 92 tourism-dependent cities in China, and the existence and formation mechanism of the carbon emission reduction effect of tourism economy were empirically tested. The main findings are as follows: (1) The tourism economy has a significant carbon emission reduction effect in China. Although the direct impact of tourism economy on carbon emission intensity is significantly positive, the indirect impact is significantly negative and stronger than the direct impact. (2) The carbon emission reduction effect of tourism economy presents multiple pathways characteristics. There are single intermediary pathways such as Tourism Economy → Environmental Regulation → Carbon Emission Intensity, Tourism Economy → Opening-Up → Carbon Emission Intensity, and dual intermediary pathways such as Tourism Economy → Opening-Up → Industrial Development → Carbon Emission Intensity, Tourism Economy → Opening-Up → Innovation Capacity → Carbon Emission Intensity. (3) The formation mechanism of the carbon emission reduction effect of tourism economy presents obvious spatial heterogeneity.

Urbanization can lead to changes in urban morphology that alter the urban thermal environment and energy demand. Improving urban ventilation can alleviate the urban heat island effect and reduce urban energy demand. We categorized the ventilation conditions of 31 major cities in China into four levels based on the frontal area index and presented the natural ventilation effects for cities in five different climate zones. We found that the land surface temperature varies between 0.029 and 5.357 °C in areas under the same climate background. Improving ventilation can directly or indirectly contribute to reductions in urban energy consumption. The energy demand in well-ventilated areas can be reduced by up to 6.704%. The largest reduction in urban energy demand was achieved by improving ventilation within the temperate continental climate zone., Competing Interests: Declaration of competing interest This manuscript has not been published or presented elsewhere in part or in entirety and is not under consideration by another journal. We have read and understood your journal's policies, and we believe that neither the manuscript nor the study violates any of these. There are no conflicts of interest to declare., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Public participation in environmental management (PPEM) in China has become increasingly prominent; thus, investigating the factors that underlie participation by the Chinese public in environmental management is important. To this end, we adopted unique data for PPEM, which was measured based on environmental complaints logged by the telephone hotline set up by the Ministry of Ecology and Environment of China. We observed that PPEM greatly varied from one city to another, indicating significant spatial heterogeneity. In addition, complaints were mainly concentrated in four large regions, namely, the North China Plain, the Yangtze River Delta, the Pearl River Delta, and the Chengdu-Chongqing urban agglomeration. Next, a newly developed spatial heterogeneity analysis method, namely, geographical detector, was applied to investigate the driving factors of PPEM. From the factor detector analysis results, we confirmed that the economic level, energy consumption, urban population, college-educated population, wastewater, environmental risk, SO 2 emissions, and PM 2.5 concentrations were the dominant factors that caused citizens to voice environmental complaints. In addition, we noticed that moderately developed cities were the leading risk areas, which indicated that these cities had serious environmental pollution problems and their citizens actively voiced complaints. As economies continue to grow, the populations in these cities are projected to become more aware of environmental quality and will implement stricter regulations to protect the environment and lower complaints. Moreover, the interaction detector analysis results revealed that the interaction of urban and college-educated populations with other factors played more important roles in affecting PPEM., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The activity and fate of heavy metals (HMs) from mining and smelting activities in farmland soil is of great significance to effectively prevent the excessive enrichment of HMs in crops. This study focuses on Baiyin area, a typical mining city in northwest China. In this example, the sources, speciation, and fate of HMs in the farmland soil, and the migration and enrichment characteristics of HMs in the different parts of crops planted in different areas were studied in detail combining the chemical sequential extraction and Pb isotope approaches. Results showed that the mean anthropogenic contributions of HMs in farmland soils were approximately 85%, 88%, 76%, and 41% for the ore district (OD), Xidagou sewage irrigation area (XSIA), Dongdagou sewage irrigation area, and the Yellow River irrigation area, respectively, and the risk that HMs were excessively accumulated in crops in OD and XSIA was high. Compared with soil residual fractions, the isotope ratios 206 Pb/ 207 Pb in non-residual fractions (1.1304-1.1669) were closer to the values of local ores, suggesting that anthropogenic HMs from mining and smelting activities were mainly enriched in the non-residual fractions. The isotope ratios 206 Pb/ 207 Pb in crops (1.1398-1.1686) further confirmed that those anthropogenic HMs were more easily absorbed and concentrated by crops. HMs contents in leaves from OD and XSIA were generally higher than that in roots, suggesting that atmospheric deposition in OD and XSIA had a greater impact on the HMs concentration of crop leaves，while the excess rate of HMs in grain/fruit was the lowest in all parts of crops. The division and classification of crop planting in mining area can effectively help minimize the risk that HMs from anthropogenic source enter the human body through the food chain., (Copyright © 2020 Elsevier Inc. All rights reserved.)

The high pollutant loads discharged from cities pose risks to urban waterways, and in turn the estuarine environments, making it challenging to improve urban liveability. Past studies on the behaviour of pollutants in rivers have largely investigated their transport along the waterway, primarily focusing on the movement of water and sediment. However, the current approaches in pollutant transport modelling provide limited insights into how pollutant transfer between water and sediment phases influences their transport from the upstream towards the estuarine environment. This research study firstly identified typical patterns of metal loads along an urban river in a highly populated city in China. The outcomes were then used to conceptualise metal transfer between water and sediment phases. It was noted that physico-chemical characteristics of water and sediments play a key role in metal transfer between the two phases, and the dominant transfer path (sediment to water/water to sediment) is different between different metals, independent of their origin (crustal, anthropogenic or marine-related). Several scenarios were derived from the conceptualisation of metal behaviour. These in turn were then used to develop real-world scenarios of metal transport in rivers based on the field data. The conceptualisation of metal behaviour confirmed that each metal is likely to have a dominant phase of transport (sediment/water), which is influenced by the dominant transfer path of that metal between water and sediments., (Copyright © 2019 Elsevier Ltd. All rights reserved.)