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Uranium is a common radionuclide contaminant in groundwater. Recovery of uranium from uranium-containing water can achieve the dual purposes of uranium remediation and uranium resource utilization. However, very few studies have successfully achieved this task. In this study, we developed a microbial fuel cell (MFC) system with a titanium dioxide nanotube array (TNTA) cathode, which could efficiently remove (over 95%) and recover (over 97%) uranium from uranium-containing water. Results demonstrated that the removal of U(VI) in the MFC was through an adsorption–reduction–deposition mechanism. U(VI) was adsorbed by the TNTA cathode, and the adsorbed U(VI) was further electroreduced to U(IV)O2 and deposited on the surface of the TNTA cathode. The reduction of adsorbed U(VI) initiated re-equilibration of the desorption reaction of adsorbed U(VI) and induced re-adsorption of U(VI). The re-adsorbed U(VI) could be further electroreduced to U(IV)O2, which resulted in the continuous removal of U(VI). Finally, 2.95 μmol U(VI) was reduced and deposited as U(IV)O2 on the surface of the TNTAs (1476.22 μmol m−2) without observing capacity saturation. Moreover, the deposited U(IV)O2 can be easily separated from the TNTA cathode with dilute nitric acid, and the TNTA cathode can be used repeatedly with stable performance.

China has made substantial progress in transforming water governance to respond to water crises and to support rapid socio-economic development. We aim to critically and comprehensively analyze imp...

There has been a growing interest in understanding the enabling conditions for the adoption of irrigation pricing reform worldwide. We enrich the literature on policy diffusion by comparing the eff...

The redox state of arsenic controls its toxicity and mobility in the subsurface environment. Understanding the redox reactions of arsenic is particularly important for addressing its environmental behavior. Clay minerals are commonly found in soils and sediments, which are an important host for arsenic. However, limited information is known about the redox reactions between arsenic and structural Fe in clay minerals. In this study, the redox reactions between As(III)/As(V) and structural Fe in nontronite NAu-2 were investigated in anaerobic batch experiments. No oxidation of As(III) was observed by the native Fe(III)-NAu-2. Interestingly, anaerobic oxidation of As(III) to As(V) occurred after Fe(III)-NAu-2 was bioreduced. Furthermore, anaerobic oxidization of As(III) by bioreduced NAu-2 was significantly promoted by increasing Fe(III)-NAu-2 reduction extent and initial As(III) concentrations. Bioreduction of Fe(III)-NAu-2 generated reactive Fe(III)-O-Fe(II) moieties at clay mineral edge sites. Anaerobic oxidation of As(III) was attributed to the strong oxidation activity of the structural Fe(III) within the Fe(III)-O-Fe(II) moieties. Our results provide a potential explanation for the presence of As(V) in the anaerobic subsurface environment. Our findings also highlight that clay minerals can play an important role in controlling the redox state of arsenic in the natural environment.

Clay minerals are an important host for arsenic in many arsenic-affected areas. The role of bioreduction of structural Fe(III) in clay minerals in the mobilization of arsenic from clay minerals, however, still remains unclear. In this study, Fe(III) reducing bacterium, As(V) reducing bacterium, and Fe(III)-As(V) reducing bacterium were employed to investigate the possible bioreduction pathways for arsenic release from Nontronite NAu-2. Results demonstrated that microbial reduction controlled arsenic mobilization from NAu-2 through Fe(III), As(V), and simultaneous Fe(III)-As(V) reduction pathways. Although the bioreduction of structural Fe(III) led to a negligible dissolution of NAu-2, it triggered a significant release of arsenic from NAu-2. The bioreduction of tetrahedral Fe(III) initiated the release of As(V), and the further bioreduction of octahedral Fe(III) induced the release of As(III) in NAu-2. In addition, bioreduction of As(V) resulted in the desorption and transformation of As(V) from NAu-2. Simultaneous bioreduction of Fe(III) and As(V) led to an almost complete release of As(V) from NAu-2. These findings suggest that simultaneous Fe(III)-As(V) reduction was the dominant pathway governing As(V) release from NAu-2, while structural Fe(III) reduction controlled As(III) release from NAu-2. Therefore, the bioreduction of iron-bearing clay minerals has a great potential for arsenic mobilization in the subsurface environment.

The diverse value of rural areas has been gradually highlighted, and promoting the sustainable development of rural areas with the theoretical guidance of rural multifunction is the key to realizing rural revitalization. This study defined the concept of rural multifunction from the perspective of resident’s demands and divided it into five main functions including rural agricultural production, nonagricultural production, living, ecological environment, and social security. By constructing the evaluation index system of rural multifunction, we analysed the spatial distribution characteristics of 160 villages of Jingjiang in Jiangsu Province. And functional combinations were identified to select targeted rural development paths oriented by balanced development of rural multifunction. The results showed the following. (1) The development of various rural functions in Jingjiang city was uneven, and agricultural production function still dominated. (2) The villages with strong agricultural production function were mainly concentrated in the northwest, while the villages with a high level of nonagricultural production function were mostly distributed in the industrial parks or around towns. There is still much room for improvement in social security function, especially in areas dominated by nonagricultural production. Nonagricultural production function had a negative effect on the ecological environment function, which is contrary to the agricultural production function. (3) Balanced development rather than equal development of rural functions should be pursued to achieve multifunctionality. Scientific guidance for the functional growth of villages in Jingjiang city and theoretical support for the microscale evaluation of rural multifunction and its application were provided by the research results.

Bioreduction of hexavalent chromium (Cr(VI)) to sparingly soluble trivalent chromium (Cr(III)) is a strategy for the remediation of Cr(VI) contaminated sites. However, its application is limited due to the slow bioreduction process. Here we explored the potential synergistic enhancement of iron(III) minerals (nontronite NAu-2, ferrihydrite, and goethite) and electron shuttle anthraquinone-2,6-disulfonate (AQDS) on the bioreduction of Cr(VI) by Shewanella oneidensis MR-1. AQDS alone increased the bioreduction rate of Cr(VI) by accelerating electron transfer from MR-1 to Cr(VI). Iron minerals alone did not increase the bioreduction rate of Cr(VI), where the electron transfer from MR-1 to Fe(III) minerals was inhibited due to the toxicity of Cr(VI) to MR-1. AQDS plus NAu-2 or ferrihydrite significantly enhanced the bioreduction rate of Cr(VI) as compared to AQDS or NAu-2/ferrihydrite alone, demonstrating that AQDS plus NAu-2/ferrihydrite had the synergistic effect on bioreduction of Cr(VI). Synergy factor (kcells+Fe+AQDS/(kcells+Fe + kcells+AQDS)) was used to quantify the synergistic effect of AQDS and iron minerals on the bioreduction of Cr(VI). The synergy factors of AQDS plus NAu-2 were 2.09–4.63 (three Cr(VI) spikes), and the synergy factors of AQDS plus ferrihydrite were 1.89–4.61 (two Cr(VI) spikes). In the presence of Cr(VI), AQDS served as the electron shuttle between MR-1 and iron minerals, facilitating the reduction of Fe(III) minerals to Fe(II). The synergistic enhancement of AQDS and NAu-2/ferrihydrite was attributed to the generated Fe(II), which could quickly reduce Cr(VI) to Cr(III). Our results provide an attractive strategy to strengthen the bio-immobilization of Cr(VI) at iron-rich contaminated sites through the synergistic enhancement of iron(III) minerals and electron shuttle.

Intensifying competition for water induces the growth of water markets in several countries for sharing water between rural communities and cities. While there is a growing recognition that adoption of market mechanisms in environmental governance relies on the state and different institutional arrangements, much less is known about how the interconnections among the state, market-tools, and the community work in practice. In China's distinctive political system, the central government has adopted a 'Two-Hands' approach () to water governance - a combination of strong central regulation and infrastructure development on the one hand, and adoption of market principles on the other to improve water reallocation. A recent study has explored the policy evolution underpinning this transition. However, no studies have systematically examined the implementation of the Two-Hands approach to reveal the underlying institutional hybrid patterns in environmental governance. This study fills this research gap by employing a Fuzzy Set Qualitative Comparative Analysis (fsQCA) to analyze how the interplay of the central government, market, and local governance shapes water rights trading patterns. A total of 29 water-scarce cities using water rights trading with 385 transactions were investigated for the period between 2000 and 2019 by combining evidence from fsQCA and qualitative case-studies. The implications drawn from interpreting the results are as follows: (1) the central government shapes the development of the market and its transactions but this is expressed in multiple ways through pilot projects and the national water exchange platform; (2) establishing water markets and investing in water infrastructure are mutually reinforcing, rather than mutually exclusive; and (3) local governments employ different property rights arrangements to adapt water markets in China's centralized politically institutional context.

Summary Over the past three decades, scholars have studied the effects of more than three dozen factors on collective action in the commons but little is known about the effects of rural to urban migration. We examine this question with the case of China, which has the world’s most extensive levels of rural to urban migration. Using OLS, Logit and Probit models and data from a survey of 1,780 households from 18 provinces, we find that migration has a statistically significant adverse effect on collective irrigation controlling for a large number of theoretically relevant variables. The effects of migration on collective action in the commons are possibly mediated by a number of factors frequently identified in the literature, including leadership, social capital, sense of community, economic heterogeneity, and dependence on resources. We speculate that massive out migration partly explains the significant drop in the use of collective canal irrigation and exacerbated the significant increase in groundwater irrigation since the start of reforms in 1980s. These findings have important policy implications for commons governance in China given that massive rural to urban migration will continue in the next decade. Because of the increasing rural to urban migration worldwide especially in developing countries, the findings could also partly explain the deteriorating state of rural village infrastructure, natural common pool resources and ecological systems in many developing countries.

Harmonious coexistence between human and nature has been an important prerequisite for territorial spatial planning to construct ecological civilizations. The effective way is essential to quantify dynamic modes of land-use changes and their ecological effects. Taking the coastal area of Weifang, eastern regions in China as a case study area, this paper quantified the spatiotemporal characteristics and ecosystem service value of salt field utilization using the theories and methods of geoscience analysis by using satellite imagery and land-use change survey data. The results showed that the area of salt field utilization first increased and then decreased with an upward trend in spatial separation. In the early study stage, the saline-alkali land was mainly developed into a salt field, following with the salt field into construction land, and the salt field into water. Changes in the utilization of salt fields reduced the value of ecosystem services by 3 million yuan RMB during the study period. Ecological value-added areas and ecological impaired areas were mainly located in economically developed areas such as Dajiawa Subdistrict, Yangzi Subdistrict and Yangkou Town. These results show that changes in the utilization of salt fields have different effects on ecosystem service values in different regions. It is necessary for Weifang to comprehensively control the utilization of salt fields, and to provide a reference for the preparation of territorial spatial planning.

Severe water pollution is among the top policy priorities in both China and India. This paper undertakes a comparative case analysis to examine efforts in combating river pollution in two major rivers – the Yangtze in China and the Ganga in India. Our analysis suggests that efforts in combating river pollution in the two Asian giants have encountered substantial challenges, such as the lack of comprehensive legal mechanisms to control pollution at the basin level, the lack of coordination among multiple government agencies, and significant gaps in policy implementation. Our analysis also points out considerable differences between China and India in institutional structure, regulatory approaches and policy instruments in dealing with river pollution.

The governance of the commons depends on collective action by resource users, which may be influenced by land use dynamics and changes in livelihood. We examine the case of China that has experienced massive outmigration of its rural population and significant changes to its land use policy. We contribute to the literature by examining the interaction effects of farmland use rights trading and rural labor out migration on collective action for the governance of the irrigation commons, which has the potential to open up a new line of theoretical and empirical inquiry. Using the socio-ecological system framework, we run ordered probit regression based on data from a survey of 125 villages in 18 provinces in China. We find that a moderate degree of farmland use rights trading has a positive effect on collective action for the governance of the irrigation commons and can slow down and mitigate the negative effect of rural labor outmigration. We conclude with implications for land use policy and governance of the commons.

A large area of room mining goaf has been left throughout the history of coal mining worldwide. However, because the pillars cannot perpetually retain stability, the sudden collapse of a large area of goaf can occur. The existing large areas of room mining goaf have become a potential source of geological risks in mining areas with room mining goafs worldwide. To elucidate the distribution and state of the goafs, a survey of the characteristics of goafs was carried out by geophysical exploration and drilling methods. From this complete survey of room mining goafs, this paper has outlined eight common goaf risks, emphasizing the types of goaf risks that require precautions, and the formation mechanisms of each goaf risk has been analyzed. Considering that the occurrence of a risk may lead to several other risks and there is a certain interaction between the risks, more specific room mining goaf risk forms, causes and scopes of influence have been listed. It is advantageous to use a support vector machine, which is useful for small-sample problems, to assess the goafs. A support vector machine assessment model of room mining goafs was established, and sample training and verification were carried out. Comparing the risk assessment results with those of the field investigation, it can be seen that the evaluation model has a high accuracy. This work can greatly contribute to the prediction and prevention of risks induced by room mining goaf.

Backfill mining is an effective way to control ground subsidence and govern gangue. To solve the problem of thin coal seam mining under villages, a new thin seam backfill mining technology was proposed. This paper investigated a reasonable proportion of filling materials by experiments, designed the filling system and introduced key technologies for thin seam working face filling. Finally, an industrial test of thin seam backfill mining technology was carried out in the C1661 working face, Beixu Coal Mine. The results show that the developed filling material meets both the pumping liquidity and strength requirements of the filling body during the early and late stages. The design and equipment selection of the paste filling system were reasonable. By using the key technologies for thin seam working face filling, the time needed for working face filling, the connection and disconnection of the filling pipeline and gob-side entry retaining were all greatly shortened. The labor intensity of the workers was reduced, and the mechanization level of the mine was improved. A fill mining length of 480 m was successfully completed. With effective roof subsidence control, the ground subsidence can be reduced, and good results can be achieved. This study can contribute to the development of backfill mining in thin coal seams.

Ostrom’s Design Principles (DPs) are believed to be a set of the best practical guidance for governing natural resources, but applying the DP theory should consider the local context, especially the political context, which has been examined little so far. Using the Institutional Analysis and Development (IAD) framework as a conceptual and analytical lens, this paper examines the impact of authoritarian context on self-governance in China. Based on the results of Barnard’s test and Crisp-set Qualitative Comparative Analysis (csQCA), our comparative analysis of nine Water Users Association cases provides consistent evidence that supports the DP theory generally on all outcome dimensions. But self-governance under authoritarianism has unique characteristics and its operation depends on proper design of institutional configuration in accordance with context. Our analysis highlights the influence of resource intervention and leadership intervention. It sheds new insights for understanding the significant impacts of the authoritarian context on institutional design of common-pool resources.