In the past few decades, extensive epidemiological studies have focused on exploring the adverse effects of PM₂.₅ (particulate matters with aerodynamic diameters less than 2.5 μm) on public health. However, most of them failed to consider the dynamic changes of population distribution adequately and were limited by the accuracy of PM₂.₅ estimations. Therefore, in this study, location-based service (LBS) data from social media and satellite-derived high-quality PM₂.₅ concentrations were collected to perform highly spatiotemporal exposure assessments for thirteen cities in the Beijing-Tianjin-Hebei (BTH) region, China. The city-scale exposure levels and the corresponding health outcomes were first estimated. Then the uncertainties in exposure risk assessments were quantified based on in-situ PM₂.₅ observations and static population data. The results showed that approximately half of the population living in the BTH region were exposed to monthly mean PM₂.₅ concentration greater than 80 μg/m³ in 2015, and the highest risk was observed in December. In terms of all-cause, cardiovascular, and respiratory disease, the premature deaths attributed to PM₂.₅ were estimated to be 138,150, 80,945, and 18,752, respectively. A comparative analysis between five different exposure models further illustrated that the dynamic population distribution and accurate PM₂.₅ estimations showed great influence on environmental exposure and health assessments and need be carefully considered. Otherwise, the results would be considerably over- or under-estimated.

For the foreseeable future, industrial water demand will grow much faster than agriculture. The demand together with the urgency of wastewater treatment, will pose big challenges for most developing countries. We applied the bibliometric analysis combined with social network analysis and S-curve technique to quantitatively analyze 9413 publications related to industrial wastewater treatment in the Scientific Citation Index (SCI) and Social Sciences Citation Index (SSCI) databases from 1998 to 2019. The results showed that: (1) Publications on industrial wastewater treatment have increased from 120 in 1998 to 895 in 2019 with a steady annual increment rate, and researchers have focused more on the application and optimization of existing technologies. (2) China had the highest number of publications (n = 1651, 19.66% of global output) and was a core country in the international cooperation network, whereas the United States and European countries produced higher quality papers. (3) By analyzing the co-occurrence and clusters of keywords and comparing three wastewater treatment categories (physical, chemical, biological), adsorption (n = 1277), oxidation (n = 1085) and activated sludge process (n = 1288) were the top three techniques. Researchers have shifted their focus to treatment technologies for specific wastewater type, such as textile wastewater, pulp and paper wastewater, and pharmaceutical wastewater. The S-curve from articles indicates that physical and chemical treatment technologies are attached with great potential in the near future, especially adsorption and advanced oxidation, while the biological treatment technologies are approaching to the saturation stage. Different pattern is observed for the S-curve derived from patents, which stressed the limited achievement until now and further exploration in the field application for the three treatment categories. Our analysis provides information of technology development landscape and future opportunities, which is useful for decision makers and researchers who are interested in this area.

Microplastic pollution in marine environment has been a growing public concern in recent years. This article analyzed the scientific literatures related to marine microplastics through a combination of social network analysis and bibliometrics. Researches related to microplastics have grown rapidly since 2011, with approximately two-thirds of the total number of articles published in the last three years. Researchers in United States and Europe have provided tremendous support, however, the efforts and progress of Chinese researchers cannot be ignored. Moreover, the international cooperation is getting closer, and related strategies are launched continuously. The results showed that Marine Pollution Bulletin is the most active journal. Through keyword analysis, we understand the development history and current hotspots of the whole microplastics researches, including ecological risks, interrelationship between microplastics and other pollutants, and detection methodology. Finally, some suggestions and perspectives for future microplastics research are provided.

Litter reduction in the coastal and marine environment represents a major challenge but must be prioritized to preserve biodiversity and ecosystems, as well as the goods and services that humans derive from seas and oceans. This paper reviews the available global scientific literature focusing on marine beach litter and tracks its evolution and trends by combining social network analysis and bibliometrics. The relationships and co-occurrences among authors, countries and keywords retrieved from the Scopus abstract and citation database are presented. A total of 1765 publications are analysed: the majority being journal articles. Results reveal the notable worldwide increase in scientific interest in beach litter in the last decade, as well as its multidisciplinary perspectives. This information could be beneficial for the processes that support the improvement of international efforts for beach litter monitoring, removal, and management activities.

Waste foundry sand (WFS) is the by-product of the foundry industry, which is produced about 0.6 tons per 1 ton of foundry industry production. While it cannot be recycled or reused, it will be disposed of in landfills. Today, with increasing attention to environmental issues, the reuse and recycle of materials because of limited resources have been considered. Due to the desirable properties of WFS, many studies have been done on the properties and performance of its use in various industries, especially in concrete technology. The purpose of this paper is to conduct a bibliometric analysis of foundry sand research during the years 1971-2020. Various aspects, such as document types, languages, major journals, key countries, authors, and keywords, have been examined. The collaborations among authors and countries were constructed, visualized, and evaluated through the application of the social network analysis method based on co-authorship relations. Also, keyword cluster analysis has been performed using co-occurrence relations to discover the most prominent issues related to WFS. The results showed that the number of publications (TP) has improved significantly in recent years, especially in 2018-2020. It has increased from 1 in 1971 to 38 in 2020. The engineering subdivision with 33% has had the highest number of papers. Also, India, China, and the USA have the highest number of publications, respectively. Statistical data from the author keyword study showed that in general, papers can be classified into three categories in terms of subject: first, characteristics of WFS and its importance; second, the use of WFS in concrete and the study of mechanical and physical properties as one of its applications; and the third, investigation on environmental effects and damage caused by disposal and landfill of WFS and efforts to find solutions for recycling and reuse. The keywords “Waste Foundry Sand,” “Foundry Sand,” and “Compressive Strength” with a growth rate of 2700%, 1900%, and 1100%, respectively, are important topics in the field of WFS research.

Ecosystems play critically important roles in supporting human society, while human activities seriously disturb their initial balance. Lots of researches on ecosystem services are conducted due to the increasing concern on ecological security worldwide. In order to provide valuable insights for understanding the primary performance of ecosystem services–related studies, a qualitative and quantitative analysis by using a bibliometric tool is performed in this study. Journal impact factor, CiteScore, and h-index are used for identifying influential journals, while h-index is used for recognizing productive countries/territories and institutions. Social network analysis of countries/territories and institutions is visualized, respectively, so that relationships among them can be uncovered. Citation analysis of publications and co-occurrence analysis of high-frequency keywords are also performed to explore hotspots and popular methods in this field. This study uncovers a holistic picture on the primary performance of ecosystem services–related literatures published from 1997 to 2016, including journals, countries/territories, and institutions. Results find that forest, agriculture, and wetland ecosystems attract lots of attention. Finally, major methods used for ecosystem services evaluation are identified and discussed. Research outcomes will provide valuable insights to stakeholders interested in ecosystem services.

Green consumption can facilitate sustainable industrial development and improve the overall efficiency of resource utilization. In response to rapid economic development and increasing environmental emissions, it is critical to promote green consumption so that the whole society can move toward sustainable development. This study aims to systematically review studies on green consumption by means of meta-analysis, bibliometric analysis, and social network analysis. The results show that green consumption is an interdisciplinary research field, involving environmental science, social science, medical science, economics, and other disciplines. Most productive countries, institutions, authors are identified so that the new researchers in this field can find their research partners. Keywords analysis results help identify the research hotpots in this field. It is suggested that future green consumption research should focus on behavior mechanism, stakeholder coordination, and policy evaluation. In general, the results obtained from this study provide valuable information for researchers and practitioners to promote green consumption research.

The planetary boundaries concept has triggered a vast amount of pure and applied scientific research, as well as policy and governance activities globally. Indeed, it has rapidly become a centerpiece of sustainability study. It is crucial to review the scientific state of the planetary boundaries (PB) concept systematically. However, there is a lack of research on drawing a scientific investigation map of planetary boundaries. Therefore, to clarify the spatial and temporal distribution characteristics, research hotspots, and frontiers of planetary boundaries, a scientometric analysis was performed based on 530 academic publications on planetary boundaries from 2009 to 2021. This paper conducted the analysis by visualizing the social network, dual-map overlay, co-cited references, structure variation article, and co-occurrence keywords with CiteSpace. The results show that as a new achievement and paradigm in sustainable development research, the planetary boundaries framework is gradually getting global attention and promotion, which has increasingly become an interdisciplinary hot research topic. The most productive authors and institutions are concentrated in England, the USA, Germany, and Sweden. Relevant articles were mainly published in journals focusing on ecology, earth, marine, veterinary, animal, economics, and politics. In addition, we summarized four predominant research themes by clustering keywords: the calculation of single boundary threshold and present value, the integration with assessment methods such as life cycle assessment and footprint families, the downscaling of planetary boundaries, and the expansion to economic and social domains. For scholars who are interested in this topic, this paper would be a useful reference and guideline.

Whether high-speed rail (HSR) can promote the coordination between the economy and environment is a critical issue that needs to be investigated. We used balanced panel data of 281 prefecture-level or above cities in China from 2005 to 2017 to consider the opening of HSR as a quasi-natural experiment. We integrated the difference-in-differences (DID) model, the spatial difference-in-differences (SDID) model, and social network analysis (SNA) to empirically investigate the impact of HSR on urban environmental efficiency (UEE). The results showed that HSR significantly improved UEE by 4.6% annually during the study period, although the effect of HSR on UEE exhibited a time lag and varied dramatically in different cities. An analysis of the mechanism showed that the effect of technological innovation and the structural effect brought by the opening of HSR were the main contributors to the improved UEE. Further analysis showed that HSR service centrality also significantly improved UEE and HSR opening and HSR service centrality both had positive spatial spillover effects on the UEE of neighboring cities. Several policy implications are proposed accordingly to make full use of the advantages of HSR to improve UEE for China.

As one of the countries with the most severe water resource problems, China faces enormous challenges in the intensive use of water resources. Rapid economic development has led to serious waste of water resources in the industry, resulting in path dependence on water-consuming technologies, namely the concept of ‘water lock-in’. This study aims to estimate the water lock-in effects in various industries in China from 1997 to 2017. To this end, a novel combination of the input–output analysis and social network analysis methods is used to calculate ‘integrated, intra-sectorial and inter-sectorial’ water lock-in, identify the complex water resource dependence relationship and explore the dynamic evolution process of the lock-in mechanism. The research results are as follows. (1) From 1997 to 2017, the integrated, intra-sectorial and inter-sectorial water lock-in coefficients decreased by 82.08%, 77.92% and 83.14%, respectively. (2) Non-metallic minerals and other mining products underwent the largest decline in water lock-in within the sectors, whereas coal, oil and gas extraction products underwent the most significant decline in water lock-in between the sectors. (3) Water lock-in conduction is most durable and obvious from S01 (agriculture, forestry, fishery products and services) to S06 (textiles). Policy recommendations are suggested to realise the water-unlocking path.