Frontiers in Environmental Science

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ISSN / EISSN : 2296-665X / 2296-665X
Published by: Frontiers Media SA (10.3389)
Total articles ≅ 2,862
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, Huixin Ma, Lanqing Qiu, Ting Zhang, Shaofei Li
Frontiers in Environmental Science, Volume 10; https://doi.org/10.3389/fenvs.2022.978385

Abstract:
Flood storage and detention areas are an important aspect of the river flood control system and an effective measure to ensure flood control safety and mitigate disasters in key areas. Using the flood storage and detention area of DaHuangPuWa as an example, the flood diversion evolution of different positions on the Jinbao highway was simulated numerically. The water level, velocity, and flow rate of each observation point during the 100-year flood were calculated. After comprehensive analysis, it is determined that the location of the diversion gate in the flood storage and detention area is better at the diversion gate of Liuwanzhuang. The results of this paper show that the numerical simulation method can provide more scientific and reasonable theoretical support for the design of flood diversion gates in flood storage and detention areas.
Jiahui Xia, , Binhai Chen
Frontiers in Environmental Science, Volume 10; https://doi.org/10.3389/fenvs.2022.943843

Abstract:
Digital technologies offer opportunities and challenges for corporate environmental management (CEM). In this paper, we provide an overview of the literature on the relationship between digital transformation (DT) and CEM using a systematic review approach in the Antecedents, Decisions, and Outcomes (ADO) format. We review 181 papers published in almost 30 years from 1997 to 2022 and identify studies and areas where DT has impacted on CEM. We find that the literature examining the DT-CEM relationship has surged since 2019 and is concentrated in areas such as green sustainable science technology and environmental sciences. Further, we analyze the economic consequences of DT, the drivers of CEM, and the mechanisms of DT on CEM. Based on the literature analysis, we find that there is still a large gap in the literature studying the mediators and moderators of the DT-CEM relationship. Further, we find that firms with DT have better responsiveness and improved CEM by using digital resources to accurately capture the demands of different stakeholders on the environment. Finally, we provide a research framework and possible research directions, and propose corresponding management insights and policy recommendations.
, Vianny Ahimbisibwe, Melvin Lippe
Frontiers in Environmental Science, Volume 10; https://doi.org/10.3389/fenvs.2022.925477

Abstract:
Agroforestry is often seen as a panacea that offers multiple environmental, economic, and social benefits. However, the validity of generalized statements on agroforestry outcomes is doubtful because the evidence base is unclear. Systematic reviews and meta-analyses exist on the topic in addition to many case studies that address specific outcomes of individual agroforestry practices at different sites. However, the overall picture of available scientific evidence on agroforestry outcomes remains opaque due to the wide diversity of existing agroforestry practices, outcome indicators, and spatial locations. To clarify whether and in which areas the research landscape allows conclusions to be drawn about the potential benefits or drawbacks of agroforestry compared to other land uses, an evidence review map was created for the purpose of this study. Based on a systematic literature search and screening, 64 systematic review articles were finally identified that summarize ecological, economic, or social outcomes of at least one agroforestry practice compared to another land use as control. The thematic and spatial coverage of the systematic reviews on agroforestry outcomes is mapped to identify density and research gaps in the evidence base. Moreover, the comprehensibility of the study selection for each identified systematic review is critically assessed. The resulting evidence review map discloses a solid evidence base for environmental outcomes and productivity aspects of individual agrisilvicultural practices, as well as for agroforestry systems when considering an aggregate level. However, the outcomes of individual silvopastoral and agrosilvopastoral practices have been less studied in the literature. A global coverage at the level of individual agroforestry practices is only available for impacts on climate change mitigation. Major research gaps were identified for systematic analysis of social outcomes of all agroforestry types. The results of the evidence mapping highlight further research needs, but also urge for caution in making generalized statements about the benefits of agroforestry.
Boshi Xu, , Zhaoti Li
Frontiers in Environmental Science, Volume 10; https://doi.org/10.3389/fenvs.2022.905410

Abstract:
Salt crust is a soil layer formed by the cementation of soluble salt on the surface or inside of soil with soil particles. The salt crust can alter the soil’s ability to resist wind erosion. To explore the characteristics of different types of salt crust, six kinds of salt (CaCl2, KCl, Na2SO4, NaCl, Na2CO3, and NaHCO3) were selected and six salt contents (0.2, 0.5, 1, 2, 3, and 4%) were set up to conduct the experiment of a sandy soil crust. The experiment compares the characteristics of crust appearance, compressive strength, and toughness of six selected kinds of salt crust. The results showed that Na2SO4 formed the subflorescence, while CaCl2, KCl, NaCl, Na2CO3, and NaHCO3 formed the efflorescences. The compressive strength and toughness of Na2SO4 salt crust initially increased and then decreased as the salt content increased, and both the strength and toughness reached the maximum when the salt content was 3%. At first, the compressive strength of NaCl crusts increased and then stabilized as a result of the increase in salt content. The toughness of the NaCl salt crust experienced an initial increase and then a decrease, reaching the maximum when the salt content was 3%. The compressive strength and toughness of the salt crusts of CaCl2 and KCl increased as the salt content increased. There was a slight increase in the compressive strength of the crusts formed by Na2CO3 and NaHCO3, with hardly any noticeable change even as the salt content increased, and the maximum compressive strength was only 0.03 and 0.40 MPa, respectively. The crusts of Na2CO3 and NaHCO3 were susceptible to wind erosion, while the crusts of KCl, CaCl2, NaCl, and Na2SO4, having high compressive strength and crust toughness, were capable of resisting wind erosion.
Yuan Wang, Yingjun Huang,
Frontiers in Environmental Science, Volume 10; https://doi.org/10.3389/fenvs.2022.989159

Abstract:
This paper takes the inter-provincial panel data of China from 1999 to 2015 as the research sample and uses the GMM estimation method to empirically test the relationship among education input, social security expenditure, and urban-rural income gap. The results show that education input and social security expenditure have a significant impact on the urban-rural income gap, and there are regional differences. Specifically, the augments of education input and social security expenditure widens the urban-rural income gap in the western region, and narrows the urban-rural income gap of the eastern and central regions but has less impact on the eastern region. The paper provides a new perspective for understanding the urban-rural income gap in China, and has a significance meaning for further increasing the educational investment in the western rural areas, and improving the redistribution efficiency of social security expenditure.
, Edo Abraham, Srijan Aggarwal, Manal Ahmad Khan, Ricardo Arguello, Meghna Babbar-Sebens, Julia Lacal Bereslawski, Jeffrey M. Bielicki, Pietro Elia Campana, Maria Eugenia Silva Carrazzone, et al.
Frontiers in Environmental Science, Volume 10; https://doi.org/10.3389/fenvs.2022.918085

Abstract:
Water, energy, and food are all essential components of human societies. Collectively, their respective resource systems are interconnected in what is called the “nexus”. There is growing consensus that a holistic understanding of the interdependencies and trade-offs between these sectors and other related systems is critical to solving many of the global challenges they present. While nexus research has grown exponentially since 2011, there is no unified, overarching approach, and the implementation of concepts remains hampered by the lack of clear case studies. Here, we present the results of a collaborative thought exercise involving 75 scientists and summarize them into 10 key recommendations covering: the most critical nexus issues of today, emerging themes, and where future efforts should be directed. We conclude that a nexus community of practice to promote open communication among researchers, to maintain and share standardized datasets, and to develop applied case studies will facilitate transparent comparisons of models and encourage the adoption of nexus approaches in practice.
Khadijatul Kubra, Anwar Hossain Mondol, , Amin Ullah Palash, Saiful Islam, A. S. Shafiuddin Ahmed, Mst Antara Masuda, Abu Reza Md. Towfiqul Islam, Simul Bhuyan, Zillur Rahman, et al.
Frontiers in Environmental Science, Volume 10; https://doi.org/10.3389/fenvs.2022.778544

Abstract:
The study area was selected in the Rupsha river basin and the sediment samples were collected to determine trace metal concentrations of As, Pb, Cd, and Cr along with biological effects, and potential ecological and human health hazards for adults and children. The concentrations of trace metals were detected from sixty composite sediment samples using an Atomic Absorption Spectrophotometer (AAS) following some sequential analytical procedures. The mean concentrations of trace metals were organized in the descending order of chromium (Cr) (43.2 mg/kg) > lead (Pb) (29.21 mg/kg) > arsenic (As) (5.18 mg/kg) > cadmium (Cd) (1.8 mg/kg). The current study highlighted that metals were attributed to the riverine sediments from natural sources and other anthropogenic sources, particularly from various industries. Based on the effect-range classifications of threshold effect concentration (TEC) and probable effect concentration (PEC), the trace metal concentrations can impact on the sediment-dwelling organisms occasionally especially for Cr, Cd, and Pb. That is, the concentrations had negative biological consequences on aquatic creatures. The assessed potential ecological risk of Cd offers a significant risk to the aquatic ecosystem, whereas As, Cr, and Cd were in low-risk. Most of the sites of the study area were within the range of moderate risk, indicated by the risk index (RI) values. Furthermore, the applied sediment quality indices, geo-accumulation index (Igeo) indicated that sediment was contaminated by Cd whereas contamination factor (CF) denoted that the sediment of the study area was moderately polluted by Pb. However, pollution load index (PLI) revealed that the study area was polluted for cumulative sence especially in winter season. The age-group risk index (HI) was much lower than the threshold limit of 1, showing that the pollution had no non-carcinogenic risk effect. Total carcinogenic risk (TCR) was less than one-tenth of a percentile. For the sake of human and environmental health, proper monitoring of metal element attribution and strict regulation are required to lessen trace metal pollution.
, Edward A. Hobbs, Jeremy M. Testa, Andrew Heyes, Melinda K. Forsyth, Casey Hodgkins, Curtis Szewczyk, Lora A. Harris
Frontiers in Environmental Science, Volume 10; https://doi.org/10.3389/fenvs.2022.866152

Abstract:
Engineered aeration is one solution for increasing oxygen concentrations in highly eutrophic estuaries that undergo seasonal hypoxia. Although there are various designs for engineered aeration, all approaches involve either destratification of the water column or direct injection of oxygen or air through fine bubble diffusion. To date, the effect of either approach on estuarine methane dynamics remains unknown. Here we tested the hypotheses that 1) bubble aeration will strip the water of methane and enhance the air-water methane flux to the atmosphere and 2) the addition of oxygen to the water column will enhance aerobic methane oxidation in the water column and potentially offset the air-water methane flux. These hypotheses were tested in Rock Creek, Maryland, a shallow-water sub-estuary to the Chesapeake Bay, using controlled, ecosystem-scale deoxygenation experiments where the water column and sediments were sampled in mid-summer, when aerators were ON, and then 1, 3, 7, and 13 days after the aerators were turned OFF. Experiments were performed under two system designs, large bubble and fine bubble approaches, using the same observational approach that combined discrete water sampling, long term water samplers (OsmoSamplers) and sediment porewater profiles. Regardless of aeration status, methane concentrations reached as high as 1,500 nmol L−1 in the water column during the experiments and remained near 1,000 nmol L−1 through the summer and into the fall. Since these concentrations are above atmospheric equilibrium of 3 nmol L−1, these data establish the sub-estuary as a source of methane to the atmosphere, with a maximum atmospheric flux as high as 1,500 µmol m−2 d−1, which is comparable to fluxes estimated for other estuaries. Air-water methane fluxes were higher when the aerators were ON, over short time frames, supporting the hypothesis that aeration enhanced the atmospheric methane flux. The fine-bubble approach showed lower air-water methane fluxes compared to the larger bubble, destratification system. We found that the primary source of the methane was the sediments, however, in situ methane production or an upstream methane source could not be ruled out. Overall, our measurements of methane concentrations were consistently high in all times and locations, supporting consistent methane flux to the atmosphere.
Weixuan Song, , Yuhan Zhang, Lianshanyu Qi, Xing Yi
Frontiers in Environmental Science, Volume 10; https://doi.org/10.3389/fenvs.2022.972563

Abstract:
As the key object of carbon emission reduction, resource-based cities’ carbon emission problems are related to the achievement of China’s goals to peak carbon emission and achieve carbon neutrality. In this paper, 115 resource-based cities with abundant natural resources in China were studied, and spatial analysis techniques such as LISA (Local Indicators of Spatial Association) time path and spatial-temporal transition were used to explore their spatial divergence pattern and spatio-temporal evolution characteristics of carbon emission intensity from 2000 to 2019, while geodetector model was used further to reveal their drivers and impacts on the environment. It is found that 1) the carbon emission intensity of resource-based cities shows a significant decreasing trend, with significant differences in carbon emission intensity and its decreasing rate in different development stages and resource-type cities. The overall trend of growing cities, declining cities, mature cities and regenerating cities decreases in order. The carbon emission intensity of cities in the energy, forest industry, general, metal and non-metal categories gradually decrease. The spatial pattern of carbon emission intensity has strong stability, with an overall spatial distribution of high in the north and low in the south. 2) The spatial structure of carbon emission intensity in resource-based cities has strong stability, dependence and integration, with the stability gradually increasing from north to south and the path dependence and locking characteristics of the carbon emission intensity pattern slightly weakened. 3) The spatial divergence of carbon emission intensity in resource-based cities is the result of the action of multiple factors, among which the level of financial investment, urban economic density, urban population density, urban investment intensity and energy use efficiency are the dominant factors. 4) The leading drivers of carbon emission intensity are different in cities at different development stages and with various resources, and grasping the characteristics of carbon emission intensity changes and drivers of various resource-based cities can better provide targeted countermeasures for resource-based cities to achieve carbon emission reduction targets and sustainable development.
Xinyu Wu, , Zhongming Ding
Frontiers in Environmental Science, Volume 10; https://doi.org/10.3389/fenvs.2022.973438

Abstract:
There is increasing evidence that European Union allowance (EUA) futures return distributions exhibit features of time-varying higher moments (skewness and kurtosis), which plays an important role in modeling and forecasting EUA futures volatility. Moreover, a number of studies have shown that time-varying risk aversion (RA) contains useful information for forecasting EUA futures volatility. In light of this, this paper proposes the GARCH-MIDAS with skewness and kurtosis (hereafter GARCH-MIDAS-SK) to empirically investigate the impact and predictive role of RA on EUA futures volatility. Our empirical results show that RA has a significantly negative impact on the long-term volatility of EUA futures. The EUA futures return distributions exhibit obvious features of time-varying higher moments. Incorporating RA and time-varying higher moments improves the in-sample fitting of the model. Furthermore, out-of-sample results suggest that incorporating RA and time-varying higher moments leads to significantly more accurate volatility forecasts. This finding is robust to alternative out-of-sample forecasting windows.
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