Global Environmental Issues Research Articles

Global Air Quality Enhancement Pathways to Health Benefits and Environmental Justice

Nowadays, air pollution has emerged as a critical global health and environmental justice issue, with a stark contrast in exposure and management between high-, middle-, and low-income countries. This study synthesizes satellite-derived data with Global Burden of Disease insights, examining the spatiotemporal trends of PM2.5 and O3 exposures and their health impacts from 1998 to 2019. Despite a reversal in the global upward trend of PM2.5 exposure post-2011, O3 levels persist, highlighting a geographical disparity in health benefits due to air quality policies. The study reveals that while a reduction in indoor PM2.5 pollution has led to significant health gains, the rise in outdoor PM2.5 and O3 pollution continues to escalate the global death toll. The research underscores the urgent need for tailored governance strategies to address the primary pollution conditions in various income-level regions, advocating for environmental justice and equality. The findings suggest that targeted air pollution management could not only mitigate the health risks but also enhance life expectancy, emphasizing the potential for substantial health benefits through improved air quality regulations.

Adsorption Properties of Fishbone and Fishbone-Derived Biochar for Cadmium in Aqueous Solution

Cadmium (Cd) contamination in aquatic ecosystems is a serious global environmental issue. Biochar derived from agricultural wastes has recently attracted remarkable attention as it is used as an absorbent in combating heavy metal contamination of water bodies. In the present study, the absorption efficacy of fish bone (FBM) and fishbone-derived biochar prepared at 200 °C, 400 °C, 600 °C, and 800 °C (referred to as B200, B400, B600, and B800, respectively) for the Cd ion (Cd2+) in aqueous solution was investigated. The results showed that high-temperature pyrolysis could optimize the pore structure and specific surface area of FBM, and Cd2+ successfully adsorbed onto FBM and fishbone-derived biochar. High-temperature pyrolysis significantly increased the FBM adsorption capacity for Cd2+ by 49.5–135.1%, with the optimal pyrolysis temperature being 600 °C. Furthermore, the kinetic data of FBM and fishbone-derived biochar for Cd2+ were in better alignment with the pseudo-second-order model, their adsorption isotherms were better in accordance with the Langmuir models, and the thermodynamic analysis showed that the adsorption process was monolayer and favorable adsorption. Moreover, the potential adsorption mechanisms of Cd2+ on FBM and fishbone-derived biochar might be related to pore filling, ion exchange, complexation with oxygen functional groups, and precipitation with the minerals on the biochar surface. Fishbone-derived biochar has significant potential for wastewater treatment and agricultural waste applications.

Engaged Amazigh Poetry in Meteor Airlines' "Agdal": Reviving Tradition while Addressing Global Environmental Issues

This paper analyzes Meteor Airlines' 2024 album Agdal, which revitalizes traditional Amazigh poetry through the emerging genre of Amazigh Rock. The study aims to explore how Agdal integrates the cultural heritage of pre-Saharan Amazigh oasis communities into global environmental discussions, with an emphasis on preserving nomadic and pastoral traditions. Using a qualitative analysis of the album’s lyrics, music style, and its reception, this research examines how the album marks a shift in Morocco's cultural industry from commercialized music production to efforts centered on cultural preservation and archiving. Findings suggest that Agdal, by merging traditional Amazigh poetry with contemporary rock elements, engages transnational audiences and contributes to an ongoing global dialogue on ecological and cultural sustainability. The study concludes that contemporary Amazigh music plays a crucial role in preserving historical memory, fostering cultural resilience, and raising environmental awareness, illustrating the impact of local cultural production on wider global issues

Freshwater salinisation: unravelling causes, adaptive mechanisms, ecological impacts, and management strategies.

Freshwater salinisation is a growing problem worldwide, affecting surface and groundwater resources. Compared with other global environmental issues, freshwater salinisation has been studied extensively in North America, Australia, and Europe but less so in South America, Asia, and Africa. Both the natural and anthropogenic sources can contribute for freshwater salinisation, through the concentration of dissolved salts in water rising above its normal levels. This review provides a comprehensive assessment of the causes of freshwater salinisation, the impacts on freshwater communities and ecosystem functions, the adaptive mechanisms for survival in an increasingly saline environment, and the management strategies available to control freshwater salinisation. Many human activities contribute to freshwater salinisation, including road salt use, agricultural practices, resource extraction, reservoir construction, and climate change. Aquatic organisms have evolved mechanisms to survive in increasingly saline environments, but excessive salinity can lead to mortality and non-lethal effects. Such effects can have cascading impacts on the structure and function of aquatic communities and ecosystem services. Therefore, monitoring programmes and chemical fingerprinting are needed to identify highly salinised areas, determine how various human activities contribute to freshwater salinisation, and implement management strategies. Furthermore, current research on freshwater salinisation has been limited to a few regions of the world. It is essential to expand the research further into exploring the impacts of salinisation on freshwater resources in unexplored geographic areas of the world that are mainly impacted by climate change scenarios.

Current Advances in the Photoconversion of Plastics: the Catalysts and Reaction Pathways.

Plastic waste has caused severe global environmental pollution and health issues due to the high production rate and lack of proper disposal technology. Traditional methods to deal with plastic waste, such as incineration and landfilling, are deemed unsustainable and energy-intensive. A promising alternative is the photocatalytic conversion of plastic waste, using sunlight as a sustainable and carbon-neutral energy source to break down plastic waste under ambient pressure and low temperatures. This review aims to provide a comprehensive summary of recent advancements in plastic photoconversion, with an emphasis on the catalysts and reaction pathways. The mechanisms and reaction pathways are first summarized, followed by a detailed discussion of strategies to design catalysts for improved performance in photoconversion. Then, examples of photothermal degradation processes are presented. Finally, current strategies, challenges, and possible future directions of plastic photoconversion are summarized and discussed.

Analysis of Decoupling Effects and Influence Factors in Transportation: Evidence from Guangdong Province, China

In recent years, global environmental issues have become increasingly prominent. The transportation industry, as the fundamental sector of national economic development, is also characterized by high energy consumption and carbon emissions. Therefore, it is imperative to conduct research on the carbon emission problem within this industry. In light of the Tapio decoupling model, an analysis of the correlation between traffic carbon emissions and economic development in Guangdong province during 1999–2019 was carried out. With the aim of encouraging Guangdong province’s low-carbon transportation development, the factors affecting the transportation industry are analyzed utilizing the generalized Divisia index model (GDIM). We also introduced passenger and freight turnover as an influencing factor for analysis. The findings indicate that (1) Guangdong province’s traffic carbon emissions increased from 1999 to 2019; (2) the traffic carbon emissions’ decoupling effect is mainly “weakly decoupled”, and the overall decoupling effect is not strong in Guangdong province; (3) among the traffic carbon emissions’ factors, the effects of the production value of traffic and the turnover volume are at the forefront, and the effect of turnover volume has gradually exceeded the production value of traffic in recent years. The suppression of the intensity of carbon emissions is relatively large, while the suppression of the intensity of energy consumption and transport is relatively weak. Based on this, strategies were proposed to promote a cleaner energy mix, improve energy use efficiency, create energy savings, develop green technologies, and foster the restructuring of transportation.

Analysis of landscape vegetation ecology and cellular structure in nature reserves based on an improved analytic hierarchy process

With the increasing severity of global environmental issues, natural reserves have become crucial areas for maintaining biodiversity and protecting natural ecosystems. The ecological status of landscape vegetation and the characteristics of cellular structures within these reserves have become focal points of research. However, traditional evaluation methods have limitations when dealing with the complex ecosystems of natural reserves, making it difficult to assess the relationship comprehensively and accurately between vegetation ecology and cellular structures. Therefore, this paper proposes an analysis of landscape vegetation ecology and cellular structure in natural reserves based on an improved Analytic Hierarchy Process (AHP). By incorporating fuzzy set theory and expert scoring mechanisms, the evaluation process is enhanced in terms of objectivity and precision. An evaluation index system for landscape vegetation ecology and cellular structure in natural reserves is constructed, covering aspects such as vegetation species richness, community structural complexity, and ecological functional stability. This systematic approach reflects the ecological status of vegetation and cellular structure characteristics, providing scientific support for targeted protection and management measures.

Monitoring, simulation and early warning of cyanobacterial harmful algal blooms: An upgraded framework for eutrophic lakes

Cyanobacterial Harmful Algal Bloom (CyanoHAB) is a global aquatic environmental issue, posing considerable eco-environmental challenges in freshwater lakes. Comprehensive monitoring and accurate prediction of CyanoHABs are essential for their scientific management. Nevertheless, traditional satellite-based monitoring and process-oriented prediction methods of CyanoHABs failed to satisfy this demand due to the limited spatiotemporal resolutions of both monitoring data and prediction results. To address this issue, this paper proposes an upgraded framework for comprehensive monitoring and accurate prediction of CyanoHABs. A collaborative CyanoHAB monitoring network was firstly constructed by integrating space, aerial, and ground-based monitoring means. As a result, CyanoHAB conditions were assessed frequently covering the entire lake, its key areas, and core positions. Furthermore, by overcoming technical limitations associated with high-precision simulation of the growth-drift-accumulation process of CyanoHABs, such as the unclear drifting process of CyanoHABs and the mechanism of its coastal accumulation, the multi-scale CyanoHAB prediction was realized interconnecting the entire lake and its nearshore areas. The implemented framework has been applied in Lake Chaohu for over three years. It provided high-frequency and high-spatial-resolution CyanoHAB monitoring, as well as its multi-scale and accurate simulation. The application of this framework in Lake Chaohu had significantly improved the accuracies of CyanoHAB monitoring, simulation, and early warning. This advancement holds significant scientific value and offers potential for CyanoHAB prevention and control in eutrophic lakes.

Analyzing Consumer Motivations and Behaviors Towards Upcycled Food from an Environmental Sustainability Perspective

Green energy consumption is a pressing global environmental issue that necessitates the optimization of food system circularity to effectively utilize natural resources. The rise of food technology has introduced upcycled food as a promising solution for reducing food waste and promoting sustainability. Despite its potential, research on consumer attitudes toward upcycled food remains scarce. This study investigates the role of upcycled food in shaping Taiwanese consumers’ behaviors in response to environmental challenges, utilizing the value–attitude–behavior (VAB) model with a focus on variables such as “product novelty”, “green perceived value”, and “ethical consumption”. Using convenience sampling, 297 valid responses were collected, achieving a response rate of 91.1%. Findings indicate that health values significantly enhance positive attitudes toward upcycled food, which in turn positively influences behavioral intentions. However, neither green perceived value nor product novelty significantly affected these intentions. These insights highlight the importance of prioritizing health values, consumer attitudes, and ethical consumption in marketing strategies for upcycled food to engage potential consumers and promote environmental sustainability. This study addresses a critical gap in the existing literature and suggests a strategic direction for the food industry.

Mapping Biodiversity Conservation Priorities for Protected Areas for Spatial Optimization: A Case Study in the Songnen Plain, China.

The decline in biodiversity poses a serious threat to natural ecosystems and has become one of the most pressing global environmental issues. Establishing conservation priorities for protected areas (PAs) is one of the most direct and effective biodiversity conservation measures. However, conservation gaps arise as a result of existing problems in spatial layout of PAs, including overlapping protection scopes, artificial fragmentation of natural ecological regions, as well as "over-protection" and "over-exploitation." To optimize the spatial layout of PAs and improve the efficiency of biodiversity conservation, we employed the Habitat Quality module of the Integrated Assessment of Ecosystem Services and Tradeoffs (InVEST) model and the Maximum Entropy (MaxEnt) model to assess the PAs in the Songnen Plain, China. The combined model (MaxEnt-InVEST) revealed that the conservation priorities for PAs in the Songnen Plain occupied a total area of 14,764.14 km2 (10.24% of the total area of the Songnen Plain). The conservation priorities outside PAs occupied a total area of 7858.45 km2 (5.45% of the total area of the Songnen Plain) and were primarily distributed in the northeastern, central, and southwestern regions of the Songnen Plain. This indicated that existing PAs did not offer adequate protection for local biodiversity. The consistency of our combined modeling framework was 72.11%, which enabled a more accurate assessment of biodiversity hotspots and respects the land uses of the Songnen Plain. In addition, the modeling framework successfully created maps of conservation gaps of biodiversity hotspots based on actual species distribution data and considers current land uses. Our study was aimed at optimizing the spatial conservation efficiency of the Songnen Plain by assessing the conservation gaps in the Songnen Plain. It could provide a reference for the future development of a PA system centering on national parks.

Biosorption of Pb2+, Cd2+ and Zn2+ from aqueous solutions by Agrobacterium tumefaciens S12 isolated from acid mine drainage

Heavy metal pollution is a global environmental issue, and microorganisms play a crucial role in the bioremediation of heavy metal-contaminated wastewater. The study isolated heavy metal-resistant bacterium and observed their absorption ability toward Pb2+, Cd2+ and Zn2+. We isolated Agrobacterium tumefaciens S12 from acid mine drainage. The various factors influencing its adsorption performance, including pH, biomass dosage, initial metal ion concentration, and adsorption temperature, were investigated in detail. Chemisorption controls the adsorption rate due to the results better fitted by pseudo-second order kinetics. The maximum adsorption capacities of Pb2+, Cd2+ and Zn2+ on A. tumefaciens S12 were 234, 58 and 51 mg g−1 at 30 °C from Langmuir isotherm, respectively. The adsorption processes for the three heavy metal ions were spontaneous and exothermic in nature. In bimetallic systems, biosorption of Pb2+ ions was preferential to that of Cd2+ and Zn2+. Furthermore, scanning electron microscopy coupled to energy dispersive spectroscopy, Fourier-transform infrared spectra and X-ray photoelectron spectroscopy analysis demonstrated that the adsorption mechanisms include ion-exchange, complexation interaction between the heavy metal ions and the functional groups on the surface of biomass. The obtained results indicated that A. tumefaciens S12 can be applied as an efficient biosorbent in bioremediation technology to sequestrate heavy metal ions from aqueous solution.

Engineering Study of Erosion to Protect the Gometseri Alazani and Pirikiti Alazani Catchment Area (Kakheti region, Akhmeta municipality, Tusheti)

Soil erosion is a global environmental issue that reduces soil productivity, affects water quality, leads to sediment deposition, and increases the likelihood of agricultural land degradation. Combating erosion requires both quantitative and qualitative assessment of potential soil erosion on specific sites, along with knowledge of local terrain, soil types, land use systems, and management practices. From a theoretical and practical point of view, erosion processes are widespread and dangerous in Georgia, especially in mountainous areas. Slopes that have not been eroded or have not formed ravines are rare. Intensive landslides and mudslides are also observed here. Changes in factors associated with erosion are of interest, including the impact of climate change and human activity on components of erosional geosystems, especially on soil cover. Modern geoinformation systems (GIS) provide qualitatively new opportunities for research, modelling and optimization of the use of erosion-prone lands. Despite its wide application in many spheres of human activity, its potential in erosion research has not yet been fully realized. This article discusses about the Gometseri Alazani and Pirikiti Alazani (Akhmeta Municipality, Tusheti) catchment areas. The erosion-landslide processes developed in the research area are studied using the Revised Universal Soil Loss Equation (RUSLE). Erosion-vulnerable areas have been identified, where it is necessary to carry out additional engineering protection measures.

Physicochemical and toxicological characteristics of leachates and water quality around dumpsites in Lagos Nigeria

Improper waste management leading to contamination of groundwater resources is a global environmental issue. This study examined the physicochemical and toxicological characteristics of leachates and their effect on water quality around the dumpsite in Alimosho Lagos, Nigeria. Samples of water and leachates were collected from boreholes around the dumpsite. Physiochemical and toxicological characterization of water around the dumpsite was based on American Public Health Association standards. Seventeen physiochemical and heavy metals of leachate and borehole water samples were analysed. The result of the study shows that the temperature, odour, appearance and turbidity of the water in the study area were within the limits set by WHO. However, the pH was below the WHO limits indicative of the acidity of the groundwater. The presence of Pb, Cr, and Cd confirmed leachate pollution. The contemporary effects confirmed the insignificant effect of the dumpsite operations at the groundwater source. Without a properly designed leachate series system, uncontrolled accumulation of leachates at the bottom of the dumpsite poses capacity infection dangers to groundwater resources. It is recommended that proper disposal of waste, in addition to implementing a higher sustainable environmental sanitation practice, is needed to ensure the safety of groundwater within the locality.

AuAg plasmonic nanoalloys with asymmetric charge distribution on CeO2 nanorods for selective photocatalytic CO2‐to‐CH4 conversion

AbstractConverting CO2 under mild conditions by employing semiconductor photocatalysts is promising to address global environmental issues. However, the current CO2 conversion efficiency is limited by the difficulty activating the thermodynamically stable CO2 molecules. Constructing plasmonic nanoalloy‐based photocatalytic systems with significant localized surface plasmon resonance (LSPR) is full of potential but remains a vast challenge. In this work, AuAg plasmonic nanoalloys were incorporated on CeO2 nanorods (designated as AuAg–CeO2) to achieve selective photoreduction of CO2. The result displays that Ag can serve as a superior electron modifier to promote the electron enrichment of Au, thus producing asymmetric charge distributions to boost the selective conversion of CO2. Furthermore, the improved LSPR effect on AuAg–CeO2 induces the generation of high‐energy hot electrons under irradiation, enhancing the reactivity of electrons for CO2 photoreduction. Due to the aforementioned effects, AuAg–CeO2 exhibits a high CO2‐to‐CH4 performance of 92.6 μmol g−1 through a 3‐h test and a high CH4 selectivity of 94.5%, up to 2.6, 8.7, and 17.1 times higher than the activity of Au–CeO2, pure CeO2, and Ag–CeO2, respectively. This work can provide a new perspective for constructing high‐performance catalysts for photocatalytic CO2 reduction.

Market Reaction to ESG Information Disclosure A Case Study of Midea Group

Abstract: As global environmental issues become increasingly severe, investors are paying more attention to corporate sustainability. They realize that focusing solely on financial performance is insufficient; a company's environmental, social, and governance (ESG) performance must also be considered. In China, with the goal of carbon neutrality highlighting the importance of ESG, concepts such as ESG investment, reporting, and rating are flourishing. Corporate ESG actions are becoming a new focal point for investors. This paper takes the ESG information disclosure of Midea Group as a case study, using an event study model to explore the stability of the companys stock price and the variation in its returns during the event window, thus analyzing the market's short-term reaction to ESG information. The study finds that the ESG reports issued by Midea Group have a positive impact on the stock market to some extent, significantly reducing stock price volatility and inducing a positive trend in abnormal returns.

Development of modified MgO/biochar composite for chemical adsorption enhancement to cleanup fluoride-contaminated groundwater

Fluoride contamination in groundwater has become a global environmental issue. Magnesium oxide (MgO) has demonstrated effectiveness as an adsorbent in treating fluoride pollution in groundwater. However, its use in powder and fine granular form often results in losses during the adsorption process, posing challenges for post-treatment recovery and potentially causing secondary environmental pollution. In this study, two novel fluoride adsorbents [rice husk (RH) and spent coffee grounds (SCG)-based magnesium oxide (MgO) biochar composites (MgO/RH and MgO/SCG)] were developed to cleanup fluoride-polluted groundwater. During the adsorbent synthesis process, RH and SCG biochar were pyrolyzed at 500 °C and modified by calcination using MgO. Both MgO/RH and MgO/SCG surfaces exhibited abundant pore structures and formed MgO crystal phases. Batch experiments results show that when the MgO/RH and MgO/SCG material dosages were 1 g/L, fluoride removal rates reached 80% and 86% respectively. The isotherms and kinetics of fluoride adsorption with MgO/RH and MgO/SCG followed the Langmuir isotherm equation and pseudo-second-order kinetic model. The maximum fluoride adsorption capacities of MgO/RH and MgO/SCG were 63.47 mg/g and 141.98 mg/g, respectively, indicating these materials used mono-layer adsorption mechanism for fluoride adsorption. The addition of MgO into the pores of porous adsorbent materials effectively increased their reactive sites and enhanced the adsorption performance of carbon materials. Particularly, SCG biochar had a richer pore structure than RH biochar, providing a larger contact surface area, facilitating the effective dispersion and doping of MgO into the pores. Therefore, MgO/SCG composite exhibited excellent fluoride adsorption properties in water, indicating the potential for developing a new type of MgO-modified SCG adsorbent material with green prospects. This composite effectively mitigated fluoride contamination, reducing the fluoride concentration in groundwater. Both RH and SCG are agricultural and food waste by-products, thus offering the opportunity to significantly reduce production, operation, and maintenance costs.

Examining the Causal and Heterogeneous Influence of Three-Dimensional Urban Forms on CO2 Emissions in 285 Chinese Cities

Despite the efforts to examine the influence of urban forms on CO2 emissions, most studies have mainly measured urban forms from a two-dimensional perspective, with relatively little attention given to three-dimensional urban forms and their causal relationships. Utilizing the built-up area dataset from the Global Human Settlement Layer (GHSL) project and the carbon emission dataset from the China City Greenhouse Gas Working Group (CCG), we examine a causal and heterogeneous effect of three-dimensional urban forms on CO2 emissions—specifically urban height, density, and intensity—in 285 Chinese cities. The empirical results reveal a robust and positive causal effect of 3D urban forms on carbon emissions. Even when incorporating the spatial spillover effect, the positive effect of 3D urban forms remains. Moreover, GDP per capita and total population have a greater impact on urban CO2 emissions. Additionally, we find that the influence of 3D urban forms on CO2 emissions is U-shaped, with total population serving as a moderating factor in this effect. Importantly, there is significant geographic and sectoral heterogeneity in the influence of 3D urban forms on CO2 emissions. Specifically, the influence of 3D urban forms is greater in eastern cities than in non-eastern cities. Furthermore, 3D urban forms primarily influence household carbon emissions rather than industrial and transportation carbon emissions. Therefore, in response to the growing challenges of global climate change and environmental issues, urban governments should adopt various strategies to develop more rational three-dimensional urban forms to reduce CO2 emissions.

The Rise of Green Trade Policy and Its Impact on the International Market

With the increasing severity of global environmental issues, governments and international organizations are gradually recognizing the key role of green trade policies in promoting environmental sustainability. Green trade policies aim to facilitate a green transition in global trade through the formulation and implementation of environmental protection measures. These policies include carbon pricing mechanisms, green tariffs, environmental subsidies, and international coordination of environmental standards. This paper systematically analyzes the definition and development of green trade policies and explores their impact on the international market. The main content covers the reshaping of international trade flows and patterns, changes in global competitive dynamics, and the optimization and adjustment of global supply chains. The study reveals that green trade policies not only drive increased demand for eco-friendly products and technologies in the international market but also reshape global competitive dynamics and promote the greening and smart transformation of global supply chains. In the future, with the further refinement of green trade policies and strengthened international cooperation, the global economy is expected to achieve more sustainable development.

Stress Response of Aphid Population Under Combined Stress of Cadmium and Lead and Its Effects on Development of Harmonia axyridis.

Heavy metal pollution is a serious global environmental issue. It threatens human and ecological health. Heavy metals can accumulate in the soil over extended periods and inevitably transfer through the food chain to herbivorous insects and their natural enemies, leading to various adverse effects. This study aimed to investigate the stress responses and biochemical metabolic changes of aphids and one of aphids' predators, ladybugs, under cadmium (Cd) and lead (Pb) stress by constructing a food chain of Vicia faba L., Megoura crassicauda, and Harmonia axyridis. The results showed that aphids and ladybugs had a notable accumulation of Cd2+ and Pb2+. Insects can adapt to heavy metal stress by regulating their energy metabolism pathways. Glycogen content in the first filial generation (F1) aphids decreased significantly, glucose content in the second filial generation (F2) to the fourth filial generation (F4) adult aphids significantly increased, and trehalose content in the F1 adult aphids increased significantly. Moreover, the relative expression levels of trehalase (TRE) and trehalose-6-phosphate synthase (TPS) in the F1 adult aphids were significantly higher than those in the control group, and the expression levels of TPS genes in the second filial generation to the fifth filial generation (F2 to F5) aphids decreased, suggesting that insects can resist heavy metal stress by regulating trehalose metabolism. The fertility of female aphids in all treatment groups was reduced compared to the control group. Additionally, the relative expression level of vitellogenin (Vg) was down-regulated in all aphid generations except the F1 aphids. There was interaction between heavy metal concentration and aphid generation, and it significantly affected the number of aphids' offspring and the expression of the aphid Vg gene. The developmental duration of the ladybugs from the second to fourth instars was prolonged, and the weight decreased significantly from the prepupa to the adult stages. These results contribute to understanding the effects of Cd2+-Pb2+ accumulation on phytophagous insects and higher trophic levels' natural enemies, laying the foundation for protecting natural enemies and maintaining ecosystem stability.

Unraveling the synergistic interplay of sulfur and wheat straw in heterotrophic-autotrophic denitrification for sustainable groundwater nitrate remediation

Nitrate pollution in groundwater is a global environmental issue that poses significant threats to human health and ecological security. This study focuses on elucidating the mechanisms of heterotrophic-autotrophic cooperative denitrification (HAD) by employing wheat straw and elemental sulfur as electron donors in varying proportions. The research initially underscores that heterotrophic denitrification (HD) accelerates the denitrification process due to its high-energy metabolism. However, as readily degradable organic matter diminished, reliance on more complex substrates such as lignocellulose posed a challenge to HD. This marks a pivotal transition towards autotrophic denitrification (AD), which, despite a slower initial rate, exhibits a more sustained denitrification performance. A low proportion of heterotrophic denitrification layer (e.g., 3:1) at the bottom facilitating efficient and sustainable denitrification. HD is capable of simultaneous removal of nitrates and nitrites, whereas AD demonstrates a higher affinity for nitrates, with nitrite accumulation reaching 100% at high influent nitrate concentrations (100 mg/L). HD not only provides the necessary alkaline environment for AD but also reduces sulfate production, whereas AD utilizes the residual organic carbon and ammonia produced by HD. The heterotrophic layer is characterized by a diverse community, whereas the autotrophic layer is predominantly composed of Thiobacillus. By delineating the interactive mechanisms and characteristics of HAD, this study highlights the importance of balancing heterotrophic and autotrophic activities for the effective remediation of groundwater nitrates.