Environmental Problems Research Articles

Enzyme-Immobilized Porous Crystals for Environmental Applications.

Developing efficient technologies to eliminate or degrade contaminants is paramount for environmental protection. Biocatalytic decontamination offers distinct advantages in terms of selectivity and efficiency; however, it still remains challenging when applied in complex environmental matrices. The main challenge originates from the instability and difficult-to-separate attributes of fragile enzymes, which also results in issues of compromised activity, poor reusability, low cost-effectiveness, etc. One viable solution to harness biocatalysis in complex environments is known as enzyme immobilization, where a flexible enzyme is tightly fixed in a solid carrier. In the case where a reticular crystal is utilized as the support, it is feasible to engineer next-generation biohybrid catalysts functional in complicated environmental media. This can be interpreted by three aspects: (1) the highly crystalline skeleton can shield the immobilized enzyme against external stressors. (2) The porous network ensures the high accessibility of the interior enzyme for catalytic decontamination. And (3) the adjustable and unambiguous structure of the reticular framework favors in-depth understanding of the interfacial interaction between the framework and enzyme, which can in turn guide us in designing highly active biocomposites. This Review aims to introduce this emerging biocatalysis technology for environmental decontamination involving pollutant degradation and greenhouse gas (carbon dioxide) conversion, with emphasis on the enzyme immobilization protocols and diverse catalysis principles including single enzyme catalysis, catalysis involving enzyme cascades, and photoenzyme-coupled catalysis. Additionally, the remaining challenges and forward-looking directions in this field are discussed. We believe that this Review may offer a useful biocatalytic technology to contribute to environmental decontamination in a green and sustainable manner and will inspire more researchers at the intersection of the environment science, biochemistry, and materials science communities to co-solve environmental problems.

A systematic review of invasive non-native freshwater bivalves.

The introduction of invasive species has become an increasing environmental problem in freshwater ecosystems due to the high economic and ecological impacts it has generated. This systematic review covers publications from 2010 to 2020, focusing on non-native invasive freshwater bivalves, a particularly relevant and widespread introduced taxonomic group in fresh waters. We collected information on the most studied species, the main objectives of the studies, their geographical location, study duration, and type of research. Furthermore, we focused on assessing the levels of ecological evidence presented, the type of interactions of non-native bivalves with other organisms and the classification of their impacts. A total of 397 publications were retrieved. The studies addressed a total of 17 species of non-native freshwater bivalves; however, most publications focused on the species Corbicula fluminea and Dreissena polymorpha, which are recognised for their widespread distribution and extensive negative impacts. Many other non-native invasive bivalve species have been poorly studied. A high geographical bias was also present, with a considerable lack of studies in developing countries. The most frequent studies had shorter temporal periods, smaller spatial extents, and more observational data, were field-based, and usually evaluated possible ecological impacts at the individual and population levels. There were 94 publications documenting discernible impacts according to the Environmental Impact Classification for Alien Taxa (EICAT). However, 41 of these publications did not provide sufficient data to determine an impact. The most common effects of invasive bivalves on ecosystems were structural alterations, and chemical and physical changes, which are anticipated due to their role as ecosystem engineers. Despite a considerable number of studies in the field and advances in our understanding of some species over the past decade, long-term data and large-scale studies are still needed to understand better the impacts, particularly at the community and ecosystem levels and in less-studied geographic regions. The widespread distribution of several non-native freshwater bivalves, their ongoing introductions, and high ecological and economic impacts demand continued research. Systematic reviews such as this are essential for identifying knowledge gaps and guiding future research to enable a more complete understanding of the ecological implications of invasive bivalves, and the development of effective management strategies.

Heavy metals removal from industrial wastewater of Biskra (Algeria) by Arundo donax and Phragmites australis.

Industrial effluents pose a serious environmental problem, because they contain toxic contaminants mainly heavy metals that are the most dangerous to humans, animals, plants, and the environment in general. Phytoremediation using macrophytes is an adopted technique for the environment decontamination due to its efficiency and cost-effectiveness. The present study aims to highlight the capabilities of macrophytes to remove heavy metals from wastewater of Biskra region (Algeria). The methodology consists of filling out the filters planted with Arundo donax and Phragmites australis with raw industrial wastewater, then recovering decontaminated water after 15 days to assess removal of lead, copper, zinc, and iron. Both plants had shown a good efficiency for the removal of metals loaded in wastewater eliminating about 94 to 98% of initial concentration. In addition, calculated bioaccumulation factor (BAF) had confirmed the accumulation of heavy metals in different parts of experimental plants; recorded values of BAF > 1 allowed the consideration of Arundo donax and Phragmites australis as good hyper-accumulator plants. Obtained results confirm the efficiency of phytoremediation technology using macrophytes for the wastewater treatment in particular and the environment decontamination in general.

Removal of calcium and magnesium ions from reverse osmosis concentrate using a two-stage precipitation with carbonation process.

The reverse osmosis (RO) technique has been extensively employed in the advanced treatment of industrial water and wastewater. However, this process results in the production of a significant quantity of reverse osmosis concentrate (ROC), which contains high levels of salinity and organic contaminants, thereby posing serious environmental problems. This study reported a two-stage precipitation process utilizing quicklime (CaO) and caustic soda (NaOH) in conjunction with air blowing (carbonation) for the removal of Ca2+ and Mg2+ from real brackish water ROC of factory. In stage I, the CaO precipitation-carbonation process was employed to eliminate the majority of Ca2+ from the ROC, while leaving Mg2+ virtually unaffected, yielding high-purity CaCO3 precipitates. In stage II, the NaOH precipitation method was utilized to eliminate the remaining Ca2+ and Mg2+ from the ROC. It was demonstrated that under optimal conditions, the removal rates of Ca2+ and Mg2+ exceeded 97%. Finally, the characterization of precipitates demonstrated the generation of high-purity CaCO3 precipitates in stage I, as well as the formation of CaCO3 and Mg(OH)2 precipitates in stage II. The results confirmed the feasibility of employing the two-stage precipitation with carbonation process to economically treat ROC and enable its reuse, offering valuable insights for the treatment of industrial wastewater.

Microplastics in Granular Sequencing Batch Reactors: Effects on Pollutant Removal Dynamics and the Microbial Community

This study investigated the relationship between microplastic (MP) presence and pollutant removal in granular sludge sequencing batch reactors (GSBRs). Two types of MPs, polyethylene (PE) and polyethylene terephthalate (PET), were introduced in varying concentrations to assess their effects on microbial community dynamics and rates of nitrogen, phosphorus, and organic compound removal. The study revealed type-dependent variations in the deposition of MPs within the biomass, with PET-MPs exhibiting a stronger affinity for accumulation in biomass. A 50mg/L dose of PET-MP decreased COD removal efficiency by approximately 4% while increasing P-PO4 removal efficiency by around 7% compared to the control reactor. The rate of nitrogen compounds removal decreased with higher PET-MP dosages but increased with higher PE-MP dosages. An analysis of microbial activity and gene abundance highlighted the influence of MPs on the expression of the nosZ and ppk1 genes, which code enzymes responsible for nitrogen and phosphorus transformations. The study also explored shifts in microbial community structure, revealing alterations with changes in MP dose and type. This research contributes valuable insights into the complex interactions between MP, microbial communities, and pollutant removal processes in GSBR systems, with implications for the sustainable management of wastewater treatment in the presence of MP. Environmental implicationThe presence of microplastics (MPs) in wastewater is a major environmental concern. Our research shows that MPs not only accumulate in biomass but also interfere with the efficiency of wastewater treatment processes in granular sludge aerobic reactors (GSBR). This highlights the hazardous nature of MPs, as they affect the dynamics of pollutant removal and microbial community activity. Understanding these interactions is critical to addressing the environmental problems posed by MP in wastewater treatment systems. By identifying the effects of MP on GSBR performance, our work helps development of strategies to mitigate their negative effects and thus improve the effectiveness of wastewater treatment processes.

Synergistic role of phenylpropanoid biosynthesis and citrate cycle pathways in heavy metal detoxification through secretion of organic acids

Excessive heavy metal contaminants in soils have serious ecological and environmental impacts, and affect plant growth and crop yields. Phytoremediation is an environmentally friendly means of lowering heavy metal concentrations in soils. In this study, we analyzed phenotypic and physiological traits, and the transcriptome and metabolome, of sheepgrass (Leymus chinensis) exposed to cadmium (Cd), lead (Pb), or zinc (Zn). Phenotypic and physiological analysis indicated that sheepgrass had strong tolerance to Cd/Pb/Zn. Transcriptomic analysis revealed that phenylpropanoid biosynthesis and organic acid metabolism were enriched among differentially expressed genes, and metabolomic analysis indicated that the citrate cycle was enriched in response to Cd/Pb/Zn exposure. Genes encoding enzymes involved in the phenylpropanoid and citrate cycle pathways were up-regulated under the Cd/Pb/Zn treatments. Organic acids significantly reduced heavy metal accumulation and improved sheepgrass tolerance of heavy metals. The results suggest that synergistic interaction of the phenylpropanoid and citrate cycle pathways in sheepgrass roots induced organic acid secretion to alleviate heavy metal toxicity. A cascade of enzymes involved in the interacting pathways could be targeted in molecular design breeding to enhance phytoremediation. Environmental implicationThe excessive content of heavy metals in soil has become an increasingly serious environmental problem. Sheepgrass as the edificator has promise for phytoremediation of heavy-metal-contaminated soils. Phenotypic and physiological analysis showed that sheepgrass had strong tolerance to Cd/Pb/Zn. Omics analysis indicated that synergistic role of the phenylpropanoid and citrate cycle pathways in sheepgrass roots induced organic acid secretion to alleviate the toxicity of heavy metals. The findings may be beneficial for the future application of herbaceous plants for phytoremediation of soils contaminated with heavy metals, and improvement in alleviating the effects of heavy metal toxicity on plants.

Aloe vera mucilage loaded gelatin electrospun fibers contained in polylactic acid coaxial system and polylactic acid and poly(e-caprolactone) tri-layer membranes for tissue engineering.

Polymeric electrospun mats have been used as scaffolds in tissue engineering for the development of novel materials due to its characteristics. The usage of synthetic materials has gone in decline due to environmental problems associated with their synthesis and waste disposal. Biomaterials such as biopolymers have been used recently due to good compatibility on biological applications and sustainability. The purpose of this work is to obtain novel materials based on synthetic and natural polymers for applications on tissue engineering. Aloe vera mucilage was obtained, chemically characterized, and used as an active compound contained in electrospun mats. Polymeric scaffolds were obtained in single, coaxial and tri-layer structures, characterized and evaluated in cell culture. Mucilage loaded electrospun fibers showed good compatibility due to formation of hydrogen bonds between polymers and biomolecules from its structure, evidenced by FTIR spectra and thermal properties. Cell viability test showed that most of the obtained mats result on viability higher than 75%, resulting in nontoxic materials, ready to be used on scaffolding applications. Mucilage containing fibers resulted on materials with potential use on scaffolding applications due to their mechanical performance and cell viability results.

Project-based methodology for English language learning in High School

High School students in Ecuador's Fiscal Educational Units have not developed skills in the English foreign language, nor can they recognize environmental problems and contribute with an effective and efficient solutions to them. The application of active communication methodologies such as project-based learning can help solve the problem together with the use of technology, thus contributing to the practice of oral skills to present innovative proposals for a specific project that can be sustainable over time. It is evident the lack of active methodological practices in the country's fiscal institutions, added to the little control in the educational establishments of the application of this type of tools that promote teamwork, hinders the improvement of the quality of education, especially in the subject of English. It is necessary to follow up on the teaching performance and the application of this methodology to generate new challenges in the educational area, especially in high school students, and complete their exit profile successfully in the English language. An article template and instructions on the editorial process and the text, figure, and references format are provided. The approach of this study is qualitative with a descriptive scope of the content for which the previous bibliography on the proposed topic is used, making a review of the literature on the project-based methodology (MBP) and its influence on the development of oral communication in the English language in the students.

Institutional Obstacles and Countermeasures to Improve the Chinese Ocean Carbon Sink Trading Market

Global climate change is a great challenge shared by human society today. All countries are actively carrying out carbon emissions trading to cope with increasingly serious environmental problems. Ocean carbon sink trading is an important part of the carbon emissions trading market and has become a new academic hot spot. It is urgent to construct an ocean carbon sink trading mechanism that meets China’s national conditions. The goal of this study is to determine how to improve China’s ocean carbon sink trading market using research methods such as normative analysis, comparative analysis, and case studies. The study shows that there are outstanding problems, such as unclear property rights and imperfect relevant laws and regulations, in the Chinese ocean carbon sink trading market. In order to solve these problems, the property rights of ocean carbon sinks should be clarified, relevant laws related to ocean carbon sinks and the trading market should be improved, and construction of a financial system for ocean carbon sinks should be further developed. At the same time, it is necessary to strengthen the supervision of ocean carbon sink trading and encourage the public to actively participate. According to the results of the study, there is a long way to go towards improving China’s ocean carbon sink trading market, requiring the joint efforts of the government, market, society, and public in making greater contributions in the response to global climate change.

Accumulation analysis and overall measurement to represent airborne toxic metals with passive tree bark biomonitoring technique in urban areas.

Authorities have long proved the utility of bioindicators in monitoring the state of environmental pollution. Some biological indicators can measure environmental pollutant levels, and many tree species have been tested for suitability for monitoring purposes. The differences in morphological characteristics in the trees have demonstrated the effects of human activities on different materials. Measuring bark and wood biomass from contaminated sites was identified and directly compared with those from a clean site or areas characterized by distinct contamination sources. However, preliminary results demonstrate the approach's potential in the realization of strategies for disease control and promoting health to reduce environmental and health inequalities in at-risk urban areas. Picea orientalis L. and Cedrus atlantica Endl., especially their bark, can be regarded as a more robust storage of Cu (37.95 mg/kg) and Mn (188.25 mg/kg) than Pinus pinaster, Cupressus arizonica, and Pseudotsuga menziesii, which and is therefore a better bioindicator for Cu and Mn pollution. Considering the total concentrations as a result of the study, the pollution is thought to be caused by environmental problems and traffic in the region. The deposition of Cu, Mn, Ni, and Zn elements was found P. menziesii (60, 443, 58, and 258 mg/kg) and P. orientalis (76, 1684, 41, and 378 mg/kg) and seems to reflect atmospheric quite clearly compared to P. pinaster, C. arizonica, and C. atlantica. Ni and Zn concentrations have significantly increased since 1983, and P. menziesii and P. orientalis can be potentially valuable bioindicators for emphasizing polluted fields.

Education for sustainable development: comparative analysis and prospects at universities in Kazakhstan, Tajikistan, Kyrgyzstan and Uzbekistan

The study, conducted in higher education institutions in Kazakhstan, Tajikistan, Kyrgyzstan and Uzbekistan, highlights ongoing changes in approaches to education for sustainable development (ESD) in Central Asian countries. This region, exposed to various challenges such as climate change and environmental problems, has recognized the importance and role of education in achieving sustainable development. The study aims to identify the current level of awareness of students and teachers about the Sustainable Development Goals, as well as to understand how universities in the region are integrating ESD principles into their educational programs.The results show that students generally have limited knowledge about the global sustainable development goals, while teachers have a higher level of awareness. Most students receive information about the sustainable development goals (SDGs) through social media and the Internet, while it is less reflected in the curriculum. However, there is a trend towards changing this situation, in particular in Tajikistan, where curricula are becoming more focused on environmental education.Finally, recommendations for universities include integrating ESD principles into teacher development, developing teaching methods and materials, and strengthening collaboration at the regional and international levels to promote sustainable development goals.

Location Selection Methods for Urban Terminal Co-Distribution Centers with Air–Land Collaboration

Urban terminal logistics and distribution enterprises face the problems of duplicated network layouts, high costs, and inefficient urban environments. Recently, collaborative distribution using unmanned aerial vehicles (UAVs) and ground vehicles has been considered as a means of reducing costs and enhancing efficiency, thus overcoming the issues created by the high-density layout of enterprises’ relatively independent networks. This essentially involves constructing an air–ground collaborative common distribution network. To optimize the economic cost and distribution time of network operations, we established a site selection planning model for air–ground cooperative urban co-distribution centers and designed a solution method based on gray wolf optimization with K-means clustering. Taking the Wangsheren area of Jinan City, China, as an example, 15 UAV co-distribution centers and 13 vehicle co-distribution centers were identified. Although the average distribution cost of the network rose by 35–50% compared to traditional terminal distribution, the time saving was 80–85%, greatly improving the high-value-added service capacity. The end-distribution efficiency and customer satisfaction were also enhanced, which fully verifies the feasibility, validity, and applicability of the proposed model. Our approach can be applied to landing sites and the planning and optimization of large-scale commercial operations using logistics UAVs in urban areas.

Olive stone powder filled bio-based polyamide 5.6 biocomposites: biodegradation in natural soil and mechanical properties

AbstractThe extensive use of non-biodegradable and petroleum derived polymers in industry exacerbates environmental problems associated with plastic waste accumulation and fossil resource depletion. The most promising solution to overcome this issue is the replacement of these polymers with biodegradable and bio-based polymers. In this paper, novel biocomposites were prepared from bio-based polyamide 5.6 (PA56) with the addition of olive stone powder (OSP) at varying weight concentrations by melt compounding method. The degradability of the prepared biocomposites is investigated through soil burial test, and assessed by reduction in their mechanical properties. The biodegradability of bio-based polyamide 5.6 is shown to be improved by addition of olive stone powder, and its effects on the properties of polymer matrix are elucidated. The Fourier transform infrared (FTIR) spectrum of the biocomposites indicate the successful incorporation of OSP into PA56 polymer matrix. After six-month soil burial test, scanning electron microscopy and FTIR show the degradation of PA56 through morphological and structural changes, respectively. Differential scanning calorimetry reveals the changes in the transition temperatures of the polymer matrix and an increase in crystallinity. Thermogravimetric analysis is used on the biocomposite to determine the fraction of its components, polymer and biofiller, and the results show that 2.67% (w/w) of the polyamide 5.6 is biodegraded at the end of the six-month soil burial.

Meeting expectations? Response of policy innovation labs to sustainable development goals

Abstract Introduced by the United Nations, Sustainable Development Goals (SDGs) aim at facilitating inclusive sustainable development. Responsiveness to SDGs is considered a key to addressing pressing development problems. The current literature focuses on the responsiveness of varied public organizations to SDGs, whereas SDGs’ responsiveness of policy innovation labs (PILs) is understudied. Aiming to address both persistent and emerging social and environmental problems, PILs are aligned with SDGs. On the other hand, PILs seek innovative ways to generate policy solutions in collaboration with citizens through experimental methods and thus are more committed to the local public rather than international organizations. This paper investigates to what extent and in what way PILs respond to SDGs during policy formulation processes, both implicitly and explicitly. Data draws on a database the authors developed, identifying 211 European PILs. Thematic coding of PILs’ websites reveals that 62.1% of the PILs implicitly promote at least one SDG. Additionally, sustainable cities and communities (SDG11) and good health and well-being (SDG3) are the two SDGs with the highest implicit-response rates, respectively. We apply grounded theory analysis from semi-structured interviews with senior PIL employees of 31 PILs to gauge their explicit views of SDGs. This inductive approach reveals three dimensions to SDGs: levels of responsiveness, different practices, and considerations that guide PILs on whether to comply with SDGs. A better understanding of PILs’ response to SDGs provides a more nuanced portrayal of PILs as organizations aiming to craft innovative policy solutions that align with international frameworks.

Effect of recycled concrete aggregate size on physical and mechanical properties of eco-friendly-self-compacting concrete

In recent years, the rapid increase in population and building demand across the world leads to significant deterioration or reduction of natural resources. Meanwhile the huge amounts of waste from the demolition of buildings and concrete structures in the landfill space become a serious ecological and environmental problem. The recovery of aggregates from recycled concrete for the formulation of new concrete would contribute to reducing the depletion of natural resources and therefore integrate into the context of sustainable development, because there are several socio-economic advantages. The objective of this possibility of using aggregates from recycled concrete mixes. We have established a comparison between the physical and mechanical behavior of SCC based on RCA (Recycled Sand: SR 0/3 and Recycled Gravel RG: 3/8 and 8/15) and that of SCC based on natural aggregates (NA) on fresh support and hardened state. Additionally, Non-Destructive Testing (NDT) methods were conducted in this research to obtain more information about the properties of the studied SCC. The results of the tests on fresh SCC meet the recommendations of the French Association of Civil Engineering (AFGC). The physical and mechanical behavior of SCC-RS is relatively weak compared to SCC-NA/RG. This is directly related to the high absorption capacity of the aggregates (depending on the size of the aggregates) and the poor quality of the mortar attached to the aggregates, which can create areas of weakness in the concrete structure. From the regression results, it was found that there is a direct correlation between the physical and mechanical properties of different concretes indicated by the higher values of R-squared (R2 = 0.92).

Confidence level based complex polytopic fuzzy Einstein aggregation operators and their application to decision-making process

A complex Polytopic fuzzy set (CPoFS) extends a Polytopic fuzzy set (PoFS) by handling vagueness with degrees that range from real numbers to complex numbers within the unit disc. This extension allows for a more nuanced representation of uncertainty. In this research, we develop Complex Polytopic Fuzzy Sets (CPoFS) and establish basic operational laws of CPoFS. Leveraging these laws, we introduce new operators under a confidence level, including the confidence complex Polytopic fuzzy Einstein weighted geometric aggregation (CCPoFEWGA) operator, the confidence complex Polytopic fuzzy Einstein ordered weighted geometric aggregation (CCPoFEOWGA) operator, the confidence complex Polytopic fuzzy Einstein hybrid geometric aggregation (CCPoFEHGA) operator, the induced confidence complex Polytopic fuzzy Einstein ordered weighted geometric aggregation (I-CCPoFEOWGA) operator and the induced confidence complex Polytopic fuzzy Einstein hybrid geometric aggregation (I-CCPoFEHGA) operator, enhancing decision-making precision in uncertain environments. We also investigate key properties of these operators, including monotonicity, boundedness, and idempotency. With these operators, we create an algorithm designed to solve multiattribute decision-making problems in a Polytopic fuzzy environment. To demonstrate the effectiveness of our proposed method, we apply it to a numerical example and compare its flexibility with existing methods. This comparison will underscore the advantages and enhancements of our approach, showing its efficiency in managing complex decision-making scenarios. Through this, we aim to demonstrate how our method provides superior performance and adaptability across different situations.

Iracema program: sustainability in distance education

With the change in the means of production since the Industrial Revolution, man starts to cause increasing impacts to the environment, since the means of production are no longer handcrafted to be machines that use steam energy from the burning of fossil fuels - initially coal. These impacts have been discussed since the 1970s at United Nations (UN) events that aim to achieve global cooperation in search of solutions to environmental problems. Research has shown that the key to sustainability is education and that it is necessary to prepare young people to work within a sustainable culture. In this sense, this work is a descriptive research with a qualitative approach that sought to promote environmental awareness in the municipalities where the UFRPE distance education centers are located, through the involvement of a program called “IRACEMa”. With regard to the axes worked on by the project, such as selective collection, and the proper use of resources such as plastic cups, it was verified that there is still an insufficient commitment between the research subjects. Thus, it is clear that actions of this nature must be strengthened in order to foster environmental awareness in distance education centers.

Environmental Behaviour of Synthesized and Commercial Agricultural Zinc Products: Leaching, Migration, and Availability in Soils

AbstractThe aim of this paper is to examine the environmental effect of different chemical characteristics of Zinc (Zn) sources, assessing the transport, leaching and accumulation in the environment in sand, acidic (AS) and calcareous (CS) soils. Comparative short- and long-term studies applying ZnO sources [bulk, laboratory-synthesized and commercial nanoparticles (NP)], ZnSO4, complexed Zn (Zn-lignosulfonate) and chelated Zn (Zn-diethylenetriamine-pentaacetate, Zn-hydroxy-ethylenediamine-tetraacetate and Zn-ethylenediamine-tetraacetate) were carried out. For all treatments and media, the medium- and long-term dissolution kinetic model was fitted to a logistic function. The applied Zn in the form of ZnO was mainly retained at the upper half (0–7.5 cm) of the columns and in very available form (ranging 40–61% of added Zn in AS and 29–31% in CS). Leached Zn reached values below 6% in AS and 3% in CS. The use of chelated Zn in both soils and complexed Zn, and ZnSO4 in AS resulted in excessive leaching of Zn (around 70%). The amount of Zn available at the upper half of the column was less than 5%. In the CS, these fertilizers showed a higher aging than ZnO sources, negatively affecting its availability as a nutrient for crops. ZnO NP showed short- and medium-term dissolution kinetics that allow gradual nutrient release and high availability at the medium-term. These products provide an effective solution for plant nutrition while mitigating the environmental problems observed with more traditional sources related to leaching. Graphical Abstract

Biofilms on Plastic Debris and the Microbiome

Plastic pollution has become a global environmental problem, and the large number of microorganisms attached to plastic debris in the environment has become a hot topic due to their rapid response to pollutants and environmental changes. In this study, we used high-throughput sequencing to investigate the microbial community structure of and explore the metagenome in the biofilm of two types of plastic debris, polystyrene (PS) and polyethylene terephthalate (PET), and compared them with a water sample collected at the sampling site. The phylum Proteobacteria dominated both the PET and PS samples, at 93.43% and 65.95%, respectively. The metagenome data indicated that the biofilm is enriched with a number of hydrocarbon (petroleum, microplastics, etc.) degrading genes. Our results show that the type of plastic determined the bacterial community structure of the biofilm, while the environment had relatively little effect.

Energy, environmental, and economic analysis of novel R744/R290 cascade refrigeration systems designed for warm ambient conditions utilizing ejector

There is a growing global awareness about the need to reduce total carbon equivalent emissions and other environmental problems caused due to synthetic refrigerants. The study utilizes cascade refrigeration systems (CRS) with R744 in the low-temperature circuit and R290 in the high-temperature circuit. Two evaporators are present in the LTC; one is direct expansion (DX) type at −40 °C with a cooling load of 70 kW, and other is gravity-fed evaporator at −25 °C with 60 kW cooling load. The study aims to enhance the performance and economic and environmental impact of CRS by incorporating parallel compression (PC) in LTC, a gravity-fed evaporator, and an ejector in HTC. The performance is compared to a baseline CRS system using a flash-gas bypass arrangement (FGB) in the LTC, bypassing generated flash gas to compressor suction. PC in LTC removes flash gas from receiver pressure to cascade condenser pressure in the first suggested CRS. While the second proposed CRS (PCEJ) employs an ejector in HTC over and above PC in LTC. The CRSs demonstrate significant higher COP of 1.43, 1.58 and 1.65, leading to an improvement upto 62.4 %, 79 %, and 86 % over the reference HFC-404A system at 45 °C ambient temperature. SEER analysis also establishes higher year-round efficiency compared to reference HFC-404A by 22 %, 36 %, and 44 %. The total TEWI of FGB, PC, and PCEJ is 43.1 %, 53.2 %, and 53.5 % lower compared to the reference system, indicating substantial potential for lowering global warming when implemented. Economic analysis brings out relative cost comparisons under various measures.