Hasil untuk "Environmental engineering"

B. Logan, B. Hamelers, R. Rozendal et al.

G. Aiken, Heileen Hsu-Kim, J. Ryan

Stephen Ryan

The typical cost analysis of an environmental regulation consists of an engineering estimate of the compliance costs. In industries where fixed costs are an important determinant of market structure this static analysis ignores the dynamic effects of the regulation on entry, investment, and market power. I evaluate the welfare costs of the 1990 Amendments to the Clean Air Act on the US Portland cement industry, accounting for these effects through a dynamic model of oligopoly in the tradition of Ericson and Pakes \citeyearpar{pakes-ericson:95}. Using a recently developed two-step estimator, I recover the entire cost structure of the industry, including the distribution of sunk entry costs and adjustment costs of investment. I find that the Amendments have significantly increased the sunk cost of entry. I solve for the Markov perfect Nash equilibrium (MPNE) of the model and simulate the welfare effects of the Amendments. A static analysis misses the welfare penalty on consumers, and obtains the wrong sign on the welfare effects on incumbent firms

Jian‐Gan Wang, F. Kang, B. Wei

Marc A. Fernandez-Yague, S. Abbah, L. McNamara et al.

J. Wilson, Cecil Piya, Y. Shin et al.

M. Portman, Asya Natapov, D. Fisher-Gewirtzman

Jesús Gracia-Sánchez, Oscar Arturo Fuentes-Mariles, Judith Ramos

En algunos canales revestidos con pendientes altas es muy común que ocurran fuertes socavaciones y erosión, así como desbordes, por lo que se requiere una regulación de las velocidades del flujo de agua. Una opción para lograrlo es aumentar significativamente la rugosidad del fondo mediante la instalación de estructuras hidráulicas rápidas. Sin embargo, en fluidos con sedimentos, el cambio de velocidad genera la deposición de sólidos, los cuales podrían consolidarse, cambiando el diseño geométrico de estas estructuras. Este estudio tiene como objetivo estimar el grado de confianza esperado cuando se producen modificaciones en las geometrías de rugosidad artificial en el fondo del canal con flujo turbulento y densidad de fluido. Esta modificación modifica barras transversales en rampas con base en un análisis matemático experimental. El estudio permite concluir que la rugosidad del fondo generada provoca flujos de agua más estables y es una forma de reducir las velocidades de flujo.

Ibraheem Hassan I., Al-Mmosawe Hasan

Hot weather conditions increase the thermal conductivity of asphalt pavements, causing heat-related damages. Reducing thermal accumulation in pavement structures is essential to improve durability and service life. This study examines the thermal and mechanical performance of asphalt mixtures modified with crumb rubber (CR) via the dry process. Twelve modified mixtures with 1%, 3%, and 5% CR were prepared using four particle sizes (0.3 mm, 2.36 mm, 4.75 mm, and blended), along with an unmodified control mix. Thermal conductivity was measured using the QTM-500 device, while mechanical properties were evaluated via the Marshall method, including stability, flow, air voids, and voids filled with asphalt (VFA). Statistical analysis using ANOVA and Tukey HSD validated the results. Thermal conductivity decreased with higher CR content, reaching 0.4619 W/m.K at 5% CR with blended gradation – a 59.4% reduction from the baseline of 1.1389 W/m.K. Marshall stability peaked at 1% CR (14.446 kN) but declined at higher CR levels due to increased air voids, affecting compatibility. With blended gradation and 2%–3% CR, both insulation and mechanical integrity improved. In hot climates, CR use enhances thermal performance, promotes tire recycling, and offers cost-efficient pavement solutions.

Rawadee Meeprasit, Sujaree Bureekul, Suriyan Saramul

This study investigated the sedimentological characteristics of the Bang Berd-Khao Tham Thong beach system, which is located along the western shore of the central Gulf of Thailand, an area that is minimally disturbed by human activity and is ideal for studying natural coastal processes. Sediment samples were collected from both coastal and marine environments across four sampling periods (July 2022, September 2022, April 2023, and June 2023). The analysis focused on the grain size distribution, sorting, skewness, kurtosis, and sediment composition, revealing a predominance of medium sand in coastal sediments and increased silt and clay contents in marine sediments. The largest sediment particle size is 466.78 microns. Coastal sediments show a well-sorted size distribution, with a mesokurtic kurtosis. In contrast, sediment samples collected from the marine environment exhibit a poorly sorted size distribution, with leptokurtic kurtosis. Most sediment samples also have symmetrical skewness. Coastal sediments displayed characteristics of tidal influence, with some southern coastal areas exhibiting desert-like conditions due to wind action. The marine sediments were a mixture of shallow marine and fluvial depositional environments. Linear discriminant functions and the CM diagram were used to classify the sediment accumulation environments, identifying four main depositional modes: rolling, rolling and suspension, suspension and rolling and graded suspension. These findings contribute to a deeper understanding of sediment transport and accumulation processes in coastal and marine environments, with implications for coastal management and climate change adaptation strategies.

Laura Nistor, Cătălin Lisa, Tsuyoshi Michinobu et al.

Background: 2-[4-(Dimethylamino)phenyl]-3-([4-(dimethylamino)phenyl]ethynyl)buta-1,3-diene-1,1,4,4-tetracarbonitrile (DDMEBT) is a thermally robust organic material of interest for applications requiring controlled volatility. Understanding its thermal stability, decomposition mechanism, and sublimation behavior is critical for optimizing deposition conditions in industrial processes. Methods: A comprehensive set of techniques was employed, including thermogravimetric analysis coupled with mass spectrometry and FTIR spectroscopy (TG/MS/FTIR), differential scanning calorimetry (DSC), ATR-FTIR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), dynamic vapor sorption (DVS) analysis, polarized light microscopy (POM), and molecular modeling. Sublimation kinetics were investigated under isothermal conditions (130–150 °C) using anthracene as reference. Significant findings: DDMEBT exhibits a sequential three-step degradation mechanism, independent of heating rate, with high thermal stability (final residue ∼77 %) attributed to its nonplanar architecture and intermolecular π–π/dipole–dipole interactions. Thermal analysis revealed melting at ∼190 °C, structural rearrangements (196–230 °C), and an amorphous-to-crystalline transition at 270 °C. Sublimation proceeds via zero-order kinetics with low volatility (0.178 μg/min at 130 °C) and an activation energy of 66.5 kJ/mol. The determined vapor pressure (1998–4000 Pa) and transport coefficients confirm a thermally activated, hydrodynamically stable process. These findings establish a reliable basis for sublimation modeling and provide guidelines for optimizing material processing in high-temperature, low-volatility applications.

Lixia Feng, Qilong Bian, Shujun Wu et al.

Abstract Arsenic contaminants exist in different chemical forms with varying toxicity and mobility, making on-site analysis challenging. Here, a fluorogenic method is developed for the efficient detection of arsenite and arsenate ions using a portable platform directly in an aqueous phase. During sensing, the aggregation-induced emission (AIE) probe TPE-Cys/TPE-2Cys exhibits low fluorescence when dissolved, but reacts with the As(III) to form organic arsenic complexes with low solubility, inducing a turn-on fluorescence for quantitative analysis. Using a prior reduction strategy, the As(V) can be converted to As(III) and further analyzed in a sequential detection. Using a specialized laser-induced fluorescence instrument, this strategy allows on-site analysis of As(III) and As(V) species with sensitivity down to 0.14 ppb in environmental samples, showing that As(III) dominates while the As(V)/As(III) ratio varies in a constitutional equilibrium. The system has potential for the practical analysis of complex arsenic, revealing the dynamic arsenic transformations in the environment.

Nan Sun, Nan Sun, Yuxin Wang et al.

IntroductionThis study adopted the intercropping pattern opepper (Capsicum annuum L.) and Chinese chives (Allium tuberosum), combined with high-throughput sequencing and microbial network analysis, to systematically reveal the mechanisms of intercropping on the structural regulation and functional synergy of the crop rhizosphere microbiome and root-stem endophyte communities.MethodsThree treatments were set up: blank control, solo cultivation, and intercropping.Combined with high-throughput sequencing and network analysis, the reorganization patterns of rhizosphere and endophyte communities were systematically analyzed.ResultsIntercropping induced differential responses of microbial communities in the two crops: it significantly increased the bacterial α-diversity in Chinese chives leaves, and the Shannon index of pepper roots also showed an upward trend, while the microbial diversity in pepper rhizosphere soil was inhibited. In contrast, among roots, the “pepper intercropped with Chinese chives” group had the highest total number of OTUs and the largest number of unique OTUs. Microbial communities exhibited cross-host transfer characteristics: the migration rate of microbial communities from pepper roots to Chinese chives rhizosphere reached 46.57%, and 69.54% of the microbial communities in Chinese chives roots originated from pepper roots. Specifically, Aureimonas and Sphingomonadaceae were significantly enriched in pepper leaves, the relative abundance of Pantoea in Chinese chives leaves increased by 11.5 times, and the abundance of Flavobacterium in pepper rhizosphere increased by 94%. Microbial co-occurrence network analysis confirmed the optimization of functional synergy: the proportion of positive interactions in pepper leaves increased to 90.45%, and the negative interactions of Bradyrhizobium decreased by 97%, the proportion of positive interactions of functional bacteria in Chinese chives rhizosphere reached 88.96%, and Bacillus enhanced positive connections while maintaining an abundance of 10.23%–20.87%, the number of positive interactions of Streptomyces in pepper rhizosphere doubled. Network stability showed spatial variation: the robustness of stem microbial networks was significantly improved, while the vulnerability of rhizosphere microbial networks increased.DiscussionThis study provides microbial theoretical support for the intercropping system to optimize nitrogen utilization by driving pepper to enrich the growth-promoting bacteria Sphingomonadaceae, and to enhance disease resistance by promoting Chinese chives to recruit the biocontrol bacteria Bacillus, thereby forming a microecological regulation mechanism with functional complementarity.

Yi-Wei Zhao, Li-Li Du, Bing Hu et al.

Nitrous oxide (N2O) emissions from the wastewater treatment sector are a significant contributor to global greenhouse gas levels. This investigation delves into the mechanisms of N2O generation and uptake, correlating microbial processes with variables such as influent characteristics and operational parameters. The nature of carbon substrates in the influent profoundly influences microbial consortia and N2O output. Elevating the carbon-to-nitrogen (C/N) ratio has been shown to curtail N2O emissions by alleviating the competitive dynamics among denitrifying enzymes. Optimal activity of N2O reductase is achieved by maintaining a neutral to mildly alkaline pH and stable ambient temperatures. It is imperative to circumvent extreme aeration rates and prolonged aeration periods to reduce N2O release. The study underscores the importance of an effective carbon feed strategy and advocates for prolonged hydraulic retention times (HRT) and sludge retention times (SRT) in activated sludge suspension systems to inhibit N2O escape. Notably, excessive internal recycling, coupled with heightened dissolved oxygen (DO) levels in aerobic zones, intensifies N2O emission risks. Moreover, the presence of hazardous contaminants, such as heavy metals and antibiotics, interferes with nitrogen elimination processes, warranting a comprehensive assessment of consequent N2O emission hazards. This research provides a scientific basis as well as practical management approaches to diminish N2O emissions.

Tamer M. Tamer, Wagih Abdel-Alim Sadik, Rafik Abbas Elady et al.

The Methyl orange (MO) azo dye has been removed from dyes-contaminated wastewater for the first time using a novel amino-ethyl Chitosan crosslinked hydrogel (CS-ENH2). The induced amine groups served as positive charge centers to bind MO azo-dye anions. The MO adsorbents' capabilities in comparison to native Chitosan (CS) are directly correlated positively with the amination phase which a very rapid initial adsorption was seen in the first 60 min, then began to slow until it leveled off after 120 min and 180 min for CS and CS-ENH2. The adsorption temperature has a positive effect, particularly at low temperatures, between 25 °C and 30 °C, where the adsorption capacity of the CS-ENH2 is double that of the CS, while at higher temperatures that effect diminished. The kinetics, isotherms, and thermodynamics characteristics of the MO adsorption process were followed. The obtained results showed that the MO adsorption process adhered to the pseudo-second-order kinetic model, the Langmuir isotherm model, and had an endothermic and spontaneous character with a maximum adsorption Langmuir monolayer of 3.66 and 10.53 mg/g for CS and CS-ENH2. In conclusion, the CS-ENH2 adsorbent removed up to 2.86 folds of MO amount of that removed using Chitosan under the same operating conditions, which reflected in the reduction of the used adsorbent amount, adsorption time, and finally proved the cost-effective of the developed CS-ENH2 adsorbent.

Ziba Moravej, Gholamali Haghighat, Aboubakr Jafarnezhad et al.

Background: Childhood hypertension can have serious consequences for children, especially during their adulthood. This study aimed to determine the prevalence of hypertension and its related factors in children aged 7 to 12 years in Larestan (Iran). Methods: In this cross-sectional study, 1110 students from 7 to 12 years old in Larestan were enrolled in the study using cluster sampling. In order to collect educational data, 10 girls' primary schools and 10 boys' primary schools were randomly selected from all the girls' and boys' primary schools. Then, considering that each school has different number of students, 55 students of each school were randomly selected. Students' blood pressure was measured as standard. Their personal information was also recorded in a checklist. A checklist containing demographic information, factors and variables that affect the prevalence of hypertension in children aged 7 to 12 years was used. To collect information, a checklist was used that included demographic information such as age, gender, and place of residence. Also, in order to identify factors and variables effective in the prevalence of high blood pressure (HBP), tools such as sphygmomanometer and other risk factors including obesity, type of diet, physical activities, and body mass index (BMI) were used. Results: The mean age of girls was 9.11 ± 1.53 and boys were 9.19 ± 1.52, which did not differ significantly from the statistical point of view. The prevalence of pre hypertension was 6.03% (95% CI: 4.71-7.60) and the prevalence of hypertension was 4.14% (95% CI: 3.05-5.49). Systolic and diastolic blood pressure has direct relation with height and weight of children. Diastolic blood pressure also had a higher prevalence in girls (P < 0.001). Conclusion: Overweight and obesity as a moderate aggressive factor were significantly associated with blood pressure. Also, the prevalence of HBP in children was significant, and it is necessary to pay attention to it in childhood. Moreover, hypertension cases should be identified and treatment should start faster for the affected person to prevent the adverse consequences in the future.

R. Jiang, G. Zhang, S. Wang et al.

<p>A lightning location system consisting of multiple ground-based stations is an effective means of lightning observation. The dataset from CNLDN (China National Lightning Detection Network) in 2016–2022 is employed to analyze the temporal and spatial lightning distributions and the differences between <span class="inline-formula">+</span>CG (positive cloud-to-ground lightning) and <span class="inline-formula">−</span>CG (negative cloud-to-ground lightning) strokes in China. On the annual scale, lightning activity is most prevalent during the summer months (June, July, and August), accounting for 72.6 % of the year. Spring sees more lightning than autumn, and winter has only a small amount in southeastern coastal areas. During the day, the frequency of lightning peaks at 15:00–17:00 CST (China standard time) and is lowest at 8:00–10:00 CST. For the period with high CG stroke frequency (summer of a year or afternoon of a day), the proportion of <span class="inline-formula">+</span>CG strokes and the discharge peak current are relatively small. Winter in a year and morning or midnight in a day correspond to a greater <span class="inline-formula">+</span>CG stroke proportion and discharge current. Spatially, low latitudes, undulating terrain, the seaside, and humid surfaces are favorable factors for lightning occurrence. Thus, the southeast coastland has the largest lightning stroke density, while the northwest deserts and basins and the western and northern Tibetan Plateau, with altitudes over 6000 m, have almost no lightning. The proportion of <span class="inline-formula">+</span>CG strokes and the peak current are low in the southern region with high density but diverse in other regions. The Tibetan Plateau causes the diversity of lightning activity in China and lays the foundation for studying the impact of surface elevation on lightning. Results indicate that the <span class="inline-formula">+</span>CG stroke proportion on the eastern and southern Tibetan Plateau is up to 15 %, larger than the plain regions. The peak current of <span class="inline-formula">−</span>CG strokes is positively correlated with altitude, but <span class="inline-formula">+</span>CG strokes show a negative correlation, resulting in a large difference in peak current between <span class="inline-formula">+</span>CG and <span class="inline-formula">−</span>CG on the plain and a small difference on the plateau.</p>

Soyoun Kim, Yejin Hyeon, Chanhyuk Park

Ubiquitous microplastics in urban waters have raised substantial public concern due to their high chemical persistence, accumulative effects, and potential adverse effects on human health. Reliable and standardized methods are urgently needed for the identification and quantification of these emerging environmental pollutants in wastewater treatment plants (WWTPs). In this study, we introduce an innovative rapid approach that employs flow imaging microscopy (FlowCam) to simultaneously identify and quantify microplastics by capturing high-resolution digital images. Real-time image acquisition is followed by semi-automated classification using customized libraries for distinct polyethylene (PE) and polystyrene (PS) microplastics. Subsequently, these images are subjected to further analysis to extract precise morphological details of microplastics, providing insights into their behavior during transport and retention within WWTPs. Of particular significance, a systematic investigation was conducted to explore how the presence of natural organic matter (NOM) in WWTPs affects the accuracy of the FlowCam’s measurement outputs for microplastics. It was observed that varying concentrations of NOM induced a more curled shape in microplastics, indicating the necessity of employing pre-treatment procedures to ensure accurate microplastic identification when utilizing the FlowCam. These observations offer valuable new perspectives and potential solutions for designing appropriate treatment technologies for removing microplastics within WWTPs.

Luan Luong Chu, Hanhong Bae

Ginseng has been well-known as a medicinal plant for thousands of years. Bacterial endophytes ubiquitously colonize the inside tissues of ginseng without any disease symptoms. The identification of bacterial endophytes is conducted through either the internal transcribed spacer region combined with ribosomal sequences or metagenomics. Bacterial endophyte communities differ in their diversity and composition profile, depending on the geographical location, cultivation condition, and tissue, age, and species of ginseng. Bacterial endophytes have a significant effect on the growth of ginseng through indole-3-acetic acid (IAA) and siderophore production, phosphate solubilization, and nitrogen fixation. Moreover, bacterial endophytes can protect ginseng by acting as biocontrol agents. Interestingly, bacterial endophytes isolated from Panax species have the potential to produce ginsenosides and bioactive metabolites, which can be used in the production of food and medicine. The ability of bacterial endophytes to transform major ginsenosides into minor ginsenosides using β-glucosidase is gaining increasing attention as a promising biotechnology. Recently, metabolic engineering has accelerated the possibilities for potential applications of bacterial endophytes in producing beneficial secondary metabolites.

M. Umar, K. Kassim, K. T. P. Chiet

Abstract The concept of using biological process in soil improvement which is known as bio-mediated soil improvement technique has shown greater potential in geotechnical engineering applications in terms of performance and environmental sustainability. This paper presents a review on the soil microorganisms responsible for this process, and factors that affect their metabolic activities and geometric compatibility with the soil particle sizes. Two mechanisms of biomineralization, i.e. biologically controlled and biologically induced mineralization, were also discussed. Environmental and other factors that may be encountered in situ during microbially induced calcite precipitation (MICP) and their influences on the process were identified and presented. Improvements in the engineering properties of soil such as strength/stiffness and permeability as evaluated in some studies were explored. Potential applications of the process in geotechnical engineering and the challenges of field application of the process were identified.