Search Results (84)

The coal-fired Plomin Thermal Power Plant (Plomin TPP) in Croatia is located in the center of the east coast of the Istrian peninsula (northern Adriatic) and is considered the main source of historical air pollution in the region. Between 1970 and 2000, sulfur-rich coal from the local Raša coal mine was primarily used. In this study, a screening of content and fate of TPP-derived sulfur in soil around the power plant was made two decades after the S-rich coal was banned from use. Soil samples were collected at varying distances from the TPP in the prevailing wind direction (NE), along with a control sample taken more than 10 km away. The samples were analyzed for total sulfur, sulfate, organic sulfur (humic and fulvic), and the stable isotope composition of total sulfur (δ³⁴S). Additionally, coal and coal ash were analyzed for total sulfur, sulfate and δ³⁴S. Soil sampling along the prevailing wind direction from the Plomin TPP revealed markedly elevated sulfur content, with levels at 100 m downwind reaching up to 4 wt.%, which is over 100 times higher than the 0.04 wt.% measured at the control site located upwind. Sulfur content decreases sharply with increasing distance from the TPP, reflecting the deposition gradient along the prevailing wind path. Speciation analysis showed that over 95% of the sulfur in the soil is now present in organic form, mainly bound to humic acids. The δ³⁴S_VCDT values of the bulk coal used in the TPP ranged from −10.0 to −5.0‰. In most soil samples, the bulk δ³⁴S values were positive (+7.0 to +20.0‰). The values of sulfate in soil range from +1.0 to +5.5‰, while those in organic sulfur range from −3.5 to +6.0‰. This indicates that atmospheric deposition of ³⁴S-depleted fly ash and sulfate from coal are the most important sulfur sources, while some of the sulfur in the soil is also of marine origin. Finally, we showed that natural attenuation was a significant and efficient process within the sustainable management of the site historically contaminated by anthropogenic atmospheric sulfur deposition. Full article

Road dust resuspension is widely recognized as a major contributor to traffic-related particulate matter (PM) in urban environments. Nevertheless, reported emission factors exhibit substantial variability. These discrepancies stem not only from the intrinsic complexity of the resuspension process but also from limitations in measurement techniques, which often fail to adequately control or characterize the influencing parameters. As a result, the contribution of each parameter remains difficult to isolate, leading to inconsistencies across studies. This study presents an experimental protocol developed to quantify PM10 and PM2.5 emission factors associated with vehicle-induced road dust resuspension. Experiments were conducted on a dedicated test track seeded with alumina particles of controlled mass and size distribution to simulate road dust. A network of microsensors was strategically deployed at multiple upwind and downwind locations to continuously monitor particle concentration variations during vehicle passages. Emission factors were derived through time integration of the mass flow rate of resuspended dust measured by the sensor network. The estimated PM10 emission factor showed excellent agreement, within 2.5%, with predictions from a literature-based formulation, thereby validating the accuracy and external relevance of the proposed protocol. In contrast, comparisons with U.S. EPA formulas and other empirical equations revealed substantially larger discrepancies, particularly for PM2.5, highlighting the persistent limitations of current modeling approaches. Full article

With the rapid expansion of urban areas, short naturally ventilated traffic tunnels (NVTTs) have become prevalent in modern cities. However, their enclosed design and inadequate ventilation often lead to the accumulation of vehicle emissions, especially during peak traffic periods, which poses significant threats to public health. Previous studies have shown that airflow in such tunnels is caused by ambient crosswinds (ACWs), which contribute to the dilution of pollutants. Based on this, a geometrical model including traffic tunnels belonging to a complex traffic system of the Second Ring Road in Wuhan City was established, followed by a mathematical model describing the fluid flow and pollutant transformation. The current flow characters and pollutant dispersion mechanism of CO and NO_X were analyzed. Among them, the number and speeds of vehicles are measured to calculate the strength of the pollutant source. Then, the data was set as the initial contaminant source strength in Ansys Fluent 14.0 to compute the pollutant dispersion of the whole domain. The results indicate the following: (1) The airflow direction inside the tunnel varies with changes in ambient wind direction and wind speed. Specifically, variations in ambient wind direction result in changes in airflow direction in both tunnels. In contrast, changes in wind speed do not affect the airflow direction in both tunnels; only in the downstream tunnel does the airflow direction change with increasing westward wind speed. By comparison, in the upstream tunnel, the airflow direction remains unchanged regardless of the westward wind speed; (2) Pollutant accumulates along the downstream airflow in both the tunnels; (3) The mass fraction level of contaminate stratification differs along the tunnels. The pollutant tends to form y-component layering near the upwind opening and x-component stratification at the downwind opening of the two tunnels. Full article

Monitoring the horizontal distribution of PM_2.5 within urban areas is of great significance, not only for environmental management but also for providing essential data to understand the distribution, formation, transport, and transformation of PM_2.5 within cities. This study proposes a novel approach—the Spectral Analysis-based PM_2.5 Estimation Machine Learning (SAPML) model. This method uses a machine learning model trained with features derived from multi-azimuth and multi-elevation MAX-DOAS observations, specifically the oxygen dimer (O₄) differential slant column densities (O₄ dSCDs), and labels provided by near-surface ground measurements corresponding to each azimuthal direction, to estimate near-surface PM_2.5 concentrations. This approach does not rely on meteorological data and enables multi-directional near-surface PM_2.5 monitoring using only a single independent instrument. SAPML bypasses the intermediate retrieval of aerosol extinction coefficients and directly estimates PM_2.5 concentrations from spectral analysis results, thereby avoiding the accumulation of errors. Using O₄ dSCD data from multiple MAX-DOAS stations for model training eliminates inter-station conversion differences, allowing a single model to be applied across multiple sites. Station-based k-fold cross-validation yielded an average Pearson correlation coefficient (R) of 0.782, demonstrating the robustness and transferability of the method across major regions in China. Among the machine learning algorithms evaluated, Extreme Gradient Boosting (XGBoost) exhibited the best performance. Feature optimization based on importance ranking reduced data collection time by approximately 30%, while the correlation coefficient (R) of the estimation results decreased by only about 1.3%. The trained SAPML model was further applied to two MAX-DOAS stations in Hefei, HF-HD, and HFC, successfully resolving the near-surface PM_2.5 spatial distribution at both sites. The results revealed clear intra-urban heterogeneity, with higher PM_2.5 concentrations observed in the western industrial park area. During the same observation period, an east-to-west PM_2.5 pollution transport event was captured: PM_2.5 increases were first detected in the upwind direction at HF-HD, followed by the downwind direction at the same station, and finally at the downwind station HFC. These results indicate that the SAPML model is an effective approach for monitoring intra-urban PM_2.5 distributions. Full article

This study characterizes a compost-bedded pack barn of a dairy cattle farm in terms of CO₂ emissions approximately 20 min after tilling under stable atmospheric conditions. Emission fluxes were calculated with the bLS model WindTrax, assessing modeled CO₂ concentrations at two altitudes (5.0 m and 10.0 m ABGL) by comparing them with those measured by a UAV-based system at the same two altitudes. The UAV-based system was equipped with a low-cost self-engineered MSP (multi-sensor platform) containing an NDIR sensor for measuring concentrations and detecting environmental conditions, which were measured both by MSPs and commercial sensors. The input data were provided by the same sensors positioned on the ground (1.5 m ABGL), upwind and downwind with respect to the emission source. A sensitivity analysis of atmospheric stability in the bLS model yielded differences between median calculated emission fluxes for stable and unstable conditions from −0.020 to 0.034 g ∙ m⁻² ∙ s⁻¹. Mean percentage errors gave overestimates of 8–39% and 13–21% 5.0 m and 10.0 m ABGL. The RMSE also indicated overestimates ranging from 44 to 275 ppm. This is the first study to validate concentrations calculated by a bLS model at two altitudes by using a UAV-based system on a compost-bedded pack barn. Full article

This study investigates the aerodynamic effect of Gurney flaps (GFs) of different heights on the performance of a Darrieus vertical axis wind turbine (VAWT). Through numerical simulations, the performance of a baseline airfoil is compared against configurations with GFs of 0.5%c, 1%c, and 1.5%c chord lengths across a range of tip-speed ratios (TSRs). Results identify the 0.5%c GF as the optimal configuration, providing consistent power enhancement across all tested conditions, unlike the taller flaps which showed inconsistent or negative effects. This optimal configuration achieved a peak power coefficient (C_p) of 0.366 at TSR = 2.0, a 3.73% improvement over the baseline, and critically, enhanced the low-speed power by 6.30% at TSR = 0.5, improving the turbine’s self-starting capability. Flow field analysis reveals a dual-benefit mechanism for this superior performance: at low TSRs, the GF delays flow separation during the upwind pass to increase lift, while at higher TSRs, it effectively manages the wake during the downwind pass to reduce drag and mitigate negative torque. The study concludes that the 0.5%c GF strikes an optimal balance between lift augmentation and drag. Full article

Temperature distribution inside the vacuum chamber of the TRX 2000(A) near space environment simulation test system (NSESTS) was investigated through both experimentation and computational fluid dynamics simulation. Comparison between the experimental result and the simulation result showed that these two results were very close to each other, validating the feasibility of using the simulation method to study the temperature distribution inside the NSESTS. Then, the effect of wind, either downwind or upwind, on temperature uniformity inside the NSESTS was investigated through the simulation method. The simulation result showed that the non-uniformity coefficient will be reduced from 0.2757 to 0.2012 (by 27.1%) in the case of downwind and to 0.2055 (by 25.5%) in the case of upwind. Then, the simulation result was validated by experiment. The result of this research indicates that the temperature uniformity can be greatly improved through installment of additional fans inside the NSESTS. Full article

Downwind wind turbines offer potential for reduced blade loads and lighter designs, yet systematic aeroelastic comparisons against upwind configurations remain limited, especially for multi-megawatt scales. This study conducts comprehensive OpenFAST simulations of the IEA 15 MW reference turbine in both configurations, contextualized against smaller turbines (2.1, 5, and 10 MW). Scaling trends reveal that, with the increase in turbine size, the disadvantage of the downwind turbine (higher flapwise and edgewise fatigue load) is gradually disappearing and even becomes an advantage. However, downwind configurations amplify tower base loads significantly. These results highlight scalable benefits for blade loads but underscore critical trade-offs requiring tower reinforcement. Optimizing rotor-nacelle mass distribution emerges as a key pathway to mitigate tower penalties while leveraging blade-load alleviation for larger downwind turbines. Full article

Floating offshore wind turbines present peculiar characteristics that make them particularly interesting for the implementation of wind farm control strategies such as wake mixing to increase the overall power production. Wake mixing is achieved by generating an unsteady cyclical load on the blades of upwind turbines to decrease the wind deficit on downwind turbines. The possibility of exploiting the yaw motion of a floating offshore wind turbine allows for amplified wake mixing or a reduction in the workload of the control mechanism. To amplify the yaw motion of the system at a selected excitation frequency, a multi-disciplinary optimization framework was developed to modify selected properties of the floating platform and mooring line configuration of the DTU 10 MW turbine on the Triple Spar platform. At the same time, operational and structural constraints were taken into account. A simulation-based approach was chosen to design a floating platform and mooring line configuration that were optimized to integrate with the new control strategy based on wake mixing in floating offshore wind farms. Modifying the floating platform spar arrangement and mooring line properties allowed us to tune the yaw natural frequency of the system in accordance with the excitation frequency of the wake control technique and amplify the yaw motion while controlling the deviations of the operational constraints and costs from the baseline configuration. Full article

Fixed double-row photovoltaic (PV) arrays are susceptible to wind-induced damage, while their wind load characteristics remain inadequately investigated. This study employs computational fluid dynamics (CFD) simulations to systematically analyze wind load behavior under varying operational conditions, aiming to identify critical scenarios and structural vulnerabilities. First, the validity of the CFD methodology was verified through direct comparison between wind tunnel pressure measurements of an isolated PV module and corresponding numerical simulations. Subsequently, scaled PV array models were constructed to replicate practical engineering configurations, enabling a systematic evaluation of wind direction effects on mean net wind pressure coefficients and three-component force coefficients. Finally, surface wind pressure distribution patterns were examined for four representative wind angles (0°, 45°, 135°, 180°). Results demonstrate that edge-positioned modules exhibit maximum mean net wind pressure coefficients and three-component force coefficients under oblique wind angles (45° and 135°), which are identified as the most critical operational conditions. In contrast, minimal wind loads were observed at a 90° wind angle, indicating an optimal orientation for array installation. Additionally, significantly higher surface wind pressure coefficients were recorded for edge modules under oblique winds (45°/135°) compared to both interior modules and other wind angles. It was found through the study that under upwind conditions (0–90°), the lower-row components are capable of withstanding greater wind loads, whereas under downwind conditions (90–180°), an increase in the loads exerted on the upper-row components was observed. Full article

Spaceborne synthetic aperture radar (SAR) has been proven capable of observing the directional ocean wave spectrum across the global ocean. Most of the efforts focus on the integrated wave parameters to characterize the imaged ocean wave properties. The newly proposed spectrum-based radar parameter mean cross-spectrum (MACS) is investigated using SAR image spectral properties of range-traveling waves at a wavelength of 20 m, based on Sentinel-1 wave mode acquisition of high spatial resolution (5 m). The magnitude of MACS is documented relative to environmental conditions (wind speed and direction) in terms of its variation for two polarizations at two incidence angles. This parameter exhibits distinct upwind–downwind asymmetry and polarization ratio at two incidence angles (23.8° and 36.8°). In addition, by comparing the SAR measurements with simulated MACS, we derive an improved real aperture radar modulation transfer function. Results obtained in this study shall help obtain a more accurate ocean wave spectrum based on the improved RAR modulations. Full article

Ribbon waterfront parks in hot summer and cold winter regions play a crucial role in microclimate regulation and thermal comfort enhancement due to the combined effects of water bodies and vegetation. This study focuses on ribbon waterfront parks in Hefei. This study investigates the influence of park environmental factors (e.g., plant community characteristics, spatial configuration of water bodies, and plaza layouts) on the summer thermal environment through field measurements and ENVI-met numerical simulations. Based on field studies and a literature review, five environmental factors were selected as test variables: water body direction (S), tree planting density and arrangement (A), square distribution form (B), square location (C), and pavement material (D). Using orthogonal testing, 64 different environmental scenarios under four distinct water body orientations were designed and simulated using ENVI-met (Version 5.6.1), followed by a quantitative analysis of the simulation results. The findings reveal that the interaction between water body orientation and prevailing wind direction significantly influences the cooling efficiency in both the upwind and downwind regions. In addition, through orthogonal testing, Range Analysis (RA), and analysis of variance (ANOVA), the order of magnitude of the effect of each experimental factor on the Universal Thermal Climate Index (UTCI) can be derived: density and form of tree planting (A) > pavement material (D) > location of the square in the park (C) > forms of distribution of squares in the park (B). Finally, this study suggests various environmental factor-setting schemes for ribbon waterfront parks that are tailored to distinct microclimatic requirements. It also provides design recommendations to improve thermal comfort in parks based on the orientation of different water bodies. Furthermore, it offers specific references and foundations for planning, designing, optimising, and renovating waterfront parks of similar scales. Full article

Hydrogen energy is considered the most promising clean energy in the 21st century, so hydrogen refuelling stations (HRSs) are crucial facilities for storage and supply. HRSs might experience hydrogen leakage (HL) incidents during their operation. Hydrogen-producing and refuelling integrated stations (HPRISs) could make thermal risks even more prominent than those of HRSs. Considering HL as the target in the HPRIS, through the method of fault tree analysis (FTA) and analytic hierarchy process (AHP), the importance degree and probability importance were appraised to obtain indicators for the weight of accident level. In addition, the influence of HL from storage tanks under ambient wind conditions was analysed using the specific model. Based upon risk analysis of FTA, AHP, and ALOHA, preventive measures were obtained. Through an evaluation of importance degree and probability importance, it was concluded that misoperation, material ageing, inadequate maintenance, and improper design were four dominant factors contributing to accidents. Furthermore, four crucial factors contributing to accidents were identified by the analysis of the weight of the HL event with AHP: heat, misoperation, inadequate maintenance, and valve failure. Combining the causal analysis of FTA with the expert weights from AHP enables the identification of additional crucial factors in risk. The extent of the hazard increased with wind speed, and yet wind direction did not distinctly affect the extent of the risk. However, this did affect the direction in which the risk spreads. It is extremely vital to rationally plan upwind and downwind buildings or structures, equipment, and facilities. The available findings of the research could provide theoretical guidance for the applications and promotion of hydrogen energy in China, as well as for the proactive safety and feasible emergency management of HPRISs. Full article

A two-eyed seeing approach considered Indigenous knowledge and Western science towards eco–health, reconciliation and land back with Fort William First Nation (FWFN) in Ontario, Canada. To map traditional land use, occupancy, and ecological knowledge, we interviewed 49 FWFN members about their hunting, fishing, trapping, plant harvesting, cultural sites, and sacred gatherings on their ancestral land. Their traditional land use and occupancy includes more than 7.5 million ha of their ancestral land. The FWFN members reported many industrial impacts on their reserve and ancestral land. We analyzed the normalized difference vegetation index (NDVI) change over time on FWFN’s ancestral land and the Thunder Bay Pulp and Paper Mill (TBPP)’s National Pollutant Release Inventory data to investigate the FWFN members’ ecohealth concerns. The NDVI analysis revealed large tracts of degraded FWFN’s ancestral land due to logging areas, mining claims, settlements, and paper mills. Mining claims and greenstone belts occupy a quarter of the FWFN members’ ancestral land. The TBPP mill dumped pollution into the Kaministiquia River upstream and upwind of the FWFN community, exposing FWFN members to kilotons of cancerous and other toxic chemicals each year for over a century. Resource extraction and pollution in Northwestern Ontario negatively impacted the human health and ecosystem integrity of FWFN, requiring reconciliation by restoring damaged land and preventing pollution as the starting point for land back. The first step to land back is ending the environmental racism of the TBPP’s pollution directed downstream and downwind of FWFN and protecting ancestral land against logging, mining, and other extractive industries. Full article

Existing research into this topic primarily focuses on low-altitude areas, neglecting the impact of extreme environmental conditions such as low temperature, low oxygen level, and low pressure in high-altitude regions. Based on the smoke diffusion theory, a series of CFD numerical simulations were conducted in order to investigate the characteristics of smoke diffusion in the highway tunnel at high altitude. The results indicated that the increase in altitude would enhance the longitudinal propagation velocity of smoke, leading to a more pronounced impact on temperature, CO concentration, and visibility at characteristic heights. Meanwhile, the altitude intensifies the inhibitory impact of longitudinal ventilation on smoke diffusion upwind of the fire source and augments the acceleration effect on smoke diffusion downwind, thereby impeding personnel evacuation on the downwind side. By taking the hazardous range at a characteristic height under the impact of wind velocity and the deceleration of evacuation velocity due to altitude into consideration, a new recommended reduction factor was deduced to design adits for people passing spacing in highway tunnels at high altitude. The findings can serve as a valuable reference for the personal evacuation in high-altitude highway tunnel fires and the design of spacing between adits for people passing within such tunnels. Full article