Search Results (57)

The reliability of passive samplers in measuring volatile organic compounds (VOCs) in indoor air depends on whether the uptake rate is constant given the environmental conditions and sampler exposure duration. The first phase of this study evaluated the performance of charcoal-based, solvent-extracted passive samplers (e.g., Radiello^® 130 passive samplers with white diffusive bodies) over exposure periods ranging from 1 week to 1 year in a test house with known vapor intrusion (VI). Chloroform %Bias values exceeded the ±30% acceptance criterion after 4 weeks exposure. Benzene, hexane, and trichloroethylene (TCE) concentrations were within the acceptance criterion for up to three months. Toluene and tetrachloroethylene (PCE), the two least volatile compounds, demonstrated uniform uptake rates over one year. In the second phase of this study, testing of the longer exposure times of 6 months and 1 year were evaluated with three additional passive samplers: Waterloo Membrane Sampler^TM (WMS^TM), SKC 575 with secondary diffusive cover, and Radiello^® 130 passive samplers with yellow diffusive bodies. The SKC 575 and Radiello^® 130 passive samplers produced acceptable results (%Bias ≤ 30%) over the 6-month exposure period, while the WMS^TM sampler results favored petroleum hydrocarbon more than chlorinated solvent uptake. After the 1-year exposure period, the passive sampler performances were acceptable under specific conditions of this study. The results suggest that all three samplers can produce acceptable results over exposure time periods beyond 30 days and up to a year for some compounds. Full article

The Huanggang iron-tin deposit, located in the southern Greater Khingan Range, is one of the largest Fe-Sn deposits in Northern China (NE China). Iron-tin mineralization occurs mainly in the contact zone between granitoid intrusions and the marble of the Huanggang and Dashizhai formations. Six mineralization stages are identified: (I) anhydrous skarn, (II) hydrous skarn, (III) cassiterite-quartz-calcite, (IV) pyrite-arsenopyrite-quartz-fluorite, (V) polymetallic sulfides-quartz, and (VI) carbonate ones. Fluid inclusions (FIs) analysis reveals that Stage I garnet and Stage II–III quartz host liquid-rich (VL-type), vapor-rich two-phase (LV-type), and halite-bearing three-phase (SL-type) inclusions. Stage IV quartz and fluorite, along with Stage V quartz, are dominated by VL- and LV-type inclusions, while Stage VI calcite contains exclusively VL-type inclusions. The FIs in Stages I to VI homogenized at 392–513, 317–429, 272–418, 224–347, 201–281, and 163–213 °C, with corresponding salinities of 3.05–56.44, 2.56–47.77, 2.89–45.85, 1.39–12.42, 0.87–10.62, and 4.48–8.54 wt% NaCl equiv., respectively. The H–O–C isotopes data imply that fluids of the anhydrous skarn stage (δD = −101.2 to −91.4‰, δ¹⁸O_H2O = 5.0 to 6.0‰) were of magmatic origin, the fluids of hydrous skarn and oxide stages (δD = −106.3 to −104.7‰, δ¹⁸O_H2O = 4.3 to 4.9‰) were characterized by fluid mixing with minor meteoric water, while the fluids of sulfide stages (δD = −117.4 to −108.6‰, δ¹⁸O_H2O = −3.4 to 0.3‰, δ¹³C_V-PDB= −12.2 to −10.9‰, and δ¹⁸O_V-SMOW = −2.2 to −0.7‰) were characterized by mixing of significant amount of meteoric water. The ore-forming fluids evolved from a high-temperature, high-salinity NaCl−H₂O boiling system to a low-temperature, low-salinity NaCl−H₂O mixing system. The garnet U-Pb dating constrains the formation of skarn to 132.1 ± 4.7 Ma (MSWD = 0.64), which aligns, within analytical uncertainty, with the weighted-mean U−Pb age of zircon grains in ore-related K-feldspar granite (132.6 ± 0.9 Ma; MSWD = 1.5). On the basis of these findings, the Huanggang deposit, formed in the Early Cretaceous, is a typical skarn-type system, in which ore precipitation was principally controlled by fluid boiling and mixing. Full article

Concrete porosity is one of the fundamental properties for the structural characterization of cementitious materials. This study compares porosity data obtained with dynamic water vapor sorption (DWVS) with the more commonly used mercury intrusion porosimetry (MIP) method for a wide range of concrete samples made with basaltic aggregates, typical of the Canary Islands, which are porous. The objective was to propose an alternative method for routine concrete monitoring that avoids the use of a hazardous substance such as mercury. The results reveal fundamental differences between the MIP and water-accessible porosimetry (WAP) data, although a correlation between the methods was revealed where MIP = 1.18 × WAP. The study was completed by an analysis of the relationships between the porosity and the characteristics and properties of concrete (water/cement ratio and strength), as well as the calculation of the tortuosity factor and a frost durability factor. Full article

Subsurface contamination can migrate upward into overlying buildings, exposing the buildings’ inhabitants to contaminants that can cause detrimental health effects. This phenomenon is known as vapor intrusion (VI). When evaluating a building for VI, one must understand that seasonal and short-term variability are significant factors in determining the reasonable maximum exposure (RME) to the occupants. RME is a semi-quantitative term that refers to the lower portion of the high end of the exposure distribution—conceptually, above the 90th percentile exposure but less than the 98th percentile exposure. Samples were collected between December 2020 and April 2022 at six non-residential commercial buildings in Fairbanks, Alaska. The types of samples collected included indoor air (IA); outdoor air; subslab soil gas; soil gas; indoor radon; differential pressure; indoor and outdoor temperature; heating, ventilation, and air conditioning (HVAC) parameters; and other environmental factors. The buildings in close proximity to the volatile organic compound (VOC) source/release points presented less variability in indoor air concentrations of trichloroethylene (TCE) and tetrachloroethylene (PCE) compared to the buildings farther down gradient in the contaminated groundwater plume. The VOC data pattern for the source area buildings shows an outdoor air temperature-dominated behavior for indoor air concentrations in the summer season. HVAC system operations had less influence on long-term indoor air concentration trends than environmental factors, which is supported by similar indoor air concentration patterns independent of location within the plume. The use of soil temperature and indoor/outdoor temperatures as indicators and tracers (I&Ts) across the plume as predictors of the sampling period could produce a good estimation of the RME for the building occupants. These results, which show the use of soil temperature and indoor/outdoor temperatures as I&Ts, will help advance investigative methods for evaluation of VI in similar settings and thereby improve the protection of human health in indoor environments. Full article

This paper presents experimental studies of the formation of thermal and humidity conditions in two wooden historic churches in southern Poland. The environmental and cultural changes taking shape are creating the need to modernize existing buildings to sustainable standards. The modernization of historic religious buildings is complicated by restrictions on the intrusion of vertical partitions, which are often covered with valuable wall paintings. The paper focuses on the important aspect of preserving historically valuable buildings in good condition and assessing the threat posed by vapor condensation on the surface of the partitions. The studied buildings differ in terms of their uses and heating systems. Building A is unheated, while building B is equipped with a heating system. The scope of the study includes continuous measurements of the temperature and relative humidity of the indoor air inside and outside the studied churches. The work presents a detailed analysis and comparison of the formation of thermal and humidity conditions inside the churches. A computational model of the buildings was created, and then a computational simulation of the risk of water vapor condensation on the surface of the external walls was carried out. The analysis presents the influence of the external climate on the formation of the thermo-humidity conditions inside the buildings, especially in the unheated church. Also shown is the effect of the temporary heating of the church on ensuring the optimal heat and moisture conditions for historic wooden buildings. The analysis shows that turning on the heating only during the use of the church slightly improves the thermal and humidity conditions compared to the unheated church. Additionally, the analysis shows that the occasional use of the unheated church contributes to significant cooling of the church (even to −8.4 °C in the winter half year). Another conclusion that the computational analysis reveals is that water vapor condensation on the surface of the external walls is impossible. However, the difference between the air temperature in the church and the dew point temperature, specifically in the unheated church, is 1.6 °C. Therefore, at lower outside air temperatures, there may be a risk of water vapor condensation. Full article

With the acceleration of urbanization, clay with significant variations in organic matter content is commonly encountered in infrastructure construction. Its unique water retention capacity is crucial for engineering safety and stability. This study uses red clay as the matrix and incorporates peat to prepare soil samples with varying organic matter content. Soil–water characteristic tests were conducted using the pressure plate method, filter paper method, and vapor equilibrium method to obtain the soil–water characteristic curves across the entire suction range. Subsequently, scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) tests were performed to analyze the mechanisms underlying the water retention characteristics. The experimental results indicate that the three different suction tests accurately reflect the soil–water characteristic curves of organic clay across the entire suction range. As the organic matter content in the soil increases, the air entry value and residual value of the soil samples exhibit a linear relationship with the organic matter content, enhancing the soil’s water retention capacity. The increase in organic matter content alters the microstructure of the clay, transforming the mineral–organic aggregates from ellipsoidal to plate-like shapes. While organic matter can influence the water retention of clay, within a certain suction range, the water retention capacity of organic clay is also related to the pore structure and the state of water within the pores. This is crucial for ensuring engineering safety and optimizing design solutions. Full article

In this paper, droplet vaporization dynamics in a heated bubbling fluidized bed was studied. A volatile hydrocarbon liquid jet comprising acetone was injected into a hot bubbling fluidized bed of Geldart A-type glass ballotini particles heated at 150 °C, well above the saturation temperature of acetone (56 °C). Intense interactions were observed among the evaporating droplets and hot particles during contact with the re-suspension of particles due to a release of vapour. A non-intrusive schlieren imaging method was used to track the hot air and vapour mixture plume in the freeboard region of the bed and the acetone vapour fraction therein was mapped. The jet vaporization dynamics in the bubbling fluidized bed was modelled in a Eulerian–Lagrangian CFD (computational fluid dynamics) modelling framework involving heat and mass transfer sub models. The CFD model indicated a dispersion of the vapour plume from the evaporating droplets which was qualitatively compared with the schlieren images. Further, the CFD simulation predicted a significant reduction (~60 °C) in the local bed temperature at the point of the jet injection, which was indirectly confirmed in an experiment by the presence of particle agglomerates. Full article

Understanding baseline O₃ is important as it defines the fraction of O₃ coming from global sources and not subject to local control. We report the occurrence and sources of high baseline ozone days, defined as a day where the daily maximum 8 h average (MDA8) exceeds 70 ppb, as observed at the Mount Bachelor Observatory (MBO, 2.8 km asl) in Central Oregon from 2004 to 2022. We used various indicators and enhancement ratios to categorize each high-O₃ day: carbon monoxide (CO), aerosol scattering, the water vapor mixing ratio (WV), the aerosol scattering-to-CO ratio, backward trajectories, and the NOAA Hazard Mapping System Fire and Smoke maps. Using these, we identified four causes of high-O₃ days at the MBO: Upper Troposphere/Lower Stratosphere intrusions (UTLS), Asian long-range transport (ALRT), a mixed UTLS/ALRT category, and events enhanced by wildfire emissions. Wildfire sources were further divided into two categories: smoke transported in the boundary layer to the MBO and smoke transported in the free troposphere from more distant fires. Over the 19-year period, 167 high-ozone days were identified, with an increasing fraction due to contributions from wildfire emissions and a decreasing fraction of ALRT events. We further evaluated trends in the O₃ and CO data distributions by season. For O₃, we found an overall increase in the mean and median values of 2.2 and 1.5 ppb, respectively, from the earliest part of the record (2004–2013) compared to the later part (2014–2022), but no significant linear trends in any season. For CO, we found a significant positive trend in the summer 95th percentiles, associated with increasing fires in the Western U.S., and a strong negative trend in the springtime values at all percentiles (1.6% yr⁻¹ for 50th percentile). This decline was likely associated with decreasing emissions from East Asia. Overall, our findings are consistent with the positive trend in wildfires in the Western United States and the efforts in Asia to decrease emissions. This work demonstrates the changing influence of these two source categories on global background O₃ and CO. Full article

A simulation of an extreme precipitation event in southern Xinjiang, which is the driest area in China, seizes the whole initiation process of the intense convective cell responsible for the high hourly rainfall amount. Considering the inner connection between convection and vertical motions, the characteristics and mechanisms of the vertical accelerations during this initial development of the deep convection are studied. It is shown that three key accelerations are responsible for the development from the nascent cumuli to a precipitating deep cumulonimbus, including sub-cloud boundary-layer acceleration, in-cloud deceleration, and cloud-top acceleration. By analyzing the right-hand terms of the vertical velocity equation in the framework of the WRF model, together with a diagnosed relation of perturbation pressure to perturbation potential temperature, perturbation-specific volume (or density), and moisture, the physical processes associated with the corresponding accelerations are revealed. It is found that sub-cloud acceleration is associated with three-dimensional divergence, indicating that the amount of upward transported air must be larger than that of horizontally convergent air. This is favorable for the persistent accumulation of water vapor into the accelerated area. In-cloud deceleration is caused by the intrusion or entrainment of mid-level cold air, which cools down the developing cloud and delays the deep convection formation. Cloud-top acceleration is responsible for the rapid upward extension of the cloud top, which is highly correlated with the convergence and upward transport of moisture. Full article

The Xiaorequanzi Cu deposit is located in the western part of the Dananhu–Tousuquan Island arc in eastern Tianshan, Xinjiang. It includes stratiform and epithermal-related veinlet mineralization. However, the genesis of this deposit remains controversial. Therefore, fluid inclusions, H–O isotopes, in situ S, and trace elements in pyrite were employed in this study to constrain the origins of the deposit. The Xiaorequanzi Cu deposit’s mineralization stages can be categorized into the following three phases: I. volcanogenic massive sulfide (VMS) mineralization; II. quartz–chalcopyrite–pyrite; and III. quartz–chalcopyrite–sphalerite stages. Fluid inclusion studies suggest that Stage I is distinguished by high-temperature (peak: 320–360 °C) and moderate-salinity (peak: 7–9 wt%) fluids belonging to the H₂O–NaCl ± CO₂ system. Stages II–III only exhibit vapor–liquid inclusions, with mineralizing fluids belonging to the medium-to-low-temperature (Stage II peak: 160–180 °C; Stage III peak: 120–130 °C) and medium-to-low-salinity (Stage II peak: 5–7 wt%; Atage III peak: 4–6 wt%) H₂O–NaCl system. The H–O isotopic data suggest that mineralizing fluid in Stage I is a blend of magmatic and paleo-seawater sources, while in Stages II–III, meteoric water predominates, accompanied by low mineralizing temperatures. In situ S isotope results indicate that the source of mineralizing materials in Stage I (2.52–4.48‰) were magmatic rocks, whereas the markedly higher δ³⁴S values in stages II–III (4.68–6.60‰) suggest sulfur isotope leaching from sedimentary rocks by meteoric water as the main source. The LA–ICP–MS data of pyrite in the Xiaorequanzi Cu deposit suggest that Py₁ was formed through volcanic processes, whereas Py₂ and Py₃ exhibited epithermal characteristics. Throughout the mineralization process, a trend in increasing oxygen and decreasing sulfur fugacity occurred, accompanied by a decreased mineralization temperature. This observation corresponds with the temperature data derived from the fluid inclusions. Additionally, the principal components of different generations of pyrite segregated as two clusters representing the VMS (Stage I) and epithermal mineralization (stages II–III). In summary, based on comprehensive research and previous geochronological studies, it is suggested that the Xiaorequanzi Cu deposit experienced two mineralization stages. The early stage is related to the volcanic activity of the Early Carboniferous (354 Ma), whereas the later stage is associated with Carboniferous–Permian (266–264 Ma) volcanic intrusions. Full article

Using multi-source observation data including automatic stations, radar, satellite, new detection equipment, and the Fifth Generation European Centre for Medium-Range Weather Forecasts Reanalysis (ERA-5) data, along with the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) platform, an analysis was conducted on a rainstorm process that occurred in Nanjing on 15 June 2020, with the aim of providing reference for future urban flood control planning and heavy rainfall forecasting and early warning. The results showed that this rainstorm process was generated under the background of an eastward-moving northeast cold vortex and a southward retreat of the Western Pacific Subtropical High. Intense precipitation occurred near the region of large top brightness temperature (TBB) gradient values or the center of low TBB values on the northern side of the convective cloud cluster. During the heavy precipitation period, the differential propagation phase shift rate (K_DP), differential reflectivity factor (Z_DR), and zero-lag correlation coefficient (ρ_HV) detected by the S-band dual-polarization radar all increased significantly. The vertical structure of the wind field detected by the wind profile radar provided a good indication of changes in precipitation intensity, showing a strong correspondence between the timing of maximum precipitation and the intrusion of upper-level cold air. The abrupt increase in the integrated liquid water content observed by the microwave radiometer can serve as an important indicator of the onset of stronger precipitation. During the Meiyu season in Nanjing, convective precipitation was mainly composed of small to medium raindrops with diameters less than 3 mm, with falling velocities of raindrops mainly clustering between 2 and 6 m·s⁻¹. The rainstorm process featured four water vapor transport channels: the mid-latitude westerly channel, the Indian Ocean channel, the South China Sea channel, and the Pacific Ocean channel. During heavy rainfall, the Pacific Ocean water vapor channel was the main channel at the middle and lower levels, while the South China Sea water vapor channel was the main channel at the upper level, both accounting for a trajectory proportion of 34.2%. Full article

Basements are integral to contemporary building design, serving as foundational structures with diverse functions in residential and commercial constructions. The utilization of wood as a natural, economical, and CO₂ storage material for basement construction significantly influences the future of construction, necessitating established concepts to guarantee sustainability, and foremost, avoid possible damages induced by moisture intrusion. This paper explores the hygrothermal performance of a wooden basement when subjected to severe indoor and outdoor climates and in the absence of pressuring groundwater. Using both 1D and 2D numerical simulations, this study conducts risk analyses for several cases to evaluate how the wooden basement behaves under critical conditions, such as moisture accumulation in the assembly due to air convection through a gap in the insulation layer, air leakage through the waterproofing membrane, and high-vapor pressure caused by the high moisture load in the indoor space. The thresholds are determined for the initial wood moisture and indoor relative humidity, under which supports are given for the use of wooden elements in the basement structures, exhibiting satisfactory performance and avoiding wood decay in the construction. Additionally, the impact of the waterproofing membrane on avoiding wood decay in the assembly is highlighted. Full article

The role of dust intrusions in the formation of lake heatwaves has not yet been discussed in previous publications. We investigated a lake heatwave (LHW) and an atmospheric heatwave (AHW) in the freshwater Lake Kinneret in the Eastern Mediterranean: these were caused by an extreme dust intrusion that lasted for a 10-day period (7–17 September 2015). The AHW and LHW were defined as periods of abnormally high air temperature (Tair) and lake surface water temperature (SWT) compared to their 90th percentile thresholds in September. In the daytime, the maximal intensities of AHW and LHW reached 3 °C and 2 °C, respectively. This was despite the pronounced drop in solar radiation due to the dust radiative effect. The satellite SWT retrievals were incapable of representing the abnormally high SWT in the presence of the extreme dust intrusion. Both METEOSAT and MODIS-Terra showed a sharp decrease in the SWT compared to the actual SWT: up to 10 °C in the daytime and up to 15 °C in the nighttime. Such a significant underestimation of the actual SWT in the presence of a dust intrusion should be considered when using satellite data to analyze heatwaves. In the absence of moisture advection, the AHW and LHW were accompanied by an increase of up to 30% in absolute humidity (ρ_v) over the lake. Being a powerful greenhouse gas, water vapor (characterized by an increased ρ_v) absorbed most of both the upwelling and downwelling longwave thermal radiation, heating the near-ground atmospheric layer (which is in direct contact with the lake water surface), in the daytime and nighttime. In the nighttime, the maximal intensity of the AHW and LHW reached 4 °C and 3 °C, respectively. Because of the observed steadily increasing dust pollution over the Eastern Mediterranean during the past several decades, we anticipate that dust-related lake heatwaves will intensify adverse effects on aquatic ecosystems such as reducing fishery resources and increasing harmful cyanobacteria blooms. Full article

Water intrusion into a building envelope describes the unwanted movement of water or vapor into a building, where it causes damage. Various factors dictate water intrusion category determination and classification. These factors include, but are not limited to, the type and degree of water intrusion, the source and route of the contamination, and exposure time, as well as geographical environmental conditions. This comprehensive research paper looked at the literature and the science to explore the bases for indoor environmental professional (IEP) classification and category determination, but also the science behind the effects of water intrusion on building materials (BM). The efficacy of building materials once degradation has occurred and any accelerating effects impacting the efficiency of building materials and their loss of integrity were closely examined in terms of material microstructural and compositional changes. The damaging effects of moisture and heat on building materials are called hygrothermal damage, which compromises the properties and use of materials. Both aspects of building integrity, i.e., water intrusion and structural deterioration, should be of concern when mitigating and remediating the intrusion of moisture. Previous research on the clarification of water categories for water intrusions is lacking. Past approaches to water classification have lacked universal scientific clarity and understanding. In addition to a need to understand the effects that water category might have on building materials and their corresponding degree of degradation, more science and reviews are needed. The need for proper class and category determination for the remediation of water intrusion within buildings is the first step toward achieving correct mitigation to ensure human health and safety. The possible adverse health effects of water intrusion need focus and cohesion for the determination of categories. We know that the final determination of water categories differs according to the degree of contamination over time and the degree of a given class of water intrusion; however, what role do the route and initial water contamination play in the determination of the category? The following paper aims to provide not only a review of the science but also an elaboration of the category determination process and the degradation effects on building materials which should be considered, as well as possible avenues of scientific research. Full article

In an electromagnetic launch system, the surface of the aluminum alloy armature is subjected to high-temperature ablation, leading to the generation of significant metal vapor and the initiation of high-energy arcs. This damages the armature structure and can result in a launch failure. Enhancing the ablation resistance of the armature surface is crucial for improving launch efficiency. In this study, a model for the surface modification of an aluminum alloy armature was constructed. The impact of the CoCrNiFeAl_x surface-modified material on the resistance to ablation and structural changes of the armature during arc ablation was elucidated through molecular dynamics simulation. Results show that adding a CoCrNiFeAl_x fused cladding layer can effectively enhance the material’s high-temperature resistance. The CoCrNiFeAl_x fused cladding significantly reduces the depth of arc intrusion. The CoCrNiFeAl_x aluminum alloy model exhibits a narrower strain range on the bombarded surface and a more flattened bombardment crater shape. CoCrNiFeAl_x fused cladding helps to reduce damage from substrate bombardment. Comparing simulation results indicates that CoCrNiFeAl_0.25 performs best in high-temperature resistance and impact strength, making it the most preferred choice. This study elucidates the law of high-entropy alloy arc ablation resistance and its micromechanism in armature surface modification. It provides a theoretical basis and technical support for preparing high-entropy alloy–aluminum alloy-modified armatures with superior ablation resistance performance. Full article