Instantaneous Concentration Research Articles

Turbulent double-diffusive convection and implementation of entropy production rate due to the mean and the fluctuating flow field

The present study performs a CFD-based analysis of entropy production due to conjugate turbulent heat and mass transfer. For the turbulent regime, the instantaneous temperature, concentration, and velocity fields are resolved into time-averaged mean and fluctuating parts. Thus, six different terms of entropy production arise due to this mode of temperature and species transfer. Unfortunately, such a model does not exist and a new approach is therefore needed which makes this problem more challenging. Hence, the overall aim of this paper is twofold: First, is to develop a new approach to cope with the entropy production that takes into account all the six different terms due to temperature and species transport. Second, is to carry out a numerical simulation of double-diffusive free convection inside a square cavity. On the basis of asymptotic considerations, a new formula that expresses entropy production due to fluctuating concentration gradients was derived. Depending on the Rayleigh number and the buoyancy ratio, the total entropy increased significantly when the fluctuating terms were accounted for. Total entropy was found to increase by up 27% for N = +5.0 and Rayleigh number of 109. However, it increased by 38% when N = +1.0 and Ra = 1010.

A Scoring-Based Risk Assessment Method Proposal for Methane Explosions in Underground Coal Mines

Mining is one of the sectors with the highest number of fatal occupational accidents. According to statistics, the majority of these fatal accidents are caused by methane explosions. In order for the explosion to occur, methane needs to form a certain concentration, sufficient oxygen and igniting elements are required. One of the most important factors that can affect methane formation is the carbon content of coal. As the carbon content increases, the probability of formation of flammable hydrocarbon-derived gas increases. The porous structure is a factor that causes methane to accumulate and create instantaneous concentration. It is known that the formation of the ignition element is directly proportional to the quartz content of the wall rocks. In this study, a new risk assessment method is proposed by assigning scores to the linguistic expressions of all these side parameters. This proposed method enables a proactive approach regardless of exact measurements and forced ventilation principles. It is foreseen that unexpected results can be prevented with the measures to be taken in this direction.

Stream metabolism sources a large fraction of carbon dioxide to the atmosphere in two hydrologically contrasting headwater streams

AbstractHeadwater streams are control points for carbon dioxide (CO2) emissions to the atmosphere, with relative contributions to CO2 emission fluxes from lateral groundwater inputs widely assumed to overwhelm those from in‐stream metabolic processes. We analyzed continuous measurements of stream dissolved CO2 and oxygen (O2) concentrations during spring and early summer in two Mediterranean headwater streams from which we evaluated the contribution of in‐stream net ecosystem production (NEP) to CO2 emission. The two streams exhibited contrasting hydrological regimes: one was non‐perennial with relatively small groundwater inflows, while the other was perennial and received significant lateral groundwater inputs. The non‐perennial stream exhibited strong inverse coupling between instantaneous and daily CO2 and O2 concentrations, and a strong correlation between aerobic ecosystem respiration (ER) and gross primary production (GPP) despite persistent negative NEP. At the perennial stream, the CO2–O2 relationship varied largely over time, ER and GPP were uncorrelated, and NEP, which was consistently negative, increased with increasing temperature. Mean NEP contribution to CO2 emission was 51% and 57% at the non‐perennial and perennial stream, respectively. Although these proportions varied with assumptions about metabolic stoichiometry and groundwater CO2 concentration, in‐stream CO2 production consistently and substantially contributed to total atmospheric CO2 flux in both streams. We conclude that in‐stream metabolism can be more important for driving C cycling in some headwater streams than previously assumed.

The ultra-low O2 environment after anaerobic treatment enhanced the antioxidant properties of Agaricus bisporus mushroom

• Excessive oxidative stress in high O2 environment (19%∼20%)accelerated the quality deterioration of mushrooms. • Ultra-low O2 environment (1%∼2%) improved the antioxidant capacity and reduced oxidative damage. • Ultra-low O2 environment inhibited the browning of mushrooms. • Agaricus bisporus has better anaerobic stress adaptation and hypoxia tolerance. Short-term anaerobic treatment provides significant benefits in maintaining the quality of mushrooms, but this benefit requires re-exposing the mushrooms to a suitable O 2 environment. Hence, this research investigated different re-oxygenation environments after 6 h anaerobic treatment on the antioxidant properties of A. bisporus . Results showed that ultra-low O 2 environment (1%∼2%) reduced the accumulation of superoxide radical (O 2 − ) and hydrogen peroxide (H 2 O 2 ), increased the activity of superoxide dismutase (SOD), catalase (CAT) and aseorbate oxidase (APX) and the content of non-enzymatic antioxidants including flavonoids and ascorbic acid, as well as inhibited browning due to the lowest polyphenol oxidase (PPO) and peroxidase (POD) activities. However, oxidative stress caused by instantaneous high concentration O 2 exposure (19%∼20%) caused severe oxidative damage to tissues and thus showed poor antioxidant properties and color maintenance. In conclusion, the ultra-low O 2 environment after anaerobic treatment can maintain the quality of mushrooms by improving the antioxidant capacity and reducing oxidative damage.

Confinement of ZIF-derived copper-cobalt-zinc oxides in carbon framework for degradation of organic pollutants

Developing efficient heterogeneous catalysts for peroxymonosulfate (PMS) activation is extraordinarily desirable in water purification. In this work, a well-defined core-shell copper-cobalt-zinc oxides consisting of Cu0.92Co2.08O4 and ZnCo2O4 wrapped by carbon (CuCoZnO/C) was fabricated by a simple one-step calcination using metal-organic frameworks (MOFs) as templates. The as-obtained catalysts were fully characterized and utilized to activate PMS for phenol degradation, and almost 100% degradation efficiency could be achieved within 10 min. The distinct hollow structure allowed the high instantaneous concentration of organic pollutant in a microenvironment, thus providing a driving force to improve the reaction rate. Owing to the mesoporous and adsorptive carbon as well as active Cu0.92Co2.08O4 shell, most SO4•− radical was confined to catalyst surface immediately once produced rather than release into the bulk solution, making the enriched reactant molecules contact active sites more easily. Further investigation found that both surface-bound SO4•− and 1O2 were dominantly participated in the catalytic process, achieving an ultrafast pollutant degradation. This work offered a new design for multiple complex oxides from MOFs and extended the development of Co-based heterogenous catalyst in PMS activation for the environmental remediation.

Soil CO2 Controls Short‐Term Variation but Climate Regulates Long‐Term Mean of Riverine Inorganic Carbon

AbstractThe evasion of CO2 from inland waters, a major carbon source to the atmosphere, depends on dissolved inorganic carbon (DIC) concentrations. Our understanding of DIC dynamics across gradients of climate, geology, and vegetation conditions however have remained elusive. To understand its large‐scale patterns and drivers, we collated instantaneous and mean (multiyear average) DIC concentrations from about 100 rivers draining minimally‐impacted watersheds in the contiguous United States. Within individual sites, instantaneous concentrations (C) measured at daily to seasonal scales exhibit a near‐universal response to changes in river discharge (Q) in a negative power law form. High concentrations occur at low discharge when DIC‐enriched groundwater dominates river discharge; low concentrations occur under high flow when relatively DIC‐poor shallow soil water predominates river discharge. Such patterns echo the widely observed increase of soil CO2 and DIC with depth and the shallow‐and‐deep hypothesis that emphasizes the importance of flow paths and source water chemistry. Across sites, mean concentrations (Cm) decrease with increasing mean discharge (Qm), a long‐term climate measure, and reachs maxima at around 200 mm/yr. A parsimonious model reveals that high mean DIC arises from soil CO2 accumulation when rates of DIC‐generating reactions are relatively high compared to its export fluxes in arid climates. Although instantaneous and mean DIC concentrations similarly decrease with increasing discharge, results here highlight their distinct drivers: daily to seasonal‐scale instantaneous concentration variations (C) are controlled by subsurface CO2 distribution over depth (from below), whereas long‐term mean concentrations (Cm) are regulated by climate (from above). The results emphasize the significance of land‐river connectivity via subsurface flow paths. They also underscore the importance of characterizing subsurface CO2 distribution to illuminate belowground processes in order to project the future of water and carbon cycles in a warming climate.

Emission characteristics and ozone formation potentials of VOCs from ultra-low-emission waterborne automotive painting

Automotive painting plants are important emission sources of volatile organic compounds (VOCs) that contribute significantly to ground-level ozone (O₃) pollution in atmosphere. Here, we investigated process-specified emission characteristics of VOCs, without or with advanced adsorption/incineration after-treatments, from an ultra-low-emission (ULE) waterborne painting process in a modernized automotive plant. Overall, more than 80 VOCs species were identified and sorted into seven main categories. In the stack emissions without after-treatments, oxygenated VOCs (alcohols, esters, ketones, ethers, etc.) were found to be the most abundant components (48.8%), followed by aromatic (30.9%), alkanes (16.9%) and alkenes (1.2%). Among the different VOCs species discharged to atmosphere (i.e. after adsorption/incineration after-treatments), aromatics demonstrated a predominant contribution (by 60.6%) to the total O₃ formation potentials (OFPs) despite their relatively lower abundance. Trimethylbenzene was identified to have the highest OFPs, and thus should be controlled with peculiar priority. As compared to traditional organic solvent-based painting process, the ULE waterborne process implemented in the target plant allows to reduce the OFPs from 10.7 mg m−3 to 3 mg m−3 (or by 72%). Additional monitoring by unmanned aerial vehicle (over more than 3000 sampling points in the plant) confirmed that the instantaneous concentrations of fugitive VOCs were well below the regulated limit value during typical working and non-working days. These findings may provide important reference for reduction of VOCs emissions and O3 pollution from automotive painting processes.

Large-eddy simulations of gravity currents in the presence of waves

Simulations are performed to investigate gravity currents in the presence of free surface waves using the open-source computational fluid dynamics programme REEF3D with the concentration equation, and the large eddy simulation model for turbulence closure. Simulations show that the period of the oscillation front relates only to the period of the incident waves and the oscillation amplitude increases with wave height. The average velocity of the density current increases with increasing wave height and wavelength. The surface waves change the generation position and combination direction of the turbulence structures in the pycnocline. The oscillatory motion of the waves stabilizes the pycnocline earlier and reduces the turbulent mixing. The instability zone is reduced faster with higher wave heights with well-ordered K-H billows, but not for longer wavelengths. The instantaneous velocity and concentration fields are highly influenced by the incident wave characteristics when compared to that in the absence of waves.

Synergistic degradation of sulfamethoxazole using peroxymonosulfate activated by Fe-Mn-Cu hollow spheres: Kinetics and mechanism studies

The synergistic effect of bimetallic or trimetallic oxide catalysts plays a vital role in sulfate radical-based advanced oxidation processes (SR-AOPs). Herein, a composite catalyst of iron-manganese-copper hollow spheres (FCMHS) was synthesized by hard template method and used for peroxymonosulfate (PMS) activation to degrade sulfamethoxazole (SMX). The catalytic activity of FCMHS was comprehensively evaluated under different conditions (including catalyst loading, PMS dosage, pH etc.). A removal efficiency of 99.1% and a mineralization efficiency of 39.7% for SMX were achieved under the optimal conditions. The kinetic studies demonstrated that the reaction rate for SMX removal by using FCMHS was about 3.5 times faster than that for using copper-manganese hollow spheres (CMHS). The enhanced catalytic performance mainly stemmed from the confined high instantaneous concentration of SMX in the local void space and the synergistic effects of Mn2+/Mn3+/Mn4+, Cu+/Cu2+/Cu3+ and Fe2+/Fe3+ redox cycles to generate radicals and non-radicals. More importantly, the introduction of iron oxide into CMHS substantially facilitated charge transfer at the interface between FCMHS and reaction solution, leading to a high rate and good product selectivity. Furthermore, SMX degradation pathways were proposed by LCMS-IT-TOF assisted with density functional theory (DFT) calculations, and the mechanism was proposed comprehensively. This study opens a reliable and promising avenue for the efficient treatment of antibiotics-polluted water based on trimetallic oxide catalysts.

Spatiotemporal measurement of concentration-dependent diffusion coefficient

We introduce a method to measure the concentration-dependent diffusion coefficient from a sequence of images of molecules diffusing from a source toward a sink. Generally, approaches measuring the diffusion coefficient, such as fluorescence recovery after photobleaching (FRAP), assume that the diffusion coefficient is constant. Hence, these methods cannot capture the concentration dependence of the diffusion coefficient if present. Other approaches measure the concentration-dependent diffusion coefficient from an instantaneous concentration profile and lose the temporal information. These methods make unrealistic assumptions, are not robust, and lead to 100% error. We introduce an image analysis framework that utilizes spatial and temporal information in a sequence of concentration images and numerically solves the general form of Fick's second law using radial basis functions (RBF) to measure the concentration-dependent diffusion coefficient. We term this approach as concentration image diffusimetry (CID). Our method makes no assumptions about the sink and source size and the diffusion dependence on concentration. CID is superior to existing methods in estimating spatiotemporal changes and concentration-dependent diffusion. CID also provides a statistical uncertainty quantification on the measurements using a bootstrapping approach, improving the reliability of the diffusion measurement. We assessed CID's performance using synthetically generated images. Our analysis suggests that CID accurately measures the diffusion coefficient with less than 2% error for most cases. We validated CID with FRAP experimental images and showed that CID agrees with established FRAP algorithms for samples with a constant diffusion coefficient. Finally, we demonstrate the application of CID to experimental datasets of a concentration gradient-driven protein diffusion into a tissue replicate. In conclusion, this work presents an image-based methodology that uses the spatial and temporal changes of concentration fields to measure the concentration-dependent diffusion coefficient.

Theoretical reassessment of the first Stefan diffusion column experiment with a two-component liquid phase, consisting of a high-density volatile solvent and a low-density nonvolatile diluent

The Stefan column was designed in the 19th century to allow the experimental estimation of binary gas diffusion coefficients starting with a pure volatile liquid A placed at the bottom overlaid with a stagnant/inert gas B. A sweeping B stream was provided at the top to remove the diffused gas A. In 1959, Richardson first studied a two-component liquid mixture in the Stefan column. One of his systems, a high-density volatile liquid A (carbon tetrachloride) dissolved in a low-density nonvolatile liquid O (dibutyl phthalate), is of interest to our ongoing research efforts. He collected interfacial descent-time data in his single isothermal Stefan column experiment, and analyzed them with a diffusion transport model, which contained unnecessary assumptions and simplifications, to obtain the binary liquid diffusivity of A in O, D AO. The present study removes the major restrictions of the previous model, reanalyzing the reported data with an improved numerical diffusion model that includes realistic features of the one-dimensional transport problem and statistical information on the estimated D AO. The average ± standard deviation of D AO were 8.82E-10 ± 1.85E-15 m2/s (12 data points), with an error of −13.3% relative to the Richardson value. The new model also provides detailed insight on the diffusive transport dynamics of liquid A by predicting interfacial descent rates, instantaneous concentration profiles in the liquid phase, and the time-dependent fraction of the mass of A lost from the original solution. The model is valuable to chemical engineering researchers studying diffusion–evaporation phenomena and multicomponent distillation processes.

Exploring bulk volume, particle size and particle motion definitions to increase the predictive ability of in vitro dissolution simulations

The definition of the local dissolution environment is central to accurate particle dissolution simulation, and is determined by the apparatus and conditions used. In the flow-through apparatus dissolution occurs in the cell, often in a low velocity environment, with the reservoir considered the relevant volume for dissolution kinetics. Dissolution simulations were conducted using a reduced-order model based on the Ranz-Marshall correlation for mass transfer from spherical particles. Using ibuprofen as a model drug, the effect of defining a local volume to simulate dynamic bulk concentration conditions in the flow-through and paddle apparatus was assessed by comparing use of a near particle volume (NPV), extending a distance of one radius from the particle surface, with a flow-through apparatus cell volume or paddle apparatus vessel volume as the relevant instantaneous volume for dissolution. The instantaneous inlet concentration to NPV or cell volume is the reservoir/vessel concentration at that simulation time point, reflecting the continuous input to the cell of more dilute solution from the reservoir (closed system). Additionally, inputting particle size distribution (PSD) instead of a median particle size (MPS) and enabling or disabling particle motion were investigated, in two media (resulting in low and high solubility) and with two fluid velocity conditions in each apparatus.The NPV predicted effects of fluid velocity differences on dissolution in the high solubility medium in the flow-through apparatus, but had no effect on predictive ability in the paddle apparatus. In both apparatuses, simulations were reasonable for the high solubility environment but underpredicted dissolution in the low solubility environment. The PSD option and disabling particle motion increased the predictive ability of the simulations in low solubility media in the flow-through apparatus. The results highlight the necessity to incorporate the local dynamic dissolution conditions in the flow-through apparatus for accurate dissolution simulation, and the challenges of defining an effective particle size for dissolution simulation and of reflecting hydrodynamic complexity in simulating dissolution in the paddle apparatus.

Application of Optically Stimulated Luminescence Technique in Exploring a Concealed Sandstone‐type Uranium Deposit

AbstractIdentifying ore‐induced geochemical anomalies at the surface that indicate concealed deposits in buried areas remains a significant challenge in geochemical exploration. In this study, in order to trace the source of the geochemical anomalies, systematic luminescence intensity analyses were conducted on quartz grains from the Quaternary regolith at the Hadatu sandstone‐type uranium deposit in the Erenhot Basin. The optically stimulated luminescence (OSL) ages were much older than the depositional ages of the Quaternary regolith. Moreover, quartz OSL ages were closely related to both borehole grades and sampling depths. Thus, the abnormal mineral OSL ages from near‐surface sediments were ultimately controlled by the sandstone‐type uranium deposits. This is identical to the rapid changes of quartz OSL ages (0.063 ka/cm) and equivalent doses (0.19 Gy/cm) with depths in a given sampling site. The instantaneous soil radon concentration was positively correlated with the quartz OSL apparent age, indicating their ore‐induced origin and, as a result, their effectiveness in the exploration of concealed uranium deposits. Other parameters, including mobile‐state uranium and 210Po contents, were poorly correlated with quartz OSL ages and therefore should only be used with caution for geochemical exploration. This is the first time an attempt has been made to discriminate the ore‐induced sources for different surface anomaly parameters, including instantaneous soil radon, mobile‐state uranium and 210Po contents for concealed sandstone‐type uranium deposits.

Large contribution of non-priority PAHs in atmospheric fine particles: Insights from time-resolved measurement and nontarget analysis

Polycyclic aromatic hydrocarbons (PAHs), detrimental to human health, are key components contributing to the carcinogenicity of fine particles. The 16 priority PAHs listed by the United States Environment Protection Agency have been studied extensively. However, other than them, there is a large diversity of PAH species, whose atmospheric concentrations, risks, and variations remain elusive. Here, we carried out a time-resolved nontarget measurement in atmospheric PM2.5 using an improved comprehensive two-dimensional gas chromatography mass spectrometry. The measurement conducted during a 5-day pollution episode at an urban site of Beijing with a time resolution of 2 h. The nontarget analysis of time-resolved chromatographic data was performed for screening PAHs. A total number of 85 PAHs were identified and quantified. We found that other than 16 EPA PAHs, other screened PAHs contributed 43.3% of the total PAH mass concentration and 40.8% poential health risks. Dynamic variations of mass concentrations and their potential health risks of the screened PAHs were captured during a short-term heavy pollution episode, during which the instantaneous PAHs concentrations were much higher than their average concentrations. This study shows the potential for application of nontarget analysis for online comprehensive two-dimensional gas chromatography mass spectrometry and highlights the importance of time-resolved measurement of PAHs in PM2.5 and attention on extended PAHs species other than 16 EPA PAHs.

Detection of Airborne Nanoparticles through Enhanced Light Scattering Images.

A new method is proposed in this paper to detect airborne nanoparticles, detecting the light scattering caused by both the particle and the surrounding molecules, which can surpass the limitations of conventional laser optical methods while maintaining simplicity and cost-effectiveness. This method is derived from a mathematical analysis that describes the particle light scattering phenomenon more exactly by including the influence of light scattered from surrounding gas molecules. The analysis shows that it is often too much of a simplification to consider only light scattering from the detected nanoparticle, because light scattering from the surrounding gas molecules, whether visible or invisible to the sensor, is important for nanoparticle detection. An image detection approach utilizing the light scattering from surrounding air molecules is described for the detection of airborne nanoparticles. Tests using monodisperse nanoparticles confirm that airborne particles of around 50 nm in size can even be detected using a low-cost testing device. This shows further that even when using a simple image processing code, captured particle light scattering images can be converted digitally into instantaneous particle counts or concentrations. The factors limiting conventional pulse detection are further discussed. This new method utilizes a simple static light scattering (SLS) approach to enable the development of new devices with better detection capabilities, paving the way for the further development of nanoparticle detection technology.

A Case Study on the Assessment of Chemical and Physical Pollution Levels during the Copying Process

In accordance with sustainable development goals (SDG’s), urgent action should be taken to make the societal and natural environments better for human beings. People spend most of their time indoors, therefore growing attention is devoted to address indoor air pollution. When the sources of anthropogenic indoor air pollution (copiers, laser printers) are operated indoors, then chemical and physical indoor air pollution may be higher than air pollution outdoors. Ozone, aerosol particles and volatile organic compounds are the result of pollution caused by copiers and printers. The research was carried out in a copying room by recording chemical (ozone and aerosol particles) and physical (noise) environmental pollution. To determine instantaneous ozone concentrations in the copying room, an ozone analyzer O3 41M was used, while to evaluate the effect of ozone on the ambient air of the copying room, passive samplers were used. To determine the number and concentration of aerosol particles in the ambient air of the office, a particle counter AZ-5 was used. In addition, a DrDAQ data logger was used to measure noise emitted by the copier and ambient temperature as well as relative air humidity. It was found that the distribution of ozone and aerosol particles in the copying room was mostly determined by the copying intensity. The maximum concentration of ozone and aerosol particles was determined during automatic copying (91–120 copies/min).

Pollutant Emissions during Oxy-Fuel Combustion of Biomass in a Bench Scale CFB Combustor

Nowadays oxy-fuel combustion of coal and biomass is the most promising option for the reduction of CO2 emissions from power plants. In this paper, emissions of NOx (NO, NO2, N2O and their precursors, such as NH3 and HCN), SO2 and CO during conventional and oxy-fuel combustion of three kinds of biomass (agro, woody and energy crop) and a reference coal are presented and discussed. Combustion tests were conducted at 850 °C in the laboratory-scale circulating fluidized bed (CFB) reactor in air and O2/CO2 atmospheres. A FTIR spectrometer was used to measure instantaneous concentrations of all pollutants in the flue gas. Emissions of SO2, N2O and CO for the combustion of biomass in all atmospheres were lower than those for the combustion of reference coal. It was found that oxidation of nitrogen species released with volatile matter was responsible for high emissions of NOx during combustion of biomass fuels in air and mixtures of O2 and CO2. The lowest NO emissions for tested fuels were detected in oxy-21 atmosphere (21% O2/70% CO2). Oxy-combustion of biomass in O2/CO2 mixtures at 30% and 40% O2 caused a decrease in emissions of N2O and CO while NO and SO2 emissions increased. The results of this study show that the tested biomass fuels are ideal renewable energy resources both in conventional and oxy-fuel conditions with a minor potential for environmental pollution.

Rational feeding strategies of substrate and enzymes to enzymatic hydrolysis bioreactors

Bioreactors operating in fed-batch mode improve the enzymatic hydrolysis productivity at high biomass loadings. The present work aimed to apply rational feeding strategies of substrates (pretreated sugarcane straw) and enzymes (CellicCtec2?) to achieve sugar titers at industrial levels. The instantaneous substrate concentration was kept constant at 5% (w/v) along the fed-batch. The enzyme dosage inside the bioreactor was adjusted so that the reaction rate was not less than a pre-defined value (a percentage of the initial reaction rate ? rmin). When r reached values below rmin, enzyme pulses were applied to return the reaction rate to its initial value (r0). The optimized feeding policy indicated a reaction rate maintained at a minimum of 70% of r0, based on the trade-off between glucose productivity and enzyme saving. Initially, it was possible to process a 21% (w/v) solid load, achieving 160 g/L of glucose concentration and 80% of glucose yield. It was verified that non-productive enzyme adsorption was the main reason for some reduction of hydrolysis yield regarding the theoretical cellulose-to-glucose conversion. An increment of 30 g/L in the final glucose concentration was achieved when a lignin-blocking additive (soybean protein) was used in the enzymatic hydrolysis.

Quantifying Farmers’ Exposure to Corn and Soybean Dust in On-Farm Grain Storage Bins

HighlightsOn-farm samples were used to analyze farmers’ exposure to dust while cleaning and unloading their grain bins.Over 18% of samples exceeded the 8-hour time-weighted average (TWA) concentration recommended by ACGIH for respirable dust, and over 27% of samples exceeded the ACGIH recommendation for total suspended particles.The results strengthen the need for relevant agricultural safety education programs to help farm workers understand the health hazards associated with grain dust.Abstract. Grain dust consists of grain particles, insect parts, silica, bacteria, fungi, and mycotoxins. The size of these airborne particulates is a concern because they can become deeply lodged in the respiratory tract. Exposure to grain dust can diminish overall lung function and lead to respiratory diseases such as asthma, chronic obstructive pulmonary disease (COPD), organic dust toxic syndrome (ODTS), chronic bronchitis, and hypersensitivity pneumonitis (farmer’s lung). Grain storage and handling facilities are primary work locations with high levels of grain dust concentrations. The objective of this study was to understand farmers’ exposure to grain dust while cleaning and unloading their grain bins. During on-farm dust sampling, researchers visited farms to collect dust samples for analysis. Two types of samples were taken. Integrated samples provided average concentrations of total dust and respirable dust while farmers performed their normal tasks in the grain bin. Real-time samples provided instantaneous concentrations of respirable dust (RESP) and total suspended particles (TSP) and how the variations changed during the farmers’ working periods. From the data collected in corn storage bins, RESP concentrations ranged from 4.1 to 6.6 mg m-3, and TSP concentrations ranged from 33 to 70.7 mg m-3. From the data collected in soybean storage bins, RESP concentrations ranged from 1.6 to 82.3 mg m-3, and TSP concentrations ranged from 8.9 to 146.8 mg m-3. Based on the calculated 8-hour time-weighted average (TWA) concentration of all samples, 18.2% of the 8-hour TWA RESP concentrations exceeded the ACGIH-recommended respirable dust concentration of 3 mg m-3, and 27.3% of the 8-hour TWA TSP concentrations exceeded the ACGIH-recommended total dust concentration of 610 mg m-3. The results strengthen the need for relevant agricultural safety education programs to help farm workers understand the health hazards associated with grain dust. Keywords: Grain dust concentrations, Occupational health, On-farm grain storage bins.

Alternative Materials for the Enrichment of Biogas with Methane.

Carbonaceous adsorbents have been pointed out as promising adsorbents for the recovery of methane from its mixture with carbon dioxide, including biogas. This is because of the fact that CO2 is more strongly adsorbed and also diffuses faster compared to methane in these materials. Therefore, the present study aimed to test alternative carbonaceous materials for the gas separation process with the purpose of enriching biogas in biomethane and to compare them with the commercial one. Among them was coconut shell activated carbon (AC) as the adsorbent derived from bio-waste, rubber tire pyrolysis char (RPC) as a by-product of waste utilization technology, and carbon molecular sieve (CMS) as the commercial material. The breakthrough experiments were conducted using two mixtures, a methane-rich mixture (consisting of 75% CH4 and 25% CO2) and a carbon dioxide-rich mixture (containing 25% CH4 and 75% CO2). This investigation showed that the AC sample would be a better candidate material for the CH4/CO2 separation using a fixed-bed adsorption column than the commercial CMS sample. It is worth mentioning that due to its poorly developed micropore structure, the RPC sample exhibited limited adsorption capacity for both compounds, particularly for CO2. However, it was observed that for the methane-rich mixture, it was possible to obtain an instantaneous concentration of around 93% CH4. This indicates that there is still much potential for the use of the RPC, but this raw material needs further treatment. The Yoon–Nelson model was used to predict breakthrough curves for the experimental data. The results show that the data for the AC were best fitted with this model.