Pollutant Dispersion Research Articles

Pollutant Dispersion from a Structural Fire Accident and its Effect on the Local Environment using a CFD Model

Pollutant Dispersion from a Structural Fire Accident and its Effect on the Local Environment using a CFD Model

Evaluation of Air Pollution Levels in Agricultural Settings Using Integrated Weather Variables and Air Pollutants

Research on the quality of the air in rural areas is essential for determining base emissions of air pollutants, evaluating the effects of dust pollutants particular to rural areas, modeling the dispersion of pollutants, and developing appropriate pollution mitigation systems. The absence of a systematic review based on the assessment of air quality levels in agricultural settings based on integrated weather variables and air pollutants in the literature draws attention to the deficiencies and the necessity of further research in this area. Hence, our study aimed to develop an Arduino monitoring system with related sensors to acquire some air pollutants and weather parameters. Additionally, we proposed an innovative solution to compare air quality levels by suggesting a new criterion called an integrated indicator for air quality assessment (IAQA). It was created based on the weighted average method to combine the investigated air pollutants and weather parameters. This criterion was evaluated while conducting field measurements in 29 environmentally different agricultural regions located within the Kingdom of Saudi Arabia. To determine the integrated indicator, all the values of the variables were normalized between 0 and 1. The agricultural setting with the lowest integrated indicator was the best environmentally. The lowest and highest values of the integrated indicator ranged from 37.03% and 66.32%, respectively, with an arithmetic average of 48.24%. The developed criterion can change its value depending on the change in the weight value of the variables involved, and it is suitable for application to any other agricultural or non-agricultural setting to evaluate the pollution level in the air. Although similar research has been published, this paper presents novelty findings based on integrated values of air pollutants and weather variables for defining a new criterion called IAQA. Additionally, this paper presents original results for air pollutants and weather aspects in different agricultural settings.

Flow patterns and heat transfer of an idealized square city in non-uniform heat flux and different background wind conditions

The city scale buoyancy-driven flow is crucial for the wind and thermal environment in urban areas, exerting a significant impact on the city ventilation, pollutants dispersion and heat removal. The intra-urban variations of hot spots and heat flux are drawing more attention on beating the urban heat. This study aims at analyzing the influences of non-uniform heat flux and background wind on the city-scale heat removal ability and underlying mechanisms. The large eddy simulation model was used and verified with water tank experiments. Results show that positive heat flux and negative heat flux in the rural areas will enhance and depress the strength of the urban heat dome flow respectively compared to the adiabatic condition. The high-speed regions are wider and stronger when the rural area has positive heat flux condition. Under positive rural heat flux condition, the time-average mixed layer height in urban areas across the city center plane is nearly twice that under negative rural heat flux condition. Besides, the city-scale heat transfer coefficients in positive rural heat flux condition are higher than those under negative rural heat flux and adiabatic conditions. For cases of non-uniform heat flux in urban areas, the differences of time-average mixed layer height and heat transfer coefficients are not obvious. The heat transfer coefficients decrease initially and then increase with increasing background wind speed indicating the non-linear interaction between approaching wind and urban heat dome flow. Moreover, the growth rate of the heat transfer coefficient decreases when the non-dimensional wind speed exceeds 1.19.

Numerical study the assessment of pollutant dispersion from a thermal power plant: Impact of the wind direction, relative humidity and ambient temperatures, which vary depending on the time of day

In this paper, it was performed a numerical simulation of the spread of a pollutant - carbon dioxide from the chimneys of a thermal power plant. To determine the correctness of the models, a test problem was used, the results of which were compared with obtained numerical and experimental values. These models were used for a 3D model on a real scale of Ekibastuz SDP P, the largest thermal power station in Kazakhstan. A study on the spread of pollutants was performed within 24 hours. In addition, in the model, environmental conditions close to the real ones were used - a variable direction of the wind, a variable humidity of the ambient air, and different temperatures, which vary depending on the time of day. The results can be used in the future to study the problem of environmental pollution and reduce the consequences of the environmental situation as a whole.

Environmental conditions affecting air pollution dispersion over Richards Bay, South Africa

Air pollution dispersion over Richards Bay, South Africa is studied using satellite, reanalysis and in-situ measurements. Near-surface concentrations of trace gases and particulates reach high concentrations under dry stable ‘berg’ winds. Temporal records of CO, NO2, O3, PM2.5, SO2 (2000-2023) exhibit no trend and short-term dose exceedances of individual pollutants are rare and confined to winter mornings. Regional point-to-field correlation maps of a Richards Bay winter air pollution index found that anomalous warming of the west Indian Ocean accelerates the jet stream over Madagascar and pulls smoke- and dust-laden north-westerly winds across the South African plateau, implicating long-range transport. At daily and hourly time scales dewpoint temperature and boundary layer height best indicate changes in local air pollution dispersion that impact respiratory health. A case study of 15-17 June 2021 revealed a 10ºC thermal inversion caused by negative sensible heat fluxes of -40 W/m2 through the night, leading to SO2 concentrations above 100 ppb in the morning along the main access road (28.8ºS, 32ºE). Poor dispersion seldom happens in the summer when turbulent mixing and rainfall cleanse the air.

Contrasting effects of urban trees on air quality: From the aerodynamic effects in streets to impacts of biogenic emissions in cities

Urban trees are often not considered in air-quality models although they can significantly impact the concentrations of pollutants. Gas and particles can deposit on leaf surfaces, lowering their concentrations, but the tree crown aerodynamic effect is antagonist, limiting the dispersion of pollutants in streets. Furthermore, trees emit Biogenic Volatile Organic Compounds (BVOCs) that react with other compounds to form ozone and secondary organic aerosols. This study aims to quantify the impacts of these three tree effects (dry deposition, aerodynamic effect and BVOC emissions) on air quality from the regional to the street scale over Paris city. Each tree effect is added in the model chain CHIMERE/MUNICH/SSH-aerosol. The tree location and characteristics are determined using the Paris tree inventory, combined with allometric equations. The air-quality simulations are performed over June and July 2022. The results show that the aerodynamic tree effect increases the concentrations of gas and particles emitted in streets, such as NOx (+4.6 % on average in streets with trees and up to +37 % for NO2). This effect increases with the tree Leaf Area Index and it is more important in streets with high traffic, suggesting to limit the planting of trees with large crowns on high-traffic streets. The effect of dry deposition of gas and particles on leaves is very limited, reducing the concentrations of O3 concentrations by −0.6 % on average and at most −2.5 %. Tree biogenic emissions largely increase the isoprene and monoterpene concentrations, bringing the simulated concentrations closer to observations. Over the two-week sensitivity analysis, biogenic emissions induce an increase of O3, organic particles and PM2.5 street concentrations by respectively +1.1, +2.4 and + 0.5 % on average over all streets. This concentration increase may reach locally +3.5, +12.3 and + 2.9 % respectively for O3, organic particles and PM2.5, suggesting to prefer the plantation of low-emitting VOC species in cities.

Time series analysis of PM2.5 pollution risk based on the supply and demand of PM2.5 removal service: a case study of the urban areas of Beijing.

Demonstrating the temporal changes in PM2.5 pollution risk in regions facing serious PM2.5 pollution problems can provide scientific evidence for the air pollution control of the region. However, research on the variation of PM2.5 pollution risk on a fine temporal scale is very limited. Therefore, we developed a method for quantitative characterizing PM2.5 pollution risk based on the supply and demand of PM2.5 removal services, analyzed the time series characteristics of PM2.5 pollution risk, and explored the reasons for the temporal changes using the urban areas of Beijing as the case study area. The results show that the PM2.5 pollution risk in the urban areas of Beijing was close between 2008 and 2012, decreased by approximately 16.3% in 2016 compared to 2012, and further decreased by approximately 13.2% in 2021 compared to 2016. The temporal variation pattern of the PM2.5 pollution risk in 2016 and 2021 showed significant differences, including an increase in the number of risk-free days, a decrease in the number of heavily polluted days, and an increase in the stability of the risk day sequence. The significant reduction in risk level was mainly attributed to Beijing's air pollution control measures, supplemented by the impact of COVID-19 control measures in 2021. The results of PM2.5 pollution risk decomposition indicate that compared to the previous 2years, the stability and predictability of the risk variation in 2016 increased, but the overall characteristics of high risk from November to February and low risk from April to September did not change. The high risk from November to February was mainly due to the demand for coal heating during this period, a decrease in PM2.5 removal service supply caused by plant leaf fall, and the common occurrence of temperature inversions in winter, which hinders the diffusion of air pollutants. This study provides a method for the analysis of PM2.5 pollution risk on fine temporal scales and may provide a reference for the PM2.5 pollution control in the urban areas of Beijing.

Experimental study on the periodic pulsating ventilation by fluidic oscillator on pollutant dispersion and ventilation performance in enclosed environment

Ventilation plays an essential role in creating healthy and comfortable indoor environment, while adopting unsteady airflow field has the potential to improve the indoor air mixing effect, which is conducive to the dispersion and eventually the discharge of indoor pollutants. A fluidic oscillator capable of producing periodic pulsating airflow is employed to conduct a ventilation experiment to test the performance of such unsteady flow regime. The distribution of indoor pollutants at different source locations is compared under both steady and unsteady ventilation mode. The assessment of the fluidic oscillator ventilation system performance in eliminating pollutants involves the concentration exceedance rate, the decay of indoor pollutant concentration, and the resultant ventilation efficiency. At a relatively lower air supply rate, the fluidic oscillator device can enhance indoor air mixing, leading to a reduction of the peak indoor pollutant concentration. Additionally, the fluidic oscillator air terminal significantly prolongs the time needed to reach the pollutant concentration threshold, increases ventilation efficiency, and improves indoor air quality.

Numerical Analysis of the Effects of Different Window-Opening Strategies on the Indoor Pollutant Dispersion in Street-Facing Buildings

The idling of automobiles at street intersections can lead to pollutant accumulation which impacts the health of residents in street-facing buildings. Previous research focused on pollutant dispersion within street canyons and did not consider the coupling of indoor and outdoor pollutants. This paper employs the computational fluid dynamics (CFD) method to simulate the dispersion characteristics of vehicle emission pollutants in street canyons, primarily investigating the indoor and outdoor pollutant dispersion patterns under various window opening configurations (single-sided ventilation, corner ventilation, and different positions of the glass under corner ventilation). Additionally, the study considers the impacts of the aspect ratio and ambient wind speed. Studies have shown that corner ventilation is effective in reducing indoor pollutant levels. When the two window glass positions are far away from the center of the intersection, the average CO mass fraction in the single-sided ventilation room is reduced by 87.1%. The average indoor CO mass fraction on the leeward side decreases with the increasing wind speed and aspect ratio. At a wind speed of 8 m/s, the average indoor CO mass fraction on the leeward side decreases to 2.45 × 10−8. At an aspect ratio of 2, the indoor CO mass fraction on the leeward side decreases with increasing floors before stabilizing at approximately 4.77 × 10−9. This study suggests optimal window opening strategies to reduce indoor pollutant levels in street-facing buildings at street intersections, offering guidance to indoor residents on window ventilation practices.

Aerosol‐Cloud Interactions Near Cloud Base Deteriorating the Haze Pollution in East China

AbstractAtmospheric aerosols not only cause severe haze pollution, but also affect climate through changes in cloud properties. However, during the haze pollution, aerosol‐cloud interactions are not well understood due to a lack of in situ observations. In this study, we conducted simultaneous observations of cloud droplet and particle number size distribution, together with supporting atmospheric parameters, from ground to cloud base in East China using a high‐payload tethered airship. We found that high concentrations of aerosols and cloud condensation nuclei were constrained below cloud, leading to the pronounced “Twomey effect” near the cloud base. The cloud inhibited the pollutants dispersion by reducing surface heat flux and thus deteriorated the near‐surface haze pollution. Satellite retrievals matched well with the in situ observations for low stratus clouds, while were insufficient to quantify aerosol‐cloud interactions for other cases. Our results highlight the importance to combine in situ vertical and satellite observations to quantify the aerosol‐cloud interactions.

Experimental and numerical study on characteristics of wake and vortex structure of cluster personnel

The purpose of this study is to study the characteristics of unsteady flow field caused by human activities in crowded public space. This study analyses the wake and vortex structure characteristics of cluster personnel through experiments and numerical simulations. The wake velocity field and vortex structure of 2 (columns) × 5 (rows) human walking were analysed by experimental measurement and large eddy simulation (LES). Personnel movement is simulated by using the dynamic mesh model of computational fluid dynamics (CFD). The results show that the wake of the leg is fully developed, and the wake end presents a “swallow-tail shaped”. The rear row personnel will make a secondary disturbance to the wake of the front row personnel in the wake of the cluster personnel. Therefore, there will be a process of mutual transformation of large-scale vortices and small-scale vortices in the wake field. In addition, the wake flow significantly affects the diffusion and propagation of respiratory pollutants.

Diffusion of Municipal Waste Pollutants in Electrokinetic Lead Remediated Compacted Lateritic Soil

Diffusion of Municipal Waste Pollutants in Electrokinetic Lead Remediated Compacted Lateritic Soil

Assessing aerosol-radiation interaction with WRF-chem-solar: Case study on the impact of the “pollution reduction and carbon reduction synergy” policy

Aerosol-radiation interaction (ARI) plays an important role in air quality and climate change. The implementation of the “Pollution Reduction and Carbon Reduction Synergy (PRCRS)” policy provides a great case to explore the impact of ARI on air quality in Beijing and the surrounding Beijing-Tianjin-Hebei (BTH) region. In this study, we analyzed the pollution characteristics and their relationship with meteorological factors in the BTH region, and used the WRF-Chem-Solar model to study the impact of the ARI effect on regional meteorological conditions, air quality improvement, and renewable energy during the implementation of atmospheric pollution improvement policies based on four different scenarios. The ARI effect led to decreases in 2-m temperature, planetary boundary layer height, surface downward shortwave radiation (SWDOWN), and an increase in 2-m relative humidity. The meteorological conditions were unfavorable to the dispersion of pollutants, and the ARI effect can lead to further aggravation of pollutants. The implementation of the PRCRS policy can suppress the adverse effects of ARI on regional air pollution diffusion conditions and improve regional pollution meteorological conditions, and the ARI effect can further enhance the policy's impact on improving air quality. In terms of renewable energy, the implementation of the PRCRS policy will increase renewable energy in the BTH region, due to the inhibition of the ARI effect on SWDOWN and wind speed at 100 m.

Analysis of Sulfur Dioxide (SO2) Exhaust Gas Emission Distribution Patterns from Airport’s Incinerators in East Java

The airport in this study is one of the airports in East Java that uses an incinerator to process its waste. Emissions generated by the incinerator will disperse in the area surrounding one of the airports in East Java. With the increasing interest of the public in air travel, activity at the airport also increases. This increase also impacts the amount of waste processed by the incinerator and the emissions produced, including Sulfur Dioxide (SO2). The aim of this study is to analyze the dispersion of air pollutants using Aermod View modeling software with SO2 parameters from environmental document data of the airport from January to June and from July to December generated by the incinerator stack. The model produces isopleths representing the dispersion of SO2 emissions. The results of the SO2 model still meet ambient air quality standards, as indicated in Appendix VII of Government Regulation Number 22 of 2021.

Development of nanoscale uniform hexagonal zeolitic imidazole framework (ZIF-8) for the degradation of CAP and 5-FLU anticancer drugs

Efficiently removing pharmaceutical pollutants poses a significant challenge for traditional sewage treatment systems. This study presents the synthesis of Zeolitic Imidazole Framework (ZIF-8) using various solvents, including deionized water (DI), isopropyl alcohol (IPA), methyl ethyl ketone (MEK), acetone (ACE), and methanol (MeOH), to degrade two anticancer drugs, 5-fluorouracil (5-FLU) and capecitabine (CAP), under visible light within 80 and 70 min, respectively. Optimized ZIF-8 synthesized using MeOH exhibits uniform hexagonal morphology at the nanoscale and a larger surface area, which, along with its interactions, establishes a synergistic reinforcing mechanism. This mechanism facilitates improved access to reactive sites, enhances the diffusion of pollutants and oxidants, improves charge separation capability, and boosts light utilization efficiency. Consequently, the degradation rates of 5-FLU and CAP approached approximately 99.7 % and 97.9 % following 80 and 70 min of visible light exposure at a pH of 7 in the presence of ZIF-8 (MeOH), indicating superior photocatalytic activity. The studied ZIF-8 (MeOH) system demonstrates excellent stability, maintaining appreciable performance even under visible light for about 70 min. The predominant active species, potential decomposition pathways of CAP and 5-FLU, and the underlying reaction mechanism of the ZIF-8 (MeOH) system under visible light have been thoroughly investigated. This research significantly advances the integration of photocatalysis technology, unlocking its tremendous potential in environmental restoration.

Impact of gas dry deposition parameterization on secondary particle formation in an urban canyon

This study investigates the impact of the parameterization of dry deposition on the local gas-particle partitioning between ammonium nitrate NH4NO3 and its precursor gases (ammonia, NH3 and nitric acid, HNO3) through chemistry-coupled large-eddy simulations on the dispersion of reactive gaseous and particulate pollutant in an idealized street canyon. A key factor in the parameterization of dry deposition is the effective Henry's Law constant H*. Three distinct characterizations of H* are compared: two drawn from existing literature (referred to as Model 1 and Model 2) and one typical of low pH conditions (referred to as Model 3), which could be more representative of urban areas. Model 3 shows contrasting gas-particle partitioning results between NH3, HNO3, and NH4NO3 with Model 1 and Model 2. In detail, the NH4NO3 concentrations in the street of Model 1 and Model 2 are smaller than the background NH4NO3 concentration. However, Model 3 shows higher NH4NO3 concentration in the street than the background NH4NO3 concentration. This is because the dry deposition fluxes of NH3 and HNO3 are higher in Model 1 and Model 2 than in Model 3, resulting in less available NH3 and HNO3 for NH4NO3 formation. These findings highlight the importance of selecting an appropriate H* characterization that is tailored to the specific environmental conditions under investigation.

Influences of synoptic circulations on regional transport, local accumulation and chemical transformation for PM2.5 heavy pollution over Twain-Hu Basin, central China

The Twain-Hu Basin (THB), located in Central China, serves as a key juncture where the northerly “polluted” airflows of the East Asian winter monsoon meet the southerly warm and humid airflows. Using the T-PCA (T- Principal Component Analysis) objective synoptic pattern classification, FLEXPART-WRF (Flexible Particle Dispersion Model), and Random Forest model, we investigate the influences of synoptic circulations on regional transport, local accumulation, and chemical transformation of PM2.5 during heavy air pollution over the THB in January of 2015–2022. The results show that the transport-type synoptic pattern accounts for 65.16% of heavy PM2.5 pollution, indicating that regional transport of PM2.5 dominates the THB's heavy air pollution. The PM2.5/CO ratio is higher in the transport-type pattern and positively correlated with PM2.5 concentrations, reflecting a higher efficiency of chemical transformation to secondary PM2.5 in transport-type pollution compared with the accumulation-type pollution. Transport-type heavy PM2.5 pollution is predominantly influenced by upstream anomalous northerly and easterly airflows at the bottom of the high-pressure system, converging with the southern wind in the receptor area over the THB. Accumulation-type heavy pollution exhibits weak wind anomalies in central and eastern China under the control of a uniform pressure field. Furthermore, thermally-induced vertical circulations with sinking airflows in the middle and lower troposphere suppress the vertical air pollutant dispersions. The relative contributions of atmospheric factors for transport-type PM2.5 heavy pollution events are 38.0% for dynamical driver, 26.8% for thermal driver, and 35.1% for chemical transformation, while in accumulation-type, the contribution rates are 33.9%, 36.3%, and 29.7%, respectively. This study elucidates the influences of synoptic patterns on regional transport, local accumulation, and chemical transformation of PM2.5 for heavy air pollution, with implications for understanding changes of air quality in the receptor region of regional transport.

Limitation on the Number of Groundwater Well Pumps in the Coastal Area of Ternate Island

The hydrogeological characteristics of small volcanic islands possess unique attributes. Groundwater flow patterns descend radially and converge in coastal aquifers. The uneven distribution of coastal aquifers sometimes leads communities to extract groundwater from specific points. A notable phenomenon observed in the study area is the presence of dug wells with multiple water pumps. If the combined suction capacity of these pumps exceeds the allowed limit, it has the potential to cause the mixing of saltwater with freshwater. This study utilizes geoelectric methods to delineate the groundwater-saltwater interface beneath the surface. The groundwater-saltwater interface can also be calculated using equations. By knowing the well positions with multiple pumps, it is possible to calculate the allowable number of pumps. The calculations yield a limit of up to 31 pumps per dug well, thereby mitigating the risk of saltwater intrusion. Furthermore, data on the dug well positions within the study area are used to create groundwater table contours and flow models, aiding in the analysis of saltwater pollutant dispersion in the event of intrusion.

Mixed response of trace element concentrations in fluvial sediments to a flash flood in a former mining area

BackgroundFloods, especially flash floods, are the major transporting agent for fluvial sediments, whose pollution is a global concern. As floods result in the dispersion of and exposure to these sediments, a profound understanding of sedimentary dynamics during flood events and the related pollutant dispersion is of relevance. However, the characteristics of extreme flood events concerning pollutant dynamics are insufficiently known so far.ResultsIn a Central European catchment impacted by intense industrial activities and former mining, over the course of five years, we surveyed six high-discharge events, five of them approx. bankfull discharge and one major flash flood event, supplemented by sampling of bank sediments. Fluvial sediments were analyzed for elemental composition by X-Ray fluorescence and for grain size distribution of the fine faction by laser diffraction. By applying a local enrichment factor, trace metal(loid) signatures in these sample sets were compared. Furthermore, Positive Matrix Factorization was used to investigate the trace metal(loid)s’ sources.The sediments deposited by minor flooding had continual trace metal(loid) signatures. However, for the extreme event, significant divergencies arose and persisted for the following years: The enrichment of anthropogenically influenced elements increased, with a slowly decreasing trend in the subsequent two years. Naturally dominated metal(oid)s decrease in enrichment without indicating a return to original levels. In contrast, other elements were insensitive to the extreme event. Positive Matrix Factorization identified anthropogenic influences in elements originating from copper and lead processing and mining activities. Furthermore, bed sediments and a natural background factor were found to dominate the non-anthropogenically influenced metal(loid)s.ConclusionsIn between extreme events, winnowing processes slowly alter the elemental composition of bed sediments. The depletion of such sediments due to the flash flood proves catchment-wide flushing, which induces a natural resetting of the geochemical signals. This ability to renew is an integral part of resilience in fluvial systems. This mechanism is disturbed by industrial activities in floodplains. The exceptional flooding reaches infrastructure that is assumed to be safe and, therefore, unprotected. These additional sources can shift flood sediments’ trace metal(loid) signature, which has a long-lasting impact on the catchment sediments. However, the modifications depend on the flooding extent, possible emitters, and protection measures.

Impact of Meteorological Conditions on PM2.5 Pollution in Changchun and Associated Health Risks Analysis

The escalating concern regarding increasing air pollution and its impact on the health risks associated with PM2.5 in developing countries necessitates attention. Thus, this study utilizes the WRF-CMAQ model to simulate the effects of meteorological conditions on PM2.5 levels in Changchun, a typical city in China, during January 2017 and January 2020. Additionally, it introduces a novel health risk-based air quality index (NHAQI) to assess the influence of meteorological parameters and associated health risks. The findings indicate that in January 2020, the 2-m temperature (T2), 10-m wind speed (WS10), and planetary boundary layer height (PBLH) were lower compared to those in 2017, while air pressure exhibited a slight increase. These meteorological parameters, characterized by reduced wind speed, heightened air pressure, and lower boundary layer height—factors unfavorable for pollutant dispersion—collectively contribute to the accumulation of PM2.5 in the atmosphere. Moreover, the NHAQI proves to be more effective in evaluating health risks compared to the air quality index (AQI). The annual average decrease in NHAQI across six municipal districts from 2017 to 2020 amounts to 18.05%. Notably, the highest health risks are observed during the winter among the four seasons, particularly in densely populated areas. The pollutants contributing the most to the total excess risk (ERtotal) are PM2.5 (45.46%), PM10 (33.30%), and O3 (13.57%) in 2017, and PM2.5 (67.41%), PM10 (22.32%), and O3 (8.41%) in 2020. These results underscore the ongoing necessity for PM2.5 emission control measures while emphasizing the importance of considering meteorological parameters in the development of PM2.5 reduction strategies.