Mean Concentrations Of Pollutants Research Articles

Pollutants In the Selected 3 – Bus Station Microenvironments in Enugu Metropolis

Idling buses in bus station micro-environments potentially pollute ambient air with health implications for commuters with long waiting times. This study aimed at finding the severity of air pollutants in selected three bus station microenvironments in Enugu metropolis, South Eastern Nigeria with the objective to determine the air quality index. Real time measurements of ambient particulates (PM10 and PM2.5) and gaseous pollutants such as SO2, NO2 and CO were monitored, in conjunction with meteorological parameters (wind speed, temperature and relative humidity) on idling buses in selected three bus stations and a control station in Enugu Metropolis. The study spanned through September 2016 to August 2018, covering dry and wet seasons. Hand-held Aeroqual Series - 200 gas monitor/sensors, particulates laser meter and ambient weather anemometer were used to collect data. Results indicated that the daily highest mean concentrations of pollutants were as follows: PM10=228µg/m3 – Young Shall Grow; PM2.5=99.5µg/m3 – Young-Shall-Grow; SO2=0.81ppm – Ifesinachi; NO2= 0.068ppm – Young-Shall-Grow; CO= 7.376ppm – ABC, consistently maintained higher concentrations than those at the control station. AQI was calculated with AQI calculator. The air quality index (AQI) results showed a severe health issue in the selected 3-bus station micro environments. This implies that commuters are highly at risk if they cluster idling buses at bus stations. This study can assist the relevant authorities to set strict ambient air quality objectives for pollutants in transport micro environments.

The NOx-O3 photochemical reactive air pollutant dispersion around an isolated building—the role of turbulence model and building aspect ratio

The NOx-O3 photochemical reactive air pollutant dispersion around an isolated building bears significant scientific and engineering implications. The present work extends the investigation to the role of turbulence models and building aspect ratio, providing valuable insights for future numerical investigations and building complex design. Validated against wind tunnel experiments, a serial Computational Fluid Dynamics (CFD) investigation was conducted with physiochemical coupling, including one large eddy simulation with near-wall resolution (LES-NWR) and three Reynolds-averaged Navier-Stokes (RANS) viscosity models (i.e., standard k-ε model (STK), renormalization group k-ε model (RNG), realizable k-ε model (RLZ)). The numerical models were assessed regarding the predictive capability of the mean pollutant concentration and velocity fields. Results show that the areas of high NO concentration are generally indifferent to the selection of turbulence models. Elsewhere, the RLZ provides the most comparable results to the LES-NWR, whereas the RNG and STK underestimate the reverse flow in the building wake and produce subpar predictions at the roof. The RNG also yields the weakest prediction by overestimating the lateral separation bubbles’ influence. Furthermore, changing the aspect ratio has negligible effects on the stream and spanwise dispersion of the highly concentrated pollutant. However, the building width plays a more decisive role in constraining the streamwise dispersion than the building height. Doubling the building length also slows down the shrinkage of recirculation, leading to a steep deduction in the streamwise dispersion along the building height.

Variability of traffic-related air pollutants at two- and four-phase intersections

Traffic intersections are the hotspots of air pollution. However, pollutant variation patterns at signalized intersections remain less explored. In this study, field measurements were conducted to investigate the pollutant variability at two- and four-phase intersections in Beijing, China. Spikes were frequently observed in pollutant concentrations at a fine-temporal (1-HZ) scale that could be well-characterized using Gaussian peak functions. The mean pollutant concentrations at two-phase intersections peaked under the green signal light and decreased exponentially under the red signal light. Pollutant concentrations were significantly influenced by the signal control pattern, which higher pollutant concentrations were observed during the pedestrian-waiting phase at the two-phase intersection and during the cross-walking phase at the four-phase intersection. Additionally, intersections with shorter signal light times result in insufficient pollutant dispersion and more frequent stop-and-go by vehicles. Nevertheless, the traffic volume is the dominant factor for a higher pollution level. These results broaden our knowledge of pollutant variability at signalized intersections and have implications for the mitigation of traffic-related air pollution.

Influence of the Bed Temperature on the Operational Reliability of a Hybrid Constructed Wetland Wastewater Treatment Plant in South-Western Poland—A Case Study

The aim of this study was to assess the influence of atmospheric air temperature on the efficiency and reliability of pollutants removal from wastewater. The studied facility was a hybrid constructed wetland wastewater treatment plant with vertical and horizontal flow serving a single-family building in the village of Krajanów in south-western Poland. The operation of the facility was evaluated on the basis of studies conducted in 2021–2022. The tests included a physico–chemical analysis of wastewater treated mechanically in a settling tank and effluents from constructed wetland beds with the vertical and horizontal flow. The following parameters were determined: BOD5, COD, total suspended solids, total nitrogen, and total phosphorus. No statistically significant effect of air temperature on the analyzed pollutants removal levels was found. The temperature in the soil–plant bed never fell below 0 °C, and so the wastewater flowing through the beds never froze. The discussed facility was characterized by high efficiency and reliability of the tested pollutants removal across the seasons. The mean concentrations of pollutants in treated wastewater did not exceed the limit values specified in the currently binding legal act. It was shown that hybrid constructed wetlands can be successfully used for wastewater treatment in the climatic conditions of southern Poland.

Allergic rhinitis children with obesity are more vulnerable to air pollution: a cross sectional study

The association between air pollution, allergic rhinitis (AR), and obesity has not been studied. From 2007 to 2011, 52 obese and 152 non-obese children (7–17 years old) with AR were recruited. Pediatric-Rhinoconjunctivitis-Quality-of-Life Questionnaire (PRQLQ) and nasal peak expiratory flow (NPEF) were tested. Association between the scores and rates of the two tests and mean air pollutant concentrations within 7 days before the tests were compared. When exposed to higher concentrations of CO, PM10, and PM2.5, the rates of worse nasal discomfort were 39.4%, 44.4% and 39.3% in obese children; and 18.0%, 21.9% and 19.7% in non-obese children, respectively. Compare to non-obese children, the rates in obese children were higher for CO (odds ratio (OR) 3.54, 95% confidence interval (CI) 1.15 ~ 10.92); PM10 (OR 3.26, 95% CI 1.01 ~ 10.57) and PM2.5 (OR 3.30; 95% CI 1.03 ~ 10.54). In obese children, correlations between higher concentrations of CO, PM10, PM2.5 and higher nasal discomfort (higher PRQLQ); and correlations between higher concentrations of CO, PM10, PM2.5, NMHC (non-methane hydrocarbon) and higher nasal mucosa inflammation (lower NPEF) were noted. Obesity negatively affected AR severity when AR children experienced higher concentrations of CO, PM10, and PM2.5. Increased nasal inflammation induced by air pollutants might be the underlying mechanism.

Short-term impact of noise, other air pollutants and meteorological factors on emergency hospital mental health admissions in the Madrid region

BackgroundA number of environmental factors, such as air pollution, noise in urbanised settings and meteorological-type variables, may give rise to important effects on human health. In recent years, many studies have confirmed the relation between various mental disorders and these factors, with a possible impact on the increase in emergency hospital admissions due to these causes. The aim of this study was to analyse the impact of a range of environmental factors on daily emergency hospital admissions due to mental disorders in the Madrid Autonomous Region (MAR), across the period 2013–2018. MethodologyLongitudinal ecological time series study analysed by Generalised Linear Models with Poisson regression, with the dependent variable being daily Emergency Hospital Mental Health Admissions (EHMHA) in the MAR, and the independent variable being mean daily concentrations of chemical pollutants, noise levels and meteorological variables. ResultsEHMHA were related statistically significantly in the short term with diurnal noise levels. Relative risks (RRs) for total admissions due to mental disorders and self-inflicted injuries, in the case of diurnal noise was RR: 1.008 95%CI (1.003 1.013). Admissions attributable to diurnal noise account for 5.5% of total admissions across the study period. There was no association between hospital admissions and chemical air pollution. ConclusionNoise is a variable that shows a statistically significant short-term association with EHMHA across all age groups in the MAR region. The results of this study may serve as a basis for drawing up public health guidelines and plans, which regard these variables as risk factors for mental disorders, especially in the case of noise, since this fundamentally depends on anthropogenic activities in highly urbanised areas with high levels of traffic density.

CFD modeling on the canyon ventilation and pollutant exposure in asymmetric street canyons with continuity/discontinuity balconies

Balconies have significant impacts on the ventilation and pollutant dispersion inside the street canyon. However, as the balconies used in previous studies are continuity balconies, it cannot accurately describe the effects of balconies in a real street canyon with discontinuity balconies. This paper approaches the actual situation by exploring the effects of discontinuity balconies and their locations on the ventilation and pollutant exposure inside the asymmetric canyons. We found that discontinuity balconies significantly improve the ventilation and pollutant dispersion by allowing more fresh air to enter the canyon compared to continuity balconies. ACH (air exchange rate) values of the asymmetric canyons are the lowest when balconies are located at both buildings and are the highest when balconies are at only low building. Also, the effects of discontinuity balconies are more dominant for the step-up canyon. When balconies are located on both buildings, ACH values of the step-up and step-down canyons with continuity balconies are reduced by 89.0% and 94.4% of regular canyons without balconies, but they stay at 93.4% and 96% for the case of discontinuity balconies. In addition, the discontinuity balconies significantly reduce the pollutant exposure risk level for pedestrians and first-floor residents, compared to continuity balconies. Notably, the influence of discontinuity balconies is more pronounced at the canyon center than at the canyon laterals, so mean pollutant concentrations at the center of the wall are considerably reduced. That is, previous studies have overestimated the effects of balconies. These findings can contribute to deep understanding of the effect of balconies on the urban canyon design.

Assessment of Ambient Air Pollution Pattern in Ikpeshi Community Edo State Nigeria Using Geostatistical Analysis

Understanding the Spatial distribution of ambient air quality in an active mining and solid mineral processing community is important in order to determine pollution hot spots and cold spots, as well as the trend. This will help Air Quality Managers to evaluate areas that are highly exposed to air pollution for mitigation purposes. In this study, dust particles in the form of ambient PM2.5, and PM10 were measured on weekly basis for a period of one year at 73 sampling points located in Ikpeshi, a mining and mineral processing community in Edo State, Nigeria using Double Parameter HoldPeak HP-5800D model Laser PM2.5 Meter. Geospatial data was also collected by means of Garmin GPSmap 78s model. The PM2.5 and PM10 data were preprocessed in MS Excel 2010 computer software to obtain the mean pollutant concentrations for the two parameters. The mean PM concentrations were analyzed and mapped using ArcGIS 10.0 software to generate various geostatistical surfaces to describe the ambient air pollution pattern and spatial distribution of pollutants in the community. The predicted mean concentrations ranged from 5.25 to 88.75µg/m3 for PM2.5 and 8.15 to 552.85µg/m3 for PM10. Mann-Kendall’s test showed that the observed pattern in ambient air quality exhibits a linear trend at 5% significant level with pollution hot spots found in the South-Eastern part of the community where the mills and quarries are domiciled while the cold spots appeared in the residential areas found in the North-Western part of the community. It was therefore concluded that the ambient air pollution pattern in the study area exhibits a linear south-east to north-west trend which is statistically significant at 5% level.

Effects of void deck on the airflow and pollutant dispersion in 3D street canyons.

In general, urban canyons are the areas most clearly affected by traffic pollutants since the ability of the canyon to self-ventilate is inhibited due to blockage of buildings or other urban structures. However, previous studies have aimed to improve the pedestrian-level wind speed with void deck in single buildings or short canyons. This study investigated the effects of void deck height and location, and the building height on the airflow field and the traffic pollutant diffusion in a long canyon with L/H = 10, validated by wind-tunnel experiment data. The results show that the void decks have a significant effect on the airflow and pollutant distribution inside the canyon. Air exchange rates (ACH) of the canyons with the void deck are much larger than that of regular canyons, and the perturbation changes of turbulence (ACH′) decrease. For the windward void deck, purging flow rate (PFR) and normalized net escape velocity (NEV*) increase by 6.4 times compared to the regular canyon, and for the leeward void deck, increase by 13 times. In particular, when the void decks are at both buildings, they are increased by 38.3 times. Also, for the canyons with the void deck, traffic pollutants are removed out of the canyon by the strong airflow through the void deck. Therefore, unlike the regular canyons, as the void deck and the building height increases, the strength of the airflow through the void deck becomes stronger, and as a result, the mean pollutant concentration is significantly reduced at both walls and the pedestrian respiration level. The mean pollutant concentration on the wall of the building with the void deck and on the pedestrian respiration plane close to it is near zero. These findings can help ease traffic pollution inside the street canyons composed of high-rise buildings, especially in tropical cities.

Impact of moving traffic on pollutant transport in street canyons under perpendicular winds: A CFD analysis using large-eddy simulations

• One-way traffic has stronger influences on pollutant dispersion than two-way traffic • The influence of traffic motion is noticeable under a low approaching wind speed • At U 10 = 2 m/s, the net pollutant flow rate at the side can be increased by 14 times • Traffic density plays a much less role than traffic direction and wind speed • Considering traffic motion is essential for accurate predictions of urban pollutant In urban street canyons, wind and vehicle motions jointly influence the pollutant dispersion. The present study systematically investigated the impact of (i) traffic direction, (ii) traffic density, and (iii) approaching wind speed on the mechanism of pollutant dispersion. Large-eddy simulations were performed for a street canyon with an aspect ratio of unity under two-lane traffic flow. Results show that two-lane traffic moving in the opposite direction insignificantly affects the mean pollutant concentrations inside the canyon, with a change in the net pollutant flow rate by less than 7%. However, traffic moving in the same direction strongly modify the local mean pollutant concentration, especially under a low approaching wind speed. Under the wind with a 10-meter speed of 2 m⋅s −1 , one-way traffic plays a dominant role in determining the concentration pattern, shifting the region with the maximum pollutant concentration from the center to the corner downstream of the traffic direction. The absolute net pollutant outflow rate at the canyon's lateral opening downstream of the traffic direction is increased by about 14 times, which is caused by the outflow convective pollutant flux. Findings here suggest numerical studies that neglect traffic motion can erroneously predict the local pollutant concentration in street canyons.

Horse Racing as a Model to Study the Relationship between Air Pollutants and Physical Performance.

Simple SummaryAmbient air contains a mixture of pollutants, the effects of which on animal and human health have been widely described. In contrast, the effects on physical performance are poorly understood, largely due to the difficulty of implementing an experimental model to study this problem. Thoroughbred horse racing involves many animal athletes, of similar genetics, environmental exposure, training, and diet, who participate by breathing varying mixtures of ambient air. This paper presents an analysis strategy based on the homogeneity of the races, the distance, and the design of the track. This paper presents a preliminary analysis in which we observe that the level of performance is decreased by concentrations of PM10, PM2.5, NO2, NO, and CO in the air. Thus, we note that this natural experiment may constitute a model of interest to advance the understanding of the problem.This study proposes the theoretical principles for the selection of a sample of horse races to study the relationship between air pollutants and performance. These criteria were then applied to an original dataset comparing the correlations between these variables obtained in “Handicap” versus “Conditional” type races. Methods: The mean concentration of pollutants during the six hours prior to the race and the speed of the test were determined in 441 official races at a racecourse in Santiago, Chile, during the summer and winter months of 2012. Using layout, track condition and distance (1000, 1100 and 1200 m) as criteria, a homogeneous group of races (“Handicap”; n = 214) versus a heterogeneous group (“Conditional”; n = 95) were compared using simple correlations (Spearman’s test). Results: Race speed was related to greater levels of PM10, PM2.5, NO2, NO and SO2 and it was positively related to O3, a trend that was observed in the 1000, 1100 m races and in the total “Handicap” group. Similar results were observed only in 1000 m for the “Conditional” group with lower Rho, except for PM10 and PM2.5. The total races of the conditional group showed lower Rho values and significant associations of the same trend for CO, NO2, NO and SO2. Conclusions: Horse races between 1000 and 1200 m of the “Handicap” type appear to be an interesting group to study the relationship between air pollutants and the performance of racehorses. In the future, our observations should be expanded to other distances and other types of races.

Estimation of pollutant dispersion around a building within non-isothermal boundary-layer using detached eddy simulation

The paper presents the numerical results of modelling pollutant transport from a low source behind a bluff-body imitating a building within a non-isothermal boundary-layer. The main goal of the study is to estimate the tracer gas dispersion in a complex turbulent separated flow behind a building in the presence of interference of the atmospheric boundary-layer and local flows. In the first part of the study we compare numerical approaches URANS and IDDES for turbulent flow prediction on a configuration for which experimental data are available. It is shown that detached eddy simulation approach predicts correctly the main separated flow features and demonstrates a reliable correlation with the experimental data on mean velocity, pollutant concentration and temperature fields. In the second part of the study, the influence of unstable thermal stratified flow on the tracer gas transport around a building is analyzed using IDDES method. The unstable thermal flow regime considered in the study affects the distribution of the pollutant concentration in the re-circulation zone behind the building. The presence of additional buoyancy effects leads to an increase in the gas concentration on the leeward wall of the body and gas transport from a ground region to a height greater than in the case with the neutral boundary-layer.

Impact of building façade geometrical details on pollutant dispersion in street canyons

The present study investigates the impact of building façade geometrical details on the pollutant transport mechanism in long street canyons. Large-eddy simulations (LES), extensively validated with experiments, are performed for four cases: (i) street canyon without façade balconies, (ii) street canyon with balconies at both windward and leeward façades, (ii) street canyon with balconies only at the windward façade and (iv) street canyon with balconies only at the leeward façade. The results show that the building balconies can strongly affect the wind flow field and pollutant dispersion in long street canyons. The most significant impact is observed for the two street canyon cases with balconies at the windward façade, which strongly obstruct the airflow from penetrating deep into the bottom of the canyon. The presence of balconies only at the windward façade and at both façades can increase the area-weighted mean pollutant concentration in the vertical center plane inside the canyon by 80% and 106%, respectively, and reduce the mean pollutant exchange velocity (Ue) by 46% and 54%, respectively. The analysis of the vertical mean convective and turbulent mass fluxes indicates that the presence of balconies mainly decreases the convective contribution to Ue, while the impact on the turbulent contribution is smaller.

CFD simulations of wind flow and pollutant dispersion in a street canyon with traffic flow: Comparison between RANS and LES

• CFD simulations for a street canyon with moving traffic are systematically validated. • Among the five RANS models, SKE has the best performance against wind tunnel data. • All RANS models overestimate pollutant concentration near moving traffics. • LES outperforms the RANS simulation in predicting mean velocity and concentration. • Pollutant concentrations are strongly affected by turbulent diffusion fluxes. The dispersion of traffic pollutants in street canyons takes place under the joint influence of the urban morphology and traffic-induced air motions. Computational fluid dynamics (CFD) are increasingly used to explore air quality problems in cities, however, numerical setup guidance for studies considering moving traffics remains missing. This study presents a systematic evaluation and comparison of steady Reynolds-averaged Navier-Stokes (RANS) and large-eddy simulation (LES) in reproducing the wind flow and pollutant dispersion in a street canyon under traffic flow using the quasi-steady method. The RANS simulations are performed with five turbulence models, and the standard k-ε (SKE) turbulence model is found to yield the best agreement with the wind-tunnel data. The LES simulation with the wall-adapting local eddy-viscosity subgrid-scale model outperforms all RANS models in simulating the mean velocity and mean pollutant concentration, and can accurately predict the turbulent velocity. The counter-gradient turbulent mass flux captured by LES reveals that the gradient-diffusion hypothesis used in steady RANS fails in the regions near moving traffics, which strongly affects the predicted mean concentration. The findings of this study can support future CFD studies on pollutant dispersion in urban environments.

Short-term air pollution exposure and COVID-19 infection in the United States

The Sars-CoV-2 disease (known as COVID-19) has become a global public health emergency. Researchers have been unveiling the transmission mechanisms and disclosing possible contributing factors. Studies have theorized plausible linkage mechanisms between air pollution exposure and COVID-19 infection and have divided the air pollution exposure into two types: long-term exposure and short-term exposure. However, present studies on impacts of short-term exposure have not reached a conclusive result and are mostly focusing on Asian and European countries. In this study, we conduct a nationwide analysis to examine the association between short-term air pollution exposure and COVID-19 infection in the United States. Daily confirmed cases, air pollution information, and meteorological factors at the county level were collected between March 1st and June 30th, 2020. A total of 806 (out of 3143) counties were included in this study, with 554 counties for PM2.5 and 670 counties for ozone (O3), which account for around 2.1 million cumulative confirmed cases, i.e., about 80% of all confirmed cases in the U.S. over the study period. A generalized additive model was applied to investigate the relationship between short-term exposure to PM2.5/O3 and COVID-19 confirmed cases. The statistically significant results indicate that, with every 10 μg/m3 increase in mean pollutant concentration, the number of daily confirmed cases increases by 9.41% (CI: 8.77%–10.04%) for PM2.5 and by 2.42% (CI: 1.56%–3.28%) for O3. The relative risks associated with short-term PM2.5 exposure remain positive after isolating the impacts of long-term exposure. The results of this study suggest that short-term exposure to air pollution, especially to PM2.5, may contribute to the spread and course of the pandemic. This finding has important implications for policymakers and the public to take preventive measures such as staying at home on polluted days while improving ventilation indoors to lower the probability of infection.

A STUDY ON AMBIENT AIR POLLUTION AND HOSPITAL VISITS OF PATIENTS IN TERTIARY HOSPITAL AT NORTH CHENNAI – AN OBSERVATIONAL STUDY

BACKGROUND: Air pollution is an important environmental risk factor for human health. Evidence is mounting that ambient air pollution exposure is signicantly associated with respiratory diseases. Ambient air pollution, such as nitrogen dioxide (NO2), sulfur dioxide (SO2), and particulate matter (PM), is associated with mortality and morbidity induced by respiratory diseases. The relationship between air pollutants and respiratory hospital admissions has been reported both in developed countries and in developing countries. Other studies have shown an adverse effect of ambient air pollution exposure on morbidity and mortality, as well as on healthcare costs. AIM OF THE STUDY: To investigate the association between ambient air pollutant exposure and daily hospital admissions for respiratory diseases in both childrens and Adults. METHODOLOGY: The daily emergency hospital admissions for respiratory conditions in the north part of Chennai during 2019- 2020 were recorded. Daily counts of hospital admissions for total respiratory conditions (43 admissions day(-1)), acute respiratory infections including pneumonia (18 day(-1)), chronic obstructive pulmonary disease (COPD) (13 day(-1)), and asthma (4.5 day(-1)) among residents of all ages and among children (0-14 yrs) were analysed. The generalized additive models included spline smooth functions of the day of study, mean temperature, mean humidity, inuenza epidemics, and indicator variables for days of the week and holidays. Total respiratory admissions were signicantly associated with the same-day level of NO2 (2.5% increase per interquartile range (IQR) change, 22.3 microg x m(-3)) and CO (2.8% increase per IQR, 1.5 mg x m(-3)). RESULTS: The daily mean concentrations of pollutants across all studies were 65.2 µg/m3 for PM10, 45.8 µg/m3 for PM2.5, 27.7 µg/m3 for SO2, 35.0 µg/m3 forNO2and1698µg/m3for CO, and 81.1µg/m3for O3. For the single variable models, the linear effect of PM10, PM2.5, and PM1 was evaluated by adjusting for the inuence of temperature. The association between hospital admissions for respiratory disease and the level of particulate matter was statistically signicant at 0-3 daylag in females and overall. In males, no statistically signicant effect was found at lag 3 for PM10 or at lag2-3 for PM2.5 and PM1.The associations between PM2.5 and PM1, and risk of admission were no longer signicant at some lags after adjusting for NO2, SO2, CO, and O3 separately. No associations were found at lag 3 after adjusting for NO2 or at lag 2 and 3 after adjusting for O3. The effects of PM2.5 and PM1 were not changed after adjusting for CO but were weaker after adjusting for other air pollutants (NO2, SO2,and O3). CONCLUSION: The ndings of this study demonstrated that O3 was associated with an increased risk of respiratory-related admissions, especially for children <5years old. The effect was stronger in the winter than in the summer with each increase of 10 µg/m3 of O3 in winter, the risk of admissions for respiratory diseases after 5 days of exposure increased by 6.2% (95% CI3.7% - 8.8%). No signicant association between O3 and hospital admissions for wheeze-associated disorders specically was observed in children.

Carpark pollutant yields from first flush stormwater runoff

Stormwater runoff from carparks should be treated to remove pollutants before they enter urban waterways; however, differences in traffic characteristics and surrounding land use activities can result in varying first flush pollutant types and concentrations requiring specific treatment approaches. An understanding of potential variations in first flush pollutant characteristics from carparks is necessary to design adequate treatment systems. Stormwater runoff from over 20 runoff events in three different carparks (university, hospital and industrial) in Christchurch, New Zealand were thus analyzed for Total Suspended Solids (TSS) and heavy metals (Zn, Cu and Pb) over a year. Pollutant concentrations were found to vary across the carparks, which were largely driven by land use activities such as traffic count, size of the vehicles, and surrounding topography. Mean concentrations of heavy metals (both dissolved and particulate) and TSS were significantly higher in the industrial carpark than in the other two urban carparks, which had statistically similar mean pollutant concentrations. Specific ratios of metal species (Zn:Cu, and Zn:Pb) were relatively high for the industrial carpark, indicating a greater contribution from the wear and tear of large commercial vehicles. TSS and total Zn wash-off concentrations from the hospital carpark when it was non-operational (passive) were found to be significantly lower than the hospital carpark when it was operational (active), confirming that pollutant concentrations increase with vehicular activity. Rainfall characteristics such as antecedent dry days and rain intensity and duration were found to only have a low positive correlation to pollutant concentrations for all carparks. The findings from this study highlight the importance of considering carpark characteristics in the implementation of on-site stormwater treatment systems.

Development of season-dependent land use regression models to estimate BC and PM1 exposure

Reliable estimation of exposure to black carbon (BC) and sub-micrometer particles (PM1) within a city is challenging because of limited monitoring data as well as the lack of models suitable for assessing the intra-urban environment. In this study, to estimate exposure levels in the inner-city area, we developed land use regression (LUR) models for BC and PM1 based on specially designed mobile monitoring surveys conducted in 2019 and 2020 for three seasons. The daytime and nighttime LUR models were developed separately to capture additional details on the variation in pollutants. The results of mobile monitoring indicated similar temporal variation characteristics of BC and PM1. The mean concentrations of pollutants were higher in winter (BC: 4.72 μg/m3; PM1: 56.97 μg/m3) than in fall (BC: 3.74 μg/m3; PM1: 33.29 μg/m3) and summer (BC: 2.77 μg/m3; PM1: 27.04 μg/m3). For both BC and PM1, higher nighttime concentrations were found in winter and fall, whereas higher daytime concentrations were observed in the summer. A supervised forward stepwise regression method was used to select the predictors for the LUR models. The adjusted R2 of the LUR models for BC and PM1 ranged from 0.39 to 0.66 and 0.45 to 0.80, respectively. Traffic-related predictors were incorporated into all the models for BC. In contrast, more meteorology-related predictors were incorporated into the PM1 models. The concentration surface based on the LUR models was mapped at a spatial resolution of 100 m, and significant seasonal and diurnal trends were observed. PM1 was dominated by seasonal variations, whereas BC showed more spatial variation. In conclusion, the development of season-dependent diurnal LUR models based on mobile monitoring could provide a methodology for the estimation of exposure and screening of influencing factors of BC and PM1 in typical inner-city environments, and support pollution management.

Changes in short-lived climate pollutants during the COVID-19 pandemic in Tehran, Iran.

This study investigates the changes of short-lived climate pollutants and other air pollutants during the COVID-19 pandemic in Tehran, Iran. Concentrations of air pollutants were obtained from 21 monitoring stations for the period from 5 January 2019 to 5 August 2019, representing normal conditions unaffected by COVID-19, and the period 5 January 2020 to 5 August 2020, i.e., during the COVID-19 crisis. We concentrated our analysis on three time windows (23 February 2020 to 15 March 2020, 18 March 2020 to 3 April 2020, and 5 April 2020 to 17 April 2020) during the lockdown when different sets of measures were taken to limit the spread of COVID-19. In comparison to the period not affected by COVID-19 measures, mean concentrations of pollutants were increased during the first lockdown period; when the number of COVID-19 patients increased sharply compared to the other periods, the mean surface concentrations of NO2, SO2, and CO were decreased and concentrations of other pollutants (i.e., O3, PM10, and PM2.5) were increased during the second lockdown period compared to the corresponding period in 2019. In the third period, the mean concentrations were decreased compared to the corresponding period in 2019. For the full period, decreases in mean concentrations of O3, NO2, SO2, CO, and PM10 and increases in PM2.5 were observed during the COVID-19 crisis, compared to 2019. Overall, the strongest reductions, 12% and 6%, respectively, were observed for CO and NO2, pointing to reduced emissions from traffic as a result of lockdown measures. The concentrations of other pollutants changed little, suggesting that the lockdown measures did not result in strong changes in the emissions from stationary sources.

Clean air in cities: Impact of the layout of buildings in urban areas on pedestrian exposure to ultrafine particles from traffic

Traffic-related pollutant concentrations are typically much higher in near-roadway microenvironments, and pedestrian and resident exposures to air pollutants can be substantially increased by the short periods of time spent on and near roadways. The design of the built environment plays a critical role in the dispersion of pollutants at street level; after normalizing for traffic, differences of a factor of ~5 have been observed between urban neighborhoods with different built environment characteristics. We examined the effects of different built environment designs on the concentrations of street-level ultrafine particles (UFP) at the scale of several blocks using the Quick Urban and Industrial Complex (QUIC) numerical modeling system. The model was capable of reasonably reproducing the complex ensemble mean 3D air flow patterns and pollutant concentrations in urban areas at fine spatial scale. We evaluated the effects of several built environment designs, changing building heights and spacing while holding total built environment volumes constant. We found that ground-level open space reduces street-level pollutant concentrations. Holding volume/surface area constant, tall buildings clustered together with larger open spaces between buildings resulted in substantially lower pollutant concentrations than buildings in rows. Buildings arranged on a ‘checkerboard’ grid with smaller contiguous open spaces, a configuration with some open space on one of the sides of the roadway at all locations, resulted in the lowest average concentrations for almost all wind directions. Rows usually prohibit mixing for perpendicular and oblique wind directions, even when there are large spaces between them, and clustered buildings have some areas where buildings border both sides of the roadways, inhibiting mixing. The model results suggest that pollutant concentrations drop off rapidly with height in the first 10 m or so above the roadways. In addition, the simulated vertical concentration profiles show a moderate elevated peak at the roof levels of the shorter buildings within the area. Model limitations and suggestions both for urban design are both discussed.