Reduction Of Pollutant Concentrations Research Articles

Horizontal-flow constructed wetlands by phytoremediation using vetiver grass, common reed, and canna lily as tertiary wastewater treatment for the reduction of pollutant concentrations of ammonia, phosphates, and nitrates

Abstract The discharge of untreated wastewater into rivers and water bodies poses significant environmental and public health risks. High concentrations of contaminants like heavy metals and pharmaceuticals disrupt rivers, exacerbating waterborne diseases, and leading to unsafe water in the Philippines. This study proposed the use of horizontal-flow constructed wetlands as a tertiary treatment method utilizing the plants: vetiver grass, common reed, and canna lily, to reduce pollutant concentrations in wastewater. This is to ensure compliance with water quality guidelines and general effluent standards under the Class SB Category, water suitable for fishery, tourist zones, and recreational activities. The research investigated the efficiency of phytoremediation beds in removing pollutants from wastewater under fixed hydraulic retention times. The efficiency of reducing pollutants and adsorption isotherms (Freundlich and Langmuir) were calculated to analyze the results of the sampling. Phytoremediation bed 1 demonstra ted efficient ammonia removal by 64.64%. Phytoremediation bed 2 was proficient in reducing nitrates at 83.85%, while phytoremediation bed 3 effectively reduced phosphate to an average of 26.26%, achieved after a 6-hour retention time. In addition, Freundlich adsorption isotherm was observable in most parameters in phytoremediation bed 1 such as ammonia as nitrogen, TDS, COD, and DO. Phytoremediation bed 3 exhibited the same adsorption isotherm on ammonia as nitrogen. Conclusively, the phytoremediation system met the Department of Environment and Natural Resources - Updated Water Quality Guidelines and General Effluent Standard (GES) for all parameters tested.

Impact of Biosorption Process on Industrial Waste Water Treatment in Panipat District, Haryana

Abstract: In this research paper, I have thoroughy described about the topic “Impact of Biosorption Process on Industrial Waste Water Treatment in Panipat District, Haryana.” The industrial wastewater pollution plaguing Panipat District, Haryana, poses a complex environmental challenge due to the diverse range of industrial activities in the region, including textiles, petrochemicals, and leather processing. This pollution, characterized by the discharge of heavy metals, dyes, organic compounds, and other contaminants into water bodies, threatens both aquatic ecosystems and public health. Conventional physical and chemical treatments have proven inadequate or environmentally harmful, necessitating the exploration of ecofriendly alternatives. Biosorption, a biotechnological method employing live or dead biomass to remove pollutants from wastewater, emerges as a promising solution owing to its cost-effectiveness, efficiency, and low environmental impact. This study explores the efficacy of biosorption techniques in mitigating industrial wastewater pollution in Panipat District, evaluating various biosorbents' performance and efficiency in pollutant removal. Results indicate remarkable reductions in pollutant concentrations, with activated carbon achieving a removal efficiency of 96% for chromium, agricultural residues demonstrating a removal efficiency of 95% for dyes, and microbial biomass exhibiting an 87.5% removal efficiency for organic compounds. Furthermore, biosorption processes contribute to cost savings, regulatory compliance, water quality enhancement, resource recovery, positive public perception, and long-term sustainability, positioning them as integral components of environmentally responsible industrial practices in Panipat. This research bridges scientific inquiry with practical application, advocating for the widespread adoption of biosorption technologies to address industrial wastewater challenges, protect ecosystems, and safeguard communities in Panipat District and beyond.

Research Progress in Reducing Pollution and Sequestration of Carbon by Carbon Neutral Plants

Under the dual constraints of economic development and ecological carrying capacity, it is necessary to explore more technical means to achieve carbon neutrality and peak in China. Plants are important carriers of terrestrial and marine carbon sink systems, whereas phytoremediation is also a scientific method to remedy environmental pollution. However, the current studies mostly focus on the single aspect of plant carbon sequestration (including both the reduction of pollutant concentrations in environmental media and degradation of pollutants) or plant pollution reduction, without considering the dual benefits of plant pollution reduction and carbon sequestration. In order to explore the carbon neutral effect of plants, we focused on the pollution reduction and carbon sequestration effect of carbon neutral plants and its progress and evaluated the pollution reduction and carbon sequestration potential of carbon neutral plants and other organisms (such as animals and soil microorganisms) and environmental functional materials. The mechanisms underlying the synergistic coupling of carbon neutral plants and animals, microorganisms, and environmental functional materials and ecosystems in reducing pollution and carbon sequestration were also explored. Finally, we proposed constructive prospects for future research on the effects of carbon neutral plants on pollution reduction and carbon sink.

An advection-diffusion equation-based approach to discern the meteorological factor effects on particle concentrations

The evaluation of the impact of meteorological conditions and anthropogenic emissions to PM2.5 concentrations is a subject of ongoing debetate, which holds significant importance in guiding the formulation and implementation of emission reduction policies. A new method, based on advection dispersion theory, has been developed to assess the impact of emission control measures and meteorological effects on the reduction of pollutant concentrations. This method involves classifying meteorological factors and utilizing the emission source intensity, which is characterized under various meteorological factors, to quantify the effects of meteorological factors and emission reduction on pollutant concentrations. Wind speed (WS), wind direction (WD), atmospheric stability (determined by cloud volume, solar radiation levels, surface wind speed) and mixed height are chosen as the key meteorological factors. Baoding City, situated within the Beijing-Tianjin-Hebei (BTH) region, is taken as an example in this study and is characterized by severe particle pollution. Due to the implementation of air pollution control measures from 2016 to 2020, the particulate pollution in this city has significantly reduced. The result of our method showed that despite the unfavorable conditions for pollutant dispersion during 2018 and 2021, the aggressive policies were estimated to have contributed to reductions in PM2.5 concentration. Specifically, there were reductions of 35.7, 19.6, 28.6, and 107.9 μg/m3 in spring, summer, autumn, and winter, respectively, from 2015 to 2018. Additionally, reductions of 8.2, 14.9, 30.0, and 50.7 μg/m3 were observed in the corresponding seasons from 2018 to 2021.

Enhanced activation of peroxymonosulfate for advanced oxidation processes using solid waste: A novel and easy implement high-value utilization process of slag

A simple, efficient and low energy-consuming process available to generate resultful radicals from PMS for organic pollutants removal had been employed in this study. Slag had been used as the activator for organic pollutants degradation under slag/PMS advanced oxidation process. In this work, effects of slag with or without pretreatment on pollutant removal were studied and radical species generated by slag were measured. Calcination pretreatment is one efficient method to enhance the degradation efficiency significantly. Due to Fe3O4 and Fe2O3 became the dominant phases after calcination, it was about 8.6-flods increasing after comparing the pollutant removal efficiency for different slag/PMS system with calcination pretreatment or not. Organic pollutant neither degraded in PMS system at 25 °C nor being absorbed by slag system for 60 min. On the contrary, up to 90% pollutant concentration reduction achieved in the slag/PMS process. During this process, both •OH and SO4•- had been detected once slag and PMS interaction in wastewater. Through the free radicals quenching tests,•OH should be the key free radical in this advanced oxidation process for the organic pollutant removal under this alkaline condition. In general, organic degradation rate was determined by the slag dosage, and the maximum degradation efficiency was mainly controlled by the PMS usage. This work is expected to broaden the high-value reutilization way for industrial solid waste.

Incorporating the impact of roadside barrier effects on dispersion into AERMOD

ABSTRACT This paper focuses on the impact of solid barriers located upwind of a highway in reducing vehicle related concentrations that occur downwind of the roadway, compared to a highway without barriers. Measurements made in the United States Environmental Protection Agency’s meteorological wind tunnel show that the mitigating impact of an upwind barrier is comparable to that of a downwind barrier. Upwind barriers lead to reductions in pollution concentrations by drawing emissions in from the highway toward the barrier. The emissions are then entrained into the flow above the recirculation zone and dispersed vertically as they are advected downwind. This upwind transport of vehicle emissions leads to concentrations at the center of the roadways that are roughly 200–300% higher than those measured on roadways with downwind barriers. This difference between on-road concentrations indicates that although both types of barriers mitigate the impact of vehicle emissions downwind of a roadway, the upwind barrier may create adverse air quality impacts for the people on the road. We have formulated a semiempirical dispersion model that incorporates the physics revealed by the wind tunnel measurements. This model improves upon a model proposed by Ahangar et al. (2017) by adjusting the wind speed to get a more realistic plume dispersion just downwind of the upwind barrier and also by providing vertical profiles of concentrations in addition to ground-level concentrations. The upwind barrier model proposed in this paper and the downwind barrier model described in Francisco et al. (2022) have been incorporated into AERMOD (version 21112) as a nonregulatory option, including the new two-barrier option when modeling both barriers on the same roadway. Implications: Our paper presents an air dispersion model algorithm for modeling the effect of upwind noise barriers on dispersion of traffic-related emissions from roadways, which was incorporated into EPA’s AERMOD and then evaluated using observations from a wind tunnel experiment. The results are compared and contrasted with results from both a no-barrier case and downwind barrier cases. This manuscript expands on previously published work analyzing the effect of barrier height and source-to-barrier distance on downwind dispersion (Atmos. Pollut. Res., 13:101385, 2022, https://doi.org/10.1016/j.apr.2022.101385). The current manuscript uses the same wind tunnel setup as reported there, but focuses on a different subset of cases, namely the upwind barrier cases, when developing dispersion model algorithms to simulate the observed effects. We believe the evaluations of the vertical profiles from the wind tunnel study, development, and incorporation of the upwind barrier algorithms into AERMOD, and model evaluation of these new algorithms are significant contributions to understanding the effects of these commonly used roadside barriers

Spatio-temporal analysis of air pollution dynamics over Bangalore city during second wave of COVID-19

The country wide lockdown implemented during 27th April to 14th June 2021 in order to prevent the spread of COVID-19 during the second wave in India. Effect of the restricted lockdown resulted in improved air quality. This study focuses on analyzing the spatio-temporal distribution analysis of major air pollutant concentration over Bangalore city in India. The inverse distance weighting (IDW) method is implemented for the spatial analysis in order to quantify the distribution of the pollutant concentrations at each location in the Urban city of Bangalore. The research considers the distinct periods of pre-lockdown and lockdown during the second wave of COVID-19 pandemic in 2021 to investigate the impact of reduced human activities on air quality over the city. The study mainly utilizes the air pollution data collected from Central Pollution Control Board (CPCB) monitoring stations across Bangalore, including measurements of pollutants such as PM2.5, PM10, O3, NO2, SO2, and CO. The IDW method is implemented to create the high-resolution pollution concentration maps for both the pre-lockdown and lockdown periods. This spatial distribution provides valuable insights into the variations in the pollution levels though out the Bangalore city. The comparative analysis of the concentration maps reveals significant changes in air pollution levels between the two periods; similarly, the temporal weekly average analysis also witnessed negative anomalies during the lockdown weeks. The results indicate substantial reductions in pollutant concentrations during the second wave COVID-19 lockdown, attributed to decreased vehicular emissions, industrial activities, and construction operations. The pre-lockdown period serves as a baseline for assessing the improvements in air quality during the lockdown. The spatio-temporal modeling approach enhances our understanding of the distribution patterns of air pollutants across the Bangalore metropolitan city. The findings underscore the potential benefits of implementing sustainable strategies to maintain improved air quality even after the pandemic subsides.

Experiment on the formaldehyde removal performance of TiO2 coating agent for finishing materials

As the frequency of indoor habitation escalates and advancements in building technology optimize airtightness, the importance of maintaining high-quality indoor air has grown increasingly critical. This urgency is further amplified by the proliferation of chemical building materials, necessitating more effective strategies for air pollutant abatement. To address this need, the current study explored the utility of titanium dioxide photocatalysts, which possess chemical decomposition capabilities, as a means of improving air quality within indoor environments. To verify the effectiveness of this approach, the research focused on the removal of formaldehyde—a quintessential indoor air pollutant—by incorporating a titanium dioxide photocatalyst into a coating agent commonly employed in construction materials. Notably, ultraviolet (UV) light, essential for activating the photocatalytic process, is generally absent in indoor settings. To mitigate this limitation, a consistent source of UV radiation was provided through the use of an UV lamp. Adhering to protocols outlined by the International Organization for Standardization, we employed a photoreactor to evaluate the photocatalytic efficiency of the composite material under varying intensities of UV radiation and reactor volumes. The results unequivocally confirmed that variations in UV radiation intensity and reactor volume significantly influenced the photocatalytic effectiveness of the material, resulting in a demonstrable reduction in pollutant concentrations. These findings suggest the feasibility of utilizing titanium dioxide photocatalysts for mitigating outdoor air pollutants, where natural UV radiation is more readily available. However, for indoor applications, the absence of naturally occurring UV radiation presents a considerable challenge. Overcoming this constraint could facilitate the indoor application of photocatalytic coatings, as informed by the optimal conditions of low pollutant reactivity and robust UV radiation revealed in this study, thereby substantially enhancing indoor air quality.

Effects of Mobility Restrictions on Air Pollution in the Madrid Region during the COVID-19 Pandemic and Post-Pandemic Periods

Air quality is one of the problems cities face today. The COVID-19 pandemic provided a unique opportunity to study the influence of traffic reduction on air quality during 2020, 2021, and 2022. The aim of this paper is to analyze the impacts and relationship between mobility restrictions in six COVID-19 wave periods and air pollution and evolution in the post-pandemic period differentiating Madrid city from its metropolitan area. We tested whether the changes produced for NO2, NOx, PM2.5, PM10, and O3 in the urban traffic and suburban traffic air quality stations data in comparison to the 2019 reference period were significant. The findings of this study show that the periods with the greatest reduction in pollutant concentrations were the first and third COVID-19 waves, when mobility restrictions were most stringent: there was strict confinement for the first wave (i.e., 47% reduction in daily average NO2 concentration), while severe weather forced a reduction in traffic in the region in the third wave period (i.e., 41% reduction in daily average NOx concentration). With the return to normal activity in the last period, pollutant concentrations began to exceed pre-pandemic levels. At the urban level, the reductions were more noticeable in relation to NO2 and NOx, while at the suburban level, changes were less prominent, except for the O3. The results are particularly inspiring for designing future mobility strategies for improving air quality in urban and metropolitan areas.

High-efficiency degradation catalytic performance of a novel Angelica sinensis polysaccharide-silver nanomaterial for dyes by ultrasonic cavitation.

Currently, the polluted wastewater discharged by industry accounts for the major part of polluted bodies of water. As one of the industrial wastewaters, dye wastewater is characterized by high toxicity, wide pollution, and difficulty in decolorization degradation. In this paper, a novel composite nanomaterial catalyst of silver was prepared by using Angelica sinensis polysaccharide (ASP) as a reducing and stabilizing agent. And the optimum reaction conditions explored are VAgNO3=5mL (300mM) and vASP=7% (w/v) for 6h at 90°C. In addition, the ASP-Ag nanocatalyst was characterized by several techniques. The results demonstrated that ASP-Ag nanoparticles were successfully synthesized. Degradation rate, which provides a numerical visualization of the percentage reduction in pollutant concentration. With the wrapping of ASP, the ultrasonic catalytic degradation rates of different organic dyes including rhodamine B (RB), methylene blue (MB), and methyl orange (MO) were from 88.2%, 88.7%, and 85.2% to 96.1%, 95.2% and 93.5% at room temperature, respectively. After the experiments, when cdyes=10mg/L, the highest degradation rate can be observed under cAPS-AgNPs=10mg/L with the most powerful cavitation frequency f=59kHz. The effect of ultrasonic frequency on the acoustic pressure distribution in the reactor was investigated by using COMSOL Multiphysis@ software to propose the mechanism of ultrasonic degradation and the mechanism was confirmed by OH radical trapping experiments. It indicates that OH produced by the ultrasonic cavitation effect plays a determinant role in the degradation. And then, the intermediate products of the dye degradation process were analyzed by gas chromatography and mass spectrometry (GC-MS), and the possible degradation processes of dyes were proposed. The resulting products of degradation are SO42-, NH4+, NO3-, N2, CO2 and H2O. Finally, the recycling degradation experiments showed that catalyst maintains a high degradation rate within reusing 5 cycles. Thus, this catalyst is highly efficient and recyclable.

Lessons learnt for air pollution mitigation policies from the COVID-19 pandemic: The Italian perspective

Policies to improve air quality need to be based on effective plans for reducing anthropogenic emissions. In 2020, the outbreak of COVID-19 pandemic resulted in significant reductions of anthropogenic pollutant emissions, offering an unexpected opportunity to observe their consequences on ambient concentrations. Taking the national lockdown occurred in Italy between March and May 2020 as a case study, this work tries to infer if and what lessons may be learnt concerning the impact of emission reduction policies on air quality. Variations of NO2, O3, PM10 and PM2.5 concentrations were calculated from numerical model simulations obtained with business as usual and lockdown specific emissions. Both simulations were performed at national level with a horizontal resolution of 4 km, and at local level on the capital city Rome at 1 km resolution. Simulated concentrations showed a good agreement with in-situ observations, confirming the modelling systems capability to reproduce the effects of emission reductions on ambient concentration variations, which differ according to the individual air pollutant. We found a general reduction of pollutant concentrations except for ozone, that experienced an increase in Rome and in the other urban areas, and a decrease elsewhere. The obtained results suggest that acting on precursor emissions, even with sharp reductions like those experienced during the lockdown, may lead to significant, albeit complex, reduction patterns for secondary pollutant concentrations. Therefore, to be more effective, reduction measures should be carefully selected, involving more sectors than those related to mobility, such as residential and agriculture, and integrated on different scales.

Quantifying COVID-19's silver lining: Avoided deaths from air quality improvements in Bogotá.

In cities around the world, COVID-19 lockdowns have significantly improved outdoor air quality. Even if only temporary, these improvements could have longer-lasting effects by making chronic air pollution more salient and boosting political pressure for change. To that end, it is important to develop objective estimates of both the air quality improvements associated with lockdowns and the benefits they generate. We use panel data econometric models to estimate the effect of Bogotá’s 16-month lockdown on PM2.5 and NO2 pollution, epidemiological models to simulate the effect of reductions in these pollutants on long- and short-term mortality, and benefit transfer methods to value the avoided mortality. We find that on average, Bogotá’s lockdown cut PM2.5 pollution by 15% and NO2 pollution by 21%. However, the magnitude of these effects varied considerably over time and across the city's neighborhoods. Equivalent permanent reductions in these pollutants would reduce long-term premature deaths from air pollution by 23% each year, a benefit valued at $1 billion annually. Finally, we estimate that if they occurred ceteris paribus, the temporary reductions in pollutant concentrations in 2020–2021 due to Bogotá’s lockdown would have cut short-term deaths from air pollution by 19%, a benefit valued at $244 million.

The impact on ambient air pollution and asthma-related admissions of COVID-19 transport restrictions

Abstract Exposure to air pollution is a known risk factor for asthma exacerbations, emergency attendances and hospitalisations. In Europe, the main source of air pollution is the transport industry, and so the COVID-19 transport restrictions provided an opportunity to examine if reduction in traffic had a demonstrable impact on ambient air quality and asthma-related admissions. Routinely collected data was used to conduct a retrospective population cohort study. The Environmental Protection Agency provided daily nitrogen dioxide (NO2) and particulate matter (PM) concentrations for Dublin, and all asthma-related admissions were collected from the Hospital In-Patient Enquiry system. The two years prior to the pandemic were compared with the period of transport restrictions (from March 2020). During the period of restrictions, there was a significant reduction in the mean number of daily asthma admissions (2.8 v 4.5 admissions p < 0.001). There was also a significant decrease in mean daily concentrations in two pollutants: NO2 (16.7 v 24.0µg/m3 p < 0.001) and PM2.5 (7.8 v 8.9µg/m3 p = 0.002). Only NO2 had a statistically significant correlation with asthma admissions (r = 0.132 p < 0.001). Transport restrictions introduced to mitigate against COVID-19 led to improvements in air quality, as seen by the reductions in pollutant concentrations. Previously described associations between pollutants and asthma, would suggest that these improvements in air quality contributed to the reduction in asthma admissions. Whereas the primary source of NO2 is transport emissions, PM is made up of particles from multiple sources, which likely explains the lack of correlation between asthma admissions and PM. Public Health need to advocate for transport policies which can improve air quality, and as a result, public health. Key messages

Assessment of Health Risks Associated with Particulate Matter and Carbon Monoxide Emissions from Biomass Fuels Utilization in Western Kenya

Purpose: The use of biomass fuels poses great threats to environmental degradation and public health risk accounting for 32% of the total attributable burden of diseases due to indoor air pollution (IAP) in especially Africa. Heavy reliance on biomass fuels for household energy in Kenya makes the country more vulnerable with 90% of the rural population relying on biomass fuels for domestic purposes. The objective of this study was to assess cooking fuel types and efficiency of improved biomass stoves in fuel consumption in Western, Kenya.
 Methodology: The data were collected through continuous real-time monitoring of kitchen Particulate Matter and Carbon II Oxide concentration for a period of 24 hours using UCB-PATS and CO monitors, questionnaires and time activity budgets. The total target population was 383 households and 204 households were selected as the sample size for HH survey. The sample size was determined using sample size algorithm by Boyd et al. (2014) where a sample size is determined by the sample population size. Selection of households for indoor air monitoring was done through quasi system where there was a predefined criterion from survey data. Tables and means were used to present results.
 Findings: The study found that Hazard quotients (HQ) for both long-term and short-term PM exposure using all stoves were all above 1 implying that health risk is real. During 24-hour cooking duration, three-stone stove using crop residues produced 145.8 times higher PM2.5 compared to RfD (Reference Dose) value while Cheprocket produced 26.4 times higher than PM2.5 RfD. People using solid biomass fuels are likely to experience headaches and running nose by the end of 24-hour period as a result of CO exposure when mud rocket stove, three stone stove and Cheprocket stoves were used. However cooks who use Chepkube stoves are not likely to experience any adverse health effects from CO exposures since the HQs were less than 1 using both wood and crop residues as fuel. The study concluded that, improved biomass stoves provided an overall reduction in pollutant concentration compared to three-stone fire but the local innovation Chepkube stove that has been classified as ungraded stove had the highest pollutant reduction. There is no health risk associated with exposure to peak CO within the 1-hour duration from all biomass stoves monitored in the study area.
 Recommendation: The study recommended that user education is necessary on kitchen practices to reduce overall exposure from improved stove utilization.

Hydrologic and water quality performance of a subsurface gravel wetland treating stormwater runoff

Subsurface gravel wetlands are an emerging type of green infrastructure that can be used to manage stormwater through the capture and slow release of runoff. They are unique to other types of green infrastructure in that they have a distinct fully saturated gravel layer below an occasionally saturated soil layer that influences pollutant removal processes. While they have been widely applied to treat wastewater, our understanding of their efficiency in treating stormwater with variable pollutant inputs is limited. To fill this gap, this study monitored the flow and water quality (total suspended solids, total nitrogen, total phosphorus, and chloride) in a subsurface gravel wetland in Oshkosh, Wisconsin at the influent, effluent, and in an observation well. Results from nine storm events indicated that the wetland had a median volume reduction of 74% and a median peak flow reduction of 89%. The reduction in pollutant concentrations where highly dependent upon the influent concentration. Average reductions of total suspended solids, total nitrogen, and total phosphorus were 49%, −21% and −0.2%, respectively, indicating an increase in nutrients; however, where influent concentrations were above irreducible levels, total phosphorus was reduced by 45% (influent ≥0.25 mg/L) and total nitrogen was reduced by 38% (influent ≥2.5 mg/L). Overall, this study shows that the subsurface gravel wetland performed similar to other types of green infrastructure and could be a good management practice to mitigate the harmful effects of stormwater runoff.

Air Quality Improvement during COVID-19 Lockdown in Colombo, Sri Lanka

This study presents a time series analysis of concentrations of particulate matter less than 2.5 micrometers (PM2.5) measured in a Colombo coastline site to determine whether air quality improves in 2020 and 2021 due to COVID-19 related travel restrictions. A package of data analysis tools that includes dedicated functions for air quality data analysis called “openair” developed on R statistical software is used in this study. When time-series data from 2017 to 2021 are analyzed, a clear reduction in PM2.5 concentration is observed. When the trend of PM2.5 concentration from late 2017 to 2021 is calculated using the Theil-Sen method, it suggests a decrease of PM2.5 concentration at a rate of 10.92 mg/m3per year (CI 8.91-13.18). Colombo is a coastal city that is greatly affected by the southwest monsoon. When monthly pollution rose diagrams were analyzed, a diurnal variation of wind pattern is observed with increasing stormy weather during the southwest monsoon season from May to September, from 2017 to 2021. To exclude the fact that the reduction in pollutant concentration is due to the increase in wind speed during the monsoon season, a cluster analysis technique has been used to separate the effect of dilution of pollutants due to the gusty winds during the monsoon season from non-monsoon seasons. The cluster analysis was performed on the concentration polar plot drawn for late 2017 to 2021, and two clear clusters were identified. Cluster-1 represented data during the monsoon season from May to September, and cluster-2 represented the data during the non-monsoon season. Cluster-1 clearly showed an inverse relationship between wind speed and PM2.5 concentration suggesting the dilution effect of concentration with the increasing wind speed. Cluster-2 clearly showed a directly proportional relationship, implying that pollutants from the city are transported to the site with increasing wind speeds. When trend analysis was performed, both clusters showed a decreasing trend. Results of the study suggest that the increasingly stormy weather during monsoons over the years has reduced the PM2.5 concentration in the study site at a rate of 11.57 mg/m3 per year (CI 9.08-14.55). The reduction in human travel that caused a decrease in traffic-related air pollution over the years has reduced the PM2.5 concentration in the study site at a rate of 7.91mg/m3per year (CI 4.68-11.92).
 Keywords: COVID-19, Lockdown, Colombo, PM2.5 concentrations, Polar plot

Meteorology-normalized variations of air quality during the COVID-19 lockdown in three Chinese megacities

To avoid the spread of COVID-19, China implemented strict prevention and control measures, resulting in dramatic variations in air quality. Here, we applied a machine learning algorithm (random forest model) to eliminate meteorological effects and characterize the high-resolution variation characteristics of air quality induced by COVID-19 in Beijing, Wuhan, and Urumqi. Our RF model estimates showed that the highest decrease in deweathered PM2.5 in Wuhan (−43.6%) and Beijing (−14.0%) was at traffic stations during lockdown period (February 1- March 15, 2020), while it was at industry stations in Urumqi (−54.2%). Deweathered NO2 decreased significantly in each city (∼30%–50%), whereas accompanied by a notable increase in O3. The diurnal patterns show that the morning peaks of traffic-related NO2 and CO almost disappeared. Additionally, our results suggested that meteorological effects offset some of the reduction in pollutant concentrations. Adverse meteorological conditions played a leading role in the variation in PM2.5 concentration in Beijing, which contributed to +33.5%. The true effect of lockdown reduced the PM2.5 concentrations in Wuhan, Beijing, and Urumqi by approximately 14.6%, 17.0%, and 34.0%, respectively. In summary, lockdown is the most important driver of the decline in pollutant concentrations, but the reduction of SO2 and CO is limited and they are mainly influenced by changing trends. This study provides insights into quantifying variations in air quality due to the lockdown by considering meteorological variability, which varies greatly from city to city, and provides a reference for changes in city scale pollutant concentrations during the lockdown.

Assessment of Air Pollution Mitigation Measures on Secondary Pollutants PM10 and Ozone Using Chemical Transport Modelling over Megacity Delhi, India

Sporadic efforts have been introduced to control emissions in Delhi, but the air quality has declined further due to the rapid development of different sectors. In this study, the impact of various mitigation scenarios on air quality for PM10, ozone, and its precursors are studied using a chemical transport model, namely WRF-Chem. The Emission Database for Global Atmospheric Research emission inventory was modified and introduced into the WRF-Chem model to assess the impact of selected emission control scenarios on different sectors. The simulations were conducted with reduced emissions for these sectors over the study domain: (a) implementation of Bharat Stage—VI norms in the transport sector, (b) conversion of fuel from coal to natural gas in the energy sector, and (c) fuel shift to LPG in the residential sector. The transport sector noted a decrease of 4.9% in PM10, 44.1% in ozone, and 18.9% in NOx concentrations with emission reduction measures. In the energy sector, a marginal reduction of 3.9% in NOx concentrations was noted, and no change was observed in PM10 and ozone concentrations. In the residential sector, a decrease of 8% in PM-10, 47.7% in ozone, and 49.8% in NOx concentrations were noted. The VOC-to-NOx ratios were also studied, revealing the ozone production over the study domain was mostly VOC-limited. As the inclusion of control measures resulted in varying levels of reduction in pollutant concentrations, it was also studied in the context of improving the air quality index. The WRF-Chem model can be successfully implemented to study the effectiveness of any regulated control measures.

Impacts of COVID-19 on Air Quality through Traffic Reduction.

In 2020, the first case of COVID-19 was confirmed in Korea, and social distancing was implemented to prevent its spread. This reduced the movement of people, and changes in air quality were expected owing to reduced emissions. In the present paper, the impact of traffic volume change caused by COVID-19 on air quality in Seoul, Korea, is examined. Two regression analyses were performed using the generalized additive model (GAM), assuming a Gaussian distribution; the relationships between (1) the number of confirmed COVID-19 cases in 2020–2021 and the rate of change in the traffic volume in Seoul, and (2) the traffic volume and the rate of change in the air quality in Seoul from 2016 to 2019 were analyzed. The regression results show that traffic decreased by 0.00431% per COVID-19 case; when traffic fell by 1%, the PM10, PM2.5, CO, NO2, O3, and SO2 concentrations fell by 0.48%, 0.94%, 0.39%, 0.74%, 0.16%, and −0.01%, respectively. This mechanism accounts for air quality improvements in PM10, PM2.5, CO, NO2, and O3 in Seoul during 2020–2021. From these results, the majority of the reduction in pollutant concentrations in 2020–2021 appears to be the result of a long-term declining trend rather than COVID-19.

Modeling Air Pollution Health Risk for Environmental Management of an Internationally Important Site: The Salt Range (Kallar Kahar), Pakistan

This study aimed to assess the health effects of emissions released by cement industries and allied activities, such as mining and transportation, in the salt range area of district Chakwal, Pakistan. DISPER was used to estimate dispersion and contribution of source emission by cement industries and allied activities to surface accumulation of selected pollutants (PM2.5, PM10, NOx, and O3). To assess the long-term effects of pollutants on human health within the radius of 500 m to 3 km, Air Q+ software was used, which was designed by the World Health Organization (WHO). One-year average monitoring data of selected pollutants, coordinates, health data, and population data were used as input data for the model. Data was collected on lung cancer mortality among different age groups (25+ and 30+), infant post-neonatal mortality, mortality due to respiratory disease, and all-cause mortality due to PM2.5 and NO2. Results showed that PM2.5 with the year-long concentration of 27.3 µg/m3 contributes a 9.9% attributable proportion (AP) to lung cancer mortality in adults aged 25+, and 13.8% AP in adults age 30+. Baseline incidence is 44.25% per 100,000 population. PM10 with the year-long concentration of 57.4 µg/m3 contributes 16.96% AP to infant post-neonatal mortality and baseline incidence is 53.86% per 1000 live births in the country. NO2 with the year-long concentration of 14.33 µg/m3 contributes 1.73% AP to all-cause mortality. Results obtained by a simulated 10% reduction in pollutant concentration showed that proper mitigation measures for reduction of pollutants’ concentration should be applied to decrease the rate of mortalities and morbidities. Furthermore, the study showed that PM2.5 and PM10 are significantly impacting the human health in the nearby villages, even after mitigation measures were taken by the selected cement industries. The study provides a roadmap to policymakers and stakeholders for environmental and health risk management in the area.