High Pollutant Concentrations Research Articles

Study on the Biotoxicity, Microbial Degradation and Metabolism, and Solidification of Monoaromatic Hydrocarbons (MACHs)

Monoaromatic hydrocarbons (MACHs), also known as aromatic organic compounds, are a general term for benzene and its derivatives. In a broad sense, monoaromatic hydrocarbons include all aromatic compounds. It can be used as an organic solvent in building decoration materials and is also widely used in other industries such as dye manufacturing, rubber manufacturing, pharmaceutical industry, pesticide industry, etc. Therefore, monoaromatic hydrocarbons are common pollutants emitted by human activities and can be widely detected in human living and living environments. With the development of China's urban economy, the improvement of residents' living standards, and the rapid increase in the number of motor vehicles, the pollution of monoaromatic hydrocarbons has become increasingly severe. Monoaromatic hydrocarbons have strong carcinogenic effects and can directly harm human respiratory, hematopoietic, nervous, reproductive and other system organs. Monoaromatic hydrocarbons also have high photochemical reactivity and are closely related to the formation of photochemical smog and aerosols in the atmosphere. Moreover, monoaromatic hydrocarbons have the characteristics of wide pollution sources, long action time, high pollution concentration, and long release cycle. They have been prioritized by the United States Environmental Protection Agency (USEPA) as pollutants for control, and have also been included in China's "blacklist" of environmental priority pollutants.

Penggunaan Jar Test untuk Penentuan Dosis dan Komposisi Optimum Komposit Koagulan Poly Aluminium Chloride (PAC) – Kitosan dalam Menurunkan TSS dan COD

Laundry waste is a pollutant that has pollutant parameters such as TSS and COD. One alternative processing is flocculation-coagulation using synthetic coagulants. The advantage of synthetic coagulants is that they are able to remove high concentrations of pollutants, but the disadvantages are that they produce quite a lot of chemical sludge and the pH of the water becomes acidic because the higher the concentration, the more coagulant is used. Previous research explains that chitosan at low doses has good penyisihan efficiency so that when combined with PAC it is hoped that it can increase penyisihan efficiency with less sludge. The purpose of this study was to determine the optimum dosage and composition for PAC and chitosan coagulant composites using the Jar Test. The Jar Test method for determining the optimum dose uses fast stirring at 140 rpm for 2 minutes and then slow stirring at 60 rpm for 15 minutes and settling for 30 minutes. Determination of the optimum dose by adding a coagulant composite of 300 ppm, 500 ppm, and 700 ppm and by varying the composition at each dose, namely 1:1, 1:3, and 3:1 between PAC-chitosan. The best conditions from the study obtained an optimum dose of 700 ppm and an optimum composition of 3:1 between PAC and chitosan resulting in COD and TSS penyisihan efficiencies of 70.04% and 90.82%.

Evolution of the waste generated along the cleaning process of phosphogypsum leachates

“The generation of acidic leachates from phosphogypsum (PGL) stacks is a global problem due to their high pollutant concentrations (As, Cr, Cd, Cu, Ni, Zn, F-, PO43-, SO42-, 210Po and 238,234U). The cleaning treatment of the PGL by neutralization with alkaline reagents is a proper option for removal of pollutants by (co)-precipitation. This study is focused on the characterization of the wastes generated along the cleaning process of PGL using CaCO3 and Ca(OH)2 with the aims of diagnosis for their valorization. In addition, a chemical modelling was performed to obtain a general guide on the precipitation behavior (cleaning) of the chemical species when the pH is increased. The main finding was that the fluorine is removed from dissolution as fluorite at pH around 3, precipitating with some gypsum. Nevertheless, calcium phosphate dominates the precipitated phase during the alkaline treatment, where monetite and brushite are the prevailing species formed at neutral pH range and fluorapatite in more basic conditions. These species contain very high concentrations of toxic chemical species and 238U-series radionuclides (mainly 238U-isotopes and 210Pb). Therefore, it is needed to design a valorization process for these two generated wastes, which could contribute to the circular economy and the improvement of the environmental conditions of the PG stacks surroundings.”

Towards healthy and energy-efficient buildings in the context of Egypt: Modelling demand-controlled ventilation to improve the indoor air quality in a generic office space in Cairo

Cairo is characterised by high concentrations of ambient air pollutants, especially air particulate matter of diameter less than 2.5 micrometre (PM2.5). Many studies have emphasized the impact of PM2.5 on people’s health and wellbeing including a World Bank report that has attributed 12% of the total annual deaths in Cairo to the exposure to ambient PM2.5. On one hand. improving the energy efficiency of buildings may involve implementing energy efficiency measures that aim to achieve indoor thermal comfort by maximizing the use of natural ventilation and minimizing mechanical air-conditioning. However, while natural ventilation can help reduce CO2 levels, it can also potentially lead to an increase in indoor PM2.5 levels. This study aims to investigate the impact of multiple air filtration scenarios on the energy consumption and the indoor air quality for a shoebox model that aims to represent generic offices Cairo. The study uses EnergyPlus simulations that leverage an Energy Management System script to model the demand-controlled ventilation, apply air filters when required, and simulate the increase in energy use due to the relevant pressure drops in the air system. The results for the scenarios investigated in the study highlighted that air filters can reduce the average indoor PM2.5 levels by nearly 40% during occupancy hours while causing an estimated increase of around 2-7% in the total operational energy. Given data and assumptions relevant to the study context, it was found that filtering the recirculated air while minimizing the introduction outdoor fresh air can be sufficient to minimize indoor PM2.5 levels.

Spatial and temporal evolution of air pollution and verification of the environmental Kuznets curve in the Yangtze River Basin during 1980—2019

ABSTRACT Continuously high concentrations of haze pollution can hinder urban economic development. In order to improve the quality of the environment in the Yangtze River Economic Belt, it is necessary to investigate the spatio-temporal characteristics and impact factors of smog. This study, relying on multi-source remote sensing data, conducted a comprehensive study on the concentration of haze pollution based on long-term data, multiple spatial scales and pollution indicators. The results showed that the concentrations of seven air pollutants (PM2.5, SO4, SO2, BC, OC, SS and dust) in the Yangtze River Basin appeared to first increase and then decreased from 1980 to 2019. Dust pollution and sea salt pollution were concentrated in the upper reaches of the Yangtze River and the coastal areas of the Yangtze River Delta, while other pollutants were higher in the Sichuan Basin and northeast of the Yangtze River. Of the socioeconomic factors, the significance of different factors on pollutant concentration was obviously different. In addition, the environmental Kuznets curve relationship between economic gain and air pollution depended on the type of pollutant, and there were certain regional differences. This study provided a scientific basis for considering innovations in haze control in the urban agglomeration of the Yangtze River Economic Belt.

Performance of electro-Fenton process for the treatment of synthetic sulphidic spent caustic waste stream generated from petroleum refineries

Sulphidic spent caustic (SSC) is an alkaline waste stream which is generated during caustic scrubbing of liquefied petroleum gas and ethylene products. Due to presence of high concentrations of sulphides and phenols, the waste stream requires proper treatment before mixing with the low strength wastewater streams produced from other refinery operations. Electrochemical process is an emerging treatment method that can work efficiently at ambient conditions. The present study reports performance of electro-Fenton (EF) process for the treatment of synthetic SSC wastewater (sulphides = 10 g L−1, phenol = 2 g L−1 and pH = 12.9). The EF runs were carried out for 2 h duration in a reactor equipped with iron electrodes. The effects of H2O2 dose (0.26–1.3 M), current density (1–20 mA cm−2), pH (4.5–12.9) and stirring speed (100–1000 rpm) were investigated on removal of pollutants. The H2O2 was rapidly consumed in initial 30 min during which the significant fraction of the pollutants was degraded or removed. The optimum conditions for EF process were found to be as follows: pH = 4.5, H2O2 dose = 1.05 M, current density = 5 mA cm−2 and stirring speed = 500 rpm. At these conditions, the maximum sulphide and phenol removals from the wastewater were 98% and 91%, respectively. The results will be helpful to the wastewater treatment plant operators worldwide dealing with high concentrations of such pollutants.

Use of expanded shale, clay, and slate aggregates and biochar in the clear zone of road infrastructures for sustainable treatment of stormwater

A Clear Zone (CZ), the unobstructed roadside area with highly compacted soil, naturally accumulates high concentrations of pollutants from traffic activities. These pollutants are washed off by road runoff and enter waterways. In situ, treatment of polluted runoff from the CZ could not only protect water resources but also provide an opportunity to recharge groundwater. However, the soil in the CZ requires compaction, which limits the natural infiltration and treatment of road runoff. In this study, we examine whether and how amending the soil in the CZ with sand, a common bulking agent used in road design, and Expanded Shale, Clay, and Slate (ESCS) aggregates, a novel light-weight engineered bulking agent, could help treat stormwater in situ. ESCS-amended soil media infiltrated 220% more water than sand-amended soil under compaction, indicating that the addition of ESCS would make the CZ better at treating road runoff generated during high-intensity rainfall. Compared to sand-amended soil in the CZ, ESCS-amended soil provided 58% more plant-available water during prolonged drying, indicating that ESCS addition would help maintain vegetation, thereby minimizing maintenance needs. Finally, replacing sand with ESCS improved the soil capacity in the CZ to remove pollutants, including heavy metals and E. coli, indicating the performance life of ESCS-amended soil would be longer than that of sand-amended soil in the CZ. Collectively, these results indicate that the addition of ESCS as an alternative bulking agent to sand in compacted soil in the CZ could potentially treat road runoff in situ and prevent pollution originating from road infrastructure.

Development of micromodels of traffic flows, taking into account environmental factors

The article considers an actual problem of organizing a safe and sustainable urban transport system. We have examined the existing positive global experience in both infrastructural and managerial decisions. Then to assess possible solutions at the stage of infrastructure design, we have developed the simulation micromodels of transport network sections of the medium-sized city (Naberezhnye Chelny) with a rectangular building type. The models make it possible to determine the optimal parameters of the traffic flow, under which pollutant emissions from cars would not lead to high concentrations of pollutants. Also, the model allows to obtain the calculated values of the volume of emissions of pollutants and the parameters of the traffic flow (speed, time of passage of the section, etc.). On specific examples, the proposed method’s effectiveness is shown. Case studies of cities of different sizes and layouts are implementation examples and possible uses proposed by the models. This study has shown the rationality of the suggested solution at the stage of assessing infrastructure projects and choosing the best option for sustainable transport development. The proposed research method is universal and can be applied in any city.

Biochemical responses of freshwater microalgae Chlorella sorokiniana to combined exposure of Zn(Ⅱ) and estrone with simultaneous pollutants removal

With the development of livestock industry, contaminants such as divalent zinc ions (Zn (Ⅱ)) and estrone are often simultaneously detected in livestock wastewater. Nevertheless, the combined toxicity of these two pollutants on microalgae is still unclear. Moreover, microalgae have the potential for biosorption and bioaccumulation of heavy metals and organic compounds. Thus, this study investigated the joint effects of Zn (Ⅱ) and estrone on microalgae Chlorella sorokiniana, in terms of growth, photosynthetic activity and biomolecules, as well as pollutants removal by algae. Interestingly, a low Zn (Ⅱ) concentration promoted C. sorokiniana growth and photosynthetic activity, while the high concentration experienced inhibition. As the increase of estrone concentration, chlorophyll a content increased continuously to resist the environmental stress. Concurrently, the secretion of extracellular polysaccharides and proteins by algae increased with exposure to Zn (Ⅱ) and estrone, reducing toxicity of pollutants to microalgae. Reactive oxygen species and superoxide dismutase activity increased as the increase of pollutant concentration after 96 h cultivation, but high pollutant concentrations resulted in damage of cells, as proved by increased MDA content. Additionally, C. sorokiniana displayed remarkable removal efficiency for Zn (Ⅱ) and estrone, reaching up to 86.14% and 84.96% respectively. The study provides insights into the biochemical responses of microalgae to pollutants and highlights the potential of microalgae in pollutants removal.

Spatial and temporal distribution of geochemical elements and their processes in different size fractions–Miri River (NW Borneo)

The toxicity, persistence, and propensity for accumulation of metals in aquatic environments have raised significant concerns globally. Expansion of urbanization with the growth of industrial and agricultural sectors in Miri City results in a high concentration of pollutants that flow directly into the Miri River. Hence, this study provides a comprehensive analysis of the Miri River water quality, focusing on spatial and temporal variations. River water samples were collected in two different time periods and analysed for physico-chemical parameters includes major ions, nutrients, metals and isotopes. Particularly, the metals were analysed in different size fractions (particulate and colloid) of the suspended solids. Geochemical plots, pollution index, geochemical modelling and factor analysis were used for the data analysis. Interpretation of data reveals that the mean concentration of metals in river water were increased from downstream to the upstream of the river irrespective of the seasons. Major ions were mostly derived from the chemical weathering of source rocks, which was supported by the Gibbs plot. Piper plot indicates the seasonal shifting of water types from Ca–Mg to Na–Cl. Isotopic signatures reveal direct atmospheric precipitation and evaporation were the major origins of river water. Fe was the dominant metal concentration in river water irrespective of the seasons (mean concentration 1.05 mg/L). Fe and Zn were the dominant metal concentration observed in all the 3 size fractions of suspended solids. Industrial activities and seawater influx dominate in the downstream, whereas weathering and agricultural inputs are significant in the upstream of the river. Particulate and colloidal fractions are the major contributors for the metal transport in the midstream and downstream of the river. The outcome of this study offer a thorough understanding of the seasonal elemental distribution at different size fractions, geochemical behaviour and the pollution status of the Miri River. With this knowledge, sustainable management strategies can be developed for this crucial water resource to the benefit of Miri community.

Assessment of respiratory and reproductive impacts of artisanal refinery activities on male Albino Wistar rats: implications for environmental health

BackgroundArtisanal petroleum refining operations have been known to produce a significant volume of air pollutants. The highest concentration of pollutants is generated during the oven heating or crude boiling phase of the operation. The major pollutant is black carbon or soot. Although these operations are widespread, especially in developing countries, the impact of exposure to emissions from artisanal refinery on both respiratory and reproductive health remains poorly understood.ObjectiveThis study is aimed to examine the effects of controlled subacute exposure to carbon soot emissions generated during the oven heating phase of the refining process, on the respiratory and reproductive systems of male albino Wistar rats.MethodsTo simulate the exposure conditions found in artisanal refineries, we developed a replicable fabrication of an artisanal refinery combustion system fitted with an exposure chamber for in vivo studies. 6–8 weeks old adolescent albino Wistar rats were divided into four groups (A, B, C, & D), with group A acting as the general control group and was not exposed to any carbon soot particulate matter. Group B, C, and D were exposed subacutely for four hours each day for 3, 7, 14, 21, and 28 days to varying emission concentrations. Daily exposure measurements were determined using Aeroqual Series 300 Gas Monitor, and average exposure concentration of carbon soot particulate matter (PM2.5), for each exposed group were given as: (1.221 ± 0.169 mg/m3, 1.290 ± 0.214 mg/m3 1.282 ± 0.235 mg/m3). Animals from each group were euthanised on Day 3, 7, 14, 21, and Day 28, respectively. Tissue samples of the lungs and testis were collected for immunohistochemistry and oxidative stress analysis.Discussion/Conclusion: Cytoarchitecture of the lungs and testis via histology and immunohistochemistry, showed inflammatory cell infiltration, thickened alveolar walls, diminished alveolar spaces, hyperaemia, and bronchial epithelial hyperplasia in the lungs of Group B, C, and D animals that were exposed to soot. While cytoarchitecture of the testis revealed a distortion of the Leydig cells, vacuolations and mild vacuolations within the spermatid layer, loss of flagella, and some distortion of seminiferous tubule in the lumen.Notable increase in the mean expression and significant P-values determined by one-way analysis of variance (ANOVA), followed by Tukey’s post hoc test, were observed on Day 14–28 (P < 0.05) for tumour-necrosis-factor alpha (TNF-α), Day 21–28 (P < 0.001) for malondialdehyde (MDA), and Day 21 (P < 0.001) for superoxide dismutase (SOD) expression in the lungs of each of the experimental Group (B, C, D) when compared to the control Group A.Our study provides valuable insights into the health risks associated with exposure to carbon soot particulate matter, thus underscoring the urgent need for necessary control measures to curb air pollution as a result of artisanal refinery activities.

Emission and capture characteristics of Chinese cooking-related fine particles.

Cooking can emit high concentrations of particles and gaseous pollutants. Cooking has contributed to the major source of indoor air pollutants, especially for particle pollutants in residential buildings. Many studies already analyzed the emission characteristics of Chinese cooking-related UFPs and PM2.5, while less for the fine particle size distributions. Currently, the fine particle emission characteristics of Chinese cooking need to be further investigated, since the mass size distribution of Chinese cooking is dominated by fine particles. This study determined the emission characteristics of PM1 and fine particles from three Chinese cooking methods. The capture efficiencies of particles were also measured by a modified indirect approach, including the impact of particle decay. The results showed that stir-fried vegetable and pan-fried meat dishes generated more fine particles at 0.542-1.5 μm. Besides, pan-fried and deep-fried meat dishes produce a higher generation of PM1. The fine particles (0.542-10 μm) number-based and volume-based size distributions of six dishes both presented a monodisperse behavior. The cooking methods are not a sensitive factor to the volume frequency of fine particle ranging from 0.542 to 10 μm. The averaged volume median and mode diameter for six typical Chinese dishes are 2.5 μm and 3.3 μm, respectively. The Sauter and DeBroukere mean diameter is 4.7 μm and 5.6 μm, respectively. The decay of fine particles increases with the particle diameter. The impact of particle decay on capture efficiency for 2-3 μm particles is about 5%. The capture efficiencies of pan-fried and deep-fried meat dishes are lower than that of vegetable dishes. In contrast, the capture efficiency for stir-fried meat dishes is higher than that of vegetable dishes. The capture efficiency for PM1 and 0.542-5 μm particles from six typical Chinese dishes were 60-90% on the IEC recommended exhaust flowrate.

Transport of pollutants in groundwater of domestic waste landfills in karst regions and its engineering control technologies

Domestic waste produces leachate with a high concentration of pollutants in the landfill process due to biochemical degradation stages like compaction and fermentation. A large number of cases show that anti-seepage membranes widely used in refuse landfills tend to rupture under long-term tension and corrosion, causing leachate to enter the groundwater system and pollute the environment. To reveal the phenomenon of groundwater contamination in refuse landfills, typical domestic waste landfills in karst regions were examined, on the basis of a summary of hydrogeological conditions and hydrochemical characteristics, a three-dimensional groundwater flow model and solute transport model were constructed to analyze the pattern of pollutant diffusion, and its controlling factors, under the current conditions and massive rupture of anti-seepage membrane. The results show that with a minor rupture of the anti-seepage membrane, the area of the low pollution region increases first and then decreases while that of the slight pollution region continuously increases; When a massive rupture of the anti-seepage membrane appears, the ranges of heavy pollution region and total pollution regions continue to grow; Pollutant migrates along the same direction as the groundwater flow and diffuse from high concentration region to low concentration regions under the differential concentration effect. Based on the temporal-spatial distribution characteristics of groundwater pollutants, two engineering control schemes, namely, curtain grouting blocking and group well pumping, were established. A comparison of the two control schemes shows that group well pumping stably maintains water quality safety over the long term, pollutants overflow from both sides of the curtain after they have accumulated to a certain point of concentration, causing damage to the groundwater environment in the conservation area.

Effects of aeration and season on the composting of hatchery waste

AbstractHatchery waste is characterized as biomass with a high concentration of pollutants, therefore, such waste should be composted in static windrows in the initial phase of the process. The current research was carried out aiming to investigate the need for forced aeration in static piles built in cells with perforated walls during the composting of hatchery waste, in association with a bulking agent, during winter and summer. Aeration resulted in greater breakdown of volatile solids (VS), carbon (C), and lignin in the summer up to 50 days of composting. However, at 70 and 90 days, the results between aerated and non‐aerated windrows were similar. The highest N breakdown took place during winter with no aeration. The concentrations of humic acids were influenced only by the season and were higher in the compost generated during summer. Micronutrient concentrations in the compost were impacted by season and were higher in the summer. It is concluded that, in winter, forced aeration is only recommended after 50 days of composting, whereas in summer, forced aeration was beneficial throughout the composting process.

Towards Cleaner Cities: An Analysis of the Impact of Bus Fleet Decomposition on PM and NOX Emissions Reduction in Sustainable Public Transport

The problem of poor air quality in urban areas has a negative impact on the health of residents. This is especially important during periods of smog. In Poland, as in other countries, the problem of poor air quality, especially during the winter season, is associated with a high concentration of particulate pollutants in ambient air (PM10, PM2.5). Sources of particulate emissions, in addition to solid-fuel boilers, include means of transportation, especially those equipped with diesel engines. In turn, during periods of strong sunshine (spring and summer), the problem of photochemical smog, whose precursors are nitrogen oxides NOX, arises in urban areas. Their main sources of emissions are internal combustion engines. Therefore, to improve air quality in urban areas, changes are being made in the transport sector, among which is upgrading the fleet of urban transport vehicles to low- or zero-emission vehicles, which are more environmentally friendly. In addition, measures that reduce the harmfulness of the transportation sector to air quality include the introduction of clean transportation zones, as well as park-and-ride (P&amp;R) systems. The purpose of this article is to present the results in terms of PM10, PM2.5, and NOx emission reductions, implemented over a period of two years (2021–2022) in the area of the Rzeszow agglomeration, related to the modernization of the suburban bus fleet and the implementation of a P&amp;R system for passenger cars. The results of the study were compared with the value of estimated emissions from coal-fired boilers used for residential heating and hot water, which also contribute to smog. Thanks to the implementation of the project, i.e., the replacement of 52 old buses with new buses of the Euro VI emission class and the construction of new P&amp;R spaces, the total average annual reduction in emissions amounted to approximately 703.6 kg of PM10, approximately 692.7 kg of PM2.5, and a reduction of approximately 10.4 tons of NOX.

Performance of Plant-Based Coagulants in Removing Turbidity and Chemical Oxygen Demand (COD) in Industrial Wastewater: A Systematic Review and Meta-Analysis

Industrial effluent contains high concentrations of pollutants, such as heavy metals, which can cause risks to human health and the ecosystem. Chemical coagulants such as aluminum and iron salts are typically used as a coagulant in the wastewater treatment plant. The effectiveness of chemical coagulants is good in the clarification of wastewater, but excessive use is not sustainable and toxic. This study focuses on the removal of turbidity and chemical oxygen demand (COD) of various industrial effluents, including dairy wastewater, textile wastewater, paper, and paper mill industry, by comparing the removal between plant-based and chemical coagulants. The study aims to quantify the ability of plant-based coagulants to remove turbidity and COD in industrial effluents. A systematic review was used to conduct this study by using a systematic search strategy (PRISMA) in the relevant databases, which are Scopus, Web of Science, and Google Scholar. Only experimental studies that test both plant-based and chemical coagulants were chosen to proceed with metaanalysis to validate the efficiency of the plant-based coagulant to remove turbidity and COD in different industrial effluents by using Cochrane RevMan 5.4 software. Twenty-five articles were evaluated, and high heterogeneity was found among those studies. The mean difference (MD) and 95% confidence interval (CI) showed a significantly increasing percentage of turbidity and COD removal by plant-based coagulant by -1.64 % (-3.49, 0.21) and -5.39% (-8.85, -1.93) respectively for all wastewaters. The result supports the application of plant-based coagulant to sustain wastewater treatment due to its eco-friendly, non-toxic, biodegradable, and capability to sustain the pH of water after treatment.

Spatiotemporal association between air pollution and stroke mortality in South Korea

BackgroundAir pollutant concentrations in South Korea vary greatly by region and time. To assess temporal and spatial associations of stroke subtypes with long-term air pollution effects on stroke mortality, we studied ischemic stroke (IS), intracerebral hemorrhage (ICH), and subarachnoid hemorrhage (SAH). MethodsThis was an observational study conducted in South Korea from 2001–2018. Concentrations of carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2), and particulate matter ≤10 µm in diameter (PM10) were determined from 332 stations. Average air pollutant concentrations in each district were determined by distance-weighted linear interpolation. The nationwide stroke mortality rates in 249 districts were obtained from the Korean Statistical Information Service. Time intervals were divided into three consecutive 6-year periods: 2001–2006, 2007–2012, and 2013–2018. ResultsThe concentrations of air pollutants gradually decreased from 2001–2018, along with decreases in IS and ICH mortality rates. However, mortality rates associated with SAH remained constant. From 2001–2006, NO2 (adjusted odds ratio [aOR]:1.13, 95% confidence interval: 1.08–1.19), SO2 (aOR: 1.10, 1.07–1.13), and PM10 (aOR: 1.12, 1.06–1.18) concentrations were associated with IS mortality, and SO2 (aOR: 1.07, 1.02–1.13) and PM10 (aOR:1.11,1.06–1.22) concentrations were associated with SAH-associated mortality. Air pollution was no longer associated with stroke mortality from 2007 onward, as the air pollution concentration continued to decline. Throughout the entire 18-year period, ICH-associated mortality was not associated with air pollution. ConclusionsConsidering temporal and spatial trends, high concentrations of air pollutants were most likely to be associated with IS mortality. Our results strengthen the existing evidence of the deleterious effects of air pollution on IS mortality.

Relative contributions of ambient air and internal sources to multiple air pollutants in public transportation modes

Commuters are often exposed to relatively high air pollutant concentrations in public transport microenvironments (TMEs) because of their proximity to emission sources. Previous studies have mainly focused on assessing the concentrations of air pollutants in TMEs, but few studies have distinguished between the contributions of ambient air and internal sources to the exposure of commuters to air pollutants. The main objective of this study was to quantify the contributions of ambient air and internal sources to the measured particulate matter and gaseous pollutant concentrations in selected TMEs in Hong Kong, a high-rise, high-density city in Asia. A sampling campaign was conducted to measure air pollutant concentrations in TMEs in Hong Kong in July and November 2018 using portable air quality monitors. We measured the concentrations of each pollutant in different TMEs and quantified the infiltration of particulate matter into these TMEs. The double-decker bus had the lowest particulate matter concentrations (mean PM1, PM2.5, and PM10 concentrations of 5.1, 9.5, and 13 μg/m3, respectively), but higher concentrations of CO (0.9 ppm), NO (422 ppb), and NO2 (100 ppb). For all the TMEs, about half of the PM2.5 were PM1 particles. The Mass Transit Railway (MTR) subway system had a PM2.5/PM10 ratio of about 0.90, whereas the PM2.5/PM10 ratio was about 0.60–0.70 for the other TMEs. The MTR had infiltration factor estimates <0.4 for particulate matter, lower than those of the double-decker bus and minibus. The MTR had the highest contribution from internal sources (mean PM1, PM2.5, and PM10 concentrations of 4.6, 13.4, and 15.8 μg/m3, respectively). This study will help citizens to plan commuting routes to reduce their exposure to air pollution and help policy-makers to prioritize effective exposure reduction strategies.

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.

Microbial community and gene dynamics response to high concentrations of gadolinium and sulfamethoxazole in biological nitrogen removal system

The impact of high antibiotic and heavy metal pollution levels on biological nitrogen removal in wastewater treatment plants (WWTPs) remains poorly understood, posing a global concern regarding the issue spread of antibiotic resistance induced by these contaminants. Herein, we investigated the effects of gadolinium (Gd) and sulfamethoxazole (SMX), commonly found in medical wastewater, on biological nitrogen removal systems and microbial characteristics, and the fate of antibiotic resistance genes (ARGs), metal resistance genes (MRGs), and mobile genetic elements (MGEs). Our findings indicated that high SMX and Gd(III) concentrations adversely affected nitrification and denitrification, with Gd(III) exerting a strong inhibitory effect on microbial activity. Metagenomic analysis revealed that high SMX and Gd(III) concentrations could reduce microbial diversity, with Thauera and Pseudomonas emerging as dominant genera across all samples. While the relative abundance of most ARGs decreased under single Gd(III) stress, MRGs increased, and nitrification functional genes were inhibited. Conversely, combined SMX and Gd(III) pollution increased the relative abundance of intl1. Correlation analysis revealed that most genera could host ARGs and MRGs, indicating co-selection and competition between these resistance genes. However, most denitrifying functional genes exhibited a positive correlation with MRGs. Overall, our study provides novel insights into the impact of high concentrations of antibiotics and heavy metal pollution in WWTPs, and laying the groundwork for the spread and proliferation of resistance genes under combined SMX and Gd pollution.