Aerosol Science and Engineering最新文献

Microbiological air sampling using a six-stage cascade impactor and subsequent analysis of viable mesophilic Gram- positive and Gram-negative bioaerosols at different steps of a sewage treatment plant (STP) in Delhi revealed very high spatial variations in bacteria among bio-aerosols in numbers and species. The bioaerosol concentration of Gram-positive bacteria ranged from 12 ± 07 to 997 ± 178 CFU m^− 3 at different sites of STP with peak values in post-monsoon at the aeration tank (997 ± 178 CFU m^− 3) and lowest values in winter at the final settlement tank (FST). The minimum concentration of Gram-negative bacteria was 35 ± 12 CFU m^− 3 at inlet 1 during the winter season and maximum with 749 ± 126 CFU m^− 3 at the aeration tank during the post-monsoon season. These numbers by far exceeds similar observations mentioned by various EPA’s literature both in terms of concentrations and seasonal variability in an outdoor environment. Univariate ANOVA analysis showed that sampling vs. seasons and sampler stages had the highest individual effect (p = 0.000) and no significant interactive effect (p = 0.611) of seasons and stages on Gram- positive bacterial bioaerosol concentration at inlet 1. The activated sludge treatment facility was the site where highest individual (p = 0.000) and interactive effect (p = 0.000) were found for Gram- negative bacterial bioaerosol. The significant higher regression coefficient (R²) values for Gram- positive and Gram- negative bacteria were observed to be 0.866 and 0.915 respectively in the pre-monsoon season between fine and coarse fractions of aerosols. The maximum concentrations for both types of bacteria were found in the respirable size fraction of particles which are less than 4.7 μm in aerodynamic diameter.

As a part of their occupation, the operators of heavy earth moving machineries (HEMM) working in opencast mines are exposed to several air pollutants, prominent one being the airborne particulate matter. The paper presents the findings from a study that was aimed at investigating the particulate matter exposure of heavy earth moving machineries (HEMM’s) operators in highly mechanized opencast mines. The HEMMs included in the study are dumper, shovel and drill. The mean in-cabin PM₁₀ concentrations of dumper and shovel, which had an air-conditioning system in the cabin, were in the range of 600–650 µg m⁻³. Operators inside the drill cabin that did not have air conditioning systems were exposed to as high as 1992 µg m⁻³ However, cabins were effective in preventing up to 20% particulate matter exposure by the operators in comparison to persons working in an open mine atmosphere. The main haul road in mines contributed ~ 50% higher exposure than the internal haul roads. Coarse particles (PM₁₀) are retained in upper respiratory tracts while the fines (PM_2.5 and PM₁) travel via tracheobronchial region and reach the alveolar region. Studies on occupational exposure of HEMM operators to different pollutants in a mine is at present very limited and therefore more studies need to be conducted.

The article focuses on developing a probabilistic scheme for the ingression of aerosol particles in the different regions of the human lung. The methodology adopted was based on the Monte Carlo technique, which was programmed using the Rust programming language. Around seven samples with different inspiratory capacities were examined using a similar methodology. The total regional deposition obtained through the Rust compiler was compared with corresponding solutions derived from Fortran. Relatively, the solution obtained through Fortran exhibits extreme variabilities while estimating the total regional deposition in the lungs. The results are negative skewness for all the samples. A wide range of variabilities was encountered while computing the total regional deposition fraction at different inspiratory capacities. The reliability of the Fortran compiler varied from 60.65 to 90.48% for every 10 events. The uncertainty in total regional deposition at higher inspiratory capacities was relatively high in the Rust version. There is no definite stochastic pattern at the Tracheo bronchial region observed for larger aerosol particles with the change in inspiratory capacities of some subjects. The rise in the inspiratory capacities of the subjects increases the probability of deposition of smaller aerosol particles to sediment in the Alveolar region. In some cases, the bimodal probability distribution pattern was noticed for the total regional deposition of aerosol particles. In addition, a wide range of extreme deviations was also observed in the solution derived from the Fortran version. The results obtained through the adopted methodology exhibited statistical significance in the context of the variation of aerosol size particles and their regional deposition in the human lungs.

The present study scrutinizes health risk assessment of BTEX compounds and the variation of BTEX concentration during winter and spring 2022 in indoor air of a painting workstation located in Tehran, Iran. 54 samples were collected according to NIOSH 1501 manual in 3 sub-units. The mean concentrations of BTEX were 3863, 9057, 4097, and 11,471 µg.m⁻³, respectively. Though the mean concentration of benzene surpassed, toluene, ethylbenzene, and xylene fell within the acceptable range of occupational exposure standard limit (Benzene: 1600 µg.m⁻³, Toluene: 75,516 µg.m⁻³, Ethylbenzene: 87,024 µg.m⁻³, and Xylene: 435,081 µg.m⁻³). As the results showed, the majority of carcinogenic risks (CR) for benzene and ethylbenzene were estimated to be unacceptable. The highest CR was figured out in the painting area with 8.78E−03 for benzene in the winter season and 2.10E−03 for ethylbenzene in the spring season, respectively. Additionally, the mean CR values of benzene and ethylbenzene were calculated at 2.46E−03 and 8.35E−04, respectively. All non-carcinogenic hazards (HQ) of benzene and xylene exceeded maximum standard level recommended by the US Environmental Protection Agency (EPA) in both seasons, meanwhile, HQs of toluene in winter were greater than 1. The mean HQ values for BTEX were benzene (2.94E + 01) > xylene (2.62E + 01) > toluene (4.07E−01) > ethylbenzene (9.35E−01). Our finding revealed the workers were more likely to be exposed to cancer health risks due to BTEX exposure thus, control measures should be defined to reduce the hazards raised by these chemicals at this workstation.

By using the Regional Climate Model (RegCM), this study aims to determine the influences of dust aerosols on the Indian summer monsoon and the shift of the Indian summer monsoon-related atmospheric features during the 2018 dust event. We integrate the RegCM over the Indian region at two distinct horizontal resolutions. The results obtained from the model simulations demonstrate reasonable similarities to observational and reanalysis data. We identify the diverse phases of the variation in the mean distribution of monsoon-associated characteristics in response to the dust event. Dust accumulation along the Tibetan Plateau's slopes in May creates an atmospheric column over the region, dragging the monsoonal flow towards the Foothills of the Himalayas (FoH) before the conventional arrival of the southwest monsoon. As a result, rainfall tends to increase along the FoH and decrease over central India in June. The EHP phenomenon completely dissipated in July. The atmospheric conditions further intensified during August. Apart from that, we also explore the consequences of horizontal resolution in representing the impact of dust events on rainfall in the Indian region. We have discovered that the inclusion of dust at a 25-km horizontal resolution has resulted in a decrease in rainfall in certain regions of the north-western, Indo-Gangetic Plain, and southern India. The increasing resolution shows distinct patches of reduced rainfall over the Indian region, which indicates that the dust aerosols may impact rainfall significantly over local regions.

Investigations on air pollutants and air quality were undertaken during the COVID-19 pandemic and pre-pandemic period in Alandur (13.03° N, 80.21° E), Tamil Nadu, India. This comparative study of atmospheric pollutants focuses on the variation between the COVID-19 pandemic period (lockdowns imposed to control the spread of novel coronavirus infection) and the pre-pandemic period with ground-based atmospheric pollution monitoring instruments. The observations were obtained from the Centre for Pollution Control Board (CPCB). The observations from 2018 to 2021 period are used for this investigation. First, the normalizing of the time series revealed the general trends of the atmospheric pollutants present in the specified timeline. Later, spectral estimations were done to unveil the hidden peaks and periodicities during the pre-pandemic period and the COVID-19 period. The power spectral analysis is carried out to comprehend the dispersion and variability of atmospheric pollutants by examining and comparing the power spectrum of a specific station using Blackman–Tukey window analysis, aiming to elucidate the impact of the COVID-19 pandemic on atmospheric pollution dynamics. The results indicate a particular trend at peak business hours (ISTs), with notable periodicities evident throughout each timeline. A significant decrease (~ 42.5%) in the intensities of air pollutants was observed during the COVID-19 period, with no change in O₃ concentrations being observed in the power spectral density windows at either of the two timelines. Thus, the power spectrum analysis provided access to top-to-bottom analysis of anthropogenic pollutants, quantifying the peaks and periodicities present in the pollutants for in-depth analysis and control in the future. Future studies will envisage pollution control technicalities and strategies.

The present study reports the health risk assessment in heavy metals (Cr, Cd, Pb, As, Mn, and Ni) in particulate matter (< 2.5 µm) measured at 18 different sites of five climatic zones India during the distinct seasons namely the northeast monsoon (NEM) and the southwest monsoon (SWM) in campaign mode for the period of 2014–2019. The concentration of these heavy metals in PM_2.5 was determined using WD-X-ray fluorescence (XRF). Health risk assessment of heavy metals was performed estimating Hazard quotient (HQ) and carcinogenic risk (CR) assessment for adults and children for the heavy metals. HI < 1 implies no health hazard, and HI > 1 indicates that adverse health impacts may occur. Exposure to harmful toxic metals for adults and children, the total excess cancer risk higher than the threshold range (10^–4–10^–6) of heavy metals is considered significant. Since airmass movement during the two seasons (NEM and SWM) is completely different, a variation is expected in the concentration of heavy metals and associated health risk factors. During NEM the CR for children (2–4 × 10^–6) is more observed at several sites namely Patiala, Lucknow, Varanasi, Bhuvneshwar, Jaisalmer, and Rajkot, whereas, for adults, the moderate CR (1–9 × 10^–6) is at sites Darjeeling, Jorhat, Giridh, Delhi, Udaipur, Jaisalmer, and Bikaner. CR value for children and adults is comparatively lower during SWM than NEM.

Indoor air quality (IAQ) in classrooms is a crucial factor in the growing health of children as they spend significant amounts of time in school. The present work examines indoor air quality in school classrooms, the relationship between indoor air and outdoor air, and a possible risk to children’s learning. Four IAQ parameters, particulate matter (PM_2.5 and PM₁₀), carbon dioxide (CO₂), temperature, and relative humidity, are assessed using a sensor-based device. Measurements were taken inside classrooms with windows open for non-air conditioner rooms, closed for air-conditioner rooms, and on the street outside the school boundary. Results indicate the exceedance of particulate matter concentrations beyond the thresholds set by the World Health Organization (WHO). Furthermore, the mean concentration of CO₂ is high for the air conditioner room, and relative humidity was identified as slightly higher for one school classroom. Employing the International Commission on Radiological Protection (ICRP) model, the research analyzes the respiratory deposition dose (RDD) of PM_2.5. It evaluates associated non-carcinogenic risks using the hazard quotient (HQ). Notably, the study reveals that the HQ in all classrooms surpassed the critical value of 1, indicating an elevated risk of bronchial diseases among students. Additionally, the Multiple Path Particle Dosimetry analysis suggests a higher deposition of PM in the lungs, with a predominant occurrence within the respiratory tract, particularly notable in younger children than adolescents. It concludes that urgent interventions are needed to improve school IAQ conditions, particularly in traffic-congested areas.

In this study, decentralized emission inventories were developed for the road sector in selected areas of Greater Chennai, with a specific focus on PM2.5 and PM10 emissions across four distinct periods: pre- and post-lockdowns, semi-lockdowns, and lockdowns. Land use types include residential, commercial, and industrial. It comprises 10 sampling stations: Anna Nagar, Ambattur, T.Nagar, Porur, Valasaravakkam, Koyembedu, Maduravayol, Kilpauk, Alandur, and Kodambakkam. Methodology included primary surveys to assess traffic patterns and mode preferences, monitoring vehicle volumes, and calculating emission rates in grams per second per square meter (g/s-m2). Utilizing primary surveys, the existing travel and transportation features were assessed to understand traffic patterns and mode preferences. Vehicle emission rates in grams per second per square meter (g/s-m²) for both PM2.5 and PM10 were determined for all ten stations. The study unveiled that the volume of vehicles commuting to the Koyambedu region is 2.5 to 5 times greater than in other areas. Modal shares varied, with two-wheeled vehicles constituting 33%, buses 25%, four-wheelers and three-wheelers 24%, and Vehicles for hauling goods 18%. Location with the greatest pollutant concentration proved Koyambedu at 0.000158 g/s-m², correlating with its elevated vehicular inventory. Prompted by the current air quality status, this study underscores the necessity to accurately estimate particulate matter emissions from vehicles and understand their impact on air quality.

The organic carbon (OC) and elemental carbon (EC) were characterized in different urban regions and categorized by diverse predominant sources. This study investigates seasonal and interlocation variability of OC and EC concentration and their role in light extinction coefficient (b_ext) in Indian cities. OC and EC exhibit significant spatial variability (p < 0.05) with high loading of EC at Delhi (20.80 ± 5.30 µg m^− 3) followed by Hyderabad (12.18 ± 4.96 µg m^− 3) and Pune (10.36 ± 4.77 µg m^− 3) while OC was abundant at Jabalpur (50.24 ± 4.23 µg m^− 3) followed by Udaipur (49.56 ± 6.46 µg m^− 3). The total carbonaceous aerosols (TCA) was the highest at Delhi (Mean = 87.42 ± 53.44 µg m^− 3) along with EC (Mean = 20.80 ± 5.30 µg m^− 3), followed by Hyderabad (TCA: 48.37 ± 25.50 µg m^− 3 and EC: 12.18 ± 4.96 5.30 µg m^− 3). The lowest TCA was found to be at Pune (TCA: 43.36 ± 25.60 µg m^− 3 and EC: 5.75 ± 5.46 µg m^− 3). Fractional EC percentage contribution to TC in Delhi is 10–15% higher than in other locations; in contrast, fractional OC percentage share in TC is lower by 20% relative to Jabalpur. Such an occurrence is attributable to relatively high combustion in Delhi and high secondary organic carbon (SOC) in Jabalpur. Fossil fuel combustion (FFC) was an ample source of OC and EC in Delhi compared to other locations, while SOC was the most abundant source in Jabalpur. It was found that FFC source was predominant, influencing carbonaceous species in urban regions of India. The OC and EC concentrations exhibited prominent seasonal variability, with the highest values during winter followed by post-monsoon, pre-monsoon, and lowest during monsoon. OC and EC showed a significant correlation (R²: 0.78 − 0.55) at all the locations, while primary organic carbon (POC) had an insignificant relationship with SOC (R²: 0.02–0.24). The average aerosol light extinction coefficient (b_ext) showed substantial spatial variability with the highest values at Delhi (913 ± 485 Mm^− 1) followed by Jabalpur (584 ± 308 Mm^− 1) and the lowest at Pune (451 ± 275 Mm^− 1). The analysis indicates that carbonaceous species have a dual nature: they are a more absorbing type in Delhi and a more scattering type in Pune.