Asian Journal of Atmospheric Environment最新文献

This study was conducted in the Central Himalayan middle hills to understand the nature of polycyclic aromatic hydrocarbons (PAHs) embedded in aerosol particles, their sources and human health risk assessments. The level of sum of 15 particle-phase PAHs was between 9 and 335 ng/m³, with an average concentration of 73±66 ng/m³. There were strong seasonal differences in total suspended particles (TSP) and particle-bound PAH concentrations with higher concentrations in winter, followed by pre-monsoon and lowest in monsoon. The main contributor to the suspended particles was 5-ring PAHs (32%), followed by 4-ring (29%), 6-ring (28%), and 3-ring PAHs (11%). Conversely, the gas-phase PAHs showed that 3-ring PAHs contributed utmost to the total particles. The molecular ratios and principal component analysis indicated that both petrogenic and pyrogenic sources, particularly fossil fuel combustion, biomass combustion, and car exhausts, were the major sources of PAHs. The overall average Benzo (a)pyrene equivalent concentration of particulate PAHs was 11.71 ng/m³, which substantially exceeded the WHO guideline (1 ng/m³), and indicated the potential health risks for local residents. The average lifetime inhalation cancer risk (ILCR) estimates associated with carcinogenic PAHs was 8.78×10⁻⁶ for adults, suggesting the possible cancer risk and 2.47×10⁻⁵ for children, signifying extreme carcinogenic effects of PAHs on children’s health. Therefore, strict measures should be taken to reduce PAHs emissions in the region.

In the wake of the SARS-CoV-2 pandemic, inactivating bioaerosols became a pivotal issue which helps to prevent the transmittance of SARS-CoV-2. Thus, the current study was conducted to investigate a potential inactivating method using both ozone (O₃) and ultraviolet C (UVC). Individual and integrated effects of O₃ and UVC were compared. A solution containing approximately 4~7.3×10⁶ CFU/mL of Salmonella typhimurium bacteria was used to produce bacteria droplets. These droplets were exposed to O₃ and UVC to determine the reduction rate of bacteria. The exposure times were set as 1 and 30 minutes. Ozone concentrations were 100 and 200 ppmv. UVC-LEDs were used as a UVC source. Peak wavelength of the UVC-LED was 275 nm and the irradiation dose was 0.77 mW/cm². In terms of O₃ and UVC-LED interaction, 194 ppmv styrene was used as a target compound to be removed. Considering the O₃ and UVC-LED interaction, the presence of O₃ could reduce the performance of the UVC-LED, and UVC-LED could also reduce significant amount of O₃. The sequence of O₃ and UVC-LED treatment was as follows: O₃ was exposed at first, then UVC-LED, and this order showed the best reduction ratio (>99.9%). Therefore, if O₃ and UVC-LED is used to disinfect Salmonella typhimurium bacteria contained in droplets, bacteria should be separately exposed to O₃ and UVC-LED in order to improve the inactivation efficiency.

PM_2.5 is a WHO-designated first-class carcinogen and coping with high-concentration situations with high human risk is becoming more important. In particular, Korea has a high concentration of PM_2.5 in winter due to its geographical characteristics, which can be largely divided into foreign inflows and domestic atmospheric stability. To determine this, wind patterns and air pressure data were analyzed representatively and episodes about high concentration phenomena were classified. In this study, high-concentration PM_2.5 episodes, where the daily average PM_2.5 concentration in Seoul exceeded 35 μg/m³ between October 2019 to March 2020, were analyzed case-by-case. The criteria for the separation of consecutive episodes were established. Then, the designated episodes were classified into four categories based on cause: atmospheric stagnation, combination of causes, penetration from abroad, and accumulation. To identify the causes of the episodes, wind direction, wind speed data, wind roses, and air quality forecast modeling data obtained from “Air Korea” were studied. Fifteen episodes were identified and analyzed and each were given a classification type. Furthermore, the phenomenon of high-concentration episodes was summarized after detailed individual analysis of the episodes. As a result of case analysis, just before there was an inflow from abroad due to strong wind speed, a characteristic of low PM_2.5 concentration of air quality as a kind of cleaning effect could be found. In addition, alarm-level PM_2.5 concentrations of 75 μg/m³ or higher were often made by external inflow. This will contribute towards identifying the main causes of high PM_2.5 concentration episodes in Korea when it is applied over a longer time period.

For two bituminous coal-fired power plants with 500 MW and pulverized coal combustion type, the concentration of PM_total, >PM₁₀, PM_2.5-10, PM_2.5, NOx, and SO₂ was measured, and their emission factors were calculated through field measurement. The measurement points started from the boiler downstream and continued to the air pollution control devices (APCDs) that are installed in series, namely, the selected catalytic reduction system (SCR), air preheater (APH), electrostatic precipitator (ESP) and wet flue gas desulfurization system (WFGD). The measurement was performed at one point for more than three times by using the Korean standard method for air pollutants. However, all measurement points, except for the stacks, were not representative of the standard test method. In addition, the PM concentration was too high to reduce the collection time due to isokinetic sampling. There is a limitation of how representative the measurement results can be. During the field measurement period, the power production rate of the two coal-fired power plants was 91.6% and 79.2% in the P-1 and P-2, respectively. Moreover, in the P-2, with a low power production rate, the concentration of PM_total, PM₁₀, PM_2.5, and NOx was found to be low, and the emission factor calculated by dividing the measured concentration value by the fuel usage was also estimated to be low. Such results are due to the coal combustion chamber and various types of APCD being operated at a lower-load condition than the design capacity. In turn, the number of pollutants generated was less, and the removal efficiency of the pollutant became high. However, it was found that the concentration of SO₂ generated and the emission factor are more significantly affected by the sulfur content of the coal than the load factor change. To this end, reducing the operation load of the coal-fired power plant improves the combustion efficiency and APCDs performance and decreases the emission factor, resulting in more reduction of the air pollutants than that based on the simple calculation.

The role of aerosols in the spread of infectious diseases cannot be overemphasized in the face of increased environmental pollution from different sources. This study aimed at determining the distribution of fungi occurring in the air around human dwellings. The fungal aerosols were randomly collected from five crowded environments (market, church, school, motor park and crowded home) in Port Harcourt, Rivers State, Nigeria and examined. The sedimentation method was used for the microbiological sampling of air and fungi were identified based on macroscopic and microscopic method. The mean fungal load of the different crowded environments were as follows; market (3.19±0.43 log₁₀ SFU cm⁻² min⁻¹), church (2.96±0.33 log₁₀ SFU cm⁻² min⁻¹), school (3.22±0.29 log₁₀ SFU cm⁻² min⁻¹), motor park (3.25±0.35 log₁₀ SFU cm⁻² min⁻¹) and home (3.04±0.46 log₁₀ SFU cm⁻² min⁻¹), with motor park having the highest and church having the lowest. A total of 16 fungal isolates belonging to twelve (12) genera were identified. They included Aspergillus spp. (31.25%) and Paecilomyces sp., Mucor sp., Fusarium sp., Aspergillus sp., Rhizopus sp., Colletotrichum sp., Cryptococcus sp., Alternaria sp., Cladosporium sp., Chrysosporium sp. and Lophophyton sp. each having a percentage occurrence of 6.25%. Although there was no significant difference (p≥0.05) in the fungal population in the different sampled locations, Motor Park was observed to have the highest percentage occurrence (34.50%) and church the least (9.35%). The percentage occurrence from all sampled sites was in the order motor park>school>market>home>church. The presence of some potential pathogenic fungi such as Aspergillus flavus pose serious public health risks.

Heatwaves are acknowledged to be the major meteorological disaster, causing a noticeable impact on humans and animals’ lives during the last few decades. The number, frequency, duration, intensity, and areal extent of the heatwaves are on the rise during recent years. The Maximum temperature data of 2013 is analyzed to assess the synoptic nature, intensity, frequency, and various significant facets of the heatwave over the south peninsular states of Andhra Pradesh and Telangana. Indian subcontinent experienced a major heatwave during 2013, which claimed 1216 human lives. Even though the highest intensity of maximum temperatures is observed in May over major areas of India, the increasing (incidence, duration, number of spells, and the sweltering temperatures) number of heatwaves are observed over many parts of the country. The northwest and southeast coastal regions are the two heat wave prone regions. The advection of heat from the northwest with the aid of north-westerly winds causes heatwaves over northwest India to sweep or move towards India’s southeast and east coast. The heatwave record over south-eastern India, i.e, Andhra Pradesh and the adjoining Telangana state during May 22–24, 2013 were described in this study. Maximum temperatures above 40°C are observed with a sudden rise by 6 to 7°C over the study region. An attempt is made to predict the maximum temperatures 72 hours before the existence of a heatwave at 3 km horizontal resolution using the Advanced core of the Weather Research and Forecasting (WRF) model. Model predicted temperature values match with observations and the statistical metrics show a high index of the agreement, lower values for root-mean-square error and mean absolute error. Atmospheric circulation patterns associated with this heatwave are also presented. The arrest of sea breeze, the hovering of diabatic heat because of subsidence is the factor that abetted the heatwave blockade over the south-eastern part of the country. The WRF model forecasts could present the occurance of the heat wave over AP and Telangana region with 72 hour lead time with high accuracy.

Black Carbon (BC) is a major pollutant that poses immediate health as well as long-term climatic threat to human civilization. Globally, India and China are considered to be among the significant contributors of carbonaceous aerosol. Therefore, in the recent past, several studies on BC measurements have been conducted and reported in both these countries. Optical absorbance measurement techniques which give BC mass by measuring light absorbance of aerosol have been used widely. Keeping these facts in mind, here an attempt has been made to realise the current state of Equivalent Black Carbon (EBC) measurement done in both countries. Eighty EBC measurement studies published in last 15 years (2005–2020) are analysed on the basis of technique, instrumentation and various important parameters involved in measurements. It is found that EBC measurements in India and China contain large uncertainties, and available data are metrologically insufficient to realise spatial distribution and long-term temporal variation precisely. Furthermore, MERRA-2 Surface Black Carbon (SBC) levels and EBC measurements are compared and evaluated for biases between spatial and temporal variation of modelled data and ground measurements. It is observed that standardization of measurement technique and parameters involved in measurement is the need of the hour. Lack of a reference method creates inconsistency and discrepancy among the measurements. Recommendations for selection of parameter/instrument and cautious measures are provided as conclusion based on this review to improve overall metrology of BC.

Real-time onsite monitoring of indoor airborne microbes in a residential property in central Tokyo was carried out in 2020 and 2021, following the onset of the COVID-19 pandemic. A microbial sensor utilizing fluorescence emitted by microorganisms was used to measure bioaerosol concentrations in the living room and children’s bedroom as well as on the balcony. Indoor PM_2.5 was also monitored simultaneously at certain time points using a PM_2.5 sensor. The behavior of the residents was also recorded during some monitoring periods. The average number concentration of microbes as fungi in the living room was 15,100, 58,800, and 10,600 counts m⁻³ in spring, summer, and winter, respectively, increasing in summer when the outside temperature was high. Microbial number concentrations were closely related to human behavior, increasing rapidly during periods of physical activity, but decreasing again within 20–30 min of the activity ending. There was no clear correlation between indoor microbial number concentrations and PM_2.5 concentrations, suggesting that indoor microorganisms are concentrated in coarse particles, such as dust, which are quickly removed via gravitational settling. The concentration of indoor airborne microorganisms decreased significantly after ventilation, and although an occasional increase was observed immediately after ventilation, concentrations decreased again rapidly within 10–20 min. These results suggest that even a short period of ventilation can significantly reduce the indoor bioaerosol.

Total Column Ozone (TCO) is a critical factor affecting the earth’s atmosphere, especially in the Himalayan region. A comprehensive study of TCO trend analysis and corresponding consequences in the Himalayan atmosphere needs to be analyzed. We statistically examine TCO variability by analyzing the daily TCO dataset of the last 15 years (2005–2019) over the crucial region of the Himalayan environment i.e. Uttara-khand, India. Obtained results indicate that TCO values are at peak during the spring season whereas it shows the least value during the winter season. The highest and lowest value of Coefficient of Relative Variance (CRV) is estimated as 3.14 and 1.09 during winter and monsoon season, respectively. Air mass trajectories have been estimated using Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT), which shows the existence of strong seasonal variability of Ozone corresponding to continental and maritime transportation towards Uttarakhand. Moreover, Least Square Method (LSM) and the Mann-Kendall test estimate a high correlation (86%) for the seasonal and annual trend of TCO with a negative rate. The obtained decreasing rate is very low which indicates recovery of TCO during the study period. Further results imply that the inter-annual oscillation pattern of TCO is similar to Quasi-Biennial Oscillation (QBO) significantly. In addition, a comparative study has been performed for the data measured by two TCO measuring instruments i.e. Ozone Monitoring Instrument (OMI) and Ozone Mapping Profiler Suite (OMPS). TCO values measured from both instruments are highly correlated (96%) with an average relative difference of around 3%. The outcomes of this study are expected to be beneficial for future study of TCO over other crucial regions of Himalayan territory.

Continuous monitoring of hourly PM_2.5 component concentrations has been performed in Japan. The objective of this study was to evaluate the advantages of continuous monitoring to obtain data that can be useful for regional air quality simulations. Inclusion of transboundary transport in the simulations improved the correlation between the observed and simulated hourly concentrations of SO₄²⁻, SO₃⁻, secondary organic aerosols (SOA), and metals in PM_2.5. Black carbon was an exception, suggesting the overestimation of emissions in upwind countries. Including volcanic and dust emissions also improved the correlations between the observed and simulated hourly concentrations of SO₄²⁻ and metals, respectively. However, despite the good correlation achieved by including transboundary transport, it also resulted in overestimated NO₃²⁻ and SOA concentrations in western Japan during the winter. Further improvements are necessary, such as balancing with SO₄²⁻ and the dry deposition of gaseous HNO₃ for NO₃⁻, and new treatment of the partitioning and aging of semivolatile organic aerosols, which have been incorporated into recent models for SOA. The differences in model performance with regard to simulating metal concentrations suggest imbalances in the speciation profiles used for countries other than Japan. Further, comparing the observed and simulated hourly concentrations helped identify the key processes driving air quality. This revealed evening peaks in black carbon concentrations, owing to the relatively stable atmosphere; and early morning peaks in NO₃⁻ concentration, owing to the low temperature and high humidity through thermodynamic equilibrium. This study demonstrated that continuous monitoring of hourly variations in PM_2.5 composition is valuable for understanding the roles of the emission sources and for improving future models, both of which contribute to deriving effective PM_2.5 suppression strategies.