Ambient bioaerosol distribution and associated health risks at a high traffic density junction at Dehradun city, India.

Traffic junctions are one of the crowded places where commuters are at high risk of developing respiratory infections, due to their greater exposure to airborne and human transmitted microbial pathogens. An airborne bioaerosol assessment study was carried out at a high traffic density junction focusing on their concentration, contribution in respirable particulate matter (PM), and factors influencing the distribution and microbial diversity. Andersen six-stage viable cascade impactor and a wide-range aerosol spectrometer were used for microbial and particulate matter measurements, respectively. Statistical analysis was conducted to evaluate the relationship between bioaerosol concentration, vehicular count, PM concentration, and meteorological parameters. The mean bacteria concentration (1962.95 ± 651.85 CFU/m3) was significantly different than fungi (1118.95 ± 428.34 CFU/m3) (p < 0.05). The temporal distribution showed maximum concentration for bacteria and fungi during monsoon and postmonsoon seasons, respectively. In terms of bioaerosol loading, a considerable fraction of fungi (3.25%) and bacteria (5.65%) contributed to the total airborne PM. Most abundant bioaerosols were Aspergillus (27.58%), Penicillium (23%), and Cladosporium (14.05%) (fungi), and Micrococcus (25.73%), Staphylococcus (17.98%), and Bacillus (13.8%) (bacteria). Traffic-induced roadside soil resuspension and microbial aerosolizations from the human body were identified as the chief sources of bioaerosol emissions. The risk of lower respiratory tract infections caused by anthroponotic (human transmitted) transfer of bacterial pathogens is very high. The results of the study can be used to trace sources of microbial mediated communicable diseases, and to recommend appropriate safety measures to avoid pathogenic bioaerosol exposure.

Assessment of Black Carbon, optical properties and aerosol radiative forcing at Pranmati basin Himalayan critical zone observatory.

The study aimed to understand the optical properties of Black Carbon (BC) and radiative forcing over a data deficient Himalayan region focusing on critical zone observatory employing ground-based measurements by Aethalometer for BC and satellite retrieval techniques for optical properties during mid-May-June 2022 and January-May 2023. BC mass concentration ranged from 0.18 to 4.43 µgm-3, exhibit a mean of 1.47 ± 0.83 µgm-3 with higher summer concentration (1.51 ± 0.94 µgm-3) than winter (1.39 ± 0.61 µgm-3). The average Absorption Ångström Exponent observed to be significantly higher than unity (1.77 ± 0.31) over the studied high-altitude Himalayan region, suggesting the dominance of biomass-burning aerosol. Higher aethalometer derived compensation parameter (K) in winter suggesting locally originated BC while, lower K value in summer suggesting aged BC transported from Indo-Gangetic Plains. Optical properties calculated from "Optical Properties of Aerosol and Cloud" (OPAC) model are used in the "Santa Barbara DISORT Atmospheric Radiative Transfer" (SBDART) model to calculate the aerosol Direct Radiative Force (DRF). The entire studied period is characterized by the predominance of absorbing aerosols, particularly BC, increasing Aerosol Optical Depth, Asymmetric Parameters and decreasing Single Scattering Albedo, leading to a considerable increase in atmospheric radiative forcing (+0.9 Wm-2, top of atmosphere) and Heating Rate (0.36 KDay-1). The mean radiative forcing within atmosphere during summer was higher (+14.29 Wm-2) relative to the winter (+12.00 Wm-2), emphasizing the impact of absorbing aerosols on regional warming and potential glacier melting in the Himalayas at a faster rate. Urgent policy consideration for the reduction of absorbing aerosols is highlighted, recognizing the critical roles of Black Carbon in the changing behaviour of Critical Zone observatory. The study's data serve as a valuable resource to understanding and addressing uncertainties in climate models, aiding effective policy implementation for Black Carbon reduction.

Chemical composition and radiative forcing of atmospheric aerosols over the high-altitude Western Himalayas of India.

Aerosol behavior over the Himalayas plays an important role in the regional climate of South Asia. Previous studies at high-altitude observatories have provided evidence of the impact of long-range transport of pollutants from the Indo-Gangetic Plain (IGP). However, little information exists for the valley areas in the high Himalayas where significant local anthropogenic emissions can act as additional sources of short-living climate forcers and pollutants. The valley areas host most economic activities based on agriculture, forestry, and pilgrimage during every summer season. We report here first measurements at a valley site at ~2600 m a.s.l. on the trek to the Gangotri glacier (Gaumukh), in the Western Himalayas, where local infrastructures for atmospheric measurements are absent. The study comprised short-term measurement of aerosols, chemical characterization, and estimation of aerosol radiative forcing (ARF) during the winter and summer periods (2015-2016). The particulate matter mass concentrations were observed to be higher than the permissible limit during the summer campaigns. We obtained clear evidence of the impact of local anthropogenic sources: particulate nitrate is associated with coarse aerosol particles, the black carbon (BC) mass fraction appears undiluted with respect to measurements performed in the lower Himalayas, and in winter, both BC and sulfate concentrations in the valley site are well above the background levels reported from literature studies for mountain peaks. Finally, high concentrations of trace metals such as copper point to anthropogenic activities, including combustion and agriculture. While most studies in the Himalayas have addressed pollution in the high Himalayas in terms of transport from IGP, our study provides clear evidence that local sources cannot be overlooked over the high-altitude Himalayas. The estimated direct clear-sky ARF was estimated to be in the range of -0.1 to +1.6 W m-2, with significant heating in the atmosphere over the high-altitude Himalayan study site. These results indicate the need to establish systematic aerosol monitoring activities in the high Himalayan valleys.

Exposure to Atmospheric Particulates and Associated Respirable Deposition Dose to Street Vendors at the Residential and Commercial Sites in Dehradun City.

BACKGROUND: Street vendors spend relatively more time near roadways and are vulnerable to air pollution related health disorders. However, there is limited information on the quality of the air they breathe. The objectives of this present study were to calculate the mass concentration of atmospheric particulate matter (PM) in eight size fractions (PM0.4-0.7, PM0.7-1.1, PM1.1-2.1, PM2.1-3.3, PM3.3-4.7, PM4.7-5.8, PM5.8-9.0, and PM9.0--0µm) at commercial (CML) and residential site (RSL) in Dehradun city from November 2015 to May 2016. To estimate the corresponding respiratory deposition dose (RDDs) in alveolar (AL), tracheobronchial (TB), and head airway (HD) region on street vendors working at CML and RSL. To find the association of atmospheric PM with RDDs and the incidence of respiratory related disorders among street vendors. METHODS: Andersen cascade impactor was employed for calculating the PM mass concentration. Questionnaire based health survey among street vendors were carried out through personal interview. RESULTS: A significant difference (p < 0.05; t-test) between the mean PM0.4-10µm mass concentration at CML and RSL was observed with (mean ± SD) 84.05 ± 14.5 and 77.23 ± 11.7 µg m-3, respectively. RDDs in AL, TB and HD region at CML was observed to be 9.9, 7.8, and 7.3% higher than at RSL, respectively. Health survey revealed 1.62, 0.96, 0.04, and 0.57 times higher incidence of cold, cough, breathlessness, and chest pain, respectively with street vendors at CML compared to RSL. CONCLUSION: The site characteristics plays a major role in the respiratory health status of street vendors at Dehradun.

Spatial and temporal variation of BTEX in the urban atmosphere of Delhi, India.

Benzene, toluene, ethylbenzene and xylene (BTEX) form an important group of aromatic Volatile Organic Compounds (VOCs) because of their role in the tropospheric chemistry and the risk posed by them to human health. Concentrations of BTEX were determined at different sampling points in the ambient air of Delhi in order to investigate their temporal and spatial distributions. Significant positive correlation coefficient (p<0.01) was found between inter-species concentrations at all the sampling locations. Inter-species ratio and Pearson's correlations indicate that gasoline vehicular exhaust could be the major source of BTEX in Delhi. The inter-species ratios exhibit clear seasonal variations indicating differential reactivity of the VOC species in different seasons. Xylenes were found the largest contributor to the ozone formation followed by toluene.

Assessment of PAHs in soil around the International Airport in Delhi, India.

Present study was undertaken to determine the level of PAH contamination due to jet turbine exhaust in the peripheral soil of the International Airport in Delhi, India. Densely populated residential areas surrounding the airport come directly under both the landing and take-off flight paths. Twelve priority polycyclic aromatic hydrocarbons (PAHs) were analyzed in the <2 mm surface soil fraction. Identification and quantification of PAHs was done by high performance liquid chromatography (HPLC). The sum of 12 PAHs ranged from 2.39 microg g(-1) to 7.53 microg g(-1) with a mean concentration of 4.43+/-1.45 microg g(-1). PAH levels observed in the present study were found to be higher as compared to most of the literature values. Among the three sampling sites selected around the International Airport, the site near landing point revealed maximum concentration of PAHs, while minimum concentration was observed at the site near take-off point. Predominance of pyrene was observed in the airport soil. Factor analysis and isomer pair ratios suggest pyrogenic origin of PAHs in the study area.

Temporal variability of benzene concentration in the ambient air of Delhi: a comparative assessment of pre- and post-CNG periods.

CNG (compressed natural gas) was fully implemented in public transport system in Delhi in December 2002. The study assesses the benzene concentration trends at two busy traffic intersections and a background site in Delhi, India. Monitoring was done for two different time periods viz; in the year 2001-2002 (pre-CNG) and two winter months (January and February) of the year 2007 (post-CNG) to assess the impact of various policy measures adopted by the government of Delhi to improve the air quality in the city. Annual average benzene concentration for the pre-CNG period was found to be 86.47+/-53.24 microg m(-3). Average benzene concentrations for the winter months (January-February) of pre- and post-CNG periods were 116.32+/-51.65 microg m(-3) and 187.49+/-22.50 microg m(-3), respectively. Enhanced values could be solely attributed to the increase in the vehicular population from 3.5 million in the year 2001-2002 to approximately 5.1 millions in the year 2007.

Metallic species in ambient particulate matter at rural and urban location of Delhi.

In the present study 14 metallic species (six crustal and eight trace metals) were quantified in the suspended particulate matter (SPM) at a rural and urban location of Delhi, India. Particulate matter was collected on glass fiber filters for a period of one year (from September 2003 to August 2004). Rank sum test revealed that the TSP concentration at the urban site was significantly (P=0.47) higher as compared to the rural site. Urban site showed highest SPM concentration during winter while rural site during summer. Enrichment factor (EF) and coefficient of variation (CV) were calculated to assess the variability of elemental concentration data. Trace metals viz. Pb, Cd, Cu and Zn were observed to be highly enriched at both the sites, but EF for Zn and Cu was 2-3 times higher at the urban site as compared to the rural site. Trace and crustal metal concentration displayed less variability at the urban site. In the urban area, metals were mainly found to come from construction and industrial activities in surrounding. At the rural site, re-suspended and wind-blown dust appeared to be the source of observed elemental concentration.

Pattern, sources and toxic potential of PAHs in the agricultural soils of Delhi, India.

Surface soil (0-5 cm) from various agricultural sites in Delhi was analyzed to discern the contents of 16 priority polycyclic aromatic hydrocarbons (PAHs). Reference and deuterated standards were used for identification and quantification of PAHs by high performance liquid chromatography (HPLC) with UV detection. summation operator(16)PAHs ranged from 830 to 3880 microg kg(-1) (dry wt.) with an arithmetic mean of 1910+/-1020 microg kg(-1) summation operator(16)PAHs values at the urban sites were 2-5 times higher as compared to the rural sites. In general, low molecular weight PAHs were predominant. Total organic carbon (TOC) was found to be significantly correlated with summation operator(16)PAHs. Isomer pair ratios and Principal component analysis (PCA) suggested biomass and fossil fuel combustion as the main sources of PAHs. The toxic equivalency factors (TEFs) were used to estimate benzo[a]pyrene-equivalent concentration (B[a]P(eq)). Therewith, PAH content of urban agricultural soil was found to have more carcinogenic potential.

Impact of CNG implementation on PAHs concentration in the ambient air of Delhi: a comparative assessment of pre- and post-CNG scenario.

The use of alternative fuel is considered to be an effective measure to improve the urban air quality. Concerned over deteriorating air quality in Delhi, the Delhi government initiated different measures including stringent emission norms, improved fuel quality and above all introduction of cleaner fuel-CNG in public transport system. The entire city bus fleet was converted to CNG mode by 2002. The present study reports the comparative assessment of the status of air quality with respect to PM(10) and PAH before and after the introduction of CNG in public transport system in Delhi. The study has been carried out for two different time periods: first in the year 1998 and second in the year 2004. Following the total conversion of public transport system to CNG in 2002, Post-CNG data indicate a sharp reduction of 51-74% in the PM(10) concentration and 58-68% in the TPAH concentration as compared to the Pre-CNG data.

Visibility impairing aerosols in the urban atmosphere of Delhi.

To study the visual air quality of Delhi, size fractionated aerosols - coarse and fine fractions of PM10 - were collected and analysed for SO4(-2), NO(-3), NH4+ and EC at three sites with different background activities. The analysed species constitute a smaller portion of coarse fraction (39%) but a larger portion of fine fraction (69%). The sampling was performed from June 2003 to November 2003 which covers monsoon and post monsoon seasons. Aerosol data was used to describe the spatial variation of Visibility Range as a function of chemical composition of visibility impairing aerosols. During the study period, visibility was found to be poor varying between 4.7 and 13 km with an average value of 9.4 km. It is observed that visibility impairment was more due to carbonaceous aerosol followed by sulphate.

PAHs contamination in bank sediment of the Yamuna river, Delhi, India.

This study was performed to elucidate the distribution, concentration trend and possible sources of PAHs in bank sediment of river Yamuna in Delhi, India. The levels of 16 priority polycyclic aromatic hydrocarbons (PAHs) were analyzed during pre-monsoon, monsoon and post-monsoon seasons in the sediment fraction < 53 microm. Reference standards and internal standards were used for identification and quantification of PAHs by HPLC. The sum of 16 PAH compounds ranged from 4.50 to 23.53 microg/g with a mean concentration of 10.15 +/- 4.32 microg/g (dry wt.). Among 5 sites studied, the site, Income Tax Office (ITO) was found to be the hotspot attaining highest concentration. Predominance of 2-4 ring PAHs suggests a relatively recent local sources of PAHs in the study area. Moreover, molecular indices based source apportionment also illustrates pyrogenic source fingerprint of PAHs. No significant temporal trend was observed.