Sources of submicron aerosol during fog-dominated wintertime at Kanpur

Field evidence of brown carbon absorption enhancement linked to organic nitrogen formation in Indo-Gangetic Plain

Atmospheric brown carbon (BrC), a short-lived climate forcer, absorbs solar radiation and is a substantial contributor to the warming of the Earth's atmosphere. BrC composition, its absorption properties, and their evolution are poorly represented in climate models, especially during atmospheric aqueous events such as fog and clouds. These aqueous events, especially fog, are quite prevalent during wintertime in Indo-Gangetic Plain (IGP) and involve several stages (e.g., activation, formation, and dissipation, etc.), resulting in a large variation of relative humidity (RH) in the atmosphere. The huge RH variability allowed us to examine the evolution of water-soluble brown carbon (WS-BrC) diurnally and as a function of aerosol liquid water content (ALWC) and RH in this study. We explored links between the evolution of WS-BrC mass absorption efficiency at 365 nm (MAEWS-BrC-365) and chemical characteristics, viz., low-volatility organics and water-soluble organic nitrogen (WSON) to water-soluble organic carbon (WSOC) ratio (org-N/C), in the field (at Kanpur in central IGP) for the first time worldwide. We observed that WSON formation governed enhancement in MAEWS-BrC-365 diurnally (except during the afternoon) in the IGP. During the afternoon, the WS-BrC photochemical bleaching dwarfed the absorption enhancement caused by WSON formation. Further, both MAEWS-BrC-365 and org-N/C ratio increased with a decrease in ALWC and RH in this study, signifying that evaporation of fog droplets or bulk aerosol particles accelerated the formation of nitrogen-containing organic chromophores, resulting in the enhancement of WS-BrC absorptivity. The direct radiative forcing of WS-BrC relative to that of elemental carbon (EC) was ∼19 % during wintertime in Kanpur, and ∼ 40 % of this contribution was in the UV-region. These findings highlight the importance of further examining the links between the evolution of BrC absorption behavior and chemical composition in the field and incorporating it in the BrC framework of climate models to constrain the predictions.

Trace elements in ambient aerosols and size-resolved fog droplets: Trends, enrichment, and risk assessment

Ambient particulate matter (PM) is composed of inorganic and organic components. The contribution of each component is impacted by various factors such as emission sources, atmospheric aging process, and size of the PM or droplets. This study mainly focuses on the effect of the PM and droplet size on trace elemental concentrations, for which various size fractions of ambient PM (PM₁, PM_2.5) were collected on quartz filters along with fog water (FW) samples during winter. Simultaneous, online measurements of the mass concentrations of PM₁ and PM_2.5 were also carried out. At the time of the collection, the mass concentration of PM_2.5 ranged from 19 to 890 μg/m³, and its mean value was 227 μg/m³. During the sampling period, 17 fog events occurred and caused a 27% reduction in the mean pre-fog PM_2.5 concentration. All the PM and FW samples were analyzed for 12 trace elements: Ca, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Zn, V. The concentrations of the various trace elements in the PM₁, PM_2.5, and FW samples encompassed a wide range: 10 (V)-2432 (Na) ng/m³, 34 (Mn)-13810 (Na) ng/m³, and 8 (Cr)-19870 (Ca) μg/l, respectively. The concentrations of the trace elements in the FW samples indicated a droplet-size-dependent trend: the small droplets (diameter <16 μm) had several times (3-10 times) higher concentrations than the coarser droplets (diameter >22 μm). The enrichment factor (EF) analysis revealed that the EF values for almost all the trace elements were an order of magnitude higher in the FW samples than in PM₁ and PM_2.5. Risk assessment based on toxic elements suggested a very high inhalation carcinogenic risk (231 per million) for the exposed population during foggy periods. This study will facilitate decision-making by policymakers regarding air quality and health concerns.

Determination and assessment of elemental concentration in the atmospheric particulate matter: a comprehensive review

The elemental concentrations of atmospheric particulate matter (PM) have a detrimental effect on human health in which some elemental species have carcinogenic nature. In India, significant variations have found in the practices adapted from sampling to analysis for the determination and assessment of the elemental concentration in PM. Therefore, Indian studies (2011-2020) on the related domain are summarized to impart consistency in the field and laboratory practices. Further, a comparative analysis with other countries has also been mentioned in the relevant sections to evaluate its likeness with Indian studies. To prepare this study, literature has been procured from reputed journals. Subsequently, each step from sampling to analysis has thoroughly discussed with quality assurance and control (QA/QC) compliance. In addition, a framework has been proposed that showed field and laboratory analysis in an organized manner. Consequently, this study will provide benefit to novice researcher and improve their understanding about the related subject. Also, it will assist other peoples/bodies in framing the necessary decisions to carry out this study.

Human health risk assessment in PM10 -bound trace elements, seasonal patterns, and source apportionment study in a critically polluted coking coalfield area of India

Jharia Coalfield (JCF) has been affected by coalmine fire and subsidence problems for several years. The emission of particulate pollutants is due to the history of unscientific and unregulated coal mining in the JCF area. In the present study (conducted in the year 2019), seasonal variations, possible causes, and human health hazards of particulate matter (PM₁₀ )-bound trace metals like Cd, Cu, Fe, Cr, Ni, Mn, Co, Pb, Zn, and As were estimated. The mean concentration of PM₁₀ (418 ± 67 µg/m³ ) exceeded the limit of NAAQS (National Ambient Air Quality Standards India, 2009) by a factor of 4.18. PM₁₀ -bound trace metal concentrations were found in the order of Fe > Mn > Cu > Zn > Cr > Pb > Co > Ni > Cd > As. The maximum trace metal concentrations of all the metals studied were observed at the mining areas of JCF affected by coalmine fire. Human health carcinogenic and noncarcinogenic risks in children and adults were estimated through exposure pathways, ingestion, dermal contact, and inhalation. The cancer risk was evaluated as excess cancer risk (ECR). Noncancer risk estimates were evaluated as the hazard index (HI) and the hazard quotient (HQ). The HI and HQ values for Cr, Cu, Cd, As, and Pb at coalmine-fire-affected areas were observed to be higher than the value of safe dose (≤1), showing a possible noncarcinogenic risk to the inhabitants as a result of multielemental toxicity. The ECR values (>10-6) in JCF areas suggested a carcinogenic risk to the populace of the area, owing to inhalation of PM₁₀ -linked Cd. Active mine fire (related to mining activities), higher transportation load, and resuspended particulate matter from road transportation were identified as the possible causes of the estimated risks based on principal component analysis and Pearson correlation analyses. Integr Environ Assess Manag 2022;18:469-478. © 2021 SETAC.

Emerging Major Role of Organic Aerosols in Explaining the Occurrence, Frequency, and Magnitude of Haze and Fog Episodes during Wintertime in the Indo Gangetic Plain

Aerosols are an important part of Earth's atmosphere. They can absorb, scatter, or reflect the incoming solar radiation, which results in heating or cooling of Earth, thus impacting its climate. It affects the health of exposed human population adversely, reduces visibility, disturbs environmental systems, and causes material damage. This study summarizes the research carried out to understand the role of aerosol load and its physicochemical characteristics on occurrence, frequency, and magnitude of haze and fog events during wintertime within the Indo Gangetic Plain (IGP) in the past decade. For most species, the highest concentration was measured during foggy events at night-time over the winter season. A few species such as water-soluble organic and inorganic carbon (WSOC and WSIC), K⁺, SO₄ ^2-, and NO₃ ^-, owing to their hygroscopic nature, were efficiently scavenged, resulting in their lower concentration within the interstitial aerosol during fog episodes. Oligomerization with hydroxy and carbonyl functional groups during AFP (activating fog period) and DFP (dissipating fog period), respectively, accompanied by acidic aerosol (having catalytic ability) and high aerosol liquid water content conditions was found to be significant. Whereas the fragmentation process was dominant along with functionalization of -RCOOH or carbonyl (aldehyde/ketone) and -RCOOH moieties during FP (fog period) and PoFP (post-fog period), respectively. Transition metals play an important role in aqueous production of secondary organic aerosol (SOA) especially during the night-time. Crustal sources had the highest scavenging efficiency along with WSOC playing an important role in nucleation scavenging. Fine droplets had a higher concentration of species with a larger fraction of highly oxidized organic matter (OM) as compared to coarse or medium size droplets. Also, a new approach to calculate absorption by black carbon (BC) and brown carbon (BrC) was proposed, which found the water-soluble brown carbon (WSBrC) absorption value in aerosol to be up to 1.8 times higher than that measured in their corresponding aqueous extracts. Organic aerosol plays a vital role in facilitating fog formation and is responsible for the longer residence time in the ambient atmosphere. Ammonia plays an important role in stabilizing organic aerosol and aids to this recurring haze-fog-haze cycle that is dominant during wintertime in the IGP. Therefore, controlling the major anthropogenic sources of organic aerosol and ammonia should be our top priority in this part of the world.

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.

Chemical Composition and Source Apportionment of Total Suspended Particulate in the Central Himalayan Region

The present study analyzes data from total suspended particulate (TSP) samples collected during 3 years (2005–2008) at Nainital, central Himalayas, India and analyzed for carbonaceous aerosols (organic carbon (OC) and elemental carbon (EC)) and inorganic species, focusing on the assessment of primary and secondary organic carbon contributions (POC, SOC, respectively) and on source apportionment by positive matrix factorization (PMF). An average TSP concentration of 69.6 ± 51.8 µg m−3 was found, exhibiting a pre-monsoon (March–May) maximum (92.9 ± 48.5 µg m−3) due to dust transport and forest fires and a monsoon (June–August) minimum due to atmospheric washout, while carbonaceous aerosols and inorganic species expressed a similar seasonality. The mean OC/EC ratio (8.0 ± 3.3) and the good correlations between OC, EC, and nss-K+ suggested that biomass burning (BB) was one of the major contributing factors to aerosols in Nainital. Using the EC tracer method, along with several approaches for the determination of the (OC/EC)pri ratio, the estimated SOC component accounted for ~25% (19.3–29.7%). Furthermore, TSP source apportionment via PMF allowed for a better understanding of the aerosol sources in the Central Himalayan region. The key aerosol sources over Nainital were BB (27%), secondary sulfate (20%), secondary nitrate (9%), mineral dust (34%), and long-range transported mixed marine aerosol (10%). The potential source contribution function (PSCF) and concentration weighted trajectory (CWT) analyses were also used to identify the probable regional source areas of resolved aerosol sources. The main source regions for aerosols in Nainital were the plains in northwest India and Pakistan, polluted cities like Delhi, the Thar Desert, and the Arabian Sea area. The outcomes of the present study are expected to elucidate the atmospheric chemistry, emission source origins, and transport pathways of aerosols over the central Himalayan region.

Source Analysis and Human Health Risk Assessment Based on Entropy Weight Method Modification of PM2.5 Heavy Metal in an Industrial Area in the Northeast of China

In this study, PM2.5 was analyzed for heavy metals at two sites in industrial northeast China to determine their sources and human health risks during heating and non-heating periods. A positive matrix factorization (PMF) model determined sources, and US Environmental Protection Agency (USEPA) and entropy weight methods were used to assess human health risk. PM2.5 heavy metal concentrations were higher in the heating period than in the non-heating period. In the heating period, coal combustion (59.64%) was the primary heavy metal source at Huagong Hospitals, and the contribution rates of industrial emissions and traffic emissions were 21.06% and 19.30%, respectively. Industrial emissions (42.14%) were the primary source at Xinqu Park, and the contribution rates of coal combustion and traffic emissions were 34.03% and 23.83%, respectively. During the non-heating period, coal combustion (45.29%) and industrial emissions 45.29% and 44.59%, respectively, were the primary sources at Huagong Hospital, and the traffic emissions were 10.12%. Industrial emissions (43.64%) were the primary sources at Xinqu Park, where the coal combustion and traffic emissions were 25.35% and 31.00%, respectively. In the heating period, PM2.5 heavy metals at Xinqu Park had noncarcinogenic and carcinogenic risks, and the hazard index of children (5.74) was higher than that of adult males (5.28) and females (4.49). However, adult males and females had the highest lifetime carcinogenic risk (1.38 × 10−3 and 1.17 × 10−3) than children (3.00 × 10−4). The traditional USEPA and entropy weight methods both produced reasonable results. However, when there is a difference between the two methods, the entropy weight method is recommended to assess noncarcinogenic health risks.

Chemical characterization and stable nitrogen isotope composition of nitrogenous component of ambient aerosols from Kanpur in the Indo-Gangetic Plains

Measurements of water-soluble total nitrogen (WSTN), water-soluble inorganic nitrogen (WSIN), water-soluble organic nitrogen (WSON) and ẟ¹⁵N_TN (total N) was carried out on PM_2.5 aerosol samples during wintertime to understand the major sources of ambient nitrogenous species at a heavily polluted location of Kanpur in north India. During the nighttime sampling campaign, WSON and NH₄⁺_N contributed dominantly to the WSTN. Ammonium-rich condition persisted during sampling (NH₄⁺/SO₄^2- average equivalent mass ratio = 3.1 ± 0.7), suggesting complete neutralization of SO₄^2- and formation of NH₄NO₃, which is stable in winter due to low temperature and high relative humidity (RH). Stagnant atmospheric conditions during wintertime enhanced concentrations of ionic species (SO₄^2-, NH₄⁺, and NO₃^-) at this location. Good correlations between NO₃^-_N, NH₄⁺_N and biomass burning tracer K⁺_BB (and also between NO₃^-_N, NH₄⁺_N and SO₄^2-) suggests a strong impact of biomass burning activities. Multi-linear regression (MLR) analysis shows a strong dependence of ẟ¹⁵N on NO₃^-_N, SO₄^2- and WSON in night-1 (10:00 pm to 2:00 am) and on NO₃^-_N and SO₄^2- in night-2 (2:00 am to 6:00 am) depicting different formation and removal mechanism of aerosols during both the time-periods. ẟ¹⁵N_TN in PM_2.5 varied from +8.8 to +15.5‰ (10.8 ± 1.3), similar to the variability observed for many urban locations in India and elsewhere. NH₄⁺_N and WSON control the final ẟ¹⁵N value of nitrogenous aerosols. High relative humidity during nighttime enhanced the secondary organic aerosols formation due to aqueous-phase formation and gas to particle-phase partitioning. Isotopic fractionations associated with multi-phase reactions during gas to particle conversion of NH₃ would result in an increase in ẟ¹⁵N by ~48‰ to 51‰ (at T of 5.4 °C to 15.4 °C) than that of the emission source(s), which indicates the most likely N-emission sources at Kanpur to be from agriculture activities and waste generation.

Absorption properties and forcing efficiency of light-absorbing water-soluble organic aerosols: Seasonal and spatial variability

Light-absorbing organic aerosols, also known as brown carbon (BrC), enhance the warming effect of the Earth's atmosphere. The seasonal and spatial variability of BrC absorption properties is poorly constrained and accounted for in the climate models resulting in a substantial underestimation of their radiative forcing estimates. This study reports seasonal and spatial variability of absorption properties and simple forcing efficiency of light-absorbing water-soluble organic carbon (WSOC, SFE_WSOC) by utilizing current and previous field-based measurements reported mostly from Asia along with a few observations from Europe, the USA, and the Amazon rainforest. The absorption coefficient of WSOC at 365 nm (b_abs-365) and the concentrations of carbonaceous species at Kanpur were about an order of magnitude higher during winter than in the monsoon season owing to differences in the boundary layer height, active sources and their strengths, and amount of seasonal wet precipitation. The WSOC aerosols during winter exhibited ∼1.6 times higher light absorption capacity than in the monsoon season at Kanpur site. The assessment of spatial variability of the imaginary component of the refractive index spectrum (k_λ) across South Asia has revealed that it varies from ∼1 to 2 orders of magnitude and light absorption capacity of WSOC ranges from 3 to 21 W/g. The light absorption capacity of WSOC aerosols exhibited less spatial variability across East Asia (5-13 W/g) when compared to that in the South Asia. The photochemical aging of WSOC aerosols, indicated by the enhancement in WSOC/OC ratio, was linked to degradation in their light absorption capacity, whereas the absorption Ångström exponent (AAE) remained unaffected. This study recommends the adoption of refined climate models where sampling regime specific absorption properties are calculated separately, such that these inputs can better constrain the model estimates of the global effects of BrC.

PM2.5-bound trace elements in a critically polluted industrial coal belt of India: seasonal patterns, source identification, and human health risk assessment

The concentration of trace elements like Fe, Mn, Cu, Zn, Ni, Pb, Cd, Cr, Co, and As in atmospheric particulate matter (PM2.5) was estimated to investigate their seasonal variation, potential sources, and health risk at Jharia coalfield, India, during May 2018 to April 2019. Measured PM2.5 (170 ± 45 μg/m3) exceeded the National Ambient Air Quality Standards (2009) by a factor of 4.25, the Clean Air Act, National Ambient Air Quality Standards (40 CFR part 50) by a factor of 11, and Air Quality Guidelines of World Health Organization (2005) by a factor of 16. Mean concentration of the trace elements were observed in the order of Fe > Mn > Cu > Zn > Cr > Pb > Co > Ni > Cd > As, highest being perceived at the monitoring sites affected by coal mine fire. The significantly higher HQ values posed by PM2.5-bound Cd, Cr, Cu, Pb, and As and higher HI values (multi-elemental exposure) indicated potential non-carcinogenic risk to the residents of Dhanbad. Higher ECR values in the coal mining areas of JCF indicated higher carcinogenic risk to the population (adults > children) of Dhanbad due to inhalation of PM2.5-bound Cr. Spontaneous combustion of coal in the mines, active mine fire, associated mining activities, heavy vehicular emission, and re-suspended road dust were recognized as the potential sources of the trace elements from the results of PCA and Pearson correlation analysis.

Understanding the origin of carbonaceous aerosols during periods of extensive biomass burning in northern India

Post-harvest crop residue burning is extensively practiced in North India, which results in enhanced particulate matter (PM) concentrations. This study explores the PM_2.5 (particulate matter with aerodynamic diameter ≤ 2.5 μm) emissions during various time periods (pre-monsoon, monsoon, and post-monsoon) over the biomass burning source region in Beas, Punjab. The PM_2.5 concentrations during the pre-monsoon period (106-458 μg m^-3) and the post-monsoon period (184-342 μg m^-3) were similar but much higher than concentrations during the monsoon season (23-95 μg m^-3) due to enhanced wet deposition. However, the carbonaceous aerosol fraction in PM_2.5 was nearly double in the post-monsoon season (∼27%) than the pre-monsoon period (∼15%). A higher contribution of secondary organic carbon (SOC) observed during the pre-monsoon season can be attributed to enhanced photochemical activity in dry conditions. Stable carbon isotope ratio (δ¹³C value) of ambient PM allowed elucidation of contributing sources. δ¹³C_TC correlation with SOC during post-monsoon and pre-monsoon periods suggests significant influence of secondary formation processes during both time periods. The concentrations of carbon fractions in sampled sources and aerosols suggests contribution of biofuels, resulting in enhanced PM concentration at this location. δ¹³C_TC values of pre- and post-monsoon samples show dominance of freshly emitted aerosols from local sources. Impact of biomass and biofuel combustion was also confirmed by biomass burning K⁺_BB tracer, indicating that major agriculture residue burning occurred primarily during nighttime. C₃ plant derived aerosols dominated at the sampling location during the entire sampling duration and contributed significantly during the pre-monsoon season. Whereas, both fossil fuel and C₃ plant combustion contributed to the total mass of carbonaceous aerosols during the post-monsoon and monsoon seasons.

Characterization of ambient PM1 at a suburban site of Agra: chemical composition, sources, health risk and potential cytotoxicity

The present study was conducted at a University campus of Agra to determine concentrations of crustal and trace elements in submicron mode (PM₁) particles to reveal sources and detrimental effects of PM₁-bound metals (Cr, Cd, Mn, Zn, As, Co, Pb, Cu and Ni) in samples collected in the foggy (1 December 2016-17 January 2017) and non-foggy periods (1 April 2016-30 June 2016). Samples were collected twice a week on preweighed quartz fibre filters (QM-A 47 mm) for 24 h using Envirotech APM 577 (flow rate 10 l min^-1). Mass concentration of PM₁ was 135.0 ± 28.2 and 54.0 ± 18.5 µg/m³ during foggy and non-foggy period, respectively; crustal and trace elements were 13 and 4% during foggy and 11 and 3% in the non-foggy period. Source identification by PCA (principal component analysis) suggested that biomass burning and coal combustion was the prominent sources in foggy period followed by resuspended soil dust, industrial and vehicular emission, whereas in non-foggy period resuspended soil dust was dominant followed by biomass burning and coal combustion, industrial and vehicular emissions. In both episodes, Mn has the highest Hq (hazard quotient) value and Cr has the highest IlcR (Incremental Lifetime Cancer Risk) value for both adults and children. In vitro cytotoxicity impact on macrophage (J774) cells was also tested using MTT assay which revealed decreasing cell viability with increasing particle mass.

Wintertime hygroscopic growth factors (HGFs) of accumulation mode particles and their linkage to chemical composition in a heavily polluted urban atmosphere of Kanpur at the Centre of IGP, India: Impact of ambient relative humidity

This study reported results of the wintertime simultaneous measurements of hygroscopic growth factors (HGFs) and particle-phase chemical composition of accumulation mode particles using a self-assembled Hygroscopic Tandem Differential Mobility Analyzer (H-TDMA) and an Aerodyne High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS), respectively at a heavily polluted urban atmosphere of Kanpur, situated in the center of IGP in India. HGFs at 85% relative humidity (RH) and the size-resolved composition of ambient aerosol particles (dry electrical mobility diameters of 100 and 150 nm) were investigated. HGF_85% was found to increase with particle size. The relative mass fraction of organic aerosol (OA) and NH₄NO₃ are probably the major contributors to the fluctuation of the HGF_85% for both particle sizes. The HGF_85% of accumulation mode particles were observed to increase from the minimum value observed during the morning until its maximum afternoon value. This study reported two maximum (early morning and afternoon time) and two minimum values (morning and evening time) of HGF_85%s. As a consequence, the main reasons for this incremental behavior were, increase in the ratio of inorganic to OA and oxidation level, f44 (m/z44/OA) of the OA within the particle phase. In context to the effect of ambient RH, this study reported two distinct variations of mean HGF_85% as the function of ambient RH. The positive linear relationship at low RH (LRH, RH ≤ 50%) was clearly associated with low OA loading, relatively higher substantial temperature, and wind speed. We also observed increment in f44, and effective density indicating aging of aerosol. However, HGF_85% was found to inversely decline as a function of RH at higher RH (HRH, RH > 50%) conditions, which clearly reflect the more significant contribution of primary OA and lower oxidation level of OA. Our results show the declining trend in size-resolved effective density at HRH conditions, confirming the above conclusions.

Trace element characterization of fine particulate matter and assessment of associated health risk in mining area, transportation routes and institutional area of Dhanbad, India

Samples of PM_2.5 were collected on PTFE filters at 11 monitoring stations in Dhanbad, India, from March, 2014, to February, 2015, for the quantification of 10 PM_2.5-bound trace elements by using ICP-OES, source apportionment by using principal component analysis and health risks posed by PM_2.5-bound trace elements by using health risk assessment model developed by US EPA. The average annual PM_2.5 concentration (149 ± 66 µg/m³) exceeded the national ambient air quality standards by factor of 3.7, US EPA national ambient air quality standards by factor of 10 and WHO air quality guidelines by factor of 15. The sum total of average annual concentration of all PM_2.5-bound trace elements was found to be 3.206 µg/m³ with maximum concentrations of Fe (61%), Zn (21%) and Pb (11%). Coal mining, coal combustion, vehicular emission, tyre and brake wear and re-suspension of road dust were identified as dominant sources of PM_2.5-bound trace elements from the results of correlation and chemometric analysis. The significantly high HQ values posed by PM_2.5-bound Co and Ni and intensification of HI values (15.7, 10.8 and 8.54 in mining area, transportation routes and institutional area, respectively) for multielemental exposure indicate high potential of non-carcinogenic health risk associated with inhalation exposure. The carcinogenic health risk due to multielemental exposure in mining area (2.27 × 10^-4) and transportation routes (1.57 × 10^-4) for adults were significantly higher than threshold value indicating the vulnerability of adults toward inhalation-induced carcinogenic risk posed by PM_2.5-bound trace elements.

Dependence of urban air pollutants on morning/evening peak hours and seasons

Traffic emission is a major source of air pollution in urban cities of developing world. This paper shows dependence of traffic-related air pollutants in urban cities on morning/evening peak hours and winter/summer seasons. This research also shows the meteorological impact, such as temperature (T), relative humidity (RH), and wind speed (WS), on traffic-related air pollutants in urban cites. Based on the research output, the elevated level of PM concentration was observed between 1.8 and 6.7 times at all nearby roadway locations compared with background (IIT [ISM] campus). We have found 2.3, 2.4, 2.6 (morning) and 2.0, 2.1, and 2.1 (evening) times higher average PM₁₀, PM_2.5, and PM₁ concentrations, respectively, in the winter than summer monitoring periods across all locations, due to the stable boundary layer, lower mixing height, and lower friction velocity. It is indicated that urban meteorology plays a crucial role in increasing or decreasing exposed pollutant concentrations in various microenvironments. The analysis of PM_2.5/PM₁₀ ratios was lower during whole campaign due to higher contribution of coarser particles generated by vehicles. During winter and summer seasons, 0.57 and 0.33 was observed, respectively. It is indicated that 57% and 33% of PM₁₀ makes up PM_2.5 particle, respectively. PM concentrations have showed a negative linear relationship with T and WS and positive relationship with RH in winter/summer seasons. Therefore, traffic and meteorology play a big role to increase or decrease in traffic-related air pollutants in urban air quality.

Chemical characterization and quantitativ e assessment of source-specific health risk of trace metals in PM1.0 at a road site of Delhi, India

This study presents the concentration of submicron aerosol (PM_1.0) collected during November, 2009 to March, 2010 at two road sites near the Indian Institute of Technology Delhi campus. In winter, PM_1.0 composed 83% of PM_2.5 indicating the dominance of combustion activity-generated particles. Principal component analysis (PCA) proved secondary aerosol formation as a dominant process in enhancing aerosol concentration at a receptor site along with biomass burning, vehicle exhaust, road dust, engine and tire tear wear, and secondary ammonia. The non-carcinogenic and excess cancer risk for adults and children were estimated for trace element data set available for road site and at elevated site from another parallel work. The decrease in average hazard quotient (HQ) for children and adults was estimated in following order: Mn > Cr > Ni > Pb > Zn > Cu both at road and elevated site. For children, the mean HQs were observed in safe level for Cu, Ni, Zn, and Pb; however, values exceeded safe limit for Cr and Mn at road site. The average highest hazard index values for children and adults were estimated as 22 and 10, respectively, for road site and 7 and 3 for elevated site. The road site average excess cancer risk (ECR) risk of Cr and Ni was close to tolerable limit (10^-4) for adults and it was 13-16 times higher than the safe limit (10^-6) for children. The ECR of Ni for adults and children was 102 and 14 times higher at road site compared to elevated site. Overall, the observed ECR values far exceed the acceptable level.

Chemical composition and source-apportionment of sub-micron particles during wintertime over Northern India: New insights on influence of fog-processing

A comprehensive study was carried out from central part of Indo-Gangetic Plain (IGP; at Kanpur) to understand abundance, temporal variability, processes (secondary formation and fog-processing) and source-apportionment of PM₁-bound species (PM₁: particulate matter of aerodynamic diameter ≤ 1.0 μm) during wintertime. A total of 50 PM₁ samples were collected of which 33 samples represent submicron aerosol characteristics under non-foggy condition whereas 17 samples represent characteristics under thick foggy condition. PM₁ mass concentration during non-foggy episodes varied from 24-393 (Avg.: 247) μg m^-3, whereas during foggy condition it ranged from 42-243 (Avg.: 107) μg m^-3. With respect to non-foggy condition, the foggy conditions were associated with higher contribution of PM₁-bound organic matter (OM, by 23%). However, lower fractional contribution of SO₄^2-, NO₃^- and NH₄⁺ during foggy conditions is attributable to wet-scavenging owing to their high affinity to water. Significant influence of fog-processing on organic aerosols composition is also reflected by co-enhancement in OC/EC and WSOC/OC ratio during foggy condition. A reduction by 5% in mineral dust fraction under foggy condition is associated with a parallel decrease in PM₁ mass concentration. However, mass fraction of elemental carbon (EC) looks quite similar (≈3% of PM₁) but the mass absorption efficiency (MAE) of EC is higher by 30% during foggy episodes. Thus, it is evident from this study that fog-processing leads to quite significant enhancement in OM (23%) contribution (and MAE of EC) with nearly equal and parallel decrease in SO₄^2-, NO₃^- and NH₄⁺ and mineral dust fractions (totaling to 24%). Characteristic features of mineral dust remain similar under foggy and non-foggy conditions; inferred from similar ratios of Fe/Al (≈0.3), Ca/Al (0.35) and Mg/Al (0.22). Positive matrix factorization (PMF) resolves seven sources: biomass burning (19.4%), coal combustion (1.1%), vehicular emission (3%), industrial activities (6.1%), leather tanneries (4%), secondary transformations (46.2%) and mineral dust (20.2%).

Role of ammonium ion and transition metals in the formation of secondary organic aerosol and metallo-organic complex within fog processed ambient deliquescent submicron particles collected in central part of Indo-Gangetic Plain

In this study we observed the role of ammonium ion (NH₄⁺) and transition metals (Fe, Mn, Cr, and Cu) present in ambient submicron particles in stabilizing and enhancing the yield of water soluble organic carbon (WSOC). A good correlation of WSOC with transition metals and NH₄⁺ was found (R² = 0.87 and 0.71), respectively within foggy episode collected ambient PM₁ (particles having aerodynamic diameter ≤1.0 μm) suggesting plausibleness of alternate oxidation (primarily various carbonyls into their respective organic acids, esters and other derivatives.) and aging mechanisms. Molar concentration of ammonium ion was observed to be exceeded over and above to require in neutralizing the sulphate and nitrate which further hints its role in the neutralization, stabilization and enhancement of subset of WSOC such as water soluble organic acids. Transition metals were further apportioned using enrichment factor analysis. The source of Fe, Mn, and Cr was found to be crustal and Cu was tagged to anthropogenic origin. This study also described the plausible role of significant predictors (Fe and Cu) in the secondary organic aerosol (SOA) formation through effect of Fenton chemistry. Mass-to-charge ratio of identified oxalic acid from our published recent field study (carried out from same sampling location) was used for understanding the possible metallo-organic complex with Fe supports the substantial role of Fe in SOA formation in the deliquescent submicron particles facilitated by aqueous-phase chemistry.

Chemical characterization of PM1.0 aerosol in Delhi and source apportionment using positive matrix factorization

Fine aerosol fraction (particulate matter with aerodynamic diameter <= 1.0 μm (PM)_1.0) over the Indian Institute of Technology Delhi campus was monitored day and night (10 h each) at 30 m height from November 2009 to March 2010. The samples were analyzed for 5 ions (NH₄⁺, NO₃^-, SO₄^2-, F^-, and Cl^-) and 12 trace elements (Na, K, Mg, Ca, Pb, Zn, Fe, Mn, Cu, Cd, Cr, and Ni). Importantly, secondary aerosol (sulfate and nitrate) formation was observed during dense foggy events, supporting the fog-smog-fog cycle. A total of 76 samples were used for source apportionment of PM mass. Six factors were resolved by PMF analyses and were identified as secondary aerosol, secondary chloride, biomass burning, soil dust, iron-rich source, and vehicular emission. The geographical location of the sources and/or preferred transport pathways was identified by conditional probability function (for local sources) and potential source contribution function (for regional sources) analyses. Medium- and small-scale metal processing (e.g. steel sheet rolling) industries in Haryana and National Capital Region (NCR) Delhi, coke and petroleum refining in Punjab, and thermal power plants in Pakistan, Punjab, and NCR Delhi were likely contributors to secondary sulfate, nitrate, and secondary chloride at the receptor site. The agricultural residue burning after harvesting season (Sept-Dec and Feb-Apr) in Punjab, and Haryana contributed to potassium at receptor site during November-December and March 2010. The soil dust from North and East Pakistan, and Rajasthan, North-East Punjab, and Haryana along with the local dust contributed to soil dust at the receptor site, during February and March 2010. A combination of temporal behavior and air parcel trajectory ensemble analyses indicated that the iron-rich source was most likely a local source attributed to emissions from metal processing facilities. Further, as expected, the vehicular emissions source did not show any seasonality and was local in origin.

Combined effects of organic aerosol loading and fog processing on organic aerosols oxidation, composition, and evolution

Chemical characterization of ambient non-refractory submicron aerosols (NR-PM₁) was carried out in real time at Kanpur, India. The measurements were performed during the winter (December 2014 to February 2015), and comprised of two very distinct high and low aerosol loading periods coupled with prevalent foggy conditions. The average non-refractory submicron aerosol loading varied significantly from high (HL, ~240μg/m³) to low loading (LL, ~100μg/m³) period and was dominated by organic aerosols (OA) which contributed more than half (~60%) of the measured aerosol mass. OA source apportionment via positive matrix factorization (PMF) showed drastic changes in the composition of OA from HL to LL period. Overall, O/C (oxygen to carbon) ratios also varied significantly from HL (=0.59) to LL (=0.69) period. Fog episodes (n=17) studied here seem to be reducing the magnitude of the negative impact of OA loading on O/C ratio (OA loading and O/C ratio are anti-correlated, as higher OA loading allows gas to particle partitioning of relatively less oxidized organics) by 60% via aqueous processing. This study provided new insights into the combined effects of OA loading and fog aqueous processing on the evolution of ambient organic aerosols (OA) for the first time.

Identification and quantification of indoor air pollutant sources within a residential academic campus

There is a growing concern regarding the adverse health effects due to indoor air pollution in developing countries including India. Hence, it becomes important to study the causes and sources of indoor air pollutants. This study presents the indoor concentrations of PM0.6 (particles with aerodynamic diameter less than 0.6μm) and identifies sources leading to indoor air pollution. Indoor air samples were collected at IIT Kanpur campus. Ninety-eight PM0.6 samples were collected during November 2013 to September 2014. PM0.6 concentration was measured using a single stage impactor type PM0.6 sampler. The average PM0.6 concentration indoor was about 94.44μg/m(3). Samples collected were then analysed for metal concentrations using ICP-OES (Inductively Coupled Plasma - Optical Emission Spectrometer). Eight metals Ba, Ca, Cr, Cu, Fe, Mg, Ni and Pb were quantified from PM samples using ICP-OES. Positive Matrix Factorization (PMF) was used for source apportionment of indoor air pollution. PMF is a factor analysis tool which helps in resolving the profile and contribution of the sources from an unknown mixture. Five possible sources of indoor pollutants were identified by factor analysis - (1) Coal combustion (21.8%) (2) Tobacco smoking (9.8%) (3) Wall dust (25.7%) (4) Soil particles (17.5%) (5) Wooden furniture/paper products (25.2%).

Highly time resolved chemical characterization of submicron organic aerosols at a polluted urban location

Non-refractory submicron (NR-PM₁) aerosols were measured during the late winter period (February-March) via an Aerodyne High Resolution Time of Flight Aerosols Mass Spectrometer (HR-ToF-AMS) along with Black Carbon (BC) and trace gasses in an industrial city, Kanpur, situated in the Gangetic Plain (GP) of India. The composition of NR-PM₁ aerosols was dominated by organics (54%), followed by inorganics (36%), and BC (10%). Source apportionment via Positive Matrix Factorization (PMF) of AMS measured organic aerosols (OAs) revealed 6 factors. Factors are identified as 2 types of oxidized organic aerosols (OOAs), 2 types of biomass burning organic aerosols (BBOAs), freshly emitted hydrocarbon-like organic aerosols (HOAs) and oxygenated primary organic aerosols (OPOAs). A substantial increase in relative OOA contributions (200%) and O/C ratio (26%) has been observed from the high loading events (HLE) to the low loading events (LLE). Back trajectory analysis indicated that the study location received contributions from regional and long-range transported aerosols. OA composition and evolution during this study period were also very different from those observed during a fog influenced peak winter period of December-January. This is the first study to present detailed aerosol composition during the late winter period in India highlighting the changes in OA composition and chemistry within the same winter season.

Source apportionment and risk assessment of PM1 bound trace metals collected during foggy and non-foggy episodes at a representative site in the Indo-Gangetic plain

The concentration, spatial distribution and source of 13-PM1 bound trace metals (Fe, Cu, Mn, Cr, Zn, Cd, Ni, K, Mg, Na, Ca, Pb and V) and adverse health effects of 5-PM1 bound trace metals (Mn, Zn, Ni, Cr and Cd) collected during foggy and non-foggy episodes are presented. Twenty-four samples from each period (foggy and non-foggy episodes) were collected from Kanpur, a typical densely populated city and the most polluted representative site in the Indo-Gangetic plain of India, and were analyzed for carcinogenic (Ni, Cr and Cd) and non-carcinogenic metals (Mn and Zn). The average mass concentration of PM1 during foggy and non-foggy episodes was found to be 160.16±37.70 and 132.87±27.97μg/m(3). Source identification via principle component analysis suggested that vehicular emission and anthropogenic, industrial and crustal dust were the dominant sources in this region. During both episodes the decreasing order of hazard quotient (Hq) for adult and children was as Mn>Cr>Cd>Ni>Zn. In a non-foggy episode the hazardous index (Hi) values of these 5 trace metals were found to be ~3.5 times higher than a foggy episode's exposed population, respectively. In a foggy episode, due to the exposure to total carcinogenic trace metals (Ni, Cr and Cd) present in the ambient air, 95% probability total incremental lifetime cancer risks (TIlcR) were ~687 cancer cases and ~402 cancer cases per million in the adult population and children population respectively. These cancer cases were ~1.6 times higher than a non-foggy episode's exposed population.

The diurnal variability of sulfate and nitrate aerosols during wintertime in the Indo-Gangetic Plain: implications for heterogeneous phase chemistry

Based on daytime and nighttime field-based observations we propose for the first-time the reaction mechanism for the heterogeneous formation of sulfate and nitrate aerosols.

Speciation of atmospheric polycyclic aromatic hydrocarbons (PAHs) present during fog time collected submicron particles

Airborne submicron particles (PM1) were collected using PM1 sampler during the fog-dominated days (December 2013-January 2014). PM1 values varied between 58.12 μg/m(3) and 198.75 μg/m(3), and average mass concentration was 162.33 ± 38.25 μg/m(3) while total average concentration of particle-associated polycyclic aromatic hydrocarbon (PAHs) determined was 616.31 ± 30.31 ng/m(3). This is a signal for an alarming high pollution level at this site situated in the Indo-Gangetic Plain (IGP). PAHs were extracted from filters using toluene and acetonitrile. Quantitative measurements of polycyclic aromatic hydrocarbons (PAHs) were carried out using the high performance liquid chromatography (HPLC) technique. The extracts were analyzed for 16 target polycyclic aromatic hydrocarbons (PAHs) including carcinogenic compound benzo(a)pyrene (19.86 ± 38.98 ng/m(3)). Fluoranthene, benzo(a)anthracene, anthracene, and fluorene were the predominant compounds found in the samples collected during foggy days. Based on number of rings, four-ring PAH compounds had maximum contribution (43%) in this fog time collected submicron particles followed by three-ring (21%), five-ring (20%), six-ring (13%), and two-ring (3%), respectively. In winter and foggy days, wood and coal combustion and biomass burning also significantly contribute to the PAH levels. However, diagnostic ratio suggests diesel emissions as the prime source of PAHs at this sampling site.

Personal exposure measurement of students to various microenvironments inside and outside the college campus

This study characterizes the exposure of a typical Indian Institute of Technology Kanpur student to particulate matter and gaseous co-pollutants like carbon monoxide, volatile organic compounds, and nitrogen dioxide in various microenvironments, within and outside the college campus. Chemical analysis of filter, used for the particulate matter measurement, was also carried out to determine the concentration of various elements such as Ca, Cd, Cr, Cu, Fe, Mg, Pb, Zn, and anions like F(-), Cl(-), NO3 (-), and SO4 (2-). Furthermore, time activity diary along with temperature data was maintained for the precise evaluation and analysis of results for various microenvironments. The results showed PM10 and PM2.5 concentrations to be higher at some outdoor microenvironments, particularly near the Ganga riverbank. From the chemical analysis, concentrations of chloride and fluoride were found higher in indoor microenvironments as compared to outdoors. Also, nitrate concentrations were quite higher within the laboratory premises. Concentrations of Ca, Fe, and Mg were significant outdoors, whereas Na, Ca, Fe, and K were prominent indoors. The study highlights the real-time personal exposure of a student cohort to various toxic pollutants typically found within their breathing levels and their potential sources both indoors and outdoors.