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Precise and accurate determination of particle size distribution (PSD) and compositional analysis is of prime importance for road dust management as most of the dust after collection is dumped on the adjacent side of the road or landfill sites. In this manuscript, we have compiled the scattered information about the dust classification, sources, PSD, polyaromatic hydrocarbons (PAHs), traces metals, etc. and also determined the PSD of collected road dust of representative samples from selected commercial, institutional, traffic intersection and residential sites in Delhi NCR. The moisture has been conducted by using IS 2720 (Part-2) standard test method. It was observed that moisture varied from 3.38 ± 0.14% to 8.05 ± 0.33%, respectively. The uncertainty evaluation to determine PSD has been carried out. The effects of balance, recovery, sieves diameter, have also been determined as per EURACHEM/GUM guidelines. The classification of road dust as per Indian Standard Specification (IS: 1498) suggested that the major percentage of road dust falls in the sand category and has possibilities to use widely for construction purposes, preparation of blocks, kerb, development of footpaths, etc. The modifications of road design, development of green belts and growing of dust capturing plants are the other alternatives to control emission of road dust. However, there is a dire need to develop reference material for accurate measurement of road dust to control road dust emissions in a scientific perspective.

The waste receiving capacity of most municipal solid waste (MSW) landfill sites in India is exhausted, resulting in the formation of larger waste heaps. In the majority of Indian cities, these old waste heaps are prone to frequent smoldering and ignition resulting into fires. In this study, the potential risk of spontaneous ignition of landfilled waste at landfill surface was analyzed based on the physico-chemical characteristics of waste, carbon monoxide (CO) levels, landfill surface temperature (LST). The leachate pollution index was also determined to analyze the leachate quality for three different seasons (monsoon, pre-monsoon and post-monsoon). The regression analysis was carried out to understand the thermal properties (smoldering temperature, smoldering time, ignition temperature etc.) of MSW. The results showed that old waste has a higher tendency to undergo ignition compared to fresh waste. It has also been observed that the lower MC of old waste samples in the range of 3.4% and 18.2% is the most likely cause of early smoldering (106.6-109.5 °C) and ignition (198.6-208.4 °C) of old waste. In pre-monsoon season, CO concentrations for sub-surface (10-30 cm depth) smoldering events (SSE) were observed to be between ∼ 150 to 200 ppm. This CO level substantially dropped to 10 ± 1 ppm in the post-monsoon season. The estimation of the leachate pollution index (LPI) showed an index score of 27.35, 30.47 and 10.71 for pre-monsoon, monsoon and post-monsoon seasons, respectively. The determination of CO levels, increased LST and physico-chemical properties of landfilled waste will greatly assist in the abatement of environmental pollution arising from landfill fires.

The diurnal and seasonal variation of PM

This paper enlightens the emissions of particulate and gaseous pollutants in the indoor environment of restaurant kitchen in Delhi, National Capital Region (NCR). The common cooking fuels used in the restaurant kitchen are coal based tandoor and liquefied petroleum gas (LPG). This study investigated the emissions of particulate matter (PM10 and PM2.5) and gaseous pollutants (CO and CO2) at sources of tandoor and LPG in the month of July 2019. The distance between samplers and source were around 2–3 m. Particulate matter (PM) samples were collected by using Mini Vol Air Metrics sampler on Whatman 47 mm size of glass fiber filter paper for the period of 8 h and analyzed by gravimetric method. The flow rate maintained for collection of PM was 5 lpm. Gaseous pollutant like CO and CO2 were collected for the period of 8 h and analyzed by NDIR method. The average concentrations of PM10 and PM2.5 in both Tandoor and LPG were 803 ± 256 and 412 ± 147 and 461 ± 60 and 290 ± 64 µg/m3 respectively. The average concentration of CO and CO2 in both Tandoor and LPG were 5 ± 2 and 1636 ± 113 and 3 ± 1 and 1688 ± 236 in mg/m3 respectively. The temperature and relative humidity in both Tandoor and LPG varied from 33 to 38 °C and 49–70% and 32–35 °C and 72–90% respectively. Till date no standard has been formulated in India for indoor air pollutants. The average concentrations of particulate and gaseous pollutants inside the restaurant kitchen were higher for coal based tandoor as compared to LPG. The present study revealed that indoor air pollution in the restaurant kitchen was influenced by cooking fuels and meteorological parameter.

At present scenario, estimation of Greenhouse Gas (GHG) emission in the ambient air has becomes a major concern. Emission of GHG has the direct linkage with ambient air pollution and also poses global environmental threats and challenges. Though several scientists are working to mitigate the emission of GHGs but till date no mitigation/management plan has been implemented in global scale. The emission of GHGs are in general from multiple sectors like energy, industry, waste management plant, agricultural sector etc. The major GHGs are methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O). In the present study GHG (CH4, CO2 and N2O) fluxes have been reviewed from wastewater treatment plant (WWTP), constructed wetlands (CWs) and irrigated rice fields (IRF) in India and compared with other countries like Australia, Europe and China. The emission of CH4, CO2 and N2O fluxes from WWTP in Australian condition varied in an average from 0 to 111, 0 to 769 and 0 to 3 ton/year respectively whereas in Indian condition CH4 and N2O fluxes varied in an average from 0 to 6, and 0 to 0.01 ton/year. The higher emission of CH4 and N2O in Australia might be due to higher capacity of WWTP and advance biological treatment plant as compared to India. In Indian and China climatic condition the emission of CH4, CO2 and N2O fluxes from IRF varied from 107 × 104 to 110 × 104, 2116 × 104 to 6096 × 104 and 4 × 104 to 5 × 104, 644 × 104 to 1202 × 104, 205 × 104 to 1208 × 104 and 29 × 104 to 41 × 104 ton/year respectively. The higher fluxes of GHG w.r.t CH4 and N2O might be due to continuous flooding in China, application of nitrogen fertilizers in large scale in the rice field, and likely to be due to overburden pressure for production of rice as compared to India. CWs are the well-known natural CH4 producer in the atmosphere. The emission of CH4 from CWs in India and Europe varied from 46 to 1103 and negative to 38,000 mg/m2/day respectively. CH4 emission depends on tropical coastal wetland condition and type of surface flow in the wetland. India is fewer producers to GHGs as compared to other countries. Appropriate management plan will further reduce the emission of GHGs as well as ambient air pollution.

The present study investigated the carbonaceous aerosol with respect to organic carbon (OC), elemental carbon (EC) and total carbon (TC) in particulate matter (PM10) in indoor environment of cafeteria located at Netaji Subhash Place, one of the hotspot locations for pollution in northwest district of Delhi during 2014–15 winter season. The collections of samples were carried out during the period of three months (December 2014 to February 2015). PM10 samples were collected by APM 800 samplers (Envirotech Pvt. Ltd., India) on Whatman 37 mm microfiber quartz filter papers for 2–3 hourly bases in the dining area of food court. The flow rate varied from 2.4 lpm to 3 lpm during the period of collection of samples. Indoor PM10 concentrations varied from 1830 to 3212 µg/m3. The concentration of OC, EC and TC in PM10 size of particulate matter varied from 54 to 318, 11 to 71 and 70 to 364 µg/m3, respectively. The percentage contribution of OC and EC in TC were varied from 80 to 90% and 10 to 20%, respectively. The percentage contribution of TC in PM10 varied from 10 to 20%, respectively. The concentration of PM10 at indoor environment of cafeteria was alarmingly high as compared to National Ambient Air Quality Standard (NAAQS), 2009. The present study revealed that concentrations of PM10, OC and EC at indoor environment of cafeteria were influenced by indoor and outdoor air pollution, meteorological parameters and guest count.

Present study aims to examine the impact of lockdown on spatio-temporal concentration of PM2.5 and PM10 - categorized and recorded based on its levels during pre-lockdown, lockdown and unlock phases while noting the relationship of these levels with meteorological parameters (temperature, wind speed, relative humidity, rainfall, pressure, sun hour and cloud cover) in Delhi. To aid the study, a comparison was made with the last two years (2018 to 2019), covering the same periods of pre-lockdown, lockdown and unlock phases of 2020. Correlation analysis, linear regression (LR) was used to examine the impact of meteorological parameters on particulate matter (PM) concentrations in Delhi, India. The findings showed that (i) substantial decline of PM concentration in Delhi during lockdown period, (ii) there were substantial seasonal variation of particulate matter concentration in city and (iii) meteorological parameters have close associations with PM concentrations. The findings will help planners and policy makers to understand the impact of air pollutants and meteorological parameters on infectious disease and to adopt effective strategies for future., Graphical abstract Unlabelled Image

The characteristics and sources of carbonaceous aerosol (CA) was studied during winter in the lower atmosphere of Kolkata, a megacity situated in the lower Indo-Gangetic plain region. The city air was laden with typically high EC (15.4 ± 9.4 μg/m3) and OC (32.2 ± 17.8 μg/m3) in winter. NASA's MERRA-2 reanalysis aerosol products underestimated PM2.5, EC, and OC with a mean bias of 41.0 ± 56.8 μg/m3, 10.1 ± 9.3 μg/m3, and 10.8 ± 18.2 μg/m3, respectively. The EC/BC ratio for the atmosphere of Kolkata was estimated to be 1.03 ± 0.50. Levoglucosan was estimated in PM2.5 as a biomass burning tracer (266.9 ± 189.5 ng/m3). Source apportionment of CA using the tracer method indicated 43% of CA (19% of total PM2.5) was of secondary origin. 49% of total CA (21% of PM2.5) was from fossil fuel combustion, consisting of 23% of EC and 26% OC. Biomass burning contributed to 8% of CA and 3% of PM2.5. The diel trend of EC indicated equivalent primary emission throughout the day except being significantly high in the morning time during rush hours of traffic and increased residential combustion. Despite lower dispersion, OC formation was much higher during sunlight, indicating extensive secondary organic aerosol formation.

In South Asia, combustion of solid fuel for residential heating and cooking is a major emission source of particulate-phase polycyclic aromatic hydrocarbons (p-PAHs), a potent carcinogen for human health. The emission factors (EFs) and source diagnostic ratios of PAHs currently used in regional inventory models have been estimated from controlled laboratory tests, which do not accurately reflect real-world combustion scenarios observed in rural Indian households. Consequently, the health effects associated with p-PAH levels in indoor and ambient air could be severely underestimated and undervalued. We performed a nationwide study across ten different states in the Indian subcontinent to evaluate the EFs and source diagnostic ratios of sixteen U.S. Environmental Protection Agency (EPA) identified high priority p-PAHs emitted from residential solid biomass combustion. Our estimated average annual EFs were 2.4–18.3 fold higher than those reported from previous laboratory-based investigations. Carcinogenic toxicity analysis shows that combustion of dung cake and coal ball, both widely used residential solid fuels, posed the most risk (80% and 59% respectively) in comparison to other PAHs owing to predominant emission of benzo[a]pyrene. Our findings underscore the importance of improved laboratory testing and field validations as crucial steps toward more accurate emission inventories and better assessment of public health impacts.

A short-term study was conducted with a view to assess the ambient air quality in the surroundings area of compost plant at Okhla, Delhi. Three selected locations viz., CRRI Campus, Hazi Colony, and Gaffar Manzil were selected during the month of November 2008. The study revealed that 24 hourly average concentration of respirable suspended particulate matter (RSPM) at all selected locations were alarmingly high as compared to National Ambient Air Quality Standards (NAAQS) specified by Central Pollution Control Board (CPCB) 2009, during the study period. The 24 hourly average concentrations of sulphur dioxide (SO2) and ammonia (NH3) were within the permissible limits prescribed by the NAAQS. Nitrogen dioxide (NO2) concentration was found to exceed the permissible limits at all the three locations with percent exceedence ranging between 67%-75%. High concentrations of NO2 could be due to auto-exhaust emissions on Delhi- Mathura road, burning of LPG gas for domestic use, incinerator stack gases and diesel run electric generator. The concentrations of H2S were low, which could be due to aerobic nature of waste processing composting plant. The 8 hourly average concentration of CO was quite high at all the three monitoring stations. Percent exceedence of CO levels ranged between 83% - 86%. The localized domestic and automobile emissions in surrounding areas could be the major contributor of CO. The overall assessment of the air quality during the study period at selected locations indicated that the maximum contribution of pollutant responsible for critical Air Quality Index (AQI) values was the respirable particulate matter (RSPM) which fell under the category of severe on majority of the days. Keywords: Compost Plant, Air Pollutants, Air Quality Index (AQI)

Air pollution in India during COVID-19 lockdown, which imposed on 25th March to 31st May 2020, has brought a significant improvement in air quality. The present paper mainly focuses on the scenario of air pollution level (PM2.5, PM10, SO2, NO2 and O3) across 57 urban agglomerations (UAs) of India during lockdown. For analysis, India has been divided into six regions - Northern, Western, Central, Southern, Eastern and North-Eastern. Various spatial statistical modelling with composite air quality index (CAQI) have been utilised to examine the spatial pattern of air pollution level. The result shows that concentration of all air pollutants decreased significantly (except O3) during lockdown. The maximum decrease is the concentration of NO2 (40%) followed by PM2.5 (32%), PM10 (24%) and SO2 (18%). Among 57 UA’s, only five - Panipat (1.00), Ghaziabad (0.76), Delhi (0.74), Gurugram (0.72) and Varanasi (0.71) had least improvement in air pollution level considering entire lockdown period. The outcome of this study has an immense scope to understand the regional scenario of air pollution level and to implement effective strategies for environmental sustainability.

Measurement of biological particles (bioaerosols) in ambient air is of great importance as it is directly linked with the health issues. However, data on the bioaerosols characterization are scarce. Here we report on the concentration and characterization of bioaerosols (including bacterial and fungal aerosols) as well as determination of organic and elemental carbon (OC and EC) in total suspended particulate matter (TSPM) at a busy roadside restaurants-cluster site in New Delhi. In addition, 14 carbonyl volatile organic compounds (carbonyl VOCs) were also measured and their relationship with bioaerosols and OC/EC is assessed. The culturable airborne bacterial and fungal concentrations (CAB and CAF) at restaurant area varied significantly in different seasons ranging from 1.7 x 10(4)-9.8 x 10(4) (averaged 6.3 x 10(4) +/- 2.6 x 10(4) cfu m(-3)) and 3.5 x 10(2)-9.5 x 10(3) (3.9 x 10(3) +/- 3.1 x 10(3) cfu m(-3)) cfu m(-3), respectively. Major concentration peaks of TSPM, OC, EC as well as bacterial and fungal aerosols were found in winter and spring seasons. These peaks can be attributed to the low atmospheric boundary layer (ABL) height and favourable meteorological conditions for microbial growth in winter and spring seasons in New Delhi. Good correlations (R-2 > 0.5) were observed between CAB, CAF, TSPM and OC. On the other hand, CAB and CAF were not found to be correlated with carbonyl compounds (R2 < 0.2) indicative of their diverse sources. The bacterial identification was done by 16s rDNA sequencing and the identified strains were Bacillus sp., Bacillus firmus, Bacillus licheniformis, Bacillus cereus, Bacillus pumilus, Acinetobacter sp. and Acinetobactor radioresistens gene. Predominant fungal genera identified were Aspergillus, Cladosporium, Alternaria and Fusarium, which are known for adverse health effects causing numerous allergic and pathogenic inflammations.

Size-segregated aerosol samplings were carried out during 2013-14 at Okhla landfills, Delhi, which is a municipal solid waste dumping station. Aerosol samples were collected on quartz filters using an Andersen impactor sampler having 9-stages with cut-off diameter >9.0, 9.0-5.8, 5.8-4.7, 4.7-3.3, 3.3-2.1, 2.1-1.1, 1.1-0.65, 0.65-0.43, 9.0 μm. Fungal spores mostly peaked in coarse sizes (2.1-5.8 μm) and showed unimodal size distribution. Predominant identified bacterial strains were mostly belonged to Bacillus, Staphylococcus, Streptococcus, Klebseilla and Escherichia genera. Most of the identified fungal spores are known for adverse health effects causing numerous allergic and pathogenic inflammations. These results suggest that the open-solid waste dumping sites are a major source of bioaerosols, and residents living in the nearby areas of landfills are at high health risks.

A fugitive emission of natural gas during the extraction of oil and gas and its transportation through the pipeline has potential threat to the environment. Natural gas (NG) is the mixture of hydrocarbon gases consisting primarily of methane and other varying hydrocarbons, a small fraction of carbon dioxide, hydrogen, nitrogen, hydrogen sulphide and rare trace gases like helium, neon, xenon etc. The colorless and odorless NG has a wide range of applications as a cleaner fuel. The rapid urbanization, industrialization and economic growth all over the world demand the increasing transportation capacity of NG. Though the transportation pipeline are laid with well-equipped sophisticated technology and leak detection sensors, however still there are risk factor associated for leakage of the gases and explosion. The impacts of man-made disaster are in terms of deaths, injury, losses in economics, property and also having the adverse effect on ecology. The integrity of the NG pipeline system can be achieved by adopting continuous sophisticated up gradation technology. It also requires operation and maintenance of the pipeline at regular interval.

Urbanization and industrialization in Delhi are growing very rapidly. As a consequence, aerosol emissions are increasing, thus leading to poor ambient air quality for human health. The precise sources and chemical composition of carbonaceous aerosols are not well known. In India, carbonaceous aerosols represent a major part, of around 50 %, of PM2.5: the particulate matter with aerodynamic diameter lower than 2.5 µm. Here, we investigated carbonaceous aerosol in PM2.5 fraction monthly in the industrial area of Delhi in 2011. Results show annual average concentrations of PM2.5 of 145.59 µg/m3, of organic C of 41.12 µg/m3 and of elemental C of 13.25 µg/m3. Organic C and elemental C were higher in post-monsoon and winter seasons. Organic and elemental C were correlated in pre-monsoon with R 2 of 0.83, and in winter with R 2 of 0.79, implying the existence of similar emission sources. The organic/elemental C ratios in PM2.5 ranged from 2.71 to 5.29 with an annual average of 3.28, indicating that vehicle exhaust, coal smoke and biomass burning are the sources of carbonaceous fractions in Delhi.

The paper deals with an economic manufacturing quantity (EMQ) model for the selling price and the time dependent demand pattern in an imperfect production process. Due to long-run, machine breakdown may occur, as a result, the system may shift to out-of-control state from in-control state and production systems begin to produce imperfect quality items. The production of imperfect items increases with time. All imperfect quality items are reworked at a fixed cost to restore these to its original quality. To reduce the production of the imperfect quality items, we consider reliability as a decision variable along with the development cost and the production cost as a function of reliability. The profit function is maximized by Euler-Lagrange formula. The numerical example, sensitively analysis, and graphical illustrations are given to illustrate the model.

The highly populated Indian regions are currently in a phase of rapid economic growth resulting in high emissions of carbonaceous aerosols. This leads to poor air quality and impact on climate. The chemical composition of carbonaceous aerosols has rarely been studied in industrial areas of India. Here, we investigated carbonaceous aerosols in particulate matter (PM) monthly in the industrial area of Delhi in 2011. The concentrations of organic C and elemental C in PM10 fraction were analyzed. Results show a clear seasonal variability of organic and elemental C. PM10 ranged 95.9–453.5 μg m−3, organic C ranged 28.8–159.4 μg m−3, and elemental C ranged 7.5–44.0 μg m−3; those values were higher than reported values. Organic and elemental C were correlated with each other in pre-monsoon and winter seasons, implying the existence of similar emission sources such as coal combustion, biomass burning and vehicular exhaust. The annual average contribution of total carbonaceous aerosols in PM10 was estimated as 62 %.

This study assessed the concentrations of airborne heavy metals (HMs) in particulate matter with a cutoff size of 10 µm (i.e., PM10) in an industrialized urban area (Naraina Industrial Area) of New Delhi, India. The samples were collected from January to December, 2011. The annual mean concentrations of selected HMs were as follows As (0.002 ± 0.002), Cd (0.030 ± 0.020), Co (0.003 ± 0.002), Cr (0.170 ± 0.081), Cu (0.183 ± 0.120), Fe (4.774 ± 1.889), Mn (0.258 ± 0.145), Ni (0.170 ± 0.146), Pb (0.345 ± 0.207) and Zn (1.806 ± 1.042) µg/m3. The seasonal trend for HMs followed the order postmonsoon > winter > premonsoon > monsoon. Principal component analysis-multiple linear regression (PCA-MLR) suggested the three major emission sources: industrial emission (70 %), mobile and stationary combustion sources (16 %), and suspended/re-suspended dust (14 %). Mean seasonal concentrations of PM10 exceeded both the 24-hour and annual Indian National Ambient Air Quality Standards (NAAQS) of 60 and 100 µg/m3, respectively, in all four seasons. Mean seasonal Ni concentrations in Delhi ambient air also exceeded the 24-h annual NAAQS of 0.020 µg/m3 during all four seasons. Mean Pb concentrations exceeded the annual NAAQS of 0.50 µg/m3 only during the post monsoon season. The high levels of Ni- and Pb-contaminated PM10 would appear to present the possibility of significant health risks.

The GW contamination has become a grave problem due to rapid growth of population, expansion of irrigation activities, industrialization and high rate of urbanization in India. Over the last few decades, the land and water use patterns have changed drastically in India. GW is an important resource for drinking purpose which contains over 90% of the fresh water resources (Sabahi et al. 2009). The untreated industrial effluents discharged into the surface water sources cause severe GW pollution in the industrial belt (Mondal et al. 2005). People are becoming more aware of the complexity of the nature and the delicate balance that exist with the global ecosystem (Ahmet et al. 2006). The National Capital Territory (NCT) of Delhi, India is a water scare state with a deficit in the drinking water supply to its resident (Shekhar et al. 2009). The Yamuna flood plain is only potential fresh GW resources in Delhi. The exploration, exploitation and unscientific management of GW resources in the NCT of Delhi, India have posed a serious threat of reduction in quantity and deterioration of quality (Adhikary et al. 2009). In Delhi, GW level has gone down approximately 8 m per year in the last 10 years which is at the rate of about 0.8 m per year (CGWB 2006). Annual replenishable GW sources of NCT Delhi are about 297 million cubic meter while the GW draft is about 480 million cubic meter (Chatterjee et al. 2009). Thus out of nine districts, seven districts of NCT Delhi have been categorized as overexploited with regards to the dynamic GW resources (CGWB 2006).The city is forced to meet 50 % of its water requirement from GW (Kumar et al. 2006). Solid and liquid waste emanating from the industry are inevitability the by products of manufacturing process which contains toxic chemicals and trace metals. The open unlined drains and availability of dumping of toxic industrial waste in nearby recharge of GW areas, act as the source of GW pollution (Dutta et al. 1997).

A study was conducted in the residential areas of Delhi, India, to assess the variation in ambient air quality and ambient noise levels during pre-Diwali month (DM), Diwali day (DD) and post-Diwali month during the period 2006 to 2008. The use of fireworks during DD showed 1.3 to 4.0 times increase in concentration of respirable particulate matter (PM(10)) and 1.6 to 2.5 times increase in concentration of total suspended particulate matter (TSP) than the concentration during DM. There was a significant increase in sulfur dioxide (SO(2)) concentration but the concentration of nitrogen dioxide (NO(2)) did not show any considerable variation. Ambient noise level were 1.2 to 1.3 times higher than normal day. The study also showed a strong correlation between PM(10) and TSP (R (2) ≥ 0.9) and SO(2) and NO(2) (R (2) ≥ 0.9) on DD. The correlation between noise level and gaseous pollutant were moderate (R (2) ≥ 0.5). The average concentration of the pollutants during DD was found higher in 2007 which could be due to adverse meteorological conditions. The statistical interpretation of data indicated that the celebration of Diwali festival affects the ambient air and noise quality. The study would provide public awareness about the health risks associated with the celebrations of Diwali festival so as to take proper precautions.

Yamuna river pollution has been extensively studied with regard to some selected parameters in five locations at Palla, Nizamuddin Midstream, Nizamuddin Quarter Stream, Agra Canal Midstream, and Agra Canal Quarter Stream in Delhi, India. Seasonal and location-wise variation of pollutants namely dissolve oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), ammonia (AMM), total coliform and fecal coliform were studied for 6 years during the period of 2000–2005. The study results revealed the lowest level of pollution during monsoon. The statistical analysis revealed a positive correlation between DO, BOD, COD, TKN, and AMM.