Very high particulate pollution over northwest India captured by a high-density in situ sensor network.

Exposure to particulate matter less than 2.5 µm in diameter (PM2.5) is a cause of concern in cities and major emission regions of northern India. An intensive field campaign involving the states of Punjab, Haryana and Delhi national capital region (NCR) was conducted in 2022 using 29 Compact and Useful PM2.5 Instrument with Gas sensors (CUPI-Gs). Continuous observations show that the PM2.5 in the region increased gradually from < 60 µg m-3 in 6-10 October to up to 500 µg m-3 on 5-9 November, which subsequently decreased to about 100 µg m-3 in 20-30 November. Two distinct plumes of PM2.5 over 500 µg m-3 are tracked from crop residue burning in Punjab to Delhi NCR on 2-3 November and 10-11 November with delays of 1 and 3 days, respectively. Experimental campaign demonstrates the advantages of source region observations to link agricultural waste burning and air pollution at local to regional scales.

Understanding seasonal variation in ambient air quality and its relationship with crop residue burning activities in an agrarian state of India.

In India, Indo-Gangetic Plains (IGP) is becoming the hotspot of air pollution due to increasing anthropogenic activities such as rapid industrial growth, infrastructure development, transportation activities, and seasonal practice of crop residue burning. In the current study, seasonal variation in ambient air quality for 14 parameters, i.e., particulate matter (PM), trace gases, and volatile organic compounds (VOCs), along with meteorological parameters, was studied in 21 districts of the Haryana state for year 2019, situated in IGP. To analyze spatial variation of pollutants, ambient air quality data of 23 continuous ambient air quality monitoring stations were divided into three zones based on ecology and cropping pattern. All the zones showed annual mean PM10 and PM2.5 concentrations much higher than national ambient air quality standards. Annual mean PM10 concentration (±standard deviation) in Zones-1, 2, and 3 was 156±86, 174±93, and 143±74 µg m-3, whereas for PM2.5 was 71±44, 85±54, and 78±47 µg m-3. The results showed a considerable seasonal variation in the concentration of all pollutants. Most of the pollutants peak in the post-monsoon season, followed by winters in which crop residue burning predominates in many parts of the Haryana. PM10 concentrations increased by 65-112% and PM2.5 concentrations increased by 131-147% in the post-monsoon season compared to monsoons. The post-monsoon season showed the highest concentration of PM10, NO, and toluene (Zone-1); and PM2.5, NH3, CO, and benzene (Zone-2); whereas in winters, SO2 (Zone-1); ethylbenzene, m,p-xylene, and xylene (Zone-2); and NO2 and NOx (Zone-3) showed the maximum pollution levels. The O3 concentration was highest in the pre-monsoon season (Zone-1). The satellite-based fire counts and PCA results show a significant influence of crop residue burning in the post-monsoon season and solid biomass burning in winters on Haryana's air quality. The study could help to understand seasonal variation in ambient air quality and the influence of factors such as crop residue burning in the IGP region, which could help to formulate season-specific control measures to improve regional air quality.

A high-resolution emission inventory of air pollutants from primary crop residue burning over Northern India based on VIIRS thermal anomalies.

Emissions from the crop residue burning adversely affect the regional and global air quality including public health. In this study, a district-wise comprehensive emission inventory of key pollutants (PM2.5, PM10, CO, CO2, SO2, NOx, N2O, NH3, CH4, NMVOC, EC, OC, PAH) emitted during primary crop residue burning was developed using activity data for the major agrarian states of north India for the agricultural year 2017-18. The emissions were scaled to the spatial resolution of 1 km grid to study the spatial distribution of crop residue burning activities using VIIRS Thermal anomalies datasets. An estimated 20.3 Mt and 9.6 Mt of crop residue were burned in Punjab and Haryana, resulting in an emission of 137.2 Gg and 56.9 Gg of PM2.5 and 163.7 Gg and 72.1 of PM10 Gg for respective states. The emissions of EC, OC, and PAHs were 8.6 Gg, 45.7 Gg, and 0.08 Gg in Punjab, whereas in Haryana emissions were 3.7 Gg, 17.7 Gg, and 0.03 Gg, respectively. The results show that rice and wheat crops were major contributor to residue burnt at the field (>90%) leading to the high load of atmospheric emissions in the IGP region. Further, CO2 equivalent greenhouse gas emissions were 34.8 Tg and 17.3 Tg for Punjab and Haryana, respectively. Around 30000 and 8500 active fires were detected by VIIRS over the agricultural area of Punjab and Haryana during the studied year. The GIS-based bottom-up approach using gridded emission inventory shows pollutant distribution dominates over the south-western part of Punjab and north-western region of Haryana. The proximity of these regions to Delhi and transboundary movement of emissions towards Indo-Gangetic plains causes high air pollution episodes. The high-resolution inventory of various pollutants will be useful for regional air quality models to better predict and manage the hotspot of air pollution.

Evaluation of groundwater contamination in Chandigarh: Source identification and health risk assessment.

The major objective of the current study is to estimate the groundwater quality and identify the likely sources of contamination in Chandigarh, India. Total 80 groundwater samples were collected from different locations and at various depths. Further, physcio-chemical analysis was done to estimate pH, electrical conductivity (EC), total dissolved solids, total hardness (TH), total alkalinity (TA), Na+, K+, Cl-, SO42-, PO43- and NO3-. The groundwater samples collected from shallow water sources contain higher concentration of total dissolved salts. EC, TA, Cl-, TH, Na+, and K+ were found relatively higher in the shallow aquifer (<150 ft). Based on the location of pollution sources at the surface and consecutive geo-statistical distribution of physicochemical characteristics, this study suggests that non-scientific disposal of municipal solid waste, dumping of industrial waste and agricultural activities, in the nearby areas lead to the deterioration of groundwater of shallow aquifer. These observations were also confirmed using various water quality indices and outcomes of multivariate modeling, including principal component analysis. Health risk assessment for nitrates indicated that 29 groundwater samples pose non-carcinogenic health risk for children due to dermal and oral exposure. Hence, there is a need to establish a system for regularly assessing the groundwater quality to minimize public health risks.

Real-time monitoring of air pollutants in seven cities of North India during crop residue burning and their relationship with meteorology and transboundary movement of air.

Air pollutants emissions due to the burning of crop residues could adversely affect human health, environment, and climate. Hence, a multicity campaign was conducted during crop residue burning period in Indo Gangetic Plains (IGP) to study the impact on ambient air quality. Seventeen air pollutants along with five meteorological parameters, were measured using state of the art continuous air quality monitors. The average concentration of PM10, PM2.5, and PM1 during the whole campaign were 196.7±30.6, 148.2±20, and 51.2±8.9 µgm-3 and daily average concentration were found several times higher than national ambient air quality standards for 24h. Amritsar had the highest average concentration of PM2.5 (178.4±83.8 µgm-3) followed by Rohtak and Sonipat (158.4±79.8, 156.5±105.3µgm-3), whereas Chandigarh recorded the lowest concentration (112.3±6.9µgm-3). The concentration of gaseous pollutants NO, NO2, NOx, and SO2 were also observed highest at Amritsar location, i.e., 6.6±2.6ppb, 6.2±0.7ppb, 12.7±3.0ppb, and 7.5±3.3ppb respectively. The highest average O3 and CO were 22.5±19.3ppb and 1.5±1.2ppm during the campaign. The level of gaseous pollutants and Volatile organic compounds (VOCs) found to be elevated during the campaign, which can play an important role in the formation of secondary air pollutants. The correlation of meteorology and air pollutants was also studied, and O3 shows a significant relation with temperature and UV (R=0.87 and 0.74) whereas VOCs shows a significant correlation with temperature (R=-0.21 to -0.47). Air quality data was also analyzed to identify sources of emissions using principal component analysis, and it identifies biomass burning and vehicular activities as major sources of air pollution.