Nikki Choudhary

Bio: Nikki Choudhary is an academic researcher from Council of Scientific and Industrial Research. The author has contributed to research in topics: Environmental chemistry & Total organic carbon. The author has an hindex of 5, co-authored 9 publications receiving 145 citations. Previous affiliations of Nikki Choudhary include Guru Gobind Singh Indraprastha University & Academy of Scientific and Innovative Research.

Chemical characteristics and source apportionment of PM2.5 using PCA/APCS, UNMIX, and PMF at an urban site of Delhi, India

Abstract: The present study investigated the comprehensive chemical composition [organic carbon (OC), elemental carbon (EC), water-soluble inorganic ionic components (WSICs), and major & trace elements] of particulate matter (PM2.5) and scrutinized their emission sources for urban region of Delhi. The 135 PM2.5 samples were collected from January 2013 to December 2014 and analyzed for chemical constituents for source apportionment study. The average concentration of PM2.5 was recorded as 121.9 ± 93.2 μg m−3 (range 25.1–429.8 μg m−3), whereas the total concentration of trace elements (Na, Ca, Mg, Al, S, Cl, K, Cr, Si, Ti, As, Br, Pb, Fe, Zn, and Mn) was accounted for ∼17% of PM2.5. Strong seasonal variation was observed in PM2.5 mass concentration and its chemical composition with maxima during winter and minima during monsoon seasons. The chemical composition of the PM2.5 was reconstructed using IMPROVE equation, which was observed to be in good agreement with the gravimetric mass. Source apportionment of PM2.5 was carried out using the following three different receptor models: principal component analysis with absolute principal component scores (PCA/APCS), which identified five major sources; UNMIX which identified four major sources; and positive matrix factorization (PMF), which explored seven major sources. The applied models were able to identify the major sources contributing to the PM2.5 and re-confirmed that secondary aerosols (SAs), soil/road dust (SD), vehicular emissions (VEs), biomass burning (BB), fossil fuel combustion (FFC), and industrial emission (IE) were dominant contributors to PM2.5 in Delhi. The influences of local and regional sources were also explored using 5-day backward air mass trajectory analysis, cluster analysis, and potential source contribution function (PSCF). Cluster and PSCF results indicated that local as well as long-transported PM2.5 from the north-west India and Pakistan were mostly pertinent.

Seasonal Variation of OC, EC, and WSOC of PM 10 and Their CWT Analysis Over the Eastern Himalaya

Abstract: In the present study, seasonal transport trends and potential source regions of carbonaceous species [organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), secondary organic carbon (SOC) and total carbonaceous aerosols (TCAs)] of PM10 was evaluated over Darjeeling, an eastern Himalayas of India during August 2018–June 2019. Backward trajectories, cluster analysis, and concentration-weighted trajectory (CWT) analysis were performed to evaluate the seasonal transport pathway of carbonaceous aerosols over the region. The annual average concentration of PM10 was recorded to be 55 ± 18 μg m−3, which is close to National Ambient Air Quality Standard (NAAQS; 60 μg m−3 for annual PM10) of India. The concentration of PM10 showed maxima in pre-monsoon season (63 ± 21 μg m−3) followed by post-monsoon (56 ± 16 μg m−3), monsoon (51 ± 13 μg m−3) and winter seasons (49 ± 17 μg m−3). The study revealed that the WSOC comprises about 72% of OC concentration with maxima in post-monsoon (81% of OC) followed by winter (74% of OC), pre-monsoon (67% of OC) and monsoon seasons (66% of OC). The concentration of SOC were estimated as 1.4 ± 0.9, 1.7 ± 1.0, 2.4 ± 0.9 and 1.9 ± 0.9 µg m−3 during pre-monsoon, monsoon, post-monsoon and winter, respectively (which are accounted for 27%, 49%, 41% and 35% to the OC mass concentration, respectively). The results indicated that biomass burning could be one of the major sources of carbonaceous aerosols in Darjeeling. Five days backward trajectory analysis (including cluster and CWT analysis) revealed that the air-mass flow of pollutants towards the sampling site of Darjeeling majorly coming from continental sites (Nepal and Indo-Gangetic plain (IGP) region of India) and the Bay of Bengal (BOB).

Seasonal variation and sources of carbonaceous species and elements in PM2.5 and PM10 over the eastern Himalaya.

Abstract: The study represents the seasonal characteristics (carbonaceous aerosols and elements) and the contribution of prominent sources of PM2.5 and PM10 in the high altitude of the eastern Himalaya (Darjeeling) during August 2018–July 2019. Carbonaceous aerosols [organic carbon (OC), elemental carbon (EC), and water soluble organic carbon (WSOC)] and elements (Al, Fe, Ti, Cu, Zn, Mn, Cr, Ni, Mo, Cl, P, S, K, Zr, Pb, Na, Mg, Ca, and B) in PM2.5 and PM10 were analyzed to estimate their possible sources. The annual concentrations of PM2.5 and PM10 were computed as 37±12 μg m−3 and 58±18 μg m−3, respectively. In the present case, total carbonaceous species in PM2.5 and PM10 were accounted for 20.6% of PM2.5 and 18.6% of PM10, respectively, whereas trace elements in PM2.5 and PM10 were estimated to be 15% of PM2.5 and 12% of PM10, respectively. Monthly and seasonal variations in mass concentrations of carbonaceous aerosols and elements in PM2.5 and PM10 were also observed during the observational period. In PM2.5, the annual concentrations of POC and SOC were 2.35 ± 1.06 μg m−3 (66% of OC) and 1.19±0.57 μg m−3 (34% of OC), respectively, whereas annual average POC and SOC concentrations in PM10 were 3.18 ± 1.13 μg m−3 (63% of OC) and 2.05±0.98 μg m−3 (37% of OC), respectively. The seasonal contribution of POC and SOC were ranging from 55 to 77% and 33 to 45% of OC in PM2.5, respectively, whereas in PM10, the seasonal contributions of POC and SOC were ranging from 51 to 73% and 37 to 49% of OC, respectively. The positive relationship between OC & EC and OC & WSOC of PM2.5 and PM10 during all the seasons (except monsoon in case of PM10) indicates their common sources. The enrichment factors (EFs) and significant positive correlation of Al with othe crustal elements (Fe, Ca, Mg, and Ti) of fine and coarse mode aerosols indicate the influence of mineral dust at Darjeeling. Principal component analysis (PCA) resolved the four common sources (biomass burning + fossil fuel combustion (BB + FFC), crustal/soil dust, vehicular emissions (VE), and industrial emissions (IE)) of PM2.5 and PM10 in Darjeeling.

Wintertime carbonaceous species and trace metals in PM10 in Darjeeling: A high altitude town in the eastern Himalayas

Abstract: Carbonaceous components [organic carbon (OC), elemental carbon (EC), water soluble organic carbon (WSOC), primary organic carbon (POC), secondary organic carbon (SOC) and carbonaceous aerosols (CAs)] and major and trace elements (Na, Mg, Ca, Al, Fe, Ti, Cl, P, S, K, Cr, Ni, Cu, Zn, Mo and B) of PM10 were studied over the eastern Himalayan high altitude station [Darjeeling: 27.01°N and 88.15°E, 2200 m average mean sea level (amsl)] during winter 2018–19 (December 2018–February 2019). The carbonaceous aerosols/species (CAs) contributed to ~23% of PM10 mass concentration, whereas major and trace elements accounted for 10% of PM10. During the entire study period, the average concentrations of PM10, OC, EC, WSOC, POC, SOC and CAs were recorded as 48 ± 16 μg m−3, 5.39 ± 1.84 μg m−3, 2.60 ± 0.94 μg m−3, 3.87 ± 1.18 μg m−3, 3.40 ± 1.23 μg m−3, 1.99 ± 1.03 μg m−3 and 11.21 ± 3.78 μg m−3, respectively. Significant positive correlation between OC & EC and OC & WSOC have been observed which are indicating their common sources. WSOC/OC ratio was estimated to be 0.71 suggesting that the biomass burning is one of the major sources of carbonaceous aerosols at Darjeeling during winter. The significant positive correlation of PM10 with crustal elements (Al, Fe, Ca, Mg and Ti) as well as the correlation of Al with other crustal elements (Fe, Ca, Mg and Ti) indicates the abundance of mineral dust at the sampling site. Principal component analysis (PCA) identified the contribution of crustal/soil dust, biomass + coal burning, vehicular emissions and solid waste to the PM10 over the eastern Himalayan region of India.

Source Apportionment of PM2.5 in Delhi, India Using PMF Model.

Abstract: Chemical characterization of PM2.5 [organic carbon, elemental carbon, water soluble inorganic ionic components, and major and trace elements] was carried out for a source apportionment study of PM2.5 at an urban site of Delhi, India from January, 2013, to December, 2014. The annual average mass concentration of PM2.5 was 122 ± 94.1 µg m−3. Strong seasonal variation was observed in PM2.5 mass concentration and its chemical composition with maxima during winter and minima during monsoon. A receptor model, positive matrix factorization (PMF) was applied for source apportionment of PM2.5 mass concentration. The PMF model resolved the major sources of PM2.5 as secondary aerosols (21.3 %), followed by soil dust (20.5 %), vehicle emissions (19.7 %), biomass burning (14.3 %), fossil fuel combustion (13.7 %), industrial emissions (6.2 %) and sea salt (4.3 %).