Seasonal variations of dustfall fluxes and biochemical parameters in the foliage of selected indoor plants in Delhi, India.

This study reports the seasonal variations in dry deposition of coarse and fine particles on the foliar surfaces of common indoor plants viz. Ficus elastica, Ficus lyrata, and Schefflera arboricola along with their biochemical changes in the urban households of metropolitan Delhi. The dustfall fluxes were significantly higher at the industrial site as compared to residential site and temporal variations indicated higher dustfall fluxes during the winter months as compared to other seasons. Seasonal concentrations of chlorophylls, pH, and soluble sugars were higher during monsoon season for the indoor plants whereas ascorbic acid content was higher in the winter season indicating more stress. The results of correlation plots revealed that the variations observed in the biochemical traits were interlinked with the changes in dustfall fluxes during different seasons, thereby reflecting the changes in air pollution stress faced by plant foliage. The air pollution tolerance index and anticipated performance index were evaluated to understand the overall tolerance of indoor plants toward air pollution which can be utilized in phytoremediation techniques. It was concluded that among the studied indoor plants, Ficus elastica and Ficus lyrata are better plant species than Schefflera arboricola for improving indoor air quality.

The novelty of this work lies in studying the spatial and temporal variations in the deposition of indoor dust on foliar surfaces of plants in the households of a highly polluted metropolitan. Based on the biochemical parameters, the air pollution tolerance index (APTI) and anticipated performance index (API) have been calculated for the first time for Ficus elastica, Ficus lyrata, and Schefflera arboricola. The study strengthens the existing knowledge regarding the role of leaves as a platform to capture dust particles and role of indoor plants in improving air quality. The outcomes of this study can be applied in modern day concepts for urban areas such as nature-based solutions for air pollution mitigation, vertical greenery systems (VGS), green roofs, and outdoor green walls.

Abundance and variation of gaseous NH3 in relation with inorganic fertilizers and soil moisture during Kharif and Rabi season.

In an agricultural country like India, inorganic fertilizers are the major contributors of atmospheric NH3 in rural areas affecting soil, vegetation and water bodies. In this study, day-night and seasonal variation of ammonia emissions were measured from July 2017 to June 2018 during Kharif and Rabi crop seasons at a rural agricultural site in Jhajjar district of Haryana. Also, NH3 emission inventory is prepared for the amount of fertilizers applied during its basal and top dressing. NH3 concentrations were noticed significantly lower after basal dressing of DAP fertilizers as compared to the concentrations after top dressing of urea. NH3 concentration in air increased with decrease in water saturation of the soil. NH3 emission was recorded as 1.4 to 45.2, 63.1 to 190.9, and 98.9 to 187.5 µg m-3 during sowing, fertilizer addition, and grain filling stages, respectively, in Kharif season. Apart from these crop stages, NH3 was measured as 56.8 to 249.5 µg m-3 during crop residue burning period. On the other hand, NH3 emissions ranged from 22.9 to 68.4, 59.4 to 104.71, 26.3 to 56.0, 48.2 to 147.2, and 21.5 to 80.4 µg m-3 during sowing, crown root initiation (CRI), panicle initiation, grain filling, and maturity crop, respectively, in Rabi season. The average NH3 concentrations during Kharif season (125.3 µg m-3) were significantly greater than the concentrations during Rabi season (51.8 µg m-3). However, a reduction in the NH3 values was observed in the period between Kharif and Rabi seasons, which could be attributed to the wet deposition during monsoon and gas to particle conversion due to less temperature conditions during the periods.

Gaseous and particulate reactive nitrogen species in the indoor air of selected households in New Delhi.

The present study reports the indoor abundance of inorganic trace gases (NH3, NO2 and SO2) and their corresponding particulates (NH4+, NO3- and SO42-) along with other major ionic species present in the aerosol form (Cl-, F-, Na+, K+, Ca2+ and Mg2+), in the urban households of megacity Delhi (India). Two different households (DH site and MH site) were selected in the city based on the variation in the land use patterns of the locations in which they were situated. Trace gases followed the order NH3 > SO2 > NO2 at both the sites with NH3 contributing about 90% and 85% to the total Nr species at DH and MH sites, respectively. NH3 showed maximum indoor concentrations during monsoon season whereas NO2 and SO2 were higher during winter season. The gas to particle conversion of the inorganic trace gases was studied by calculating their oxidation ratios which followed the order SOR > NOR > NHR, indicating that SO2 showed more oxidative conversion to SO42- as compared to NO2 and NH3 in the indoor setup. The chemical composition of the particulates revealed that Ca2+ and SO42- were the most abundant cation and anion, respectively, among the measured ionic species at both sites and the concentrations of all the major ions were higher for the industrial MH site as compared to the residential DH site. Source apportionment using principal component analysis and mass ratios showed that indoor activities such as cooking, cleaning along with others such as biomass burning and dust resuspension were responsible for the indoor composition of particulates at DH site whereas outdoor influences such as coal burning and industrial emissions from local sources were prominent at MH site due to its industrialized surroundings. For naturally ventilated households (such as the present study), it was observed that the emissions generated indoors as well as the characteristic outdoor influences seem to influence the overall indoor air composition and quality.