A new perspective of probing the level of pollution in the megacity Delhi affected by crop residue burning using the triple oxygen isotope technique in atmospheric CO2.

Air quality in the megacity Delhi is affected not only by local emissions but also by pollutants from crop residue burning in the surrounding areas of the city, particularly the rice straw burning in the post monsoon season. As a major burning product, gaseous CO2, which is rather inert in the polluted atmosphere, provides an alternative solution to characterize the impact of biomass burning from a new perspective that other common tracers such as particulate matters are limited because of their physical and chemical reactiveness. Here, we report conventional ([CO2], δ13C, and δ18O) and unconventional (Δ17O) isotope data for CO2 collected at Connaught Place (CP), a core area in the megacity Delhi, and two surrounding remote regions during a field campaign in October 18-20, 2017. We also measured the isotopic ratios near a rice straw burning site in Taiwan to constrain their end member isotopic compositions. Rice straw burning produces CO2 with δ13C, δ18O, and Δ17O values of -29.02 ± 0.65, 19.63 ± 1.16, and 0.05 ± 0.02‰, respectively. The first two isotopic tracers are less distinguishable from those emitted by fossil fuel combustion but the last one is significantly different. We then utilize these end member isotopic ratios, with emphasis on Δ17O for the reason given above, for partitioning sources that affect the CO2 level in Delhi. Anthropogenic fraction of CO2 at CP ranges from 4 to 40%. Further analysis done by employing a three-component (background, rice straw burning, and fuel combustion) mixing model with constraints from the Δ17O values yields that rice straw burning contributes as much as ∼70% of the total anthropogenic CO2, which is more than double of the fossil fuel contribution (∼30%), during the study days.

Multifunctional diesel exhaust emission soot coated sponge for water treatment.

We demonstrated that a pollutant and waste, diesel exhaust emission soot (DEES) can be used as an absorbent to remove oil and organic pollutants from wastewater. The diesel exhaust emission soot coated sponge (DEES sponge) was prepared using the dip-coating method. Prepared DEES sponge was found hydrophobic in nature as the contact angle between water drop and its surface was recorded to be 147°. The DEES sponge showed high absorption capacity with various oils, without any surface modifications and pretreatments. Highest oil absorption capacity was found to be 39 g/g for engine oil. Excellent separation efficiency was recorded (max. 98.5% for engine oil). It shows promising recyclability having 95% efficiency even after 10 cycles. DEES sponge also demonstrated the capability to be used as an adsorbent due to its ability to absorb pollutants like methylene blue (MB), ciprofloxacin, and detergent from the water. It was able to adsorb 93% of the dye MB from its aqueous solution having concentration of 15 µM.