RESUMO
The strict nationwide lockdown imposed in India starting from 25th March 2020 to prevent the spread of COVID-19 disease reduced the mobility and interrupted several important anthropogenic emission sources thereby creating a temporary air quality improvement. This study conducts a multi-scale (national-regional-city), multi-species, and multi-platform analysis of air pollutants and meteorological data by synergizing surface and satellite observations. Our analysis suggests a significant reduction in surface measurements of nitrogen dioxide (NO2) (46-61 %) and fine particulate matter (PM2.5) (42-60 %) during the lockdown period that are also corroborated by the reduction in satellite observed aerosol optical depth (AOD) (3-56 %) and tropospheric NO2 column density (25-50 %) data over multiple cities. Other species, namely coarse particulate matter (PM10) (24-62 %), ozone (22-56 %) also showed a substantial reduction whereas carbon monoxide (16-46 %), exhibited a moderate decline. In contrast, sulfur dioxide (SO2) levels did not show any defined reduction trend but rather increased in Mumbai, Bengaluru, and Kolkata. The temporary air quality improvement achieved by the painful natural experiment of this pandemic has helped demonstrate the importance of reducing emissions from other sectors along with transportation and industry to achieve the national air quality targets in the future.
RESUMO
Metals contained in the waste transfer to the waste incineration products, including flue gas, fly ash, and bottom ash, as different oxide, nitride, carbides, and other phases. Most of the metal-based phases formed in incineration are toxic and their emissions need to be strictly controlled. Therefore, behavior of metal species during incineration must be well understood. Such understanding is possible based on the experimental identification of the metal phases formed in the waste combustion and determination of their concentration in various incineration products. To avoid well-known experimental difficulties of the industrial waste incinerators associated with the poor fuel/conditions reproducibility and limited instrumentation, a 140,000 Btu/h pilot-scale, laboratory burner was constructed, characterized and operated at NJIT. A synthetic fuel representative of the municipal solid waste in the US was formulated and produced in 600-Lb batches. The solid fuel contained Fe and SiO2 as main constituents, and was doped with trace amounts of Al, Ni, Cr, Hg and PbO. Several experiments have been conducted on combustion of the synthetic fuel in the pilot-scale incinerator with varying fuel-air equivalence ratio. Both gaseous and condensed combustion products were sampled and analyzed. Atomic absorption spectroscopy and X-ray diffraction were used to analyze total metal contents and metal containing phases in the incineration products. Thermodynamic equilibrium computations were performed to obtain the adiabatic flame temperature and identify the phases of the metal-containing products formed at the equilibrium conditions. The results of the equilibrium computations performed at the varied fuel/air ratios were compared with the observed experimental results.
