Lockdown seems the most effective way to prevent the spread of Coronavirus disease (COVID-19) as no vaccine is currently available in the market to cure it. Thus, India has enforced nation-wide lockdown from 25 th March to lower the spread of this contagious virus and associated illness. This study aims to quantify the changes in pollution levels as well as meteorology during the 6-weeks COVID-19 lockdown over 17 cities of India for 5 major criteria pollutants using publicly available air quality data. Hourly averaged data is accessed from the air quality monitoring stations during the lockdown and immediate pre-lockdown periods and also corresponding data from the previous year (2019). During the lockdown, PM 2.5 , PM 10 , NO 2, and CO reduced significantly with relatively small changes in meteorological conditions compared to the prelockdown period. The highest decline is observed over Ahmedabad (68%), Delhi (71%), Bangalore (87%), and Nagpur (63%) for PM 2.5 , PM 10 , NO 2 , and CO, respectively. The Northern region shows the highest decline for all the pollutants with most days below NAAQS during lockdown-86%, 68%, and 100% compared to 18%, 0%, and 38% in 2019 for PM 2.5 , PM 10 , and NO 2 , respectively. The smaller cities Dewas and Jorapokhar show lesser improvement with only 3% and 16% improvement in days under NAAQS for PM 2.5 . SO 2 is the least affected pollutant with little improvement. The major decline is observed during 7-10 am and 7-10 pm hours of the day for PM 2.5 , PM 10 , NO 2 , and CO with more than 40% reduction. The meteorological changes are very small and heterogeneous over India showing a similar extent of changes compared to the previous year but the pollution levels have reduced significantly. Thus, the sharp decline in pollutant concentration during the ~6 weeks period national lockdown can be attributed to the reduced economic and transport activities.
<p>Fired clay brick kiln (FCBK) industry is one of the unorganized and often overlooked sectors in terms of its regional air quality and health impacts. Approximately 87% of the 1.5 trillion clay bricks produced worldwide annually are made in Asia. These bricks are typically fired in small-scale traditional kilns that burn coal or biomass without air pollution controls. Clamp kiln is the most traditional technology of brick manufacturing. It is a batch-style kiln that produces 10,000-200,000 bricks per batch in a time period of two to four weeks. It uses coal as primary and firewood and rice husk as supplementary fuel. There is no chimney, and hence the smoke escapes from the cracks at the top and from the sides of the kiln. Very little information is available on aerosols emitted from these kilns. Therefore, it&#8217;s important to accurately estimate aerosol emissions and their chemical properties from FCBK to understand their impact on regional air quality and climate. This study examines the chemical and optical properties of emitted aerosols during different stages of combustion in clamp kilns. The National Carbonaceous aerosol programme- Carbonaceous aerosol emissions, source apportionment and climate impacts (NCAP-COALESCE) network source emission measurement system was used to measure absorption and scattering properties using the Aethalometer and Integrating Nephelometer, respectively. Measurements were done for clamp kilns of different firing stages, namely ignition, propagation, and end. The combustion efficiency was >97% during the end, propagation and ignition stages. The average BC (SO<sub>2</sub>) concentration measured during the ignition, propagation and end stage was 12.5 (10) 18.5 (9), and 13.3 &#956;g-m<sup>-3</sup>(19 ppm), respectively against background of 2 &#956;g-m<sup>-3 </sup>(0 ppm) . The corresponding values of average AAE<sub>370/660</sub> (AAE<sub>660/880</sub>) during the three combustion phases were 3.6 (1.3), 2.6 (1.1) and 1.8 (1.2), respectively. The relatively high AAEs indicate a strong contribution by brown carbon aerosol, likely emitted from fuelwood and rice husk combustion during the ignition and propagation stages, respectively. This study would help characterise the combustion stage specific emissions. Further analysis is ongoing to understand the potential impacts on regional air quality and climate.&#160;</p> <p><img src="" alt="" /></p> <p>Figure 1: Emission measurement setup and different position of the multi-arm during measurement based on incoming plume</p>
<p>One-third of the Indian population relies on biomass for cooking and heating which makes the residential sector a major source of particulate matter (PM)<sub> </sub>emissions. The climate impact of indoor PM depends on the fraction of particles advecting out of the house, which is either not considered in climate impacts or some thumb rule is used. The removal mechanism can have a distinct impact on different size ranges, thus size-based characterization of exfiltration factor (fraction of particles that are advected outdoors) is very important to underpin accurate climate impact. This study examines the size-dependent ExF of PM and the influence of different parameters such as room size, type of circulation, and ventilation status on exfiltration factor (ExF). CO is used as a reference gas to understand decay associated with the air exchange, while PM removal is considered to be dependent on deposition and air exchange. An Optical Particle Sizer and an Indoor Air Quality Monitor are used for PM and CO real-time measurements. We find a significant difference in PM<sub>2.5</sub> ExF during natural (25&#177;7 %) and forced (34&#177;12 %) circulation. PM<sub>2.5</sub> ExF was lowest&#160; (i.e. 22%)&#160; when both door and window were closed. Opening the window or both window and door increased the exfiltration slightly (26 and 27 %, &#160;respectively). However, the exposure time to significantly elevated indoor PM levels can vary from 10 mins to 360 mins depending on ventilation, thus health impacts can differ significantly due to ventilation despite having an insignificant change in climate impacts. Size-based ExF for PM<sub>0.9</sub>, PM<sub>2.5</sub>, and PM<sub>10</sub> ExF were 43&#177;28, 30&#177;9 and 29&#177;9 % respectively.The integration of ExF, total PM emissions, and kitchen-type information would bring more certainty to the climate impact assessment. An extended analysis is underway to understand the importance of room size and shape.</p> <p>&#160;</p> <p><img src="" alt="" /></p> <p>Figure 1. The decay of gas and aerosol concentration from the room under different removal mechanisms. (Here, EF stands for emission factor)</p>
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