write an essay on the topic: changes in air pollution level before and after covid 19 in major cities.
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Answer:
Air pollution anomalies. When viewed broadly and globally, air pollution dropped during the lockdowns. A study based on data from satellites and more than 10,000 ground-based monitoring stations around the world found that average global air quality during lockdowns improved relative to the same periods in 2019 (Proc.25-Sep-2020
COVID-19 lockdowns had strange effects on air pollution ...
Explanation:
Answer:
Amidst the devastating Covid-19 pandemic, a rare positive has been the significant global decrease in air pollution levels. Primarily, experts have measured nitrogen dioxide (NO2), one of the six major air pollutants (in addition to particulate matter, carbon monoxide, sulfur dioxide, ground-level ozone, and lead). NO2 has, like most other gases, natural and human sources.
Natural sources include lightning, oceans, and volcanoes. However, in urban regions, natural sources of NO2 account for a small fraction of the total NO2 levels; according to a 2005 report by Australia’s Department of the Environment and Heritage, natural sources of NO2 only account for 1 per cent of overall NO2 levels in cities. Human activity is almost entirely responsible for NO2 emissions in urban regions, with road transport being the number one cause. Planes, power plants and ships, all of which burn fossil fuels, are also significant human sources of NO2. Given this, it’s unsurprising that during the stringent global lockdowns, NO2 levels have dropped significantly in urban areas, especially in India’s densely populated cities.
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Satellite imagery from the European Space Agency’s Copernicus Sentinel 5P satellite measure NO2 levels globally. These measurements accurately reflect emissions sources, because unlike other gases that can travel a significant distance from where they’re emitted, NO2 has a short lifespan and dies before it can move very far. In other words, if the Sentinel 5P satellite captures a hotspot of NO2 over Delhi, it’s highly likely it was emitted from within Delhi’s vicinity. Satellite imagery is, therefore, a highly reliable tool for measuring NO2 emissions, especially if data with high levels of cloud coverage is excluded.
The global decreases in NO2 levels were first seen in China, where levels plummeted dramatically following the strict quarantine measures enforced in late January. As nations in Europe and North America followed China’s lead in late February and March, similar trends have been observed globally. India’s nationwide lockdown, in particular, has had stunning effects on air pollution levels. With citizens quarantined at home, road transportation and power plant operations have come to a grinding halt, and pollution levels across the country, especially in typically smoggy cities, have fallen to dramatic lows.
Dramatic decrease
In Delhi’s metropolitan area, pollution levels have dropped most dramatically; NO2 levels from March 25 (the day quarantine began) to May 2 have averaged 90 µmol/m2 compared to 162 µmol/m2 from March 1 to March 24. In 2019, NO2 levels from March 25 to May 2 were also far above this year’s levels, averaging 158 µmol/m2.
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In Greater Mumbai and Navi Mumbai, a similar trend has been observed as NO2 levels from March 25 to May 2 averaged 77 µmol/m2 compared to 117 µmol/m2 from March 1 to March 24. In 2019, NO2 levels from March 25 to May 2 averaged 122 µmol/m2.
In nearly all other big Indian cities, similar drops in NO2 levels are apparent, highlighting the national scale of India’s lockdown.
The country-wide drop in NO2 emissions during this lockdown has significant immediate consequences. Exposure to high levels of NO2 has substantial detrimental effects on human health. Short-term exposure to high levels of NO2 can result in worsened coughing, aggravation of existing respiratory diseases (asthma), and hospitalisation, while longer-term exposure can lead to the development of asthma and increase one’s susceptibility to respiratory diseases. It makes sense, therefore, that experts are finding significant links between long-term exposure to high levels of air pollution and increased Covid-19 death rates.
Many researchers have hypothesised that the drop in air pollution levels may currently be saving a significant amount of lives, not only by reducing individuals’ susceptibility to Covid-19, but also by preventing some of the world’s seven million annual deaths due to air pollution exposure. Still, the dangerously high levels of NO2 in many urban areas before Covid-19 has likely resulted in far more virus deaths compared to the lives saved by this current drop in emissions. The pandemic and the subsequent decreases in air pollution levels due to the quarantine have illuminated a severe issue regarding ongoing high levels of air pollution.
Explanation:
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