@pasinduchamikara
Pasindu Chamikara
“Learning till the last breath and sharing the knowledge whenever it is feasible” being the philosophy of mine. I am Pasindu Chamikara from Sri Lanka.
https://globescience.net/
COVID-19 lockdowns significantly impacting global air qualityAGU contact: Lauren Lipuma, +1 (202) 777-7396, news@agu.org Contact information for the researchers: Jenny Stavrakou, Royal Belgian Institute for Space Aeronomy, Brussels, Belgium: +32 477 067 415 (GMT+2), jenny@aeronomy.be Guy Brasseur, Max Planck Institute for Meteorology, Hamburg, Germany: +49 171 287 6106 (GMT+2), brasseur@ucar.edu WASHINGTON—Levels of two major air pollutants have been drastically reduced since lockdowns began in response to the COVID-19 pandemic, but a secondary pollutant – ground-level ozone – has increased in China, according to new research. Two new studies in AGU’s journal Geophysical Research Letters find nitrogen dioxide pollution over northern China, Western Europe and the U.S. decreased by as much as 60 percent in early 2020 as compared to the same time last year. Nitrogen dioxide is a highly reactive gas produced during combustion that has many harmful effects on the lungs. The gas typically enters the atmosphere through emissions from vehicles, power plants, and industrial activities. In addition to nitrogen dioxide, one of the new studies finds particulate matter pollution (particles smaller than 2.5 microns) has decreased by 35 percent in northern China. Particulate matter is composed of solid particles and liquid droplets that are small enough to penetrate deep into the lungs and cause damage. The two new papers are part of an ongoing special collection of research in AGU journals related to the current pandemic. Such a significant drop in emissions is unprecedented since air quality monitoring from satellites began in the 1990s, said Jenny Stavrakou, an atmospheric scientist at the Royal Belgian Institute for Space Aeronomy in Brussels and co-author of one of the papers. The only other comparable events are short-term reductions in China’s emissions due to strict regulations during events like the 2008 Beijing Olympics. The improvements in air quality will likely be temporary, but the findings give scientists a glimpse into what air quality could be like in the future as emissions regulations become more stringent, according to the researchers. “Maybe this unintended experiment could be used to understand better the emission regulations,” Stavrakou said. “It is some positive news among a very tragic situation.” However, the drop in nitrogen dioxide pollution has caused an increase in surface ozone levels in China, according to one of the new studies. Ozone is a secondary pollutant formed when sunlight and high temperature catalyze chemical reactions in the lower atmosphere. Ozone is harmful to humans at ground-level, causing pulmonary and heart disease. In highly polluted areas, particularly in winter, surface ozone can be destroyed by nitrogen oxides, so ozone levels can increase when nitrogen dioxide pollution goes down. As a result, although air quality has largely improved in many regions, surface ozone can still be a problem, according to Guy Brasseur, an atmospheric scientist at the Max Planck Institute for Meteorology in Hamburg, Germany, and lead author of one of the new studies. “It means that by just reducing the [nitrogen dioxide] and the particles, you won't solve the ozone problem,” Brasseur said. Worldwide emissions Stavrakou and her colleagues used satellite measurements of air quality to estimate the changes in nitrogen dioxide pollution over the major epicenters of the outbreak: China, South Korea, Italy, Spain, France, Germany, Iran and the United States. They found that nitrogen dioxide pollution decreased by an average of 40 percent over Chinese cities and by 20 to 38 percent over Western Europe and the United States during the 2020 lockdown, as compared to the same time in 2019. However, the study found nitrogen dioxide pollution did not decrease over Iran, one of the earliest and hardest-hit countries. The authors suspect this is because complete lockdowns weren’t in place until late March and before that, stay-at-home orders were largely ignored. The authors did see a dip in emissions during the Iranian New Year holiday after March 20, but this dip is observed during the celebration every year. Air quality in China The second study looked at air quality changes in northern China where the virus was first reported and where lockdowns have been most strict. Brasseur analyzed levels of nitrogen dioxide and several other types of air pollution measured by 800 ground-level air quality monitoring stations in northern China. Brasseur and his colleague found particulate matter pollution decreased by an average of 35 percent and nitrogen dioxide decreased by an average of 60 percent after the lockdowns began on January 23. However, they found the average surface ozone concentration increased by a factor of 1.5-2 over the same time period. At ground level, ozone forms from complex reactions involving nitrogen dioxide and volatile organic compounds (VOCs), gases emitted by a variety of household and industrial products, but ozone levels can also be affected by weather conditions and other factors. ### AGU (www.agu.org) is an international association of more than 60,000 advocates and experts in Earth and space science. Through our initiatives, such as mentoring, professional development and awards, AGU members uphold and foster an inclusive and diverse scientific community. AGU also hosts numerous conferences, including the largest international Earth and space science meeting as well as serving as the leading publisher of the highest quality journals. Fundamental to our mission since our founding in 1919 is to live our values, which we do through our net zero energy building in Washington, D.C. and making the scientific discoveries and research accessible and engaging to all to help protect society and prepare global citizens for the challenges and opportunities ahead.
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APOLLO 4: Demonstration and operations of the first Saturn 5 rocket launch.APOLLO 4 LAUNCH, NOVEMBER 9, 1967, Kennedy Space Center "Bridge to Space" 1967 NASA INFO: Launch preparation[edit] The vehicle's on-pad, pre-launch tests and preparation practice started in September, and encountered several problems with propellant loading and various equipment failures. These pushed the launch into November, but provided valuable lessons learned on the new vehicle.[16] By this time, North American had been purchased by Rockwell Standard Corporation, so launch support was the first provided under the new name, North American Rockwell. On November 6, the 56½ hour countdown sequence began with propellant loading. In total there were 89 trailer-truck loads of LOX (liquid oxygen), 28 trailer loads of LH2 (liquid hydrogen), and 27 rail cars of RP-1 (refined kerosene). This time the problems encountered were few and minor.[17] Flight[edit] Launch occurred on November 9 at 7:00 am EST (12:00 pm UTC). Eight seconds before liftoff, the five F-1 engines ignited, sending tremendous amounts of noise across Kennedy Space Center. To protect from a possible explosion (see below), the launch pads at LC-39 were located more than three miles from the Vertical Assembly Building; still, the sound pressure was much stronger than expected and buffeted the VAB, Launch Control Center and press buildings. Ceiling tiles fell around news reporter Walter Cronkite, covering the launch for CBS News. Cronkite and producer Jeff Gralnick put their hands on the observation window in an effort to stop its powerful vibrations.[18] Cronkite later admitted he was "overwhelmed" by the power of the rocket and the emotion of the moment. His on-air description was delivered without his usual poise and reserve as he yelled above the launch noise into his microphone. ...our building's shaking here. Our building's shaking! Oh it's terrific, the building's shaking! This big blast window is shaking! We're holding it with our hands! Look at that rocket go into the clouds at 3000 feet!...you can see it...you can see it...oh the roar is terrific!... — Walter Cronkite, Broadcast of Apollo 4 launch[19] Much like with the Saturn I's maiden flight six years earlier, the fear of a low altitude launch failure, and especially a pad explosion, was high. Several NASA studies had been conducted to assess this scenario by studying previous such accidents (notably the March 1965 Atlas-Centaur disaster), but in all such cases, they involved launch vehicles less than half the size and fuel load of the Saturn V. Such an event would be a catastrophe beyond all proportions (the Soviet N-1 disaster of 1969 however provides a glimpse of what it might have looked like). Fortunately for all concerned, the largest rocket ever built lifted from LC-39A and performed perfectly through all stages of the flight. The launch placed the S-IVB and CSM into a nearly circular 100-nautical-mile (190 km) orbit, a nominal parking orbit that would be used on the actual lunar missions. After two orbits, the S-IVB's very first in-space re-ignition put the spacecraft into an elliptical orbit with an apogee of 9,297 nautical miles (17,218 km) and a perigee deliberately aimed 45.7 nautical miles (84.6 km) below the Earth's surface; this would ensure both a high-speed atmospheric reentry of the Command Module, and destruction after reentry of the S-IVB. Shortly after this burn, the CSM separated from the S-IVB and fired its Service Module engine to adjust the apogee to 9,769 nautical miles (18,092 km) and a perigee of −40 nautical miles (−74 km). After passing apogee, the Service Module engine fired again for 281 seconds to change the orbit to a hyperbolic trajectory, increasing re-entry speed to 36,545 feet per second (11,139 m/s), at an altitude of 400,000 feet (120 km) and a flight path angle of -6.93 degrees, simulating a return from the Moon.[1][20] The CM landed approximately 8.6 nautical miles (16 km) from the target landing site northwest of Midway Island in the North Pacific Ocean. Its descent was visible from the deck of the USS Bennington, the prime recovery ship.
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