Beirut Analysis

Tania Ghosh

2nd October, 2020

Abstract

On 4 August 2020, a large amount of ammonium nitrate stored at the port of the city of Beirut, the capital of Lebanon, exploded, causing at least 181 deaths, 6,000 injuries. The scientists have been trying to decipher what caused such a huge blast.

 

Introduction

According to the BBC news, the disaster was preceded by a large fire at the Port of Beirut, on the city's northern Mediterranean coast. In videos posted on social media white smoke could be seen billowing from Warehouse 12, next to the port's huge grain silos.

Shortly after 18:00 (15:00 GMT), the roof of the warehouse caught alight and there was a large initial explosion, followed by a series of smaller blasts that some witnesses said sounded like fireworks going off.

About 30 seconds later, there was a colossal explosion that sent a mushroom cloud into the air and a supersonic blast wave radiating through the city.

 

The chemical involved

The Lebanese government sources eventually said it was 2,750 metric tons of ammonium nitrate, a chemical routinely used as an agricultural fertilizer and, when mixed with fuel oil, as a mining explosive. The stockpile had been sitting in a warehouse since 2014 when the ship that carried it into port was abandoned. As we all know, ammonium nitrate is made from The neutralization of 45 - 65% nitric acid with gaseous ammonia is accompanied by the release of 100 - 115 J per mole of ammonium nitrate. The material itself does not readily burn but will readily do so if contaminated by combustible material. Toxic oxides of nitrogen are produced during combustion.

 

The scientists' take on this matter

According to Suzzane Smith and Russel Ogle who investigated this explosion, they concluded that the explosion could be caused due to an external heat source. It’s stable under normal conditions, but things can be done to it that will cause it to misbehave. The main trigger is an external heat source. Depending on how to count it, there have been probably somewhere between 20 and 30 major catastrophic explosions with ammonium nitrate since it came on the scene as a commercial product in the 1920s. And fire is a frequent trigger. It’s the heat of the fire that warms up the ammonium nitrate that can become a problem. If it is heated by a large heat source like a fire, the ammonium nitrate will begin to decompose—and that decomposition can be mild and harmless, or it can be catastrophic.

 

The pieces of evidence on which the judgment is based on

The videos are the primary sources on which the verdict was made. The presence of a crater is another indication of the size of the explosion and what could potentially be involved. And the radii of damage could tell a lot about how big or small the explosion was. A thin, spherical white shape could be seen moving away from the explosion in the videos. What was actually seen was water vapor condensing out of the air, because of really low pressure right behind the high-pressure shock wave. And then you can see it disappears right away because it’s evaporating once the pressure equalizes. You can see the actual shock wave, so you know that it detonated—and only certain things can get you to a detonation.

 

The Shock Wave

According to the Scientific American’s statement on Ogle’s interview. A shock wave travels faster than the speed of sound, and that’s the hallmark of a detonation. There are two kinds of decomposition reactions that could be found in ammonium nitrate when it’s starting to build up enough pressure to cause damage. The first is called a deflagration. It’s a wave—literally a chemical reaction wave—that is traveling through the material slower than the speed of sound. As it continues to travel, it accelerates. And if it gets to the point where it hits the speed of sound, that’s what we call a detonation. A detonation yields far more damaging mechanisms against things such as structures and buildings.

 

The Pressure Wave

According to Wired, the wave that was seen was not a shock wave but a pressure wave. A shock wave goes from zero pressure to its absolute maximum pressure in literally zero seconds. The impact of a pressure wave is like hitting the ground after rolling down a steep cliff; the force of a shock wave is like hitting the ground after falling through the air and reaching terminal velocity. High explosives produce shock waves; low explosives, like ammonium nitrate, produce pressure waves, which have a bit of slope to their shape, a period of time over which the pressure increases more gradually. Shocks, because of their fascinating and complex physics, travel faster than the speed of sound, and they cause far more damage than pressure waves. The speed of sound in air is 343 meters per second. Based on the viewing angle and distinctive red chairs pictured in some of the later frames, He traced one of the Beirut videos posted by The Guardian to its filming location on the rooftop terrace of La Mezcaleria Rooftop Bar and measured it to be 885 meters from the center of the blast. From that vantage, the pressure wave can be seen neatly traveling from the center of the blast first to the point halfway between the end of the pier and the edge of the long, massive gray grain silo building, a distance of 151 meters, then to the end of the pier, 262 meters, then eventually to La Mezcaleria.

By measuring the times at which the pressure wave reaches these landmarks on the video, we know that, as it blazed down the pier, its rampage occurred at a speed of only 312 meters per second. That’s slow for a bomb. Then by the time the audible crash and mayhem reached the formerly peaceful and picturesque outdoor bar, it had slowed to at most 289 meters per second. The pressure wave, slower than the 343 meters per second speed of sound, caused destruction, horror, confusion, shattered glass, torn-apart flat surfaces, and disorientation for onlookers as their ears were subjected to the rapid pressure fluctuations. But a shock wave could have caused them to drop dead from lung trauma as they watched.

 

The Mushroom Cloud

Brian Castner, a weapons investigator for Amnesty International, completely ruled out the idea of a nuclear explosion taking place in the Beirut blast despite several people supporting this claim. According to him, the smoke plume from the warehouse was red. And so people have said, ‘Oh, this shows it’s ammonium nitrate’, Well, it’s consistent with ammonium nitrate (but) other chemicals burn red. So it’s one of those things that’s a confirmation but it’s not dispositive or unique”, he said. On his interview with Wired, he further said When there’s a detonation, what’s caused is a shockwave and that shockwave is the air pushing itself into itself, essentially, and it sets up a front—kind of like a storm front [although] this is obviously many, many, many times more than that. But as the air pushes into itself when the air is really humid, you can see the shockwave, and it forms that cloud”.

 

Forensics' take in the explosion

According to Doug Perovic, a professor at the University of Toronto's department of material science and engineering in the Faculty of Applied Science and Engineering, the shelf life of ammonium nitrate is about 6 months. If a large volume of ammonium nitrate is stored for years and allowed to absorb moisture in a humid environment, the ammonium nitrate granules/pellets agglomerate and deteriorate, which increases the explosive potential of the mass. Additionally, ammonium nitrate has to be protected from impurities such as flammable liquids, powdered metals, oils, and acids and salts. The fuel load and heat from the fire at the fireworks storage appear to have been large enough to detonate the ammonium nitrate pile. It is possible the initial fire could have been intentionally set by someone who was sufficiently knowledgeable of the sequence of events required to detonate a large mass of ammonium nitrate.


 

Conclusion

The Beirut blast has become a topic of plentiful discussions. The opinions of people vary regarding the subject of what caused the blast. But there is a lot of information that has yet to be uncovered by the scientists and they are working hard to collect pieces of evidence to date to come up with a constructive reason with evidence as to what caused this blast.

Reference

1. Bushwick, S. (2020, August 7). Beirut fire: Large blaze erupts in port a month after explosion. Retrieved September 13, 2020, from https://www.google.com/amp/s/www.bbc.com/news/amp/world-middle-east-54100251

 

2. Ibrahim, A. (2020, August 22). A new exodus from Lebanon after deadly Beirut blast. Retrieved September 13, 2020, from https://www.google.com/amp/s/www.aljazeera.com/amp/news/2020/08/mass-exodus-lebanon-deadly-beirut-blast-200821191208211.html

 

3. MacKenzie, L. (2020, August 06). Why the Beirut explosion caused a mushroom cloud. Retrieved September 13, 2020, from https://wired.me/science/why-the-beirut-explosion-caused-a-huge-mushroom-cloud/

 

4. Irving, T. (2020, August 10). U of T forensic engineering expert on what happens next in Beirut investigation. Retrieved September 13, 2020, from https://www.utoronto.ca/news/u-t-forensic-engineering-expert-what-happens-next-beirut-investigation

About the Author

Tania Ghosh, studies Biotechnology in St. Xavier's College Kolkata.