3 ms·

So... to drop the PM2.5 amount by 15%, this tower must be removing many many tons of particulate matter every day. How is it removed from the filters they speak

by jhugg 9y ago

So... to drop the PM2.5 amount by 15%, this tower must be removing many many tons of particulate matter every day. How is it removed from the filters they speak of? How expensive is that to do? I have some questions about the practicality. On the other hand, I wonder if anyone's ever built a 100m placebo before. It could be a really interesting university study on the placebo effect in disguise.

lawlessone 9y ago
>I wonder if anyone's ever built a 100m placebo before. It could be a really interesting university study on the placebo effect in disguise. See the protests that erupt over mobile(Cell) phone towers. People claiming towers that weren't even on made them sick etc. https://idle.slashdot.org/story/10/01/15/1516245/tower-switch-off-embarrasses-electrosensitives https://idle.slashdot.org/story/10/01/15/1516245/tower-switc...
LeifCarrotson 9y ago
> many many tons of particulate matter every day Let's do the math. Guidelines state that the limit on PM2.5 particulates is approximately 10 micrograms per cubic meter for an annual average. Xian, where the tower was installed, is currently (http://aqicn.org/city/xian/ http://aqicn.org/city/xian/) under 231 ug/m^3 of pollution. The tower is supposed to process 10 million cubic meters of air per day. 10^7 m^3 x 231 x 10^-6 g/m^3 x 10^-3 g/kg x 0.15 = 231 x 0.15 x 10^-2 => 0.34 kg of particulate contamination removed per day. Not many tons. But someone check my math, please - that seems impossibly low, unless combustion is cleaner and generates lower quantities of PM2.5 particulates than I'm imagining. I did assume that it only removes PM2.5 contaminants, ignoring larger dust particles and PM10 pollution. Let's also check the amount of air it should be processing. It's about 100 meters tall, and intended to cover 10 square kilometers. We'll conservatively assume that this volume represents the total quantity of air it needs to process. Ihe volume is: 10 km^2 x 10^3 m/km x 10^3 m/km x 10 ^ 2 m = 10^8 m^3 or 100 million cubic meters, so it's intended to process one tenth of that volume per day. The math still seems low. Micrograms per cubic meter are hard to intuit.
- OskarS 9y ago
  Using your numbers, I get the same thing: http://www.wolframalpha.com/input/?i=(10,000,000+m3)+*+(0.15+*+231+micrograms%2Fm%5E3) http://www.wolframalpha.com/input/?i=(10,000,000+m3)+*+(0.15... The microgram is a very small unit :) I mean, a gram is already pretty dinky, a millionth of it is even tinier! The whole point of these particles is that they're miniscule and can pass through tissue other particles can't, so maybe it's not so surprising that it's not a massive amount when you pile them up.
- jhugg 9y ago
  That's really interesting. Maybe the pm2.5 is less visible than the PM10, but maybe I'm just way way off. As for the volume of air, I'm most curious where the 15% measurement was taken and how consistent it was. How far from the tower? How many different places were measured? How many days are in the sample? What's the P-Value? But still, thanks. Makes this interesting to think about.
  - OskarS 9y ago
    I think PM10 rates are in similar orders of magnitude, in the "micrograms per cubic meter" range, so i don't think it would be that different. Maybe an order of magnitude larger, but not much more. I agree, this is very surprising. Before I saw LeifCarrotson's calculation, I would have thought "tons" was the right unit as well. There's so much polluted air, you'd think that it would add up to some significant amount of matter, but apparently not.
    - staplers 9y ago
      Puts into perspective how much PM burning coal puts into the atmosphere.. EDIT: In 2016, the United States burned roughly 728 million tons of coal, enough to fill a typical railroad car every 4 seconds
    - jhugg 9y ago
      Well, 10km^2 is pretty tiny in a country the size of China, and I'm not sure how high up the pollution goes (higher than buildings but lower than planes). So it's still a lot of pollution, just much less actual mass than I would have guessed.

by jhugg 9y ago

lawlessone 9y ago

>I wonder if anyone's ever built a 100m placebo before. It could be a really interesting university study on the placebo effect in disguise. See the protests that erupt over mobile(Cell) phone towers. People claiming towers that weren't even on made them sick etc. https://idle.slashdot.org/story/10/01/15/1516245/tower-switch-off-embarrasses-electrosensitives https://idle.slashdot.org/story/10/01/15/1516245/tower-switc...

LeifCarrotson 9y ago

> many many tons of particulate matter every day Let's do the math. Guidelines state that the limit on PM2.5 particulates is approximately 10 micrograms per cubic meter for an annual average. Xian, where the tower was installed, is currently (http://aqicn.org/city/xian/ http://aqicn.org/city/xian/) under 231 ug/m^3 of pollution. The tower is supposed to process 10 million cubic meters of air per day. 10^7 m^3 x 231 x 10^-6 g/m^3 x 10^-3 g/kg x 0.15 = 231 x 0.15 x 10^-2 => 0.34 kg of particulate contamination removed per day. Not many tons. But someone check my math, please - that seems impossibly low, unless combustion is cleaner and generates lower quantities of PM2.5 particulates than I'm imagining. I did assume that it only removes PM2.5 contaminants, ignoring larger dust particles and PM10 pollution. Let's also check the amount of air it should be processing. It's about 100 meters tall, and intended to cover 10 square kilometers. We'll conservatively assume that this volume represents the total quantity of air it needs to process. Ihe volume is: 10 km^2 x 10^3 m/km x 10^3 m/km x 10 ^ 2 m = 10^8 m^3 or 100 million cubic meters, so it's intended to process one tenth of that volume per day. The math still seems low. Micrograms per cubic meter are hard to intuit.

OskarS 9y ago
Using your numbers, I get the same thing: http://www.wolframalpha.com/input/?i=(10,000,000+m3)+*+(0.15+*+231+micrograms%2Fm%5E3) http://www.wolframalpha.com/input/?i=(10,000,000+m3)+*+(0.15... The microgram is a very small unit :) I mean, a gram is already pretty dinky, a millionth of it is even tinier! The whole point of these particles is that they're miniscule and can pass through tissue other particles can't, so maybe it's not so surprising that it's not a massive amount when you pile them up.
jhugg 9y ago
That's really interesting. Maybe the pm2.5 is less visible than the PM10, but maybe I'm just way way off. As for the volume of air, I'm most curious where the 15% measurement was taken and how consistent it was. How far from the tower? How many different places were measured? How many days are in the sample? What's the P-Value? But still, thanks. Makes this interesting to think about.
- OskarS 9y ago
  I think PM10 rates are in similar orders of magnitude, in the "micrograms per cubic meter" range, so i don't think it would be that different. Maybe an order of magnitude larger, but not much more. I agree, this is very surprising. Before I saw LeifCarrotson's calculation, I would have thought "tons" was the right unit as well. There's so much polluted air, you'd think that it would add up to some significant amount of matter, but apparently not.
  - staplers 9y ago
    Puts into perspective how much PM burning coal puts into the atmosphere.. EDIT: In 2016, the United States burned roughly 728 million tons of coal, enough to fill a typical railroad car every 4 seconds
  - jhugg 9y ago
    Well, 10km^2 is pretty tiny in a country the size of China, and I'm not sure how high up the pollution goes (higher than buildings but lower than planes). So it's still a lot of pollution, just much less actual mass than I would have guessed.