'Trees filter the air'

[Simpo Two]

Or do they? I heard that phrase on the news, but wondered how they did it. Air enters via the stomata, and through the wonder of photosynthesis CO2 is converted to O2, but do trees really remove air pollution and if so by what mechanism?

[Beati Dogu]

I think it’s more that pollution particles gets trapped on the leaves and branches before the rain washes it away. Trees do give out pollutants like isoprene, but then so do we.

[dvs_dave]

Yes, they do, particularly Plane trees as they routinely shed their bark. Although the effect is marginal.

https://www.sciencefocus.com/planet-earth/do-londo...

[Simpo Two]

dvs_dave said:

Yes, they do, particularly Plane trees as they routinely shed their bark. Although the effect is marginal.

https://www.sciencefocus.com/planet-earth/do-londo...

Thanks; I know about plane trees, but they are the exception - most trees don't shed bark.

So I wondered if it was one of those pseudo-science soundbytes that sounds good but doesn't stand examination.

As for the BBC saying 'Plane trees do emit isoprene though, which combines with nitrous oxide in car exhaust emissions to produce harmful ozone' - do they? I can't find a reference to it.

Edited by Simpo Two on Wednesday 6th December 20:07

[welshjon81]

In essence, trees are composed primarily of carbon. Their mass is derived from the atmosphere, where they extract carbon from CO2 and subsequently release the oxygen component back into the air.

[Simpo Two]

welshjon81 said:

In essence, trees are composed primarily of carbon. Their mass is derived from the atmosphere, where they extract carbon from CO2 and subsequently release the oxygen component back into the air.

Indeed they do; once upon a time I could have drawn you a cross section of a chloroplast cell wall with all the proteins of photosynthesis in it and the accompanying biochemistry from CO2 to glucose. But the question here is whether they 'filter out' air pollution, and I remain unconvinced.

[Pistom]

I would have thought with all the wind they create when they move and fan the air, they'd be moving a fair amount of pollution about.

But physics wasn't my strong point.

[lufbramatt]

Possibly comes from a NASA study that found plants could remove chemicals like formaldehyde from the air under lab conditions. But I'm sure subsequent studies showed that to make any useful effect you'd need more plants than you could physically fit into the room.

[Cryssys]

There is limited evidence that certain houseplants can remove/absorb a range of pollutants in some circumstances :

https://neoplants.com/blog/air-purifying-plants

How beneficial this is remains open to question.

Further google searching, e.g. do plants remove pollutants reveals further evidence that they do however there real world effectiveness appears to be quite limited.

[bucksmanuk]

Pistom said:

I would have thought with all the wind they create when they move and fan the air.....
.

Sorry for the slow response – but my mum was convinced of this. I thought I had misheard her.
I am afraid she dropped down in my estimation that day….

[Kawasicki]

Trees pollute

https://www.insidescience.org/news/trees-may-becom...

[Simpo Two]

Kawasicki said:

Trees pollute

https://www.insidescience.org/news/trees-may-becom...

It's interesting, but too woolly; too many 'mights' and 'can be's'. And that seems to be a problem with science these days - too much extrapolation and too much headlining with little significant support. Perfect fodder for the media (and those with vested interests) to make mountains from molehills and spray stuff around that can effectively be false or at best misleading.

[Kawasicki]

Simpo Two said:

Kawasicki said:

Trees pollute

https://www.insidescience.org/news/trees-may-becom...

It's interesting, but too woolly; too many 'mights' and 'can be's'. And that seems to be a problem with science these days - too much extrapolation and too much headlining with little significant support. Perfect fodder for the media (and those with vested interests) to make mountains from molehills and spray stuff around that can effectively be false or at best misleading.

How dare you question peer reviewed science.

Denier!

“Those with vested interests“ is tantamount to admitting you believe in conspiracy theories. Bet you also believe the earth is flat.

[Simpo Two]

Kawasicki said:

Denier!

I was thinking about that word yesterday, which is inspired by the phrase 'holocaust denier'; ergo, a denier is in the same box as the Nazis and very bad. But there are other categories. As well as Denier I propose Accepter, Evangelist and Sucker; but it's best that fight stays on another thread

[Silvanus]

Trees don't really filter the air as such. They do however remove air pollution by capturing particulate matter on their leaves and bark with the absorption of some small levels gaseous pollutants through the leaf stomata. The pollutants on the tree surfaces are then either absorbed or later fixed into the soil bellow. They of course have the benefits already mentioned of absorbing carbon and releasing oxygen. Water absorption and soil stabilisation have big benefits too, by reducing runoff they can reduce the amount of chemicals and pollutants entering watercourses, riparian trees are particularly useful. They also have a cooling affect bringing down air ground, and water/river temperatures. Loads of other benefits too.

[ATG]

Think I read somewhere about particulates (dunno what size) concentration being reduced downwind of trees. Seems reasonable as (a) the trees provide a surface area on which the particulates can adhere and (b) they locally create turbulence that will slow the bulk air helping gravity "win" and also creating pockets of slow moving air in which particles will tend to congregate and may allow them to conglomerate into bigger particles, again helping gravity "win". Imperial do a lot of urban air quality research. Might be worth seeing if they've published anything. Feels like the kind of thing you could measure fairly easily if you could carpet an urban area in detectors. I guess it comes down to the cost of doing so.

From the university of anecdote, I can certainly attest that an urban privet hedge captures a huge amount of crap from the air. The foliage becomes absolutely filthy.

Edited by ATG on Friday 29th December 11:49

[Simpo Two]

Thanks to the genius of Amazon - how do they know? - this appeared in the 'stuff you might want' category...

https://www.amazon.co.uk/dp/B08X2V5K28

[Kawasicki]

Simpo Two said:

Thanks to the genius of Amazon - how do they know? - this appeared in the 'stuff you might want' category...

https://www.amazon.co.uk/dp/B08X2V5K28

The Amazon is actually a major source of methane, a very powerful greenhouse gas.

[Simpo Two]

Kawasicki said:

The Amazon is actually a major source of methane, a very powerful greenhouse gas.

Well that's OK, just trap it and burn it as fuel. The resultant CO2 is much less effective as a GG...

Therefore we need to burn more methane. Bring on the cows! And when there's an excess of cows, we can eat them, which is an excellent repurposing of organic matter