Plastic in caves (split from Solution for retaining a scree slope)

[Mr Dinwiddy]

Am I the only one who feels uneasy about using plastic in digs? Whatever we take to stabilise and facilitate digs we are essentially leaving in caves. I am comfy if this is steel or wood- both biodegrade into compounds which I regard as inert and harmless in the cave or groundwater. Likewise with concrete, though I dislike major modifications of surface features with concrete.

But I worry about microplastics in the groundwaters or in karst aquifers. Most of these hard plastics do not biodegrade in any case they just fragment into smaller sized plastics which become more mobile in aquifers and eventually oceans. My pet hate is plastic sacks as even in the absence of UV, they seem to fragment.

Should we be finding materials which are environmentally harmless for stabilising digs? Like most I use cut down barrels for moving spoil but when they wear out I remove them. I am talking materials we know will remain in the cave environment for decades or longer. Any thoughts?

 

[Rob]

Not really sure i understand the logic behind your concern. There's not much more inert than structural plastics. In comparison rust from metals i'd guess is quite toxic to some organisms. And treated wood (which you'd need to use to make it last at all) will surely have "nasties" in. Although either in the scheme of the rate of decay will hopefully be totally negligible. People often put plastic in a naughty corner when actually they mean to put litter in that corner, most of which is made of plastic. The difference is key.

Surely the best solution for cave shoring is use materials that will last the longest. Strong plastics will often tick that box, especially things like those plastic boards posted by pwhole. Agree, plastic sandbags not so much, but it'll still be tens if not hundreds of years in the benign environment of most caves. And still better than hemp ones that wont last 2 years.

 

[paul]

It also makes you wonder how safe some old digs are where scaffolding was used to support large boulders and now have rusty old scaffold clips holding it all together as we crawl through or beneath.

 

[pwhole]

We did sink six metres of twinwall pipe into the entrance shaft too, and that's definitely plastic - but then it's designed to be underground, so we can't do much more really. The choice we had was a brief breakthrough followed by total re-collapse (possibly with someone buried alive), or repair it with the strongest and most durable materials we could obtain in the shortest possible time. We bought it too!

From our perspective, re-opening a site that's been blocked for fifty years and guaranteeing that it won't ever happen again was more beneficial than an eco-friendlier solution that wouldn't last more than a couple of years. Though I too have my doubts that the micro-plastic particles from our treatments woud be significant in this environment. There's still a large amount of oil working its way through Speedwell, presumably from the Eldon Quarry works in the 60s-80s, and that's of far more environmental concern to me than our trivial contribution. I've been down Leviathan before when it smelled like a garage forecourt.

 

[CJ]

Am I the only one who feels uneasy about using plastic in digs? Whatever we take to stabilise and facilitate digs we are essentially leaving in caves. I am comfy if this is steel or wood- both biodegrade into compounds which I regard as inert and harmless in the cave or groundwater. Likewise with concrete, though I dislike major modifications of surface features with concrete.

But I worry about microplastics in the groundwaters or in karst aquifers. Most of these hard plastics do not biodegrade in any case they just fragment into smaller sized plastics which become more mobile in aquifers and eventually oceans. My pet hate is plastic sacks as even in the absence of UV, they seem to fragment.

"Researchers in Sweden measured samples of DNA at hundreds of locations around the world, taken from both soil and water.

They found 30,000 enzymes in these DNA samples that have the potential to degrade 10 different types of commonly used plastic, including the widely-used polyethylene terephthalate (PET). 

What's more, there appears to be a higher concentration of plastic-eating microbes where there is more plastic waste for them to break down.

It's thought the soaring use of plastic for packaging over the last 70 years has given 'sufficient evolutionary time' for various microbes present in the environment to respond to these compounds. "
- https://www.dailymail.co.uk/sciencetech/article-10312425/Microbes-oceans-soils-evolving-eat-plastic-study-reveals.html

Remind me why you're NOT doing your part to further evolution? I say decorate your digs with PET bottles

Psst... I'm being facetious, I do get your point​

 

[Rob]

In a similar vein there is active research currently underway looking at seemingly unique bacteria found in Mulu caves that has been seen to degrade our (plastic) caving ropes very fast. The scientists involved seem very happy with the discoveries, although i'm a little concerned if i'm honest!!

Some of these sites are exceptionally remote so presumably not showing an evolutionary response to human induced plastic but actually a natural ability...

 

[SamT]

seemingly unique bacteria found in Mulu caves that has been seen to degrade our (plastic) caving ropes very fast.

Is it because they're actually acidic.. weren't some limestone caves in South America thought to be formed not by flowing water, but by sulphuric acid emitting bacteria.

 

[cap n chris]

seemingly unique bacteria found in Mulu caves that has been seen to degrade our (plastic) caving ropes very fast.

Is it because they're actually acidic.. weren't some limestone caves in South America thought to be formed not by flowing water, but by sulphuric acid emitting bacteria.

Cueva de Villa Luz, Mexico, if memory serves; Professor Diana Northrop was the primary figure - acidic snottite u-loops, also found in Movile Cave, Romania; there was a programme about it yonks back.

 

[Pitlamp]

Are these the snottites we had a discussion about on this forum, earlier this year? There were some very useful posts contributed to that.

Or are the sort of microbes that make caves different?

 

[cap n chris]

Are these the snottites we had a discussion about on this forum, earlier this year? There were some very useful posts contributed to that.

Or are the sort of microbes that make caves different?

Possibly. I'm insufficiently up to speed on the topic to have useful answers to the specific questions though.

 

[Maj]

.............. Like most I use cut down barrels for moving spoil but when they wear out I remove them. ......

If worried about micro plastics from degradation of shoring materials, are you not concerned about the plastic that wears away from the drag trays.
What do you then do with the old digging skips?
I have a reasonable stock of blue barrels (not black), when their life as digging skips is over I clean them, cut them into smaller pieces and put them in my recycling box for roadside collection (they won't take cut up black skips).

Maj.

 

[pwhole]

There's a certain dig I've seen that used hundreds and hundreds of Tesco carrier bags to contain and stack sediment - this is at the head of a SSSI river valley with a known underground drainage component. It looked pretty funny when I first saw it, but then all I've thought since is how well they'll stand up to the rigours of time. There's no way this can be dismantled now, so they'll be there until they disintegrate. There's no obvious water-flow, and the dig is pretty dry, so may be OK, but that worries me much more than decking planks.

 

[andrewmcleod]

There's a certain dig I've seen that used hundreds and hundreds of Tesco carrier bags to contain and stack sediment - this is at the head of a SSSI river valley with a known underground drainage component. It looked pretty funny when I first saw it, but then all I've thought since is how well they'll stand up to the rigours of time. There's no way this can be dismantled now, so they'll be there until they disintegrate. There's no obvious water-flow, and the dig is pretty dry, so may be OK, but that worries me much more than decking planks.

I don't know if it's still true, but Tesco carrier bags from about 5-10 years ago used to complete disintegrate into flakes in about 2/3 years in storage in a house.

 

[pwhole]

It's probably been about eight years since I saw the dig - although there's no UV light down there, which may play a part in slowing down the degradation.

 

[mikem]

Andrewmc, sounds like their biodegradable ones:
https://www.edie.net/amp-news/5/Tesco-makes-u-turn-on-biodegradable-plastic-bags/20622/

 

[Tseralo]

Id much rather people use things like plastic to shore up digs. There are already a few places that have been lost again or had to be retrofitted because the wooden shoring rotted I suspect in 30-40 years we will be seeing a lot of issues with the current generation of scaff rusting away. I can think of a few popular places in the peak with rather rusty scaff allready.

 

[2xw]

There's already plastics in caves, it comes in from terrestrial deposition. Plastic is not inert - it might be chemically but it still has physical effects as it bioaccumulated.

I wouldn't worry about it from a caving perspective as they're already in the air, the soil and the caves. You won't make much difference with bags and dig trays.

 

[Leclused]

If you want to avoid microplastics coming into cave then you should wear a cotton overall and a wooden helmet and no plastic/rubber boots, don't use cave ropes, tackels bags,... Because they all contain plastics and we rub with it against the walls of the cave.

So imho don't bother too much about using hard plastic materials in a dig.