Hangover from the past

Emily Collins – Conservation Student Intern

Have you ever passed a beck or a stream and wondered why it was occasionally bright orange? Perhaps you thought the rock was naturally that colour, or that it was stained with sheep’s urine, or simply that local artists thought it a marvellous place to wash out their yellow ochre paint palettes.

In fact, this ochre colouring comes from underground and is often associated with historic mining activity. When it is washed out of the rock, ‘ferrous’ iron reacts with oxygen and water and forms ‘ferric hydroxide’ particles which join to form a thick layer of sediment. This can often smother the riverbed, quickly turning the water into something resembling gone-off carrot soup.

North York Moors - historic mine entrance

Ferric hydroxide forming undergroundThe thick suffocating ochre deposits can have a detrimental effect on food sources in the vicinity and downstream for things like aquatic plants, algae and invertebrates. They find it difficult to survive because iron ochre creates a very acidic and oxygen-deficient environment which puts many species under a lot of stress.

“But who cares about invertebrates?” you say, “They’re tiny and disgusting- don’t you have anything more useful to spend your resources on?”

Jon Sullivan, Mayfly Nymph - from Flickr.comJon Sullivan, Midge larvae - from Flickr.comJon Beresford, Caddis Fly Larvae - from Flickr.com

Indeed, they are tiny and some of them do look quite disgusting, but they can also give us a valuable insight into the effect historic mine discharge is having on watercourses today throughout the National Park. If you carry out a kick-sample – where sediment is literally ‘kicked’ into a net – and identify the invertebrates caught within it, the number and proportion of species give quite an accurate indication of the water quality at that site. This information can be used to justify and target future attempts to improve water quality and therefore increase the overall biodiversity of the area.

“You go on about this ‘biodiversity’ malarkey but you haven’t explained what it is and what’s in it for me?”

Dipper - Mike Nicholas for NYMNPA

Well, do you remember that scene in The Lion King where Mufasa explains ‘the great circle of life’ to Simba? He says that “everything you see exists together in a delicate balance” and he’s right! We need bacteria to break down our waste pollutants, insects to pollinate our crops and birds to spread seed throughout the land. Plants stop erosion, control floods and absorb CO2, as well as providing habitats in which animals can live and breed.

Humans have been exploiting the land for thousands of years and although there are exceptions, we do tend to disrupt the careful balance of nature. In the instance of the historic mining industry, the haphazard closure of mines in the 19th and 20th centuries has led to all sorts of pollutants which continue to be flushed out of them. The build-up of these pollutants in river systems can have detrimental consequences for the species living in the wider catchment.

DSCF2548 (2)Over the next few months I am going to be working with students at the University of Hull to investigate the aquatic invertebrate communities at various sites which are thought to be affected by historic mine discharge. This will hopefully give us some idea of what’s in the water and how it is affecting local species and their habitats. This will help to determine plans for future remediation e.g. creating new wetland areas to hold the sediment as it emerges.

8 thoughts on “Hangover from the past

  1. The pollution of the beck that runs into Saltburn is a perfect example. Neglect over several decades caused almost total die back in the stream and its banks, not to mention the horrible color. Cost the Government loads of cash to clean it up – after they had spent a fortune on an investigation to find the cause (which could have been established by simply asking locals). Best of luck in your endeavors to care for our landscape and heritage.

  2. I very interesting read Emily. Do you ever wonder if in 100 or 200 years young people like yourself will be blogging about The Polution caused by a Potash mine, or by nucleaur waste dumped into void spaces under the moors. Or could they be blogging about a poisened water column caused by fracking in The National Park ?? Would love to hear your thoughts.

    Regards – Glenn (www.real-whitby.co.uk)

  3. There are relatively few instances of it coming from mine workings in this area.
    I’ve no idea why that is the main thrust of this blog post except that a green/activist/anti-industry position is now obligatory in any kind of environmental study, especially if a grant is required.

    More often it seeps out naturally from underground iron deposits on its own.
    Many parts of the North York Moors have problems with ochre rapidly blocking land drains.
    Also it should be pointed out that the orange material is not toxic but tends to simply smother the stream bed especially during drier periods with reduced flow.

    It is hard to imagine how water seeping through iron rich seams would not eventually emerge somewhere with it’s dissolved iron burden, regardless of historic mining.

  4. Nice blog, Emily. The aquatic invert photos are really good and your writing style is very accessible to non-specialists, which is an important skill for scientists.

  5. A very interesting project but rather than stopping short with a detailed fauna survey, suggested ways to harmlessly neutralise the problem would make a really worthwhile conclusion.

  6. Pingback: Hangover cure | The official blog for the North York Moors National Park

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