Challenging Habitat Blog

Who needs (blood) diamonds when nature sparkles in so many ways?

Without environmental devastation

…without exploitation

…and for free!

I’ve recently reported on the risk associated with recreational activities or working on an abandoned copper and arsenic mine in the Tamar Valley, UK. Read these posts at ‘Challenging Habitat‘ and ‘Arsenic Health Risk at UK World Heritage Site‘.

The research attracted news coverage in local papers and BBC Radio Devon and I made local stakeholders aware of it.

I am pleased to see that the landowner of this site has acted responsibly and barred access to arsenic contaminated spoil heaps for sport. As a result, the cycling club Gawton Gravity Hub, who manages access to the site for mountain biking has installed new signage reflecting this change and sturdy timber bars prevent accidental trespass of no-go zones. The most toxic downhill routes are now blocked.

Still, access to the most dangerous part of the site, the area around the ruins of the arsenic processing and refining facilities, is still permitted.

While display boards warning of toxicity and explaining the process of arsenic sublimation and condensation in the calciners and labyrinth are fading, the path once covered in imported ‘inert and clean’ gravel is contaminated with arsenic dust.

More concerning still, just one step distance off the path, the stone and brickwork of the labyrinth undergoes wetting and drying that brings ‘blooms’ of efflorescent salts that are rich in arsenic and highly toxic.

Would you encourage your children onto a playground you know is heavily contaminated with arsenic?

Most probably not!

But the public is encouraged to use the heavily arsenic contaminated grounds of Devon Great Consols mine near Plymouth (UK) for recreation: walking, riding, biking, picnicking, exploring…

You think that’s crazy? You may be in a minority!

In 2007, the Tamar Valley AONB were successful in attracting £7 million investment from the Heritage Lottery Fund, Europe, County Councils and others for the Mining Heritage Project. Works commenced with consultancy surveys and finished with the opening of 25 km of trails that allow the public to access some of the most contaminated land in the country.

Some of this money was spent on remediation and mitigation: shafts were fenced off and signs were installed (not barriers) that intended to prevent access into some of the most polluted parts of the site.

Today, a lovely video praises this site for its family-friendly atmosphere and shows people jogging and biking on highly polluted ground – oblivious of the dangers they are in.

What’s more: the land owner permits a mountain bike club to use one of the most contaminated mining waste heaps for downhill practice and competitions.

Time to get real:

Arsenic is a deadly poison: the dose necessary to kill a person is somewhere between 100 mg and 300 mg, or one tenth to roughly one third of one gram of inorganic arsenic.

Chronic poisoning, the type people around the world are exposed to as a result of contaminated water supplies and occupational exposure, leads to serious consequences, including cancers of many organs, skin diseases, abdominal pain and diarrhoea, confusion and memory loss, neonatal morbidity and mortality, lung diseases and disruption of endocrine and haematological systems (Ratnaike, 2003).

Is anybody doing something about this?

I’ve tried for over a decade for this contamination to be taken seriously with respect to environmental health. Now, we’ve published work relating to human health.

Here is what we found:

  • across the site, the enrichment with arsenic is 600 fold relative to the soil concentrations in the Tamar river catchment (based on median)
  • concentrations ranged from around 140 to 75000 microgram per gram (µg/g) of soil or dust (that’s 7.5% by weight)
  • health-based soil guidelines values developed by the Environment Agency of England and Wales are 179 µg/g for park-type soil and 640 µg/g for commercial land
  • ingestion simulation with gastro-intestinal fluids testing the biologically accessible concentration in soils showed that most samples exceeded the park-type soil level
  • of 98 measurements taken on publicly accessible trails and places on site, only one (1) showed arsenic concentrations suitable for parkland and only 13 were suitable for commercial activities
  • particles in all air samples taken along trails and mountain bike tracks exceeded the current European Directive annual average target value of 6 nanogram arsenic per meter cubed (ng/m3), in one case by more than 10 times
  • lung fluid simulation showed that target values for arsenic were exceeded in many samples, indicating that the biologically accessible concentrations were too high
  • the calculated Index Dose of Minimal Risk from ingestion and inhalation of arsenic is 0.302 microgram per kilogram of body weight per day (µg/kg bw /day) and it is estimated that children ingest around 100 mg soil
  • a child of 1-2 years old and weighing 9.8 kg visiting the sites for 6 hours may ingest 25 mg of soil containing on average 13000 µg/g arsenic would be exposed to more than 10 times (33 µg/kg bw /day) the Index Dose of Minimal Risk
  • the equivalent exposure is more than 7 times (2.3 µg/kg bw /day) the Index Dose of Minimal Risk

What does this mean?

  • arsenic concentrations at Devon Great Consols are sufficiently high to be a public health concern
  • frequent visits, or indeed working on site, could significantly increase one’s risk of chronic arsenic poisoning
  • activities that encourage airborne dust, such as mountain biking, riding and walking in dry conditions increase the risk of inhalation
  • deviating from permissive paths onto mine waste material that is not fenced off increases the risk to health
  • mitigation measures are urgently needed to protect the public and employees

What can be done?

In my own opinion, and not necessarily reflecting the opinions of my co-authors of the scientific paper, the site should be instantly closed the general public. However, more pragmatically, and as a minimum, leisure pursuits should be minimised to less contaminated trails, areas fenced off that are highly contaminated and comprehensive information signage installed. Furthermore, the contaminated car parking area and timber storage yard to the north of the site must be closed to protect workers and visitors. The public must be excluded from the area of highly contaminated remains of arsenic processing and refining installation (calciners and labyrinth). Mountain biking activities must be disallowed on mining waste.

More mid-term, and in the interest of re-opening the site, contaminated trails could be remediated by removing surface layers and replacing them with inert materials.

In addition, covering the mine waste to prevent water ingress, erosion and dispersal of contaminated material would be a long-term target to protect the site and surrounding farmland and dwellings. Large-scale engineering solutions are expensive, disruptive and not sympathetic to the mining heritage. Therefore, I would suggest a phyto-stabilisation approach through re-vegetation.

I can only hope that someone out there cares enough to make it happen!

If you want a little bit more of the back story – go to my post ‘Challenging Habitat‘ and follow the links in the introductory paragraph.


All detail stated here has been either linked to external sources or is referenced in the published scientific article:

Braungardt C, Chen X, Chester-Sterne D, Quinn JGA, Turner A (2020). Arsenic concentrations, distributions and bioaccessibilities at a UNESCO World Heritage Site (Devon Great Consols, Cornwall and West Devon Mining Landscape). Environmental Pollution 264.

This work is accessible free of charge until 5th July 2020 from the publisher at:

After that date, please contact me directly for an electronic copy at


View over Anna Maria waste heap from one of the trails at Devon Great Consols mine. Photo: C Braungardt, 2018.

Let me take you to an excursion to the origin of this blog: I started writing about my thoughts on mining and its legacy in the UK and beyond. I wrote about the soils contaminated by metal mining and how lichens and mosses start natural succession in the most challenging habitats. There were posts on the toxicity of legacy mine sites and their effect on the wider environment, especially rivers, as well as touched on social and health aspects of the industry.

Together with two colleagues1 and two MSc students2 at University of Plymouth, I have taken up this latter thread again with a scientific risk assessment for people who frequent legacy mine sites contaminated with arsenic and metals for recreation or work.

Specifically, our research focused on the mining complex of Devon Great Consols in the Tamar Valley Area of Oustanding Beauty (AONB), an area of 67 hectare that is part of the UNESCO World Heritage Site ‘Cornwall and West Devon Mining Landscape‘. The mining history of Devon Great Consols began in the 16th century and ended in 1985 and broke several records, including ‘largest sulfide lode in West England’, ‘largest copper producer’ in the 1850s and in the 1870s, ‘largest arsenic producer’ in the world.

The mine generated great wealth for its owners and shareholders (Stewart, 2013), which at the time, were not bound to undertake remediation upon mine closure. Yet ores below ground and great heaps of waste materials at surface remain rich in arsenic, copper, zinc, iron, tin, tungsten and a range of other metals. Sporadically, the mine was worked for arsenic, tin and tungsten up to the 1930s and the waste heaps were reworked for copper and tin in the 1940s and 1970s. The site remains heavily contaminated, as documented by many scientific publications by the British Geologic Survey and others.

The relatively recent disturbance by mining activities, car rallies (!) and mountain biking combined with the toxic nature of the material means that vast areas remain bare of vegetation. This leaves the toxic waste vulnerable to erosion by wind, rain and frost.

A substantial proportion of the 67 hectare site is less contaminated than the waste heaps and much of that is under woodland management. However, some of the work areas are close to or directly on land covered in mine waste. Moreover, the area has been opened up to the public for walking, biking, horse riding, learning and picnicking on and along a network of 25 km of trails, put in place by the Mining Heritage Project of the Tamar Valley AONB. Arsenic is still abundant on site and it is highly toxic and carcinogenic, as I detailed in a previous blog post and is a major chronic health concern in many areas of the world (e.g. Ratnaike, 2003; World Health Organisation)

The question is obvious: how safe is it today to work here or visit this place for recreation?

Our research investigated the risk to health associated with spending time at Devon Great Consols. We re-assessed general levels of contamination, what happens to arsenic in the human body when the waste material is ingested or inhaled.

We found that parts of the site accessible to the public greatly exceed soil guideline values for arsenic and that exposure of visitors and employees is greater than the dose of minimal risk to health. This led us to urge mining areas to be more thoroughly mitigated before being repurposed and opened to the public.

Our work has been published in the peer-reviewed scientific journal “Environmental Pollution“, which I have summarised for non-scientists in a related post: Arsenic Health Risk at UK World Heritage Site.


1 Dr Andrew Turner, Associate Professor in Environmental Science and
Mr Jamie Quinn, cartographer at the University of Plymouth, UK
2 Ms Xiaqing Chen and Mr Daniel Chester-Sterne, both graduates of MSc Environmental Consultancy at the University of Plymouth, UK


MSc students at the base of Anna Maria waste tip at Devon Great Consols mine, 2018. Image by C Braungardt.


Braungardt C, Chen X, Chester-Sterne D, Quinn JGA, Turner A (2020). Arsenic concentrations, distributions and bioaccessibilities at a UNESCO World Heritage Site (Devon Great Consols, Cornwall and West Devon Mining Landscape). Environmental Pollution 264. Accessible for free of charge from the publisher until 5th July 2020 at:
After that date, please contact me directly for an electronic copy at

Ratnaike RN (2003) Acute and chronic arsenic toxicity. Postgraduate Medical Journal 79:391-396. [link]

Stewart RJ (2013) Devon Great Consols. A Mine of Mines. The Trevithick Society, Camborne. Obtainable from The Trevithick Society [link]

Fior di Mandorla

‘Almond blossom’ cookies belong to the collection of great European pastries (Lebkuchen and Tarta de Santiago are among my favourites, too) that are gluten free and utterly delicious. Based on almonds, they have Arab background, making them even more multi-cultural, which is a bonus in my world.


  • 400 g ground almonds (freshly ground is best)
  • 150 g honey
  • 50 g sugar
  • 1 teaspoon ground cinnamon
  • zest of one lemon
  • ca. 2 egg whites
  • icing sugar for decoration


  • pre-heat the oven to 150°C
  • mix the ground almond, sugar, honey, cinnamon and lemon zest
  • add just enough egg white to make a firm paste – if you add too much it gets sticky and sloppy and difficult to work – you can always add a little more almond if that happens
  • knead it with your hands until you get the texture of damp sand, the mixture will be held together by the oil that is released by the almonds while kneading
  • use the volume of about a heaped tablespoon of mass to shape oblong cookies in the palm of your hands (about 5 cm long and 2 cm thick) and press a little thumb print into the middle
  • bake them on a greased baking tray for about 20 min, taking care that they don’t get browned – they should be slightly soft in the centre
  • dust them with icing sugar and serve (amaretto goes very well with them)

The inspiration for this recipe comes from Claudia Roden’s ‘The food of Italy’, 1989, Arrow Books, London.

For a change, something really positive here…

We are the business of inspiring young people to be curious and ask questions, to get into nature and experience the small and big wonders of it, to make sense of how the planet works and how we interact with it, to seek and find solutions for the mess we’ve made of it, and to feel empowered. In short: I teach environmental science together with colleagues of diverse expertise at the University of Plymouth, and we like to think that we are making an important difference, however small.

Pelican of London sailing off Plymouth, August 2019. (c) C Braungardt

Tall ship Pelican of London sailing off Plymouth, August 2019. (c) Charly Braungardt

In partnership with the charity Adventure under Sail, we’ve piloted an outreach initiative that makes a difference for teenagers: with ‘Sea the Future‘, we combine personal development through sail training with the exploration of nature through marine environmental science and simply being, now.

And nature rewarded us amply: a star-lit night, dolphins hunting, illuminated by bioluminescent dinoflagellates, they looked like ghosts in the water, leaving trails of silver as they swerved, leaped and dived. For some of the 20 teenagers, this was the first live encounter with dolphins, and for all of us it was special and unforgettable.

The week’s journey touched us in many ways and the direct experience of so much beauty (from tiny plankton to fish, birds and mammals) and so much evidence of our negative impact on the marine environment (from plastics and sewage to noise and over-fishing) inspired the young people to do more to protect the oceans…but that’s best heard in their own voices, summarised in Jamie’s video of our voyage by Shield Media Services.

Dolphin at the bows of Pelican

Dolphin in the bow wave of Pelican. (c) Charly Braungardt

And what better metaphor for the global community coming together to build a sustainable future, than working as a team on a ship, literally pulling on together on many ropes for one common purpose?

What we love, we are responsible to take care of !

Watch the video Jamie from Shield Media Service produced about this amazing adventure:

In 2008, the Environment Agency wrote “Abandoned mines are one of the most significant pollution threats in Britain” (EA, 2008). This pollution threat to fresh, ground and coastal waters arises from thousands of discharges of mine waters in England, Wales and Scotland carrying metals, such as cadmium, copper, iron, lead and zinc, as well as less common elements, such as thallium, arsenic and antimony. Metal pollution is not the only negative impact of mining in rivers, often minerals generate acid when they oxidise and this can lower the pH of water to levels far below the range of natural water courses (pH 5-8), with pH<4 observed in many mine waters, a significant number below pH 2, and some even exhibiting negative pH. As a result, an estimated 2858 km of river length in the UK are adversely impacted by abandoned metal mines, 981 km of which are located in the South West (EA, 2008). For example, every year the former mining centre around Calstock and Gunnislake contributes around 220 tonnes of iron, 62 tonnes of manganese, 14 tonnes of copper, 12 tonnes of zinc, 5 tonnes of nickel and 4.5 tonnes of arsenic to the contaminant load of the river Tamar (Cornwall/Devon, UK) (Mighanetara 2009).

This is a global issue. Growing population and increasing living standards demand more resource extraction. The detrimental impacts of mining on rivers and coastal waters are reported in the news, by non-governmental organisations and official records around the world: follow some links from South Africa, the USA, Colombia, Australia, China and Spain.

Mine waters can be very visible. For example, where iron-rich acid mine drainage emanates from an adit (a drainage channel leading out of underground mine workings),  the iron that oxidises and precipitates as ochre when the mine waters gets into contact with the air. There are numerous examples of this phenomenon and a particularly (eerily) beautiful example is the outflow of Blanchdown adit accumulating and dewatering over time in its precipiation dam in the Tamar Valley.

Blanchdown Adit

Blanchdown adit, the main drainage of Devon Great Consols mine in the Tamar Valley, UK. Photo (c) C Braungardt 2016.

Geevor mine, West Cornwall

Minerals precipitating from mineral-rich seepage on the rocks at Geevor mine in Cornwall. Photo (c) C Braungardt 2011.

In other places, ground water becomes enriched with salts as ores dissolve in old mine workings or mine waste piles. This may leave colourful traces on rocks as secondary minerals precipitate when the waters reach the surface. Examples are the rocks on the beach at Geevor Tin mine (Cornwall, UK) and the efflorescent salts observed on mine waste at Devon Great Consols mine (Devon, UK). Such salts, the product of wetting and drying cycles, are highly soluble and are easily washed into surface waters with rainfall.


Efflorescent salts on the surface of mine waste at Devon Great Consols mine (UK). Photo (c) C Braungardt, 2007.

But often, the contamination of rivers with elements, such as arsenic, zinc or thallium is not visible. Only investigations by scientists using sophisticated analytical techniques reveal the extent to which the environment is contaminated and what effects pollution has on plants, animals and ecosystems, as well as the risks to human health. But this will be the subject of future posts.


EA (2008) Abandoned Mines and the Water Environment. Science Project: SC030136-41. Environment Agency, Coal Authority and Environmental Protection Agency Scotland. [accessed 24/07/2016]

Mighanetara K, Braungardt CB, Rieuwerts JS, Azizi F (2009) Contaminant fluxes from point and diffuse sources from abandoned mines in the River Tamar catchment, UK. Journal of Geochemical Exploration 100, 116-124.

Featured image: River in southern Sardinia polluted by the mining industry. Photo (c) C Braungardt 2007.

General Reading

Stewart RJ (2013) Devon Great Consols. A Mine of Mines. The Trevithick Society, Camborne. Obtainable from The Trevithick Society [link]

Poldark‘, the popular BBC series uses the Cornish mining legacy as a backdrop and you might have come across its relics on a coastal walk or moorland walk. Neither the picturesque views of landscape and sea, nor the glamour, heroism and romance helps us to understand the full story of thousands of years of metal mining history in Britain. From pre-Roman Britain through the Industrial Revolution to supplying today’s high-tech industry, mining has been driven by the pursuit of wealth and power at the expense of the welfare of untold numbers of individuals and to the detriment of the environment.

I often wonder how many people died an untimely death while on a poor wage during the height of arsenic mining in the latter quarter of the 19th and early 20th century in the Tamar Valley (Devon/Cornwall, UK), from where half the world’s arsenic originated at the time (Stewart, 2013). Arsenic poisoning resulted from poor working conditions while working the mines, processing the ore and refining the product. In addition, the rural population living near the mines was exposed to contaminated dust, fumes and water. Although I can’t find reference to it, I guess the health of agricultural workers in the US, many of whom were slaves, spreading arsenic pesticides on the cotton fields (see ‘Toxic’ Places) and orchards may have also been affected.

the 20th century, fatalities associated directly with the extractive industries have fallen considerably as safety in mining is taken more seriously and advances in robotics take the human element out of the more dangerous working environments. Still, some 12000 annual fatalities in mines around the world (BBC, 2010) are part of the price we pay for consumer goods containing mined resources, from paper (china clay) to energy (e.g. oil, uranium) to electronic gadgets (…where do I start: iron, silicate, gold, rare earth elements, copper, oil… ).



BBC News (2010) The dangers of mining around the world. By Olivia Lang 14 October 2010. [accessed 22/10/2017]

Stewart RJ (2013) Devon Great Consols. A Mine of Mines. The Trevithick Society, Camborne. Obtainable from The Trevithick Society [link]

Image: Hemerdon tungsten mine operated by Wolf Minerals in Devon, UK. Photo (c) C Braungardt, 2017.

Metal mine waste tailings dam in Nova Scotia, Canada

Metal mine waste tailings dam in Nova Scotia, Canada. Photo C Braungardt 2010

Following on from writing about mining waste as a challenging habitat for plants (see ‘First Arrivals‘), I want to provide you with the means to make sense of the contamination present in the historic metal mining landscape in Southwest England (and by analogy, in similar settings elsewhere). Nearly 700 sites in England are considered contaminated with metals (DEFRA, 2009) and in the northern England alone, 12000 km2 of river catchment soils and sediments are directly affected by historic metal mining, with similar areas in the Cornwall and mid-Wales (EA, 2008). Here, I will try to answer the questions why (is it there ?), how much (of it?) and by placing numerical information into everyday context. .  Read More



Encrusting and branching lichens on granite on the Cornish coast. Photo C Braungardt 2009

If epiphytes were people, we would call them clever strategists. I guess this holds true for any organism that manages to occupy a hostile corner, but I am fascinated by life forms that grow on toxic substrates. In this context, epiphytes (or air plants) are the pioneers that prepare the terrain for the arrival of other organisms.
Read More


Mine waste and woodland in Cornwall, UK. Photo C Braungardt 2009

What makes plants thrive? The obvious answer is light, water and ‘good soil’. Light is not likely to be a limiting factor on most mine sites, as there is little growing that could provide too much shade. However, water can be an issue and that brings us to the concept of ‘good soil’.

So what is a ‘good soil’? It contains a mixture of humus (more than 5 %) and mineral particles (ca. 45 %) of different sizes, so that it has a good water retention capacity without making it water-logged, it is rich in major nutrients (nitrate, phosphate, potassium) and contains micro-nutrients within a concentration range that is somewhere between deficient and toxic, i.e. just right. Its acidity is modest and into its texture, plants can anchor their roots. Soil also contains air (ca. 25 %) and water.

A key component of fertile soil is humus that gives surface soils their dark colour and also can be found in well-tended compost heaps. Humus is defined by Oxford Dictionaries as ‘The organic component of soil, formed by the decomposition of leaves and other plant material by soil micro-organisms’.

Humus provides minerals and nutrients that are readily available for plants and is important for retaining water and nutrients in soils.   Read More

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