I learned today … a bit about nanosilver pollution

OK, so this may not sound that interesting unless you are an environmental scientist, but hear me out – although I am going to save the best bit to last to keep you reading.

Silver is ubiquitous these days.  Although its antimicrobial properties have been harnessed for medicinal purposes for centuries, it has more recently been found in socks, shower heads and various medical consumables such as swabs.  Although, a recent study of silver containing textiles in Denmark found that a lot of the articles claiming to contain silver had no trace when tested in the lab (see Chemistry World July 2012) but I digress.

A lot of the ‘new’ silver products contain nano (aka very, very small) particles of silver and this is where the controversy has arisen.  There has been concern raised about the effect of nano particles on the environment and human health.  By their very nature of being incredibly small they can get to places that larger particles can’t reach and there is the potential that they may have different surface and chemical properties.   Studies have shown that, depending on the method used to incorporate the silver into the textile or article, there is a high chance of the nano silver being released into the environment, especially if for example it is put through a washing machine.

The problem with silver escaping into the environment is that the property that makes it so useful – the toxicity of silver ions released from an item – is the very thing that makes it an issue – it is toxic to all organisms depending on the concentration.

There is a worry that the nano silver would get into the water course and pollute and kill everything in its path (OK, that’s an exaggeration but you get the idea).  Not to mention that the sludge from sewage works is often spread on fields.  However, there is a chance that this fear is unfounded.  Firstly, it appears that the toxicity of the nano silver is due to the fact that, just like other forms of silver used in medicine since whenever, it is the fact that it is Silver and releases silver ions that causes the toxicity.  The tiny-ness of the particles doesn’t make a difference to the toxicity.

Secondly, it is the free silver ions that are the problem.  In the water course the silver tends to combine with sludge and forms silver sulphides – these are not soluble, so less of an issue.

Finally, when solid silver objects, such as silver spoons, are examined it appears that they release nano silver – so this is probably not as new an issue as previously thought.

However, I do have a cooler bit of knowledge that I learned today to share.  In order to test for soil pollution worms are used.  A clew (for that is the collective noun for a ball of worms) is put into a test chamber.  On the one side there is lovely unpolluted soil, on the other there is the potentially polluted soil.  Worms are so good at sensing when soil is bad that and should be avoided that they have their own ISO standard for determining the chemical quality of soil.

insect_worm_15-1669pxSo, what is the worms’ verdict.  When they are faced with soil contaminated with silver nitrate they won’t go near it and detect the silver straight away.  Put them in front of some soil with nano silver and they take their time deciding that it isn’t a good place to be and that it’s time to run away.  See, it was a fact worth waiting for.

Whilst the jury may still be out gathering evidence as to the environmental and health impacts of nano particles, the verdict of the worms is definitely in.

I learned today … about fairy rings

which is quite a coincidence as we were discussing this very topic at the weekend, except at that point I didn’t realise what they were.  If you see a circle (or circles) of lush grass or indeed dead grass, then that is a fairy ring.

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These are caused by fungus growing underground – later in the year you might see the fruiting bodies, aka mushrooms.  If the grass is much greener and thicker that’s because the mycelium (the underground bit equivalent to plant roots) is adding nutrients, if it is dead grass then the the fungus is damaging the plant roots.  Each fairy ring is caused by a single fungus.

The rings are thought to start from a single spore that grows outwards until it reaches a certain size (around a metre) after which they run out of nutrients in the centre and start to form a ring, with nutrients passed around the ring to the point where they are needed.  If the ring hits an obstacle such as stone the bit by the stone will die and the rest will grow around it.  However, if it hits a larger obstacle such as a path it will stop growing and die.  There were many reasons postulated for this, but it was discovered that the fungi are very polar and grow in one direction only, therefore if the is blocked they can’t grow anywhere else and therefore run out of nutrients.  If they run into another fairy ring they compete with each other and both die!  Despite this there are records of some fairy rings that are over 100 years old.  According to one article I read there is a fairy ring in France that’s 600m in diameter and thought to be over 700 years old.

Fairy rings are also found in woodlands where they are known as tethered fairy rings as the mycelium are attached to the tree roots.  The fungi gives the tree water and mineral nutrients such as nitrogen that it extracts from the soil and in return gets sugars from the tree.  The mycelium are often seen in borders where they look like a mould on things like bark chips.  In fact, fungi are one of natures great recyclers, being one of the few organisms that can break down lignin from trees due to the complex enzymes they contain.

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Although fungi are very diverse; there are around 5 million species worldwide compared with 400,000 plant species, in the UK there are about 60 species that form fairy rings.

As can be gathered from the name fairy ring, there is a lot of folklore associated worldwide with these mushroom manifestations, worryingly enough the legends seem to have continued into the twentieth century.  I won’t go into details, but suffice it to say it involves fairies and dancing and having to do all sorts of superstitious things such as running round the ring nine times with your cap on back to front if you find yourself in one of these rings.

I learned today … that Galen was green

galenNot in the literal sense, but I think that he was perhaps the first practitioner of sustainable healthcare.  Although Galen (AD130-210) is well known as the basis for much medicine up until the 16th Century when his work on anatomy and circulation were proved to be inaccurate by Vesalius (one of my all-time heroes after Robert Hooke) and Harvey, he perhaps should also be lauded as one of the earliest sustainability managers.  According to the historians on a recent R4 podcast Galen had perhaps one of the biggest recipe books for drugs and treatments, receiving recipes from across the Roman empire; most of these were plant based and some survive up to the present day.  Not only did he prescribe remedies based on diet and exercise, but he also realised the effect of stress and mental health on physical health.

I think that if he were alive today he would definitely think that prevention was better than cure!

I learned today … that a new type of bee has found its way to the UK

OK, two bee posts in two days, but this was the most interesting thing I learned today (apart from the fact that potassium permanganate is used to treat weeping skin blisters as a last resort) whilst listening to a Radio 4 podcast.

First seen in 2001 the Ivy Bee ( Colletes hederae )is slowly progressing up the British Isles as shown on the survey map.   These bees start to fly around the end of August and have around a six week flight window coinciding with the flowering period of ivy.  Although I haven’t seen one they apparently look like furry ginger wasps.

As with many solitary bees these dig a hole in the ground in which to lay their eggs.  One pair will have around 10 offspring with up to 18 in a  good year.  In order to make sure the larva can survive for 10 to 11 months underground they provision the chamber where the egg is laid with up to 3million grains of pollen and nectar – this takes about 6 trips for each chamber – quite a task if you only live for about three weeks!

Although these bees are doing well – there is  no need to worry – as with other bees, the males don’t sting and the females are very docile.  As they have recently evolved they don’t yet have any predators here that have evolved with them and, as they don’t appear to pose any threat to native insects, let’s hope that they continue to flourish.  I’ll be setting a reminder in my calendar to look for them next September.  Looking at photos of them that I have found around the inter web I am fairly hopeful that I might recognise one if I see it.  I have included a photo below from Wikipedia taken by Hectonichus – maybe ginger humbugs was a good description!

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Today I learned … that not all bees collect pollen on their legs.

I already knew about the existence of cuckoo bees.  These are bees that lay their eggs in the already provisioned nests of pollen collecting bees so that they don’t have to bother collecting pollen themselves.  This means that they don’t have the hairy pollen baskets on their legs.  This is one way of differentiating them from the hosts that they have evolved to mimic.  However, an interesting article by Mike Edwards in the excellent British Wildlife Magazine gave me an insight into different types of bees and why their efficiency at pollinating plants varies so much.

The standard belief is that there is a mutually beneficial relationship between plants and pollinators whereby plants provide nectar as a foodstuff for the pollinating insect. In turn the bee moves pollen from the male part of the flower to the female whilst collecting it to take back to the nest for their larvae.  This article revealed that this only occurs with certain species and that in many cases the plant is robbed!

bee or waspWhat I didn’t know before today is that some bees, such as this white faced bee, are almost hairless and eat the pollen and nectar they collect before flying back to the nest; therefore denying the flower its rightful pollination.

The best known bees are the honey bees and the bumble bees, however, I also learned today these are not very efficient pollinators.  In some cases these bees manage to get the nectar and avoid the reproductive parts of the flower and therefore don’t pollinate it at all.  However, even if they do collect the pollen in the baskets on their legs, they need to wet it with nectar so that it doesn’t fall out.  This means that the pollen isn’t readily transferred to the female part of the flower.  Honey and bumble bees are, in effect, pollen robbers!

Whilst googling cuckoo bees for this short article I also came across this cool picture on Wikipedia.  A cuckoo bee asleep, using its mandibles to hold on – what a fantastic shot!  Until today I didn’t realise that bees did this!

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