Wonderful wetlands

Oxford is built on a swamp.

The home insurers won’t let you forget that most of the houses are delicately balanced on a tiny strip of land just above the water level, like Noah on a beached ark.

When it rains heavily, the soils saturate and run onto the tarmac, creating rivers occupied by confused looking geese that stream down the streets. Adjacent fields take on the appearance of flooded paddy fields.

But believe it or not, these indomitable wetlands are crucial to the local environment, its habitats, ecosystems, and even the shape of the land. This is because of something called phytoremediation.

 

Swampland in Oxford. By Jpbowen via Wikipedia Commons.

Lifetime of a Plastic Bag

450 years into the future - that’s the agreed lifetime of a uniform piece of plastic like a bag. But who’s arguing? Man-made plastics have only been around for about 50 years: we don’t know for sure how long it takes a plastic bag to decompose: so where does this number come from?

A floating plastic bag. Like so many, it has ended up in the ocean. Image credit: Andrew (Flickr).

Plastic readily breaks down into smaller and smaller pieces (microplastics) under environmental conditions: it can now be found anywhere, a splash of colour amongst sand particles viewed beneath a microscope. But this isn’t the same as biodegradation, defined as the bacteria-driven chemical transformation of a material into other compounds.

Natural plastics do exist and do biodegrade: rubber and cellulose, for example. But these don’t make a good comparison with man-made plastics: cellulose is eaten by many animals, and enzymes and microorganisms exist in nature to catalyse its break down, which normally happens by about 6 months^[1]. There are some man-made plastic-eating bacteria, but these have only recently been discovered: how fast they act or what products the plastics are broken down into (and whether they are safe and useful) is still a mystery^[2].

Toxic Climate: how climate change changes pollution

When it comes to climate change, contaminated land is the forgotten risk.

Climate change leaves us worrying about quite a lot of things: tropical diseases, extreme weather events, extinctions... But we don’t tend to worry about pollution outbreaks. In DEFRA’s climate change risk assessment, it doesn’t even get a mention.

But is that because we’ve forgotten the risks, or because we don’t know?

Extreme weather may affect land safety, access and use. Image © Rowena Fletcher-Wood

Lots of land is “contaminated land”. This doesn’t mean it glows yellow in the dark or is a breeding site for mutant flesh-eating bacteria. Most land is contaminated by waste from agriculture, industry, energy or medicine, and that can be anything from fertilisers that cause algal overgrowths to pharmaceuticals that make male fish feminine^[1]. Humans like to concentrate chemicals to put them to use doing specific jobs. This is great when they’re where they’re supposed to be, but leftover chemicals or waste products are still relatively concentrated and can be poisonous or harmful.

Contaminants can also come from the land itself: like arsenic, which is rife in various rocks. Or radon, a radioactive gas found in granite, and especially Cornwall.

There are three main ways of dealing with chemicals in the environment:

1. Spread them out – diluting them more and more until they’re no longer at harmful concentrations
2. Concentrate them – and lock them up in a box or a landfill somewhere they can’t do any harm
Or 3. Change them. Chemical reactions can change the nature of some chemicals, such as pharmaceuticals, making potentially harmful things into harmless things.

These processes are called remediation.

Mysterious Mo

Why is stainless steel stainless?

Iron vs Steel

Steel is made from iron, but it’s not the same thing: steel is an alloy - iron doped with other elements to engineer new, useful properties. Some of these elements have been especially selected to provide certain properties, but not all metallurgy is that well understood: some elements have simply been stuck in and performed well - and we don’t know why.

100,000 Years Later

The problem of making future predictions about the destiny of long-lived nuclear waste.

What is nuclear waste?

Depending upon what you put into a nuclear power station and how you operate it, you get different products out. Most reactors use uranium dioxide fuel, UO₂, and over 90% of the “spent fuel” is still uranium compounds, with a little plutonium. Although it is called spent fuel, so much uranium still exists that it may be recycled to generate more electricity and remains hot for years. However, “ash” products that absorb neutrons and slow the reactions build up as the fuel operates, the rate that energy is produced drops and stops being efficient. Then the fuel will be replaced, useful uranium extracted and recycled and the rest disposed of.

Some kinds of reactors extract more energy and are more efficient, such as fast breeder reactors. These make products like plutonium-239 (Pu-239) that sustain the chain reaction - nuclei falling apart and giving off energy. When the rate plutonium-239 is produced is faster than it is used up, the reactor can get 60 times as much energy from the original uranium and more plutonium products result. However, there are no fast breeder reactors in the UK because plutonium-239 is one component used to make nuclear weapons - not something you want to be storing in large quantities. Plutonium-239 and other minor actinide products of nuclear power generation remain dangerous for over hundreds of thousands of years. Although the longer a radioactive material remains dangerous, the lower the danger (because they produce radioactivity more slowly), fresh spent fuel is so concentrated that standing unprotected before it would get you a lethal dose in seconds, and you would die of radiation sickness in days.

How can we store nuclear waste?

Location, Location, Location

Nuclear power and nuclear waste are sensitive public issues. Whilst the Finns are already building a geological disposal facility in Onkalo, in the UK we still haven’t decided what to do with our waste. Before the site can be chosen and built, a formal, scientific safety case must be completed, evidencing the likelihood that the containment facility will remain intact on a timescale of at least thousands of years. Learning from the “Yucca Mountain controversy”, where the state of Nevada legally opposed the construction of an American disposal facility on the grounds that they didn’t want to be lumbered with the country’s nuclear waste without consent, the UK government are waiting for volunteer communities to emerge before they can even start studying local geology in detail. Huge climate and geological changes, including at least one ice age, are predicted, which would totally change the landscape, the exact impacts of which could vary widely depending on where nuclear waste goes.

Nuclear waste is divided into three categories: High, Intermediate and Low Level Waste. High Level Waste is what's left after spent fuel is recycled to extract as many reusable uranium and plutonium fuel isotopes as possible. This waste is usually vitrified: transformed into a glass by fusing with borosilicates at high temperature. Intermediate and Low Level Wastes are non-fuel items (such as containers) that have been or may be been contaminated during normal operation of the nuclear power plant, and comprise the bulk of the waste. Image credit: Nevada Test Site Guide (public domain)

India's MOM seeks answers

In 2010 the Indian Space Research Organisation (ISRO) began a mission to send a spacecraft to orbit Mars – the Mars Orbiter Mission (MOM). Three years later they launched the craft and finally, on 24th September 2014 it reached its destination. The spacecraft’s primary objective is to test and develop the necessary technologies needed for interplanetary space travel - a technology which will allow India to plan future missions through the solar system and beyond. Its secondary objective, though, is scientific research. As the craft orbits the planet it will be collecting data about the planet’s atmosphere and surface.

The journey to Mars, though relatively short compared to a journey to other planets, is a complicated one; out of the 23 missions which have been launched to orbit Mars, only 10 have been fully successful. For India, this maiden voyage means the chance to explore the red planet whilst also developing their technological know-how. The whole mission has cost ISRO about $70 million - making it the cheapest vessel to enter Mars’ orbit since exploration of the planet began! For comparison, NASA had to pay a similar amount per seat to fly their own astronauts to the International Space Station in a Russian spacecraft. This is an incredible feat for technology and may lead to reduced costs for future missions to Mars.

An artist's impression of the Mars Orbiter Mission spacecraft orbiting Mars. The basic structure was based closely on ISRO’s first mission - Chandrayaan-1. Image credit: Nesnad, via Wikimedia Commons. (CC-BY-SA-3.0)

Mars is the outermost of the four rocky planets in our Solar System, and is also Earth’s neighbour. Despite having similar rocky compositions these two planets couldn’t be more different. The oceans, flora and fauna which are so prevalent on Earth are completely absent on Mars, and yet the two planets’ orbits are separated by a mere 54.6 million kilometres – a galactic stone’s throw away. Astronomers and planetary scientists have been studying the planet for a while now, and yet there is still so much we cannot decipher about the planet and its history.