Transition to zero pollution

By Albert Fabregas Flavia, a member of the Transition to Zero Pollution cohort.

According to a recent UN report, the world’s population is expected to rise from 7.7 billion to 9.7 billion by 2050 and reach 11 billion by 2100. Such an increase in population will inevitably lead to a proportional increase in the demand for food. Producing enough food to satisfy the needs of this growing population (and doing so sustainably) is, therefore, a pressing global challenge.

Currently, staple food production relies heavily on the use of synthetic nitrogen fertilisers. However, considerable amounts of synthetic nitrogen are lost to the environment in the form of nitrate leaching or as ammonia and nitrous oxide emissions, causing air and water pollution across the globe and contributing to global warming.

Interestingly, a few soil-dwelling bacteria have long been known to be capable of converting the nitrogen in the atmosphere into nitrogen fertiliser. Using these bacteria as bio-fertilisers has therefore been proposed as a way to reduce agriculture’s harmful over dependence on synthetic nitrogen fertilisers. Yet, the process for converting atmospheric nitrogen into fertiliser is highly demanding for the bacteria and is likely to result in a severe “fitness cost” (that is, a negative impact on the bacteria’s ability to grow and replicate and therefore its viability as an eco alternative), preventing the potential use of these bacteria as bio-fertilisers in agriculture.

As part of Imperial’s commitment towards a zero-pollution future, our project we will be taking an innovative approach to tackling the bacterial fitness cost associated with synthesising nitrogen fertiliser from the air. Because, to paraphrase Bob Dylan, we think the answer to the question of how to feed the world sustainably might well be “blowing in the wind”.

Read PhD Insights: Finding new ways to feed the world in full

By Marcus Annegarn, member of the Transition to Zero Pollution cohort of PhD students

The title of my project is ‘Understanding the electronic and physical structure of particulate matter through theory and experiment’, and its aim is to help experimentalists detect and analyse particulate matter in London’s air.

What is particulate matter?

Particulate matter (or PM for short) are microscopic particles that exist in the air that we breathe. They can consist of a wide range of materials and across many shapes and sizes. They are often categorised by their size.

For example, PM10 is used to denote particles which are less than 10 microns in size and PM2.5 denotes particles that are less than 2.5 microns in size.  For reference, a human hair is about 180 microns in width.

So what’s the big deal? Short answer: Your lungs! Exposure to PM has been linked to both minor and severe health risks. This can result in short term affects such as a runny nose, coughing and shortness of breath.  Prolonged exposure has been linked to increased mortality and prevalence of respiratory diseases, particularly amongst at risk groups such as children, the elderly, and those with pre-existing conditions such as asthma.

The smaller particles are believed to be more dangerous as they can penetrate deep into your lungs, even so far as into the membranes where oxygen is passed into your blood. The smaller particles also have a large surface area to volume ratio and more surface area allows for more harmful interactions with your lungs; for example, it is believed that small metallic particles can promote oxidation and thus severe damage to lung tissues.

However, the mechanism by which they affect our lungs is not yet fully understood. Nor which sizes and materials may be the most harmful. It is also hard to identify the exact size and composition of the particles.

Where does PM come from? 

PM can come from a wide range of sources. Outdoor sources include any sort of combustion engine as well as other vehicular sources such as brake pads, car tyres, roads, train tracks etc. Factories, open fires, and power plants can also contribute.

Indoor sources can come from fires, using gas heaters and stoves, cooking oil and even other household appliances such as air-conditioners.

How do we detect them? (Where I fit in)

The techniques often used to detect and analyse PM include X-ray absorption spectroscopy (XAS) and Electron Energy Loss Spectroscopy (EELS).

Both techniques result in a characteristic spectrum that gives information about the energy of the core electrons in the PM. From this information you can deduce which elements are present in the PM and in what configuration (i.e what material). The difficulty is that, to get this information, you need to match the spectra to a pre-existing spectrum of a known material.

My work involves using quantum chemistry software to try and predict spectra from theory so that we can use them to fingerprint and identify experimental spectra.

The hope is that this can lead to better understanding of what is out there and, in the future, which forms of PM are the most dangerous so that we can develop a targeted approach to mitigating the effect of air pollution on human health.

Read PhD Insights: Why Particulate Matter matters in full