Year of the Periodic Table - Vera He

  • Year: 3rd Year PhD
  • Supervisor: Professor Mathew Heal

Tell us about your PhD project

My PhD project focuses on understanding the air we breathe and its health impacts in cities. WHO reported 4.2 million deaths every year as a result of exposure to outdoor air pollution, and 91% of the world's population lives in places where air quality exceeds WHO guideline limits. This is an area which is relevant to all of us, particularly to most Chinese people. As a Chinese myself, I was motivated by a project called BeijingAirNow, initiated by a photographer from Beijing, he has taken an identical photo of the sky daily since 2013.

The influence of air pollution can be easily seen from pictures.  Looking at these pictures, you probably assume when skies turn blue, the air quality is good, but it is actually not true. Most of the air pollutants are invisible. One of the most well-known air pollutants, PM2.5 is too small to be seen. You can see from the picture that PM2.5 is much smaller than our hair! Not to mention that there are lots of gaseous pollutants in the air. So as a scientist, I am trying to understand air quality by modelling the concentrations of air pollutants. One of the example results is the concentration map of annual average NO2 concentration in Guangzhou for 2017. From this picture, you can easily see the places where the concentration is high and where it is relatively low and since the WHO guideline for annual NO2 concentration is 40 ug/m3, you can find the places are safe in Guangzhou and avoid places are above that concentration.

Pollution as it affects the human hair

Image from https://www.epa.gov/pm-pollution/particulate-matter-pm-basics

Nitrogen dioxide variation across Guangzhou

Which element is key to your research area and why?

Nitrogen. When two nitrogen atoms bond together, they form nitrogen gas (N2) and N2 makes up 78% of Earth’s atmosphere. When N2 meets oxygen (O2) in combustion process nitrogen combines with oxygen to form several different oxides. The main resultant chemicals are nitrogen monoxide (NO) and nitrogen dioxide (NO2). NO and NO2 are two kinds of gases and are referred as nitrogen oxides (NOx). NO can be oxidised by ozone (O3) or volatile organic compounds (VOCs) to form NO2 and NO2 is one of air pollutants regulated by WHO and my PhD project focus on modelling NO2 concentration in cities.

Describe your average day of PhD work here in the School of Chemistry

Because I am doing modelling work, so I spend most of time with computers. I use R to process most data and ArcGIS for spatial data like roads and buildings, to make maps or to prepare them in the correct formats as inputs for my models. I am a member of a research group  modelling and measuring atmospheric composition and air quality at Edinburgh (MACAQUE) and we have regular group meeting so I can learn what other PhDs’ work within the group.

What’s your favourite chemical element?

Oxygen. It is the third-most abundant element and is crucial to our body. We cannot live without inhaling oxygen gas (O2). Three oxygen atoms form another gas, called ozone (O3). O3 in the stratosphere (between 16-48 km above the Earth’s surface) absorbs UV light from the Sun which can protect us.  Different from stratospheric O3, ground-level O3 is harmful to us. It is not only irritable to our respiratory system, but also has negative impacts on crops. The different roles of O2 and O3 in our lives make oxygen a fascinating element.

The three bands of the upper atmosphere surrounding the Earth

Image from https://www.scienceabc.com/wp-content/uploads/2018/01/Ozon-layers.jpg

What's your favourite chemical reaction?

I am very interested in a series of reactions describing the chemical coupling of NO, NO2, and O3.

NO2+hv →NO+O

O+O2O3+M

O3+NO→NO2+O2

M represents a molecule that stabilizes the O3 molecule formed. These reactions are key to modelling NO2 and O3 concentration in cities during the day. They can also explain a phenomenon that O3 concentration is higher at rural area, where NO2 concentration is low,  than its concentration at city centre (Clapp and Jenkin, 2001).