Whilst everyone else on board is sampling sea water, I study the atmosphere, what tiny particles are being carried in the air and what particles are in rain water. My main research interests are to understand how tiny particles of iodine react in the air (it’s a chemical very similar to chlorine, which is what makes swimming pools smell). It’s important to study iodine in our atmosphere, as it reacts with light in a layer called the troposphere where it breaks down the ozone layer. This is important as ozone can help block UV radiation, so if ozone is broken down more UV radiation can reach the earth’s surface, which is a problem for us as it can cause skin cancer.
To study the atmosphere it’s important to be out of polluted air, this is why being in the middle of the Atlantic is great, but it also means I have to get right above the ship where no pollution, or tiny particles, will blow off the boat. Therefore on daily basis, I have to go up to the monkey island. This is the level above the bridge right on top of Discovery, it has the best view on board and there isn’t I better place to be on a sunny day. Unfortunately, because I really want wind and rain samples, this isn’t exactly what I’m looking for.
Chan on Monkey Island with his aerosol collector
On the monkey island I have two aerosol collectors and two rain funnels set up. These are for collecting air and rain water samples, the first set is for trace metals analysis (tiny particles of metal in the atmosphere) and the second one is for major ions (other chemicals such as iodine). The basic principle of an aerosol collector is to allow air to flow either through hitting or passing through filters for about 20-24 hours. By either being collected on or passing through a filter, I can then separate these coarse and fine particles in the air. I will then use these filters to understand the chemical composition of air. After the filters have been left in place for a day, I will collect them and freeze them to bring back to UEA for future analysis, it’s the same with the rain samples.
It’s fair to say sampling air might seem a little dull. There is nothing very exciting about collecting filters, and then freezing them, day after day for an entire 46 day cruise, well apart from the view! However, when we were around 15-20 degrees North, the colour of filters I was collecting completely changed. They went from the typical dark particles I usually collect to a yellowy-brown colour. Now again this might seem like a subtle difference, but for me it was quite exciting as it meant I was sampling Saharan dust! Having blown off the desert, many hundreds of miles away, it travels in the wind and I was sampling it in the middle of the Atlantic! It just goes to show the impact the sand, and any particles the sand carries, can have a large impact on the ocean waters, possibly affecting what can grow there.
An aerosol filter covered in Saharan dust
Now whilst you can’t really see what is carried in the wind, well not until it’s on my filters, collecting rain is much more visual. The nature of rain at the Tropics is really different from what I have experience back in the UK. This is because the strong sunshine and hot weather causes clouds to form from sea water evaporation. With the rain showers we experience here tending to be short, sharp and heavy downpours. Because showers come and go so quickly, it can make getting a clean, fresh sample really difficult. Getting to Monkey Island requires some climbing, and like its name sake I have to be pretty agile to get up above the bridge to get good samples. I must be the only person on board Discovery hoping for long rain showers and strong winds!
Heavy rain makes me feel like I am back at home, in Thailand, where the weather is hot and humid throughout the year, and we have heavy rain regularly. Pouring tropical rain like this can be problematic as it causes a lot of flooding problems in Thailand and South East Asia, especially recently. But for sampling the atmosphere it is ideal.