What was your most important finding?
‘There were two, actually. I wanted to make a survey of the effects of human activity on the Oldebroek heath in Gelderland province. To do that, I took water samples from a soil depth of 30 centimetres at regular intervals and compared them with samples that colleagues have taken over the past ten years. They showed that the soil pH has dropped from 4.50 to 3.85. Though in principle this may be due to natural causes, the speed at which it has happened here is notable. The acidification of the soil is directly related to the volume of acid rain. In other words, the concentration of acidifying substances in the rain is still far too high.’
What was your other conclusion?
‘That dry periods neutralise this acidification of the soil to some extent. We discovered this by stretching sheets out over the heath to keep off the rain. It’s also interesting to find out about the effects of drought as periods of drought are becoming more frequent through climate change. In the soil you have substances known as cations. They convert acidic substances and thus neutralise the soil. Rain washes cations out. But when it’s dry, more cations remain and acidification tapers off. Acidification is harmful to heather and other plants as well. In Europe, the acid rain caused by nitrogen emissions from agricultural and industrial production has been decreasing for many years, but my research shows that we’re not at all out of the woods yet. Nitrogen emissions still need to come down more.’
You are in Australia now. Are you doing a follow-up study there?
‘No, I’ve got a new job here, with BP. I’m from Australia originally. I started off as a soil scientist, but I’d been working as a consultant in Brisbane before going to the Netherlands. My husband had been offered a two-year job at Schiphol and I went with him to Amsterdam. I took a voluntary position at IBED as a research assistant to Albert Tietema. A few months later, I got asked for this doctoral research project. My supervisor, Albert Tietema, will now be continuing the project. It’s actually part of a European research programme, so other universities are still conducting this research as well.’
How would you sum up your time as a doctoral researcher?
‘It was a fantastic period. I had a huge amount of freedom. Working as a consultant, I had to log every quarter hour but as a doctoral researcher, I could simply set aside a week to try something new. I also liked the Netherlands. The only thing I never got used to was the climate. The winters were way too cold for me. It’s eight o’clock in the evening here in Brisbane and still a lovely 23 degrees Celsius. But Amsterdam was a great city to live in. We quickly made lots of friends and if you’ve gone out for a few drinks, you can just take the bike home, which made life so easy. Here in Brisbane that would be much too dangerous. There are almost no designated bike paths.’