Luis Peralta, professor at the University of Lisbon’s physics department, and Carmen Oliveira, physics and chemistry teacher at Casquilhos High School in Barreiro near Lisbon, describe the ‘Environmental radiation’ project, in which students become actively and enthusiastically involved in science through easy and inexpensive experiments that highlight the thrilling world of invisible particles.
The ‘Environmental radiation’ project, which started in 2007, emphasises the importance of ionising radiation – radiation with enough energy to remove electrons from atoms or molecules – in daily life. It now involves students (aged 12-18) and teachers from 25 high and middle schools throughout Portugal and the Azores, who receive technical and logistical support from the physics departments at the universities of Lisbon and Beira Interior, and from the Laboratory of Instrumentation and Experimental Particle Physics. The idea for the project was born when students from several high schools visited Lisbon University for a few days in Summer 2006, and a first trip to uranium mines was organised for them.Teachers and students involved in the project are invited to conduct hands-on experiments and share their results on the project’s websitew1 (see graphs below) and during an annual one-day workshop hosted by one of the participating schools.
This includes a science fair where students present their results and share new ideas, and the best works are awarded symbolic prizes. At the end of this day, there is a ‘pros and cons’ debate between the students and guest scientists concerning radiation issues. This workshop is also an interesting social event, attracting the attention of newspapers and local radio stations.
The ‘Environmental radiation’ project also provides extracurricular activities. In 2008, students and teachers, accompanied by two geologists, visited the uranium mines near Nisa, a small town about 200 km north-east of Lisbon. This is one of several locations in Portugal where rocks with some degree of radioactivity can be collected. The students collected over 50 kg of rocks at the site, which were later used to perform experiments at school. There are several areas in Europe where such rocks can be collected, for example in the Czech Republic.
The project’s chosen topic may seem controversial, as we are dealing with radioactivity and young people, but all the samples we use have a low radioactive content and, in fact, this negative aspect can be transformed into a positive one, as this project enables students to develop a culture of protection and good practices that carry through to the way they deal with radioactivity in everyday life – for instance, in medical imaging. To that end, the project’s website has a dedicated forum where students are encouraged to debate radiation-related issues.
We come across natural radiation in a variety of situations. For instance, radiation caused by radon and the elements into which it decays represents around 50% of the total radiation that people are normally exposed to in Europe. In turn, radon itself forms naturally when uranium present in rocks, most commonly granite, decays. Radon gas leaks from the soil and through cracks in the walls, and accumulates in closed rooms such as cellars, or inside buildings near the ground floor, where its presence can be detected through simple experiments that students can perform at their own schools.
The experiments developed for this project can be performed using a minimum amount of inexpensive materials. Each of the participating schools was provided with a kit comprising a Geiger counter, irradiated seeds, X-ray dental film, and a plastic box with up to 2 kg of rocks collected at the uranium mines. The schools provided lab space, computers and the enthusiasm of students and teachers.
A wide range of experiments can be performed to introduce and explore radioactivity, with varying degrees of complexity. For instance, students can use Geiger counters to measure radiation levels in and around their schools, and create a local radiation map using GPS coordinates which they then feed into Google Earthw2. Other simple experiments using only a Geiger counter involve detecting radiation in salts used in food preparation, such as potassium chloride, and in natural rocks; in more complex experiments, students can place metal plates with different thicknesses and compositions (lead, aluminium) between radioactive material and the Geiger counter, to discover how radiation diminishes when it traverses metal.
Experiments developed by the ‘Environmental radiation’ project also include using a balloon to catch radioactive dust from a closed room: rub the balloon with a furry cloth to create static electricity which will attract the dust, hang it for 30 minutes in a room which is usually kept closed, deflate it and use a Geiger counter to measure the radiation it emits. Students can even re-enact Becquerel’s historic experiment that led to the discovery of radioactivity, in which radioactive rocks are placed on dental X-ray plates and developed to reveal the ‘auto X-ray’ they have created.
For detailed descriptions of all the experiments and a discussion forum on radioactivity (all in Portuguese), visit the project websitew1.
Using the protocol below, students can explore a commercial application of radioactivity. The experiment has been successfully performed by students aged 13-20, but is also suitable for younger students, if the evaluation (measurements and graphs) is adapted accordingly.
While the fact that ionising radiation damages DNA and other cellular structures poses a risk to humans, it can also be – and frequently is – used to our advantage. Ionising radiation is used to kill all microbes on surgical instruments, sterilising them, and it is also employed in a similar fashion to extend the shelf life of some foods, and even in agriculture, where it is used to eliminate parasites from plant seeds. In Portugal, seed irradiation is done for research purposes only, while in the USA, this is common practice. Of course, the latter could inflict radiation damage to the seeds themselves. However, plant seeds are generally more resistant to radiation than the micro-organisms that plague them, so it is a question of finding the right balance: the radiation to which the seeds are subjected must be strong enough to kill the parasites, but not so strong as to harm the seeds.
By tracking the development of plant seeds subjected to different amounts of radiation, students can observe the effects of radiation on plant germination and growth.
For this experiment, the ‘Environmental radiation’ project had their seeds irradiated at the University of Lisbon’s physics department and at a facility that sterilises surgical implements. You can contact similar institutions in your country to irradiate the seeds you need.
The organisers of the ‘Environmental radiation’ project are currently in contact with biologists and biology teachers in an effort to further expand this experiment to encompass a multidisciplinary approach, in which students may be able to observe the effects of radiation on the plants’ cells and genetic material. Interested teachers may contact the organisers through the forum on the project’s website.
This project was financed by Ciência Viva, the Portuguese National Agency for Scientific and Technological Culture, the Science and Innovation Program for 2010, and ERDF (European Regional Development Fund).
Luis Peralta is a professor in the physics department of Lisbon University. He obtained his PhD in 1991 working on a high-energy physics experiment at CERN, in the field of heavy-ion collisions. In recent years, he has been working on radiation physics applied to medicine and is now interested in environmental radon-related problems.
Carmen Oliveira is a physics and chemistry teacher at Casquilhos High School in Barreiro, near Lisbon. She obtained a master’s degree in physics in 1996, working on radioactivity and the environment. Currently, she is working towards a PhD in physics, developing ionising radiation detectors for primary and secondary schools.