Mercury Detection using LED techniques: a feasibility study

Abstract: Mercury is a a heavy metal and its presence in our environment constitutes an health-hazard for example in the form of methyl-mercury. Therefore, it is important to construct sensors to detect this pollutant. Research is also being performed on developing optical sensors and mercury can be detected through a range of methods, from point monitoring using Zeeman absorption to 3-D scanning of the atmosphere utilizing Lidar. The aim of the present investigation is to evaluate if a LED in the wavelength region 250-265 nm can be used in order to measure the concentration of the mercury vapour in the air via the 253.7 nm spectral line. This could be used in developing a new type of robust and simple sensor to detect mercury. The theory part of this thesis gives a general introduction to atoms and how they behave, in order to explain the behaviour of mercury. The physics behind the investigation is briefly discussed in order to explain the methods used and developed. The difficulties behind utilizing the LED as a light source is discussed and a comparison with another light source (Hg-lamp) is performed in order to illustrate the differences and challenges between the two light sources. The different designs, which have been developed in an iterative process, are discussed and their performance is compared with each other to describe the process behind the development of the set-ups. Finally the results are presented and discussed. Even though the mercury could not be detected, this investigation lies the foundation for future reference. LEDs will achieve better performance in the future, and we expect this experiment to become more facile, but still not trivial, to perform.