Project Summary

2012 Google Science Fair- ANIRUDH JAIN

Our environment is a precious resource, and at the very core of human existence. Humans cannot survive and thrive without the environment and all the resources it provides. As we invent and use more products for personal convenience, there is an increasing incidence of manmade chemicals in our environment. One of these chemicals is silver nanoparticles. Several commercially available products use the antimicrobial properties of silver nanoparticles to kill harmful microorganisms, clothing being a prime example amongst other uses. The increasing incorporation of nanoparticles in products is resulting in the nanoparticles being released into the environment. For example, socks made of fabric treated with silver nanoparticles lose some of these particles every time they are washed. Therefore, it has become extremely important to detect the extent of contamination of these particles into the environment. This project examines if the use of diatoms (Asterionella formosa) as bioindicators for nanoparticle pollution presents a practical and simple alternative to other nanoparticle detection methods, such as elemental analysis of water samples. To test this hypothesis, three sets of healthy diatoms samples were exposed to silver nanoparticle solution of varying concentration (0.5%, 2.5%, and 5%), and one set was used as control without the addition of silver nanoparticles. Over a two-week interval, samples were periodically drawn from these sets and measured for growth (fluorescence) and health (quantum efficiency of Photosystem II, an indicator of photosynthetic performance). The diatoms samples exposed to silver nanoparticles showed either a slower growth or a decline in growth in comparison while the control sample of diatoms that was not exposed to the silver nanoparticles grew along the predicted growth curve for healthy diatoms. The experimental results supported the hypothesis that the growth and health of freshwater diatoms will be affected adversely in proportion to the exposure to increasing concentrations of silver nanoparticles and conclusively established that diatoms are a good and practical way of detecting nanoparticle pollution in the environment.