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Two samples were also analysed for polychlorinated dioxins and furans (PCDD/Fs), a class of chemical that can be formed during the combustion of materials present in e-waste. Soil from an open burning site was moderately contaminated, while sediment from the Agbogbloshie lagoon contained a very high level of these highly toxic, highly persistent and bioaccumulative chemicals, at a level just below the threshold defined as being indicative of serious contamination for sediments in the Netherlands. Though this study did not attempt to quantify damage caused to the environment or human health, the results do indicate that the exposure of workers and bystanders to hazardous chemicals may be substantial. In. | Sensors 2012 12 481-488 doi 10.3390 s120100481 OPEN ACCESS sensors ISSN 1424-8220 www.mdpi.com journal sensors Article Measurement of Organic Chemical Refractive Indexes Using an Optical Time-Domain Reflectometer Chien-Hung Yeh 1 Chi-Wai Chow 2 Jiun-Yu Sung 2 Ping-Chun Wu 2 Wha-Tzong Whang 3 and Fan-Gang Tseng 4 1 Information and Communications Research Laboratories ICL Industrial Technology Research Institute ITRI Hsinchu 31040 Taiwan 2 Department of Photonics and Institute of Electro-Optical Engineering National Chiao Tung University Hsinchu 30010 Taiwan E-Mails cwchow@faculty.nctu.edu.tw C.-W.C. tom7721.eo96@g2.nctu.edu.tw J.-Y.S. depew007@yahoo.com.tw P.-C.W. 3 Department of Materials Science and Engineering National Chiao Tung University Hsinchu 30010 Taiwan E-Mail wtwhang@cc.nctu.edu.tw 4 Department of Engineering and System Science National Tsing Hua University Hsinchu 30013 Taiwan E-Mail fangang@ess.nthu.edu.tw Author to whom correspondence should be addressed E-Mail yeh1974@gmail.com Tel. 886-3-591-5698 Fax 886-3-582-0226. Received 2 December 2011 in revised form 28 December 2011 Accepted 4 January 2012 Published 5 January 2012 Abstract In this investigation we propose and experimentally demonstrate a method for measuring the refractive index RI of liquid organic chemicals. The scheme is based on a single-mode fiber SMF sensor and an optical time-domain reflectometer OTDR . Here due to the different reflectance R between the SMF and organic liquid chemicals the reflected power level of the backscattering light BSL measured by the OTDR would be different. Therefore we can measure the RI of chemical under test via the measured BSL level. The proposed RI sensor is simple and easy to manipulate with stable detected signals and has the potential to be a valuable tool for use in biological and chemical applications. Keywords fiber sensor OTDR refractive index RI Sensors 2012 12 482 1. Introduction Refractive index RI is one of the important optical parameters of
