Preliminary Study on Heavy Metal Detection in Soil Using Terahertz Time-domain Spectroscopy

Abstract

Heavy metal pollution is becoming a serious problem in agriculture in China. A rapid and accurate detection method is in an urgent need. This paper reports a preliminary work on a feasibility study to apply terahertz (THz) spectroscopy technology for heavy metal detection in soil with collaboration among Oklahoma State University (OSU), China Agricultural University (CAU) and Capital Normal University (CNU) in Beijing, P.R. China. A detailed experiment design and data analysis will be presented. In 2010 and 2011, soil samples were prepared including pure samples with negligible heavy metal ion contents, and samples with different concentrations of heavy metals (Cu2+, Zn2+, and Pb2+). Two sample holders with thicknesses of 1.5mm and 3mm were designed especially for the detection with terahertz spectroscopy. The absorption spectra of the soil samples were collected using two different THz time-domain spectroscopy (THz-TDS) equipments at Oklahoma State University in USA and the Capital Normal University in China. Multivariate statistical methods were used to analyze the collected data. The results showed that different heavy metal ions in a soil sample had unique absorption bands. The changes in spectral responses were relevant to the variations in concentration levels of heavy metal ions. This preliminary study indicated a great potential of THz spectroscopic technology for heavy metal ions detection in soil.