Synchrotron Radiation Study on Ancient Burnt Rice Found at Archaeological Sites in Thailand

Abstract

Rice is the food staple for most of the world’s population especially Asians. It is also the essence of life of people in Thailand. Archaeological evidence based on the paddy rice reveals the rice planting in northeastern Thailand over 5,000 years ago. The burnt rice grains have been found in many archaeological sites in Thailand, which are involved with the religious ceremony and home prosperity. In this work, the synchrotron radiation has been applied to investigate the elemental distribution, chemical composition and bio-molecular structure, and three-dimensional segmentation of the ancient burnt rice samples from Nakorn Nayok (Ban Dong Lakon), Suphan Buri (U-Thong), and Prachin Buri (Sri Mahosot) using micro-beam XRF (SR µ-XRF), Infrared spectroscopy (SR IR), and X-ray tomographic microscopy based on synchrotron radiation (SR XTM), respectively. Field emission scanning electron microscope (FE SEM) incorporated with energy dispersive spectrometer (EDS) have been carried out in order to characterize the structure and composition of samples. It has been found that the grains are oblong in shape with a rough surface. Major elements in the grains are C, Si, Ca, and Al. Other trace elements such as Ti, Cr, Mn, Fe, Ni, Cu, and Zn are also detected. The IR spectra provide some information about molecular bonds. The tomographic investigations reveal the internal structure of ancient burnt rice.