In chemistry, speciation refers to the distribution of an element amongst chemical species in a system. The five chapters of this book each bring a unique perspective on this type of speciation as it pertains to marine biota, x-ray fluorescence spectroscopy, and other areas of interest. Chapter One investigates the bioaccumulation of cadmium, a toxic heavy metal, in marine biota in the Egyptian coastal zones. Chapter Two scrutinizes the applications of energy and wavelength dispersive spectroscopic techniques in various materials. Chapter Three explains the phenomenon of thermoluminescence and the effect of varying readout heating rates on the dosimetric properties of TLD-100 (LiF: Mg, Ti) irradiated with 6 MV X-ray. Chapter Four focuses on the applications of different X-ray spectroscopy techniques and their use in the elemental analysis of water, coal, fly ash, and fertilizer samples. Finally, Chapter Five describes how to select the best speciation model from studies based on potentiometric measurements.