Despite the major efforts that have been made over recent years to clean up the environment, pollution remains a major problem and poses continuing risks to health. Thus, the determination of contaminants in environmental samples is a challenging and critical issue. Highly accurate analytical techniques provide the possibility to assess and map the organic and inorganic pollutants in complex atmospheric, water, and soil matrices qualitatively and quantitatively. The present chapter brings together the wealth of information in the current literature, covering both the fundamentals and applications of these methodologies. The main attention is given to neutron activation analysis, inductively coupled plasma mass spectrometry, and inductively coupled plasma atomic emission spectroscopy. The principles, main strengths, and weaknesses of each technique are discussed. Several examples of techniques applied in air, water, and soil sample analysis are presented.
TopNeutron Activation Analysis
Neutron activation analysis (NAA) is an important analytical technique for performing, both qualitative and quantitative, multi-elemental analysis in order to determine the content of major, minor, and trace elements in environmental samples (Gibson, 2004). In 1998, NAA was defined by the Comité Consultatif pour la Quantité de Matière — Métrologie en Chimie as the primary method of measurement, which is a method having the highest metrological properties, whose operation can be completely described and understood, for which a complete uncertainty statement can be written down in terms of SI units (Greenberg et al., 2011).
In general, activation analysis is based on the conversion of stable nuclei to radioactive one via nuclear reactions and measurement of the reaction products. In NAA the nuclear reactions occur via bombardment of the sample to be analyzed with neutrons. The reaction products to be measured are either the radiation, released nearly instantaneously upon neutron capture; or, if the resulting new nuclei are radioactive, the induced radioactivity by which they decay (Greenberg et al., 2011). The most common occurring reaction is the (n,γ) reaction, but also reactions such as (n,p), (n,α), (n,n′) and (n,2n) are important.
Neutrons can be produced in: (i) isotopic neutron sources, (ii) particle accelerators or neutron generators and (iii) nuclear research reactors. Reactors are the strongest sources of neutrons. The neutron output of research reactors is often quoted as neutron flux in an irradiation facility and varies, depending on reactor design and reactor power, between 1011 and 1014 n cm–2 s–1(Trincherini et al., 2009).