Methods for the Determination of Heavy Metals and Metalloids in Soils

Abstract

This chapter explores the analytical methods currently available for the measurement of heavy metal content in soils, ranging from well-established techniques routinely applied in laboratories worldwide, to newly emerging approaches, and with emphasis on the need to select strategies that are ‘fit-for- purpose' in terms of the information required. Included are guidelines for field sampling and for the storage of samples and avoidance of contamination. Brief information is provided on analytical techniques directly applicable to solid samples including neutron activation analysis, laser-induced breakdown spectrom- etry and X-ray-based methods. Suitable approaches to sample extraction for differ- ent situations are summarised (total digestion, pseudototal digestion, single and sequential extraction) together with examples of procedures involving hot-plate, block, bomb, and microwave apparatus. The use of extractants to assess (plant) bioavailability or (human) bioaccessibility of heavy metals in soils is discussed. Details are provided of the various types of atomic spectrometry that nowadays serve as ‘workhorses' for trace metal determination in environmental chemistry, with particular emphasis on their principles, strengths, limitations and applicability. Included are flame and electrothermal atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry. The chapter also provides a brief introduction to the vast topic of speciation analysis, an area of particular interest for metals that can occur in different oxidation states e.g. Cr, or that have environmentally important organometallic forms e.g. Hg. Finally, some recommendations are given on strategies that researchers should adopt whenever possible to improve the quality of their analytical data. C.M.