INTRODUCTION TO THE CHEMISTRY AND GEOCHEMISTRY OF THE ELEMENTS S. Reeder1, H. Taylor1, R.A. Shaw1 and A. Demetriades2 1British Geological Survey, Keyworth, Nottingham, UK 2Institute of Geology and Mineral Exploration, Athens, Greece A brief overview of the chemistry and 5. atmophile (gas-loving): elements that exist geochemistry of each element discussed in this either uncombined or as highly volatile volume is provided (Table 1). compounds. The texts begin with a brief summary of the Controls on the element’s behaviour are element’s chemistry, including its position in the discussed with particular respect to the periodic table, atomic number, atomic mass, main geochemistry of the element in the surface oxidation states, naturally occurring isotopes and environment. Information about the nature of soil abundances, and main chemical associations. solutions, and the global average abundance of The element’s geochemistry is then discussed. each element in soil is given. The basic natural Main mineral forms and associations are processes contributing to the concentration of the identified. Data on abundance in the earth’s crust element in stream water are discussed, including and in different rock types are provided. (i) acid-base controls, (ii) complexation, (iii) Elements are characterised as: oxidation-reduction, (iv) dissolution/precipitation, 1. lithophile (rock-loving) – elements with a and (v) adsorption/partitioning reactions. The strong affinity to form oxides, and mainly chemical forms of the element in the aqueous rock-forming silicates; environment are discussed and typical 2. chalcophile (copper-loving) – elements concentrations of each element in river water are with a strong affinity to form sulphides; given, wherever available. 3. siderophile (iron-loving) – elements with a Finally, a brief discussion is presented on the strong affinity to form metals or solid uses of each element, potential anthropogenic solutions in metals, sources of contamination, the element’s biological 4. biophile or organophile (organic matter significance and likely hazards posed to plants, loving) – elements that concentrate in animals and humans. living matter, and Acknowledgements Dr Neil Breward, Dr Chris Johnson and of the elements discussed in this report. A further Professor Barry Smith of the British Geological source of information is the Website of the Survey are gratefully acknowledged for Association of Applied Geochemists permitting their text from a number of (http://www.appliedgeochemists.org/). The publications, including BGS (1999, 2000), authors would also like to thank Ms Jennifer Cook Johnson et al. (2001) and Sewell (1999), to be for her thorough and incisive review of the draft used as a basis for the descriptions given for some text. 19 20.