Trace Elements in Soils (Hooda/Trace Elements in Soils) || Arsenic and Antimony

✍ Scribed by Hooda, Peter S.

• Publisher: John Wiley & Sons, Ltd
• Year: 2010
• Weight: 482 KB
• Category: Article
• ISBN: 1405160373
• DOI: 10.1002/9781444319477.ch16

✦ Synopsis

Introduction

Arsenic (As) and antimony (Sb) are chalcophilic metalloids that share numerous similarities in biogeochemical properties. This chapter reviews the chemical properties, environmental/geochemical reactions, phytoaccumulation and toxicology of the two elements.

Arsenic belongs to Group 15 in the periodic table. The electron configuration is [Ar]3d 10 4s 2 4p 3 , and it has four major oxidation states (þ5, þ3, 0, and À3). Arsenic has multiple isotopes, and most of them have very short half-life (t ½ ) of microseconds to milliseconds. Of these, 71 As, 72 As, 73 As, 74 As and 74 As have t ½ of approximately 65 h to 80 days, and 75 As is the only stable isotope. In the soil and water environment, inorganic As is mainly present in two oxidation states (þ3 and þ5). Arsenite, As(III), commonly exists as arsenious acid, As(OH) 3 , in reduced environments. Conversely, an oxidized environment contains more arsenate, As(V), as arsenic acid (for example, HAsO 4 2À ). Antimony also belongs to Group 15 in the periodic table. The electron configuration is [Kr] 5s 2 4d 10 5p 3 , and it has four major oxidation states (þ5, þ3, 0 and À3). The most common oxidation states in low temperature environments are þ5 and þ3. Although Sb has multiple isotopes, most of them have short t ½ of <1 day. Only a few of its isotopes have t ½ of more than a few days: 122 Sb (2.7 days), 124 Sb (60.2 days), 126 Sb (12.3 days), and 127 Sb (3.85 days). Antimony has two stable isotopes, 121 Sb and 123 Sb. Antimony-125 is a fission product of 235 U, and has a half life of $2.76 years. While antimonite, Sb(III), commonly exists as antimonous acid,