ABSTRACT
Antimony (Sb) is a rather rare element in the earth’s crust, but in the recent past, human activities have led to highly elevated Sb concentrations in soils and sediments at many locations and, as a consequence, to increased exposure of biota to this toxic element. Although often referred to as a heavy metal in ecotoxicological studies, it has mixed metallic and nonmetallic characteristics, corresponding to its position on the boundary between metals and nonmetals in the periodic table. It is therefore more properly described as a metalloid, like arsenic (As) and silicon (Si). In contrast to common soil metal contaminants such as lead (Pb), copper (Cu), and cadmium (Cd), which
CONTENTS
4.1 Introduction ................................................................................................ 119 4.2 Sources, Usages, and Environmental Distribution of Antimony ....... 120 4.3 Antimony Aqueous Chemistry ............................................................... 121
4.3.1 Redox and Acid-Base Chemistry ................................................. 121 4.3.2 Complexation with Dissolved Organic Ligands ....................... 123 4.3.3 Methylated Sb Species ................................................................... 125
4.4 Retention Mechanisms of Antimony in Soils ........................................ 125 4.4.1 Adsorption ...................................................................................... 126
4.4.1.1 Adsorption to Pure Mineral Phases ............................. 126 4.4.1.2 Sorption to Soil Organic Matter .................................... 128 4.4.1.3 Competitive Sorption ..................................................... 129
4.4.2 Precipitation and Coprecipitation ............................................... 132 4.4.3 Uptake by Plants ............................................................................ 134
4.5 Mobilization and Transport of Sb in Soils ............................................. 135 4.6 Concluding Remarks ................................................................................. 138 Acknowledgments .............................................................................................. 139 References ............................................................................................................. 139
speciate as cations, Sb occurs as an oxyanion in soil solutions under aerobic conditions, and therefore behaves very differently from these metals in many respects. Furthermore, Sb is a redox-sensitive element, making its mobility directly susceptible to changes in the soil redox state.
