DISTRIBUTION AND MOBILITY OF ARSENIC AND ANTIMONY IN STREAM WATER, SEDIMENT AND SUSPENDED MATTER IN A FORMER MINING AREA AT GLENDINNING, SOUTHERN SCOTLAND

The small upland catchment of the Glenshanna Burn at Glendinning (Scottish Borders) was investigated for possible As and Sb contamination derived from long-term antimony smelting and mining activities. The aims were to establish the spatial variation in concentration of As and Sb in water, suspended particulate matter (SPM) and sediment of the river system; to assess the level of contamination, and to estimate the chemical forms of As and Sb and their mobility in the river solids. On the basis of multiple and single chemical extractions, it appears that As and Sb partitioning is highly variable within this river system. Arsenic and Sb in all the compartments studied showed high concentrations (exceeding acceptable guidelines). Arsenic concentrations (as high as 970 µg L^-1) in water samples adjacent to mine tailings indicate mobilization of As. Despite the high relative availability of Sb in sediments only two water samples contained detectable Sb levels. The main sink for Sb was the sediment. Speciation, saturation index and solid phase stability for stream-water samples were evaluated using Geochemist Workbench™ and PHREEQC computer programs. It was revealed that both As and Sb undergo precipitation and dissolution in the stream water, their solubility depending mainly upon Fe-Al oxy/hydroxide and calcite dissolution in the water system. The only As and Sb bearing mineral phases supersaturated in the waters were Ba₃(AsO₄)₂, and SbO₂ and Sb(OH)₃. Principal Component Analysis indicates both geogenic and anthropogenic influences on As and Sb behaviour in the soil-sediment-water system.