Plant available arsenic (As) is not defined by its total content but by the various forms in soil. The aims of this study were to determine the amounts of As phases in soils extracted in the vicinity of the antimony mines; to study soil surface processes affecting formation of most mobile phases of As and the identification of sources of As phases in C soil horizon. Five fractions of soil As were determined by sequential extraction analyses (As F1, As F 2, As F 3, As F 4 and As F 5) in A and C horizons. The identification of the origin of As fractions were made by mean of principal component analyses (PCA) including Pearson correlations. The amount of the most mobile forms of As (As F1 and F2) was below 1%. The content of As F1, As F2 and As F4 decrease with soil depth, while aqua regia As and phases F3 and F5 increase with depth. Principal component analyses (PCA) showed that the content of As F2 is affected by anthropogenic factor and the content of As F4 by biological factor. In C horizon, As F2 and F4 are influenced by the leaching processes in soil. Arsenic F5 is bound to sediment rocks. The soil surface processes increases the availability of As in soil. The most mobile forms of As were found in deeper soil horizon that is due to the leaching of As with water from biological sources. The content of semi available phase of As F3 increases with depth, with stronger bounds due to the linkage to the amorphous Fe hydroxides
