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Polonium behaviour in reservoirs potentially affected by acid mine drainage (AMD) in the Iberian Pyrite Belt (SW of Spain)

Abstract:

The province of Huelva is one of the areas most affected by acid mine drainage (AMD) in the world, which can produce big enhancements and fractionations in the waters affected by AMD. There are very few studies on this issue, and none on polonium-210. Twenty-two water reservoirs were sampled, and the 210Po was measured in both dissolution and particulate phases.The 210Po concentrations in the waters were in the same order of magnitude to those ones for unperturbed systems, although the data published to particulate matter are very scarce. A mean value and standard uncertainty for 210Po of 0.25 ± 0.03 mBq L-1 in the dissolved matter, and 62 ± 9 mBq g-1 in the particulate matter can be established as base line for the reservoirs of the Huelva area. The distribution coefficients (kd) range from 104 to 106 L kg-1, in agreement to the found ones by other authors for the case of neutral waters, but being the lowest values for the more acidic reservoirs.It has been also found that 210Po has a high tendency to be associated to the particulate matter for neutral-alkaline waters, however, under extreme acid conditions (pH < 3), increases the Po tendency to be associated to the dissolved phase. Therefore, the main conclusion obtained in this work is that AMD has no a significant influence on the total activity concentration of 210Po in the waters of reservoirs, but the acidity has a clear influence on its distribution between both dissolved and the particulate phases.