Assessment of acid rock drainage pollutants release in the uranium mining site of Pocos de Caldas - Brazil

We compared three different techniques to assess acid drainage occurrence c onnected to pyritic waste rock piles at a uranium mining and milling site i n Pocos de Caldas - Brazil: (I) mass balance calculations, (2) column leach ing experiments and (3) geochemical modelling. The study site was chosen be cause all the drainage coming from the pile is collected in one holding pon d and a huge database (monitoring program) was available. The three indepen dent methods predicted similar values for the intrinsic oxidation rate (IOR ) (about 10(-9) kg m(-3) s(-1)). We estimate the total time for consumption of all oxidizable material in the dump to be greater than 500 years. Geoch emical model results showed a good agreement between predicted sulphate con centrations in relation to those found in the waste pile drainage, although the Al values were overestimated and pH values were underestimated. (C) 20 01 Elsevier Science Ltd. All rights reserved.