Optimization of the anthropogenic vadose zone monitoring at the sulfidic mining waste dumps and engineering constructions

摘要

Acid Rock Drainage (ARD) that causes severe ground water deterioration and mobilization of potentially toxic elements is one of the persistent environmental problems in countries with a developed extractive industries. In brief, it results from exothermic process of sulfide minerals decomposition in mining waste deposited at the surface in the presence of atmospheric oxygen and moisture/infiltration water from precipitation. To attenuate the environmental impact of extractive wastes, the European Commission issued adequate legislative documents: a Directive on the management of waste from the extractive industries (2006) and a Reference document on Best Available Techniques for Management of Tailings and Waste-Rock in Mining Activities (BREF, 2004). These documents oblige the extractive industry to intercept the generation of ARD. Simultaneously, mining waste is an attractive material widely used in civil engineering as a common fill. This results in the need of early-warning monitoring of a potential of disposed/reused mining waste to generate acidic and/or highly mineralized leachate and of the efficiency of interceptive/insulation protection measures. The performance-based off-site techniques comprise sampling waste material along the waste layer profile by drilling, with subsequent pore solution extraction and analysis by ICP-MS. Though detailed and precise, these techniques are time-consuming and expensive, thus being limited to few randomly selected profiles. Large area of the sites and heterogeneity of a material causes problems with proper selection of representative profiles and therefore with evaluation of the environmental behavior of a reused or disposed material. For better characterization of a problematic site, its screening with cone penetrometer integrated with real-time, downhole sensing devices equipped with sensors for measurements of temperature, pH, rock moisture content and conductivity seems to be the best solution, giving the most important information concerning reactivity of a material in the waste layer and efficiency of protective measures.