MATRIX POROSITY AS THE MOST IMPORTANT PARAMETER OF FISSURED ROCKS FORSOLUTE TRANSPORT AT LARGE SCALES

Simple considerations show that tracer and/or pollutant velocity at la rge scales in fissured rocks can be described by the formula upsilon(t )n(p) almost-equal-to (DELTAH/DELTAx)k, where upsilon(t) is the mean v elocity of a conservative tracer or pollutant, n(p) is the matrix poro sity, DELTAH/DELTAx is the hydraulic gradient, and k is the hydraulic conductivity. The applicability of the formula is discussed and its va lidity tested in several case studies in which hydraulic conductivitie s calculated from either pollutant transport velocity or environmental tracer ages were compared with those known or estimated from other de terminations. The influence of matrix diffusion on the environmental t racer ages can also be proved independently by comparison of the rock volume (V(rock)) estimated from the hydrogeologic map with that calcul ated from volumetric flow rate (Q), age of tracer (t(t)) and matrix po rosity (V(rock) almost-equal-to Qt(t)/n(p)).