TRACER TEST IN FRACTURED CHALK .1. EXPERIMENTAL-DESIGN AND RESULTS

A two-well tracer test was conducted in eastern Denmark, in which a sh ort duration pulse of lithium chloride was injected into a recharge we ll and made to flow through a fractured chalk aquifer to a discharge w ell. The wells were 25 m apart, and the concentration of lithium arriv ing at the discharge well was monitored at five vertical intervals in the well for a 21-day period. The observed breakthrough curves show a sharp breakthrough front, with an arrival time that is consistent with advective transport through the fractures in the chalk. The breakthro ugh curves also exhibit a long tail in the falling limb, suggesting th e influence of a secondary transport mechanism of diffusion into the p orous matrix.