Large‐scale natural gradient tracer test in sand and gravel, Cape Cod, Massachusetts: 1. Experimental design and observed tracer movement

Abstract

A large‐scale natural gradient tracer experiment was conducted on Cape Cod, Massachusetts, to examine the transport and dispersion of solutes in a sand and gravel aquifer. The nonreactive tracer, bromide, and the reactive tracers, lithium and molybdate, were injected as a pulse in July 1985 and monitored in three dimensions as they moved as far as 280 m down‐gradient through an array of multilevel samplers. The bromide cloud moved horizontally at a rate of 0.42 m per day. It also moved downward about 4 m because of density‐induced sinking early in the test and accretion of areal recharge from precipitation. After 200 m of transport, the bromide cloud had spread more than 80 m in the direction of flow, but was only 14 m wide and 4–6 m thick. The lithium and molybdate clouds followed the same path as the bromide cloud, but their rates of movement were retarded about 50% relative to bromide movement because of sorption onto the sediments.

Steady flows driven by sources of random strength in heterogeneous aquifers with application to partially penetrating wells

“…The configuration mostly studied in the past is that of uniform flows in the average (a situation which is ascribed to natural gradient conditions). Mean uniform flows have been investigated experimentally by controlled field tests (e.g., Sudicky 1986; LeBlanc et al 1991), and theoretically by means of numerical codes (a wide review can be found in Zhang 2002;Rubin 2003), as well as of analytical tools (Dagan 1989). There are however many hydrological applications (such as protection zones of wells, pump and treat remediation procedures, pumping tests analysis) of non uniform mean flows.…”

Lattice Boltzmann modeling for tracer test analysis in a fractured Gneiss aquifer

“…Tracer tests can be conducted in steady state or transient mode. Injection of one or more tracers at a time is possible [6][7][8][9][10][11]. Interpretation of tracer test can be numerical and analytical, but the analytical analysis is restricted to steady state flow while numerical analysis can deal with steady or transient state flow.…”

Transport in heterogeneous sediments with multimodal conductivity and hierarchical organization across scales

“…Thus, we limit the analysis to plumes that exist over scales captured in the first three hierarchical levels, which would include the overall scale of some of the better known natural-gradient tracer tests, e.g. Borden (Sudicky, 1986) and Cape Cod (Leblanc et al, 1991).…”