Submitted to: American Geophysical Union
Publication Type: Abstract only
Publication Acceptance Date: 5/29/1998
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Field experiments were conducted at two sites where tile drain facilities were used to monitor breakthrough of four conservative tracers, which were sequentially applied during a very mild irrigation. Bromide was sprayed shortly before irrigation started, while three different fluorobenzoic acids were applied at 2, 4, and 6 hours after irrigation started, respectively. In soil with low clay and organic content, these four tracer were detected at 0.9 m at: 360, 102, 42, and 18 minutes after the applications, respectively. The mass recoveries were 4.06%, 13.9%, 18.7%, and 19.7%, respectively. In soil with high clay and organic content, the fast arrival times were almost identical to the other site, but, mass recoveries decreased significantly. These results suggested that: (1) breakthrough patterns of sequentially-applied tracers can quantify the impact of preferential flow paths on contaminant transport; (2)preferential lflow dictates the deep and fast leaching that occurs initially; (3)clay an organic content dictate the total leaching of adsorbing chemicals; and (4) the spectrum of the hydraulically-active pores along preferential flow paths in unsaturated soils might be universal. It was essential to intensively monitor contaminant transport during the first day after a rainfall.