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Title: COMPARISON OF PREFERENTIAL CHEMICAL TRANSPORT AT HIGH AND LOW IRRIGATION RATES

Author
item Gish, Timothy
item KUNG, K.J. - UNIV OF WISCONSIN
item KLADIVKO, E. - PURDUE UNIV
item POSNER, J. - UNIV OF WISCONSIN
item BUBENZER, G. - UNIV OF WISCONSIN
item Helling, Charles
item STEENHUIS, T. - CORNELL UNIV

Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: 10/21/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Without flux information, the variability of matrix and preferential flow processes makes scientific interpretation of chemical transport uncertain and development of effective non-point source legislation nearly impossible. Chemical fluxes of bromide (Br; 280 kg/ha) and penta-fluorobenzoic acid (PFBA; 121 kg/ha) were evaluated at two irrigation nrates (3.1 mm/h and 0.89 mm/h) under near steady state conditions at the Univ. of Wisconsin, Madison. Tracers were applied to a 3.5m x 24m region parallel to and offset 0.3m from a tile drain. At an irrigation rate of 3.1 mm/h nearly 20% of the applied Br was recovered in the tile line after 80 mm of irrigation, although an estimated pore volume is about 350mm of water. On the other hand, at an irrigation rate of 0.89 mm/h only 0.32% of the applied PFBA was lost through leaching after 80 mm of irrigation. The rapid appearance of Br and the large quantities leached with small water inputs suggest a flow process dominated by preferential flow, while the main PFBA breakthrough pattern fitted the 1-D convective-dispersive transport well, suggesting that the PFBA transport was dominated by matrix flow. This study suggests that there may be a critical water flux whereby preferential flow is initiated and subsequently dominates chemical transport through soil.