Martin F. Helmke

Learn More
Fractures in till may provide pathways for agricultural chemicals to contaminate aquifers and surface waters. This study was conducted to quantify the influence of fractures on solute fate and transport using three conservative and two nonconservative tracers. The conservative tracers were potassium bromide (KBr), pentafluorobenzoic acid (PFBA), and(More)
a solute diffuses may cause the observed, or effective diffusion coefficient (De) to be lower than the diffusion Diffusion is often the dominant mode of solute transport in soils coefficient of a compound in water (D0) (Rao et al., when advection is minimal. This paper describes the application of a radial diffusion cell method to estimate the effective(More)
Discrete-fracture and dual-porosity models are infrequently used to simulate solute transport through fractured unconsolidated deposits, despite their more common application in fractured rock where distinct flow regimes are hypothesized. In this study, we apply four fracture transport models--the mobile-immobile model (MIM), parallel-plate(More)
Tills are considered by many to be impermeable and thus should prevent vertical and horizontal transport of pointand nonpoint-source contaminants. However, studies in Iowa have shown that aquifers underlying till are contaminated and that streams contain high concentrations of nutrients and pesticides (e.g., Kolpin et al., 1995; Burkart et al., 2004). We(More)
  • 1