| dc.description.abstract | Understanding the fate of organic compounds in river systems is important for protecting
watersheds and human health. While individual mechanisms of compound transformation and transport
can be quantified, determining their relative importance under various photochemical and
biogeochemical conditions poses another challenge. Aquatic pesticide treatments provide an
opportunity for scientists to conduct controlled field studies and validate a systematic research
framework for assessing chemical fate. This research synthesizes laboratory and in-situ experiments
with field studies on the lampricide 3-trifluoromethyl-4-nitrophenol (TFM), a compound that has
been applied to tributaries of the Great Lakes since the 1950s to control for the invasive sea
lamprey (Petromyzon marinus). Tandem studies of a photoreactive tracer (uranine), a sorptive tracer
(rhodamine-WT), and a conservative tracer (bromide) are used to quantify specific loss processes.
Our study of two treatments in the Upper Peninsula of Michigan reveal physical transport processes
and local hydrologic conditions largely control the residence time of TFM in the hyporheic zone,
where most biogeochemical transformations occur. Evidence of transient subsurface storage (i.e.,
reincorporation of TFM back into the water column over treatment timescales) suggests
photodegradation may be important, yet in-situ batch experiments and modeled solar irradiance
reveal environmental photodegradation kinetics are much slower than laboratory kinetics. Alignment
between in-situ experiments, kinetic models, and field observations highlights the importance of
using a synergistic approach to predict compound persistence in the environment. | en_US |
