posted on 2012-01-17, 00:00authored byJeffrey H. Writer, Joseph N. Ryan, Steffanie H. Keefe, Larry B. Barber
The majority of previous research investigating the fate of endocrine-disrupting
compounds has focused on single processes generally in controlled
laboratory experiments, and limited studies have directly evaluated
their fate and transport in rivers. This study evaluated the fate
and transport of 4-nonylphenol, 17β-estradiol, and estrone in
a 10-km reach of the Redwood River in southwestern Minnesota. The
same parcel of water was sampled as it moved downstream, integrating
chemical transformation and hydrologic processes. The conservative
tracer bromide was used to track the parcel of water being sampled,
and the change in mass of the target compounds relative to bromide
was determined at two locations downstream from a wastewater treatment
plant effluent outfall. In-stream attenuation coefficients (kstream) were calculated by assuming first-order
kinetics (negative values correspond to attenuation, whereas positive
values indicate production). Attenuation of 17β-estradiol (kstream = −3.2 ± 1.0 day–1) was attributed primarily due to sorption and biodegradation by
the stream biofilm and bed sediments. Estrone (kstream = 0.6 ± 0.8 day–1) and 4-nonylphenol
(kstream = 1.4 ± 1.9 day–1) were produced in the evaluated 10-km reach, likely due to biochemical
transformation from parent compounds (17β-estradiol, 4-nonylphenolpolyethoxylates,
and 4-nonyphenolpolyethoxycarboxylates). Despite attenuation, these
compounds were transported kilometers downstream, and thus additive
concentrations from multiple sources and transformation of parent
compounds into degradates having estrogenic activity can explain their
environmental persistence and widespread observations of biological
disruption in surface waters.