Ongoing Research
The Fate of Hormones in the Aquatic Environment
Starting in the early 1990s, researchers began reporting feminization of male fish (e.g., the presence of egg proteins in their blood). In rivers that received significant inputs of municipal wastewater effluent, the feminization of male fish was found to be attributable to the presence of steroid hormones, such as 17beta-estradiol, ethinyl estradiol and estrone.
Over the past decade, our research group has developed analytical methods for quantifying the extremely low concentrations of steroid hormones present in the aquatic environment (e.g., certain species of fish can be feminized by exposure to steroid hormones at concentrations as low as 1 ng/L). We also have studied the fate and transport of these compounds and more recently have begun to study sources of steroid hormones unrelated to municipal wastewater.
Read more about this project here.
Oxidation of Contaminants by Iron Nanoparticles in the Presence of Oxygen
We are currently examining the potential for using ZVI nanoparticles to produce strong oxidants. We have found that when ZVI is exposed to oxygen it can be used to degrade many different types of organic contaminants (Keenan and Sedlak 2008a). However, the reactions tend to be inefficient, and only a small fraction of the ZVI is converted into oxidants. We have found two ways of increasing the yield of oxidants: adding iron-complexing ligands (Keenan and Sedlak, 2008b) and adding athe catalyst POM (Lee et al. 2008).
We are currently exploring ways of employing these findings in the development of a heterogeneous catalyst that can be used in water treatment systems. We also are studying the effects of ZVI reactions on biological systems because ZVI might be useful for disinfection of water and the reactions may provide insight into damage to cells casued by exposure to fine particles.
Read more about this project here.
Use of Iron to Control of Methylmercury Formation in Wetlands
Our previous experiments were conducted under well-controlled laboratory conditions using either pure cultures of sulfate-reducing bacteria or wetland sediments incubated in closed containers. In our current research project, we are exploring the effect of iron addition on mercury methylation under conditions closer to those encountered in the field using microcosms with wetlands plants and a simulated tidal cycle. Preliminary results indicate that iron addition decreases methylercury production and that the effect of iron addition persists for at least three months. Ongoing research is targeted at determining the dose of iron needed for effective methylmercury control with the objective of conducting pilot-scale experiments at field sites where wetland restoration in planned in the San Francisco Bay region.
Read more about this project here.
Publications for these projects and others can be viewed here.