Friday, August 31, 2018

OSCAR Student Robert Spaine Quantifies Micropollutant Levels in Organisms

I have been participating in research, which seeks to quantify micropollutant levels in organisms in local river communities, and to test the capabilities of the KABAM (Kow (based) Aquatic BioAccumulation Model) model to predict the bioaccumulation of micropollutants in different trophic levels of these communities. Those of us on the chemistry team received samples of river water, zooplankton, sediment, clams, submerged aquatic vegetation and three species of fish from the field. The first step of our laboratory methods was to use an organic solvent to extract micropollutants from these samples using a method known as QuEChERS (Quick Easy Cheap Effective Rugged Safe). The extractions were then analyzed using an LC-MS/MS instrument. To analyze the data obtained from this instrument, researchers on the Chemistry team of the project were divided into two groups, one to quantify the concentrations of endocrine disrupting compounds and the other to quantify the concentration of other micropollutants found in pharmaceuticals and personal care products (PPCPs). I belong to the group quantifying the concentrations of endocrine disrupting compounds.

Quantifying the concentrations of endocrine disrupting compounds from chromatograms has not been as easy as I expected from previous experience with gas chromatography. Because the analyte chemicals (in this case, endocrine disruptors) are at very low concentrations, the electronic signal which they produce is often very difficult, if not impossible to distinguish from electronic noise produced in the instrument. Even when a signal is found, poor signal resolution makes it difficult to use them to calculate an accurate concentration. In many cases, we can tell that an endocrine disrupting compound is present in river water, sediment, or one of the organisms, which was sampled, but the exact concentration of the compound is to some degree indeterminate. Some of the compounds commonly detected so far include atrazine, diclofenac, several species of parabens, and certain sunscreen ingredients.

These preliminary results indicate multiple sources of endocrine disruptor pollution in the Potomac watershed. Atrazine is a common herbicide and its presence is almost certainly a result of runoff from agricultural land; on the other hand, diclofenac is an NSAID drug and parabens are commonly found in cosmetics and both likely entered the Potomac watershed through inadequate treatment of human wastewater. So, for our research to be useful, further research will need to be completed to find more efficient means of managing wastewater pollution and developing agricultural solutions, which avoid releasing endocrine disruptors into local waterways.