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Evaluating Effluent Impacts with the AquaFluor Handheld Fluorometer

Parameters: Chlorophyll

Effluent from wastewater treatment plants (WWTP) is one of the main contributors to nutrient pollution nationwide. Dr. Jeffrey Simmons and his students at Mount St. Mary's University are investigating the effects of these nutrients on algal productivity in Tom's Creek, Frederick County, Maryland. Measuring phytoplankton response to a point source of nutrient pollution is challenging because the algae are moving downstream. By the time they are able to respond with increased growth and biomass they may be several miles downstream. Also it is often difficult to find a reference stream to which the polluted stream can be compared.

Tom's Creek is a perfect site for evaluating effluent impacts because discharge from the Emmitsburg WWTP stops for three months each summer. Thus, it is possible to compare algal productivity during times of discharge with productivity during times of cessation. Dr. Simmons and his students collect water samples from 3 locations upstream and 8 locations downstream of the WWTP. In vivo Chlorophyll a is measured at the time of collection and another subsample is preserved for nutrient analysis.

Preliminary results indicate that phytoplankton biomass increases more downstream of the WWTP while it is discharging than when it is not discharging. Furthermore, this biomass increase peaks between 5 and 6 km downstream of the discharge point. Dr. Simmons continues to monitor this phenomenon. Phytoplankton biomass is measured in vivo with the Turner Designs AquaFluor Handheld Fluorometer. The AquaFluor is calibrated monthly with a primary standard of chlorophyll a and daily with a secondary standard.

The portability of the meter allows us to measure the chlorophyll fluorescence as soon as we collect the sample instead of having to take the sample back to the lab where holding time becomes an issue. In a project like this where the whole day is spent sampling, samples would have to sit overnight before being analyzed in the lab. The low detection level is also an advantage.

Author: Jeff Simmons

Insitution: Mount St. Mary's University, Emmittsburg, Maryland, USA

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