Improving Fluorometry as a Source Tracking Method to Detect Human Fecal Contamination in Georgia Waters

In a continuing effort to develop inexpensive source tracking methods to detect human fecal contamination in environmental waters, we combined targeted sampling with fluorometry. Targeted sampling works by identifying hotspots of fecal contamination through multiple samplings over everdecreasing distances. Fluorometry identifies human fecal contamination by detecting optical brighteners, primarily from laundry detergents. On St. Simons Island, targeted sampling and fluorometry identified two hotspots of fecal contamination. One hotspot was confirmed as fecal contamination from humans, but the other was not, most likely because of background organic matter fluorescence. Adding a 436-nm emission filter to the fluorometer reduced this background fluorescence by >50%, and with this filter in place, the second hotspot was identified as fecal contamination from birds. As long as a fluorometer is equipped with a 436-nm emission filter, targeted sampling combined with fluorometry may be a relatively inexpensive method to identify human fecal contamination in water.