Improving fluorometry as a source tracking method to detect human fecal contamination

Abstract

ABSTRACT:In a continuing effort to develop inexpensive source tracking methods to detect human fecal contamination in environmental waters, targeted sampling was combined with fluorometry. Targeted sampling works by identifying hot spots of fecal contamination through multiple samplings over ever-decreasing distances. Fluorometry identifies human fecal contamination by detecting optical brighteners, primarily from laundry detergents. Because organic matter fluoresces and interferes with fluorometry, two locations were chosen for sampling: waters relatively low in organic matter at Mayagiiez Bay, Puerto Rico, and waters relatively high in organic matter at St. Simons Island, Georgia. In Puerto Rico, targeted sampling and fluorometry quickly and easily identified two hot spots of human fecal contamination in the Yagiiez River, which flows through the city of Mayagiiez. Another source tracking method, detection of the esp gene, confirmed their human origin. On St. Simous Island, targeted sampling and fiuorometry identified two hot spots of potential human fecal contamination. Detection of the esp gene confirmed the human origin of one site but not the other, most likely because background organic matter fluorescence interfered with fhiorometry. A separate experiment showed that adding a 436-um emission filter to the fluorometer reduced this background fluorescence by > 50%. With the 436-nm Filter in place, another sampling was conducted on St. Simons Island, and the second hot spot was identified as fecal contamination from birds. As long as the fluorometer was equipped with a 436-nm filter and organic matter concentrations were considered, targeted sampling combined with fluorometry was a relatively inexpensive method for identifying human fecal contamination in water.

Tracking human faecal contamination in tropical reservoirs in Puerto Rico

“…Water sample fluorescence was measured with a Turner Designs Model 10‐AU‐005 field fluorometer (Turner Designs, Sunnyvale, CA, USA), fitted with filters for excitation (360 nm) and emission (436 nm) to improve the fluorometric detection of OBs (Hartel et al . 2007b).…”

“…2006; Hartel et al . 2007a,b, 2008). To address potential problems with background fluorescence, we also determined fluorescence loss upon irradiation of the samples at 366 nm, as suggested by Hartel et al .…”

Bacterial source tracking guides management of boat head waste in a coastal resort area

“…After light absorption, fluorescence is given off during a second excited state and can be measured by a fluorometer. Since household plumbing systems combine wastewater from toilets and washing machines, the presence of optical brighteners and fecal coliform bacteria in a waterway may indicate an input of human origin (Hartel et al, 2007a). Optical brightener samples were collected by filling Nalgene 125 mL opaque collection bottles 10 cm below the surface facing into the stream (Tavares et al, 2008).…”

“…A kit was added to the fluorometer that included a lamp (10e049) emitting near UV light at 310e390 nm, a filter (10-069R) for the 300e400 nm light range, and finally a 436 nm filter was added to greater decrease background fluorescence (Hartel et al, 2007a). A standard curve was created using serial dilutions from 100 mg of Tide detergent (Procter and Gamble, Cincinnati, Ohio) in 1 L of deionized water.…”

Microbial contamination and shellfish safety

“…The results suggested that non-human sources may constitute a majority of the fecal pollution in the study area, with a few human sources near boat moorings and sewage collection lift stations. Hartel et al (2007) included use of a humanspecific marker (esp) in Enterococcus faecium (Scott et al, 2005) to complement an in-depth assessment of the use of fluorometric detection of optical brighteners as an indicator of fecal contamination. Inclusion of organic matter analysis and an additional filter for fluorometry were required for accurate source identification in coastal waters.…”