Animal Waste, Water Quality and Human Health

336Animal Waste, Water Quality and Human Healthversus qualitative (presence/absence) assessments. It was found that quantitativesource tracking functioned best when there were equal numbers of differenthosts shedding large amounts of highly-specific markers in well-mixedenvironments (Leach et al. 2008). Variation in the distribution and density offaecal contamination in the environment contributed to method error with thehighest error associated with sparsely-contaminated and/or unmixedenvironments. This suggests that temporal variability, a survey of thegeographic distribution of host-specific markers, an examination of cross-speciesmarker occurrence and an assessment of environmental decay rates are allimportant preliminary steps prior to engaging in and contributing to the successof quantitative source attribution projects.9.5 PRACTICAL UTILITY OF SOURCE ATTRIBUTIONSTUDIESSource attribution has been successfully employed in determining the cause offaecal contamination at bathing beaches (Brownell et al. 2007, Korajkic et al.2009) and when examining faecal loading as a function of land use (Gourmelonet al. 2007, Lee et al. 2008). Although many of these studies have focused onhuman-specific targets, some have included one or more methods for detectionof animal faeces (Cole et al. 2003, Stewart-Pullaro et al. 2006, Gourmelon et al.2007, Stapleton et al. 2007, Lee et al. 2008, Fremaux et al. 2009, Jenkins et al.2009, Stapleton et al. 2009, Edge et al. 2010). Source tracking is becomingan integral part of the total maximum daily load (TMDL) assessment andimplementation strategy in the USA. In Florida, a recent study used markers forhuman (Bacteroidales HF183 and human polyomaviruses), general ruminant,and horse targets to determine the dominant contributors to elevated FIO levelsin tributaries of the Hillsborough River (Wapnick et al. 2007). The success ofthis study relied on intensive sampling of the tributaries using low-cost methods(FIO testing by membrane filtration) to determine the most contaminated sites asa precursor to targeted deployment of source tracking methods based on athorough land use assessment and field survey of probable sources. The use ofmultiple assessment methods allowed the identification of specific sites andsub-watersheds dominated by ruminant or human pollution as well as those thatreceived mixed inputs. The study results were incorporated into the basinmanagement action plan (BMAP) of Hillsborough County. 3 Of interest, thisstudy found low correlation between marker detection and FIO concentrations;3http://www.dep.state.fl.us/water/watersheds/bmap.htm