b'A comparative study of lipid extraction methods for thequantification of biomarkers within soil and cattle slurryManley A1,2, Collins AL1, Mellander P-E2,3 and Jordan P4 1Sustainable Agriculture Sciences, Rothamsted Research, North Wyke, Okehampton, UK,EX20 2SB2Agricultural Catchments Programme, Teagasc, Johnstown Castle Environmental Research Centre, Wexford, Co. Wexford, Ireland3Crops, Environment and Land Use Programme, Teagasc, Johnstown Castle Environment Research Centre, Wexford, Co. Wexford, Ireland4School of Geography and Environmental Sciences, Ulster University, Cromore Road, Coleraine,BT52 1SAPotable water is a precious resource, so there are policies and programmes worldwide toprotect and/or improve water quality. A key contributor to the decline of water quality isagriculture and associated faecal/nutrient pollution. Faecal waste causes excessive nutrient enrichment and one result is eutrophication. The latter problem has resulted in the EU Nitrates Directive and its associated Action Programme rules for managing amendments to agricultural land from fertilisers and slurry. The robust sourcing of these pollutants is important to be able to target the appropriate sector and to engage the corresponding managers. Biomarker technology has the potential to do this, particularly the biomarker suite of sterols. Sterols have been used in the differentiation of human and animal faeces; however, there is no unequivocal techniqueregarding their analysis. Some of the methods used include: Soxhlet extraction, Bligh andDyer (BD) extraction, and accelerated solvent extraction (ASE). Whilst all have theirinherent advantages and disadvantages, the less costly and time intensive technique of ASE is particularly attractive, but a current research gap concerns further comparisons regarding lipid extraction of soils/slurries compared with the more traditionally used methods of Soxhlet and BD extraction. Such a comparison has recently been undertaken in conjunction with a Teagasc Walsh Fellowship PhD studentship exploring the development of robust chemical methodologies and their correlation with conventional water quality datasets for confirming incidental transfers of farm slurries to watercourses. 5'