Environmental forensics studies for nitrate source determination (NSD) have seen increased interest in recent years. To date, nitrate stable isotopes have mainly been used for this purpose. However, they are unable to characterize sewage and manure inputs or multiple sources of nitrate within a sample. However, they are unable to differentiate sewage and manure sources in surface waters. This differentiation is especially important as human-health risks are higher from human, than animal, faecal contamination. To address such shortcomings, human and veterinary pharmaceuticals were exploited as co-occurring sewage and manure discriminators. For this reason an analytical suite of 10 chemical markers (10 human and 4 veterinary) was developed. Through an understanding of their use, occurrence and fate allows further source characterization, e.g. between raw and treated sewage, could be achieved. Pharmaceutical analysis has traditionally been carried out using SPE-LC-MS/MS techniques. Therefore, a single method has been developed and validated for the analytical suite at detection limits of up to 50 pg/L. Its application to monitoring sites within Ireland reveals raw sewage infiltration at upstream sites, which has been attributed to septic tank inputs, a topical concern in Ireland. However, despite the advantages of using chemical markers, SPE-LC-MS/MS is costly and time intensive. Hence, the potential of the novel application of alternative analytical techniques has been explored, as complementary methods to LC-MS/MS. In particular, the use of immunoassays, which are also suitable for inclusion on lab-on-a-chip systems, resulted in limits of detection that are relevant to low-level contamination of surface waters and comparable to those achieved using SPE-LC-MS/MS.

Analytical techniques for the differentiation of sewage and manure inputs to surface waters

246th National Meeting (2013)

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