Sediments accumulated in sewer settling basins as recorders of historical use of drugs: Potential and limitations.

This study assesses the occurrence of various types of drugs in a sedimentary archive cored in a sewer settling basin with a depth of 14 m. The coring operations were conducted before the basin was drained. A 2.2-m long sedimentary core was recovered. The sediments consisted of successions of coarse minerals and coarse or fine organic layers. One of the main challenges is to be able to date such a very recent archive. This was realized by using an event-based approach with 19 ¹⁴C Carbon dating out of the rising and decay phase of atmospheric ¹⁴C content linked to the aerial explosion of thermonuclear bombs (bomb peak). The first results revealed the potential of these sediments to record diverse contaminants. Eighteen of the 20 molecules targeted were quantified at least once. The potential of such archives to record the first use of each drug in the city is questioned, as well as the potential of back-calculated drug consumption on the basis of sedimentary occurrences. The estimated wastewater concentrations fit quite well for some molecules, whereas further work remains necessary for other drug values, especially concerning the back-calculation parameters.