Extended Geochemical Observation of Urban Trajectories – EGOUT

Greywaters as new source of information for urban planning
There is an increasing interest in public health monitoring through Wastewater-Based Epidemiology (WBE). This approach relies on the hypothesis that concentration of human-excreted materials (i.e. pharmaceuticals, drugs, pathogens…) in wastewater can give clue information on health status of people living in the catchment. The spectrum of potential tracers (and thus questions to address) is enlarged by recent progress in mass spectrometry for non-targeted analyses, allowing quantitation of yet non-identified compounds for which, obviously, the source remains to be elucidated. Although WBE has proven its efficiency for health issues, there is currently a consensus on the under-exploitation of sewer-based data and the emergence of new initiatives to expand the range of chemical and biological tracers of human activities. EGOUT plans to extend the range of indicators far beyond those related to health issues through ambitious Sewage Chemical-Information Mining (SCIM). Indeed, stormwater and wastewater in a combined sewer system carry a large diversity of potential geochemical indicators of which the temporal and spatial distributions allow addressing numerous issues such as health and well-being, demography, nutrition, environment, runoff from roads and from soils, urban design and buildings .

Sediments for mapping and temporal archiving
Geochemical heterogeneities in sediments accumulated in decantation tanks across the Paris sewer network are suspected to be related to differences in behaviour, practices, and urban management across the catchment. In parallel, sediment accumulations are precious archives to record human activities. By diverting geochemical/environmental diachronic approaches to the Anthropocene and to urban socio-ecosystems, EGOUT will lead to a disruption in conventional access to socio-economic information.

Which tracer for which practice?
The diversity and complexity of tracers in waters that circulate and in sediments that accumulate in sewer networks afford a rather infinite set of potential tracers of diverse origins, attesting to various processes, and related to distinct topics that are abundantly described in the literature. In order to minimize risks, we will first take advantage of well-established geochemical tracers that are socio-economically relevant, as demonstrated by Choi et al. (2020). Then, we will explore more innovative geochemical tracers developed by partners (emerging contaminants, HRMS fingerprints, isotopes) and susceptible of providing complementary information. The targeted tracers will be co-defined based on partner's research questions and analytical capabilities, stakeholders’ concerns, and citizen propositions.

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Nutrition, health, well-being… How can we get policy relevant and multi-thematic information on the typology and evolution of urban systems? Polls, surveys, census and… sewers! Inspired by latests developments in Sewage Chemical-Information Mining, and consolidated by our recent successes, the EGOUT project aims at developing an objective, reactive and integrated observatory of the evolution of Paris by monitoring a large array of geochemical indicators and confront them to socio-economic metrics. We will produce maps of geochemical heterogeneities that will be analysed in the light of socio-economic. We will monitor the evolution of selected indicators to track socio-economic trajectories. Citizens, public policymakers and practitioner’s involvement will be ensured through a co-design and a participatory research action process.