[A-HW18] 流域圏生態系における物質輸送と循環：源流から沿岸海域まで

[AHW18-06] Use of Nature-Based Solutions (SbN) for improving the quality of contaminated groundwater by urban nutrients

★Invited Papers

*Reginaldo Antonio Bertolo¹、Vinicius Rogel P Oliveira¹、Priscila Ikematsu²、Tatiana Luís Tavares²、Shin-ichi Onodera³、Mitsuyo Saito³、Ricardo Hirata¹ (1.Groundwater Research Center - University of Sao Paulo - Brazil、2.Technological Research Institute - IPT、3.Hiroshima University)

キーワード：groundwater pollution, Nature-based Solutions, phytoremediation, nitrate, nutrients

Contamination of aquifers by nitrate is quite common in Brazilian urban areas. The origin of the contamination is usually related to leaks from the pipelines of the urban sewage network installed in the subsurface. The result is that shallow aquifers normally have concentrations above standard limits for nitrate and other nutrients, often causing the loss of public supply wells installed in the impacted aquifer. The remediation of the impacted groundwater, as well as the identification of pollution sources in the sewage network, represent complex tasks, as they commonly involve high-cost engineering solutions. Nature-based solutions (SbN) are measures that mimic the natural processes of forest ecosystems and that have great potential for improving the environmental quality of polluted environments, as they are of lower costs, easy to apply and promote the generation and maintenance of valuable ecosystem services. One type of SbNs known worldwide is phytoremediation, which integrates services between microorganisms and plants to extract and degrade contaminants in soils and waters. It is observed that studies addressing phytoremediation by native species in the Atlantic Forest and Cerrado biomes in Brazil are incipient, with the aim of recovering soils and shallow aquifers contaminated by nutrients. In this context, this project aims to identify, on a pilot scale, the efficiency and potential of phytoremediation in improving the quality of water contaminated by domestic effluents, from a native forest ecosystem. Therefore, it is expected that the studies will lead to the understanding of geochemical and microbiological processes and transformations of the different nitrogen species in the groundwater of the unsaturated zone of the aquifer. The experiment is being carried out in the city of Bauru, in the State of São Paulo (Brazil), which faces problems of groundwater quality due to nitrate, in parallel with problems of water scarcity. The main stages of the work correspond to: (i) the selection of an experimental area in a forest, involving botanical, edaphic and hydrogeological characterizations; (ii) the installation of adequate instrumentation in an experimental station for the investigation of the unsaturated zone and groundwater aquifer (digital tensiometers, suction lysimeters, monitoring wells); (iii) carrying out monitoring to assess the background conditions of water quality in the unsaturated and saturated zones over a hydrological year; (iv) infiltration of water contaminated by sewage on the surface of the experimental station by dripping; (v) monitoring the effects of infiltration in the forest system, based on the investigation of chemical, isotopic (d¹⁵N, d¹⁸O, d²H) and biological parameters in soil solution, groundwater and plant fertility. The results obtained in the pilot project will be incorporated into a numerical model of reactive flow and transport to evaluate the role of urban green areas in improving the quality of groundwater, providing subsidies to define strategies for remediation of aquifers contaminated by effluents rich in nutrients by through the use of SbNs. The authors thank the São Paulo Research Foundation (FAPESP) for supporting the Project SACRE (grant 2020/15434-0) and CNPq (grant 423950/2021-5).