[A-HW22] 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

[AHW22-02] Native tropical forest to treat contaminated urban rivers and increase groundwater availability in Brazil

*Vinicius Rogel Paulino de Oliveira^1,2、Priscila Ikematsu²、Reginaldo Antonio Bertolo¹、Leonardo de Andrade Capeleto^1,2、Tatiana Tavares³、Shin-ichi Onodera⁴、Mitsuyo Saito⁴、Ricardo Hirata¹ (1.Groundwater Research Center - University of Sao Paulo - Brazil、2.Technological Research Institute of the State of São Paulo、3.Goias Federal University、4.Hiroshima University)

キーワード：Water quality, Urban green areas, Environmental monitoring, Nature-based Solution

Surface and groundwater pollution is a significant concern in urban and rural areas in Brazil, where 48% of its population does not have a adequate sewage service, and 55% of the not treated waste waters released directly into rivers or infiltrated into septic tanks or pit latrines. Forests and riparian zones play a crucial role in providing ecosystem water services; but are still little used in developing countries, which require cheap and low-impact solutions to solve their contaminated river problems. This study evaluate native vegetation, such as species from the Atlantic Forest and Cerrado biomes, to treat contaminated rivers and increase water availability through managed aquifer recharge. Based on botanical, soil, and hydrogeochemical characterizations, three experimental stations were built in a riparian zone in Horto Florestal in Bauru (São Paulo state, Brazil). This region is characterized by a tropical climate, with humid summers and dry winters; rainfall of 1300 mm/y, and air temperatures of 23ºC. We constructed three stations with diameters of 1.20 m and depths of 6, 4, and 2 m, installed in vegetated areas and distributed in line and orthogonally to the river. The unsaturated zone is monitored by digital tensiometers, suction lysimeters, and gas samplers at different depths, with a focus on the root zone, up to 2.0 m. The saturated zone is monitored by a network of 17 wells (up to 12 m). Finally, the trench drain (riverbank filtration, RBF) with an area of 4 m² and 2 m deep collects water from a 5 m distance river . The experiment consists of pumping water collected in the RBF system and infiltrating it into the forest soil close to the stations, with flow rates of 10 mm/d during the dry season. The biogeochemical transformations of water in the respective compartments are being monitored. Water quality is monitored for major and minor ions, metals, nutrients, isotopes, and carbon and nitrogen gases in the unsaturated zone. Samples of the plant's leaf tissue are also analyzed. The results will feed numerical flow, transport, and geochemical models will allow us to understand how geochemical reactions are processed, and propose modifications in the water irrigation management to increase the efficiency of the water treatment and aquifer recharge. The authors would like to thank the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) for supporting the SACRE Project (grant 2020/15434-0) and CNPq (grant 423950/2021-5).