Detailing nitrogen transformations in aquifers through sinchrotron-based X-ray micro and nanotomography

• Grant number: 24/16743-7
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Start date: March 01, 2025
• End date: May 31, 2029
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geology
• Principal Investigator: Ricardo César Aoki Hirata
• Grantee: Lívia de Almeida Freitas
• Host Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 20/15434-0 - SACRE: integrated water solutions for resilient cities, AP.TEM

Abstract

Nitrate contamination is an insidious problem that affects practically all aquifers in São Paulo, which are responsible for the total or partial public water supply of 80% of its municipalities. Although this topic has been studied for more than two decades, there is still no clear understanding of which mechanisms (e.g., biological, chemical, natural or anthropogenic) control nitrogen species in groundwater. One of them involves N2O, the main ozone-depleting gas in the atmosphere and a dangerous greenhouse gas, generated by the processes of denitrification and, to a lesser extent, by nitrification. This direct doctoral project is *pioneering* in using the X-ray micro and nanotomography technique to analyze and characterize the porous medium in rocks that make up the Bauru Aquifer System (SAB), originating from boreholes drilled in a contaminated area in the city of Bauru (SP). To this end, the following activities are expected to be carried out: i) selection of the area for drilling a borehole; ii) collection and analysis of sediment/rock samples at depth; iii) preparation of undisturbed samples for characterization of the porous medium at microscale and chemical analysis; iv) segmentation and quantification of properties of the pore space, matrix and particulate organic matter. The results will allow establishing a relationship between the petrophysical properties, at pore scale, and the existing hydrogeochemical and microbiological information, which are related to nitrification and denitrification reactions (production and emission of N2O), enabling scientific advancement on the subject and subsidizing public policies for managing contamination of urban aquifers in the state of São Paulo.