Geochemical Fractionation of Phosphorus in Soils from the Margins of the Billings Reservoir

• Grant number: 25/13841-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: December 01, 2025
• End date: November 30, 2026
• Field of knowledge: Physical Sciences and Mathematics - Geosciences
• Principal Investigator: Diego Barcellos
• Grantee: Larissa Aparecida dos Santos
• Host Institution: Instituto de Ciências Ambientais, Químicas e Farmacêuticas (ICAQF). Universidade Federal de São Paulo (UNIFESP). Campus Diadema. Diadema , SP, Brazil

Abstract

The Billings Reservoir, located in the Metropolitan Region of São Paulo (Brazil), faces severe water and soil quality degradation due to intense urbanization and the influx of domestic and industrial effluents. Despite its importance, data related to phosphorus (P) dynamics and comprehensive spatial studies on water quality and the geochemistry of soils and surface sediments in this reservoir are still limited. Excess phosphorus is one of the main drivers of eutrophication, affecting biodiversity and the environmental health of water resources and soils. To better understand the P biogeochemical cycle and its potential environmental impacts in the reservoirs, it is essential to quantify its content and analyze its fractions in soils, which can either release or retain P. The aim of this study is to characterize the geochemical fractions of P in soils along the margins of the Alvarenga branch of the Billings Reservoir, comparing areas with or without the influence of effluents. Soil samples will be collected at different depths and distances from the waterline, including both aerated and waterlogged soils, which exhibits different redox conditions that impact the geochemical dynamics of P. Geochemical fractionation of P will be conducted for these soils into six distinct fractions, as follows: soluble and exchangeable P (PEx), P associated with reducible iron (Fe) and manganese (Mn) oxyhydroxides (PFeMn), P associated with silicates and aluminum hydroxide (PSiAl), P associated with humic acids (PAH), P associated with apatite (PCa), and residual P (Pres). The results will allow the evaluation of P bioavailability and mobility in soils, contributing to the understanding of this nutrient's dynamics in the environment and supporting remediation efforts and public policies aimed at preserving the region's environmental resources. (AU)