Riparian Zones as Biogeochemical Filters: Attenuating Nitrogen Loads in Brazilian Urban Aquifers.

This poster presents findings on the biogeochemical filtration capacity of riparian zones in urban aquifers in Bauru City, Brazil. It examines how historical urbanization and the high permeability of the unconfined Bauru Aquifer System (BAS) have led to the degradation of shallow water quality through urban recharge.The research illustrates how the shallow BAS acts as an aerobic oxidative reactor, nitrifying sewage and resulting in nitrate concentrations that frequently violate drinking water standards. Furthermore, the study identifies that the riparian zone's denitrification capacity has been overwhelmed, acting as a "leaky filter" for contaminants reaching the Bauru River.Key methodologies included the analysis of major ions, nitrogen species (including Norg, Ntotal, NO3, NH4+), and microbiological indicators (E. coli) across surface water, shallow groundwater, and regional groundwater horizons during wet and dry seasons.The results provide evidence of vertical hydrogeological isolation protecting the deep Guarani Aquifer System (GAS), while highlighting the urgency of sanitation interventions to address the surface water contamination driven by groundwater discharge.