Use of multi-tracers, nanotechnology and numerical modeling of geochemical multicomponent reactive transport to assess nitrate in urban aquifers

Abstract

Nitrate contamination is almost ubiquitous in urban unconfined aquifers, becoming a challenge for the São Paulo State where more than 80% of its municipalities are supplied totally or partially by groundwater. Despite the several existing studies, there are critical scientific challenges that overcoming will contribute to the environmental management of extensive contaminated urban areas. There is not yet sufficient understanding to establish in which situations nitrogen species will degrade aquifers and which effective biogeochemical mechanisms, natural or anthropogenic, cause the greater or lesser extent of the problem. Recently, advanced research groups have suggested the joint use of new tools, which would integrate with traditional hydrogeochemical techniques, including multi-tracer (CFCs, SF6, 39Ar, 14C, 11B, 15N, 18ONO3, 87Sr/86Sr, artificial sweeteners), microbiology (16S rRNA, narG, napA, nirS, nirK, norB, nosZ genes), nanotechnology (synchrotron-based high resolution and time-resolved X-ray imaging) and numerical modeling of multicomponent reactive transport. The proposal of this study is to apply, in a pioneering way, these tools in a very detailed study in a contaminated area in the city of Bauru (SP). For this purpose, the following activities are planned: I) registration and treatment of previous data; II) determination of BAS flow conditions; III) reassessment of previous and recent nitrate concentrations; V) installation of multi-level monitoring wells; IV) sampling for physicochemical, chemical, isotopic, gas, microbiological, artificial sweetener analyses of surface water, groundwater, rainwater, and wastewater samples; V) collection of sediment/rock samples for porous media characterization and chemical, microbiological, isotopic and nanotechnology analyses; VI) numerical modeling of groundwater flow and reactive nitrate transport. Thus, it is expected that the understanding of the nitrogen dynamics in the subsurface and the factors that control it will subsidize public policies for the management of urban contamination, reducing the health risk to millions of urban groundwater users in the State of São Paulo. (AU)