The influence of bedrock hydrogeology on catchment-scale nitrate fate and transport in fractured aquifers

Abstract

12Characterising catchment scale biogeochemical processes controlling nitrate fate in groundwater 13 constitutes a fundamental consideration when applying programmes of measures to reduce risks 14 posed by diffuse agricultural pollutants to water quality. Combining hydrochemical analyses with 15 nitrate isotopic data and physical hydrogeological measurements permitted characterisation of 16 biogeochemical processes influencing nitrogen fate and transport in the groundwater in two 17 fractured bedrock aquifers with contrasting hydrogeology but comparable nutrient loads. bedrock conditions need to be considered when implementing catchment management plans to 7 reduce the impact of agricultural practices on the quality of groundwater and baseflow in receiving 8 rivers. 9 10 Nitrate isotopic signatures in the groundwater of a freely draining catchment underlain by a 11 karstified aquifer and a poorly draining aquifer with a low transmissivity aquifer.

Real‐Time Monitoring and Postprocessing of Thermal Infrared Video Images for Sampling and Mapping Groundwater Discharge

“…Because the annual thermal variability of groundwater generally decreases with depth (Briggs et al., 2018; Hare et al., 2021; Kurylyk et al., 2015; Taniguchi, 1993), the temperature of a spring should be useful for inferring its source at many sites away from the equator. Deep and shallow groundwater flows also tend to have different solute concentrations (Burns et al., 1998; Condon et al., 2020; Iwasaki et al., 2015; Orr et al., 2016). Although the different sources may have a homogeneous temperature if they are from similar depths or deeper than the isothermal layer, the coexistence of multiple groundwater types with different temperatures and chemistries at Site S (Figure 2 and Figure S7 in Supporting Information ) demonstrates that there are cases where TIR data are effective at inferring groundwater discharge sources.…”

Hydrogeophysical Characterization of Fractured Aquifers for Groundwater Exploration in the Federal District of Brazil

“…Therefore, these hydrogeological features are the potential site for groundwater development. These heterogeneous hydrogeological settings can also (i) influence the nitrate contamination transport and its fate by biogeochemical mechanisms [26], and (ii) increase the vulnerability of aquifers from surficial contaminates. These structures may outcrop at the ground and provide a pathway for contaminant transport.…”

“…These structures are recommended for future detailed investigations that may include the application of integrated geophysical techniques followed by geotechnical investigations and then finally the installation of pumping wells at the site. These features have been documented in numerous previous studies [8,10,[23][24][25][26][27][28][29][30]. A common contour interval and respective color scale are chosen for all the resistivity inversion models.…”

Nitrate reduction potential of a fractured Middle Triassic carbonate aquifer in Southwest Germany

“…While natural organic matter (NOM) is the most common electron donor for (heterotrophic) denitrification in shallow alluvial aquifers (Smith and Duff 1988;Zarnetske et al 2011), ferrous iron [Fe(II)] and reduced sulfur [S(-I)] bearing minerals such as pyrite were found to dominate (autotrophic) denitrification in aquifers with low amounts and limited bioavailability of NOM. This includes fractured aquifers in carbonate rocks (Baker et al 2012;Kim et al 2016;Opazo et al 2016), and crystalline bedrock (Pauwels et al 2000;Orr et al 2016), but also porous aquifers (e.g., Schwientek et al 2008;Zhang et al 2013). The presence of denitrifying microorganisms within fractured carbonate aquifers was confirmed by studies investigating microbial communities in the major conduit and fracture network (Farnleitner et al 2005;Jakus et al 2021) or attached to the limestone rock matrix (Herrmann et al 2017;Starke et al 2017).…”