DOC and nitrate fluxes from farmland; impact on a dolostone aquifer KCZ

Abstract

DOC and nitrate in farmland represent key chemical species that determine the water quality in the Karst Critical Zone (KCZ). The work reported here focuses on quantifying fluxes of these species in an experimental farm site (University of Leeds Farm, UK) overlying a dolomitic karst aquifer of Permian age. In this research, the Transect Method was applied for the first time to farmland by combining hydrochemical data from soil and groundwater for computation of mass fluxes. The Transect Method, developed for management of industrially contaminated sites, was applied to a farm source due to the presence of localised contamination from application of pig slurry.Required inputs for our approach include concentrations of nitrate and DOC in soil water and groundwater, net recharge flux (here derived from a MODFLOW-2005 model) and local hydraulic gradient and conductivity measurements. Key outputs are fluxes and downstream groundwater concentrations of DOC and nitrate. Downstream concentrations were validated against direct groundwater measurements, demonstrating the veracity of the approach. The approach shows that the localised contamination has a significant impact on both concentrations of nitrate and DOC in groundwater, although the DOC impact is greater, because the upstream land uses also produce nitrate as a result of agricultural practices that are widespread in the region.The results of the study also constrain the zone vulnerable to contamination to the upper ~40 m below the ground surface. Future modelling efforts on solute contaminant transport should focus on this shallow vulnerability zone (0-40 mBGL) and the Transect Method applied in this work can be used to define boundary conditions. Hence, following this research, we envisage to export a generic approach that combines physical flow parameters and hydrochemical analyses for computation of subsurface mass fluxes using the Transect Method, to identify the degree of impact of specific point sources and to support conceptualization and modelling of contaminant transport in the KCZ of farm areas.

Historical analysis of a karst aquifer: recharge, water extraction, and consumption dynamics on a tourist island (Cozumel, Mexico)

“…These characteristics favour the channeling, storage and infiltration of rainwater in the north-central zone where UGA C1 is located, in addition to being the location of the greatest freshwater lens on the island. However, high permeability of karstic systems also increases vulnerability to pollutant infiltration and does not prevent issues from over extraction like seawater intrusions (Medici et al, 2019(Medici et al, , 2020.…”

“…Cozumel is the third largest island in Mexico and the most populated island, located in the southeastern State of Quintana Roo, where the drinking water supply depends on the aquifer recharged only by rain (Gutiérrez-Aguirre et al, 2008). Like in many other karstic nature islands, rainwater rapidly infiltrates into the aquifer, although they are highly vulnerable to pollution infiltration and water scarcity (Medici et al, 2019(Medici et al, , 2020. Vulnerability is an intrinsic property of karstic island aquifers, which depends on characteristics of the area and the sensitivity of the system to human and natural impacts (Ducci and Sellerino, 2013;Kačaro glu, 1999;Medici et al, 2021), such as wastewater infiltration, hurricanes and saltwater intrusions.…”

Review of Modeling Approaches to Groundwater Flow in Deformed Carbonate Aquifers

“…In these areas, stress on groundwater resources is much higher due to high population densities, which necessitate intense industrial and agricultural activities. Thus, a range of pollutants such as nitrate, sulfate, chloride, pathogens, toxic organic compounds released by mineral fertilizers and pesticides can reach the saturated parts of these aquifers in regions, which are devolved to industry and agriculture (Bales et al 1989;Göppert and Goldscheider 2008;Mahler and Garner 2009;Petitta et al 2009Petitta et al , 2018Musgrove et al 2014;Zhang et al 2019;Medici et al 2020). Additionally, carbonate aquifers represent the principal source of water for major capital cities such as Doha, Beijing, London, Rome, and Vienna (Maloszewski et al 2002;Worthington and Gunn 2009;Ford and Williams 2013;Hartmann et al 2014aHartmann et al , 2014bWorthington 2015).…”

An Integrated Modeling System for the Evaluation of Water Resources in Coastal Agricultural Watersheds: Application in Almyros Basin, Thessaly, Greece

“…Hence, research must be done in the direction of the development of efficient software and tools that take into account the impacts of water abstractions, the water balance deficit, the nitrate leaching, the nitrate pollution, and the seawater intrusion [18][19][20][21]. Until recently, most of the hydrological processes and human interactions either for surface water resources [22] or groundwater [23], or under climate change [6] or land uses [24], or landscape and population changes [25] are often studied separately.…”