The increase of intensive agriculture and animal farming has resulted in the extensive application of organic and chemical fertilizers in soils. This utilization has led to the release of diverse chemical pollutants into the soil, which are then transported into the water table through the leaching action of rainwater. Despite the implementation of strict regulations specified in the Nitrate Directive, there has been no noticeable improvement in groundwater quality within numerous Nitrates Vulnerable Zones. Our study location, the plain of Arborea (Sardinia), has been identified as a NVZ since 2005, and this phenomenon is clearly observable there. The unsaturated zone regulates the flow of water and the leaching of contaminants, depending on soil characteristics and infiltration rate. Consequently, the research aimed to evaluate the processes involved in nitrate degradation and natural attenuation mechanisms during infiltration and transport through the unsaturated zone. In the plain, an agricultural field was chosen as a pilot site, in which a monitoring system of the unsaturated zone was set up to obtain information on the processes taking place in the soil. TDR probes were installed to measure the volumetric water content, while suction cups were placed at different depths to sample pore water for analysis of ionic nitrogen species and nitrate isotopes. Soil samples were collected every 10 cm along a vertical profile to determine their stable water isotope ratios and through the peak-shift method with the assumption of the piston displacement method to evaluate the time lag between infiltration and water table attainment. The monitoring of the unsaturated zone coupled with the determination of travel time, contribute to the understanding of the processes occurring in the transported solutes and are an effective tool for the reduction of their leaching into groundwater and for the optimization of agricultural practices.
Assessment of the nitrate transformation processes during infiltration and transport in the unsaturated zone
Francesca Lobina
Primo
;Stefania Da Pelo;Antonio Coppola;Andrea Vacca;Riccardo Biddau;Claudio Arras;Maria Chiara Porru
2024-01-01
Abstract
The increase of intensive agriculture and animal farming has resulted in the extensive application of organic and chemical fertilizers in soils. This utilization has led to the release of diverse chemical pollutants into the soil, which are then transported into the water table through the leaching action of rainwater. Despite the implementation of strict regulations specified in the Nitrate Directive, there has been no noticeable improvement in groundwater quality within numerous Nitrates Vulnerable Zones. Our study location, the plain of Arborea (Sardinia), has been identified as a NVZ since 2005, and this phenomenon is clearly observable there. The unsaturated zone regulates the flow of water and the leaching of contaminants, depending on soil characteristics and infiltration rate. Consequently, the research aimed to evaluate the processes involved in nitrate degradation and natural attenuation mechanisms during infiltration and transport through the unsaturated zone. In the plain, an agricultural field was chosen as a pilot site, in which a monitoring system of the unsaturated zone was set up to obtain information on the processes taking place in the soil. TDR probes were installed to measure the volumetric water content, while suction cups were placed at different depths to sample pore water for analysis of ionic nitrogen species and nitrate isotopes. Soil samples were collected every 10 cm along a vertical profile to determine their stable water isotope ratios and through the peak-shift method with the assumption of the piston displacement method to evaluate the time lag between infiltration and water table attainment. The monitoring of the unsaturated zone coupled with the determination of travel time, contribute to the understanding of the processes occurring in the transported solutes and are an effective tool for the reduction of their leaching into groundwater and for the optimization of agricultural practices.
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