『Abstract
Geochemical and isotope data collected in the agricultural area
of Fucino Plain, Central Italy provided information about the
relationship between the nitrate cycle and agricultural practices
and seasonal changes in hydrology, in particular concerning the
interaction between groundwater and surface water. The nitrate
cycle of the alluvial aquifer of the Plain has been summarized
in a seasonal-dependent conceptual model, where the shallow alluvial
aquifer plays a fundamental role contributing to contamination
of irrigation channels during periods of no manure application.
Based on isotopic fingerprinting, chemical characterization and
agricultural practices, the main nitrate source involved in the
nitrate cycle in the study area is manure that is applied during
the fall and winter periods. A nitrogen contribution from the
deep alluvial-lacustrine aquifer was also documented in this study.
The isotope data also showed the occurrence of denitrification
occurring in nitrate pools in the shallow aquifer, which is characterized
by low-permeability layers. The nitrate pool in the shallow aquifer
is related to infiltration after the application of manure. The
isotope and concentration data showed that the increase of nitrate
in the irrigation channels under non-runoff conditions is controlled
by seepage from the shallow aquifer. The cycle ends with a new
application of manure, generating considerable increases of “fresh”
nitrate concentration in the channels. The historical trend of
decreasing water table conditions and increasing nitrate content
in the shallow aquifer threatens the deep aquifer, used for drinking
purposes, since heavy pumping can induce the transport of nitrate
from the shallow aquifer toward the capture zone of the deep wells.
Keywords: Groundwater; Agriculture; Nitrate; Isotope geochemistry;
Denitrification』
Introduction
Study site
Hydrogeological setting
Materials and methods
Results and discussion
In situ measurements
Water chemistry and nitrogen compounds
Nitrogen chemistry
Environmental isotopes
Nitrate cycle and its relationship with the hydrogeological cycle
Final remarks
Acknowledgements
References