| Title | Factors affecting agricultural nitrogen removal in riparian strips: Examples from groundwater-dependent ecosystems of the Po Valley (Northern Italy) |
| Abstract | The role of riparian ecosystems in mitigating the effects of diffuse agricultural sources is recognized in
several regulatory measures and public policy initiatives in many parts of the world. This study aimed to
evaluate the N buffering capacity of semi-natural riparian zones associated with spring-fed lowland
streams, also known as "fontanili", representing the most important groundwater-dependent
ecosystems in Northern Italy. Monitoring parcels were set up in nine riparian sites selected to cover
a range of different soil properties and hydrogeological settings, and to sustain the evaluation of the main
drivers affecting their N removal efficiency. Subsurface water level, nutrient concentrations and the main
hydro-chemical parameters were monitored along transects of piezometers installed from crop
fields to the spring channels. On selected samples from two sites stable isotopes of the water molecule were also
determined. Median NO3 input concentrations from adjacent cropland to the riparian sites ranged from
0.10 to 21 mg N L1, with maximum values exceeding the drinking water limit recorded during the
summer and winter fertilization periods. Highly variable groundwater nitrate patterns were found in the
riparian areas, including short nitrate plumes extending from the adjacent cropland into some riparian
zones, or in others, small patches where NO3 declined at variable distance from the stream. Some
chemical indicators (e.g., NO3 /Cl ratio, O2, DOC) suggested that NO3 attenuation was mostly due to the
denitrifying activity occurring in the subsurface aquifers in specific conditions (hot spots and moments),
although, in some cases, physical processes such as dilution also contributed. The overall N removal
efficiency was greater than 90% in four sites, 74%, 34% and 30% in three sites, and zero in the remaining
two sites. Useful predictors of the nitrate removal capacity were factors linked to the water residence
time, such as the hydraulic conductivity, the soil texture and the slope of the riparian profile, together
with the water table depth and soil organic carbon. A combination by standardized averaging of these
five factors supported a clear discrimination of sites with zero or low N removal effectiveness from those with
high efficiency. |
| Source | Agriculture, ecosystems & environment (Print) 221, pp. 132–144 |
| Keywords | NitrateDenitrificationHydrologyTopographySoil Isotopes |
| Journal | Agriculture, ecosystems & environment (Print) |
| Editor | Elsevier, Amsterdam, Paesi Bassi |
| Year | 2016 |
| Type | Articolo in rivista |
| DOI | 10.1016/j.agee.2016.01.034 |
| Authors | Balestrini R., Sacchi E., Tidili D., Delconte C.A., Buffagni A. |
| Text | 346637 2016 10.1016/j.agee.2016.01.034 ISI Web of Science WOS 000373649100015 Scopus 2 s2.0 84956681114 Nitrate Denitrification Hydrology Topography Soil Isotopes Factors affecting agricultural nitrogen removal in riparian strips Examples from groundwater dependent ecosystems of the Po Valley Northern Italy Balestrini R., Sacchi E., Tidili D., Delconte C.A., Buffagni A. Water Research Institute, National Research Council CNR IRSA , Via del Mulino 19, 20861 Brugherio, MB, ItalyDepartment of Earth and Environmental Sciences, University of Pavia and CNR IGG, U.O.S. of Pavia, via Ferrata 1, 27100 Pavia, Italy The role of riparian ecosystems in mitigating the effects of diffuse agricultural sources is recognized in several regulatory measures and public policy initiatives in many parts of the world. This study aimed to evaluate the N buffering capacity of semi natural riparian zones associated with spring fed lowland streams, also known as fontanili , representing the most important groundwater dependent ecosystems in Northern Italy. Monitoring parcels were set up in nine riparian sites selected to cover a range of different soil properties and hydrogeological settings, and to sustain the evaluation of the main drivers affecting their N removal efficiency. Subsurface water level, nutrient concentrations and the main hydro chemical parameters were monitored along transects of piezometers installed from crop fields to the spring channels. On selected samples from two sites stable isotopes of the water molecule were also determined. Median NO3 input concentrations from adjacent cropland to the riparian sites ranged from 0.10 to 21 mg N L1, with maximum values exceeding the drinking water limit recorded during the summer and winter fertilization periods. Highly variable groundwater nitrate patterns were found in the riparian areas, including short nitrate plumes extending from the adjacent cropland into some riparian zones, or in others, small patches where NO3 declined at variable distance from the stream. Some chemical indicators e.g., NO3 /Cl ratio, O2, DOC suggested that NO3 attenuation was mostly due to the denitrifying activity occurring in the subsurface aquifers in specific conditions hot spots and moments , although, in some cases, physical processes such as dilution also contributed. The overall N removal efficiency was greater than 90% in four sites, 74%, 34% and 30% in three sites, and zero in the remaining two sites. Useful predictors of the nitrate removal capacity were factors linked to the water residence time, such as the hydraulic conductivity, the soil texture and the slope of the riparian profile, together with the water table depth and soil organic carbon. A combination by standardized averaging of these five factors supported a clear discrimination of sites with zero or low N removal effectiveness from those with high efficiency. 221 Published version 21/01/2016 Factors affecting agricultural nitrogen removal in riparian strips Examples from groundwater dependent ecosystems of the Po Valley Northern Italy AgEE2016.pdf Articolo in rivista Elsevier 0167 8809 Agriculture, ecosystems environment Print Agriculture, ecosystems environment Print Agric. ecosyst. environ. Print Agriculture, ecosystems environment. Print Agriculture, ecosystems and environment Print elisasacchi SACCHI ELISA carloandrea.delconte DELCONTE CARLO ANDREA raffaella.balestrini BALESTRINI RAFFAELLA andreastefano.buffagni BUFFAGNI ANDREA STEFANO TA.P04.032.001 Funzionalita degli ecosistemi acquatici dinamica dei nutrienti, idromorfologia e habitat fluviali |
