| Title | Groundwater-dependent ecosystems in agro-environments of the Po valley (Italy): their role in the nitrogen cycling. |
| Abstract | The most spread groundwater-dependent ecosystems (GDEs) in the River Po valley are semi-natural lowland springs called "fontanili". They are biotopes where groundwater emerges spontaneously mainly due to the decrease in the permeability of alluvial sedimentary deposits in the transition zone between the higher and the lower plain. In the higher plain of Lombardy (Northern Italy), the concentration of nitrates in groundwater often exceeds the regulatory limits (50 mg L-1). Due to agricultural practices, the N excess is leached to the subsoil and is therefore subtracted from the shallow environment. However, this sink is only temporary, since the fontanili return the deep groundwater, partially mixed with recently infiltrated irrigation water, and the associated nutrients back to the surface water compartment. The available data on the chemistry of the fontanili reveals high NO3 concentration commonly in the range of 10-25 mg L-1. Within the INTEGRON project (Squaring the cycle: the INTEgration of GROundwater processes in Nutrient budgets for a basin-oriented remediation strategy) the N flux re-cycled from groundwater to surface water was estimated by an extensive seasonal monitoring of the nutrient concentrations and discharge in 50 fontanili from the catchments of Ticino and Adda rivers. The role of riparian strips and aquatic macrophytes in reducing the N contamination was studied by field campaigns in plots equipped with piezometer nests and by nutrient addition experiments. The nitrate removal effectiveness showed a large variation between the studied riparian areas including sites where we did not observe any reduction and locations where a complete NO3 depletion always occurred. Some useful predictors of the nitrate removal capacity were factors linked to the water residence time (e.g. the hydraulic conductivity, the soil texture and the slope of the riparian profile) together with the water table depth and soil organic carbon. Furthermore, our results demonstrate that the presence of instream vegetation, together with associated biological communities, provides a considerably higher nutrient retention. Despite the chronic high NO3 loading, the biota responds efficiently to variations in the relative availability of NH4 and PO4, and this suggests that some aspects of ecosystem functionality are maintained relatively intact when macrophytes can grow. Lastly, specific recommendations are made for improving the management practices in the Po valley in order to maximize the potential ecosystem services offered by the secondary hydrographic network. |
| Source | 6th ISRS Symposium "Riverine landscapes as coupled socio-ecological systems", Vienna, 9-13 settembre 2019 |
| Keywords | nitrateriparian stripsmacrophytedischarge |
| Year | 2019 |
| Type | Abstract in atti di convegno |
| Authors | Raffaella Balestrini(1), Carlo Andrea Delconte(1), Elisa Sacchi(2), Andrea Buffagni(1, 3) Presenting author: Raffaella Balestrini |
| Text | 427656 2019 nitrate riparian strips macrophyte discharge Groundwater dependent ecosystems in agro environments of the Po valley Italy their role in the nitrogen cycling. Raffaella Balestrini 1 , Carlo Andrea Delconte 1 , Elisa Sacchi 2 , Andrea Buffagni 1, 3 Presenting author Raffaella Balestrini 1 Water Research Institute, National Research Council CNR IRSA , Via del Mulino 19, I 20861 Brugherio, MB, Italy 2 Department of Earth and Environmental Sciences, University of Pavia, via Ferrata 1, 27100 Pavia, Italy 3 Dipartimento di Scienze Ecologiche e Biologiche, Universita della Tuscia, Viale dell Universita s.n.c., I 01100 Viterbo, Italy Published version 6th ISRS Symposium Riverine landscapes as coupled socio ecological systems Vienna 9 13 settembre 2019 Internazionale Contributo The most spread groundwater dependent ecosystems GDEs in the River Po valley are semi natural lowland springs called fontanili . They are biotopes where groundwater emerges spontaneously mainly due to the decrease in the permeability of alluvial sedimentary deposits in the transition zone between the higher and the lower plain. In the higher plain of Lombardy Northern Italy , the concentration of nitrates in groundwater often exceeds the regulatory limits 50 mg L 1 . Due to agricultural practices, the N excess is leached to the subsoil and is therefore subtracted from the shallow environment. However, this sink is only temporary, since the fontanili return the deep groundwater, partially mixed with recently infiltrated irrigation water, and the associated nutrients back to the surface water compartment. The available data on the chemistry of the fontanili reveals high NO3 concentration commonly in the range of 10 25 mg L 1. Within the INTEGRON project Squaring the cycle the INTEgration of GROundwater processes in Nutrient budgets for a basin oriented remediation strategy the N flux re cycled from groundwater to surface water was estimated by an extensive seasonal monitoring of the nutrient concentrations and discharge in 50 fontanili from the catchments of Ticino and Adda rivers. The role of riparian strips and aquatic macrophytes in reducing the N contamination was studied by field campaigns in plots equipped with piezometer nests and by nutrient addition experiments. The nitrate removal effectiveness showed a large variation between the studied riparian areas including sites where we did not observe any reduction and locations where a complete NO3 depletion always occurred. Some useful predictors of the nitrate removal capacity were factors linked to the water residence time e.g. the hydraulic conductivity, the soil texture and the slope of the riparian profile together with the water table depth and soil organic carbon. Furthermore, our results demonstrate that the presence of instream vegetation, together with associated biological communities, provides a considerably higher nutrient retention. Despite the chronic high NO3 loading, the biota responds efficiently to variations in the relative availability of NH4 and PO4, and this suggests that some aspects of ecosystem functionality are maintained relatively intact when macrophytes can grow. Lastly, specific recommendations are made for improving the management practices in the Po valley in order to maximize the potential ecosystem services offered by the secondary hydrographic network. Abstract in atti di convegno carloandrea.delconte DELCONTE CARLO ANDREA raffaella.balestrini BALESTRINI RAFFAELLA andreastefano.buffagni BUFFAGNI ANDREA STEFANO |
