| Title | Nitrogen inputs to a river course in a heavily impacted watershed: A combined hydrochemical and isotopic evaluation (Oglio River Basin, N Italy). |
| Abstract | This study aims at evaluating sources and processes affecting NO3- concentrations in the Oglio River. Five sampling campaigns considered the main watercourse, tributaries, point pollution sources, springs, and groundwater. Physico-chemical parameters, N forms, B, Sr2 +, stable isotopes (?2HH2O, ?18OH2O, ?15NNO3, ?18ONO3, ?11B) and discharge were measured. Hydrological modelling was performed using mass balance and End Member Mixing Analysis equations. During the irrigation period, in the upstream reach, up to 90% of the natural river flow is diverted for irrigation and industrial purposes; excess water drained from agricultural fields is returned to river in the downstream reach. Results evidenced, in the middle reach, a large input of NO3--rich groundwater which could be quantified using hydrological modelling. Groundwater inputs are responsible for the sharp, tenfold increase in NO3- in the river water, from 2.2-4.4 up to 33.5 mg L- 1, and are more evident in summer, when discharge is lower. Nevertheless, river water preserves its natural B isotopic composition, indicating that the two tracers do not have a common origin and are not co-migrant. In the lower plain, surface-groundwater interconnections and human disturbances in the water cycle favour the recycling of the compounds in the environment, and lead to a similarity in composition of the different water bodies (Oglio River, tributaries and groundwater). The long lasting agronomical practices have profoundly modified the surface-groundwater equilibrium and chemical characteristics, resulting in a highly buffered system. Infiltrating irrigation water leaches down NO3- which is subsequently denitrified; when returned to the Oglio River, groundwater modifies the river water composition by dilution, in the case of NO3-, or by addition, for other constituents (e.g. Cl-, B). The results of this study indicate that, in order to reduce the NO3- transport towards the Adriatic Sea, groundwater contamination should be addressed first, with expected long recovery times. |
| Source | Science of the total environment 466-467, pp. 924–938 |
| Keywords | NO3- contaminationsurface-groundwater interactionstable isotopeshydrological modellingPo plain |
| Journal | Science of the total environment |
| Editor | Elsevier, Lausanne ;, Paesi Bassi |
| Year | 2014 |
| Type | Articolo in rivista |
| DOI | 10.1016/j.scitotenv.2013.07.092 |
| Authors | Delconte C. A.[1,2], Sacchi E.[1,2], Racchetti E.[3], Bartoli M.[4,5], Mas-Pla J.[4,5], Re, V.[6] |
| Text | 285170 2014 10.1016/j.scitotenv.2013.07.092 ISI Web of Science WOS 000330491600098 NO3 contamination surface groundwater interaction stable isotopes hydrological modelling Po plain Nitrogen inputs to a river course in a heavily impacted watershed A combined hydrochemical and isotopic evaluation Oglio River Basin, N Italy . Delconte C. A. 1,2 , Sacchi E. 1,2 , Racchetti E. 3 , Bartoli M. 4,5 , Mas Pla J. 4,5 , Re, V. 6 1 Institute of Geosciences and Earth Resources IGG , CNR, U.O.S. Pavia, Italy 2 Department of Earth and Environmental Sciences, University of Pavia, Italy 3 Department of Life Sciences, University of Parma, Italy 4 Department of Environmental Sciences, University of Girona, Spain 5 Catalan Institute for Water Research, Girona, Spain 6 Department of Molecular Sciences and Nanosystems, University Ca Foscari of Venice, Venezia, Italy This study aims at evaluating sources and processes affecting NO3 concentrations in the Oglio River. Five sampling campaigns considered the main watercourse, tributaries, point pollution sources, springs, and groundwater. Physico chemical parameters, N forms, B, Sr2 , stable isotopes 2HH2O, 18OH2O, 15NNO3, 18ONO3, 11B and discharge were measured. Hydrological modelling was performed using mass balance and End Member Mixing Analysis equations. During the irrigation period, in the upstream reach, up to 90% of the natural river flow is diverted for irrigation and industrial purposes; excess water drained from agricultural fields is returned to river in the downstream reach. Results evidenced, in the middle reach, a large input of NO3 rich groundwater which could be quantified using hydrological modelling. Groundwater inputs are responsible for the sharp, tenfold increase in NO3 in the river water, from 2.2 4.4 up to 33.5 mg L 1, and are more evident in summer, when discharge is lower. Nevertheless, river water preserves its natural B isotopic composition, indicating that the two tracers do not have a common origin and are not co migrant. In the lower plain, surface groundwater interconnections and human disturbances in the water cycle favour the recycling of the compounds in the environment, and lead to a similarity in composition of the different water bodies Oglio River, tributaries and groundwater . The long lasting agronomical practices have profoundly modified the surface groundwater equilibrium and chemical characteristics, resulting in a highly buffered system. Infiltrating irrigation water leaches down NO3 which is subsequently denitrified; when returned to the Oglio River, groundwater modifies the river water composition by dilution, in the case of NO3 , or by addition, for other constituents e.g. Cl , B . The results of this study indicate that, in order to reduce the NO3 transport towards the Adriatic Sea, groundwater contamination should be addressed first, with expected long recovery times. 466 467 http //www.journals.elsevier.com/science of the total environment/ Nitrogen inputs to a river course in a heavily impacted watershed A combined hydrochemical and isotopic evaluation Oglio River Basin, N Italy . DELCONTE.pdf Articolo in rivista Elsevier 0048 9697 Science of the total environment Science of the total environment Sci. total environ. elisasacchi SACCHI ELISA carloandrea.delconte DELCONTE CARLO ANDREA TA.P04.014.002 Metodologie integrate per la conoscenza di processi e materiali geologici e del loro impatto sull uomo e l ambiente |
