Contaminación por nitrógeno en el sistema "río-acuífero aluvial" de la cuenca del Jarama (Comunidad de Madrid, España) ¿Origen agrícola o urbano?
A hydrochemical characterization of the "river-alluvial aquifer" system in the Quaternary deposits of the Jarama catchment has been performed, including the rivers Jarama, Henares, Manzanares, Tajuña and a part of Tajo, as well as the alluvial aquifer associated to the said fluvial net. Th...
| Autores: | , , |
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| Tipo de recurso: | artículo |
| Fecha de publicación: | 2008 |
| País: | España |
| Institución: | Universitat Autònoma de Barcelona |
| Repositorio: | Dipòsit Digital de Documents de la UAB |
| Idioma: | español |
| OAI Identifier: | oai:ddd.uab.cat:32774 |
| Acceso en línea: | https://ddd.uab.cat/record/32774 |
| Access Level: | acceso abierto |
| Palabra clave: | "Riu-aqüífer luvial" Conca del Jarama Nitrogen Nitrat Amoni Agricultura de regadiu Efluents urbans Zones Vulnerables a la contaminació per nitrats "River-alluvial aquifer" Jarama catchment Nitrate Ammonia Irrigated agriculture Urban effluents Vulnerable Zones to nitrate pollution "Río-acuífero aluvial" Cuenca del Jarama Nitrógeno Nitrato Amonio Agricultura de regadío Efluentes urbanos Zonas Vulnerables a la contaminación por nitratos |
| Sumario: | A hydrochemical characterization of the "river-alluvial aquifer" system in the Quaternary deposits of the Jarama catchment has been performed, including the rivers Jarama, Henares, Manzanares, Tajuña and a part of Tajo, as well as the alluvial aquifer associated to the said fluvial net. The roles of agriculture and urban uses have been explored as possible sources of nitrogen pollution in surface and underground water resources. Two sampling campaigns were performed, in March (at the end of the winter) and in August of 2005 (when irrigation water demand was at its highest), with water samples collected at 35 sampling stations (16 wells on the alluvial aquifer and 19 fluvial stations). The medium and low areas of the Manzanares, Jarama, Tajuña, and Tajo rivers did not meet the standards of quality established by the Tajo Catchment Hydrologic, due to high levels of ammonia, QOD and. electric conductivity, attributable to the incorporation of water treatment effluents originating from urban areas, (in some areas, conductivity levels could be explained by the geological context). The medium and low areas of the alluvial aquifer (in each subcatchment) showed very high values of nitrate concentration and conductivity, making its use unsuitable for drinking and restricting it for agricultural irrigation. A clear concordance was found between the spatial distribution of nitrate pollution in the alluvial aquifer and the agricultural irrigated areas. Using the N/P ratio as an indicator of the agricultural or urban origin it is interpreted that nitrogen pollution is mainly of urban origin in the rivers and of agricultural precedence in the alluvial aquifer (attributable to the bad management of fertilization and irrigation). The problem is compounded when water from nitrogen polluted rivers is used for irrigation, transferring nitrogen of fluvial origin into the alluvial aquifer with the irrigation return flows (urban nitrogen + fertilizers nitrogen). On the other hand, it has been observed that the excess of irrigation reverts the natural dynamic of the aquifer, producing rises of the phreatic level in extensive areas during the summer. These results provide a scientific basis to consider the declaration of the Quaternary alluvial deposits of the Jarama catchment as a Vulnerable Zone to nitrate contamination of agricultural origin, as established in the Directive 91/676/EEC. |
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