INVESTIGADORES
JOBBAGY GAMPEL Esteban Gabriel
artículos
Título:
Nitrate dynamics in the soil and unconfined aquifer in arid groundwater coupled ecosystems of the Monte desert, Argentina
Autor/es:
ARANIBAR JN; VILLAGRA P; GOMEZ ML; JOBBAGY EG; QUIORGA M; WUILLOUD RG; MONASTERIO RP; GUEVARA A
Revista:
JOURNAL OF GEOPHYSICAL RESEARCH
Editorial:
AMER GEOPHYSICAL UNION
Referencias:
Lugar: Washington DC; Año: 2011 vol. 116 p. 1 - 14
ISSN:
0148-0227
Resumen:
In arid ecosystems, vegetation controls water and nitrate movement in the soil, 7 reducing solute transport to aquifers. Here we analyzed nitrate distribution and transport 8 throughout the soil profile and to the groundwater under different ecologic (vegetation 9 type) and topographic (upland/lowland) situations across sand dune ecosystems with 10 shallow water tables, subject to domestic grazing in the Monte desert. Based on vertical 11 nitrate distributions in deep soil profiles we found that dune uplands (deep groundwater, 12 low productivity) lost relatively more nitrogen than lowlands (shallow groundwater, 13 high productivity), likely reinforcing productivity contrasts along these topographic 14 positions. The traditional practice of nighttime animal concentration in corrals may affect 15 nitrogen transport, with poorly vegetated interdunes at livestock posts showing higher 16 subsoil nitrate concentrations than a well‐vegetated nonsettled interdune. Vegetation left 17 its imprint on the vertical distribution of nitrate, as suggested by the presence of a depletion 18 zone that matched the depth of maximum root densities, followed by an underlying zone 19 of accumulation. To explore how nitrogen exports to groundwater could affect water 20 quality and nutrient supply to phreatophyte plants, we characterized groundwater flow 21 patterns based on a potentiometric map and sediment characteristics, and measured 22 groundwater electric conductivity, nitrate and arsenic concentration, and stable isotopes 23 across 29 wells (5.8–12 m deep). Under the present land use and climate conditions, nitrate 24 leaching does not seem to have an important and widespread effect on water quality. Nitrate 25 concentration exceeded established limits for human consumption (45 mg L−1) in only one 26 well, while arsenic concentration exceeded the established limits (10 mg L−1) in all but 27 one well, reaching extreme values of 629 mg L−1. Yet, our analysis suggests that nitrate 28 exports from corrals can reach the aquifer in localized areas and be transported to the 29 surrounding vegetation in a relatively short time. Vegetation access to groundwater could 30 allow ecosystems to recover part of this nutrient loss, buffering the effects of land use