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