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Closed Access item Point-source effects on N and P uptake in a forested and an agricultural Mediterranean streams
|Authors:||Merseburger, G. C.|
Ortiz, J. D.
|Keywords:||Point-source, Stream, Nitrogen, Phosphorus, Nutrient uptake|
|Citation:||Science of the Total Environment 409(5) : 957-967 (2011)|
|Abstract:||We examined the effect of point-source inputs from wastewater treatment plants (WWTP) on in-stream
uptake of ammonium, nitrate and phosphate and compared it between two streams draining catchments with
contrasting land use. The selected streams were La Tordera and Gurri (NE Spain), draining a forest- and an
agriculture-dominated catchment, respectively. In each stream, we compared nutrient uptake metrics,
estimated from nutrient additions, between two reaches located upstream and downstream of a WWTP input.
Measurements were done on 8–9 dates during 2002–2003.
In La Tordera, the point-source increased concentrations of all studied nutrients; whereas in Gurri, this effect
was less evident. Point-source effects on nutrient uptake differed between the two streams, and among
solutes. In La Tordera, uptake lengths (Sw) of ammonium and phosphate averaged hundreds of meters above
the point-source, and increased (i.e., decreased uptake efficiency) 4 and 5 times, respectively, below the
point-source. Sw of nitrate was ≥2 km regardless of reach location. In Gurri, Sw of all studied nutrients was
within the km range in the two reaches. In this stream, diffuse nutrient inputs from adjacent fields may
overwhelm the local effect of the point-source input.
Uptake velocities (vf) of the studied nutrients ranged between 10EXP−6 and 10EXP−4 m/s in the two streams,
and were similar between the two reaches in each stream. However, phosphate vf decreased under increasing
concentrations following a power function. This trend remained significant when combining our results with
those compiled from literature, suggesting the efficiency loss response may be a general trend for phosphate
The relative increases in uptake rates (U) below the point-source were proportional to the relative point-source
contribution to downstream nutrient loads, especially for ammonium and nitrate. However, the increases in U
were not enough to compensate for the increases in nutrient loads downstream of theWWTP input.|
|Description:||11 Páginas ; 4 Figuras ; 4 Tablas|
|Publisher version (URL):||http://dx.doi.org/10.1016/j.scitotenv.2010.11.014|
|Appears in Collections:||(CEAB) Artículos|
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