Net dissolved inorganic nitrogen production in hyporheic mesocosms with contrasting sediment size distributions |
| |
Authors: | Brett N Harvey Michael L Johnson Joseph D Kiernan and Peter G Green |
| |
Institution: | (1) Center for Watershed Sciences, University of California, One Shields Avenue, Davis, CA 95616, USA;(2) Department of Civil and Environmental Engineering, University of California, Davis, CA 95616, USA |
| |
Abstract: | The interstitial spaces within streambeds are recognized as an important location of dissolved inorganic nitrogen (DIN) transformations
in streams. However, it remains uncertain how physical characteristics of streambeds affect the magnitude and net outcome
of subsurface nitrogen transformations. We tested whether the size distribution of streambed sediments, in isolation from
the influence of streambed topography and groundwater upwelling, could affect net DIN uptake or production along interstitial
flow paths. Mesocosms constructed from PVC pipe (15 cm diameter × 1 m long) were filled with either coarse gravel/cobble or
gravel/cobble mixed with finer sediments (5 mesocosms per sediment treatment). Mesocosms were submerged in a stream and oriented,
so that surface water flowed through the sediments. After 2 months incubation, we measured DIN in interstitial water at 20 cm
intervals and dissolved oxygen at 10 cm intervals along mesocosm flow paths. In both sediment types, DIN concentrations increased
longitudinally along mesocosm flow paths in the direction of interstitial flow, indicating net DIN production. Although DIN
increased to higher concentrations in mesocosms with fine sediments, greater exchange flow through coarse sediments resulted
in similar rates of net DIN production and delivery to surface water. Production of DIN in both sediment types was concentrated
within the first 10 cm of interstitial flow paths, with no significant production further along the flow paths. Coarse sediments
had higher rates of oxygen consumption per unit sediment volume than the coarse–fine sediment mix, suggesting interstitial
water velocity may be an important factor affecting hyporheic microbial metabolism. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|