03621nas a2200133 4500008004100000245010500041210006900146260002700215490001000242520306700252100002503319700002403344856011903368 2001 eng d00aModeling hyporheic exchange influences on biogeochemical processes in dry valley streams, Antarctica0 aModeling hyporheic exchange influences on biogeochemical process bUniversity of Colorado0 vPh.D.3 a

The ephemeral streams of the Dry Valleys of Antarctica provide habitat to benthic algal mats, and greatly control the quantity and quality of glacial melt water that enters closed basin Dry Valley lakes. Dry Valley watersheds are composed of streambeds and adjacent hyporheic zones. Hydrologic exchange of water and solutes between the stream and the hyporheic zone has the overall effect of increasing residence time in the stream/hyporheic system. Biogeochemical reactions (e.g. chemical weathering, nutrient assimilation) occur both in the water column and in the hyporheic zone. Field experiments and solute transport modeling were employed to elucidate the effects of rapid hyporheic exchange on biogeochemical cycling in Antarctic streams. The results presented here show that (1) large portions of the wetted zone that surrounds each stream is a hyporheic zone, and that stream water exchanges into and out of extended portions of this zone on the order of weeks, (2) the rapid exchange of stream water between the water column and the hyporheic zone controls the rate of weathering in streambed sediments, and (3) denitrification in streams is limited by the conversion of NO2 to N2O, while the conversion of NO3 to NO2 occurs very quickly.

1 aGooseff, Michael, N.1 aMcKnight, Diane, M. uhttps://mcm.lternet.edu/content/modeling-hyporheic-exchange-influences-biogeochemical-processes-dry-valley-streams