TY - JOUR
T1 - Fine-scale in situ measurement of riverbed nitrate production and consumption in an armored permeable riverbed
AU - Lansdown, Katrina
AU - Heppell, Catherine M.
AU - Dossena, Matteo
AU - Ullah, Sami
AU - Heathwaite, A. Louise
AU - Binley, Andrew
AU - Zhang, Hao
AU - Trimmer, Mark
PY - 2014/4/15
Y1 - 2014/4/15
N2 - Alteration of the global nitrogen cycle by man has increased nitrogen loading in waterways considerably, often with harmful consequences for aquatic ecosystems. Dynamic redox conditions within riverbeds support a variety of nitrogen transformations, some of which can attenuate this burden. In reality, however, assessing the importance of processes besides perhaps denitrification is difficult, due to a sparseness of data, especially in situ, where sediment structure and hydrologic pathways are intact. Here we show in situ within a permeable riverbed, through injections of 15N-labeled substrates, that nitrate can be either consumed through denitrification or produced through nitrification, at a previously unresolved fine (centimeter) scale. Nitrification and denitrification occupy different niches in the riverbed, with denitrification occurring across a broad chemical gradient while nitrification is restricted to more oxic sediments. The narrow niche width for nitrification is in effect a break point, with the switch from activity "on" to activity "off" regulated by interactions between subsurface chemistry and hydrology. Although maxima for denitrification and nitrification occur at opposing ends of a chemical gradient, high potentials for both nitrate production and consumption can overlap when groundwater upwelling is strong.
AB - Alteration of the global nitrogen cycle by man has increased nitrogen loading in waterways considerably, often with harmful consequences for aquatic ecosystems. Dynamic redox conditions within riverbeds support a variety of nitrogen transformations, some of which can attenuate this burden. In reality, however, assessing the importance of processes besides perhaps denitrification is difficult, due to a sparseness of data, especially in situ, where sediment structure and hydrologic pathways are intact. Here we show in situ within a permeable riverbed, through injections of 15N-labeled substrates, that nitrate can be either consumed through denitrification or produced through nitrification, at a previously unresolved fine (centimeter) scale. Nitrification and denitrification occupy different niches in the riverbed, with denitrification occurring across a broad chemical gradient while nitrification is restricted to more oxic sediments. The narrow niche width for nitrification is in effect a break point, with the switch from activity "on" to activity "off" regulated by interactions between subsurface chemistry and hydrology. Although maxima for denitrification and nitrification occur at opposing ends of a chemical gradient, high potentials for both nitrate production and consumption can overlap when groundwater upwelling is strong.
UR - http://www.scopus.com/inward/record.url?scp=84898905098&partnerID=8YFLogxK
U2 - 10.1021/es4056005
DO - 10.1021/es4056005
M3 - Article
C2 - 24628544
AN - SCOPUS:84898905098
SN - 0013-936X
VL - 48
SP - 4425
EP - 4434
JO - Environmental Science and Technology
JF - Environmental Science and Technology
IS - 8
ER -