Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Influence of emergent vegetation on nitrate cycling in sediments of a groundwater-fed river
AU - Ullah, Sami
AU - Zhang, Hao
AU - Heathwaite, A. Louise
AU - Heppell, Catherine
AU - Lansdown, Katrina
AU - Binley, Andrew
AU - Trimmer, Mark
PY - 2014/4
Y1 - 2014/4
N2 - Emergent vegetation in river beds can play a significant role in nutrient cycling in riverine sediments. We analysed and compared pore water NO3 (-) concentration gradients in the sediments of the River Leith, Cumbria, UK, in the presence and absence of emergent vegetation (dominated by Sparganium spp.). High resolution (1 cm interval), in situ, vertical profiles of NO3 (-) to 30 cm depth were measured using deployment of diffusive equilibrium in thin films probes on four occasions from July to September 2010. We found significantly (p <0.05) lower NO3 (-) concentration under vegetated sediments (VS) compared to those under adjacent un-vegetated sediments (UVS). Concentrations of dissolved oxygen, measured in pore water collected from multi-level piezometers at 10, 20, 25, 30 and 35 cm depths at the VS and UVS sties, were generally lower under VS (median concentration = 28 mu M) than under UVS (median = 132 mu M) and correlated significantly with NO3 (-) concentration (Spearman's r = 0.74, p <0.05). Similarly, pore water dissolved organic carbon (DOC) concentration was 2.8 times higher under VS compared to UVS, and correlated negatively with NO3 (-) concentration (Spearman's r = -0.39, p <0.05). Specific ultra-violet absorption at 254 nm (SUVA) and per cent aromaticity values of DOC were significantly higher under VS (p <0.05), suggesting that the DOC contained more complex (aromatic) compounds than DOC recorded under UVS. We suggest that, the higher quantity of DOC and its distinct SUVA and percentage aromaticity under VS may have supported faster dissolved oxygen consumption, with the creation of anoxic zones conducive for NO3 (-) reduction mainly through denitrification. Metabolic uptake and immobilization of NO3 (-) by plants and microbes may have further contributed to lower NO3 (-) concentrations under VS. As Sparganium spp. is a common plant growing in river beds in the UK, its role in NO3 (-) cycling should be considered in attempts to accurately budget N cycling in river beds.
AB - Emergent vegetation in river beds can play a significant role in nutrient cycling in riverine sediments. We analysed and compared pore water NO3 (-) concentration gradients in the sediments of the River Leith, Cumbria, UK, in the presence and absence of emergent vegetation (dominated by Sparganium spp.). High resolution (1 cm interval), in situ, vertical profiles of NO3 (-) to 30 cm depth were measured using deployment of diffusive equilibrium in thin films probes on four occasions from July to September 2010. We found significantly (p <0.05) lower NO3 (-) concentration under vegetated sediments (VS) compared to those under adjacent un-vegetated sediments (UVS). Concentrations of dissolved oxygen, measured in pore water collected from multi-level piezometers at 10, 20, 25, 30 and 35 cm depths at the VS and UVS sties, were generally lower under VS (median concentration = 28 mu M) than under UVS (median = 132 mu M) and correlated significantly with NO3 (-) concentration (Spearman's r = 0.74, p <0.05). Similarly, pore water dissolved organic carbon (DOC) concentration was 2.8 times higher under VS compared to UVS, and correlated negatively with NO3 (-) concentration (Spearman's r = -0.39, p <0.05). Specific ultra-violet absorption at 254 nm (SUVA) and per cent aromaticity values of DOC were significantly higher under VS (p <0.05), suggesting that the DOC contained more complex (aromatic) compounds than DOC recorded under UVS. We suggest that, the higher quantity of DOC and its distinct SUVA and percentage aromaticity under VS may have supported faster dissolved oxygen consumption, with the creation of anoxic zones conducive for NO3 (-) reduction mainly through denitrification. Metabolic uptake and immobilization of NO3 (-) by plants and microbes may have further contributed to lower NO3 (-) concentrations under VS. As Sparganium spp. is a common plant growing in river beds in the UK, its role in NO3 (-) cycling should be considered in attempts to accurately budget N cycling in river beds.
KW - Nitrate cycling
KW - Riverbed sediments
KW - Water quality
KW - Emergent vegetation
KW - Groundwater-fed rivers
KW - DISSOLVED ORGANIC-CARBON
KW - SURFACE-WATER
KW - NUTRIENT CHARACTERISTICS
KW - SUBMERGED MACROPHYTES
KW - AQUATIC MACROPHYTES
KW - STREAM SEDIMENTS
KW - PORE WATERS
KW - GEL PROBES
KW - NITROGEN
KW - RESOLUTION
U2 - 10.1007/s10533-013-9909-2
DO - 10.1007/s10533-013-9909-2
M3 - Journal article
VL - 118
SP - 121
EP - 134
JO - Biogeochemistry
JF - Biogeochemistry
SN - 0168-2563
IS - 1-3
ER -