es7b03121_si_001.pdf (356.56 kB)
High-Resolution in Situ Measurement of Nitrate in Runoff from the Greenland Ice Sheet
journal contribution
posted on 2017-09-27, 00:00 authored by Alexander D. Beaton, Jemma L. Wadham, Jon Hawkings, Elizabeth A. Bagshaw, Guillaume Lamarche-Gagnon, Matthew C. Mowlem, Martyn TranterWe
report the first in situ high-resolution nitrate time series
from two proglacial meltwater rivers draining the Greenland Ice Sheet,
using a recently developed submersible analyzer based on lab-on-chip
(LOC) technology. The low sample volume (320 μL) required by
the LOC analyzer meant that low concentration (few micromolar to submicromolar),
highly turbid subglacial meltwater could be filtered and colorimetrically
analyzed in situ. Nitrate concentrations in rivers draining Leverett
Glacier in southwest Greenland and Kiattuut Sermiat in southern Greenland
exhibited a clear diurnal signal and a gradual decline at the commencement
of the melt season, displaying trends that would not be discernible
using traditional daily manual sampling. Nitrate concentrations varied
by 4.4 μM (±0.2 μM) over a 10 day period at Kiattuut
Sermiat and 3.0 μM (±0.2 μM) over a 14 day period
at Leverett Glacier. Marked changes in nitrate concentrations were
observed when discharge began to increase. High-resolution in situ
measurements such as these have the potential to significantly advance
the understanding of nutrient cycling in remote systems, where the
dynamics of nutrient release are complex but are important for downstream
biogeochemical cycles.