Geochemistry of Major Elements in a Pristine Boreal River System; Hydrological Compartments and Flow Paths |
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| Authors: | Email author" target="_blank">J?IngriEmail author A?Widerlund M?Land |
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| Institution: | 1.Division of Applied Geology, Lule?,University of Technology,Sweden;2.Department of Geology and Geochemistry,Stockholm University,Stockholm,Sweden |
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| Abstract: | Once or twice weekly, water sampling was undertaken for a two and a half year period in the Kalix River, northern Sweden.
Soil water, groundwater, water in tributaries and mire water were also sampled at several occasions. Samples were filtered
and analysed for major dissolved elements and TOC. Although only 5 of the bedrock in the Kalix River drainage basin is situated
in the Caledonian mountains (mostly schist, with some outcrops of dolomite and limestone), the chemical composition of the
river, at the river mouth, is clearly influenced by water from the mountain areas. High dissolved Ca/Mg ratios in June and
July indicate a large influence of water from the mountain areas during summer. The dissolved Si/Mg ratio increases when water
from the woodland (bedrock consisting of Precambrian granitoids) predominates during snowmelt in May, but the ratio is low
during summer when water from the mountains is increased. However, the low Si concentrations in the mountain areas are probably
not primarily the result of the different rocks but more a reflection of the less intense weathering of silicate minerals
in the mountains. High Si/Mg ratios are closely related to high TOC. All the major dissolved elements, except TOC, are diluted
by snowmelt in May. However, the dilution varies for different elements. Based on the interpretations of major element ratios
the melt water discharge in May reflects two major compartments in the woodland; peatland areas and the upper section of the
soil. During summer and autumn storm events in the woodland most of the storm water originated from peatland. High K/Mg ratios
in the river in May are related to water discharge from the upper section of the till. Low S/Mg ratios in the river indicate
an influence of mire water from the woodland both during melt water discharge in May and during increased water discharge
in autumn. The Ca/Mg ratios in tributaries in the woodland are consistently lower during melt water discharge compared with
values in August. The lower Ca/Mg ratio in May probably reflects water that has been in contact with the B-horizon in the
till during spring flood. Data show that the TOC discharged during spring flood originates from two major compartments in
the landscape, the upper soil profile and peatland. Storm discharge of TOC during the rest of the year originates mostly from
peatland. |
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| Keywords: | major elements Kalix River Northern Sweden normalisation hydrogeochemistry flow paths |
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