TY - JOUR
T1 - Colloid dynamics and transport of major elements through a boreal river - brackish bay mixing zone
AU - Gustafsson, Ö.
AU - Widerlund, A.
AU - Andersson, P.
AU - Ingri, J.
AU - Roos, P.
AU - Ledin, Anna
PY - 2000
Y1 - 2000
N2 - A range of biogeochemical methodologies were applied to investigate how aggregation processes affected the phase
distribution and mixing of Fe, Si, and organic carbon between the Kalix River and the Bothnic Bay, northernmost Baltic Sea
salinityF3; the low-salinity zone LSZ. was stretching over 60 km in the spring.. During the dynamic springflood
conditions studied, small 238U–234Th disequilibria, low sediment trap fluxes, laboratory mixing experiments, as well as
results from an independent two-box, two-dimensional mixing model combine to suggest that no significant removal of Fe,
Si, or organic C was occurring in the highly-resolved LSZ. While no conclusions may be drawn based solely on
property–salinity plots over narrow salinity ranges, apparently linear graphs for Fe and Si over 3 separate years also suggest
minimal removal in this regime. At the same time, size distributions both of elements —from cross-flow ultrafiltration —
and of bulk suspended solids — from light scattering photon correlation spectroscopy wPCSx. — indicated that significant
aggregation was taking place.
The aggregation-without-significant-settling scenario in this low-salinity mixing regime, with a geochemistry similar to
that of neighboring Russian Arctic rivers, is hypothesized to result from a comparatively high organic-to-detrital matter
characteristic of the aggregates. While first principles would indeed suggest that decreasing electrostatic repulsion during
mixing lead to aggregation, a low specific density of mineral-poor amorphous organic aggregates may lead to transport of
these authigenic particles further away from the river mouth. The role of detrital ‘‘sinkers’’ on vertical removal of suspended
organic matter is discussed in the wider context of scavenging mechanisms in the ocean. q2000 Elsevier Science B.V. All
rights reserved.
AB - A range of biogeochemical methodologies were applied to investigate how aggregation processes affected the phase
distribution and mixing of Fe, Si, and organic carbon between the Kalix River and the Bothnic Bay, northernmost Baltic Sea
salinityF3; the low-salinity zone LSZ. was stretching over 60 km in the spring.. During the dynamic springflood
conditions studied, small 238U–234Th disequilibria, low sediment trap fluxes, laboratory mixing experiments, as well as
results from an independent two-box, two-dimensional mixing model combine to suggest that no significant removal of Fe,
Si, or organic C was occurring in the highly-resolved LSZ. While no conclusions may be drawn based solely on
property–salinity plots over narrow salinity ranges, apparently linear graphs for Fe and Si over 3 separate years also suggest
minimal removal in this regime. At the same time, size distributions both of elements —from cross-flow ultrafiltration —
and of bulk suspended solids — from light scattering photon correlation spectroscopy wPCSx. — indicated that significant
aggregation was taking place.
The aggregation-without-significant-settling scenario in this low-salinity mixing regime, with a geochemistry similar to
that of neighboring Russian Arctic rivers, is hypothesized to result from a comparatively high organic-to-detrital matter
characteristic of the aggregates. While first principles would indeed suggest that decreasing electrostatic repulsion during
mixing lead to aggregation, a low specific density of mineral-poor amorphous organic aggregates may lead to transport of
these authigenic particles further away from the river mouth. The role of detrital ‘‘sinkers’’ on vertical removal of suspended
organic matter is discussed in the wider context of scavenging mechanisms in the ocean. q2000 Elsevier Science B.V. All
rights reserved.
KW - Bothnic Bay
KW - Colloids
KW - Low-salinity zone
KW - Kalix River
KW - Aggregation
U2 - 10.1016/S0304-4203(00)00035-9
DO - 10.1016/S0304-4203(00)00035-9
M3 - Journal article
SN - 0304-4203
VL - 71
SP - 1
EP - 21
JO - Marine Chemistry
JF - Marine Chemistry
IS - 1-2
ER -