Sedimentary Phosphorus

1
GLOWA
Dust fluxes (samples poisoned by Na-Azide) in
Lake Agmon during 2002 (gr m-2 month-1). The
extremely high flux monitored in October results
from works conducted in the Lake area (including
the digging of an additional canal). Phosphorus
fluxes (Kg/lake/month) were calculated by
assuming that P conc entration in dust is
2500ppm. Organic matter was obtained by weigh
loss due to ignition (520oC). It was found that
approximately 75 of the dust is organic matter.
 
Lake Agmon Hydrology and Geochemistry By A.
Nishri,and M. Gophen
General Conclusions There is a seepage in both
directions, from Lake Agmon to its surroundings
and vice versa. However, seepage from the lake to
the surroundings predominance ant accounts for
about 10 of the total water inflows. Lake Agmon
functions as a settling pond for Phosphorus
about 40 of the external P input is sedimented
in the lake. Lake Agmon is also removes Nitrogen
about 2/3 of N input is removed in the lak either
by denitrification or sedimentation or
both. Sulfate balance indicates similarities
between inputs and outputs therefore if Sulfate
is educed to Sulfide, the opposite flux (Sulfide
oxidation to Sulfate) is occurring at a similar
magnitude. Dust contribute about 10 of P
inputs. Pore Water P profiles indicates as
removal/uptake in the upper layer (probably) by
benthic algae and macrophytes).
Methods Water discharges were measured biweekly
by portable-handy-flow meter at 5 stations
including inflows and outflows of Lake Agmon.
Water level in Lake Agmon (biweekly) evaporation
(daily) and rainfall (daily) were measured as
well. Chemical parameters (among others N,and P
forms, sulfate,DO, Turbidity) and physical
parameters (pH, Temp., conductivity) in Lake
Agmon were measured monthly. Dust fluxes and P
content were measured (bimonthly). Seepage was
measured in the inshore zone of the lake. P
content of the sediments and in the pore water
was measured. The biomass (dry weight) and
content of N and P in the submerged vegetation
was measured every 4 months.
Sedimentary Phosphorus In the northern part
of Lake Agmon the upper ca. 4cm of the
sedimentary column has a higher porosity (less
lithified), contains more organic matter but has
relatively less phosphorus. The decrease in
sedimentary P in the surface sediments is
indicated for various phosphorus sedimentary
phases. In most cores the concentration of
soluble phosphorus in the pore water of surface
sediments is also relatively low. One
possible explanation for these patterns is that
surface sediments contain eroded debris of
allochthanous and/or autochthonous origin and
that their P content represents the original
material eroded and deposited over the lake
floor. Another possible explanation is that P
depletion in the surface sediments is due to
consumption (uptake) by benthic (macro
filamentous algae) and submerged (macrophytes)
flora. These two hypotheses are yet to be
investigated.
Winter runoff coefficient is inversely related to
consumption lower coefficient relates to
higher consumption.Water consumption was actually
decreased and therefore it is suggested that
water loss w as enhanced