Cesium Kinetics in a Montane Lake Ecosystem

Abstract

This study was initiated to determine the kinetics of cesium transport in East Twin Lake, a 5-ha, natural semi-drainage lake which lies at an elevation of 2880 m in the north-central Colorado Rockies. One kilogram of 133Cs (as 133CsC1) was introduced into the water of East Twin Lake on 15 September 1970. Samples of water, seston, sediment, amphipods, zooplankton, trout and two species of vegetation were obtained over a 393-day period following the dosing event. Stable cesium was measured by neutron activation analysis.The loss of 1%k from water occurred in two phases. The rapid phase accounted for the loss of 60% of the cesium from water and had a loss half-time of 0.5 days while the slow phase had a loss half-time of 130 days. The seston fraction of each water sample contained from 25 to 80% of the 133Cs present in each liter of unfiltered water. Bottom sediments were identified as the major site of deposition of the '=Cs dose. The sediment, at 393 days post-dosing, accounted for 82% of the l%Cs inventory in the lake whereas water and seston accounted for only 3 and 14%, respectively. Amphipods and zooplankton reached equilibrium with the water within about 3 weeks after the lSCs administration and achieved concentration factors (wet weight) of about 700 and 150, respectively. During mid-winter, however, these organisms showed increased concentrations of lSCs with concentration factors ranging up to 3700 and 350 for amphipods and zooplankton, respectively. Trout accumulated the 1BCs more slowly than the invertebrates and reached a maximum concentration factor of about 5600 some 260 days following the dosing event.Absolute quantities as small as 10-8 g of lSCs were detectable. Concentrations of133Cs and fallout lS7Cs in trout muscle were significantly correlated which indicated that the kinetic behavior of the isotopes in this component of the lake was similar. Furthermore, the stable tracer obviates the radiation protection problems that would arise from contaminating a public water with a radiosotope of cesium.

Foliar uptake of cesium from the water column by aquatic macrophytes

“…Two studies that do provide sufficient data are the Kolehmainen et al (1967) study of 137 Cs addition to 2 small (!1 ha) Finnish lakes, Lakes Porholanlampi and Valkealampi, and Hakonson and Whicker's (1975) introduction of 133 Cs into East Twin Lake, a 5-ha Montane lake in Colorado, USA. At least some of the plant species in these lakes demonstrated patterns of Cs accumulation that suggest foliar uptake.…”

“…A separate model for Lake Valkealampi did not consider the macrophytes (Vanderploeg et al, 1975b). Hakonson (1972) considered at least part of the 133 Cs accumulation by N. polysepalum to be due to foliar uptake and surface contamination and modeled the results for both species by assuming direct uptake from the water.…”

“…(2) and (3). Concentrations of 133 Cs in East Twin Lake waters and plants are listed in Hakonson (1972). The concentrations for the Finnish lakes were extrapolated from figures in Kolehmainen et al (1967) and Vanderploeg et al (1975aVanderploeg et al ( , 1975b, and thus the estimated u and k values and their standard errors should be considered approximate.…”

Distribution of gamma-ray emitting radionuclides in the marine environment of the Burullus Lake: II. Bottom sediments

“…Most radionuclides are sorbed directly to sediments or to sinking particles within 1-2 years (e.g., Hakonson and Whicker 1975). However, small fractions of the radionuclides may later be remobilized from the sediments to the water column and subsequently be taken up by biota or exported hydrologically from the system (Alberts et al 1979;Bird et al 1998).…”

Sorption kinetics of Cs and Sr in sediments of a Savannah River Site reservoir

“…A couple of models formulated first order rate equations, describing a kinetics layered approximation and employing the sorption rates or the Kd in conjunction with processes of diffusion, settling, and resuspension to predict the tracer removal from the water column (Nyfeller et al 1986;Adler 1982). Some models were simplifications of the contributing processes and compartments, yet maintained a good prediction for their experiments (Monte et al 1991;Monte 1993;Monte 1995;Hesslein 1980;Hakonson 1972). Overall, some models have the advantage of formulation, others simplification.…”