River flow, tritium

Another pathway whereby tritium enters the ocean is through continental runoff and river flow. Tritium deposited to the continents ultimately flows to the oceans via lakes, rivers and groundwater flow, but is retained within the continental hydrosphere for time-scales of many years, thereby introducing a delayed input to the oceans. Further, when computing the time-evolving tritium inventory within an ocean basin, it is necessary to consider inflow and outflow across the basin s boundaries. 

A widely used instmment for air monitoring is a type of ionization chamber called a Kaimn chamber. Surface contamination is normally detected by means of smears, which are simply disks of filter paper wiped over the suspected surface and counted in a windowless proportional-flow counter. Uptake of tritium by personnel is most effectively monitored by urinalyses normally made by Hquid scintillation counting on a routine or special basis. Environmental monitoring includes surveillance for tritium content of samples of air, rainwater, river water, and milk. 

Figure 10.10 provides data on repeated tritium measurements in a well and in the adjacent Mohawk River. What hydrological conclusions can be drawn The variations in tritium concentrations in the well followed variations in the river, as shown in Fig. 10.10. Hence, the river is recharging the well. The time lag in the well s response can be used to calculate recharge velocities. The data reveal piston flow of the recharge water, with little smoothing by dispersion (Fig. 10.10).

Recent tritium data from Wells 199-N-67 and 199-N-69 (Color Illustration 2-2), however, show a different pattern. These data indicate significant contamination at depth, and in both Wells 199-N-67 and 199-N-69 higher levels of contamination at depth than at water table. For example, tritium activity observed in Wells 199-N-67 and 199-N-69 in November/December 1989 was 42,600 pCi/L and 78,400 pCi/L, respectively. The higher tritium levels at depth in the vicinity of 116-N-l may indicate a deeper, preferential flow path for discharge from 116-N-3, particularly in the most direct pathway towards the river. The Sr activity associated with discharges to 116-N-3 is presumably not observed at this point in the migration pathway because it was previously removed through adsorption in the immediate vicinity of the crib. 

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