I. Experimental conditions: 2-ha section of marsh. Earthen dike encloses 10,000 m 3 of water (depth of 50 cm; water surface area of approximately 20,000 m 2 ) . 10 Ci HTO added to marsh and the system followed for one year.

II. Plant species:

(a)    Smartweed ( Polygonum lapathifolium ). Bound and unbound HTO follow the declining pattern of HTO in the marsh water. Evapotranspiration accounts mostly for tritium loss. Activity ratios of tritium in the tissue of the plant and marsh water are typically 0.3 or less throughout the observed period reported.

(b)    Pickerelweed ( Pontederia cordata ). Follows the same pattern as smartweed, but activity ratios of bound HTO to marsh water tritium approach 1.0 at several times. Activity ratios for unbound HTO vary from 0.02 to 0.6.

(c)    Pondweed ( Potamogeton crispus ). Follows a similar pattern to smartweed. Activity ratios over a long period of observation for bound and unbound HTO both range from 0.6 to 1.0, but then bound HTO ratios decline to near zero near the end of the observation period while the unbound HTO activity ratios remain in a range of 0.3-0.6.

III. Animal species:

(a)    The crayfish ( Procambarus blandingi ) accumulates maximum activity in muscle and viscera within 2 and 3 days directly, then the both bound HTO and unbound HTO decline rapidly. Maximum activity ratios of Bound HTO/Unbound HTO: muscle, 0.34; viscera, 0.23. The unbound HTO follows the marsh water, with activity ratios of close to 1. The bound HTO never reaches an activity level relative to marsh water of greater than 0.2, declines to less than 0.1 within 2 months, and hovers near zero for the rest of the observation period.

(b)    Carp ( Cyprinus carpio ) accumulates maximum activity in muscle and viscera within 4 hours of exposure then declines. Maximum activity ratios Bound HTO/Unbound HTO: muscle, 0.25; viscera, 0.39. The unbound HTO follows the same pattern as crayfish, with activity ratios close to 1 during much of the observation period and through its end. The bound HTO activity ratio never exceeds 0.1, remains relatively constant through much of the observation period, then declines to zero near the end of that period.

(c)    Bluegill ( Lepomis macrochirus ) accumulates maximum activity in muscle and viscera within 1 day. Maximum activity ratios Bound HTO/Unbound HTO: muscle, 0.35; viscera, 0.38. The unbound HTO tracks the marsh water activity decline for the rest of the period (activity ratios of about 0.8), while the bound HTO declines rapidly to near zero within 70 days for both muscle and viscera.

IV. To track the tritium in the marsh water, the following data are extracted from the paper by Adams et al:

Days Post-        Tritium concentration in          Days Post-        Tritium concentration in
Treatment        marsh water (dpm/L) bsp;Treatment          marsh water (dpm/L)

                                          p;    13,000        

                            bsp;            70                          11,000

                            sp;            100                         8000

                            sp;            170                         5000

                            sp;            220                         >2000

Notes:     (1) Reference: adapted from Adams et al. (1979), especially Figures 1-4 and text.
    (2) Tritium count data are rounded out to the nearest thousand.
    (3) No estimate of biomagnification factors from the species studied because of a lack of an established food-chain relationship.
    (4) dpm, disintegrations per minute.