As at Eneu, HFH 1, the chemical quality of the the radionuclide con- centrations in Bikini surface ground- water also changed slowly over the water samples are variable. Both 90 239,240 the or Pu are in higher nd day. concentration in the groundwater any use, withdrawal rates should not from Locations north of exceed 8 litres/min. baseline in (HFH 3, the waters 137 The Cs south of to assure the best-quality water for the center HFH 4, HFH 5) this concentrations Therefore, we recommend that than The mean Cs concentration in the surface groundwaters at Bikini road. was 430 show no + 179 pCi/litre. An addi- apparent geographical correlation, tional 2.4% is associated with the and none of the radionuclide concen-— particulate phase. 137 trations appear related to water freshness. lowest Ose concentration in its water. The last two samples pumped from HFH 1] had the lowest water. In a shows ‘os and recent 90 report, Sr Conard concentrations in well water samples from several Bikini lecations for the years 19/1, Oc con- centrations and the highest on the aver- concentration guideline for drinking to have the Cs concentration and the highest Cs concentration is, total age, 2.5% of the recommended FRC Of the newly established wells, we found HFH 4 The present 1972, and 1973. "os Since no locations concentrations among the newly estab- or identifications were given with lished wells. Conard's data, we have averaged gest 1s that These data might sug- ; the concentration of inversely related to 137 both the 13766 and 1S for each year and have plotted the the concen- ; 9 tration of Ose, values, trations increased over the day, both the time in Fig. "os groundwater concen- the Oo, a : é nd 239,240), | tofether with our 1975 mean concentrations, During the pumping experiment at HEH 1, Os, concentrations c 5. as a function of Although the stan- dard deviations during any single but year are large, concen- the data strongly trations were lower in the final sam- indicate that ples than in the first sample. water concentrations have declined These over the last four years, data demonstrate that a single radio- 90 nuclide should not be used as a universal indicator the mean while the os Sr concentrations appear to have increased over this same to describe the los ground- interval. temporal variations of other radio- These data demonstrate again the nuclides in the groundwater reser- great need for detailed assessment of voirs. the mechanisms controlling the Coincident with the radio- cycling of individual radionuclides nuclide changes during pumping at -16- JUPU2ZO4