| OCR Text |
Show Silver iodide concentrations do occur at generator sites. A site in use from 196k through 19& 9 " was sampled in 1971. Immediately at the site, a concentration of 16 ppm was detected in the first 10 centimeters of soil. Below 30 centimeters, the concentration was below the limit of detection ( 0.008 ppm). About ^ 00 feet from the site the concentration dropped to 0.05 ppm. No silver could be detected below 10 centimeters elsewhere. Soil microbial populations and respiration rates from the site and its immediate vicinity were compared with those from a number of sites in the San Juan Mountains. No correlation with silver content of the soil and either variable was observed. Other tests using sublethal levels of silver in various forms show no effect on normal development. Silver iodide dispensed during seeding can be deposited on forage and subsequently ingested by grazing animals. To determine if this could affect the digestion, a Bureau- sponsored research program has been started. Goats ( ruminants) were dosed with 1 ppm of silver iodide generator product three times a day for Ik days. Based on food intake and feces production, digestion was no different from that of control goats. Rabbits ( monogastric) were fed 5 ppm of generator produce for 11 days, with no change in folic- acid production from that of control rabbits. Six rabbits were force- fed 1 microcurie of radioactive silver. Some silver was retained for 5 to 7 days. Analyses indicated no absorption of silver by the digestive tract and complete excretion of the silver. It has been suggested that aquatic organisms may be very sensitive to silver iodide. A program to investigate this possibility is presently underway. Rainbow trout were exposed to running water containing 1 ppm of silver iodide for 2 weeks with no adverse effects noted. Silver iodide dissolved in sodium iodide was used next. Again, no effects were observed after a 2- week exposure to a concentration of 100 parts per billion. Silver iodide added to fish food at 1 ppm did not affect the trout over a 2- week period. In further tests a variety of chemicals are being added to the silver iodide in an effort to increase the solubility of the silver. The tests will be extended to include studies on a number of other aquatic organisms. 511 |
