Insect blood meal studies using radiosodium 24Na and 22Na.

Rabbits were infused with 3.7 GBq (100 mCi) of [24Na]Na ion in a 100-ml sodium carbonate solution. Beta particles were detected using a Tennelec Counting System; background counts were 1.6 +/- 1 counts per minute (cpm). Counts for one nanoliter of blood ranged from 22 to 30 cpm. Blood volumes on the mouthparts of tabanids following a 15-sec interrupted feeding were estimated to be 12.5 nl for Tabanus fuscicostatus, 10.8 nl for T. nigrovittatus and 6.12 nl for Chrysops fuliginosus. Estimates of the quantity of blood adhering to 22-gauge needles and insect pins (size 2) following a percutaneous intramuscular needle-stick were 8.8 +/- 1.0 nl and 5.7 +/- 1.8 nl, respectively. Mosquitoes, Aedes aegypti females, were fed to repletion with a 22Na-artificial diet, and radioactivity was measured using a Packard Autogamma 5650. The estimated average blood meal size was 2.80 +/- 0.94 microliters.

Radiocesium-137 movement in a southern coastal plain ecosystem.

The movement of radiocesium (137Cs) in an open ecosystem under natural conditions was investigated at the Louisiana State University Radioecology Field Laboratory. Approximately 80 mCi of 137Cs were transferred to an experimental plot in September 1979. Observations over a six-month period beginning February 1981 indicated that the 137Cs content of plants growing naturally in the plot was low (0.98 Bq/g of plant tissue, dry wt). The vertical mobility of 137Cs to more than 10 cm was also found to be low (up to 1.32 Bq/g of soil, dry wt). The horizontal migration of 137Cs along water drainage directions from the plot was limited to the area of a small ditch that surrounds the experimental plot. No 137Cs above background was found in the fields beyond the 10 m X 10 m plot boundary. The overall results demonstrated that greater than 99.9% of the 137Cs remained within the top 10 cm of the soil profile of the experimental plot under natural field conditions.