RESUMO

Concentrations of 127I and 129I in rainwater samples from several stations across Argentina (latitudes between 25° S and 55° S) were measured and analyzed for the assessment of distribution patterns and potential sources of 129I in the Southern Hemisphere. Measured 129I levels, clearly above those explainable by natural background and atmospheric nuclear weapons tests, can be understood by the injection into the Southern Hemisphere of 129I that had been discharged from nuclear fuel reprocessing plants in the Northern Hemisphere.

Assuntos

Poluentes Radioativos do Ar , Monitoramento de Radiação , Poluentes Radioativos do Ar/análise , Argentina , Radioisótopos do Iodo/análise

RESUMO

Trophallaxis between individual worker ants and the toxicant load in dead and live Argentine ants (Linepithema humile) in colonies exposed to fipronil and hydramethylnon experimental baits were examined using accelerator mass spectrometry (AMS). About 50% of the content of the crop containing trace levels of 14C-sucrose, 14C-hydramethylnon, and 14C-fipronil was shared between single donor and recipient ants. Dead workers and queens contained significantly more hydramethylnon (122.7 and 22.4 amol/µg ant, respectively) than did live workers and queens (96.3 and 10.4 amol/µg ant, respectively). Dead workers had significantly more fipronil (420.3 amol/µg ant) than did live workers (208.5 amol/µg ant), but dead and live queens had equal fipronil levels (59.5 and 54.3 amol/µg ant, respectively). The distribution of fipronil differed within the bodies of dead and live queens; the highest amounts of fipronil were recovered in the thorax of dead queens whereas live queens had the highest levels in the head. Resurgence of polygynous ant colonies treated with hydramethylnon baits may be explained by queen survival resulting from sublethal doses due to a slowing of trophallaxis throughout the colony. Bait strategies and dose levels for controlling insect pests need to be based on the specific toxicant properties and trophic strategies for targeting the entire colony.