Studies of methamidophos-C-14 in Costa Rican vegetables and soils

In order to see the effect of time lapse between the last application of methamidophos and harvesting insecticide was applied on lettuce plants (6,84 μCi in one experiment and 4,03 μCi in the other experiment). Analysis of the crops harvested 3 days after last application showed 9,7 ppm residues on leaves, while crops harvested 1 day after application showed residues of 12,7 ppm (25% more). Treatment of tomato plants (39,65 μCi, 1,01 kg/ha) gave residues in fruits 4,92 ppm after 8 days interval between last application and harvesting. 40 days gap between the last application and harvesting leaved residues of 0,7 ppm in fruits which is much less as recommended by FAO/WHO (1 – 2 ppm).Degradation of this insecticide is dependent on the matrix of the soil, this breakdown is observed in the first ten days and than after it remains constant. C-14 radioactivity extracted from soil and plant analysis was methamidophos (92%)     

Ein Beitrag zur Photostabilität organischer Umweltchemikalien in Gegenwart von Wasserstoffperoxid in aquatischen Systemen

It is well documented that the photolysis of H₂O₂ generates OH radicals which play an important role in explaining the degradation of environmental chemicals in aqueous medium. In the following work relative reaction rate constants of some representative substances were determined with wavelengths above 290 nm in the presence of H₂O₂. The results show, that the used system is suitable to check the OH radical reactivity of organic compounds under natural conditions.     

Fate of benzo(a)pyrene-C during brew process

Benzo(a)pyrene-¹⁴C (1 ppm) was applied to wort and boiled with hops in a brew process. The wort after filtration was subjected to fermentation. The hops and yeast were found to contain more than 99 % of applied radioactivity and consisted of benzo(a)pyrene. The radioactivity dissolved in beer was less than 1 % and the chemical nature could not be identified.     

Balance of conversion and degradation of 2,6-dichlorobenzonitrile -14C in humus soil

In a closed aerated laboratory soil test, volatilization and mineralization of 2,6-dichlorobenzonitrile-¹⁴C is negligible within 61 days. The major soil residues are parent compound, 2,6-dichlorobenzamide and unextractable residues.