Bioavailability of HOC depending on the colloidal state of humic substances: a case study with PCB-77 and Daphnia magna.

Condensed organic matter with higher affinity for hydrophobic organic compounds (HOC) is currently held responsible for slow desorption and concomitant lower bioavailabilities of HOC in sediments and soils. In an experiment with Daphnia magna and IHSS Peat Humic Acid (PHA), we showed that the bioconcentration factor (BCF) of 3,3',4,4'-tetrachlorobiphenyl (PCB-77) was directly related to the charge of the humic colloid, as predicted by the metal-humic binding model WHAM. Consistent with the type of binding to the humic acid (counter-ion accumulation vs. specific binding), increasing the concentration of Na+ and Ca2+ ions generated opposite effects on colloid charge and HOC binding by the humic acid. Condensation as a colloidal phenomenon in solution as well as on surfaces needs to be addressed as a contributor to lower bioavailabilities and, possibly, to slower desorption kinetics.

Effective monitoring of small river basins.

As the transport of many pollutants occurs during high floods monitoring programs must focus on these intermittent events. In small rivers the pollutants start their travel as short pulses often associated with fine particles, but disperse on their way downstreams. Therefore the chemical data of a flood event are only representative of a small part of the basin adjacent to the monitoring station. This is usually not taken into account by evaluating water quality data.

[Intravenous methyl iodide poisoning--detoxification using hemoperfusion]. / Intravenöse Methyljodidintoxikation--Detoxikation durch Hämoperfusion.

A 19-year-old patient intending to commit suicide gave himself an intravenous injection of about 14 g methyliodide. The patient was admitted to our hospital in a state of somnolence and agitation followed by a cerebral convulsion and severe hypotension. The serum concentration of methyl iodide was measured by mass spectroscopy. In addition to an antidote therapy with acetylcysteine, haemoperfusion was performed followed by a remarkable decrease of the methyliodide concentration. The patient survived this severe intoxication and was discharged from the hospital after a week.