Bioremediation of Chlorobenzene-Contaminated Groundwater on Granular Activated Carbon Barriers

During the past decade, various promising technologies have been developed for the decontamination of groundwater insitu which do not require long-term pumping or high energy consumption. One approach is to use funnel and gate technology. In the case described here, the combination of adsorption of contaminants on granular activated carbon (GAC) and its biodegradation is applied to considerably extend the operating time of the filling material in the barrier system. Monochlorobenzene (MCB), a recalcitrant groundwater contaminant under anaerobic conditions, undergoes high-capacity adsorption on GAC up to about 450 mg per gram. Aerobic enrichment cultures, obtained from a contaminated aquifer, were able to mineralize initially adsorbed MCB. In respirometer experiments the rate of carbon dioxide formation was dependent on the equilibrium concentration of MCB. The oxygen consumption of activated carbon by means of autoxidative reactions may delay aerobic biodegradation in GAC filters. The oxygen uptake of pristine activated carbon amounted to 5.6 mg per gram GAC in laboratory column experiments. When GAC was pre-loaded with MCB, autoxidation rates were considerably reduced. Hence, it is advisable not to stimulate the biodegradation of MCB by oxygen supply in GAC biobarriers until after an initial period of solely sorptive MCB removal from the groundwater flow.     

Die Beeinträchtigung aquatischer Ökosysteme durch die Zivilisation

The surface waters of northwestern Europe belong to the most heavily loaded waters of the world. Within the last decades, pollution by non-biogenic organic substances has often become more important than pollution by domestic sewage. Ecologic concepts aid in understanding the various modes of disturbance of aquatic ecosystems. Stream pollution control consists not only of waste treatment.

     

Simultaneous placentacentesis and amniocentesis for prenatal karyotyping: Report on 250 cases

The efficacy and risks of simultaneous transabdominal chorionic villus biopsy (placentacentesis) and amniocentesis in the second and third trimesters were evaluated in 250 singleton pregnancies. The major indications were advanced maternal age (36·0 per cent), abnormal ultrasound findings (23·2 per cent), and low maternal AFP value (17·6 per cent). Nine abnormal karyotypes were found in placental tissue (3·6 per cent). The karyotypes of placental and amniotic cells were different in three cases, including two cases of false-positive mosaicism (08 per cent) and one case of a false-negative result (0·4 per cent) obtained by placental karyotyping. The problem of discrepant karyotypes in embryonic and extra-embryonic tissue does not seem to be restricted to the first trimester. The post-procedure fetal loss rate was estimated as approximately 1·8 per cent. We conclude that the procedure presented here combines the advantages of rapid karyotyping (placentacentesis) and high diagnostic reliability (amniocentesis). It does not seem to be necessary to restrict its use to late presentations and suspicious ultrasound findings.