Factors affecting denitrification during infiltration of river water into a sand and gravel aquifer in Saxony, Germany

River infiltration into a sand and gravel aquifer was investigated to assess the importance of denitrification in maintaining low-NOS groundwater supplies. Samples from the River Elbe and groundwater sampling points along a section of the aquifer were analysed for dissolved organic carbon, major ions and the 15N/14N isotopic ratio of dissolved NO3-. Input of NOS to the aquifer is influenced by seasonal, temperature-dependent denitrification in the river bed sediments. Along an upper flowpath in the aquifer from the River Elbe to a sampling point at a distance of 55 m, the median NO3- concentration decreased by 4.8 mg litre-1 and the δ15N composition increased by +9.0‰, consistent with denitrification. Similar isotopic enrichment was demonstrated in a laboratory column experiment with a reduction in NO3- of 10.5 mg litre-1 for an increase in δ15N of +9.8‰, yielding an isotopic enrichment factor of ~ 14.6‰. A mass balance for denitrification shows that oxidizable organic carbon required for denitrification is derived from both the infiltrating river water and solid organic matter fixed in the river bed sediments and aquifer material

Gas chromatographic analysis of volatile hydrocarbons to detect irradiated chicken, pork and beef - an intercomparison study A report in English and German

This report provides a detailed description of an inter-laboratory study to detect irradiation treatment of chicken carcasses, pork and beef using a method suitable for routine application. The 17 participating laboratories determined the quantity of four different radiation-induced hydrocarbons (1-tetradecene, pentadecane, 1,7-hexadecadiene, 8-heptadecene) in coded samples approx. 3 and 6 months after irradiation. The quantities detected were used to identify the samples as irradiated or non-irradiated. The samples of each type of meat to be examined had been supplied by two different producers. The dose range that was tested (approx. 0.6 to 7.5 kGy) included commercially used doses (approx. 1 to 5 kGy). The method employed enable 98.3% of a total of 864 samples to be correctly identified as irradiated or non-irradiated. This result is remarkable: Although the marker concentrations in the various samples showed a clear dose dependency, the variation was quite marked. The high rate of correct identifications could be achieved by defining a sample only as irradiated if certain quantities of at least 3 of the radiolytic products to be determined had been found. A similar identification rate was achieved if quantification of markers was omitted to identify a sample only as irradiated when all the expected radiolysis products could be clearly detected. For all three types of meat, no significant differences in marker yields could be shown for the products of the respective two producers. Also, in none of the types of meat, any significant difference could be revealed for the quantiatitive results achieved three and six months after irradiation. These results show that irradiation of chicken carcasses, pork and beef in the commerically used dose range can be clearly detected throughout the entire period in which products are normally stored and that the method described is suitable for routine analyses in food control laboratories. (orig.)Available from TIB Hannover: RR 1068(1993,1) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman