Behavior of PAHs during cold storage of historically contaminated soil samples

The stability of historically polycyclic aromatic hydrocarbon (PAH)-contaminated soils during cold storage was investigated. Samples from two former manufactured gas plants exhibited quantitative recoveries of PAHs over the whole period of sample holding at 4 °C in the dark (8–10 months), whereas significant losses of PAHs were observed for soils received from a former railroad sleeper preservation plant with low molecular weight compounds being notably more affected compared to heavier PAHs. Already after 2 weeks of holding time, 3-ring PAHs in one of theses samples were down to 29–73% of the initial concentration and significant losses were observed for up to 5-ring compounds. Dissipation of PAHs was found to be predominantly due to aerobic microbial metabolism since sodium azide poisoned samples showed quantitative recoveries for all PAHs over the entire storage time of 3 months. A similar stabilizing effect was observed for freezing at −20 °C as means of preservation. Except for acenaphthene, no significant loss for any of the PAHs was observed over 6 weeks of holding time. Eventually, selected chemical, physical, and biological parameters of two soils were investigated and identified as potential indicators for the stability of PAH-contaminated soil samples.     

Bioremediation of chlorobenzene-contaminated ground water in an in situ reactor mediated by hydrogen peroxide

New in situ reactive barrier technologies were tested nearby a local aquifer in Bitterfeld, Saxonia-Anhalt, Germany, which is polluted mainly by chlorobenzene (CB), in concentrations up to 450 microM. A reactor filled with original aquifer sediment was designed for the microbiological remediation of the ground water by indigenous bacterial communities. Two remediation variants were examined: (a) the degradation of CB under anoxic conditions in the presence of nitrate; (b) the degradation of CB under mixed electron acceptor conditions (oxygen+nitrate) using hydrogen peroxide as the oxygen-releasing compound. Under anoxic conditions, no definite degradation of CB was observed. Adding hydrogen peroxide (2.94 mM) and nitrate (2 mM) led to the disappearance of CB (ca. 150 microM) in the lower part of the reactor, accompanied by a strong increase of the number of cultivable aerobic CB degrading bacteria in reactor water and sediment samples, indicating that CB was degraded mainly by productive bacterial metabolism. Several aerobic CB degrading bacteria, mostly belonging to the genera Pseudomonas and Rhodococcus, were isolated from reactor water and sediments. In laboratory experiments with reactor water, oxygen was rapidly released by hydrogen peroxide, whereas biotic-induced decomposition reactions of hydrogen peroxide were almost four times faster than abiotic-induced decomposition reactions. A clear chemical degradation of CB mediated by hydrogen peroxide was not observed. CB was also completely degraded in the reactor after reducing the hydrogen peroxide concentration to 880 microM. The CB degradation completely collapsed after reducing the hydrogen peroxide concentration to 440 microM. In the following, the hydrogen peroxide concentrations were increased again (to 880 microM, 2.94 mM, and 880 microM, respectively), but the oxygen demand for CB degradation was higher than observed before, indicating a shift in the bacterial population. During the whole experiment, nitrate was uniformly reduced during the flow path in the reactor.     

Assessment of Bacillus subtilis spores as a possible bioindicator for evaluation of the microbicidal efficacy of radiation processing of water.

Gamma and electron-beam irradiation of Bacillus subtilis spores suspended in different types of water was studied to evaluate the inactivation of the spores and assess their possible use as a bioindicator for radiation processing. We found that the inactivation proceeded endogenously, being dose-rate-dependent and affected by oxygen. The radiation resistance of the suspended spores was found to be rather high; therefore, B. subtilis spores used as a bioindicator for efficiency of water treatment by radiation under practical conditions might result in the spores being overly conservative surrogates for pathogenic microorganisms. Moreover, the doserate dependency impedes the use of the spores as a bioindicator. Thus, B. subtilis spores cannot be recommended as a bioindicator for evaluation of the microbicidal efficacy of ionizing radiation processing of water.     

Teil 3: PCDD/F im Blutfett ausgewählter Personen

This study was designed to assess the degree of exposure to PCDD/F in 56 selected persons living in the vicinity of a former copper smelter located in Marsberg, Germany. The copper smelter was in operation until 1945. In 1991, high levels of PCDD/F were found particularly in materials from the slag dumps (10 000 – 100 000 ng TE/kg). The levels of PCDD/F in blood fat were used as parameters for individual PCDD/F exposure. Since only limited reference data for PCDD/F in human blood were available, blood samples of a reference group were analyzed in the same way. The criteria were collected from a group matched for sex, age (±3 years) and body mass. The median NATO/CCMS-Toxicity equivalency values (NATO/CCMS-TE-values) of the Marsberg group (43,2 pg NATO/CCMS-TE/g blood fat) and the reference group (43,0 pg NATO/CCMS-TE/g blood fat) were similar, whereas the arithmetic mean of the Marsberg group (52,7 pg NATO/CCMS-TE/g blood fat) was higher than that of the reference group (44,4 pg NATO/CCMS-TE/g blood fat). The frequency distribution of the individual TE-values of the Marsberg group was slightly shifted toward higher values. The individuals of the Marsberg group had significantly higher levels of PentaCDF, HexaCDF and HeptaCDF on average than the individuals of the reference group. On the basis of TE-values, the majority of the individuals from Marsberg did not have an increased body burden of PCDD/F. However, some individuals could be identified with TE-values exceeding background levels ranging up to 231 pg NATO/CCMS-TE/g blood fat. Although it must be assumed that the unusual congener pattern found in many of the test subjects is a result of ingestion of contaminated slag material or soil, the findings of this study could not verify this fact.     

Abundance of 14C in biomass fractions of wastes and solid recovered fuels

In recent years thermal utilization of mixed wastes and solid recovered fuels has become of increasing importance in European waste management. Since wastes or solid recovered fuels are generally composed of fossil and biogenic materials, only part of the CO₂ emissions is accounted for in greenhouse gas inventories or emission trading schemes. A promising approach for determining this fraction is the so-called radiocarbon method. It is based on different ratios of the carbon isotopes ¹⁴C and ¹²C in fossil and biogenic fuels. Fossil fuels have zero radiocarbon, whereas biogenic materials are enriched in ¹⁴C and reflect the ¹⁴CO₂ abundance of the ambient atmosphere. Due to nuclear weapons tests in the past century, the radiocarbon content in the atmosphere has not been constant, which has resulted in a varying ¹⁴C content of biogenic matter, depending on the period of growth. In the present paper ¹⁴C contents of different biogenic waste fractions (e.g., kitchen waste, paper, wood), as well as mixtures of different wastes (household, bulky waste, and commercial waste), and solid recovered fuels are determined. The calculated ¹⁴C content of the materials investigated ranges between 98 and 135 pMC.