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The amount of sewage sludge produced worldwide is expected to further increase due to rising efforts in wastewater treatment. There is a growing concern against its direct use as fertilizer due to contamination of the sludge with heavy metals and organic pollutants. Incinerating the sludge degrades organic compounds almost completely and concentrates heavy metals and phosphorus. However, the sewage sludge ash (SSA) is almost completely disposed of and with it all resources are removed from the economic cycle. Comprehensive knowledge of the composition of SSA is crucial to assess the resource recovery potentials. We conducted a survey of all SSA emerging in Germany and determined the respective mass fractions of 57 elements over a period of one year. The median content of phosphorus was 7.9%, indicating an important recovery potential. Important trace elements were Zn (2.5 g/kg), Mn (1.3 g/kg), and Cu (0.9 g/kg). Mass fractions of technology metals such as V, Cr, Ga, Nb, and rare earths were comparatively low. Considering the possible use of SSA as secondary raw material for fertilizer production it should be noted that its Cd and U content (2.7 mg/kg and 4.9 mg/kg respectively) is significantly lower than that of rock phosphate based mineral fertilizers.

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Cyclic voltammetry was used to study the reduction and oxidation behaviour of several pyrimidine cyclobutane dimers mimicking UV induced lesion in DNA strands in polar solvents (N,N-dimethylformamide and acetonitrile). Both electron injection and removal to and from the dimers, respectively, lead to their cleavage and reformation of the monomeric base. The influence of stereochemistry and substitution pattern at the cyclobutane motif on the reactivity has been studied. It appears that the repair process always proceeds in a sequential fashion with initial formation of a dimer ion radical intermediate, which then undergoes ring opening by homolytic cleavage of the two C-C bonds. Standard redox potentials for the formation of both radical anion and radical cation state of the dimers were determined. Quantum calculations on simplified model compounds reveal the reason for the finding that the exergonic homolytic cleavages of the carbon-carbon bonds are endowed with sizeable activation barriers. The consequences of these mechanistic studies on the natural enzymatic repair by photolyase enzyme are discussed.

In order to further elucidate the pathogenesis of the direct carotid cavernous fistulas (dCCF) clinical, patho-anatomical, and physico-mechanical studies were performed. In 27 of 42 patients the dCCF were found to be localized in the segment C4 (according to Teufel, 12), in 13 patients in segment C2 and in only 2 patients in segment C3. The patients with dCCF in segment C4 were significantly younger than those with dCCF in the segments C2 or C3. In none of the patients fractures of the bony walls of the cavernous part of the internal carotid artery (ICA) could be ascertained. On human cadavers it was affirmed that the cavernous branches of the ICA arise nearly exclusively from the top of segment C3 and from the lateral wall of segment C2. The strength of the wall of the cavernous part of the ICA was shown to decline with age as revealed by means of a tensile machine. There were no significant differences between the four segments investigated. As revealed by roentgenograms the distensibility of the ICA within its coverings was shown to be greatest in the segments C2 and C4 and lowest in segment C3. A sudden increase of the intraluminal pressure ruptured the ICA exclusively in the segments C2 and C4. Histological preparations revealed that the trabeculae of the cavernous sinus insert tangentially into the adventitia of the ICA. Taken together these findings strongly support the view that the dCCF are mainly due to a sudden increase of the intraluminal pressure of the ICA.