Organic carbon and humic substances contents, carbon isotope composition and peroxidase activity in sediments from DSDP Sites 15-147 and 75-532

Sediment samples from the Cariaco Trench (DSDP Leg 15) and the Walvis Ridge (DSDP Leg 75) ranging in age from Holocene to Upper Miocene (approximately 8 million years BP) and in depth from 5 to 258 m were extracted with basic sodium pyrophosphate and the extract analyzed for enzymic activity. Since no dehydrogenase, alkaline phosphatase or esterase activity was found, it is estimated from these data that the maximum bacterial population does not exceed 1000 cells per gram dry sediment. Peroxidase activity was, however, found in most samples: this showed marked dependence on the humic substance concentration (expressed as percent of the organic carbon content) and increased with depth at a rate of 33 units per meter. To explain this observation, we favor an hypothesis based on the presence of active humic-enzyme association. The humic substances absorb and stabilize peroxidase which is liberated throughout the sediment column by lysis of cells. The association of the enzyme with the humic substances protects it from biodegradation and denaturation. This hypothesis agrees with laboratory experiments which show the enhanced stability of humic-enzyme complexes towards degradation by biological, chemical and thermal effects

Dead Sea Asphalt from the Excavations in Tel Arad and small Tel Malhata

Asphalt was found in the excavations of Tel Arad and Small Tel Malhata in the Northern Negev, Israel, in levels dated as Early Bronze I and II. Detailed chemical analysis indicates that this material, used as a glue on various utensils, resembles natural occurrences of asphalt blocks which are occasionally found floating on the Dead Sea. Although the historical records of 2000 years ago indicate that Dead Sea asphalt has been an important trade item of the region, this is the first evidence that Dead Sea material can be found outside its source area. It also indicates that the export of Dead Sea asphalt had begun at least 3000 years before the earliest historical record by Diodorus of Sicily (ca. 50 A.D.).Du bitume a été trouvé au cours de fouilles de Tell Arad et du petit Tell Malhata dans le nord du Néguev, en Israël, dans les niveaux datés du Bronze Ancien I et II. L'analyse chimique indique que ce bitume, utilisé sur des objets divers, est de même nature que les blocs de bitume que l'on trouve parfois flottant à la surface de la Mer Morte. Les textes anciens mentionnent que le bitume de la Mer Morte était une denrée d'exportation importante de la région il y a deux mille ans; le bitume de Tell Arad et du petit Tell Malhata est le premier témoin de ce matériau en dehors de son lieu d'origine. Il indique aussi que le commerce du bitume de la Mer Morte a commencé au moins 3000 ans avant l'apparition de la première mention historique faite par Diodore de Sicile vers l'an 50 de notre ère.Nissenbaum Arie, Serban Andrei, Amiran Ruth, Ilan Ornit. Dead Sea Asphalt from the Excavations in Tel Arad and small Tel Malhata. In: Paléorient, 1984, vol. 10, n°1. pp. 157-161