Radiocarbon in Porewater of Continental Shelf Sediments (Southeast Mediterranean)

From the 18th International Radiocarbon Conference held in Wellington, New Zealand, September 1-5, 2003.In this study, we aim to characterize the main processes controlling 14CDIC concentrations in porewater at the shallow shelf (water depth less than 120 m) off the Mediterranean coast of Israel. At these water depths, we expected to find evidence for seawater penetration toward the coast, since this area was flooded by seawater only some 18,000 yr ago (the end of the Last Glacial period). Measurements of the chemical composition (14CDIC) and stable carbon isotopic composition (delta-13CDIC) were performed in several sediment cores (40-250 cm long) at water depths between 6 and 115 m. At water depths of 60 m, represented by a 2.5-m-long sediment core, the porewater 14CDIC levels (85-87 pMC) were lower than the corresponding sediment values in each layer (92-95 pMC), mainly due to the oxidation of relatively old organic matter (about 70 pMC) with no evidence to advection. In contrast, sediment cores from water depths shallower than 50 m showed only slight anaerobic oxidation and high 14CDIC values of approximately 100 pMC, indicating possible downward advection. These geochemical observations support the perception that the penetration of seawater into the coastal aquifer occurs at the shallow water zone (<50 m), while further verification by deeper cores is required.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Distribution of Pine Woolly Adelgids Infestation on Pinus merkusii Plantation in Java

Pine woolly adelgid is a recently found exotic pest attacking seedling up to grown plants of Pinus merkusii plantations forest. Since its discovery, there were not much information about it.&nbsp; The objectives of this research were to study pine woolly adelgids distribution, symptoms and indicators, and its scale of infestations on Pinus merkusii plantation in Java, to determine the presence of any specific P. merkusii sites invaded by pine woolly adelgids, considering the pests were native to boreal and temperate areas.&nbsp; Hypothesis was pine woolly adelgids infestation on P. merkusii in Java is consistent with their native distribution.&nbsp; There were 9 Forest Management Unit (KPH) with infested P. merkusii plantations which were located at altitude between 900 to 1,700 m asl. with temperature ranging 16-22 ˚C and air humidity 80-90%. This indicated that Pine Woolly Adelgids required low temperature to survive, which was consistent with their original distribution. Host preference with regard to scale of infestation was closely related to temperature, altitude, and number of trees per hectare. The scale of infestation varied among regions, from light to heavy infested/death of trees.Keywords: pine woolly adelgid, Pinus merkusii, scale of infestation, host preference

Effect of metallic aggregate and cement content on abrasion resistance behaviour of concrete

Many concrete structures are required to have sufficient abrasion resistance, such as dams, canals, roads and floors. The abrasion resistance of concrete may be defined as its ability to resist being worn away by rubbing. Compressive strength and aggregate type are also important factors affecting the abrasive behaviour of concrete. However, very little information on the properties of haematite containing concrete has been reported. The authors report on the abrasion resistance of concrete with four different cement contents (300, 350, 400 and 450 kg m(-3)) and with haematite as a metallic aggregate with replacement ratios of 15, 30, 45 and 60\% under 5, 10 and 15 kg loads. The water/cement ratio was kept constant at 0.40 to evaluate the effects of haematite and cement content. Slump tests were conducted to evaluate the workability of fresh concretes. For hardened concrete samples, mechanical tests such as compressive strength, splitting tensile strength, unit weight and wear resistance were performed. Along with the physical and mechanical properties of concretes, haematite was studied as a mineral. Increasing both cement and haematite content has substantial effects on the strength of the concrete. Polarising microscopy views of the interfaces show that haematite aggregates exhibit greatly improved bond strength. Wear loss of concrete decreases with increasing concentration of haematite, while it increases with increasing cement content. An equation representing wear as a function of cement content, compressive strength and also applied load provides virtually perfect agreement with the experimental results