Composition of individual nitrate-containing particles in non-urban atmospheres of Colorado,U.S.A. and Tel Aviv,Israel

Nitrate-containing aerosols, collected on Nuclepore filters and electron microscope screens, precoated with nitron, cause characteristic reaction patterns that can be identified by scanning and transmission electron microscope (STEM). Interfacing the STEM with an X-ray energy analyzer and selected area electron diffraction permits the simultaneous detection of elements of atomic number larger than 11 and of minerals in individual aerosols. In an application of this technique to aerosols collected at the Boulder Atmospheric Observatory and at Tel Aviv University, the aerosols were found associated with wet crustal particles. They were found as minerals and air pollution aerosols containing one or a combination of several elements. The precoated electron microscope screens, permitted elemental analysis of individual micrometer-size particles providing new information on the characterization of aerosols mainly the presence of water that can not be obtained by bulk analysis commonly employed in the study of nitrates.     

Micromorphology of sediments from Hayonim Cave,Israel

Hayonim Cave, situated in the western part of Upper Galilee is a solution cavity formed in limestone and filled with a partly cemented mixture of stony and slightly silty clays. Prehistoric industries range from Mousterian (ca. 80,000 to 40,000 BP) at the base, to Natufian (ca. 10,000 BP) whose burials are dug into the underlying Upper Palaeolithic and Kebaran deposits, a one to two meter accumulation of Byzantine ash, with guano and clays rich in organic matter capping the sequence.Micromorphological investigation, using principally the terminology of BREWER, was undertaken to describe systematically the sediments and to interpret the depositional and palaeoenvironmental history of the cave sediments. Skeleton components (including litho- and pedo-relicts) consist of limestone fragments, bone, quartz silt, chert and abundant rounded red clay clumps that contain quartz silt and bone inclusions. Other items are burnt wood, phytoliths (?) and carnivore (Hyaena?) faecal remains. Plasma, mostly localized in the form of clumps, is predominantly red clay with argillasepic and mosepic plasmic fabrics. With the exception of the quartz silt which was blown into the cave, most of the skeleton material is biogenic or anthropogenic in origin.Post-depositional modification is represented by cementation with calcite micrite and sparite, and precipitation of vugh-type collophane (hydroxyapatite). Calcite cementation is found in the Mousterian, in the center of the cave, and in the Kebaran, near the cave entrance, suggesting possibly moister environments during these periods.     

Ten years of precipitation chemistry in Haifa,Israel

Rain event samples have been collected in Haifa, Israel, for nine hydrological years 1981 to 1990. Precipitation amount, pH, SO₄ ⁼, NO₃ ^?, Cl^?, NH₄ ⁺, Na⁺, K⁺, Ca⁺⁺, Mg⁺⁺ and alkalinity of rainwater samples were recorded. The sampling and analysis program was based on WMO recommendations for background networks. The sampling was performed manually, and the analysis was based on wet chemistry for ions and atomic absorptions for metals. Data of 187 rain samples showed that the average pH was 5.3±1.1∶ 26% of the rain events were below pH of 5.6 and 23% above pH of 7.0. Some simple chemical mass-balance considerations indicate that natural sources, sea salt and soil carbonates are the main contributors to rain chemistry. However, the presence of low pH events observed over the years suggests that the impact of anthropogenic emissions may overwhelm the buffering capacity of the alkaline aerosol.