نتایج جستجو برای: carbonaceous phosphorites
تعداد نتایج: 4406 فیلتر نتایج به سال:
This study focuses on sulphurous and carbonaceous aerosol, the major constituents of particulate matter in the lowermost stratosphere (LMS), based on in situ measurements from 1999 to 2008. Aerosol particles in the size range of 0.08 2 mm were collected monthly during intercontinental flights with the CARIBIC passenger aircraft, presenting the first long-term study on carbonaceous aerosol in th...
Comprehensive carbonaceous aerosol characterization P. Herckes et al.
Nitrogen content and isotopic composition of carbonaceous-rich metasediments were determined by online and sealed-tube combustion using ultra-high vacuum line and static mass spectrometer adapted to analyse nitrogen nanomoles. Accurate measurements showed that nitrogen amount released by on-line combustion technique was underestimated to various extents. As a result, the nitrogen isotopic compo...
A suite of 47 carbonaceous, enstatite, and ordinary chondrites are examined for Re-Os isotopic systematics. There are significant differences in the Re/Os and Os/Os ratios of carbonaceous chondrites compared with ordinary and enstatite chondrites. The average Re/Os for carbonaceous chondrites is 0.392 0.015 (excluding the CK chondrite, Karoonda), compared with 0.422 0.025 and 0.421 0.013 for or...
Putative microbialites are commonly regarded to have formed in association with photosynthetic microorganisms, such as cyanobacteria. However, many modern microbial mat ecosystems are dominated by chemotrophic bacteria and archaea. Like phototrophs, filamentous sulfur-oxidizing bacteria form large mats at the sediment/water interface that can act to stabilize sediments, and their metabolic acti...
NASA’s Dawn spacecraft observations of Asteroid (4) Vesta reveal a surface with the highest albedo and color variation of any asteroid we have observed so far. Terrains rich in low albedo dark material (DM) have been identified using Dawn Framing Camera (FC) 0.75 lm filter images in several geologic settings: associated with impact craters (in the ejecta blanket material and/or on the crater wa...
The naturally occurring carbonaceous material (CM) in gold bearing ores often exhibits strongpreg-robbing properties. It can adversely affect the process of gold recovery during the cyanidation due to its ability to adsorb, or preg-rob gold from the cyanide leach solution. Treatments of carbonaceous ores with chemical surfactants as blinding agents to limit pregrobbing have shown promising resu...
Carbonaceous aerosols are responsible for large uncertainties in climate models, degraded visibility, and adverse health effects. The Carbonaceous Aerosols and Radiative Effects Study (CARES) was designed to study carbonaceous aerosols in the natural environment of the Central Valley, California, and learn more about their atmospheric formation and aging. This paper presents results from spectr...
Cadmium occurs in the earth’s crust at a concentration of 0.1–0.5 ppm and is commonly associated with zinc, lead, and copper ores. It is also a natural constituent of ocean water with average levels between <5 and 110 ng/L, with higher levels reported near coastal areas and in marine phosphates and phosphorites. The cadmium concentration of natural surface water and groundwater is usually <1 μg...
Phosphate minerals hydroxylapatite, fl uorapatite and crandallite were identifi ed in nodules within phosphorites from Ervenik, Croatia. The minerals were identifi ed using optical microscopy, XRD, SEM and EDS analyses. The presence of fungi was recognized only in association with phosphate-rich phases. Fungal activity resulted in the dissolution of apatite, producing hollow crystals, particula...
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