Evaluation of fluidized bed asbestos segregator to determine erionite in soil     

Daniel Farcas  Martin Harper  Jed W. Januch  Teri A. Jacobs  Khachatur Sarkisian  Larry D. Stetler  Diane Schwegler-Berry 《Environmental Earth Sciences》2017,76(3):126

Three sets of soil samples were collected by the National Institute for Occupational Safety and Health and one set by South Dakota School of Mines & Technology from in and around the Slim Buttes Land Unit of the Sioux Ranger District of the Custer–Gallatin National Forest in the northwest of South Dakota. The rocks forming the Slim Buttes are sedimentary clays, sands and gravels including re-worked volcanic ash-falls in which the zeolite mineral erionite has crystallized during diagenesis in a fibrous form or morphology similar to that of asbestos. The samples were prepared using the fluidized bed asbestos segregator (FBAS) and analyzed by phase contrast microscopy (PCM) or transmission electron microscopy to detect the presence of mineral fibers. FBAS–PCM results compared to semi-quantitative polarized light microscopy (PLM) and X-ray diffraction analysis indicated a recovery of approximately 1% and a linear relationship that likely can be extrapolated to concentrations well below the 1% detection limit of PLM. There were small variations between a PCM count of 10 fibers to a count of 100 fibers (or a maximum of 200 microscopic fields of view), which indicates the possibility of rapid turnaround of results. Although the four sets of samples examined in this work were collected by slightly different techniques, some tentative conclusions can be drawn about the distribution of erionite in soils. Erionite was detected in almost every soil sample, even those taken several miles from the outcrop, but without any distribution indicating recent transportation from the current volcaniclastic sediment outcrops. Removal of more extensive volcaniclastic sediments through erosion may have resulted in remnant material in soils, including erionite crystals, but this possibility requires further study. Although we have demonstrated that erionite in soils can be detected through FBAS–PCM, we have not attempted to correlate those results with human inhalation exposure through activity-based sampling, and thus, any risk inherent in working these soils is unknown.  相似文献   

Pinched between the plates: Armenia's voluminous record of volcanic activity     

Ralf Halama  Khachatur Meliksetian  Ivan P. Savov  Patrick J. Sugden  Krzysztof Sokół 《Geology Today》2020,36(3):101-108

Located in the heart of the Lesser Caucasus mountains, where the Arabian and Eurasian tectonic plates collide, Armenia occupies an exceptional geological position shaped through millions of years of subduction and collision. It is a unique place on the Earth recording extensive intrusive and volcanic activity related to the long-standing continental convergence. The volcanoes of Armenia provide a rare opportunity to study the sources and processes involved in this unusual type of magmatism. More than 500 Quaternary volcanoes have been mapped in Armenia, most of them formed from single eruptive episodes. Among several large composite volcanoes, the mighty Aragats stands out as the largest volcano in Armenia and the region altogether. Volcanic deposits testify to the range of eruptive styles—from the ignimbrites formed in eruptions as explosive and voluminous as any seen globally in the modern era to the enormous fissure-fed lava flows that form the Southern Caucasus flood basalt province, the smallest and youngest Large Igneous Province in the world. Several pre-historical and historical eruptions have been documented, highlighting the potential for future volcanic activity in the region. In recent years, research has focused on the volcanic hazards associated with the Armenian Nuclear Power Plant, located in the foothills of Aragats volcano. This article highlights some of the extraordinary volcanic and intrusive features observed in Armenia and summarizes aspects of recent volcanological and petrological research.  相似文献