We have measured visible wavelength optical properties of the ash from the 1982 El Chichón eruptions. These measurements were made on ash samples collected at three surface sites at distances between 12 and 80 km from the volcano. The most distant sample is taken as most representative of the silicate ash injected into the stratosphere. The measured optical properties are expressed as a complex refractive index n, with the aerosol absorption expressed as the imaginary component of the refractive index, nIM. Each of these samples showed quite low values of absorption, with nIM at 500 nm ranging from 1.5×10−3 for the 12 km sample to 1.0×10−3 for the 80 km sample. Based on these measurements, we estimate that n for the stratospheric silicate ash is given by n = 1.53 ‐ 0.001i.
Miners constitute an underserved, isolated, medically vulnerable, and often underinsured, rural population. 1 In the southwestern United States (US), most miners are Hispanic or American Indian, and high school dropouts. 1 The recent re-emergence of pneumoconioses 2 has created a challenge for rural mining communities in the US. Rural residents also experience a higher prevalence of, and deaths from, chronic obstructive pulmonary disease (COPD) than nonrural residents. 3 Rural miners similarly are at greater risk for COPD and self-reported dust-related lung disease than non-rural miners. 4 The World Health Organization declared coronavirus disease-2019 (COVID-19) a pandemic on March 11, 2020. Although urban areas are disproportionately affected, the disease has spread to rural areas, where its prevention and treatment may be more challenging because of the lower concentration of medical and public health resources. 5 Data indicate that men are more susceptible than women, and that smoking affects outcomes adversely. 4,6 Given that miners, mostly men and often smokers, have a dispoportionately high prevalence of hypertension and diabetes (other risk factors for COVID-19 1,7), miners may constitute a susceptible population for this disease.
Illite/m ontm orillonite (in bulk and in mixed-layer clays) increases during diagenesis, indicating th a t m ontm orillonite is altered to illite. Altering average sedim entary m ontm orillonite layers to average diagenetic illite layers prin cipally involves increasing tetrahedral A1 from alm ost nil to ~2 0 percent. Regarding possible m echanism s: (1) A1 probably cannot displace Si and occupy the sam e tetrah ed ro n ; (2) high-energy barriers undoubtedly exist at subm etam orphic tem peratures to a m echanism requiring disintegration; (3) during dehydration o f m ontm orillonite, some exchangeable cations (with radius < Na+) apparently enter through the " ditrigonal" holes in basal oxygen planes into expanded tetrahedral sites (one hydroxyl ion, three basal oxygen io n s); and (4) the expanded tetrahedral sites contract to norm al 4 C N packing as tetrahedral rotation increases to the theoretical m axim um (30°). The proposed m echanism involves: (a) m igration of interlayer A1 through ditrigonal holes; (b) increased tetrahedral ro tatio n (attraction of basal oxygens tow ard the A1 ions in the expanded te tra h e d ra); (c) creation of perm anent A1 tetrahedra at 30° ro tatio n ; (d) expulsion of an equal num ber o f Si to the inter layer volum e; (e) additional Si m igration along easy paths to new (illite) tetrahedra; (f) hydrogen ion m igration to nearest neighbors within the oxygen-hydroxyl planes; and (g) continued ro tatio n to the illite configuration. Processes (c) through (f) occur sim ultaneously. This m echanism is sterically possible at each structural level. Inherited illite O H -O H angles within in dividual layers depend on the spatial relations between the sets o f tetrahedra vacated in to p and b ottom sheets, and on the original m ontm orillonite OH -79 80 C l a y W a t e r D i a g e n e s i s D u r i n g B u r i a l O H angles. P o o r stacking order in m ontm orillonite predeterm ines the 1 M d illite polytype, as has been observed in early diagenetic illites. The (Al, Si) tetrah ed ra are ordered in the product, illite, within each single-layer dom ain.
Introduction:The re-emergence of pneumoconiosis, particularly among coal miners (ie black lung), in the USA is a challenge for rural communities because more miners require specialized care while expertise is scarce. The Miners' Wellness TeleECHO (Extension for Community Health Outcomes) Clinic, jointly held by the University of New Mexico and a community hospital in New Mexico, provides structured telementoring to professionals caring for miners, including clinicians, respiratory therapists, home health educational approach may help ensure the delivery of high-quality interdisciplinary care to rural miners in pneumoconiosis mortality hotspots in the USA.
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