A 50-year record of NOx and SO2 sources in precipitation in the Northern Rocky Mountains, USA

Ice-core samples from Upper Fremont Glacier (UFG), Wyoming, were used as proxy records for the chemical composition of atmospheric deposition. Results of analysis of the ice-core samples for stable isotopes of nitrogen (δ15N, ) and sulfur (δ34S, ), as well as and deposition rates from the late-1940s thru the early-1990s, were used to enhance and extend existing National Atmospheric Deposition Program/National Trends Network (NADP/NTN) data in western Wyoming. The most enriched δ34S value in the UFG ice-core samples coincided with snow deposited during the 1980 eruption of Mt. St. Helens, Washington. The remaining δ34S values were similar to the isotopic composition of coal from southern Wyoming. The δ15N values in ice-core samples representing a similar period of snow deposition were negative, ranging from -5.9 to -3.2 ‰ and all fall within the δ15N values expected from vehicle emissions. Ice-core nitrate and sulfate deposition data reflect the sharply increasing U.S. emissions data from 1950 to the mid-1970s

Highly Sensitive Fluorescence Probe Based on Functional SBA-15 for Selective Detection of Hg2+

An inorganic–organic hybrid fluorescence chemosensor (DA/SBA-15) was prepared by covalent immobilization of a dansylamide derivative into the channels of mesoporous silica material SBA-15 via (3-aminopropyl)triethoxysilane (APTES) groups. The primary hexagonally ordered mesoporous structure of SBA-15 was preserved after the grafting procedure. Fluorescence characterization shows that the obtained inorganic–organic hybrid composite is highly selective and sensitive to Hg2+ detection, suggesting the possibility for real-time qualitative or quantitative detection of Hg2+ and the convenience for potential application in toxicology and environmental science

Assessment of Spatial Variability of Major-Ion Concentrations and DEL Oxygen-18 Values in Surface Snow, Upper Fremont Glacier, Wyoming, U.S.A.

One hundred samples were collected from the surface of the Upper Fremont Glacier at equally spaced intervals defined by an 8,100 m2 snow grid to assess the significance of lateral variability in major-ion concentrations and del oxygen-18 values. For the major ions, the largest concentration range within the snow grid was sodium (0.5056 mg/l) and the smallest concentration range was sulfate (0.125 mg/l). Del oxygen-18 values showed a range of 7.45 per mil. Comparison of the observed variability of each chemical constituent to the variability expected by measurement error indicated substantial lateral variability within the surface-snow layer. Results of the nested ANOVA indicate most of the variance for every constituent is in the values grouped at the two smaller geographic scales (between 506 m2 and within 506 m2 sections). Calcium and sodium concentrations and del oxygen-18 values displayed the largest amount of variance at the largest geographic scale (between 2,025 m2 sections) within the grid and ranged from 14 to 26 per cent of the total variance. The variance data from the snow grid were used to develop equations to evaluate the significance of both positive and negative concentration/value peaks of nitrate and del oxygen-18 with depth, in a 160 m ice core. Solving the equations indicates that both the nitrate and del oxygen-18 ice-core profiles have concentration/value trends that exceed the limits expected from lateral variability. Values of del oxygen-18 in the section from 110-150 m below the surface consistently vary outside the expected limits and possibly represents cooler temperatures during the Little Ice Age from about 1810 to 1725 A.D.</jats:p