Adipokines and Incident Type 2 Diabetes in a Canadian Aborigine Population: The Sandy Lake Health and Diabetes Project

OBJECTIVE—The aim of this study was to investigate associations of adiponectin, leptin, C-reactive protein (CRP), interleukin (IL)-6, and serum amyloid A (SAA), individually or in combinations, with risk of incident type 2 diabetes in a Canadian Aborigine population

Risk assessment for arsenic in drinking water: Limits to achievable risk levels

The drinking water standard or maximum contaminant level (MCL) for arsenic is currently being re-evaluated by the US Environmental Protection Agency. The health risk associated with exposure to arsenic through consumption of drinking water is a primary concern in setting a new arsenic MCL. This paper examines the implications of arsenic chemistry, occurrence, and routes of exposure for risk assessment. In order to illustrate the relative importance of exposure through consumption of food and drinking water, the contribution of dietary intake to human exposure to inorganic arsenic was estimated as 2 μg/d. This estimate is based on a total dietary intake of arsenic of 40 μg/d and a 5% contribution of inorganic arsenic to the total dietary intake. This estimated value for dietary intake of inorganic arsenic (2 μg/d) is comparable to the exposure that would result from consumption of 2 l/d of drinking water containing 1 μg/l inorganic arsenic. At lower concentrations of arsenic in drinking water, daily intake of inorganic arsenic becomes increasingly dominated by the dietary contribution. Evaluation of standards for arsenic in drinking water should include careful consideration of exposure through other routes, particularly food consumption

Comparison of arsenic(V) and arsenic(III) sorption onto iron oxide minerals: Implications for arsenic mobility

Arsenic derived from natural sources occurs in groundwater in many countries, affecting the health of millions of people. The combined effects of As(V) reduction and diagenesis of iron oxide minerals on arsenic mobility are investigated in this study by comparing As(V) and As(III) sorption onto amorphous iron oxide (HFO), goethite, and magnetite at varying solution compositions. Experimental data are modeled with a diffuse double layer surface complexation model, and the extracted model parameters are used to examine the consistency of our results with those previously reported. Sorption of As(V) onto HFO and goethite is more favorable than that of As(III) below pH 5-6, whereas, above pH 7-8, As(III) has a higher affinity for the solids. The pH at which As(V) and As(III) are equally sorbed depends on the solid-to-solution ratio and type and specific surface area of the minerals and is shifted to lower pH values in the presence of phosphate, which competes for sorption sites. The sorption data indicate that, under most of the chemical conditions investigated in this study, reduction of As(V) in the presence of HFO or goethite would have only minor effects on or even decrease its mobility in the environment at near-neutral pH conditions. As(V) and As(III) sorption isotherms indicate similar surface site densities on the three oxides. Intrinsic surface complexation constants for As(V) are higher for goethite than HFO, whereas As(III) binding is similar for both of these oxides and also for magnetite. However, decrease in specific surface area and hence sorption site density that accompanies transformation of amorphous iron oxides to more crystalline phases could increase arsenic mobility

Comparative characterization of volcanic ash soils exposed to decade-long elevated carbon dioxide concentrations at Mammoth Mountain, California

Elevated concentrations of soil CO2, ranging from 20% to 90%, from a magmatic source have been killing coniferous trees in the last decade in several distinct areas on the flanks of Mammoth Mountain, California. These areas of elevated soil CO2 provide a natural laboratory to examine how chemical weathering in soils responds to extremely high-CO2 concentrations in conjunction with possible changes in organic acids resulting from vegetation mortality. These volcanic ash soils have a particularly low resistance to chemical weathering due to the predominance of volcanic glass and other noncrystalline phases. Thus, decade-long exposure to anomalous conditions may result in differences in soil characteristics. Soil samples from within the high-CO2 region have been analyzed and compared to samples from outside the anomalous area in the adjacent healthy forest areas where background CO2 concentrations are less than 1%. Compared to the control soil, the high-CO2 soil has lower pH values (5.0 compared to 5.6), higher soil moisture content, and higher surface area. Dithionite-citrate and acid-oxalate extractants were less effective in leaching Al and Si from the high CO2 than from the control soil, indicating a distinct difference in the mineralogy of these soils. The observed differences between the high-CO2 and control soils are consistent with an enhancement of weathering intensity in the soil exposed to elevated CO2 concentrations. © 2002 Elsevier Science B.V. All rights reserved

Factors affecting the dissolution kinetics of volcanic ash soils: Dependencies on pH, CO2, and oxalate

Laboratory experiments were conducted with volcanic ash soils from Mammoth Mountain, California to examine the dependence of soil dissolution rates on pH and CO2 (in batch experiments) and on oxalate (in flow-through experiments). In all experiments, an initial period of rapid dissolution was observed followed by steady-state dissolution. A decrease in the specific surface area of the soil samples, ranging from 50% to 80%, was observed; this decrease occurred during the period of rapid, initial dissolution. Steady-state dissolution rates, normalized to specific surface areas determined at the conclusion of the batch experiments, ranged from 0.03 μmolSim -2h-1 at pH 2.78 in the batch experiments to 0.009 μmolSim-2h-1 at pH 4 in the flow-through experiments. Over the pH range of 2.78-4.0, the dissolution rates exhibited a fractional order dependence on pH of 0.47 for rates determined from H+ consumption data and 0.27 for rates determined from Si release data. Experiments at ambient and 1 atm CO2 demonstrated that dissolution rates were independent of CO2 within experimental error at both pH 2.78 and 4.0. Dissolution at pH 4.0 was enhanced by addition of 1 mM oxalate. These observations provide insight into how the rates of soil weathering may be changing in areas on the flanks of Mammoth Mountain where concentrations of soil CO2 have been elevated over the last decade. This release of magmatic CO2 has depressed the soil pH and killed all vegetation (thus possibly changing the organic acid composition). These indirect effects of CO2 may be enhancing the weathering of these volcanic ash soils but a strong direct effect of CO2 can be excluded. © 2004 Elsevier Ltd. All rights reserved

Rapid oxidation of geothermal arsenic(III) in streamwaters of the eastern Sierra Nevada

Arsenic redox cycling was examined in source waters of the Los Angeles Aqueduct, specifically at Hot Creek, a tributary of the Owens River. Elevated arsenic concentrations in Hot Creek result from geothermal inputs. Total arsenic and As(III) concentrations were determined in the creek and in hot spring pools along its banks. Samples were processed in the field using anion-exchange columns to separate inorganic As(III) and As(V) species. Downstream of the geothermal inputs, decreasing contributions of As(III) to total arsenic concentrations indicated rapid in-stream oxidation of As(III) to As(V) with almost complete oxidation occurring within 1200 m. Based on assumed plug flow transport and a flow velocity of about 0.4 m/s, the pseudo- first-order half-life calculated for this reaction was approximately 0.3 h. Conservative transport of total dissolved arsenic was observed over the reach. Pseudo-first-order reaction rates determined for As(III) oxidation in batch studies conducted in the field with aquatic macrophytes and/or macrophyte surface matter were comparable to the in-stream oxidation rate observed along Hot Creek. In batch kinetic studies, oxidation was not observed after sterile filtration or after the addition of antibiotics, which indicates that bacteria attached to submerged macrophytes are mediating the rapid As(III) oxidation reaction. | Arsenic redox cycling was examined in source waters of the Los Angeles Aqueduct, specifically at Hot Creek, a tributary of the Owens River. Elevated arsenic concentrations in Hot Creek result from geothermal inputs. Total arsenic and As(III) concentrations were determined in the creek and in hot spring pools along its banks. Samples were processed in the field using anion-exchange columns to separate inorganic As(III) and As(V) species. Downstream of the geothermal inputs, decreasing contributions of As(III) to total arsenic concentrations indicated rapid in-stream oxidation of As(III) to As(V) with almost complete oxidation occurring within 1200 m. Based on assumed plug flow transport and a flow velocity of about 0.4 m/s, the pseudo-first-order half-life calculated for this reaction was approximately 0.3 h. Conservative transport of total dissolved arsenic was observed over the reach. Pseudo-first-order reaction rates determined for As(III) oxidation in batch studies conducted in the field with aquatic macrophytes and/or macrophyte surface matter were comparable to the in-stream oxidation rate observed along Hot Creek. In batch kinetic studies, oxidation was not observed after sterile filtration or after the addition of antibiotics, which indicates that bacteria attached to submerged macrophytes are mediating the rapid As(III) oxidation reaction

Influence of Dissolved Sodium and Cesium on Uranyl Oxide Hydrate Solubility

The solubility of uranium-containing minerals can control the mobility of uranium in contaminated soil and groundwater. The identity and solubility of these minerals are strongly influenced by solution composition. The influence of dissolved sodium and cesium on the solubility of uranyl oxide hydrates has been investigated in a series of batch experiments conducted with synthetic metaschoepite ((UO2)8O2(OH) 12·10H2O). During reaction of metaschoepite in NaNO3, CsNO3, and NaF solutions, an initial increase in the dissolved uranium concentration was followed by a decrease as uranium was incorporated into a secondary solid phase. Given sufficient reaction time, metaschoepite was completely transformed to a clarkeite-like sodium uranyl oxide hydrate or a cesium uranyl oxide hydrate that has not previously been described. These secondary solid phases exhibited X-ray diffraction patterns and Raman spectra that were distinct from those of the original metaschoepite. Dissolved uranium concentrations in equilibrium with the sodium and cesium uranyl oxide hydrates can be more than 2 orders of magnitude lower than those in equilibrium with metaschoepite. Initial changes in metaschoepite solubility may also result from particle growth induced by sodium and cesium incorporation into the solid phase

Arsenic occurrence and speciation in municipal ground-water-based supply system

The city of Hanford, California, relies on ground water for its municipal water supply. Arsenic concentrations in local wells frequently exceed the current drinking water standard (50 μg/L), although some dilution is achieved within the distribution system. Water samples were collected from municipal water supply wells and storage tanks in July and December 1996. Total arsenic concentrations ranged from 9 to 75 μg/L. Arsenic was found to occur predominantly in the +III oxidation state. Lower contributions of As(III) to total arsenic concentrations were found in three wells and one storage tank. In all other samples, the percent As(III) was 89 ± 6%. The very low values of %As(III) in one storage tank (1% in July and 14% in December) indicate that As(III) oxidation occurs within the distribution and storage system. | The city of Hanford, California, relies on ground water for its municipal water supply. Arsenic concentrations in local wells frequently exceed the current drinking water standard (50 μg/L), although some dilution is achieved within the distribution system. Water samples were collected from municipal water supply wells and storage tanks in July and December 1996. Total arsenic concentrations ranged from 9 to 75 μg/L. Arsenic was found to occur predominantly in the +III oxidation state. Lower contributions of As(III) to total arsenic concentrations were found in three wells and one storage tank. In all other samples, the percent As(III) was 89 ± 6%. The very low values of %As(III) in one storage tank (1% in July and 14% in December) indicate that As(III) oxidation occurs within the distribution and storage system