The unique physicochemical characteristics of geogenic particles induced a proinflammatory response in the lung. These data suggest that particle composition should be considered when setting community standards for PM exposure, particularly in areas exposed to high geogenic particulate loads.
The aim of this study was to assess the influence of season, farm management (organic, biodynamic, integrated, and conventional), and soil chemical, physical, and biological properties on gross nitrogen (N) fluxes and bacterial community structure in the semi-arid region of Western Australia. Moisture availability was the dominant factor mediating microbial activity and carbon (C) and N cycling under this climate. In general, microbial biomass N, dissolved organic N, and potentially mineralisable N were greater in organic and biodynamic than integrated and conventional soil. Our results indicate that greater silt and clay content in organic and biodynamic soil may also partly explain these differences in soil N pools, rather than management alone. Although plant-available N (NH4+ + NO3–) was greater in conventional soil, this was largely the result of higher NO3– production. Multiple linear modelling indicated that soil temperature, moisture, soil textural classes, pH, electrical conductivity (EC), and C and N pools were important in predicting gross N fluxes. Redundancy analysis revealed that bacterial community structure, assessed by denaturing gradient gel electrophoresis of 16S rDNA, was correlated with C and N pools and fluxes, confirming links between bacterial structure and function. Bacterial community structure was also correlated with soil textural classes and soil temperature but not soil moisture. These results indicate that across this semi-arid landscape, soil bacterial communities are relatively resistant to water stress.
Background: There has been renewed interest in the use of silver diamine fluoride (SDF) for the management of carious lesions in high-risk groups. Previous studies have found a difference in clinical efficacy among different concentrations of SDF and discrepancies between ionic concentrations of fluoride (F) and silver (Ag) in SDF preparations. The aim of this study was to measure the free F, Ag ion concentrations and pH of a variety of commercially available SDF preparations. Methods: Seven SDF products used globally were evaluated for F and Ag ion concentrations using a calibrated ion-selective electrode and optical emission spectrometry respectively. Acidity was determined with a pH electrode. Results: The 30% SDF solution contained almost half the F concentration and a much higher Ag concentration than expected (16 343 ppmF and 246 000 ppmAg). Comparatively, the mean F concentration of the remaining six 38% solutions was 74 802 ppm (expected mean 44 800 ppm) ranging from 36 457 ppm to 120 760 ppm. The mean Ag concentration was 326 000 ppm (expected mean 253 870 ppm) and ranged from 246 000 ppm to 425 451 ppm. All solutions were found to be neutral or mildly alkaline in nature (pH 7-10.3). Conclusions: Wide variations between claimed and measured F and Ag ion concentrations exist among the different brands of commercially available SDF products.
Twenty nine Fe oxide concentrates of Thai soils formed on basalt, sandstone, shale/limestone and granite were investigated. Goethite and hematite are relatively more abundant in granitic and basaltic soils, respectively. Values of Feo/Fed range from 0.01 to 0.28 indicating that free Fe oxides are mostly crystalline.There are no systematic differences in unit-cell dimensions for goethite and hematite in soils on different parent materials. Mean crystallite dimensions calculated from the 110 reflections are greater for hematite than for goethite. Aluminium substitution varies from 8 to 24 mole% for goethite and from 4 to 17 mole% for hematite. The dehydroxylation temperature for goethite ranges from 285ºC to 320ºC. The goethite in basaltic soils has a smaller crystal size and Al substitution, as well as a lower dehydroxylation temperature, compared to soils on other parent materials. The dehydroxylation temperature of goethite is positively related to Al substitution (R = +0.58), MCD110 (R = +0.49) and Ald (R = +0.53). The Mn, Ni, Cr, V and P in these soils occur in Fe oxides rather than as discrete minerals.
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