Dissolved iron(III) speciation in the high latitude North Atlantic Ocean

On voyages in the Iceland Basin in 2007 and 2009, we observed low (ca. 0.1 nM) total dissolved iron concentrations [dFe] in surface waters (<150 m), which increased with depth to ca. 0.2–0.9 nM. The surface water [dFe] was low due to low atmospheric Fe inputs combined with biological uptake, with Fe regeneration from microbial degradation of settling biogenic particles supplying dFe at depth. The organic ligand concentrations [L_T] in the surface waters ranged between 0.4 and 0.5 nM, with conditional stability constants (log K′_FeL) between 22.6 and 22.7. Furthermore, [L_T] was in excess of [dFe] throughout the water column, and dFe was therefore largely complexed by organic ligands (>99%). The ratio of [L_T]/[dFe] was used to analyse trends in Fe speciation. Enhanced and variable [L_T]/[dFe] ratios ranging between 1.6 and 5.8 were observed in surface waters; the ratio decreased with depth to a more constant [L_T]/[dFe] ratio in deep waters. In the Iceland Basin and Rockall Trough, enhanced [L_T]/[dFe] ratios in surface waters resulted from decreases in [dFe], likely reflecting the conditions of Fe limitation of the phytoplankton community in the surface waters of the Iceland Basin and the high productivity in the Rockall Trough.Below the surface mixed layer, the observed increase in [dFe] resulted in a decrease of the [L_T]/[dFe] ratios (1.2–2.6) with depth. This indicated that the Fe binding ligand sites became occupied and even almost saturated at enhanced [dFe] in the deeper waters. Furthermore, our results showed a quasi-steady state in deep waters between dissolved organic Fe ligands and dFe, reflecting a balance between Fe removal by scavenging and Fe supply by remineralisation of biogenic particles with stabilisation through ligands.     

远震数据显示贝加尔裂谷带北穆伊斯克(Severomuysk)段地壳和上地幔的精细结构

通过贝加尔裂谷系统北穆伊斯克(Severomuysk)段的密集地震台站线性网络获得的远距离强震记录,并利用P波接收函数技术,揭示了地壳和上地幔顶部的复杂分层块状结构。横波速度的分布表明构成北穆伊斯克地壳的地块具有不同性质。这些地块的西部聚散和地壳下部的分层证实了该地区隆起的堆积-碰撞起源。位于西伯利亚克拉通变薄的倾斜边缘上的北穆伊斯克段解释了该地区地壳碰撞效应的强度。2015年地震的震中深度与Muyakan 凹陷地壳上部的明显速度差异存在令人信服的相关性。     

Fluvial carbon export and CO2 efflux in representative nested headwater catchments of the eastern La Plata River Basin

This study involved a baseline evaluation of fluvial carbon export and degas rates in three nested rural catchments (1 to 80 km²) in Taboão, a representative experimental catchment of the Upper Uruguay River Basin. Analyses of the carbon content in stream waters and the catchment carbon yield were based on 4‐year monthly in situ data and statistical modeling using the United States Geological Survey load estimator model. We also estimated p CO₂ and degas fluxes using carbonate equilibrium and gas‐exchange formulas. Our results indicated that the water was consistently p CO₂ saturated (~90% of the cases) and that the steep terrain favors high gas evasion rates. The mean calculated fluvial export was 5.4 tC·km^?2·year^?1 with inorganic carbon dominating (dissolved inorganic carbon:dissolved organic carbon ratio >4), and degas rates (~40 tC km^?2·year^?1) were nearly sevenfold higher than the downstream export. The homogeneous land use in this nested catchment system results in similar water‐quality characteristics, and therefore, export rates are expected to be closely related to the rainfall–runoff relationships at each scale. Although the sampling campaigns did not fully reproduce storm‐event conditions and related effects such as flushing or dilution of in‐stream carbon, our results indicated a potential link between dissolved inorganic carbon and slower hydrological pathways related to subsurface water storage and movement.     

Magnetic signature of indoor air pollution: Household dust study

The combination of magnetic and geochemical methods was used to determine the mineralogy, grain size and domain structure of magnetic particles in indoor dust collected in 195 sites in Warsaw, Poland. Data show an asymmetric distribution of magnetic susceptibility (χ) in the wide range of 20–1514 × 10^?8 m³ kg^?1. Comparison of magnetic parameters shows that the internal dust contains outside pollution characteristic for air and soil. More than 90% of indoor dust samples were characterized by roughly uniform magnetic mineralogy, typical for fine grained magnetite (diameter of 0.2–5 μm), and grain size between pseudo-single-domain and small multi-domain with small contribution of superpara-magnetic particles (～10%). Samples with χ larger than 220 × 10^?8 m³ kg^?1 contain mainly magnetite and an anthropogenic metallic Fe with T _C > 700°C. The indoor dust contains, characteristic for the urban areas, spherical magnetic particles originated from fossil fuel combustion processes and mixture of irregular angular iron-oxides grains containing other elements, including Na, Ca, Al, Si, K, S, Mn, Cl, and Mg.     

Towards an Automated Comparison of OpenStreetMap with Authoritative Road Datasets

OpenStreetMap (OSM) is an extraordinarily large and diverse spatial database of the world. Road networks are amongst the most frequently occurring spatial content within the OSM database. These road network representations are usable in many applications. However the quality of these representations can vary between locations. Comparing OSM road networks with authoritative road datasets for a given area or region is an important task in assessing OSM's fitness for use for applications like routing and navigation. Such comparisons can be technically challenging and no software implementation exists which facilitates them easily and automatically. In this article we develop and propose a flexible methodology for comparing the geometry of OSM road network data with other road datasets. Quantitative measures for the completeness and spatial accuracy of OSM are computed, including the compatibility of OSM road data with other map databases. Our methodology provides users with significant flexibility in how they can adjust the parameterization to suit their needs. This software implementation is exclusively built on open source software and a significant degree of automation is provided for these comparisons. This software can subsequently be extended and adapted for comparison between OSM and other external road datasets.     

Structural investigations of the two polymorphs of synthetic Fe-cordierite and Raman spectroscopy of hexagonal Fe-cordierite

The crystal structures of synthetic hexagonal and orthorhombic Fe-cordierite polymorphs with the space groups P6/mcc and Cccm were refined from single-crystal X-ray diffraction data to R _{1, hex}?=?3.14 % and R _{1, ortho}?=?4.48 %. The substitution of the larger Fe²⁺ for Mg leads to multiple structural changes and an increase of the unit cell volumes, with a, c (hex)?=?9.8801(16) Å, 9.2852(5) Å and a, b, c (ortho)?=?17.2306(2) Å, 9.8239(1) Å, 9.2892(1) Å in the end-members. Furthermore Fe incorporation results in an increase of the volumes of the octahedra, although the diameters of the octahedra in direction of the c-axis decrease in both polymorphs. X-ray powder diffraction analysis indicates a high degree of Al/Si ordering in the orthorhombic polymorph, the Miyashiro distortion index is ~0.24. Estimations of site occupancies based on the determined tetrahedral volumes result in the following values for hexagonal Fe-cordierite: ~73 % Al for T₁ and ~28 % Al for T₂. For the first time Raman spectroscopy was performed on the hexagonal Fe-cordierite polymorph. In the hexagonal Fe-cordierite polymorph most Raman peaks are shifted towards lower wavenumbers when compared with the Mg-end-member.     

High-temperature single-crystal neutron diffraction study of natural chondrodite

The H-atom environment in a Tilly Foster chondrodite was analyzed using single-crystal neutron-diffraction data collected at 500, 700 and 900 K and previously published low temperature data collected at 10, 100 and 300 K on the same crystal (Mg_4.64Fe_0.28Mn_0.014Ti_0.023(Si_1.01O₄)₂F_1.16(OH)_0.84; Friedrich et al. in Am Mineral 86:981–989, 2001). The full mean square displacement matrix Σ of the O–H pair was determined from the temperature dependence of the anisotropic displacement parameters, enabling a proper correction of the O–H bond for thermal vibration without assumptions about the correlation of O and H movements. The results show that the perpendicular O–H motions in chondrodite are intermediate between the riding and the independent motion models. The corrected O–H bond lengths do not change with temperature whereas the corrected H···F distances show an increase of ~0.02 Å with temperature, as do the Mg–O distances. This result shows that spectroscopic observations on the strength of the covalent O–H bond cannot be interpreted unambiguously in terms of a corresponding behaviour of the associated H···O/F hydrogen bond.