pilot commanded maneuvering without adverse characteristics, such as departures, requiring the pilot’s attention . Then, there is a discussion of... Loaded Actuator Frequency Response 136 Figure 5.3.4 Actuator Model with and without Control Module Dynamics 137 Figure 5.3.5 Object diagram of HIRM 141...obvious, and frequently the most important, is that the direct connection between the pilot and the control surfaces is not there. Special attention is
Gune, Minal; Harshavardhana, B G; Balakrishna, K; Udayashankar, H N; Shankar, R; Manjunatha, B R
We present seasonal rock magnetic data for 48 surficial soil samples collected seasonally around a coal-fired thermal power plant on the southwest coast of India to demonstrate how fly ash from the power plant is transported both spatially and seasonally. Sampling was carried out during pre-monsoon (March), early-monsoon (June), monsoon (September) and post-monsoon (December) seasons. Low- and high-frequency magnetic susceptibility (χlf and χhf), frequency-dependent magnetic susceptibility (χfd), χfd %, isothermal remanent magnetization (IRM), "hard" IRM (HIRM), saturation IRM (SIRM) and inter-parametric ratios were determined for the samples. Scanning electron microscopy (SEM) was used on limited number of samples. NOAA HYSPLIT MODEL backward trajectory analysis and principal component analysis were carried out on the data. Fly ash samples exhibit an average HIRM value (400.07 × 10(-5) Am(2) kg(-1)) that is comparable to that of soil samples. The pre- and post-monsoon samples show a consistent reduction in the concentration of magnetically "hard" minerals with increasing distance from the power plant. These data suggest that fly ash has indeed been transported from the power plant to the sampling locations. Hence, HIRM may perhaps be used as a proxy for tracking fly ash from coal-fired thermal power plants. Seasonal data show that the distribution of fly ash to the surrounding areas is minimum during monsoons. They also point to the dominance of SP magnetite in early-monsoon season, whereas magnetic depletion is documented in the monsoon season. This seasonal difference is attributable to both pedogenesis and anthropogenic activity i.e. operation of the thermal power plant.
Sediments from ODP site 1063 (Bermuda Rise, North Atlantic) contain a high-resolution record of geomagnetic field behavior during the Brunhes Chron. We present rock magnetic data of the upper 160 mcd (<900 ka) from hole 1063D that show magnetic properties vary in concert with glacial cycles. Magnetite appears to be the main magnetic carrier in the carbonate-dominated interglacial horizons, yet exhibits contrasting grain size distributions depending on the redox state of the horizons. Higher contributions of single domain magnetite exist above the present day sulfate reduction zone (ca. 44 mcd) with relatively higher multidomain magnetite components below that likely arise from the partial dissolution of SD magnetite in the deeper, anoxic horizons. Glacial horizons on the other hand, characterized by enhanced terrigenous deposition, show no evidence for diagenetic dissolution but do indicate the presence of authigenic greigite close to glacial maxima (acquisition of gyro-remanence, strong magnetostatic interactions and SD properties). Glacial horizons contain hematite (maxima in HIRM and S-Ratio consistent with a reddish hue) and exhibit higher ARM anisotropy and pronounced sedimentary fabrics. We infer that post depositional processes affected the magnetic grain size and mineralogy of Bermuda rise sediments deposited during the late Pleistocene. Hematite concentration is interpreted to reflect primary terrigenous input that is likely derived from the Canadian Maritime Provinces. A close correlation between HIRM and magnetic foliation suggests that changes in sediment composition (terrigenous vs. marine biogenic) were accompanied by changes in the depositional processes at the site.
Yauk, Kimberly E.
Natural atmospheric dust samples collected from the American southwest and globally were measured using magnetic methods in order to separate remanence attributed to the high coercivity iron oxide and oxyhydroxide minerals hematite and goethite. Dust collected from mountain snow and dust source areas in nearby arid plains were analyzed using traditional room- and low temperature methods. Additional methods were created to better examine the weak, high coercivity components. Combinations of high fields (2.5-9 T), low temperatures (10-300 K), partial AF demagnetization, and thermal demagnetization to 400 K were implemented to separate each component. Percentages of remanence attributed to magnetite, hematite, and goethite were compared to results found by HIRM (hard isothermal remanent magnetization) and Mossbauer spectroscopy with good correlation and to coercivity unmixing methods without correlation. TRM (thermoremanent magnetization) was found to be an important step in magnetizing a greater portion of the goethite fraction. Further procedures for characterizing nano grain sizes would be illuminating.
Klein, Vladislav; Noderer, Keith D.
Aerodynamic equations with unsteady effects were formulated for an aircraft in one-degree-of-freedom, small-amplitude, harmonic motion. These equations were used as a model for aerodynamic parameter estimation from wind tunnel oscillatory data. The estimation algorithm was based on nonlinear least squares and was applied in three examples to the oscillatory data in pitch and roll of 70 deg triangular wing and an X-31 model, and in-sideslip oscillatory data of the High Incidence Research Model 2 (HIRM 2). All three examples indicated that a model using a simple indicial function can explain unsteady effects observed in measured data. The accuracy of the estimated parameters and model verification were strongly influenced by the number of data points with respect to the number of unknown parameters.
Chiverrell, R. C.; Foster, G. F.
The sediment trapping efficiency offered by lakes should allow their sediments to reflect changes in discharge; however studies linking lake records with changing catchment hydrology are rare (e.g. Foster et al., 2003; 2008). Research examining sediments from the last 500 years from Loch of the Lowes (Tweed catchment) reveal variations in sediment properties that have been related to variations in transport capacity (flow regime). Small lakes with moderately sized catchments and limited capacity for upstream sediment storage appear to produce a strong coupling between the catchment and the lake, which appears essential for the system to record a flood stratigraphy. In northwest England and southwest Scotland land-use related woodland clearances have rendered upland landscapes susceptible to erosion. These conditions have produced lake sediment records for the last 4-2000 years dominated by catchment soils and sediments. Careful separation of grain size, geochemical and environmental magnetic parameters can identify suites of signals that reflect variations in both (1) supply and (2) the capacity of the system to transport materials to the lake. The capacity parameters (e.g. sand, HIRM and HIRM/XLF) broadly reflect changes in discharge, can be interpreted in terms of flood frequency. Preliminary data for the Loch of the Lowes basin in the central Southern Uplands of Scotland show a strong correlation with the North Atlantic Oscillation. There the capacity-related lake proxies appear to identify phases of increased flooding ~AD 1625-1650, 1680-1700, 1730-1760, 1800-1815, 1850-1880, 1910-1930, 1960-1970 and possibly the 1990s. Good correspondence between the sediment ‘flood' archive and historical records of flooding in Scotland suggests that lake-catchment systems of this type have the potential to yield valuable information on past hydrological response. These issues are developed in relation to other lakes in northwest England.
Rosenbaum, J.G.; Heil, C.W.
Bear Lake, in northeastern Utah and southern Idaho, lies in a large valley formed by an active half-graben. Bear River, the largest river in the Great Basin, enters Bear Lake Valley ???15 km north of the lake. Two 4-m-long cores provide a lake sediment record extending back ???26 cal k.y. The penetrated section can be divided into a lower unit composed of quartz-rich clastic sediments and an upper unit composed largely of endogenic carbonate. Data from modern fluvial sediments provide the basis for interpreting changes in provenance of detrital material in the lake cores. Sediments from small streams draining elevated topography on the east and west sides of the lake are characterized by abundant dolomite, high magnetic susceptibility (MS) related to eolian magnetite, and low values of hard isothermal remanent magnetization (HIRM, indicative of hematite content). In contrast, sediments from the headwaters of the Bear River in the Uinta Mountains lack carbonate and have high HIRM and low MS. Sediments from lower reaches of the Bear River contain calcite but little dolomite and have low values of MS and HIRM. These contrasts in catchment properties allow interpretation of the following sequence from variations in properties of the lake sediment: (1) ca. 26 cal ka-onset of glaciation; (2) ca. 26-20 cal ka-quasicyclical, millennial-scale variations in the concentrations of hematite-rich glacial fl our derived from the Uinta Mountains, and dolomite- and magnetite-rich material derived from the local Bear Lake catchment (reflecting variations in glacial extent); (3) ca. 20-19 cal ka-maximum content of glacial fl our; (4) ca. 19-17 cal ka-constant content of Bear River sediment but declining content of glacial fl our from the Uinta Mountains; (5) ca. 17-15.5 cal ka-decline in Bear River sediment and increase in content of sediment from the local catchment; and (6) ca. 15.5-14.5 cal ka-increase in content of endogenic calcite at the expense of detrital material. The onset
Reynolds, Richard L.; Cattle, Stephen R.; Moskowitz, Bruce M.; Goldstein, Harland L.; Yauk, Kimberly; Flagg, Cody B.; Berquó, Thelma S.; Kokaly, Raymond F.; Morman, Suzette; Breit, George N.
Iron oxide minerals typically compose only a few weight percent of bulk atmospheric dust but are important for potential roles in forcing climate, affecting cloud properties, influencing rates of snow and ice melt, and fertilizing marine phytoplankton. Dust samples collected from locations across eastern Australia (Lake Cowal, Orange, Hornsby, and Sydney) following the spectacular "Red Dawn" dust storm on 23 September 2009 enabled study of the dust iron oxide assemblage using a combination of magnetic measurements, Mössbauer spectroscopy, reflectance spectroscopy, and scanning electron microscopy. Red Dawn was the worst dust storm to have hit the city of Sydney in more than 60 years, and it also deposited dust into the Tasman Sea and onto snow cover in New Zealand. Magnetization measurements from 20 to 400 K reveal that hematite, goethite, and trace amounts of magnetite are present in all samples. Magnetite concentrations (as much as 0.29 wt%) were much higher in eastern, urban sites than in western, agricultural sites in central New South Wales (0.01 wt%), strongly suggesting addition of magnetite from local urban sources. Variable temperature Mössbauer spectroscopy (300 and 4.2 K) indicates that goethite and hematite compose approximately 25-45% of the Fe-bearing phases in samples from the inland sites of Orange and Lake Cowal. Hematite was observed at both temperatures but goethite only at 4.2 K, thereby revealing the presence of nanogoethite (less than about 20 nm). Similarly, hematite particulate matter is very small (some of it d < 100 nm) on the basis of magnetic results and Mössbauer spectra. The degree to which ferric oxide in these samples might absorb solar radiation is estimated by comparing reflectance values with a magnetic parameter (hard isothermal remanent magnetization, HIRM) for ferric oxide abundance. Average visible reflectance and HIRM are correlated as a group (r2 = 0.24), indicating that Red Dawn ferric oxides have capacity to absorb
The mathematical models needed to represent the various dynamics phenomena have been conceived in many disciplines related to aerospace engineering. Major aerospace companies have developed their own codes to estimate aerodynamic characteristics and aircraft stability in the conceptual phase, in parallel with universities that have developed various codes for educational and research purposes. This paper presents a design tool that includes FDerivatives code, the new weight functions method and the continuity algorithm. FDerivatives code, developed at the LARCASE laboratory, is dedicated to the analytical and numerical calculations of the aerodynamic coefficients and their corresponding stability derivatives in the subsonic regime. It was developed as part of two research projects. The first project was initiated by CAE Inc. and the Consortium for Research and Innovation in Aerospace in Quebec (CRIAQ), and the second project was funded by NATO in the framework of the NATO RTO AVT-161 "Assessment of Stability and Control Prediction Methods for NATO Air and Sea Vehicles" program. Presagis gave the "Best Simulation Award" to the LARCASE laboratory for FDerivatives and data FLSIM applications. The new method, called the weight functions method, was used as an extension of the former project. Stability analysis of three different aircraft configurations was performed with the weight functions method and validated for longitudinal and lateral motions with the root locus method. The model, tested with the continuity algorithm, is the High Incidence Research Aircraft Model (HIRM) developed by the Swedish Defense Research Agency and implemented in the Aero-Data Model In Research Environment (ADMIRE).
Dong, Yan; Zhang, Weiguo; Dong, Chenyin; Ge, Can; Yu, Lizhong
In this paper, we present the results of research on a coastal lowland Holocene tidal flat sequence in order to explore the variations in magnetic mineralogy during the process of tidal flat sedimentation and subsequent land formation. Three cores (˜6 m in length) were collected from the coastal plain in Jiangsu Province, China, and investigated with magnetic measurements, diffuse reflectance spectroscopy (DRS) and free iron oxide (Fed) analyses. The tidal flat sequence shows a fining-upward trend, and the top ˜2 m of each core with redoximorphic feature was interpreted to be a salt marsh facies in origin. Unmixing of isothermal remanent magnetization acquisition curves identify magnetite and maghemite as well as high-coercivity hematite and goethite, with the latter iron oxides confirmed by DRS analysis. Enrichment of goethite, hematite and maghemite occurs in the salt marsh deposits in comparison to the lower intertidal and subtidal deposits, with goethite being the dominant iron oxide. The changes in hard isothermal remanent magnetization acquired in field above 100 mT field (HIRM100) and the S-100 ratio largely reflect the presence of medium-coercivity maghemite in absolute content and relative proportions, respectively. The approach used for iron oxide characterization may offer an efficient diagnostic tool for recognizing sediments or soils subjected to redox condition oscillation elsewhere and contribute to studies of iron cycling in (palaeo-)environmental researches.
Baker, Dahlia Anne; Wollack, Edward; Rostem, Karwan
Control over optical response is an important aspect of instrument design for astrophysical imaging. Here we consider a mid-infrared absorber coating proposed for use on HIRMES (High Resolution Mid-Infrared Spectrometer), a cryogenic spectrometer which will fly on the SOFIA (Stratospheric Observatory for Infrared Astronomy) aircraft. The aim of this effort is to develop an absorptive coating for the 20-200 microns spectral range based on a graphene loaded epoxy binder (Epotek 377H) and glass microsphere scatterers (3M K1). The coatings electromagnetic response was modeled using a Matlab script and the glass microspheres were characterized by the measured size distribution, the dielectric constant, and the filling fraction. Images of the microspheres taken by a microscope were used to determine the size distribution with an ImageJ particle analysis program. Representative test samples for optical evaluation were fabricated for characterization via infrared Fourier transform spectroscopy. The optical tests will determine the material’s absorptance and reflectance. These test results will be compared to the modeled response.
Srivastava, Priyeshu; Sangode, S. J.; Parmar, Nikita; Meshram, D. C.; Jadhav, Priyanka; Singhvi, A. K.
The voluminous red sand deposits of Bheemuni in the east coast of India provide record of coastal land-sea interaction during the late Quaternary climatic and eustatic oscillations. Limited information on the origin and depositional environments of these red sands and their chronology is available. We studied two inland to coast cross profiles from Bheemuni red sand deposits using mineral magnetism, color characteristics and Citrate-bicarbonate-dithionite (CBD) extractable pedogenic iron oxides over 23 horizons along with optically stimulated luminescence (OSL) chronology at 6 horizons. The oldest exposed bed had an optical age of 48.9 ± 1.7 ka. Differential ages between the two parallel sections (SOS = 48.9 ± 1.7 to 12.1 ± 0.3 ka and IMD = 29.3 ± 3.5 ka) suggest laterally shifting fluvial sedimentation. Both the profiles show significant amount of antiferromagnetic oxide (hematite) along with ferrimagnetic (magnetite/maghemite) mineral composition. The granulometric (/domain-) sensitive parameters (χFD, χARM, SIRM/χLF and χARM/χLF) indicate variable concentration of superparamagnetic (SP) and single domain (SD) particles between the two profiles. The higher frequency dependent and pedogenic magnetic susceptibilities (χFD and χpedo) in the younger (IMD) profile suggest enhanced pedogenesis under a warm-wet climate post 29.3 ka and also during Holocene. A combination of hard isothermal remanent magnetization (HIRM) and redness rating (RR) index indicates distinct but variable concentration of a) crystalline and b) poorly crystalline (pigmentary) hematites in both the profiles. We consider that the former (#a) is derived from hinterland red soils and possibly due to post-depositional diagenesis, and the latter (#b) precipitated from the dissolved iron under fluvial regime imparting the unique red coloration to Bheemuni sands. Partial to complete alteration of ferromagnesian minerals due to pedogenesis in hinterlands under warm-wet climate was therefore the
Kawamura, N.; Amano, Y.; Ishikawa, N.
Frequent outbreaks of red tide caused by dinoflagellate blooms have been reported since 1970 in the Hiroshima bay. Iron is an essential element for dinoflagellates, and is supplied as bivalent or trivalent ions and iron compounds from lands to sea. For damage predictions of red tide, it is important to research the distribution of iron in the bay. In order to investigate the distribution and mode of iron in sediments, suspended solids (SS), and bottom water in the Hiroshima Bay, rock magnetic and geochemical analyses are performed. Sediments of 5 cm in depth and overlying bottom water were taken at three sites in the bay every month. The sediment samples were composed of clayey silt. We measured dissolved iron concentration in bottom waters filtered above 0.45 um grains. The contents of carbon, nitrogen, and sulfur in the sediments are measured. The rock magnetic measurements (magnetic susceptibility, NRM, ARM, IRM, HIRM, S-0.3T, magnetic hysteresis, and high temperature magnetometry) of the sediments and SS are conducted. Concentration dependent rock magnetic parameters of the sediments and SS show relatively high values during spring at the near estuary site. It indicates that relatively larger amount of terrigenous materials are supplied in this season. Magnetic grain size decreases during summer, while iron concentration increases in the bottom waters. Data of oceanographic observations at these sites showed that the temperature of the bottom water increased, whereas DO and pH values decreased during summer. The presence of magnetite (Fe3O4) and hematite (Fe2O3) were recognized in all analyzed samples, whereas greigite (Fe3S4) appeared during summer. The contents of sulfur in the sediments also increase in this period. It is implied that magnetite and hematite were dissolved, and greigite was formed associated with the proceeding of the anoxic condition during summer. It is suggested that irons moves between sediments and bottom water corresponding to seasonal
Quinton, Emily E.; Dahms, Dennis E.; Geiss, Christoph E.
In order to constrain the rate of magnetic enhancement in soils, we investigated modern soils from five fluvial terraces in the eastern Wind River Range, Wyoming. Profiles up to 1.2 m deep were sampled in 5-cm intervals from hand-dug pits or natural riverbank exposures. Soils formed in fluvial terraces correlated to the Sacajawea Ridge (730-610 ka BP), Bull Lake (130-100 ka BP) and Pinedale-age (˜20 ka BP) glacial advances. One soil profile formed in Holocene-age sediment. Abundance, mineralogy, and grain size of magnetic minerals were estimated through magnetic measurements. Magnetic enhancement of the A-horizon as well as an increase in fine-grained magnetic minerals occurred mostly in Bull Lake profiles but was absent from the older profile. Such low rates of magnetic enhancement may limit the temporal resolution of paleosol-based paleoclimate reconstructions in semiarid regions even where high sedimentation rates result in multiple paleosols. A loss of ferrimagnetic and an increase in antiferromagnetic minerals occurred with age. Our findings suggest either the conversion of ferrimagnetic minerals to weakly magnetic hematite with progressing soil age, or the presence of ferrimagnetic minerals as an intermediate product of pedogenesis. Absolute and relative hematite abundance increase with age, making both useful proxies for soil age and the dating of regional glacial deposits. All coercivity proxies are consistent with each other, which suggests that observed changes in HIRM and S-ratio are representative of real changes in hematite abundance rather than shifts in coercivity distributions, even though the modified L-ratio varies widely.
Leng, Wei; von Dobeneck, Tilo
Large-scale glacial meltwater discharge could be widely recognized off the eastern Canadian continental margin. At Laurentian Fan, sub-glacial outburst floods eroded Permian-Carboniferous redbeds at Gulf of St. Lawrence and then delivered the reddish sediments by Laurentian Channel. Sedimentary record from four gravity cores (GeoB18514-2, 18515-1, 18516-2 and 18517-1) at the SW slope of the Grand Banks of Newfoundland revealed the major depositional processes since Heinrich event 2 (ca. 22 ka). In the cores, the upper thick Holocene olive-grey silty mud units overly IRD-rich Heinrich 1 layer, five reddish units are distinguished in the lower part. Reddish units get proportionally thinner along the SW slope at higher and more distal positions; instead, separating olive-grey layers get thicker with height and distance. Reddish and olive grey units have sharp boundaries and no signs of erosion. Mean grain size changes abruptly from coarse in grey layers to fine in reddish layers, terrigenous elements (as Al, K, Ti, Fe) and clays (Al/Si) are highly elevated in reddish layers and low in Heinrich layers, which are instead enriched in detrital continental carbonates. Both Heinrich layers and reddish layers have enhanced magnetic susceptibility, but Heinrich layer have higher ferromagnetic (SIRM) content (mafic rocks), while reddish layers have more hematite (HIRM). These five reddish layers differ from event to event, which seems to reflect different mixing ratios of event-related and background sedimentation. This mixing will allow estimating event-specific sedimentation rates. Using mixing ratio combined with 14C dating data could contribute to estimate the sedimentation rate and duration of outburst floods, which could help to build ice sheet retreat history and find the connection with paleoclimate changes.
Reynolds, Richard L.; Goldstein, Harland L.; Moskowitz, Bruce M.; Bryant, Ann C.; Skiles, S. McKenzie; Kokaly, Raymond F.; Flagg, Cody B.; Yauk, Kimberly; Berquó, Thelma; Breit, George; Ketterer, Michael; Fernandez, Daniel; Miller, Mark E.; Painter, Thomas H.
Dust layers deposited to snow cover of the Wasatch Range (northern Utah) in 2009 and 2010 provide rare samples to determine the relations between their compositions and radiative properties. These studies are required to comprehend and model how such dust-on-snow (DOS) layers affect rates of snow melt through changes in the albedo of snow surfaces. We evaluated several constituents as potential contributors to the absorption of solar radiation indicated by values of absolute reflectance determined from bi-conical reflectance spectroscopy. Ferric oxide minerals and carbonaceous matter appear to be the primary influences on lowering snow-cover albedo. Techniques of reflectance and Mössbauer spectroscopy as well as rock magnetism provide information about the types, amounts, and grain sizes of ferric oxide minerals. Relatively high amounts of ferric oxide, indicated by hard isothermal remanent magnetization (HIRM), are associated with relatively low average reflectance (<0.25) across the visible wavelengths of the electromagnetic spectrum. Mössbauer spectroscopy indicates roughly equal amounts of hematite and goethite, representing about 35% of the total Fe-bearing phases. Nevertheless, goethite (α-FeOOH) is the dominant ferric oxide found by reflectance spectroscopy and thus appears to be the main iron oxide control on absorption of solar radiation. At least some goethite occurs as nano-phase grain coatings less than about 50 nm thick. Relatively high amounts of organic carbon, indicating as much as about 10% organic matter, are also associated with lower reflectance values. The organic matter, although not fully characterized by type, correlates strongly with metals (e.g., Cu, Pb, As, Cd, Mo, Zn) derived from distal urban and industrial settings, probably including mining and smelting sites. This relation suggests anthropogenic sources for at least some of the carbonaceous matter, such as emissions from transportation and industrial activities. The composition of
Warrier, Anish Kumar; Shankar, R.; Manjunatha, B. R.; Harshavardhana, B. G.
We have used rock magnetic techniques in this study to assess atmospheric pollution at five stations in and around Mangalore city on the southwestern coast of India. Samples of dust were collected from two suburban areas (Thokkottu and Pumpwell located respectively ~ 10 km and 3 km from the city center), the city center itself (Milagres) and industrial/port areas (Panambur and Mangalore Refinery and Petrochemicals Limited (MRPL)). Low-frequency magnetic susceptibility (χlf), frequency-dependent susceptibility (χfd), susceptibility of anhysteretic remanent magnetization (χARM) and isothermal remanent magnetization (IRM 20 to 1000 mT) were determined on 23 dust samples and inter-parametric ratios calculated. Results show that samples from suburban areas (particularly Thokkottu) are characterized by low χlf (< 314.1 × 10- 8 m3 kg- 1) and up to 6% χfd, suggesting low levels of pollution and the presence of pedogenic magnetite possibly derived from soils by wind erosion. However, the average χlf of Milagres, Panambur and MRPL dust samples is high by factors of 9.2, 3.3 and 2.6 compared to that of the Thokkottu sample. The Milagres sample contains magnetically "soft" minerals like magnetite, possibly indicating its derivation from motor vehicle exhaust. In contrast, the Panambur dust sample is characterized by magnetically "hard" minerals such as hematite and goethite as it has an 8-fold higher HIRM value compared to the Thokkottu sample. This magnetic signature is perhaps the result of dust particles derived from the grinding of hematite-rich iron ore by the Kudremukh Iron Ore Company Limited (KIOCL) at Panambur and its storage and export through the nearby New Mangalore Port. However, the dust sample from MRPL has magnetically "soft" minerals like magnetite. This magnetic mineral may have originated from petroleum refining processes at MRPL. Particulate pollution from industrial activities and motor vehicle exhaust is a threat to human health and is known to
Reynolds, R. L.; Goldstein, H.; Painter, T.; Moskowitz, B. M.; Yauk, K.; Flagg, C.; Kokaly, R. F.; Miller, M. E.; Ketterer, M. E.
Dust layers deposited on snow cover of the Wasatch Range (northern Utah) in 2009 and 2010 provide rare samples to determine the relations between their compositions and radiative properties. These studies are required to comprehend and model how such dust-on-snow (DOS) layers affect rates of snow melt through changes in the albedo of snow surfaces. We evaluated several constituents as potential contributors to the absorption of solar radiation indicated by values of absolute reflectance determined from bi-directional reflectance spectroscopy. Ferric oxide minerals and organic matter appear to be the primary influences on lowering snow-cover albedo. Techniques of reflectance and Mössbauer spectroscopy as well as rock magnetism provide information about the types, amounts, and grain sizes of ferric oxide minerals. Relatively high amounts of ferric oxide, indicated by hard isothermal remanent magnetization (HIRM), are associated with relatively low average reflectance (0.1702-0.3160) within the visible part of the solar radiation spectrum. Mössbauer spectroscopy indicates roughly equal amounts of hematite and goethite, representing about 35% of the total Fe-bearing phases. Nevertheless, goethite (FeOOH) is the dominant ferric oxide found by reflectance spectroscopy and thus appears to be the main iron oxide control on absorption of solar energy. At least some goethite probably occurs as nano-phase grain coatings less than about 50 nm thick. Relatively high amounts of organic carbon, indicating as much as 9 % organic matter, are also associated with lower reflectance values. The organic matter correlates strongly with metals (e.g., Cu, Pb, As, Cd, Mo, Zn) derived from far-distant urban and industrial settings (including mining and smelting sites). This relation suggests anthropogenic sources for at least some of the organic matter, such as emissions from transportation and industrial activities. The composition of the DOS samples can be compared with sediments in a
Kars, M. A. C.; Musgrave, R. J.; Kodama, K.; Jonas, A. S.
In 2014, IODP Expedition 350 drilled a 1806.5 m deep hole at Site U1437 in the Izu Bonin rear arc. The Site presents an unusual deep methanogenesis zone because of a release of sulfate below the sulfate reduction zone (27-83 mbsf) which may buffer methanogenesis by anaerobic methanogens. Methane abundance gradually increases with depth, with significant abundance at ~750-1459 mbsf with a maximum value at 920 mbsf. The rock magnetic study carried out in Hole U1437D from ~775 to ~1000 mbsf shows a drastic change of the magnetic properties at ~850 mbsf coincidently with a stronger release of methane from < 60 ppm at 841 mbsf to ~300 ppm at 854 mbsf. That also corresponds to a depth interval where no core was recovered (~846-854 mbsf). For the sake of clarity, we call hereafter zone A the depth interval above this non-recovered interval (775-846 mbsf) and zone B the interval below (854-1000 mbsf). Both belong to the same lithostratigraphic unit composed of tuffaceous mudstones intercalated with volcanoclastics. In the zone A, NRM, magnetic susceptibility, ARM, SIRM, HIRM display high values. In the zone B, these parameters show much lower values of one order of magnitude less, except for the interval 936-950 mbsf that corresponds to a local maximum (but still lower values than the zone A). Besides, the rock magnetic parameters for grain size and coercivity, such as ARM/χ, S-ratio and Bcr do not show any variations throughout the entire studied interval, although S-ratio displays slightly lower values from ~850 to ~930 mbsf. Grains are low coercivity pseudo-single domain sized. According to the present data, two preliminary hypotheses can be proposed to explain the observations. 1) The non-recovered interval between the zones A and B can be caused by the presence of a sedimentary hiatus and/or a fault, which may be consistent with the observed change in sedimentation rate. 2) No hiatus in the sedimentation. The changes in the magnetic properties can be explained by a
van Peer, Tim; Xuan, Chuang; Lippert, Peter; Wilson, Paul; Liebrand, Diederik
(possibly of biogenic origin) and a coarse-grained non-stoichiometric haematite component as remanence carriers of the sediments. Variations in the magnetic particle concentration, inferred from bulk magnetic susceptibility (χ), qualitatively co-vary with a global stacked oxygen-isotope curve on at least an ~100 kyr scale. The ratios between χ and anhysteretic remanent magnetisation (ARM) and ARM/IRM are typically used to assess bulk magnetite grain size. These ratios, as well as the HIRM ('hard' IRM) component (haematite/goethite) and the L-ratio, decrease approximately by a factor of 2 at the onset of the Mi1 event in Subchron C6Cn.3n. All of these environmental magnetic changes are coincident with an abrupt increase in the Zr/Ti values - a proxy for detrital input, measured by continuous X-Ray Fluorescence core scanning. Collectively, these observations are consistent with shifts in supply or preservation of the non-stoichiometric haematite component throughout the measured section. We tentatively interpret these changes in deep sea magnetic mineralogy to reflect changes in sediment provenance, grain size, or both, which are likely related to changes in DWBC strength and source regions; this hypothesis can be tested by additional magnetic fabric, sediment particle, and geochemical studies. Our work demonstrates that continuous magnetic measurements can reveal important changes in contourite drifts, and hints at how major climatic events such as Mi1 may influence ocean current systems such as the DWBC.