Reactive oxygen species (ROS) production in O2-perturbed subsurface environments has been increasingly documented in recent years. However, the constraining conditions under which abiotic and/or biotic mechanisms predominate for ROS production remain ambiguous. Here, we demonstrate that the ROS production mechanism, biotic and abiotic, is determined by sediment redox properties and sediment compositions. Upon the oxygenation of 10 field sediments, the cumulative H2O2 concentrations reached up to 554 μmol/kg within 2 h. The autoclaving sterilization experiments showed that H2O2 could be produced by both biotic and abiotic processes depending on the redox conditions. However, only the abiotic process could produce significant levels of •OH, and the production yield was closely related to the sediment components, particularly sediment Fe(II) and organic matter. Fe(II) bound with organic matter led to high yields of H2O2 and •OH production. Sediment oxygenation contributed to the appearance of H2O2 in groundwater, with the abiotic mechanism producing higher instantaneous H2O2 concentrations than the biotic mechanism. These findings reveal that the redox conditions, compositions, and texture of sediments collectively control abiotic and biotic mechanisms for ROS production, which assists the identification of ROS production hotspots and the understanding of ROS distribution and utilization in the subsurface.
In this paper, techniques for retrieving wind direction and speed from shipborne X-band nautical radar images are presented. First, by analyzing the radar backscatter intensity histogram and zero-pixel percentage, each individual image is designed to go through a data quality control process. With this processing, the rain cases and all-black images can be recognized. Then, a harmonic function that is least-squares fitted to the radar backscatter intensity as a function of antenna look direction is applied to determine the wind direction. Furthermore, for wind speed retrieval, an empirical third-order polynomial model is derived using the average radar backscatter intensity and the reference wind speed. To improve the accuracy of wind retrieval, a modified technique, which involves a dual-curve-fitting approach, is implemented. For the data presented in this paper, it was found that the second stage of the curve-fitting performed optimally when the data at angles of 60° to the left and right of the first-guess upwind direction were used. Also, only the data for the dual-curve-fitting were used to calculate the average intensity of the radar images for wind speed estimation. The modified method is applied to the radar data and the results are compared with the reference data measured by a ship-based anemometer. It is shown that the dual-curve-fitting algorithm produces improvements in the mean differences between the radar and the anemometer results for wind direction and speed of about 7° and 0.4 m/s, respectively, under low sea state.
Seismic tomography using body or surface wave data is a powerful tool to explore the structure of Earth’s interior structure. In recent decades, joint inversion of seismic body and surface wave data has been widely employed to investigate seismic velocities of the Earth’s lithosphere and asthenosphere. Benefited from the complementary sensitivities of different datasets, seismic velocities determined by joint inversion generally exhibit higher resolution and accuracy. Regular mesh (cell or grid) is commonly used in seismic tomography. As data distribution is uneven in most cases, regularization techniques are implemented in regular mesh seismic tomography method to stabilize ill-posed problems. Despite the selection of appropriate regularization parameters, it is also challenging to achieve multiscale resolution in regular mesh joint inversion method. In this study, we developed a joint inversion method using adaptive irregular mesh according to the real data distribution based on Poisson-Voronoi cells. Synthetic tests show that the newly developed method can better resolve multi-scale structures without regularizations. We applied this method to a dataset with seismic arrays in different scales. The newly determined multiscale velocity model reveals distinct features particularly in areas with dense data distribution.
With development and continuous improvement of methods and technologies, more and more attention has been paid to research of marine controllable source electromagnetic inversion. How to develop a fast and practical marine controllable source electromagnetic inversion method is one of the current research focuses and hot spots. So it is necessary for the development of marine controllable source electromagnetic to study the 2D fast, reasonable and effective inversion, which has important theoretical and practical significance. In this paper, the traditional Gauss-Newton inversion is carried out on the basis of the adaptive finite element forward simulation, and the simulation data and the Occam inversion results are systematically analyzed and compared. The classical model inversion results show that both Occam inversion and Gauss-Newton inversion can invert the anomalies well and the inversion results have their own advantages and disadvantages. Occam inversion RMS is low, the result is smoother, the convergence is stable; the Gauss-Newton inversion time is short, and the number of iterations is small. This is helpful for the later marine controllable source electromagnetic method data interpretation and application.
We report the petrology, whole-rock geochemistry, zircon LA-ICP-MS U-Pb chronology and zircon Hf isotopic data of Daxigou granitoids (western part of the Kuluketage Block, NW China) to evaluate their likely petrogenesis and tectonic setting.Zircons from syenogranite can be divided into two groups: 1) those that display oscillatory zoning and high Th/U ratios (average = 1.38), implying their magmatic origin and 2) those that exhibit weak zoning and extremely high U and Pb contents but low Th/U ratios (average = 0.35), resembling zircons that experienced hydrothermal alteration.The zircon LA-ICP-MS U-Pb dating of the two groups of zircons yielded weighted mean ages of 1830 ± 12 Ma (MSWD = 0.78) and 1798 ± 21 Ma (MSWD = 1.6) respectively.The Daxigou granitoids belong mostly to normal-K and sodium-rich metaluminous calc-alkaline type, systematically enriched in LREE and large ion lithophile elements (LILE, e.g., K, Ba and Rb), but significantly depleted in high field strength elements (HFSE, e.g., Ti, P, Nb, Ta and U).Their εHf(t) values and two-stage Hf model ages range from -7.16 to -5.03 and 2.69 to 2.76 Ga, respectively.Taken together, it is suggested that Daxigou granitoids are of I-type affinity and that they were derived by partial melting of a Neoarchaean TTG (e.g., Tuoge Complex) rocks in a continental-arc environment.These new data, combined with previous regional geological studies, demonstrate that a series of Palaeoproterozoic (c.2.0-1.8Ga) tectono-magmatic events occurred in Kuluketage Block during the assembly of Columbia.
An abnormal multipath arrival structure was found in the signal from a receiver array during an acoustic experiment in East China Sea. The cause for the abnormal pattern was found due to the tilt of the array, which results from the strong sea currents. The array tilt was figured out with the Bellhop acoustic ray model by matching the simulation results with the received signal. Results were further testified by the depth sensor data. Given that the ocean observations are always sparse in time and spatial domain, the method in this paper provides a new source to help determine the sea current direction in the complex shallow water environment.
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