Microplastic pollution in surface water and sediments of Qinghai-Tibet Plateau: Current status and causes

To study the current status and causes of the microplastic pollution in surface water of the Qinghai-Tibet Plateau, this paper compared the average microplastic abundance in sediments and surface water of the Qinghai-Tibet Plateau and the results are as follows. First, the average microplastic abundance in surface water of the independent rivers and the whole area is 247–2686 items/m³ and 856 items/m³, respectively. The average microplastic abundance in sediments of independent rivers or lakes and the whole area is 0–933 items/m² and 362 items/m², respectively. Meanwhile, the degree of microplastic pollution in river sediments is higher than that in lake sediments, and the rivers suffering from microplastic pollution mainly include the Brahmaputra River, Tongtian River, and Nujiang River. Second, compared with the microplastic pollution in other areas of the world, the levelof microplastic pollution in the lakes and rivers of the Qinghai-Tibet plateau is not lower than that of well-developed areas with more intensive human activities. Finally, this study suggests that relevant government departments of the Qinghai-Tibet Plateau should strengthen waste management strategies while developing tourism and that much attention should be paid to the impacts of microplastics in the water environment.©2021 China Geology Editorial Office.     

Strain rate of the South American lithospheric plate by SIRGAS-CON geodetic observations

A multiyear solution of the SIRGAS-CON network was used to estimate the strain rates of the earth surface from the changing directions of the velocity vectors of 140 geodetic points located in the South American plate. The strain rate was determined by the finite element method using Delaunay triangulation points that formed sub-networks; each sub-network was considered a solid and homogeneous body. The results showed that strain rates vary along the South American plate and are more significant on the western portion of the plate, as expected, since this region is close to the subduction zone of the Nazca plate beneath the South American plate. After using Euler vectors to infer Nazca plate movement and to orient the velocity vectors of the South American plate, it was possible to estimate the convergence and accommodation rates of the Nazca and South American plates, respectively. Strain rate estimates permitted determination of predominant contraction and/or extension regions and to establish that contraction regions coincide with locations with most of the high magnitude seismic events. Some areas with extension and contraction strains were found to the east within the stable South American plate, which may result from different stresses associated with different geological characteristics. These results suggest that major movements detected on the surface near the Nazca plate occur in regions with more heterogeneous geological structures and multiple rupture events. Most seismic events in the South American plate are concentrated in areas with predominant contraction strain rates oriented northeast-southwest; significant amounts of elastic strain can be accumulated on geological structures away from the plate boundary faults; and, behavior of contractions and extensions is similar to what has been found in seismological studies.     

Twenty-five years of spectral UV-B measurements over Canada,Europe and Japan: Trends and effects from changes in ozone,aerosols, clouds,and surface reflectivity

Spectral UV records of solar irradiance at stations over Europe, Canada, and Japan were used to study long-term trends at 307.5 nm for a 25-year period, from 1992 to 2016. Ground-based measurements of total ozone, as well as satellite measurements of the Aerosol Index, the Total Cloud Cover and the surface reflectivity were also used in order to attribute the estimated changes of the UV to the corresponding changes of these factors. The present study shows that over the Northern Hemisphere, the long-term changes in UV-B radiation reaching the Earth's surface vary significantly over different locations, and that the main drivers of these variations are changes in aerosols and total ozone. At high latitudes, part of the observed changes may also be attributed to changes in the surface reflectivity. Over Japan, the UV-B irradiance at 307.5 nm has increased significantly by ∼3%/decade during the past 25 years, possibly due to the corresponding significant decrease of its absorption by aerosols. It was found that the greatest part of this increase took place before the mid-2000s. The only European station, over which UV radiation increases significantly, is that of Thessaloniki, Greece. Analysis of the clear-sky irradiance for the particular station shows increasing irradiance at 307.5 nm by ∼3.5%/decade during the entire period of study, with an increasing rate of change during the last decade, possibly again due to the decreasing absorption by aerosols.     

大孔隙与大孔隙率矿石的石蜡法体重测定中的修正问题

以伽玛测井解释含量确定铀矿储量时，矿石体重应该是天然状态下的体重，当矿心孔隙度较大而有部分失水，并存在表面大孔隙时，封蜡法所测得的体重系统偏小。对此，本文改进了测定方法，提出了修正方案，并以某矿床为例分析了产生表面孔隙的原因及修正后的具体结果。     

Lithospheric structure beneath the East China Sea revealed by Rayleigh-wave phase velocities

We explore the variations of Rayleigh-wave phase-velocity beneath the East China Sea in a broad period range (5–200 s). Rayleigh-wave dispersion curves are measured by the two-station technique for a total of 373 interstation paths using vertical-component broad-band waveforms at 32 seismic stations around the East China Sea from 6891 global earthquakes.The resulting maps of Rayleigh-wave phase velocity and azimuthal anisotropy provide a high resolution model of the lithospheric mantle beneath the East China Sea. The model exhibits four regions with different isotropic and anisotropic patterns: the Bohai Sea, belonging to the North China Craton, displays a continental signature with fast velocities at short periods; the Yellow Sea, very stable unit associated with low deformation, exhibits fast velocities and limited anisotropy; the southern part of the East China Sea, with high deformation and many fractures and faults, is related to slow velocities and high anisotropic signature; and the Ryukyu Trench shows high-velocity perturbations and slab parallel anisotropy.     

A non-glacial origin for the ordovician (middle caradocian) cosquer formation,veryarc'h,crozon peninsula,brittany, France

The presence of a dispersed clast fraction in strata near the base of the Cosquer Formation in west Brittany, does not support a glacial origin for this unit. The upper 25 to 30 m of the underlying Kermeur Formation consists of a prograding sequence of very fine to fine sandstones deposited in a mid to distal current swept shelf setting. This sequence shows signs of slope instability, as do the supposed ‘glacial strata’ which overlie it. The upper two thirds of the Cosquer Formation contain spectacular slump-breccias. Smaller clasts within the laminated mudrocks at the base of the formation are associated with thin graded and non-graded sandstone laminae. They show no evidence of active penetration into underlying laminae other than can be explained by compaction. Larger clasts are confined to thicker massive beds, or disrupted units with marked internal contorted lamination. This, along with the abundance of slump features within the sequence suggests lateral emplacement by sediment gravity flows in a distal shelf-slope setting. Surface textures of sand grains within the formation are related to rock disaggregation along fractures developed during post-depositional deformation and are not related to glacial processes. Distinctive mineralogically immature, poorly-sorted aggregate sediment pellets, which have been considered as positive proof of glaciation, are not present.     

Application of the normalized surface magnetic charge model to UXO discrimination in cases with overlapping signals

This paper presents an application of the normalized surface magnetic charge (NSMC) model to discriminate objects of interest, such as unexploded ordnance (UXO), from innocuous items in cases when UXO electromagnetic induction (EMI) responses are contaminated by signals from other objects. Over the entire EMI spectrum considered here (tens of Hertz up to several hundreds of kHz), the scattered magnetic field outside the object can be produced mathematically by equivalent magnetic charges. The amplitudes of these charges are determined from measurement data and normalized by the excitation field. The model takes into account the scatterer's heterogeneity and near- and far-field effects. For classification algorithms, the frequency spectrum of the total NSMC is proposed and investigated as a discriminant. The NSMC is combined with the differential evolution (DE) algorithm in a two-step inversion procedure. To illustrate the applicability of the DE–NSMC algorithm, blind test data are processed and analyzed for cases in which signals from nearby objects frequently overlap. The method was highly successful in distinguishing UXO from accompanying clutter.     

Surface wave propagation in a transversely isotropic elastic layer overlying a liquid saturated porous solid half-space and lying under the uniform layer of liquid

Dispersion of Rayleigh-type surface wave is studied in a homogeneous transversely isotropic elastic layer overlying a nondissipative liquid-saturated porous solid half-space and lying under a uniform layer of homogeneous liquid. The frequency equation in the form of ninth-order determinant is obtained.Special cases have been deduced by reducing the depth of the layers to zero and by changing the transverse isotropic layer to an isotropic layer. Dispersion curves for the phase velocity have been plotted for a particular model.     

A study of a fair weather boundary layer in TOGA-COARE: Parameterization of surface fluxes in large scale and regional models for light wind conditions

The study focuses on a way to parameterize the effect of subgrid scale convective motions on surface fluxes in large scale and regional models for the case of light surface winds. As previously proposed, these subgrid effects are assumed to scale with the convection intensity through the relationship: where is the mean velocity of the wind, U₀ the velocity of the mean wind, w_* the free convection velocity, and an empirical coefficient to be determined. Both observations and numerical simulation are presently used to determine the free convection coefficient .Large eddy simulation of a fair weather convective boundary layer case observed during TOGA-COARE is performed. Comparisons between observations and the simulation of surface properties and vertical profiles in the planetary boundary layer are presented. The simulated vertical turbulent fluxes of heat, moisture and buoyancy range well within estimates from aircraft measurements.The most important result is that the true free convection coefficient , directly estimated from simulation, leads to a value of 0.65, smaller than the ones estimated from temporal and spatial variances. Using observations and simulation, estimates of from temporal and spatial variances are obtained with similar values 0.8. From both theoretical derivations and numerical computations, it is shown that estimates of the true from variances are possible but only after applying a correction factor equal to 0.8. If this correction is not used, is overestimated by about 25%. The time and space sampling problem is also addressed in using numerical simulations.     

Feedbacks in the Land-Surface and Mixed-Layer Energy Budgets

A mixed-layer model of the surface energy budget and the planetary boundary layer (PBL) is developed, based on the prognostic equations for soil temperature, mixed layer potential temperature and specific humidity and the growth and abrupt collapse of the PBL. Detailed parameterizations of the longwave radiative fluxes are included. The feedbacks in the uncoupled (i.e. surface energy budget with non-responding PBL) and coupled land surface and atmospheric mixed-layer energy budgets are examined. A simplified, time continuous, version of the model, in which the specific humidity budget is the balance of evapotranspiration and dry-air entrainment, and the PBL height is given by the lifted condensation level, is shown to be in good agreement with the complete model. By forcing the simplified model with daily mean rather than periodic solar radiation, an equilibrium model state is achieved where the fluxes are in close agreement with the daily mean fluxes corresponding to the periodic forcing. The model also agrees favorably with measurements from the FIFE field experiment. Feedbacks are examined using the equilibrium model state. The uncoupled and coupled model sensitivities with respect to the minimal stomatal resistance and the atmospheric specific humidity not only differ in magnitude, but in sign as well. This results puts into question the extent to which uncoupled land-surface models that are forced with atmospheric variables may be used in sensitivity studies.