A detailed chronology of the sedimentation in the Danube abyssal fan records the major episodes of the late-Holocene Black Sea evolution

We have constructed a high-resolution Bayesian sedimentation model spanning the last 5500 years based on 25 AMS radiocarbon dated sediments of bulk organic matter (OM) sampled from the NW Black Sea anoxic waters of the continental slope. The corrections for the ¹⁴C ages due to marine reservoir effect (MRE) and detritus organic carbon are correlated with exogenous information such as ²¹⁰Pb dating, metallurgy pollution and human-induced soil erosion, highlighting the Danube influence on the geochemistry and chronology of the NW Black Sea sediments through the input of terrigenous organic matter. The results show excellent agreement with some of the previous studies, supporting a total age offset for the bulk OM of 60 years as MRE and 580 years as detritus organic carbon influence. The revisited chronology pinpoints the first and second invasion of the coccolithophores Emiliania huxleyi at 2524 ± 87 and 625 ± 65 years cal. BP. Sedimentation rate shows an increase of about three times with the starting of the late Medieval, which correspond to the highest observed sediment discharge of the Danube as are considered the last 500-300 years. This type of high-resolution sedimentation model is an important step for constructing the carbon budget in bottom waters of variable oxygen concentration.     

Magnetic-Tower Jet Solution for Launching Astrophysical Jets

In spite of the large number of global three-dimensional (3-D) magnetohydrodynamic (MHD) simulations of accretion disks and astrophysical jets, which have been developed since 2000, the launching mechanisms of jets is somewhat controversial. Previous studies of jets have concentrated on the effect of the large-scale magnetic fields permeating accretion disks. However, the existence of such global magnetic fields is not evident in various astrophysical objects, and their origin is not well understood. Thus, we study the effect of small-scale magnetic fields confined within the accretion disk. We review our recent findings on the formation of jets in dynamo-active accretion disks by using 3-D MHD simulations. In our simulations, we found the emergence of accumulated azimuthal magnetic fields from the inner region of the disk (the so-called magnetic tower) and also the formation of a jet accelerated by the magnetic pressure of the tower. Our results indicate that the magnetic tower jet is one of the most promising mechanisms for launching jets from the magnetized accretion disk in various astrophysical objects. We will discuss the formation of cosmic jets in the context of the magnetic tower model.     

Spatiotemporal long-term trends of extreme wind characteristics over the Black Sea

In this study, long-term change of wind characteristics on the Black Sea has been investigated using two widely used data sources, i.e., European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim and National Centers for Environmental Prediction/Climate Forecast System Reanalysis (NCEP/CFSR), spanning 40 years between 1979 and 2018. Spatial and seasonal variability of climatic features such as the wind speed, direction, number and duration of storms, and wind power density are discussed. Wind climate is characterized by strong, durable and stable winds in the northern and western Black Sea, and relatively weak, short-lived and highly-variable winds in the eastern Black Sea. These long-term wind patterns indicate that the eastern part of the basin is likely to be subjected to the impacts of climate change. Long-term stable and strong wind conditions in the southwest part indicate reliable, persistent and sustainable wind energy potential. Long-term and seasonal variation of wind power density (WPD) at 110 m altitude over the Black Sea is investigated. There is a significant difference in WPD values between winter and summer seasons, with around 2.8 times larger WPD in winter than that in summer. In the western Black Sea, narrow confidence intervals observed in each season indicate a low level of variation during a season and ensures stable wind power conditions.     

碳同位素技术在碳质气溶胶源解析中应用的研究进展

概述了国内外14C和13C技术在大气碳质气溶胶源解析中应用的研究进展,指出14C在碳质气溶胶源解析研究中具有不可替代的独特优势,联合采用14C和13C技术有利于解决多种排放源的区分问题;随着碳质气溶胶组分分离技术的进步,对有机碳(0C)和黑碳(BC)等组分中14C的研究获得重要进展;除需深入研究13C的分馏机制外,建立各种排放源在不同区域的δ13C值域“特征谱”的重要性也日益突出;结合14C和13C以外的其他示踪剂、模型和分析方法将提供更多关于气溶胶来源的信息,并减小来源贡献率估算的不确定性.     

Enrichment and Origin of Some Trace Elements in Black Shales from the Early Cambrian in Eastern Guizhou Province

The analysis is based on the elemental geochemistry, ¹³C, ¹⁸O isotope and lithology combination of the black shale, a set assemblage mud and carbon of lithology , in East Guizhou. The coordinated change in spider diagrams of race elements suggests those elements have the same source. The ¹³C, ¹⁸O isotopes, mode of REE partition and characteristic enrichment of elements assemblage in carbonaceous shale show that the deep thermal fluid is added, and the shelf sea basin edge with distribution of hydrothermal activity is propitious to precipitation of ore elements. Evidence from the ³⁴S isotope and redox-sensitive elements show that the hydrostatic hypoxia environment is also conducive to precipitation of elements. The lithologic features (phosphorus, coal-bearing layers) and high content of organic carbon indicate that the deposits are influenced by the upwelling ocean current.     

Analysis of different methods for monitoring the urbanization process

The monitoring of urban sprawl in agricultural and natural areas requires the frequent acquisition of information relative to land cover changes. The loss of high capability agricultural lands is a major problem. The sound management of resources requires the knowledge of the nature and orientation of the urban dynamics.

Remote sensing is a useful tool for highlighting areas where changes have occured,for determining the type of change and for quantifying these changes. A spatial‐temporal analysis of the urban processes is carried out for the urban area of Montreal, Canada. Different sources of information are used: three Landsat MSS satellite images acquired in 1972, 1979 and 1982, planimetric data from the Department of Municipal Affairs of Quebec and statistics compiled by Environment Canada.

The satellite data shows a sharp increase, in the order of 65%, in urban areas during the period under consideration. These results are compared with governmental data derived from classical photo‐interpretation techniques.

On one hand, we observe that the results obtained by automatic classification of the satellite data are superior in the order of between 5% to 30%, depending on the year and the different governmental sources. On the other hand, we discuss problems of homogeneity in the use of terms related to land cover between the various governmental organizations.     

THE SPREAD OF CHANGE IN METROPOLITAN AND NONMETROPOLITAN GROWTH IN THE UNITED STATES, 1940–1976

This article explores the historical, economic, and social factors that shape the recent migration of middle-class Blacks to low-income, urban, Black neighborhoods. It focuses on the meanings associated with this pattern of Black gentrification and the extent to which this residential pattern is consistent with previous models of urban gentrification. Using three years of ethnographic data from a low-income neighborhood in Philadelphia that has experienced an increase in Black middle-class residents, I conclude that this pattern of neighborhood change is distinct from previous models of urban gentrification. In this article, I argue that Black gentrification represents a unique set of opportunities and constraints that produce a group of middleclass African Americans willing to invest their social, economic, and cultural capital into improving the quality of life for low-income Black neighborhoods and their residents.