Abrupt climatic events recorded by the Ili loess during the last glaciation in Central Asia: Evidence from grain-size and minerals

The loess record of Central Asia provides an important archive of regional climate and environmental changes. In contrast to the widely investigated loess deposits in the Chinese Loess Plateau, Central Asian loess-paleosol sequences remain poorly understood. Here, we present an aeolian loess section in the southern Ili Basin. Based on granularity and mineralogical analyses, we reconstruct climatic changes during the last glaciation. The results indicated that most of the abrupt climatic events (such as Dansgaard-Oeschger events and Heinrich events) were imprinted in this loess section, although their amplitudes and ages showed some differences. Compared with the millennial oscillations recoded in loess and stalagmites in East Asia, the arid Central Asia responded more sensitively to the warming events than to the cooling events. The shifting trajectory of westerlies across Central Asia played an important role in dust deposition during the stadials. The North Atlantic climatic signals may have been transmitted from Central Asia to the East Asian monsoon regions via the westerlies

The Technology and Application of Improving Bearing Capacity of Deep Peat Soil Subgrade

Peat soil is widely distributed in more than 500 countries around the world, covering an area of over 4 million square kilometers, among which the distribution area in China is about 40000 square kilometers, and most of Peat soil is distributed in swamps and forests. Peat soil is with high content of organic matter, poor engineering properties and low bearing capacity, which is very unfavorable to the safety and functionality of infrastructure construction. The Belt and Road, and the other two parts of the peat soil are studied in this paper. The key technologies of peat soil foundation are studied through literature review and comparative study. This will provide theoretical and technical support for repairing bridges, roads and houses in the distribution area of peat soil, and provide the theoretical basis and technical foundation for the construction of the “peat” Road area. Chinese Library Classification: TU0

Adsorption Properties of Ni(II) by D301R Anion Exchange Resin

The adsorption of Ni(II) with D301R resin was investigated in this paper. The results showed that the saturated extent of adsorption Ni(II) by the resin was 84.3 mg/g. The equilibrium data of Ni(II) sorption was better described by Langmuir isotherm model (r2=0.994) while that of Ni(II) sorption also fitted in Freundlich isotherm model within the experimental concentration range. The amount of the constant (q0) of Ni(II) under 298 K in Langmuir model was 76.92 mg/g, which was close to the experimental results. The constant n was within 2–10 in Freundlich model; it was shown that adsorption of Ni(II) by the resin was easy to take place. The uptake kinetics followed the Lagergren pseudo-first-order rate equation (r2=0.9813). The particle diffusion controlled the adsorption process of Ni(II). The coefficient of the intraparticle diffusion increased with the increase of the pH values and the concentration of Ni(II) in aqueous solution. There was a drop of 20.1 cm−1 for the bending vibration frequency of N–H bond. Results showed that the adsorption of Ni(II) by D301R anion exchange resin was the surface complexation through the infrared spectrum analysis

Holocene dust deposition in the Ili Basin and its implications for climate variations in Westerlies-dominated Central Asia

Understanding Holocene paleoclimate in arid Central Asia (ACA) is helpful for predicting future climate. However, Holocene climate patterns and their forcing mechanisms across ACA are vigorously debated in the context of global climate change. Here, we present a Holocene loess profile (SGX) from the Ili Basin in the Westerlies-dominated Central Asia. Based on high-resolution, medium-grained (38-63 mu m) quartz optically stimulated luminescence (OSL) dating, and grain size and color measurements, we reconstruct the Holocene paleoclimate. OSL geochronology indicate that this SGX loess profile covers the last 11.5 ka, and grain size analyses reveal that the sediments are sandy loess, and the environmentally sensitive fractions are < 35.6 mu m and 35.6-252 mu m which represent suspensions after dust storms and proximal deposit components transported mainly during dust storms, respectively. And the redness and yellowness in the loess profile are closely related to the concentrations of hematite (Hm) and goethite (Gt); the ratio Hm/Gt also can be used to reflect the evolution of dry/humid conditions in Central Asian loess. The Holocene Westerlies-dominated climate in ACA is characterized by a dry early Holocene, persistently wet conditions in the middle and late Holocene, and a climatic optimum in the late Holocene. The winter solar insolation at 60 degrees N is considered the major forcing of Holocene climate evolution in ACA

Calculation of pH Values for Mixed Waters

Mixing of waters with different compositions is a common phenomenon. The pH of mixed water can be calculated by introducing charge neutrality equation into the equations for equilibrium distribution calculation of species in water. In this paper, the equations thus obtained were solved by golden section method. To verify the calculation method, laboratory experiments were done for three sets of mixing water. The results showed the calculated pH values are in good agreement with measured ones

Quantifying the provenance of dune sediments in the Taklimakan Desert using machine learning, multidimensional scaling and sediment source fingerprinting

Study of windborne sediments in the Taklimakan Desert is of great significance in the context of global change. Much effort has gone into characterizing the Taklimakan dune sediments, but quantitative understanding of the source contributions from the surrounding mountains is lacking. Accordingly, using elemental data, we applied random forest (RF), multidimensional scaling (MDS) and sediment source fingerprinting (SSF) to examine homogenization of the dune sediments in the desert, and to quantify the contributions of key sources. The results underscored the heterogeneity of geochemistry in dune sediments in the Taklimakan Desert. On the basis of dominant wind directions and the drainage network in the Tarim Basin, as well as lithologic features in the surrounding mountains, potential sources of sand dune sediments comprised three groups: "Tianshan", "PamirsKunlun", and "Kunlun-Altun". Using the FingerPro and MixSIAR fingerprinting models, our results suggested that the contributions of the three sources to the target dune sediments were: "Kunlun-Altun" > "Pamirs-Kunlun" > "Tianshan". However, substantial variations in the respective contributions were observed for different target dune samples. Although both the frequentist and Bayesian models performed well in the calculations of the relative source proportions based on goodness of fit (GOF) (0.97 on average for the two models respectively), virtual mixtures (VM) tests indicated that the frequentist model returned more accurate predictions. Consequently, using the frequentist results, we propose that the "Kunlun-Altun"-derived sediment (an average of 56%) is mainly delivered to the Taklimakan Desert via fluvial transport; sediment supply from the "Pamirs-Kunlun" source (33%) depends on fluvial and wind transport and that aeolian processes are mainly responsible for distribution of the "Tianshan"-derived sediment (11%) in the desert by transporting the fine fraction. Our findings thereby highlight the interaction between fluvial and aeolian transport within the Tarim Basin

Geochemical composition of Tajikistan loess and its provenance implications

The Tajikistan (TJ) loess has great significance for the study of Quaternary climate changes and dust source in Central Asia. In this paper, we investigate the geochemical composition and provenance of loess. Our results show that the major elements, in order from high to low average content, are SiO2 &gt; Al2O3 &gt; CaO &gt; Fe2O3 &gt; MgO &gt; K2O &gt; Na2O &gt; TiO2 &gt; P2O5 &gt; MnO. Fe, Ti, P and Mn contents in loess are similar to those in the UCC, as is the case with Si, Al and Mg contents in paleosols. Ca is distinctly enriched in loess, and Si, Al and K are depleted. Na is depleted in both loess and paleosols, and P is depleted only in paleosols. In contrast to the UCC, paleosols show enrichments in all trace elements except for Ba, Sr and Zr, but in loess, some trace elements (e.g., Ba, Co, Ni and Zr) show depletion. The CIA value of TJ loess is lower than that of Kashmir loess, the latter being influenced by differences in the sorting and tectonic environment. There are no great changes about provenance during the formation of TJ loess, and the deposit areas have a shorter distance to the provenance. Geochemical data and atmospheric circulations demonstrate that the TJ loess was mainly transported by the near surface northerly or northwesterly winds, but there may be an additional and local source making a certain contribution to the formation of loess deposits in the south of Tianshan. (C) 2016 Elsevier B.V. All rights reserved

Provenance of sub-aerial surface sediments in the Tarim Basin, Western China

Provenance of surface sediments in the Tarim Basin is important for understanding the aridification of the Asian interior and the interplay between the Westerlies and the Asian monsoon. Although the desert sands in the Taklamakan Desert have been studied intensively, there is no consensus regarding their provenance, namely, the dispute exists between various sand sources in different parts of the desert and homogenization of the sands in the entire desert. Moreover, other surface sediments in the basin are poorly investigated. Here we examine the particle-size-specific rare earth element (REE) and trace element characteristics of various surface sediments from different regions of the basin. The results reveal that the 63 mu m fraction are dominated by regional-derived materials, mainly from the adjacent mountains (e.g. Pamirs, Kunlun, Kuruktag, Altun, Tianshan Mountains), and the fluvial systems are an important additional transport mechanism. Our findings potentially provide an improved understanding of the dust cycle and atmospheric circulation patterns in Central Asia, and of the provenance of loess in North China