本实用新型涉及一种微升量气体单分子化合物稳定同位素组成分析装置,该装置包括气相色谱‑连续流稳定同位素质谱仪、高真空系统、岩石样品分段加热脱气装置、岩石样品高真空电磁破碎脱气装置、除水装置、活性炭冷指。岩石样品分段加热脱气装置通过管线Ⅰ与岩石样品高真空电磁破碎脱气装置相连,该管线Ⅰ上设有高真空阀Ⅱ、Ⅲ;高真空阀Ⅱ与Ⅲ之间的管线Ⅰ上设有管线Ⅱ,该管线Ⅱ的末端连有管线Ⅲ、Ⅳ;管线Ⅲ连有除水装置、活性炭冷指、高真空六通阀,其末端与管线Ⅳ相连;管线Ⅳ上连有高真空系统;高真空六通阀连有载气输入管、样品环、气相色谱‑连续流稳定同位素质谱仪;管线Ⅱ与Ⅲ及Ⅳ相接处设有薄膜真空计。本实用新型灵敏度高、分离效果好。
2016-12-28Pedogenic carbonates (calcretes) have often been proposed as possible markers of the pedogenetic processes in soils under semi-arid climate. However, precise chronological constraints on, their formation are required in order to investigate the climatic and paleo-environmental conditions that prevailed during and after their formation, and to improve our understanding of the, physical and chemical conditions that promoted their development and preservation. Moreover, these authigenic calcium carbonate precipitates provide us with an interesting test of the U-Th radioactive disequilibrium dating method, the reliability of which has been demonstrated extensively in aragonitic corals and calcitic continental speleothems, but which remains much more questionable in highly porous, chemically and mineralogically complex media such as soil profiles. We report here U-238-U-234-Th-230 radioactive disequilibrium analyses measured by Thermo-Ionization Mass Spectrometry in calcretes from two sites in southwest India. Since calcretes are impure carbonates mixed with various amounts of parent rock and weathered minerals, all ages must be computed using the isochron technique, involving the extraction of several coeval subsamples from the same soil horizon and U-Th analyses after total dissolution (TSD) method, in order to correct for the detrital component. Th-232 is usually used as index of the detrital contamination, and the isochron age is derived from the isotopic composition (Th-230/U-238; U-234/U-238) of the pure authigenic carbonate end-member of the mixing line. Our results show that each set of samples taken from decimetric blocks is characterized by a well-defined isochron line in a 3-D Osmond diagram (Th-232/U-238; Th-230/U-238; U-234/U-238). The regression lines obtained for most of the samples show probabilities of fit satisfying the mathematical assumptions of the isochron model (in most cases 0.05), and mean square weighted deviations (MSWD) values around 1. The compositions of the end-members are highly variable between the different isochrons, both for the carbonate phase, indicating various ages of cristallisation, and for the detrital phase, indicating various origins and compositions. Notably, our data demonstrate that the detrital component is in all cases out of secular equilibrium, by contrast with the standard paradigm of dirty carbonate dating, which is based on the assumption of average continental crust Th/U elemental ratio, and secular equilibrium values of the ((Th-230/U-238) and (U-234/U-238) ratios. At the first site (Coimbatore), we obtain U-Th ages between 304 +/- 38 ka and 44 +/- 2.9 ka (2 sigma) from the base to the top of the profile. These suggest discontinuous precipitation of the different fades in good agreement with micro morphological observations. At the second study site (Gundlupet), the carbonate nodules sampled from two different profiles, yield consistent ages of 200 ka, which suggests that precipitation of nodular carbonate occurred across the entire pediment toposequence during a single event. Surprisingly, in mere contradiction with the standard model of impure carbonate dating, two puzzling samples display vertical isochrons, i.e., variable Th-232/U-238 without any variation of the Th-230/U-238 and U-234/U-238 ratios. Such patterns require extremely high Th-232/U-238 ratios, in an as yet unidentified detrital phase. Taken at face value, these results suggest that no clear correlation can be inferred between the precipitation of these pedogenic carbonates and major orbitally-driven climate variations recorded in other archives during the last glacial/interglacial cycles. (C) 2016 Elsevier B.V. All rights reserved.
2016-12-23 Web of ScienceAeolian desertification is poorly understood despite its importance for indicating environment change. Here we exploit Gaofen-1(GF-1) and Moderate Resolution Imaging Spectroradiometer (MODIS) data to develop a quick and efficient method for large scale aeolian desertification dynamic monitoring in northern China. This method, which is based on Normalized Difference Desertification Index (NDDI) calculated by band1 & band2 of MODIS reflectance data (MODIS09A1). Then we analyze spatial-temporal change of aeolian desertification area and detect its possible influencing factors, such as precipitation, temperature, wind speed and population by Convergent Cross Mapping (CCM) model. It suggests that aeolian desertification area with population indicates feedback (bi-directional causality) between the two variables (P < 0.05), but forcing of aeolian desertification area by population is weak. Meanwhile, we find aeolian desertification area is significantly affected by temperature, as expected. However, there is no obvious forcing for the aeolian desertification area and precipitation. Aeolian desertification area with wind speed indicates feedback (bi-directional causality) between the two variables with significant signal (P < 0.01). We infer that aeolian desertification is greatly affected by natural factors compared with anthropogenic factors. For the desertification in China, we are greatly convinced that desertification prevention is better than control.
2016-12-22 Web of ScienceThe success of a biological invasion relies on the environment and is closely linked to factors such as water and temperature. Invasive plant species display different seed characteristics, including shape. Field sandbur (Cenchrus pauciflorus) is a globally widespread invasive species capable of adapting to broad environmental conditions. However, its germination response to water and temperature still remains unclear. C. pauciflorus contains two seeds in the same bur that differ in size: big seeds (M) and small seeds (P). Separate greenhouse experiments were conducted under different temperature regimes (0/10 degrees C, 5/15 degrees C, 10/20 degrees C, 15/25 degrees C, 18/28 degrees C, 20/30 degrees C and 25/35 degrees C) and water potentials (-1.50Mpa, -1.00Mpa, -0.75Mpa, -0.50Mpa, -0.25Mpa and OMpa) for M and P seeds. The results support the hypothesis that germination of C. pauciflorus is significantly influenced by seed type, temperature and water potential. M and P seeds responded differently to varied alternative temperatures and water potentials. However, M and P seeds were more sensitive to water potential than to temperature. Optimal conditions for M and P seed germination were measured at 25/35 degrees C (night temperature/day temperature) and 20/30 degrees C, respectively. In contrast, the highest germination rate was observed for the OMpa of the water potential treatment. Additionally, base temperature (T-base) and base water potential (W-base) were lower for M (7.7 degrees C, -1.11Mpa at 10/20 degrees C, and -1.07Mpa at 20/, base, 30 degrees C) than for P (9.4 degrees C, -0.92Mpa at 10/20 degrees C, and -0.52Mpa at 20/30 degrees C). These different germination strategies of M and P seeds with respect to temperature and water potential increased overall plant propagation. These results indicate that tropical and subtropical regions water potentials beyond -0.50Mpa (10/20 degrees C) or -1.00Mpa (20/30 degrees C) face a potential risk of C. pauciflorus invasion.
2016-12-19 Web of ScienceOperational application of a remote sensing-based two source energy balance model (TSEB) to estimate evaportranspiration (ET) and the components evaporation (E), transpiration (T) at a range of space and time scales is very useful for managing water resources in arid and semiarid watersheds. The TSEB model uses composite land surface temperature as input and applies a simplified Priestley-Taylor formulation to partition this temperature into soil and vegetation component temperatures and then computes subsequent component energy fluxes. The remote sensing-based TSEB model using component temperatures of the soil and canopy has not been adequately evaluated due to a dearth of reliable observations. In this study, soil and vegetation component temperatures partitioned from visible and near infrared and thermal remote sensing data supplied by advanced scanning thermal emission and reflection radiometer (ASTER) are applied as model inputs (TSEBCT) to assess and refine the subsequent component energy fluxes estimation in TSEB scheme under heterogeneous land surface conditions in an advective environment. The model outputs including sensible heat flux (H), latent heat flux (LE), component LE from soil and canopy from the TSEBCT and original model (TSEBPT) are compared with ground measurements from eddy covariance (EC) and larger aperture scintillometers (LAS) technique, and stable isotopic method. Both model versions yield errors of about 10% with LE observations. However, the TSEBCT model output of H and LE are in closer agreement with the observations and is found to be generally more robust in component flux estimation compared to the TSEBPT using the ASTER data in this heterogeneous advective environment. Thus given accurate oil and canopy temperatures, TSEBCT may provide more reliable estimates of plant water use and values of water use efficiency at large scales for water resource management in arid and semiarid landscapes. (C) 2016 Elsevier B.V. All rights reserved.
2016-12-15 Web of ScienceAsian dust particulate is one of the primary aerosol constituents in the Earth-atmosphere system that exerts profound influences on environmental quality, human health, the marine biogeochemical cycle, and Earth's climate. To date, the absorptive capacity of dust aerosol generated from the Asian desert region is still an open question. In this article, we compile columnar key absorption and optical properties of mineral dust over East and Central Asian areas by utilizing the multiyear quality-assured datasets observed at 13 sites of the Aerosol Robotic Network (AERONET). We identify two types of Asian dust according to threshold criteria from previously published literature. (1) The particles with high aerosol optical depth at 440 nm (AOD(440) >= 0.4) and a low Angstrom wavelength exponent at 440-870 nm (alpha = 0.4 and 0.2 < alpha < 0.6 are designated as Transported Anthropogenic Dust (TDU), which is mainly dominated by dust aerosol and might mix with other anthropogenic aerosol types. Our results reveal that the primary components of high AOD days are predominantly dust over East and Central Asian regions, even if their variations rely on different sources, distance from the source, emission mechanisms, and meteorological characteristics. The overall mean and standard deviation of single-scattering albedo, asymmetry factor, real part and imaginary part of complex refractive index at 550 nm for Asian PDU are 0.935 +/- 0.014, 0.742 +/- 0.008, 1.526 +/- 0.029, and 0.00226 +/- 0.00056, respectively, while corresponding values are 0.921 +/- 0.021, 0.723 +/- 0.009, 1.521 +/- 0.025, and 0.00364 +/- 0.0014 for Asian TDU. Aerosol shortwave direct radiative effects at the top of the atmosphere (TOA), at the surface (SFC), and in the atmospheric layer (ATM) for Asian PDU (alpha < 0.2) and TDU (0.2 < alpha < 0.6) computed in this study, are a factor of 2 smaller than the results of Optical Properties of Aerosols and Clouds (OPAC) mineral-accumulated (mineral-acc.) and mineral-transported (mineral-tran.) modes. Therefore, we are convinced that our results hold promise for updating and improving accuracies of Asian dust characteristics in present-day remote sensing applications and regional or global climate models.
2016-12-15 Web of ScienceSemi-natural lands are not intensively managed lands, which have ecological significance in protecting artificial oasis and preventing desertification in arid regions. The significant shrinkage and degradation of semi-natural lands in the land-use intensification process have caused severe desertification. However, there is a knowledge gap regarding the spatio-temporal pattern and detailed classification of semi-natural lands and its quantitative relationship with desertification. Taking the Tarim Basin as an example, we proposed a comprehensive classification system to identify semi-natural lands for 1990, 2000, and 2010, respectively, using multi-source datasets at large scales. Spatio-temporal changes of semi-natural lands were then characterized by map comparisons at decade intervals. Finally, statistical relationships between semi-natural lands and desertification were explored based on 241 watersheds. The area of semi-natural lands in Tarim Basin was 10.77 x 10(4) km(2) in 2010, and desert-vegetation type, native-oasis type, artificial-oasis type, saline type and wetland type accounted for 59.59%, 14.65%, 11.25%, 9.63% and 4.88% of the total area, respectively. A rapid loss of semi-natural lands (9769.05 km(2)) was demonstrated from 1990 to 2010. In the fragile watersheds, the semi-natural lands were mainly converted to desert; while in the watersheds with advanced oasis agriculture, artificial-oasis type reclaimed to arable land was the major change. The occurrence of desertification was closely related to the type, area proportion and combination patterns of semi-natural lands. Desertification was prone to occur in regions abundant in desert-vegetation type and saline type, while less serious desertification was observed in regions with high proportion of artificial-oasis type and wetland type. Policy intervention and reasonable water resource allocation were encouraged to prevent the substantial loss of semi-natural lands, especially for the water-limiting watersheds and periods. (C) 2016 Elsevier B.V. All rights reserved.
2016-12-15 Web of ScienceThe mineralogy of the clay fraction of soils is a major determinant of the behavior of soil. Conventionally these clay minerals have been determined using techniques such as X-ray Diffraction (XRD), but new complementary methods such as infrared spectroscopy can be used to rapidly and economically predict these minerals. This paper presents a methodology to predict these clay minerals at high-resolution that adhere to GlobalSoilMap (GSM) standards. Mid-infrared (MIR) spectroscopic models were formulated for clay minerals kaolinite, illite and smectite using partial least squares regression (PLSR) and legacy quantitative XRD determinations. Very strong models were achieved for kaolinite, illite and smectite and the root mean square error of cross validation (RMSECV) were all <12 wt.%. Spectroscopic models were applied to 11,500 samples from western Victoria and harmonized to the GSM specified depth intervals using equal area splines. Clay minerals were then mapped using data mining model trees with a 10-fold cross validation to derive a mean prediction estimate and 90% prediction interval. Spatial models accounted for 26 to 77% of the total variation with kaolinite predictions for all 6 GSM depths 65%. Kaolinite is the dominant soil clay mineral of western Victoria for uplands and weathered volcanic terrains. Illite concentrations are higher where associated with weathered granitic plutons and in aeolian deposits of semi-arid environments. Smectite tends to occur associated with depressions of plains (volcanic and sedimentary). Further supplementation of additional sites and samples for landscapes with relatively sparse observations should contribute to refined and improved maps of these clay minerals. (C) 2016 Elsevier B.V. All rights reserved.
2016-12-15 Web of Science