太湖表层悬浮泥沙遥感定量模式研究

二类水体光学活性成分的复杂性导致了水体光学特性的复杂性。通过对太湖区域实测高光谱数据的分析,进一步认识了太湖水体的光谱特性与悬浮泥沙浓度之间的关系： 最大反射峰波长随着悬浮泥沙浓度的增加向短波方向移动,即“蓝移现象”;敏感波段区域的光谱曲线对波长的积分面积与悬浮泥沙浓度之间具有良好的线性关系,近似后的梯形面积模型能较好地反映太湖泥沙浓度状况,并适用于LandSat/TM等多光谱卫星影像数据反演。梯形面积模型的反演,结果表明太湖区域悬浮泥沙浓度主要集中在30～80 mg·L-1之间,分布呈现湖西、湖南和湖心高,湖东低的格局;与实测数据相比较,反演模型相对误差为6.035%。     

A preliminary investigation on the distribution of heavy metals in surface sediments of the Cona tidal marsh (Venice Lagoon)

Summary Data are from the two series of surface sediment samplings in an interface area between the Venice Lagoon and the mainland. The distribution of heavy metals gives a correlation with polluted source-sites—identified in the channel systems with a highly polluted input—and allows us to identify the localities of accumulation. Restricted to the estuary of the river tributary transporting a high concentration of pollutants into a tidal marsh area of the lagoon, the study shows the effect of the fresh water forcing to distribute heavy metals on surface sediments. Within the scope of this preliminary investigation, indications from sampling identify a sector of the ?Palude di Cona? in this estuary, which is highly suitable for detailed studies on processes affecting heavy-metal distributions in bottom surface sediments of shallow-water areas. Paper presented at the IV Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 22–24, 1987, Rome.     

Morphology and Pore Size Distribution of Biocompatible Interconnected Porous Poly(L-lactic acid) Foams with Nanofibrous Structure Prepared by Thermally Induced Liquid–Liquid Phase Separation

Biocompatible, highly interconnected microporous poly(L-lactic acid) (PLLA) foams with nanofibrous structure, containing pores with average diameter below 1 μm and fibers with diameters of 10² nm scale, were prepared through the thermally induced liquid–liquid phase separation (TIPS) method consisting of quenching of the PLLA solution, freeze extraction with ethanol, and vacuum drying. Diverse foam morphologies were obtained by systematically changing parameters involved in the TIPS process, such as polymer concentration, solvent composition, and quenching temperatures. The morphology of different foams was examined by scanning electron microscopy to characterize the pore size and the pore size distribution. The results showed that most porous foams had a nanofibrous structure with interconnected open pores. In the case of using tetrahydrofuran (THF) as solvent, the higher the PLLA concentration, the smaller the average pore diameter and the narrower the pore size distribution. In the case of using the mixed solvents of THF/DOX (1,4-dioxane) with higher than 6/4 volume ratio, there appeared a maximum value of average pore diameter and a widest pore size distribution at 0.09 g/mL PLLA concentration. The average pore diameter of the foams increased with increasing DOX content in the mixed solvent and ranged from 0.2 to 0.9 μm depending on the process parameters. When the DOX content reached 60% by volume, the morphology of the foams contained some large closed pores with diameter ranging from 1 to 10 μm. By decreasing the quenching temperature, the average pore diameter of foams decreased and the pore size distribution became narrower. All the pore size distribution fit F-distribution equations.     

气泡体积分数对沙质沉积物低频声学特性的影响

由于有机物质分解等原因,实际的海底沉积物中存在气泡,气泡的存在会显著影响沉积物低频段的声学特性,因此研究气泡对沉积物低频段声速的影响机理具有重要意义.考虑到外场环境的不可控性,在室内水池中搭建了大尺度含气非饱和沙质沉积物声学特性获取平台,在有界空间中应用多水听器反演方法首次获取了含气非饱和沙质沉积物300—3000 Hz频段内的声速数据(79—142 m/s),并同时利用双水听器法获取了同一频段的数据(112—121 m/s).在声波频率远低于沉积物中最大气泡的共振频率时,根据等效介质理论,将孔隙水和气泡等效为一种均匀流体,改进了水饱和等效密度流体近似模型.模型揭示了气泡对沉积物低频段声学特性的影响规律,理论上解释了沉积物中声速的降低.通过分析模型预报声速对模型参数的敏感性,根据测量得到的声速分布反演得到了沉积物不同区域的气泡体积分数,气泡体积分数从1.07%变化到2.81%.改进的模型为沉积物中气泡体积分数估计提供了一种新方法.     

Effects of sediment physical properties on the phosphorus release in aquatic environment

Particle size, porosity, and the initial phosphorus concentration in sediments are the main factors affecting phosphorus release flux through the sediment-water interface. Sediments can be physically divided to muddy and sandy matters, and the adsorption-desorption capacity of sediment with phosphorus depends on particle size. According to phosphorus adsorption-desorption experiments, phosphorus sorption capacity of the sediment decreases with the increase of particle dimension. But among the size-similar particles, sediment with a bigger particle size has the larger initial phosphorus release rate. In terms of muddy and sandy sediments, there are inversely proportional relationships between the release rate and the flux. Due to the contact of surface sediment and the overlying water, the release flux from the sediment is either from direct desorption of surface sediment layer or from the diffusion of pore water in the sediment layer, which is mainly determined by sediment particle size and porosity. Generally, static phosphorus release process may include two stages: the first is the initial release. As for coarse particles, phosphorus is desorbed from surface sediment. And for fine particles, phosphorus concentration in water often decreases, mainly from pore water by the molecular diffusion. During the second stage, pore water flows faster in coarse sediment, and phosphorus is easy to desorb from the surface of the particles as diffusion dominates. For the smaller liquid-solid ratio of fine particles and the larger amount of phosphorus adsorption, the release flux from pore water due to diffusion is very small with longer sorption duration.     

Stable Sulfur Isotope Effects Related to Local Intense Sulfate Reduction in a Tidal Sandflat (Southern North Sea): Results from Loading Experiments

Abstract

Anoxic sediment surfaces coloured black by iron monosulfides (“black spots”) evolve in tidal sandflats of the Wadden Sea (southern North Sea) as a result of the degradation of buried organic matter. To follow the short- and long-term effects of organic matter burial on pore water and sediment isotopic biogeochemistry, formation of artificial black spots was initiated on the Groninger Plate (site RP63) in the backbarrier tidal flats of Spiekeroog island. Changes in concentrations (DOC, TA, TOC, sulfate, sulfide, TRS, Fe) and isotopic compositions (sulfate, sulfide, TRS, pyrite, TOC) were followed for up to 12 months and compared to reference areas. 13°C ratios of TOC clearly mirror the early diagenetic degradation of organic matter. At least temporarily closed system sulfate reduction is inferred for the artificial black spot from the variation of sulfate concentrations and stable sulfur isotope partitioning, In the interstitial waters of the black spot, 34S/32S values of coexisting dissolved sulfate and sulfide yield fractionation degrees between ?5 and ?25%. On the reference area, 34S/32S are fractionated by ?32 to ?42% as calculated from the isotope composition of solid phase reduced sulfur and pore water sulfate. Sulfur isotope fractionation seems to increase with decreasing sulfate reduction rate. Limiting factor seems to be the availability of DOC. Between the pyrite pool and the dissolved sulfide in the black spot, no significant isotope exchange is observed within 12 months.     

Focus on sulfur count rates along marine sediment cores acquired by XRF Core Scanner

The aim of this study is to investigate the information provided by sulfur count rates obtained by X‐ray fluorescence core scanner (XRF‐CS) along sedimentary records. The analysis of two marine sediment cores from the Niger Delta margin shows that XRF‐CS sulfur count rates obtained at the surface of split core sections with XRF‐CS correlate with both direct quantitative pyrite concentrations, as inferred from X‐ray powder diffraction (XRD) and sulfur determination by wavelength dispersive X‐ray fluorescence (WD‐XRF) spectrometry, and total dissolved sulfide (TDS) contents in the sediment pore water. These findings demonstrate the potential of XRF‐CS for providing continuous profiles of pyrite distribution along split sections of sediment cores. The potential of XRF‐CS to detect TDS pore water enrichments in marine sediment records, even a long time after sediment recovery, will be further discussed. Copyright © 2016 The Authors. X‐Ray Spectrometry Published by John Wiley & Sons Ltd.     

Pore Structure Analysis of Porous Particles by Modelless and Micropore Method

The modelless (ML) and micropore (MP) methods for the pore structure analysis of porous particles have been studied. Concerning the ML method, it has been shown that the Kiselev equation can only be used to describe condensation and evaporation in capillaries, but cannot be used to describe the increase and decrease of the thickness of the adsorption layer. Strictly speaking, therefore, the ML method is not modelless even for the pore core size distribution. A comparison between the ML method and methods using an equivalent pore model is given. The results of using the ML method in conjunction with a certain pore model are little less accurate than those obtained by adopting the equivalent pore model straightaway. The parameters required for the calculation of both the pore core size and the pore size distribution as well as the conversion between these two calculations are given. Concerning the MP method, it has been shown that the three types of v-t curves, the theoretical foundation of the MP method, are not in one to one correspondance to the three kinds of adsorption mechanism. From the viewpoint of accuracy, the MP method has no advantage over the methods which are based on the condensation mechanism, both have their own merits.     

Mössbauer spectroscopy and X-ray fluorescence studies on sediments from the methanic zone of the Helgoland mud area,North Sea

⁵⁷Fe Mössbauer spectroscopy (MS) and X-ray fluorescence spectroscopy (XRF) were used to determine the identity of iron(III) oxides in surface (top 30 cm ) and subsurface (> 30 cm – 500 cm)sediments from the Helgoland mud area in the German Bight of the North Sea. A 500 cm-long sediment core was cut in 25cm sections while only the top 10 cm of a 30 cm-long sediment core was sampled. Using a MIMOS spectrometer, MS spectra were recorded at 293K (RT) in backscattering geometry. At 80K and 5.5K, MS analysis was carried out in transmission geometry. At RT and 80K only illite was observed, but at 5.5K lepidocrocite was revealed in the MS spectra. The relation between Fe(III) and Fe(II) doublets of illite did not significantly vary with depth, but the relative amount of lepidocrocite increased with depth reaching about 24 % of iron phases, as revealed by MS. XRF measurements showed that the amount of Fe in the sediments varied with depth but was always less than 4 % of total elemental composition. The main component of the sediment was silica and its depth profile alternated with those of other elements, especially aluminium and iron. It was observed that elevated concentrations of dissolved iron in the subsurface sediment of the Helgoland mud area correlated with the depth-wise distribution of distinct microbial populations presumably due to microbial reduction of excess bioavailable iron minerals such as lepidocrocite. These results are thus, important in the context of microbe-mineral interactions in marine sediments as iron oxides are an electron acceptor for microbial anaerobic respiration.     

Characterizing the Evolution of Porosity during Controlled Drug Release

Nuclear magnetic resonance (NMR) techniques have been successfully used to characterize the evolving pore structure of partially soluble pharmaceutical pellets as they absorb water and release soluble components. The restricted diffusivity of water trapped within pellets, which have been immersed in water for differing times, has been measured by pulsed field gradient NMR. These measurements have been used to calculate the surface-to-volume ratio and tortuosity of the pore structure. A one-shot Carr–Purcell–Meiboom–Gill sequence has been used to measure the spin–spin (T ₂) relaxation time of water trapped within the pellets. These data have been regularized and then analyzed by the Brownstein–Tarr model to provide a pore size distribution for the pellets as a function of increasing immersion time. It has been found that pore structure changes significantly as water enters the pellet matrix. Two pellet formulations (herein referred to as placebo and drug-loaded) were studied and showed the same trends of a decreasing surface-to-volume ratio and tortuosity with increasing immersion time. At an immersion time of 10 min, both of these parameters decreased to approximately 70% of their values compared to an immersion time of 2 min. The placebo material tested consistently had both a higher tortuosity and surface-to-volume ratio than the drug-loaded material. At an immersion time of 2 min, the tortuosity for the placebo and drug-loaded materials were about 18 and about 10, respectively, and surface-to-volume ratios of about 6 μm⁻¹ and about 5 μm⁻¹, respectively. The materials tested also show changes in their pore size distribution with immersion time. In both formulations the mean and modal pore sizes increase with immersion time. The placebo material maintains an approximately similar mean and modal pore size, about 2 μm over the timescales studied, suggesting a more symmetric pore size distribution. In the drug-loaded pellets the mean pore size is much higher than the modal pore size, their values being 6.5 and 2.1 μm after 10 min immersion time, respectively. Authors' address: Michael D. Mantle, Department of Chemical Engineering, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, UK     

Pore formation in in situ processed MgB2 superconductors

MgB₂ bulks were prepared by an in situ process which utilizes the reaction between boron and magnesium powder. The reaction time was fixed at 0.5 h and the temperature was changed from 600 °C to 1000 °C. The density decrease due to pore formation and mass (mainly magnesium) loss during the formation reaction of MgB₂ was observed in all samples. In addition to the pore formation, a pellet expansion which can be explained by the outgrowth of MgB₂ grains was also observed. Two different mechanisms were adopted to explain the pore formation; Kirkendall pores formed at a temperature below the melting point (m.p.) of magnesium by a difference in the diffusivity between magnesium and boron, and the pores formed at a temperature above the m.p. by melting of magnesium and a capillary movement. The density, T_c and J_c results suggest that the current carrying capacity can be improved by a careful control of the process parameters regarding a pore evolution.     

黄河口海域悬浮物浓度Landsat8 OLI分段线性反演

黄河每年输送大量泥沙进入渤海。研究黄河口海域悬浮物浓度，对于黄河输沙以及周边海域的环境监测具有重要意义。利用2011年夏、冬两季实测遥感反射率以及同步测量悬浮物浓度数据，开展了黄河口海域悬浮物浓度分段线性反演研究。结果表明，不同浓度范围下，悬浮物浓度反演的敏感波段不同；浓度小于等于50 mg·L-1(≤50 mg·L-1)，敏感比值波段为(600~700 nm)/(400~600 nm)，浓度高于50 mg·L-1(＞50 mg·L-1)，敏感比值波段为(750~900 nm)/(420~720 nm)，Landsat8 OLI的对应组合方式分别为B4/B2和B5/B3；根据上述浓度分段范围分别建立线性模型，其精度R2，RMSE和APD分别为0.873 5，4.08 mg·L-1和22.81%(≤50 mg·L-1)，以及0.969 3，102.96 mg·L-1和17.51%(＞50 mg·L-1)，整个浓度下三个精度参数分别为0.975 3，67.03 mg·L-1和20.45%，均优于常用单一模型在分段和整体浓度下的相应参数，且具有良好的稳定性。分段线性模型，更适合浓度变化大的黄河口海域悬浮物浓度反演。     

不同水体中有色可溶性有机物质荧光光谱定量分析研究

有色可溶性有机物(CDOM)是指水体中对紫外及可见光均有光吸收的溶解有机物,能对水色产生影响,是自然生态系统、水色光学遥感、水体碳循环研究中必不可少的环境因素。由于CDOM具有荧光特性,荧光光谱技术已成为开展CDOM研究的重要手段,被用于CDOM的来源、分布及其变化规律的研究。文章主要利用荧光检测技术,研究了不同水体CDOM的发射荧光光谱峰面积、荧光峰强度与其浓度间的变化关系,发现在低浓度范围内,发射光谱峰面积和荧光强度与CDOM浓度具有良好的线性关系(r2＞0.98);不同浓度的CDOM水溶液的发射光谱峰面积及其荧光强度随浓度的变化趋势是一致的。文章首次利用低浓度下CDOM的发射光谱峰面积与浓度间的线性关系,建立了适合于水体中组成复杂的CDOM的定量分析方法,拓展了荧光分析技术在CDOM研究中的应用。     

Pore-size distributions of cationic polyacrylamide hydrogels of different compositions maintained at the same swelling capacity

Pore-size distributions have been measured for cationic acrylamide-based hydrogels of different compositions maintained at the same swelling capacity (27.8 ± 0.7 g swollen gel/g dry gel) by varying the ionic strength of the surrounding solution. Swelling equilibria were measured at about 6°C in pure water and aqueous sodium azide solutions ranging in concentration from to 10^?3 to 10^?1 M. The mixed-solute-exclusion method (introduced by Kuga) was used to obtain the experimental solute-exclusion curve, which represents the amount of imbibed liquid inside the gel inaccessible to a solute of radius r. The pore-size distribution was obtained by using Casassa's Brownian-motion model and numerically solving the Fredholm integral equation. The modes of the pore radii range from 20.4 to 47.1 Å for acrylamide-based hydrogels containing varying amounts of cationic comonomer (1.5 and 4.0 %M), crosslinker (0.3 and 1.0 %C), and initial concentration of total monomer (15 and 35 % T).     

Determining pore sizes using an internal magnetic field

A concept is proposed to measure the pore size length scale by the internal magnetic field (B_i) in porous materials. The spatial distribution of the magnetic field inhomogeneity, a result of the magnetic susceptibility contrast between the porous material and the fluid, reflects the underlying pore geometry. Diffusion in B_i causes the initial decay of magnetization. At long times, the effect of B_i saturates when the diffusion length reaches a characteristic pore size. This method is independent of surface spin relaxation in determining pore sizes. Nuclear magnetic resonance experiments on packed glass beads and sedimentary rock samples will be presented.     

海南岛沿岸海域水体漫衰减系数光谱分析及LiDAR测深能力估算

机载激光雷达测深是近年来蓬勃发展的主动式水深测量方法,能够快速精准地获取近岸水深和水下地形,特别是对于浅海、岛礁等船只无法达到的区域具有显著优势。而机载激光雷达系统的测深能力主要受到水体浑浊度的影响。激光测深实验中对实验区域的水体浑浊度研究将有助于实验方案的设计。以中国海南岛沿岸海域为例,研究了该海域水体浑浊度和机载激光雷达测深系统CZMIL(coastal zone mapping and imaging LiDAR)测深能力之间的关系,建立了运用水体漫衰减系数估算机载激光雷达测深系统测深能力的算法。首先分析并确定了实验区域的漫衰减系数K_d(490)反演算法;其次,运用该区域实测光学数据建立了漫衰减系数K_d(490)和K_d(532)之间的数值关系;接着总结了K_d(532)和CZMIL系统最大测深值之间的关系;最后运用MODIS数据合成了海南岛沿岸海域在CZMIL系统海道测量模式下的测深能力空间分布图,重点分析了海口和陵水附近海域的最大可测水深分布情况。为海南岛沿岸海域开展激光测深实验提供了参考和依据。     

The mechanisms of contaminants release due to incipient motion at sediment-water interface

Sediments in many rivers and lakes are subjected to resuspension due to a combination of hydrodynamics.However,the roles of contaminant-contained dissolved and particulate sediments during the resuspension release are rarely studied.This study focuses on the release quantity of contaminants in both water phase and solid phase.Conservative tracer(NaCl)and reactive tracer(Phosphorus)were respectively added to cohesive fine-grained sediments and non-cohesive coarse-grained sediments.A range of typical shear stress was conducted to characterize the time-depended release of contaminants in a laboratory flume.When the sediment started to move,the concentration of contaminant in the overlying water increased with the bed shear stress,but the dissolved contaminants responded faster than the particulate ones.The observed contaminant release process can be divided into three main stages:the initial two hours fast mixing:the release contribution of pore water could reach up to 75%;the middle 4–6 h adsorption:the partitioning coefficient of contaminant between water phase and solid phase decreased over the time,and the adsorption of contaminates from resuspended sediment dominated the negative release;the last equilibrium stage:the desorption and adsorption reached equilibrium,and the reactive contaminant made an impact on the water quality in the solid phase.The existing formulas to evaluate the release flux are far from practice meaning as the sediment contaminants undergo a very complex release process.     

Electronic structure of heavy-metal azides

Calculations of the electronic crystal structure in the basis of pseudoatomic orbitals are used to investigate major heavy-metal azides AgN ₃ and TlN ₃. Special features and composition of the energy bands are analyzed for two cases: with allowance for spin-orbit interaction and without it. The chemical bond structure determined by the electron-density distribution is also examined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 84–88, October, 2004.     

三维荧光与神经网络研究城市河流沉积物孔隙水有机物组成与结构特征

应用三维荧光技术结合自组织神经网络方法,研究典型城市河流沉积物孔隙水中水溶性有机物(DOM)与颗粒性有机物(POM)组成结构及空间分布特征。自组织神经网络是一种非监督神经网络算法,能够从有机物三维光谱中提取不同的荧光组分,表征各组分的含量。沉积物是重要的有机碳库,而沉积物孔隙水中有机物的多寡可直接反映其环境特征。人们对水体中沉积物孔隙水中的DOM与营养盐特征的研究较多,而对POM的研究较少,尤其对重污染城市支流河的研究更少。因此,选取沈阳市白塔堡河为研究对象,沿河源、农村、城市区域河段采集沉积物孔隙水样品,提取DOM与POM,检测样品的三维荧光光谱。DOM的f_450/500值为1.82～1.91,表明DOM主要是微生物源;POM的f_450/500值为1.42～1.68,表明POM主要以陆地输入为主。自组织神经网络解析DOM与POM含有类酪氨酸、类色氨酸、类富里酸与类胡敏酸等物质,类酪氨酸主要源于新鲜的具有高氧化的类蛋白物质,而类色氨酸主要为微生物代谢产物。DOM的各组分丰度之和为POM的2倍,类酪氨酸平均相对丰度在50%以上,类色氨酸的平均相对丰度为18.8%～23.1%,类富里酸相对丰度比类胡敏酸的高,但两者在有机物组分所占比重小。通过主成分分析,DOM与POM特征呈现沿河源、农村、城市区域河段变化,表明白塔堡河深受人类活动的影响。