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241.
Aluminum in the macrotidal Yalujiang estuary: Partitioning of Al along the estuarine gradients and flux 总被引:1,自引:0,他引:1
Water samples were collected from the Yalujiang estuary in both flood periods (August 1992 and August 1994) and dry season (May 1996) and were analyzed for aluminum (Al). Al behaves non-conservatively in the Yalujiang estuary, and a significant loss (70–80%) in dissolved concentration is observed in the upper estuary, in spite of seasonal variation in water discharge and sediment load. About 0.4×106, tons of Al is annually transported from Yalujiang to the estuary, of which the particulate pool clearly dominates. The particulate Al flux through the Yalujiang contributes 35% of the total Al input from Chinese rivers to the Yellow Sea. The data sets from size fractionation and C-18 SPE separation demonstrate that a large fraction of dissolved Al is in colloidal (≈50%) and organically complex (≈60%) forms in the Yalujiang. The observed scavenging from solution to particulate pools in the estuary is most likely through the flocculation of colloidal and organic-complexed Al, which results in a considerable change in dissolved-particulate partitioning, shown by laboratory mixing experiments. Exchange between dissolved and particulate phases is examined by analysis of Kd, the distribution coefficient. The empirical relationship of Kd with chlorinity and suspended matter concentrations was investigated with field observations and model simulations. The model indicated that Kd values of Al are inversely related to the amount of total suspended matter, but Kd-chlorinity plots show different features between dry and flood seasons. 相似文献
242.
The distribution of some trace metals (Cu, Zn, Ni, Co,Fe, Mn) and of DOC over a particulate (> 1 m),a colloidal (size < 0.45 m and molecular weight > 10 kD) and an ultrafiltered fraction (< 10 kD)was determined at several sites on the Thur River,Switzerland, at various times of the year. Thecomplexation of Cu by strong ligands in theultrafiltrate and in the conventional filtrate (<0.45 m) was compared using a ligand-exchange/CSV method.The <0.45 m concentrations of Cu (from anaverage of 7 nM to 24 nM), Zn (<5–23 nM), Ni (5–13 nM),Co (1.5–3 nM) and Mn (7–92 nM)increased downstream. The major part of Cu, Zn, Niand Co usually occurred in the ultrafiltratefraction at all sites, whereas Fe and Mn were mostlyin the particulate fraction, under conditions of lowsuspended matter content (< 10 mg L-1) in theriver. The percentage of metal in the colloidalfraction, with respect to the 0.45-m filtrate,decreased in the order: Cu (median 11%) > Zn Ni(median 5–6%) > Mn Co (median < 5%). DOCalso consisted mostly of molecules in the < 10 kDrange.Cu was strongly complexed by natural organic ligandsin all filtrate and ultrafiltrate samples. A largepart of the strong Cu binding ligands consisted ofcompounds in the < 10 kD range, but colloidalligands with similar properties also occurred. Cu wasdistributed among the dissolved and the colloidalligands, roughly in proportion to organic carbon.The colloidal fraction (as defined here) did notincrease in its proportional amount downstream and wasonly of limited significance in transporting traceelements in the Thur River under low discharge conditions. 相似文献
243.
利用与现今地面有关的数字地形资料,确定了内蒙古河套裂谷带北翼狼山-色尔腾山的剥蚀面序列及其分布型式。始新世末期始发的裂谷作用导致该裂谷北翼在渐新世(E3)、中新世(N1)、上新世(N2)和第四纪(Q)发生了4幕区域性地面隆起和剥蚀作用,与裂谷盆地的4幕沉降和沉积作用相关联。区域性地面降起量和剥蚀作用的时间长度、流水侵蚀对局部地势的潜在影响、隆起和侵蚀速度的相对重要性,以及构造、侵蚀和均衡作用的联合效应是该裂谷翼部景观发育的主要控制因素。 相似文献
244.
基于动力统计模型重构的副热带高压中长期预报 总被引:1,自引:0,他引:1
基于T106数值预报产品500 hPa位势高度场序列,用EOF方法对位势场序列进行时、空分解,在考虑相邻时段位势场空间模态基本稳定的前提下,引入动力系统重构的思想,以EOF分解的空间模态时间系数序列作为动力统计模型变量,用遗传算法全局搜索和并行计算优势,进行了模型参数的优化反演,建立了EOF分解的时间系数的非线性预报模型。通过模型积分和EOF的时、空重构,实现了副热带高压活动场的中长期预报。试验结果表明,在短期预报(1—5 d)该模型与T106模式的预报效果大致相当;但对于中长期预报(≥5 d),其预报效果优于T106预报产品;特别是10 d以上的预报结果对副热带高压的形态和范围仍然能较为准确地描述。该研究方法对副热带高压等复杂天气系统和要素场预报提供了一种新的思路。 相似文献
245.
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247.
Interdecadal variations in the frequency of typhoon affecting China (TAC) during 1951-2004 were investigated in this study. The yearly frequency of TACs showed a slightly increasing trend from the 1950s to the early 1970s and a significant decreasing trend afterwards. There were more TACs during the 1960s while the most inactive period was observed in recent 10 years. A decreasing trend was observed in the monthly frequency of TACs in June, August and September throughout the 54 years. Large interannual variabilities were apparent in yearly and monthly frequencies of TACs. 相似文献
248.
中国城市固体废弃物甲烷排放研究 总被引:2,自引:0,他引:2
The greenhouse effect of methane (CH4) is only inferior to that of carbon dioxide (CO2). As an important anthropogenic emission source, the calculation of the emission amount of CH4 from waste treatment in landfills plays an important role in compiling greenhouse gases inventory and in estimating the climate change effects caused by increasing of greenhouse gases. Based on the previous work, and according to the sampling and analysis on municipal solid waste (MSW) in typical cities, the degradable organic carbon (DOC) percentile was identified in typical cities in recent years. According to the IPCC greenhouse gases inventory guideline and default method of CH4 emission from MSW landfills, and in light of MSW managing situation in different regions, the amount of CH4 emission was calculated. The results show that the amount of CH4 emission decreases geographically from east to west and it increases temporally from 1994 to 2004 in China. 相似文献
249.
首先介绍了激光测距仪的发展历程,针对应用领域的不同,分别对3维激光成像仪和机载/星载激光测高仪的测量原理进行了阐述,并分别介绍了两种激光测距仪的工作流程以及数据处理流程,最后对两种激光测距仪的应用范围进行了阐述,并把两种激光测距技术和普通摄影测量进行了比较,指出了激光测距技术相对于普通摄影测量的优点,即高精度性、穿透性、实时性。 相似文献
250.
WANG Ren ZHU Xinhui 《地球空间信息科学学报》2007,10(1):57-60
In the field of converting simulation surveying and traditional close range photogrammetry, it has been developed so far to survey objects by commercial digital camera and this technique is applied widely in every part of production. In order to get three-dimensional information of objects, commercial digital camera must be examined. For a long time, digital camera has been examined by DLT. Then there must be a high-precision control field. For realizing surveying without control points, a method for self-calibration is proposed. 相似文献