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721.
Jing‐Wen Zhang Yu‐Kun Wang Hai‐Ying Du Xin Du Jing‐Jun Ma Jing‐Ci Li 《洁净——土壤、空气、水》2011,39(12):1095-1098
A new method for determining lead (Pb) content was developed by dispersive liquid–liquid microextraction based on the solidification of floating organic droplets followed by flame atomic absorption spectrometry. Under optimum conditions, the calibration graph was linear within the Pb content range of 8.43–400 µg L?1 with a detection limit of 2.53 µg L?1. The relative standard deviation for 10 replicate measurements of 20 and 400 µg L?1 of Pb were 3.41 and 2.78%, respectively. The proposed method was assessed through the analysis of certified reference water and recovery experiments. 相似文献
722.
通过实例研讨了高层建筑物的沉降观测。对水准点、沉降观测点的布设及沉降观测的资料整理进行了论述,谈了一些变形测量的体会。 相似文献
723.
Christopher J. Garden Dave Craw Jonathan M. Waters Abigail Smith 《Estuarine, Coastal and Shelf Science》2011
Tracking and quantifying biological dispersal presents a major challenge in marine systems. Most existing methods for measuring dispersal are limited by poor resolution and/or high cost. Here we use geological data to quantify the frequency of long-distance dispersal in detached bull-kelp (Phaeophyceae: Durvillaea) in southern New Zealand. Geological resolution in this region is enhanced by the presence of a number of distinct and readily-identifiable geological terranes. We sampled 13,815 beach-cast bull-kelp plants across 130 km of coastline. Rocks were found attached to 2639 of the rafted plants, and were assigned to specific geological terranes (source regions) to quantify dispersal frequencies and distances. Although the majority of kelp-associated rock specimens were found to be locally-derived, a substantial number (4%) showed clear geological evidence of long-distance dispersal, several having travelled over 200 km from their original source regions. The proportion of local versus foreign clasts varied considerably between regions. While short-range dispersal clearly predominates, long-distance travel of detached bull-kelp plants is shown to be a common and ongoing process that has potential to connect isolated coastal populations. Geological analyses represent a cost-effective and powerful method for assigning large numbers of drifted macroalgae to their original source regions. 相似文献
724.
Mucus films, flocs or foams consisting of fine sand, algae and detritus frequently occur in the surface waters of rocky intertidal reef flats during incoming tide. These masses are referred to as mucus aggregates. We examined the developmental process of mucus aggregates and their abundance, distribution, migration and trophic composition. The trophic composition of mucus aggregates was then compared to those of sediments to evaluate their potential nutritional value for benthic animals. The organic matter content, chlorophyll a concentration, microalgal density and bacteria-derived fatty acid contents of mucus aggregates were higher than those observed in sediment, suggesting that mucus aggregates contain not only high levels of organic matter but also dense concentrations of microalgae and bacteria; therefore, mucus aggregates may serve as a qualitatively more energetic food source for benthic fauna compared to sediments. Benthic diatoms were the most abundant organisms in mucus aggregates. Large numbers of diatoms were trapped in fine mineral particles and mucilage-like strings, suggesting that a portion of the mucus is secreted by these benthic microalgae.Mucus aggregate accounted for only 0.01-3.9% of the daily feeding requirements of the dominant detritivore, Ophiocoma scolopendrina (Echinodermata: Ophiuroidea) over the entire sampling area. In contrast, for the species population on the back reef, where mucus aggregates ultimately accumulate, mucus aggregates provided from 0.4 to 113.3% of food for this species. These results suggest that mucus aggregate availability varies spatiotemporally and that they do not always provide adequate food sources for O. scolopendrina populations. 相似文献
725.
Water waves induce a slow drift of an object floating on the water surface. In this study, we examined, by a series of laboratory experiments, the drift motion of small rigid floating objects driven by regular waves in deep water. Different shapes of planar objects, including square, circular and elliptical, were investigated for two different submergences, and their drift motions in waves were determined using an infrared motion monitoring system. The corresponding measurements enabled the quantification of the drift characteristics with respect to the wave characteristics and object shapes. Numerical simulations based on an existing theory were presented and comparisons between the experimental data and the predictions by the existing theory were performed. 相似文献
726.
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728.
平均海面存在趋势性变化,对于四维大地测量定位而言,必须赋予高程基准以时间特征,本文认为最好是确定高程基准历元。文章提出了高程基准历元的定义,给出了计算公式,求得中国1985国家高程基准历元为1966.0。文章还讨论了平均海面趋势性变化的数学问题,及提出了高程基准归化至统一状态的概念,研究了由于海水密度不同引起的平均海面高度变化,计算得中国1985国家高程基准对于通常海水状态的修正值为-0.012m 相似文献
729.
作为人造工程的三峡水库的建立,使得库区水体聚集,地球质量重新分布,将使地壳的物理结构以及局部地球重力场发生变化.针对上述问题,对库区的水准面、点绝对重力值、垂线方向和高程、高程基准面等的重力场变化以及地壳形变进行了研究.主要结果是:当蓄水水位达到峰值175m(坝高)时,大地水准面有2.23-11.2mm的变化,点重力值有(0.83-4.6)×10-5ms-2的变化,垂线偏差的变化分别为-0.62"-6.50"(南北方向)和-6.42"-1.34"(东西方向)地壳的形变量为1.32-6.65mm,这些变化将引起测区的高程产生3.55-17.84mm的变化.因此,原有库区及其附近的测量资料(包括水准、天文、重力等)必须审慎使用,并应建立库区形变监测网,对地壳形变、地震、滑坡、大坝变形等进行监测. 相似文献
730.
Relative sea level change can be derived from tide records. In order to study the general sea level change along the coast of China, it is necessary to make a unified reduction for all the results obtained from various tide stations. A so-called isostatic datum of vertical movement of thecoastal land hasbeen suggested as a basis of the unified reduction in this paper, established by useof precise releveling data completed between 50's and 80's.The vertical movement velocities relative 相似文献