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601.
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Trophic Assessment in Chinese coastal systems-review of methods and application to the Changjiang (Yangtze) Estuary and Jiaozhou Bay 总被引:3,自引:0,他引:3
Yongjin Xiao João G. Ferreira Suzanne B. Bricker João P. Nunes Mingyuan Zhu Xuelei Zhang 《Estuaries and Coasts》2007,30(6):901-918
Coastal eutrophication has become one of the main threats to Chinese coastal areas during the last two decades. High nutrient
loads from human activities have modified the natural background water quality in coastal water bodies, resulting in a range
of undesirable effects. There is a need to assess the eutrophic level in coastal systems and to identify the extent of this
impact to guide development of appropriate management efforts. Traditional Chinese assessment methods are discussed and compared
with other currently-used methods, such as the Oslo-Paris Convention for the Protection of the North Sea (OSPAR) Comprehensive
Procedure and Assessment of Estuarine Trophic Status (ASSETS). The ASSETS method and two Chinese methods were tested on two
Chinese systems: the Changjiang (Yangtze) Estuary and Jiaozhou Bay. ASSETS is process based, and uses a pressure-state-response
model based on three main indices: Influencing Factors, Overall Eutrophic Condition, and Future Outlook. The traditional methods
are based on a nutrient index. ASSETS was successfully applied to both systems, classifying the Changjiang Estuary as Bad
(high eutrophication) and Jiaozhou Bay as High (low eutrophication). The traditional methods led to ambiguous results, particularly
for Jiaozhou Bay, due to the high spatial variability of data and a failure to assess the role of shellfish aquaculture in
nutrient control. An overview of the Chinese coastal zone identifies 50 estuaries and bays that should form part of a national
assessment. A comparison of methods and results suggests that ASSETS is a promising tool for evaluating the eutrophication
status of these systems. 相似文献
604.
Tao Li Zhe Zhu Dongsheng Wang Chonghua Yao Hongxiao Tang 《International Journal of Mineral Processing》2007
Flocs generated by various shear forces exhibit different characteristics of size, strength and structure. These properties were investigated by employing a continuous optical monitoring and a microscope with CCD camera to directly monitor aggregation under six different shear intensities. The floc structure was characterized by the fractal dimension. The results showed that the flocculation index (FI) decreased from 1.16 at 20 rpm to 0.25 at 250 rpm and the floc size decreased from 550 μm to 150 μm, meantime, the FI value showed a good correlation with floc size. In order to determine the floc strength, two methods were used. One was the strength factor, ranging from 18.3% to 62.5%, calculated from FI curve, and the other was a theoretical value between 0.005 N/m2 and 0.240 N/m2, estimated by calculation. The floc strength increased with the G value in both cases. Furthermore, the fractal dimension increased with G and its value was between 1.30 and 1.63. The relation between fractal dimension and strength was also obtained. 相似文献
605.
606.
根据显微镜观察,塔里木盆地砂岩储层中SiO2溶蚀分为石英颗粒边缘溶蚀、次生加大边溶蚀和交代溶蚀。通过对石英颗粒和加大边溶蚀特征及其与粘土矿物组合、与碳酸盐胶结、与古油藏破坏以及现今油田水中Si离子含量等关系的综合研究,这些SiO2溶蚀可能存在两种机理:碱性环境下的SiO2溶蚀和有机酸(烃类微生物降解产生的有机酸以及有机质成熟产生的有机酸)引起的SiO2溶蚀。第一种溶蚀类型较普遍,但程度微弱;第二种溶蚀类型主要发生在古油藏破坏和有机质成熟过程中,这种溶蚀较强烈但很局限。SiO2的溶蚀作用可以为油气提供一定量的储集空间,这对于深埋的时代较老的志留-泥盆系储层具有重要意义。在古油藏中尽管烃类已经充注储层孔隙,但只要孔隙中存在有机酸或碱性孔隙水,SiO2的溶蚀和石英次生加大的胶结等作用仍可进行。 相似文献
607.
608.
GDX-502树脂富集高效液相色谱法测定地表水中酚类化合物 总被引:2,自引:2,他引:2
采用自制GDX-502固相萃取小柱萃取水中苯酚、对硝基酚、间甲酚、2,4-二氯酚、2,4,6-三氯酚、五氯酚等6种酚类化合物,以乙腈作为洗脱剂,选择280nm和290nm双波长紫外高效液相色谱进行检测。结果表明,方法检出限为0.01-0.05mg/L,IL水的平均加标回收率为82.5%-95.0%,精密度(RSD,n=7)为3.6%-9.2%。方法用于实际地表水中痕量酚类化合物的检测,操作简单,有机溶剂用量少,分析效率高;萃取小柱可多次重复使用,分析成本低。 相似文献
609.
长河煤矿为地质构造中等复杂区,其矿区地质及水文地质条件表明,地表水、直接充水含水层煤系砂岩裂隙水、老窑水、构造断裂带水都可构成该矿井开采的充水因素,且其涌水量大小与大气降水关系密切。针对矿井开采的具体情况提出了一系列的防治措施,并取得了良好的效果,对煤矿水害的防治有一定的指导意义。 相似文献
610.
Synthetic aperture radar (SAR) image formation for a ground moving target necessitates the compensation of the unknown target trajectory. The keystone transform has been employed to remove the linear component of the range migration for the moving target, where interpolation is required. In this letter, a realization of the keystone transform avoiding interpolation is presented. The kernel of this transform, i.e., the range-frequency-dependent azimuth time rescaling, is implemented using only complex multiplications and fast Fourier transforms based on the scaling principle, which has been successfully applied in the equalization of the space-variant range cell migration in SAR processing. In addition, the moving target is coarsely focused according to the SAR geometry and the platform velocity while exploiting the scaling principle. This preliminary focusing is helpful in the isolation of the moving target from ground clutter, so as to facilitate a more refined processing with respect to each mover. SAR raw data combined with simulated echoes of moving targets are utilized to validate the presented approach 相似文献