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201.
Excitation-emission matrix spectroscopy (EEMS) was used to characterize the ultra violet fluorescence fingerprints of eight crude oils (with a 14,470-fold range of dynamic viscosity) in seawater. When the chemical dispersant Corexit 9500 was mixed with the oils prior to their dispersion in seawater, the fingerprints of each oil changed primarily as an increase in fluorescence over an emission band centered on 445 nm. In order to simplify the wealth of information available in the excitation-emission matrix spectra (EEMs), two ratios were calculated. A 66-90% decrease in the slope ratio was observed with the addition of Corexit. When the slope ratios were reduced in complexity to intensity ratios, similar trends were apparent. As a result either of the ratios could be used as a simple and rapid means of identifying and monitoring chemically dispersed oil in the open ocean. 相似文献
202.
Dhong-il Lim Seung Woon Jung Man Sik Choi Sun Mee Kang Hoi Soo Jung Jin Yong Choi 《Marine pollution bulletin》2013
Concentrations of heavy metals and Pb isotopes were measured in the 1-M HCl leaching fraction of core sediments spanning the last 400 years. This sedimentary record of pollution history in metal concentrations shows a good correlation with the increases in industrialization, urbanization, and energy consumption since 1901s. Notably, the Pb concentration and the 207Pb/206Pb and 208Pb/206Pb ratios were constant before the 1910s (16.7 μg/g, 0.844, and 2.098, respectively), whereas they increased steadily up to 21.9 μg/g, 0.848, and 2.101 after the 1910s. The correlations between Pb isotope ratios (206Pb, 207Pb, and 208Pb) showed different linear regression trends for core sediments before and after the 1910s, indicating differences in Pb sources. Our interpretation suggests that the source of anthropogenic Pb in Korean coastal region and the Yellow Sea shelf was presumed to be Chinese coals or ores, which have also played a major role as sources of atmospheric particulate Pb. 相似文献
203.
Local geology or local site effect is a crucial component while conducting seismic risk assessment studies. Investigations made by utilization of ambient noise are an effective tool for local site estimation. The present study is conducted to perform site response analysis at 13 different sites within urban settlements of Fateh jang area(Pakistan). The aim of this study was achieved by utilizing Nakamura method or H/V spectral ratio method. Some important local site parameters, e.g., the fundamental frequencies f0 of soft sediments, amplitudes A0 of corresponding H/V spectral ratios, and alluvium thicknesses over 13 sites within the study area, were measured and analyzed. The results show that the study area reflects low fundamental frequency f0. The fundamental frequencies of the sediments are highly variable and lie in a range of 0.6–13.0 Hz. Similarly, amplification factors at these sites are in the range of 2.0–4.0. 相似文献
204.
从Global CMT目录搜集了1976年1月至2016年6月之间的震源深度大于70 km的255个震源机制解,用阻尼应力反演方法,分70~160 km和170~310 km两个深度,计算了帕米尔-兴都库什地区的构造应力场;同时以10 km为间隔计算了兴都库什地区深度介于70~310 km之间的应力形因子.得到以下初步结论:兴都库什板片向下俯冲和帕米尔地区断裂带的横向拉张,可能是导致应力场不同的原因.兴都库什俯冲带与帕米尔俯冲带碰撞,导致交汇地区(37°N-37.5°N)的应力场参数突变.兴都库什俯冲板片受到深部温度、压力等因素,出现薄弱面进而形成拆离板片.其脱离了主俯冲板片的束缚后,重力的上下拉张作用导致空区附近张轴倾伏角接近90°,拆离板片俯冲至上地幔不连续面,导致板片部分熔融进而应力形因子随着深度变小.而拆离板片受到地幔挤压其内部发生破碎,其压应力轴由西部的NS到东部NW-SE方向偏转及纵向张应力轴倾伏角变小.
相似文献205.
The herbicides atrazine, simazine and terbuthylazine (and the degradation product deethylatrazine) were analysed in two river-to-open-sea transects and two vertical (open-sea) profiles in the southern Baltic off Poland. Samples taken in September 1995 and April 1997 contained total triazine concentrations ranging from 7 to 31 and 4.5 to 13 ng/dm3, respectively. Concentrations of the individual compounds ranged from 0 to 8 ng/dm3. These are generally higher than levels reported, for example, in the North Sea. The largest surface concentrations were found close to the Vistula and Odra river mouths, endorsing river run-off as a primary source of the triazines. Temporal variability can be related to the late-spring and early-summer agricultural applications of the compounds. Variations in ratios between the individual triazines can be explained by usage patterns and differing residence times. Offshore vertical profiles indicate enrichment of the surface layer through atmospheric triazines inputs, highest concentrations above the halocline associated with colloidal organics and lowest concentrations in the bottom waters, probably as a result of particulate scavenging. The influence of the North Sea inflow to the Baltic is also discussed. 相似文献
206.
Wang Guoan Han Jiamao Zhou Liping Xiong Xiaogang Tan Ming Wu Zhenhai Peng Jun 《中国科学D辑(英文版)》2006,49(1):97-102
Carbon isotope ratios (δ
13C) of 89 C4 plant samples were determined from the loess area in North China. δ
13C values vary between −10.5‰ and −14.6‰ with a mean of −12.6‰. Along a precipitation gradient from the semi-moist area to
the semiarid area, then to the arid area, the δ
13C values of C4 plants show a slight decreasing trend. The δ
13C values of C4 plants in the dry season are found lower than those in the wet season. These trends are opposite to those observed for C3 species. 相似文献
207.
208.
《Marine pollution bulletin》2014,81(1-2):52-58
The contamination of surface sediments in Guan River Estuary, China, by polycyclic aromatic hydrocarbons (PAHs) has been fully investigated. Total concentrations of 21 PAHs ranged from 90 to 218 ng/g with an average of 132.7 ng/g, which is relatively low in comparison with other estuaries around the world. PAH concentrations appeared to be positively correlated with clay content and negatively correlated with sediment grain size. Source identification implied that the PAHs originated mainly from pyrolytic sources. However, source patterns may be continuously changed to a petrogenic origin due to the heavy ship traffic and continuous discharge of oily sewage in this area. The PAH levels were also compared with international Sediments Quality Guidelines and Sediments Quality Criteria, and the results indicated low negative effects for most individual PAHs. However, toxic effects related to FLO would occur occasionally in most locations in the estuary. 相似文献
209.
210.
传统等效线性化波动法主要的缺陷之一,是当基岩输入地震动较强时,高频段算得的频响放大倍率比实际场地的实测结果明显偏低.该缺陷可能导致低估重大工程的设计地震动参数的严重后果,因而是亟待解决的重要问题.本文认为,现行基于土的剪切模量和阻尼比的频率相关性修正等效剪应变的做法有其合理性,但不便应用并可能具有较大的不确定性;由于震级可以影响地震动的频谱特征,通过震级调整等效剪应变的做法也可视为按照频率调整等效剪应变.由于距离与震级一样也可以影响地震动的频谱特征,本文提出通过震级M和距离R参数修正等效线性化的方法EQLM(M,R),并用算例说明,等效线性化方法的上述缺陷可以通过本文提出的EQLM(M,R)方法得到一定程度的改善. 相似文献