南加州洛杉矶盆地北部S波分裂的观测结果

发生在洛杉矶盆地下面,深度为5—18 km 结晶基岩处的地震,在三分向地震图上,观测到了20—120 ms 的 S 波的分裂。发生在5 km 厚沉积层底部上述基岩中的浅震 S 波分裂现象不明显,而较深的地震 S 波分裂现象则随深度逐渐明显,快 S 波的偏振方向为南北方向,与地震和接收点之间射线的方位角无关。我们认为,S 波分裂主要发生在结晶基岩处,并且是由沿南北方向排列的地壳垂直微裂隙所引起的。假定微裂隙的这种排列又是由于地下应力状态造成的;由洛杉矶盆地北部下面 S 波分裂资料所得到的最大主应力方向为 N—S 向±15°,这与地质填图和断层面解的结果是一致的。射线追踪模拟表明,观测到的 S 波分裂,可通过含沿 N—S方向排列的垂直裂隙(裂隙密度约为0.04)的各向异性基岩解释,且其上覆盖着弱各向异性沉积岩层(裂隙密度小于0.02)。过去的4年中,在洛杉矶盆地发生了三次较大的地震,它们是1989年蒙特贝洛 M 4.6和 M4.4双震,1990年阿普兰 M5.5地震和谢拉马德 M5.8地震,他们距洛杉矶北部的 SCS 台站的震中距分别为10,55和40 km。在 SCS 台于阿普兰和谢拉马德地震前后,我们没有观测到 S 波分裂的明显变化。但是,在蒙特贝洛地震后,我们发现 S 波分裂的变化相当快;主震后分裂的 S波的分开时间从70 ms 迅速降至不到20 ms,然后,逐渐恢复到平均水平。S 波分裂时间的快速下降可能是一种时间变化,或者是蒙特贝洛地震位置的变化结果,因为蒙特贝洛地震近似地确定在预期的奇异线地点附近。     

顾功叙(ku kung-hsu)

地球物理学家,中国科学院地学部委员顾功叙先生,1908年7月5日出生在浙江省嘉善县,汉族。1929年于上海大同大学毕业后,任浙扛大学物理系助教。1934年赴美国留学,先后在科罗拉多州矿业学院和加利福尼亚理工学院学习及做研究工作,并获科罗拉多州矿业学院硕士学位。1938年回国后任前北平中央研究院物理研究所研究员。     

Development of macrofaunal communities on dredged material used for mudflat enhancement: a comparison of three beneficial use schemes after one year

In recent years, dredged material has become regarded as a potential resource and used to create and/or improve intertidal habitats ('beneficial use' schemes). This paper presents the results of a sampling programme to investigate the short-term macrofaunal recovery of three beneficial use schemes in south-east England in terms of species and functional diversity. Environmental parameters (sediment redox potential, and water, organic carbon and silt/clay contents) and univariate community attributes (total individuals and species, diversity, evenness and biomass) at the recharge sites had attained reference levels at two schemes while assemblages differed significantly in terms of species composition at all three schemes. While trophic group proportionality had re-established at one scheme, an increased grazer dominance was apparent at another while the proportion of sub-surface deposit feeders decreased at the third. Total individuals and species number of the developing communities were negatively correlated with sediment redox potential at 4 cm and % silt/clay, respectively. The implications of these results for monitoring the recovery of future fine-grained beneficial use schemes are discussed.     

Occurrence and accumulation features of polycyclic aromatic hydrocarbons and synthetic musk compounds in finless porpoises (Neophocaena phocaenoides) from Korean coastal waters

Reports of the occurrence and accumulation patterns of polycyclic aromatic hydrocarbons (PAHs) and synthetic musk compounds (SMCs) in marine mammals are scarce. In this study, the concentrations and accumulation profiles of PAHs and SMCs were determined in blubber from finless porpoises in Korean coastal waters. Total concentrations of PAHs and SMCs ranged from 6.0 to 432 (mean: 160) ng/g lipid weight and from 17 to 144 (mean: 52) ng/g lipid weight, respectively. Residue levels of PAHs were lower than those reported from other studies, while residue levels of SMCs were relatively higher than those reported in other studies. Naphthalene was the most abundant PAH and HHCB was the dominant SMC observed in finless porpoises. The concentrations of PAHs and SMCs were not correlated with each other, but were significantly correlated within the same chemical groups. No correlations were found between body size and residue levels of PAHs and SMCs.     

Accumulation of butyltin compounds in cetaceans from Korean coastal waters

Data on the occurrence and accumulation profiles of butyltins (BTs), including tributyltin (TBT), in marine mammals are scarce. This is the first study to investigate residue levels and accumulation patterns of BTs in cetaceans from Korean coastal waters. The total concentrations of BTs (sum of mono- to tri-butyltins) in minke whales (Balaenoptera acutorostrata) and long-beaked common dolphins (Delphinus capensis) ranged from 15.7 to 297 ng/g wet weight (mean: 100 ng/g wet weight) and from 59.0 to 412 ng/g wet weight (mean: 228 ng/g wet weight), respectively. Dibutyltin (DBT) accounted for 63% of the total BTs in all cetacean samples. Significant species-specific differences in BT concentrations, possibly due to the differences in their habitat and diet, were found between the two cetacean species. The concentrations of DBT and TBT in most cetacean samples exceeded the threshold value for cytotoxic effects in cetaceans, implying potentially adverse health risks from exposure to BTs.     

Immune responses to combined effect of hypoxia and high temperature in the green-lipped mussel Perna viridis

Flow cytometry was used to examine immune responses in haemocytes of the green-lipped mussel Perna viridis under six combinations of oxygen level (1.5 mg O2 l(-1), 6.0 mg O2 l(-1)) and temperature (20 °C, 25 °C and 30 °C) at 24 h, 48 h, 96 h and 168 h. The mussels were then transferred to normoxic condition (6.0 mg O2 l(-1)) at 20 °C for further 24 h to study their recovery from the combined hypoxic and temperature stress. Esterase (Est), reactive oxygen species (ROS), lysosome content (Lyso) and phagocytosis (Pha) were reduced at high temperatures, whereas hypoxia resulted in higher haemocyte mortality (HM) and reduced phagocytosis. For HM and Pha, changes were observed after being exposed to the stresses for 96 h, whereas only a 24 h period was required for ROS and Lyso, and a 48 h one for Est. Recovery from the stresses was observed for HM and Pha but not other immune responses.     

A photoautotrophic source for lycopane in marine water columns

Suspended particulate matter and recent sediments from diverse oceanic sites have been investigated for their contents of lycopane. Lycopane was present in all samples, including both oxic and anoxic water column and sediments. The highest concentrations in the water column were found in surface waters of the central Pacific gyre (1.5 ng/L) and in the anoxic waters of the Cariaco Trench (1.1 ng/L) and the Black Sea (0.3 ng/L). Vertical concentration profiles suggest that lycopane is probably algal in origin. Moreover, biogeochemical conditions in anoxic zones apparently result in a secondary production of lycopane from an as yet unidentified precursor. Compound-specific carbon isotopic analyses have been carried out on lycopane from water column and sediment samples. Isotopic compositions of lycopane range between -23.6% and -32.9% and are consistent with a photoautotrophic origin. We postulate that some lycopane is produced in surface waters of the ocean, while additional lycopane is produced in anoxic zones by anaerobic microbial action on an algal precursor.     

Effects of nitrogen and sulphide on macroinfaunal community: a microcosm study

A microcosm experiment was conducted to test the short-term effects of nitrogen (as TKN, total Kjeldahl nitrogen) and sulphide (as AVS, acid volatile sulphide) on macrobenthic infauna over a period of 8 weeks. The experiment consisted of four treatments using sediment cores (D: 8 cm, H: 20 cm) with addition of: I, nitrogen (N) to an in situ mean level of 0.48 mg Ng(-1) dw; II, sulphidic solution (S) to an in situ mean level of 318.8 microM S g(-1) dw; III, nitrogen and sulphidic solution (NS) to in situ mean levels of 0.45 mg Ng(-1) dw and 329.0 microM S g(-1) dw, respectively, and IV, control with no addition of N and S. Sediment cores were retrieved for analysis of infaunal composition after weeks 2, 4 and 8. A total of 646 specimens of macrobenthic infauna belonging to 27 species were recorded from the cores, in which polychaetes were the most abundant with respect to species and individual numbers. Mean species number and diversity H' of the control and N treatment was statistically higher than S and NS treatments, mean individual number of the S treatment was larger than the NS treatment, and mean evenness J of the S treatment was lower than the N and NS treatments as well as the control. Individual numbers also showed a significant increase from weeks 2 to 8, whereas evenness J decreased in weeks 4 and 8. Multivariate analyses of the faunal data suggested that benthic composition of the N treatment and control did not differ during the experimental period, but changes in benthic structure in S and NS treatments were evident. The present findings demonstrated the dose-response relationship of benthic species changes under controlled addition of N and S. The response to N and S additions in the sediment microcosms was in agreement with the general effects of organic enrichment on macrobenthic communities along a spatial gradient of organic pollution as described by Pearson and Rosenberg [Pearson, T.H., Rosenberg, R., 1978. Macrobenthic succession in relation to organic enrichment and pollution of the marine environment. Oceanography and Marine Biology Annual Review 16, 229-311]. However, in the present experiment, community changes in the treatments were observable in a short, temporal scale.