Isomer specific determination of hexabromocyclododecanes (HBCDs) in small cetaceans from the South China Sea--Levels and temporal variation   总被引：1，自引：0，他引：1  

Isobe T  Ramu K  Kajiwara N  Takahashi S  Lam PK  Jefferson TA  Zhou K  Tanabe S 《Marine pollution bulletin》2007,54(8):1139-1145

A diastereoisomer (alpha, beta, and gamma) specific analytical method for measuring hexabromocyclododecanes (HBCDs) was developed using liquid chromatography-tandem mass spectrometry (LC-MS-MS). The method developed was applied to analyze blubber of small cetaceans to divulge the distribution and temporal variation of HBCDs in the Asian marine environment. HBCDs were detected in all the blubber samples of finless porpoises (Neophocaena phocaenoides) and Indo-Pacific humpback dolphins (Sousa chinensis) collected from the South China Sea during 1990-2001. Concentrations of HBCDs were higher in humpback dolphins (31-380 ng/g lipid) than in finless porpoises (4.7-55 ng/g lipid), which can be attributed to habitat differences. Average concentrations of alpha-HBCD in finless porpoises increased from 9.5 ng/g lipid in 1990 to 35 ng/g lipid in 2000/01. alpha-HBCD was predominant among the three isomers with some exceptions in finless porpoises collected in 1990. This is the first report on HBCDs contamination in marine mammals from Southeast Asia.  相似文献   

The occurrence of selected antibiotics in Hong Kong coastal waters   总被引：4，自引：0，他引：4  

Gulkowska A  He Y  So MK  Yeung LW  Leung HW  Giesy JP  Lam PK  Martin M  Richardson BJ 《Marine pollution bulletin》2007,54(8):1287-1293

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Predicting support of climate policies by using a protection motivation model     

San-Pui Lam 《Climate Policy》2013,13(3):321-338

Taiwan aims to reduce its estimated 2020 CO₂ emissions by 45%. Attaining this goal will require strong policies and public support. In this study, a psychological model was tested to predict how Taiwanese citizens would support ten policies that mitigate or adapt to climate change. The model is an expansion of Protection Motivation Theory (PMT [Rogers, R. W. (1983). Cognitive and physiological processes in fear-based attitude change: A revised theory of protection motivation. In J. Cacioppo & R. Petty (Eds.), Social psychophysiology: A sourcebook (pp. 153–176). New York, NY: Guilford]) involving responsibility and the subjective effectiveness of alternative solutions (SEAS) as additional variables. Data were collected after conducting two surveys in Taiwan that involved a total of 394 respondents. The results indicated that perceived responsibility and SEAS predicted the support of only one to three of the policies. Regarding the PMT variables, severity and vulnerability did not affect the support of almost all policies. Policy support was primarily affected by the other three PMT variables: self-efficacy, response efficacy, and relative benefit. These three variables significantly affected most policies, accounting for 34–73% of the variance in public support. This suggests that PMT facilitates understanding of public support for climate policies.  相似文献   

Experimental Investigation of the Decay from A Ship’s Propeller   总被引：1，自引：0，他引：1  

宋永臣 《中国海洋工程》2011,25(2):265-284

In the present study,an experimental investigation of the decay of the maximum velocity and its turbulent characteristics behind a ship propeller,in "bollard pull" condition(zero speed of advance),is reported.Velocity measurements were performed in laboratory by use of a Laser Doppler Anemometry(LDA) measurement system.Earlier researchers described that the maximum axial velocity is constant at the initial stage of a ship’s propeller jet(Fuehrer and Rmisch,1977;Blaauw and van de Kaa,1978;Berger et al.,1981;Verhey,1983) as reported in a pure water jet(Albertson et al.,1950;Lee et al.,2002;Dai,2005),but a number of researchers disagreed with the constant velocity assumption.The present study found that the maximum axial velocity decays in the zone of flow establishment and the zone of established flow with different rates.The investigation provides an insight into the decays of both the maximum velocity and the maximum turbulent fluctuation in axial,tangential and radial components and the decay of the maximum turbulent kinetic energy.Empirical equations are proposed to allow coastal engineers to estimate the jet characteristics from a ship’s propeller.  相似文献   

Changes in the nutrient ratios and phytoplankton community after declines in nutrient concentrations in a semi-enclosed bay in Hong Kong     

Lie AA  Wong CK  Lam JY  Liu JH  Yung YK 《Marine environmental research》2011,71(3):178-188

Tolo Harbour is a landlocked bay with poor tidal flushings in the northeastern part of Hong Kong. During the 1980s, excessive nutrient loading led to dramatic increase in nutrient concentrations, accompanied by lower N:P ratios, higher algal biomass and shifts in the phytoplankton community. We studied the effects of nutrient loading reduction measures on nutrient concentrations, nutrient ratios and phytoplankton dynamics in Tolo Harbour by comparing data collected before the full implementation of nutrient loading reduction measures (1986-1997) to those after the implementation (1998-2008). Such measures led to declines in nutrient concentrations, changes in N:P and N:Si ratios, lower chlorophyll-a concentrations and fewer algal blooms. Diatoms were the most abundant phytoplankton group in Tolo Harbour both before and after declines in nutrient concentrations. The density of dinoflagellates did not change, but substantial increase in other algal group abundance was recorded.  相似文献   

Comparison of two sampling methods when studying periphyton colonization in Lam Tsuen River, Hong Kong, China     

�װ�ƽ  ��Ⱥ��  ������ 《中国海洋湖沼学报》2011,29(1):141-149

We used standard periphyton samplers to examine the colonization pattern of periphytic algae on artificial substrates (glass slides) in Lam Tsuen River, Hong Kong, in dry (winter) and wet (summer) seasons. In each season, six replicated slides were retrieved randomly and replaced by new slides at weekly intervals over a period of 6 weeks. We thus obtained two batches of slides, both with a series of different exposure times (1 to 6 weeks): one batch was set up at the same time (start of the sampling) and the other was harvested at the same time (end of the sampling). Changes in taxonomic composition, species diversity (Shannon-Wiener diversity index), standing crop (in terms of cell density and cell biovolume), and abundance of the abundant algal species were monitored and compared between the two batches of slides. The succession patterns of the periphytic algae were similar between the two batches in each season, while more remarkable differences were observed between the two seasons, suggesting that either batch would be suitable for a colonization study of periphytic algae. The cell density was dominated by diatoms in both seasons, while the cell biovolume was dominated by diatoms in winter and by green algae in summer. The cell density and biovolume attributed to blue green algae was relatively small. Most of the diatom species exhibited similar colonization patterns throughout the experiment, while green algae showed different succession patterns in different seasons or sampling methods, indicating that diatoms are better bio-indicators than green algae for a periphyton colonization study. In general, the diversity indices and the standing crops reached their maximums at around week 4, and they were higher in summer than in winter.  相似文献   

Analysis of factors controlling soil N2O emission by principal component and path analysis method     

Can Chen  Deli Chen  Jianjun Pan  Shu Kee Lam 《Environmental Earth Sciences》2014,72(5):1511-1517

Nitrous oxide (N₂O) is a potent greenhouse gas. Mitigating N₂O emission is critical for combating global climate change and improving the ecological environment. Many studies have focused on factors affecting N₂O emission from agricultural soils, but rarely on the relationship among these factors. In the present study, continuous measurement on N₂O emission was conducted in a maize system in Griffith, Australia and the relationships between N₂O emission, soil properties and weather conditions were examined. Principal component analysis and path analysis were used to analyze these data in correlation coefficient and the direct and indirect effects to N₂O emission. Results indicated that (1) the major factors affecting N₂O emission were WFPS, mineralized nitrogen (Mineral N), daily mean temperature (T _mean) and CO₂ concentration. The factors of direct influence N₂O emission were following Mineral N, CO₂, WFPS, and T _mean. The indirect influence N₂O emission was following T _mean, WFPS, Mineral N, and CO₂ concentration. (2) The standard multiple regression describing the relationship between N₂O emission and its major factors were Y = ?37.162 + 0.5267 X ₁ + 0.4331 X ₂ + 0.3014 X ₃ + 0.2392 X ₄ (r = 0.924, p < 0.01, n = 151), where Y is N₂O emission, X ₁ is Mineral N, X ₂ is CO₂, X ₃ is WFPS and X ₄ is T _mean. (3) N₂O emission from agricultural soils can be monitored and mitigated through improved management practices such as irrigation, straw retention and fertilizer application.  相似文献   

Fixing the wheel the carpetbaggers broke     

Martin M  Lam PK  Richardson BJ 《Marine pollution bulletin》2003,46(7):918-920

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Exposure and time dependent DNA strand breakage in hepatopancreas of green-lipped mussels (Perna viridis) exposed to Aroclor 1254, and mixtures of B[a]P and Aroclor 1254     

Siu WH  Hung CL  Wong HL  Richardson BJ  Lam PK 《Marine pollution bulletin》2003,46(10):1285-1293

Green-lipped mussels (Perna viridis) were exposed to Aroclor 1254 (0.5, 5 and 50 microgl(-1)) and a mixture of benzo[a]pyrene (B[a]P) and Aroclor 1254 (0.3+0.5 and 3+5 microgl(-1)) for 12 days. On day 0, 1, 3, 6 and 12, the levels of DNA strand breaks in the mussel hepatopancreas were monitored using an alkaline unwinding assay. The results were compared to the findings of a previous study in which the levels of DNA strand breakage in the same species were measured following exposure to various concentrations of B[a]P (0.3, 3 and 30 microgl(-1)). The results indicated that Aroclor 1254 at a concentration 相似文献   

A fast algorithm for finding K shortest paths using generalized spur path reuse technique     

Bi Yu Chen  Xiao‐Wei Chen  Hui‐Ping Chen  William H. K. Lam 《Transactions in GIS》2021,25(1):516-533

The problem of finding the K shortest paths (KSPs) between a pair of nodes in a road network is an important network optimization problem with broad applications. Yen's algorithm is a classical algorithm for exactly solving the KSP problem. However, it requires numerous shortest path searches, which can be computationally intensive for real large networks. This study proposes a fast algorithm by introducing a generalized spur path reuse technique. Using this technique, shortest paths calculated during the KSP finding process are stored. Accordingly, many shortest path searches can be avoided by reusing these stored paths. The results of computational experiments on several large‐scale road networks show that the introduced generalized spur path reuse technique can avoid more than 98% of shortest path searches in the KSP finding process. The proposed algorithm speeds up Yen's algorithm by up to 98.7 times in experimental networks.  相似文献