Uptake and depuration of PAHs and chlorinated pesticides by semi-permeable membrane devices (SPMDs) and green-lipped mussels (Perna viridis)     

Bruce J. Richardson  Edmund S.-C. Tse  Sharon B. De Luca-Abbott  Michael Martin  Paul K.S. Lam 《Marine pollution bulletin》2005,51(8-12):975

Semi-batch seawater experiments were conducted to follow the uptake and release of selected PAHs (anthracene, fluorathene, pyrene and B[a]P) and organochlorine pesticides (α-HCH, aldrin, dieldrin, p,p′-DDT) in semi-permeable membrane devices (SPMDs) and green-lipped mussels (Perna viridis). Mathematical models were applied to describe the uptake and elimination curves of the contaminants for SPMDs, and kinetic parameters, such as uptake rate constants, and equilibrium triolein/water partitioning coefficients were calculated. SPMD data showed a good fit to estimate rate constant and partition coefficient equations, but only those contaminants which partitioned mainly in the dissolved phase (α-HCH and dieldrin) were well explained for mussels. Poor conformity of the other contaminants indicated mussels uptake by routes other than diffusion, such as ingestion of algae. An apparent equilibrium state was only noted for α-HCH in mussels. Aldrin was not detected in mussels in the first few days of exposure, indicating potential metabolism of this compound. B[a]P was not detected in the triolein of SPMDs, which suggests that the membrane may act as a reservoir. Loss of spiked B[a]P from the triolein was evident in a depuration experiment, which may indicate transfer to the membrane. Rate constants for mussels were higher than those for SPMDs, but the reverse was true for partition coefficients. Overall, mussels and SPMDs had similar uptake rates for all compounds in this study, excluding p,p′-DDT and dieldrin. Contaminant elimination took place more rapidly in mussels, implying that SPMDs are better candidates for detecting episodic discharge of organic contaminants.  相似文献   

Peak displacement demand of small to moderate magnitude earthquakes in stable continental regions     

Nelson Lam  Adrian Chandler 《地震工程与结构动力学》2005,34(9):1047-1072

A theoretical fault‐slip model has been developed for predicting the notional peak displacement demand (PDD) of earthquakes based on a limiting natural period of 5 s, for application in stable continental regions (SCRs). The developed theoretical expression is simple and robust. Importantly, it envelops predictions arising from a number of existing empirical and seismological (stochastic) models included in the comparison. The notional PDD prediction has been made initially for hard rock crustal conditions and at a reference source–site distance of 30 km. Factors have accordingly been introduced to correct for different distances and geological conditions in completing the PDD prediction model. Assuming displacement‐controlled behaviour, the predicted notional PDD may be compared with the displacement capacity of a structure, or component, for purposes of seismic stability assessment. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Shear wave velocity modelling in crustal rock for seismic hazard analysis   总被引：2，自引：1，他引：2  

A.M. Chandler  N.T.K. Lam  H.H. Tsang 《Soil Dynamics and Earthquake Engineering》2005,25(2):167-185

P-wave velocity data along with the thickness of sedimentary and crystalline layers within bedrock were collected from all global regions and presented in the Global Crustal Model CRUST2.0, published in 2001. This well-organised database provides invaluable potential contributions towards future seismic hazard modelling, particularly for stable continental regions (SCRs), where there is a scarcity of representative strong motion records for conventional modelling purposes. The P-wave velocity information presented in CRUST2.0 has been converted herein to S-wave velocity information. The latter is especially important for purposes of seismic hazard modelling. The value of the CRUST2.0 model has therefore been greatly enhanced by the important findings presented and further developed in this paper. By making the best use of available information on crustal conditions, the amplification behaviour of seismic waves affecting a region, an area or a site for any given earthquake scenario may be predicted. The developed methodology, which is intended for worldwide applications, has been illustrated by case studies in which model S-wave velocity profiles were developed for different geological regions within North America. The model profiles were found to be in excellent agreement with field measurements reported for each respective region.  相似文献   

Photodegradation of the pharmaceuticals atorvastatin, carbamazepine, levofloxacin, and sulfamethoxazole in natural waters     

Monica W. Lam  Scott A. Mabury 《Aquatic Sciences - Research Across Boundaries》2005,67(2):177-188

  相似文献   

Estimating non‐linear site response by single period approximation     

Hing‐Ho Tsang  Adrian M. Chandler  Nelson T. K. Lam 《地震工程与结构动力学》2006,35(9):1053-1076

Site effects characterize the filtering mechanisms within the soil sedimentary layers overlying bedrock. In regions of high seismicity such as California where strong motion records are relatively abundant, site coefficients can be developed by regression of recorded ground shaking parameters. In regions of low‐to‐moderate seismicity or of high seismicity but with a paucity of recorded strong motion data, such empirical models cannot be obtained in the same way. This study describes the theoretical development of a simple, rational manual procedure to calculate site coefficients, based on a single period approximation (SPA), and to construct displacement response spectra (RSD) for soil sites. The proposed simplified model, which takes into account the non‐linear behaviour of soil that is dependent on the level of shaking, impedance contrast at the soil–bedrock interface and the plasticity of soil material, has been verified by comparison with results obtained from non‐linear shear wave analyses and data recorded during the 1994 Northridge earthquake. The proposed model is believed to be a convenient tool for calculating non‐linear site responses and constructing site‐specific response spectra, which has the potential of being incorporated into code provisions. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Terrestrial heat flow and geothermal gradients in relation to hydrodynamics in the Alberta basin, Canada     

J. A. Majorowicz  F. W. Jones  H. L. Lam  A. M. Jessop 《Journal of Geodynamics》1985,4(1-4)

Geothermal gradients in the Alberta part of the Western Canadian sedimentary basin have been studied on the basis of 55,244 bottom-hole temperature values from 28,260 petroleum exploration wells. Gradient estimates for different depth and stratigraphic intervals together with a study of the heat conductivity distribution indicate both regional heat flow variations and variations with depth. The regional hydrodynamics of the basin strongl influences both grad ifT gradient and heat flow increase with depth in water recharge areas to the west and decrease with depth in discharge areas to the north and east. The results indicate that heat flow in the central part of the basin should be approximately equal to the deep crustal heat flow.  相似文献   

Response spectrum predictions for potential near-field and far-field earthquakes affecting Hong Kong: rock sites   总被引：1，自引：0，他引：1  

N. T. K. Lam  A. M. Chandler  J. L. Wilson  G. L. Hutchinson 《Soil Dynamics and Earthquake Engineering》2002,22(1)

To realistically assess the seismic risk relating to built infrastructures in Hong Kong and in the neighbouring coastal cities of southern Guangdong province, it is necessary to predict ground shaking induced by different earthquake scenarios with good accuracy. A companion paper has described the modelling of the spatial and temporal distribution of the diffused seismic activities in the region, based on the newly-developed ‘Expanding Circular Disc’ (ECD) method. Representative Magnitude–Distance (M–R) combinations for both near-field and far-field earthquakes (in relation to Hong Kong) have been derived using the ECD method. The present paper describes the modelling of the response spectrum on rock sites associated with the predicted M–R combinations, using the Component Attenuation Model (CAM) that was also developed recently by the authors, based on stochastic simulations of the seismological model. The significant effects of soil resonance on the response spectrum are described in a separate publication.The accuracy of CAM in modelling ground motion properties on rock sites has been tested here by comparisons with (i) strong motions recorded in Taiwan and South China from the 1999 ‘Chi-Chi’ earthquake in Taiwan (M=7.6), (ii) motions recorded in South China from another earthquake occurring in the southern Taiwan Strait in the same year (M=5.1), and (iii) historical seismic intensity data obtained within South China. The overall capability of CAM in modelling both near-field and far-field attenuation has been shown to be unmatched by existing empirical models. Results of the comparison studies confirm the accuracy of CAM, particularly within an epicentral distance of 300–400 km.This study shows that the developed serviceability response spectra (i.e. at short return periods) are controlled mainly by the earthquake recurrence behaviour of major distant seismic sources. In contrast, the ultimate response spectra (i.e. at long return periods) relate to events with magnitudes close to the maximum credible earthquake (MCE) limit, the effect of which may also be represented by the Characteristic Response Spectrum (CRS). Both types of earthquake scenario can be significantly affected by the regional crustal properties. The proposed response spectrum envelopes have been compared with previously developed recommendations, and a critical review has been conducted. The intrinsic advantages of the ECD–CAM modelling approach have been highlighted, emphasising its directness and transparency when compared with the more complex process required to implement traditional Probabilistic Seismic Hazard Assessment (PSHA).  相似文献   

海岸侵蚀作用下海岸带地区极端风暴洪水风险评估 —以上海石化为例     

刘青  张卫国  Nina Siu-Ngan Lam  王军 《海洋通报》2022,(2)

海堤是海岸带地区社会经济活动的重要保护屏障。海岸侵蚀的加剧将导致海堤稳定性和安全性降低, 增加海岸带地 区遭受极端风暴洪水的风险, 进而影响到海岸带地区的安全。本文选择上海石化这一遭受海岸侵蚀较为严重的区域作为研究 区, 利用 GIS 分析了 1972—2020 年近岸海床侵蚀特征, 并基于 2000—2020 年-5 m 等深线变化评估了上海石化近岸海堤的 稳定性。结果表明： 1972—2020 年间上海石化前沿海床整体以侵蚀为主, 石化近岸东侧以及西侧局部的浅滩侵蚀明显, 城 市沙滩中段、第 6 次围堤处以及码头东岸海堤稳定性最低。基于上述研究结果, 考虑海堤稳定性薄弱段出现极端风暴洪水漫 堤或溃堤情景, 模拟并分析了上海石化 2010 年 、2030 年和2050 年遭受千年一遇极端风暴洪水的风险。结果显示： 在 2010 年基准年情景下, 受海岸侵蚀作用最明显的城市沙滩和第6 次围堤区域遭遇极端风暴洪水的风险最高, 到 2050 年, 当前稳 定性较好的海堤安全性也将大大降低, 与 2010 年相比, 上海石化近岸地区的直接经济损失将会增加近 3 倍。  相似文献   

Comparison of the performance of flow‐routing algorithms used in GIS‐based hydrologic analysis     

John P. Wilson  Christine S. Lam  Yongxin Deng 《水文研究》2007,21(8):1026-1044

Flow direction and specific catchment area were calculated for different flow‐routing algorithms using TAPES‐G and TauDEM. A fuzzy classification was used along with eight topo–climatic attributes to delineate six landscape classes from a 10‐m USGS DEM. A series of maps and tabular outputs were produced to compare flow‐routing predictions in different parts of the study area in the Santa Monica Mountains of southern California. The matched pair t‐test was used to compare the performance of pairs of specific catchment area grids across six user‐defined fuzzy landscape classes. The results show that (1) the ‘source’ cells predicted with the D∞, DEMON, and FD8 algorithms were confined to hilltops; (2) two single flow‐routing algorithms (Rho8, D8) produced poor results; and (3) the choice of flow‐routing algorithm has potentially important consequences for the calculation of upslope contributing areas, sediment transport capacity, topographic wetness, and several other topographic indices. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Risks posed by trace organic contaminants in coastal sediments in the Pearl River Delta, China   总被引：8，自引：0，他引：8  

Fung CN  Zheng GJ  Connell DW  Zhang X  Wong HL  Giesy JP  Fang Z  Lam PK 《Marine pollution bulletin》2005,50(10):1036-1049

Local marine environments in China's Pearl River Delta (PRD), the most rapidly developing region in one of the world's fastest growing economies, have been experiencing significant environmental stress during the past decades. This investigation was conducted to determine the status and trends of persistence organic pollutants (POPs) such as polycyclic aromatic hydrocarbons (PAHs), petroleum hydrocarbons (PHCs), polychlorinated biphenyls (PCBs), organochlorine (OC) pesticides and dioxin-related compounds in marine sediments collected from sixteen coastal stations in the Pearl River Delta (PRD) in March 2003. Elevated concentrations of PAHs (94-4300 ng/g), PCBs (6.0-290 ng/g), PHCs (14-150 microg/g), and DDTs (1.4-600 ng/g) were detected in sediment samples. In addition, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-like activities in the sediment samples were estimated to range from 0.3 to 440 pg TCDD-EQ/g. Sediments collected from Xiashan contained the greatest concentrations of trace organic contaminations amongst all the sampling stations in the present study. The degree of trace organic contamination was, in general, more severe at stations situated along the west shores of the PRD than their counterparts in the east. A preliminary assessment was performed to examine the probable risks to the marine ecosystem due to POPs. The results showed that OC pesticide contamination in the PRD was particularly serious and might pose a threat to the health of the marine inhabitants.  相似文献