Impact of offsite sediment transport and toxicity on remediation of a contaminated estuarine bay     

Pascoe GA  McLaren P  Soldate M 《Marine pollution bulletin》2002,44(11):1184-1193

Sediment of Ostrich Bay, an arm of Dyes Inlet on Puget Sound, was historically contaminated with ordnance compounds from an onshore US Navy facility. An initial recommendation for a sediment cover to mitigate benthic risks was followed by studies of sediment transport and deposition to determine whether contaminated sediment from Dyes Inlet or other offsite sources in Puget Sound may contribute to Ostrich Bay impacts. A Sediment Trend Analysis (STA) identified net sediment transport pathways throughout the bay and inlet by examining changes in grain size distributions in multiple adjacent samples. Results indicated that fine-grained sedimentary material transports into and deposits throughout the Dyes Inlet system, with no erosion or transport out of Ostrich Bay. Echinoderm larvae mortality bioassay results were elevated in fine-grained sediments of both Ostrich Bay and Dyes Inlet. Ordnance compounds were undetected, and although sediment mercury concentrations were elevated at 0.48-1.4 mg/kg in both waterbodies, the relationship with toxicity was weak. Results of the studies and sedimentation modeling indicate that impacted sedimentary material deposits throughout the Dyes Inlet/Ostrich Bay system from unknown sources and will prevent natural recovery of Ostrich Bay as well as negate long-term effectiveness of active remedial measures. Stakeholders have recognized that remediation of the bay can be achieved only after the toxicity of depositing sediment decreases.  相似文献   

荒漠动植物群落类型与演化过程概览     

波利.  GA 李胜功 《世界沙漠研究》1994,(2):19-23

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巴哈马的阿巴科岛外声学传播时间和动态高度偏差现象间的关系     

Maul  GA 张淑芝 《海洋技术学报》1994,13(2):12-17

倒置回声测深仪（ＩＥＳ＇Ｓ）是用来测量ＩＥＳ到海表面环行声学传播时间。推荐这些相当谦价的海底安装的仪器是为了以下几个目的：ａ．长期监测特殊站点的动力变化（如热容量、温跃层、动力高度偏差等）；ｂ．卫星高度计的公海标准，ｃ．研究近岸验潮仪和近海验潮仪之间不同的海平面信号。为测量海平面的变化，特别是厘米级精确度的变化，必须获得传输时间和动态高度偏差之间的精确关系。假设在动态高度偏差和传播时间之间有不变的  相似文献   

Using atmospheric tracers to reduce uncertainty in groundwater recharge areas     

Starn JJ  Bagtzoglou AC  Robbins GA 《Ground water》2010,48(6):858-868

A Monte Carlo-based approach to assess uncertainty in recharge areas shows that incorporation of atmospheric tracer observations (in this case, tritium concentration) and prior information on model parameters leads to more precise predictions of recharge areas. Variance-covariance matrices, from model calibration and calculation of sensitivities, were used to generate parameter sets that account for parameter correlation and uncertainty. Constraining parameter sets to those that met acceptance criteria, which included a standard error criterion, did not appear to bias model results. Although the addition of atmospheric tracer observations and prior information produced similar changes in the extent of predicted recharge areas, prior information had the effect of increasing probabilities within the recharge area to a greater extent than atmospheric tracer observations. Uncertainty in the recharge area propagates into predictions that directly affect water quality, such as land cover in the recharge area associated with a well and the residence time associated with the well. Assessments of well vulnerability that depend on these factors should include an assessment of model parameter uncertainty. A formal simulation of parameter uncertainty can be used to delineate probabilistic recharge areas, and the results can be expressed in ways that can be useful to water-resource managers. Although no one model is the correct model, the results of multiple models can be evaluated in terms of the decision being made and the probability of a given outcome from each model.  相似文献   

Organochlorine contaminants in endangered Hawaiian monk seals from four subpopulations in the Northwestern Hawaiian Islands     

Ylitalo GM  Myers M  Stewart BS  Yochem PK  Braun R  Kashinsky L  Boyd D  Antonelis GA  Atkinson S  Aguirre AA  Krahn MM 《Marine pollution bulletin》2008,56(2):231-244

We analyzed blubber and blood samples for organochlorines (OCs) from 158 Hawaiian monk seals (Monachus schauinslandi) at four of their six primary breeding colonies in the Northwestern Hawaiian Islands. Levels of OCs in blubber were lower in adult females compared to juveniles or adult males, evidently owing to the transfer of these lipophilic compounds to pups by pregnant and lactating females. Concentrations of SigmaPCBs and p,p'-DDE in blubber generally increased with age until seals were sexually mature and then continued to increase with age in males after puberty. Average levels of PCBs and PCB toxic equivalents (TEQs) in blubber were significantly higher in adult male and juvenile seals at Midway Atoll than the same age class of seals at the other colonies. Unlike concentrations of OCs in blubber, circulating levels of OCs in blood did not vary consistently among age classes of seals or among breeding colonies. Though the concentrations of OCs measured in Hawaiian monk seals were generally equal to or lower than those reported for other pinniped species in the North Pacific Ocean, they were high enough in a few seals to potentially affect their health.  相似文献   

对逆冲断层一些普遍观念的质疑：以美国西部科迪勒拉及中国华北的野外研究？     

Davis  GA 《地学前缘》1999,6(3):49-66

在过去的２５年里,由于许多原因,作为最常见,分布也最广泛的地质构造形迹之一,逆冲断层成为倍受关注的科学研究主题。文中指出,关于逆总断层及其几何学特征的许多普遍认识,并不像以往文献中所阐述的那样简单,其中之一的“薄皮”冲断构造是受地层控制的,极少有或者没有结晶基底物的卷入。  相似文献   

21世纪的天气预报     

MeBe.  GA 郑贵华 《沙漠与绿洲气象(新疆气象)》1999,22(6):49-50

大气——地球的成员20世纪的最后几年,大自然遗赠我们一些极端事件。飓风、龙卷风、冬季风暴、洪水和其它灾害给地球人类的生活造成惨重的损失。1998年,与天气相关的灾害造成的世界经济损失约有900亿美元,比1996年的记录增加了将近50％。在人类追求财富和经济增长的过程中,各国政府逐步认识到天气、气候、空气质量及其它环境因素在政府和个人决策时日益重要。在进入下个世纪的时候,将迫使我们进一步提供几分钟至数十年的大气及其变化情况。这些服务将远远超出日常的天气预报。还要为保护健康、减轻灾害、发展经济等各种各样的计划和决…  相似文献   

Effects of barium and cadmium on the population development of the marine nematode Rhabditis (Pellioditis) marina     

Lira VF  Santos GA  Derycke S  Larrazabal ME  Fonsêca-Genevois VG  Moens T 《Marine environmental research》2011,72(4):151-159

Offshore oil and gas drilling often involves the use of fluids containing barium and traces of other heavy metals. These may affect the environment, but information on their toxicity to benthic biota remains scant. Here, we present results of a 10-day bioassay with the marine nematode Rhabditis (Pellioditis) marina at different loads of barium (0-10 ,000 ppm nominal concentrations) and cadmium (0-12 ppm) in the range of concentrations reported from drilling-impacted sediments. Barium did not affect the fitness and population development of R. (P.) marina at concentrations up to 300 ppm, but did cause a decrease in population abundance and an increase in development time from concentrations of 400-2000 ppm onwards. Increased mortality occurred at 4800 ppm Ba. For cadmium, LOEC and EC?? values for total population abundance were 2.95 and 8.82 ppm, respectively. Cd concentrations as low as 2.40 to 2.68 caused a decrease in the abundance of adult nematodes, indicating that assays covering more generations would likely demonstrate yet more pronounced population-level effects. Our results indicate that oil and gas drilling activities may potentially have important implications for the meiobenthos through the toxicity of barium and associated metals like cadmium.  相似文献   

Sediment characteristics and macrofauna distribution along a human-modified inlet in the Gulf of Oristano (Sardinia, Italy)     

Como S  Magni P  Casu D  Floris A  Giordani G  Natale S  Fenzi GA  Signa G  De Falco G 《Marine pollution bulletin》2007,54(6):733-744

We studied the spatial variability and within-year temporal changes in hydrological features, grain size composition and chemical characteristics of sediments, as well as macrofaunal assemblages, along a heavily modified inlet in the Gulf of Oristano (western Sardinia, Italy). The inlet connects the Cabras lagoon to the gulf through a series of convoluted creeks and man-made structures, including a dam and fish barriers built in the last three decades. Sediments were muddy and mainly composed of the "non-sortable" fraction (i.e., <8 microm particle size) in all four areas investigated: Lagoon, Creeks, Channel and Seaward. Along the inlet, however, the ratio between the <8 microm and the 8-64 microm fractions was highest in Creeks and Channel, between the fish barriers and the dam, suggesting impaired hydrodynamics. Consistently, steep gradients in water salinity, temperature and dissolved oxygen concentrations were found in proximity to the fish barriers. The whole inlet was characterized by a major organic enrichment of sediments, with up to an annual mean of 33.6% of organic matter and 11.7% of total organic carbon in Seaward due to the presence of seagrass leaf litter. Acid-volatile sulphide and chromium-reduced sulphur concentrations were highest throughout the year in Seaward and Lagoon, respectively, with a peak in summer. Consistently, the whole inlet supported low structured macrofaunal assemblages dominated by few opportunist species, with a relatively lower diversity in Lagoon throughout the year and the highest abundances in Seaward in summer. We infer that the presence of artificial structures along the inlet, such as fish barriers and the dam, impair the lagoon-gulf hydrodynamics, sediment exchange and animal recruitment and colonization. We suggest that the removal of these structures would favour water renewal in the Cabras lagoon, but would also increase the outflow of organic C-bonding fine particles into the gulf with serious consequences for Posidonia oceanica and Cymodocea nodosa seagrass meadows. We conclude that all possible consequences of such initiatives should be carefully considered before any action is taken.  相似文献   

The molecular emission-line spectrum of IRC +10216 between 330 and 358 GHz     

Groesbeck TD  Phillips TG  Blake GA 《The Astrophysical journal. Supplement series》1994,94(1):147-162

We have conducted a spectral line survey of IRC +10216 using the Caltech Submillimeter Observatory to an average sensitivity of < or approximately 95 mK. A deconvolution algorithm has been used to derive the continuous single-sideband spectrum from 330.2 to 358.1 GHz. A total of 56 spectral lines were detected of which 54 have been identified with 8 molecules and a total of 18 isotopomers. The observed lines are used to derive column densities and relative abundances for the detected species. Within this frequency range the spectral lines detected contribute the majority of the total flux emitted by IRC +10216. We use the derived column densities and excitation temperatures to simulate the molecular line emission (assuming LTE) at frequencies up to 1000 GHz. The observed and simulated flux from line emission is compared to broadband total flux measurements and to dust emission assuming a power-law variation of the dust emissivity. We conclude that significant corrections for the line flux must be made to broadband flux measurements of IRC +10216 at wavelengths longer than approximately 750 micrometers.  相似文献