Variations in benthic fauna underneath an effluent mixing zone at a marine oil terminal in Port Valdez, Alaska

The distributions of hydrocarbons and infauna in sediments below a permitted mixing zone for the disposal of treated ballast waters in Port Valdez, Alaska were examined annually, 1999–2001. The associations of biological measures and the abundance of selected benthic organisms to total aromatic hydrocarbons (TARO) ranged up to large-sized effects, as compared against minimum-effect criteria (|r|0.63). The apparent sensitivity of three polychaete worms to low levels of hydrocarbons makes them particularly useful as indicators of future changes in spatial distributions of hydrocarbons associated with discharged effluent. In 2001, sediment TARO concentrations decreased and the correlation values of TARO to biotic variables were generally less than in 1999 and 2000. Evidence supports a conclusion of a strong but spatially limited association of some fauna with accumulations of petroleum hydrocarbons in these sediments.     

泰国地震考察概述

以国家地震局科技监测司副司长孙其政为团长的中国数字地震台网考察团,一行10人,于1989年10月13日,赴泰国进行了为期8天的地震考察。在此期间,我们对不久前在泰缅边界发生的6.4级破坏性地震现场进行了考察,以及位于泰国西北部距曼谷近300公里的2个水库大坝和电站。两国地震工作者就如何利用强震仪监测库区水位变化,如何研究强地面运动对水坝的影响等多项内容进行了讨论;两国台站的工     

Temporal variations of coda Q~（－1） associated with the dahaituoshan， Beijing， earthquake of 1990

Ｐｒｅｓｅｎｔａｄｄｒｅｓｓ：ＳｏｕｔｈＣａｌｉｆｏｒｎｉａＵｎｉｖｅｒｓｉｔｙ，ＵＳＡ．ＣｏｎｔｒｉｂｕｔｉｏｎＮｏ．９３Ａ００３２，ＩｎｓｔｉｔｕｔｅｏｆＧｅｏｐｈｙｓｉｃｓ，ＳＳＢ，Ｃｈｉｎａ．ａｎｄｓｔａｔｉｏｎａｒｅｓｅｐａｒａｔｅ，ｓｕｐｐｏｓｉｎｇａｒａｎｄｏｍａｎｄｈｏｍｏｇｅｎｅｏｕｓｄｉｓｔｒｉｂｕｔｉｏｎｏｆｔｈｅｓｃａｔｔｅｒｓｉｎａｔｈｒｅｅ－ｄｉｍｅｎｓｉｏｎａｌｉｎｆｉｎｉｔｅａｎｄｐｅｒｆｅｃｔｌｙｅｌａｓｔｉｃｍｅｄｉｕｍ．ＴｈｅｅｎｅｒｇｙｄｅｎｓｉｔｙａｔａｄｉｓｔａｎｃｅｏｆｒｉｓｇｉｖｅｎａｓＥ（ｒ，ｔ｜ω）＝［Ｗ０（ω）ｇ０（ω）］／（４πｒ２）．Ｋ（ｖｔ／ｒ）．ｅｘｐ（－ωＱｃ－１ｔ）ｖｔ＞ｒ（２）ＷｈｅｒｅＫ（ｘ）＝（１／ｘ）ｌｎ［（ｘ＋１）／（ｘ－１）］，ａｎｄｇ０（ω）ｉｓｔｈｅｔｏｔａｌｓｃａｔｔｅｒｉｎｇｃｏｅｆｆｉｃｉｅｎｔｃｈａｒａｃｔｅｒｉｚｉｎｇａｓｃａｔｔｅｒｉｎｇｐｏｗｅｒｐｅｒｕｎｉｔｖｏｌｕｍｅｏｆｔｈｅｈｏｍｏｇｅｎｅｏｕｓｍｅｄｉｕｍ．Ｃｏｍｐａｒｉｓｏｎｏｆｖａｒｉｏｕｓｏｂｓｅｒｖａｔｉｏｎｓｉｎｃｌｕｄｉｎｇｃｏｄａｄｅｃａｙ     

震源对面波群走时和群速度图的影响

在大多数地震面波的研究中,观测到的群走时被解释为全部由波沿传播路径产生的时延迟,并且认为震源效应非常小而可忽略不计。这与观测的震相时间不同。因为对震源相进行校正一般认为是必须做的。一个重要的但尚未解决的问题是宽频带面波研究中对震源群走时（ＳＧＴ）的忽略如休影响测量的群速度曲线和利用观测数据进行层析成像的精度,本文考虑ＳＧＴ对基阶瑞利波群速度测量的范围,并论述其对周期（１０－２００ｓ）震源机制和震源     

20年代地震预报暴露了一些地震预报的陷阱问题

一些地震学家正在寻求作出科学上合理的地震预报的可能性。而另一些人则关心着大众对地震预报如何反应(NationalResearch Council,1978;Geller,1997)。20世纪20年代,美国地震学会主席曾公开预报,南加州将在最近10a内遭受一次强烈     

Assessment of variables controlling nitrate dynamics in groundwater: is it a threat to surface aquatic ecosystems?

The impact of fertilised cropping on nitrate-N dynamics in groundwater (GW) was assessed in a catchment from piezometers installed: (i) to different depths, (ii) in different soil types, (iii) on different positions on landscape, and (iv) compared with the Australian and New Zealand Environmental and Conservation Council guideline values provided for different aquatic ecosystems. The GW and NO(3)-N concentration dynamics were monitored in 39 piezometer wells, installed to 5-90 m depth, under fertilized sugarcane (Saccharum officinarum-S) in the Johnstone River Catchment, Australia, from 1999 January through September 2002. The median nitrate-N concentration ranged from 14 to 1511 microg L(-1), and the 80th percentile from 0 to 1341 microg L(-1). In 34 out of the 39 piezometer wells the 80th percentile or 80% of the nitrate-N values were higher than 30 microg L(-1), which is the maximum trigger value provided in the ANZECC table for sustainable health of different aquatic ecosystems. Nitrate-N concentration decreased with increasing well depth, increasing depth of water in wells, and with decreasing relief on landscape. Nitrate-N was higher in alluvial soil profiles than on those formed in-situ. Nitrate-N increased with increasing rainfall at the beginning of the rainy season, fluctuated during the peak rainy period, and then decreased when the rain ceased. The rapid decrease in GW after the rains ceased suggested potential existed for nitrate-N to be discharged as lateral-flow into streams. This may contribute towards the deterioration in the health of down-stream aquatic ecosystems.     

Metal tissue levels in Steller sea lion (Eumetopias jubatus) pups

The endangered Western population of the Steller sea lion declined for three decades for uncertain reasons. We present baseline data of metal concentrations in pups as a first step towards investigating the potential threat of developmental exposures to contaminants. Seven metals were investigated: arsenic, cadmium, silver, aluminum, mercury, lead and vanadium. Vanadium was detected in only a single blubber sample. Mercury appears to be the most toxicologically significant metal with concentrations in the liver well above the current action level for mercury in fish. The concentrations of aluminum, arsenic, silver, cadmium and lead were present in one-fourth to two-thirds of all samples and were at either comparable or below concentrations previously reported. Neither gender nor region had a significant effect on metal burdens. Future work should consider metal concentrations in juveniles and adults and toxicological studies need to be performed to begin to assess the toxicity of these metals.     

Evaluation of volatilization as a natural attenuation pathway for MTBE

Volatilization and diffusion through the unsaturated zone can be an important pathway for natural attenuation remediation of methyl tert-butyl ether (MTBE) at gasoline spill sites. The significance of this pathway depends primarily on the distribution of immiscible product within the unsaturated zone and the relative magnitude of aqueous-phase advection (ground water recharge) to gaseous-phase diffusion. At a gasoline spill site in Laurel Bay, South Carolina, rates of MTBE volatilization from ground water downgradient from the source are estimated by analyzing the distribution of MTBE in the unsaturated zone above a solute plume. Volatilization rates of MTBE from ground water determined by transport modeling ranged from 0.0020 to 0.0042 g m(-2)/year, depending on the assumed rate of ground water recharge. Although diffusive conditions at the Laurel Bay site are favorable for volatilization, mass loss of MTBE is insignificant over the length (230 m) of the solute plume. Based on this analysis, significant volatilization of MTBE from ground water downgradient from source areas at other sites is not likely. In contrast, model results indicate that volatilization coupled with diffusion to the atmosphere could be a significant mass loss pathway for MTBE in source areas where residual product resides above the capillary zone. Although not documented, mass loss of MTBE at the Laurel Bay site due to volatilization and diffusion to the atmosphere are predicted to be two to three times greater than mass loading of MTBE to ground water due to dissolution and recharge. This result would imply that volatilization in the source zone may be the critical natural attenuation pathway for MTBE at gasoline spill sites, especially when considering capillary zone limitations on volatilization of MTBE from ground water and the relative recalcitrance of MTBE to biodegradation.     

地球内核真的旋转吗？

地球固体内核,一个半径为1220km(地球液体核的1/3)的铁合金球体,吸引着许多科学家在许多领域探索了至少10年。地球内核的一个显著特性是各向异性:地震波沿平行于地球旋转轴方向的传播比沿垂直于地球旋转轴方向的传播快。这种3％     

基于无人机倾斜影像的数字校园三维重建

为研究基于无人机倾斜影像的数字三维重建的优缺点,对传统的三维模型重建方法与基于无人机倾斜影像重建三维模型的方法进行了对比分析。实验结果表明:传统的建模方式耗时比较长,但是模型精细;而基于倾斜影像重建三维模型方式可以快速获取大场景模型,但是模型细节较差,仍需后续进行手工修复。因此,实际建模需要根据需要,将二者结合起来,取长补短,发挥各自优势。