三孔较差视宁度仪的对比观测

三孔较差视宁度仪（ＤＩＭＭ）已在丽江高美古和云南天文台投入观测，我们用云南天文台的一米望远镜测得的视宁度与ＤＩＭＭ所测得的视宁度进行对比。１９９５年上半年获得了５个晚上的资料，测得的结果表明ＤＩＭＭ测量的视宁度与一米望远镜测量的视中度是相关的。二套ＤＩＭＭ也进行了相互校正和对比，共用了８个晚上获得１２５组ｒ０，二套ＤＩＭＭ的视宁度测量值是相关的，二套系统的误差小于１％。     

Laboratory and numerical investigation of flow and transport near a seepage-face boundary

Laboratory and numerical modeling investigations were completed to study the unconfined ground water flow and transport processes near a seepage-face boundary. The laboratory observations were made in a radial sand tank and included measurements of the height of the seepage face, flow velocity near the seepage face, travel time distribution of multiple tracer slugs, and streamlines. All the observations were reliably reproduced with a three-dimensional, axi-symmetric, variably saturated ground water flow model. Physical data presented in this work demonstrate and quantify the importance of three-dimensional transport patterns within a seepage-face zone. The results imply that vertically averaged flow models that employ Dupuit approximations might introduce error in the analysis of localized solute transport near a seepage-face boundary. The experimental dataset reported in this work will also be of interest for those who are attempting to validate a numerical algorithm for solving ground water and contaminant discharge patterns near a surface-water boundary.     

Antifouling paint booster biocides in the UK coastal environment and potential risks of biological effects

In the yachting sector of the UK antifouling market, organic biocides are commonly added to antifouling preparations to boost performance. Few data presently exist for concentrations of these compounds in UK waters. In this study the concentrations of tributyltin (TBT) and eight booster biocides were measured before and during the 1998 yachting season. The Crouch Estuary, Essex, Sutton Harbour, Plymouth and Southampton Water were chosen as representative study sites for comparison with previous surveys of TBT concentrations. Diuron and Irgarol 1051 were the only organic booster biocides found at concentrations above the limits of detection. Diuron was measured at the highest concentrations, whilst detectable concentrations of both Irgarol 1051 and diuron were determined in areas of high yachting activity (e.g. mooring areas and marinas). Maximum measured values were 1,421 and 6,740 ng/l, respectively. Lower concentrations of both compounds were found in open estuarine areas, although non-antifouling contributions of diuron may contribute to the overall inputs to estuarine systems. TBT was found to be below or near the environmental quality standard (EQS) of 2 ng/l for all samples collected from estuarine areas frequented by pleasure craft alone, but with much higher concentrations measured in some marinas, harbours and in areas frequented by large commercial vessels. Using the limited published environmental fate and toxicity data available for antifouling booster biocides, a comparative assessment to evaluate the risk posed by these compounds to the aquatic environment is described. TBT still exceeds risk quotients by the greatest margins, but widespread effects due to Irgarol 1051 and less so diuron cannot be ruled out (particularly if use patterns change) and more information is required to provide a robust risk assessment.     

Comparability of bioaccumulation within the sanddab guild in coastal Southern California

Most assessments of fish contamination in Southern California use ecologically different species from different sites. Use of ecologically similar species (a guild) might provide better assessments of fish contamination across different sites and depths. In July-August 1997, we collected samples of four sanddab guild species at 22 sites where species pairs co-occurred and determined total DDT concentrations in homogenized whole fish composites. Log-transformed DDT concentrations were highly correlated among all species pairs within this guild. All relationships were linear over the range observed, with slopes not statistically different from unity. The variability in response among species was about four times the variability encountered among replicates within species, but 15 times smaller than the variability among sites. Together, these results suggest that the sanddab guild, widespread on soft bottoms of the Southern California coastal shelf, can be used as a "superspecies" in bathymetrically diverse regional assessments of fish tissue contamination.     

来自海洋地壳深处的甲烷

在许多语气表明，在地球的更深化部位存在着来自地幔的巨厚甲烷储层。这种成因类型的甲烷在Ｃ，Ｏ，Ｈ同位素上与有机质正常裂解所形成的甲烷气明显不同。Ｋｅｌｌｅｙ认为该类ＣＨ４的形成至少有两个阶段；第一阶段涉及到岩浆挥发分，形成的温度较高，ＣＨＲ被捕获在包体中，并在其中继续发生ＣＯ２转化为ＣＨ４的反应，使ＣＨ４聚集较轻的碳同位素，即残留的ＣＯ２比原始地幔气更重；第二阶段发生于４００℃左右，由于冷却作用，在