地中海海脊泥角砾岩的无机地球化学特征

地中海海脊泥角砾岩的无机地球化学特征ＳｉｍｏｎＪ．Ｗａｋｅｆｉｅｌｄ等地中海海脊是由非洲板块俯冲到爱琴海底部而形成的加积楔体系（Ｒｙａｎ等，１９８２）．最近，在海脊顶部详细的海底调查结果发现了泥底辟区（火山），这些底辟带可能是沉积物质向上运动而形成的...     

Sublethal toxicity of orchard stormwater runoff in Sacramento splittail (Pogonichthys macrolepidotus) larvae

The sublethal effects of stormwater runoff from sections of a plum orchard treated with esfenvalerate or diazinon were evaluated in 7-day-old Sacramento splittail (Pogonichthys macrolepidotus) larvae. Fish were exposed to eight runoff samples using the USEPA standard static renewal method for 96 h acute toxicity testing, then transferred to clean water for three-month to assess the survival, growth, histopathological abnormalities, and heat stress proteins (hsp). No significant mortality was observed at 96 h in exposed fish. At one week, histopathological abnormalities included severe glycogen depletion, cytoplasmic protein droplets, vacuolar degeneration, and cell necroses in liver of all exposure groups. Pyknotic nerve cells were seen in brain of one exposure group. Significantly higher cumulative mortality, lower condition factor, and elevated hsp60 and hsp70 levels (p < 0.05) were occurred in several exposure groups. No histopathological abnormalities were observed after three months in any exposure group. This study confirms that standard acute toxicity tests have underestimated the toxicity of stormwater runoff, and although splittail larvae survived the 96 h exposure, they exhibited reduced survival and growth and showed signs of cellular stress even after a three month recovery period.     

Factors affecting the distribution of benthic macrofauna in estuaries contaminated by urban runoff

Contaminants derived from urban runoff have been shown to accumulate in estuarine sediments, reaching concentrations potentially capable of causing biological effects. Demonstration of effects, however, is difficult due to strong natural environmental gradients and the effects of past or present point-sources of contamination. We used multivariate methods to test two hypotheses relating to the effects of urban-derived contaminants on estuarine benthic communities. First, that patterns of distribution and abundance of benthic invertebrates in two urbanised estuaries would be different from those in two non-urbanised estuaries. Second, that the distributions of benthic invertebrates within and among the four estuaries would be related to those of urban-derived contaminants. Concentrations of contaminants were larger in estuaries with urbanised catchments and concentrations of Cu, Pb, Zn and DDT in some samples exceeded those at which biological effects may be expected to appear. Tests of differences in composition of benthic communities among estuaries showed that the two urban estuaries were not significantly different, but that they differed from both rural estuaries, which also differed from each other. Distributions of benthic invertebrates were significantly related to those of environmental variables, and were ordinated along axes that correlated with both natural environmental variables (nature of the sediment, position in estuary) and contaminants. Differences in faunas between the urban and non-urban estuaries were not, however, clear-cut and nor were relationships between faunal assemblages and environmental variables (including contaminants) consistent between two times of sampling.     

Assessing the impact of nutrient enrichment in estuaries: susceptibility to eutrophication

The main aim of this study was to develop a generic tool for assessing risks and impacts of nutrient enrichment in estuaries. A simple model was developed to predict the magnitude of primary production by phytoplankton in different estuaries from nutrient input (total available nitrogen and/or phosphorus) and to determine likely trophic status. In the model, primary production is strongly influenced by water residence times and relative light regimes. The model indicates that estuaries with low and moderate light levels are the least likely to show a biological response to nutrient inputs. Estuaries with a good light regime are likely to be sensitive to nutrient enrichment, and to show similar responses, mediated only by site-specific geomorphological features. Nixon's scale was used to describe the relative trophic status of estuaries, and to set nutrient and chlorophyll thresholds for assessing trophic status. Estuaries identified as being eutrophic may not show any signs of eutrophication. Additional attributes need to be considered to assess negative impacts. Here, likely detriment to the oxygen regime was considered, but is most applicable to areas of restricted exchange. Factors which limit phytoplankton growth under high nutrient conditions (water residence times and/or light availability) may favour the growth of other primary producers, such as macrophytes, which may have a negative impact on other biological communities. The assessment tool was developed for estuaries in England and Wales, based on a simple 3-category typology determined by geomorphology and relative light levels. Nixon's scale needs to be validated for estuaries in England and Wales, once more data are available on light levels and primary production.     

ECMWF业务预报系统的改进

欧洲中期预报中心(ECMWF)第二个业务模式——T63(谱模式)1983年4月21日投入业务使用后,进行了以下改进:1984年12月4日,改进了辐射格式,在解决长波辐射传输方面,使用了与过去不同的气体效应处理方法,其最大好处是缓和了中、高对流层中,云量少的层次所出现的过     

Assessing the suitability of OSPAR EcoQOs for eutrophication vs ICES criteria for England and Wales

This paper provides a preliminary evaluation of the suitability of OSPAR Ecological Quality objectives for eutrophication for coastal and offshore waters of England and Wales on the basis of ICES criteria. In principle, EcoQOs are easy to understand, but responses to nutrient enrichment are complex. Few studies provide unequivocal evidence of links between inputs and response. Monitoring is generally feasible and in place, but needs to be improved. The best EcoQO is winter nutrient concentrations. Chlorophyll concentrations are a good indicator in environments susceptible to nutrient enrichment. The EcoQO for zoobenthos/fish kills potentially meets all criteria for a good indicator; EcoQOs for phytoplankton indicator species, oxygen concentrations and zoobenthos changes do not. Greater emphasis needs to be placed on seasonal effects of nutrient inputs and phytoplankton response, natural susceptibility of different water bodies, differences between coastal and offshore environments, and developing longer time series of data.     

Measurement of Charge Exchange and X-Ray Emission Cross Sections for Solar Wind-Comet Interactions

X-ray emission from a comet was observed for the first time in 1996. One of the mechanisms believed to be contributing to this surprisingly strong emission is the interaction of highly charged solar wind ions with cometary gases. Reported herein are total absolute charge-exchange and normalized line-emission (X-ray) cross sections for collisions of high-charge state (+3 to +10) C, N, O, and Ne ions with the cometary species H2O and CO2. It is found that in several cases the double charge-exchange cross sections can be large, and in the case of C3+ they are equal to those for single charge exchange. Present results are compared to cross section values used in recent comet models. The importance of applying accurate cross sections, including double charge exchange, to obtain absolute line-emission intensities is emphasized.