Heavy metal concentrations in growth bands of corals: a record of mine tailings input through time (Marinduque Island,Philippines)

The impact of copper mining along the western coast of Marinduque Island was investigated. Historic input of mine tailings in the coastal region was traced through variations in heavy metal concentrations in Porites growth bands. Five samples were collected from three reefs showing different modes and extent of exposure to mine tailings. Baseline metal concentrations in Porites were established using a coral from a reef that is least exposed to contamination. The lowest mean values of Cu (0.7 microg/g), Mn (0.8 microg/g), and Zn (1.0 microg/g) were calculated from annual skeletal bands representing five years of growth. Conversely, a sample from a reef adjacent to an old tailings stockpile displayed consistently elevated metal values in its growth bands. Mean Cu, Mn, and Zn values for this coral are 3.1, 1.0 and 1.8 microg/g, respectively. Corals from the Ihatub reef showed a distinct metal concentration peak in their 1996 growth ring. These peaks coincide with a documented release of mine tailings in the Ihatub area during that year. Other metal peaks observed in coral samples correlate with years of high precipitation which may have resulted in increased sediment transport in the region. The metals are presumed to be mostly bound to the aragonite lattice of the coral skeleton, however, contribution from incorporated detrital materials to the observed metal signal (mainly of Fe) could not be easily discounted.     

利用岩石声发射活动性的应力履历效应估计地壳应力

引言 岩石的声发射活动性能够“记忆”岩石所受过的最大应力,这种效应称为凯赛效应。它是Kaiser,J.1953年在金属材料的拉伸试验中首先发现的。后来Goodman(1963)、金川忠等(1977)在岩石压缩试验中也证实了凯赛效应的存在。金川忠等(1978)认为,利用定向钻孔岩芯制备的定向试件声发射活动性的变化,可以确定地壳应力状态。这个应力状态与同一地点的套芯法和水压致裂法原地应力测量结果相比较,有可能估计测量地区应力状态的变化趋势。这对于判断天然断层的稳定性具有十分重要的意义。这个     

A coupled soil-atmosphere model of H2O2 on Mars

The Viking Gas Chromatograph Mass Spectrometer failed to detect organic compounds on Mars, and both the Viking Labeled Release and the Viking Gas Exchange experiments indicated a reactive soil surface. These results have led to the widespread belief that there are oxidants in the martian soil. Since H2O2 is produced by photochemical processes in the atmosphere of Mars, and has been shown in the laboratory to reproduce closely the Viking LR results, it is a likely candidate for a martian soil oxidant. Here, we report on the results of a coupled soil/atmosphere transport model for H2O2 on Mars. Upon diffusing into the soil, its concentration is determined by the extent to which it is adsorbed and by the rate at which it is catalytically destroyed. An analytical model for calculating the distribution of H2O2 in the martian atmosphere and soil is developed. The concentration of H2O2 in the soil is shown to go to zero at a finite depth, a consequence of the nonlinear soil diffusion equation. The model is parameterized in terms of an unknown quantity, the lifetime of H2O2 against heterogeneous catalytic destruction in the soil. Calculated concentrations are compared with a H2O2 concentration of 30 nmoles/cm3, inferred from the Viking Labeled Release experiment. A significant result of this model is that for a wide range of H2O2 lifetimes (up to 10(5) years), the extinction depth was found to be less than 3 m. The maximum possible concentration in the top 4 cm is calculated to be approximately 240 nmoles/cm3, achieved with lifetimes of greater than 1000 years. Concentrations higher than 30 nmoles/cm3 require lifetimes of greater than 4.3 terrestrial years. For a wide range of H2O2 lifetimes, it was found that the atmospheric concentration is only weakly coupled with soil loss processes. Losses to the soil become significant only when lifetimes are less than a few hours. If there are depths below which H2O2 is not transported, it is plausible that organic compounds, protected from an oxidizing environment, may still exist. They would have been deposited by meteors, or be the organic remains of past life.     

Climatological observations and predicted sublimation rates at Lake Hoare, Antarctica

In December 1985, an automated meteorological station was established at Lake Hoare in the dry valley region of Antarctica. Here, we report on the first year-round observations available for any site in Taylor Valley. This dataset augments the year-round data obtained at Lake Vanda (Wright Valley) by winter-over crews during the late 1960s and early 1970s. The mean annual solar flux at Lake Hoare was 92 W m-2 during 1986, the mean air temperature -17.3 degrees C, and the mean 3-m wind speed 3.3 m s-1. The local climate is controlled by the wind regime during the 4-month sunless winter and by seasonal and diurnal variations in the incident solar flux during the remainder of the year. Temperature increases of 20 degrees-30 degrees C are frequently observed during the winter due to strong f?hn winds descending from the Polar Plateau. A model incorporating nonsteady molecular diffusion into Kolmogorov-scale eddies in the interfacial layer and similarity-theory flux-profiles in the surface sublayer, is used to determine the rate of ice sublimation from the acquired meteorological data. Despite the frequent occurrence of strong winter f?hns, the bulk of the annual ablation occurs during the summer due to elevated temperatures and persistent moderate winds. The annual ablation from Lake Hoare is estimated to have been 35.0 +/- 6.3 cm for 1986.