Reservoir timescales for anthropogenic CO2 in the atmosphere

Non-steady state timescales are complicated and their application to specific geophysical systems requires a common theoretical foundation. We first extend reservoir theory by quantifying the difference between turnover time and transit time (or residence time) for time-dependent systems under any mixing conditions. We explicitly demonstrate the errors which result from assuming these timescales are equal, which is only true at steady state. We also derive a new response function which allows the calculation of age distributions and timescales for well-mixed reservoirs away from steady state, and differentiate between timescales based on gross and net fluxes. These theoretical results are particularly important to tracer-calibrated "box models" currently used to study the carbon cycle, which usually approximate reservoirs as well-mixed. We then apply the results to the important case of anthropogenic CO2 in the atmosphere, since timescales describing its behavior are commonly used but ambiguously defined. All relevant timescales, including lifetime, transit time, and adjustment time, are precisely defined and calculated from data and models. Apparent discrepancies between the current, empirically determined turnover time of 30-60 years and longer model-derived estimates of expected lifetime and adjustment time are explained within this theoretical framework. We also discuss the results in light of policy issues related to global warming, in particular since any comparisons of the "lifetimes" of different greenhouse gases (CO2, CH4, N2O, CFC's etc.) must use a consistent definition to be meaningful.     

Distribution of moderately volatile trace elements in fine-grained chondrule rims in the unequilibrated CO3 chondrite, ALH A77307

The concentrations of Ni, Cu, Zn, Ga, Ge, and Se in five, fine-grained chondrule rims in the highly unequilibrated CO3 chondrite ALH A77307 (3.0) have been determined for the first time by synchrotron X-ray fluorescence (SXRF) microprobe at Brookhaven National Laboratory. These elements are especially useful for tracing the role of condensation and evaporation processes which occurred at moderate temperatures in the solar nebula. Understanding the distribution of moderately volatile elements between matrix and chondrules is extremely important for evaluating the different models for the volatile depletions in chondritic meteorites. The data show that the trace element chemistry of rims on different chondrules is remarkably similar, consistent with data obtained for the major and minor elements by electron microprobe. These results support the idea that rims are not genetically related to individual chondrules, but all sampled the same reservoir of homogeneously mixed dust. Of the trace elements analyzed, Zn and Ga show depletions relative to CI chondrite values, but in comparison with bulk CO chondrites all the elements are enriched by approximately 1.5 to 3.5 x CO. The abundance patterns for moderately volatile elements in ALH A77307 chondrule rims closely mimic those observed in the bulk chondrite, indicating that matrix is the major reservoir for these elements. The close matching of the patterns for the volatile depleted bulk chondrite and enriched matrix is especially striking for Na, which is anomalously depleted in ALH A77307 in comparison with average CO chondrite abundances. The depletion in Na is probably attributable to the effects of leaching in Antarctica. With the exception of Na, the volatile elements show a relatively smooth decrease in abundance as a function of condensation temperature, indicating that their behavior is largely controlled by their volatility.     

再考查深成岩体侵位作用

以前有关深成岩体的侵位研究都试图解释岩体侵位空间如何形成。事实上，幔源岩浆侵位期间在地壳中“制造空间”的途径不外乎；（１）莫霍面降低；（２）地球表面外移。其它的“岩体侵位机制”均是不增加地壳体积的物质迁移作用（ＭＴＰｓ）。得到广泛引用的“同心带状气球膨胀岩体”侵位时的ＭＴＰｓ是岩体附近围岩的韧性流动。这类深成岩体附近可能形成的构造和总应变与岩体的三维形态、接触变质带的宽度以及岩体是否为刺穿底辟有关     

Historical and ecological analysis of coral communities in Castle Harbour (Bermuda) after more than a century of environmental perturbation

The coral reefs in Bermuda's Castle Harbour basin have been subjected to varying anthropogenic stressors for over 100 years. These include restriction of water flow through the construction of a causeway in the late 19th century and an extensive dredging and land reclamation operation during World War II. In the 1970s, disposal of bulk waste commenced at a foreshore reclamation site in Castle Harbour. Since 1996 the waste stream has included blocks of cement-stabilized municipal incinerator ash. This study provides a historical and quantitative ecological review of the Castle Habour reef ecosystem as a case study, assessing the responses of the reef to more than a century of anthropogenic disturbance. Measures of the coral community, flow rates, turbidity and sedimentary regimes suggest the present structure of the coral community largely reflects the impacts of the historic dredge and fill operations prior to the establishment of the foreshore dump site. Recent increases in the abundance of some sediment tolerant, massive reef-building coral species (Diploria strigosa and Montastraea cavernosa) suggest adaptation to chronic sediment stress.     

Mapping water quality and substrate cover in optically complex coastal and reef waters: an integrated approach

Sustainable management of coastal and coral reef environments requires regular collection of accurate information on recognized ecosystem health indicators. Satellite image data and derived maps of water column and substrate biophysical properties provide an opportunity to develop baseline mapping and monitoring programs for coastal and coral reef ecosystem health indicators. A significant challenge for satellite image data in coastal and coral reef water bodies is the mixture of both clear and turbid waters. A new approach is presented in this paper to enable production of water quality and substrate cover type maps, linked to a field based coastal ecosystem health indicator monitoring program, for use in turbid to clear coastal and coral reef waters. An optimized optical domain method was applied to map selected water quality (Secchi depth, Kd PAR, tripton, CDOM) and substrate cover type (seagrass, algae, sand) parameters. The approach is demonstrated using commercially available Landsat 7 Enhanced Thematic Mapper image data over a coastal embayment exhibiting the range of substrate cover types and water quality conditions commonly found in sub-tropical and tropical coastal environments. Spatially extensive and quantitative maps of selected water quality and substrate cover parameters were produced for the study site. These map products were refined by interactions with management agencies to suit the information requirements of their monitoring and management programs.     

Foraminifers as indicators of marine pollution: a culture experiment with Rosalina leei

In order to develop a viable foraminiferal proxy for heavy metal pollutants, juvenile specimens of Rosalina leei were subjected to different mercury concentrations (0-180 ng/l). Initially considerable growth was observed in specimens kept in saline water having a mercury concentration up to 100 ng/l. But with the gradual increase in concentration of mercury the growth rate started decreasing. Total growth achieved was significantly lower in case of specimens kept at relatively higher mercury concentrations then those maintained in normal saline water. The most significant result of this experiment was the addition of abnormal chambers in the specimens kept at higher mercury concentration. Later the specimens kept at highest concentration (180 ng/l) were subjected to progressively increasing concentration of mercury to see the further effects and it was found that the specimens were still living at as high a mercury concentration as 260 ng/l although there was no growth.