An assemblage of geoduck clam shells from the marine environment of coastal British Columbia was studied. Shells were cut
and the widths of internal shell growth increments, annuli, were measured from the hinge plate. The largest shells showed
more than one hundred annual increments. Shell growth exhibited juvenile maxima at ontogenetic ages 3–6 years. The growth
maximum was followed by a distinct decline that continued until the death of each individual. Further, this ontogenetic growth
trend was mathematically removed from the data in order to examine growth variations other than ageing. The longest growth
records from the oldest shells were compared to monthly indices of the Pacific Decadal Oscillation (PDO). It was found that
the PDO exerts the strongest influence on the shell growth during the very start of the growing season, in February and March.
We also detected increased magnitude of growth variations towards the end of the 20th century. Similar trends were apparent
in the PDO record. Moreover, the shell specimen displaying the strongest trend of increasing variance had the strongest PDO-linked
regional growth signal. Our results support the view that PDO exerts a governing influence on the biological and ecological
system along Northeast Pacific coastal areas. Incorporation of geoduck shell growth increment analyses into multi-disciplinary
studies dealing with palaeoceanography and archaeology is suggested as a promising future approach. 相似文献
This paper presents the results of a study on Ni(II) removal from water by adsorption using abundant and low-cost volcanic rock grains: Scoria (VSco) and Pumice (VPum), which could be used as an alternative approach to remove potentially harmful metals from contaminated water. Basic process characteristics were determined under batch conditions. The maximum adsorption capacities for Ni(II) on VSco and VPum were found to be 980 and 1187 mg kg−1, respectively. These results were obtained at the optimized conditions of pH (5.0), temperature (24.9 °C), contact time (24 h), adsorbent/solution ratio (1:20), particle size (fine) and with the variation of initial concentrations between 0.5 and 50 mg L−1. Competitive adsorption of Ni(II), Cd(II) and Cu(II) on the adsorbents present in binary as well as ternary mixtures were also compared with the single metal solution. Thus, given that enough volcanic rock grains are provided, Ni(II) ions could be removed even from a metal ion bearing matrix. A number of available models like Lagergren pseudo-first order kinetics, second-order kinetics, intra-particle diffusion and liquid film diffusion were utilized to evaluate the kinetics and the mechanism of the sorption interactions. The results revealed that the pseudo-second order equation best described the kinetics mechanisms of Ni(II) adsorption although the removal process was found to be complex. Moreover, three adsorption models have been evaluated in order to attempt to fit the experimental data, namely the Langmuir, the Freundlich and the Redlich–Peterson isotherm models. It was found that the first two isotherms most closely described the adsorption parameters. 相似文献
Field and petrographic investigations, cathodoluminescence (CL) studies as well as microprobe analyses of major rock-forming minerals were conducted to establish the crystallization processes in the Eppawala carbonatites, Sri Lanka. The well preserved magmatic textures and crystal morphologies combined with the chemistry of apatite, calcite and dolomite indicate two major stages of crystal growth, which were accompanied by dynamic crystallization conditions. Initially, nucleation of apatite, ilmenite and possibly olivine was associated with rapid crystal growth during slow cooling of the carbonatite melt at depth. The heat loss through the roof and crystallization processes induced the development of turbulent convective currents, which in turn prevented further nucleation and growth of crystals and led to the dispersion of these earlier formed crystals within the magma chamber. Then, rapid upward movement of magma along structural weaknesses led to (i) the transport of mineral clusters, (ii) deformation of ilmenite, (iii) fracturing of apatite and (iv) the emplacement of the carbonatite melt as dykes. Here, the conditions were favourable for the simultaneous crystallization of magnetite, calcite and dolomite in a non-turbulent environment. Subsequent subsolidus alteration caused the hydrothermal overprint of the documented mineral assemblages, particularly along grain boundaries. The study demonstrates that detailed textural examinations of carbonatites combined with mineral chemical analyses and CL investigations can reveal the crystallization processes within carbonatite melts. 相似文献
A shellfish toxin investigation along the Chinese coast has recently been conducted using both HPLC and mouse assay methods. The results showed that DSP was widely distributed in different shellfish species in China. 26 out of 89 samples had DTX1 (dinophysistoxin-1) or OA (okadaic acid) but the DSP content in most shellfish samples did not reach the regulatory limit for human consumption adopted in many countries (20 μg/100 g soft tissue). PSP was also found in 5 out of 96 samples along the coast. One sample, Chlamys nobilis from Hong Kong contained high levels of PSP (320 μg STX equivalent/100 g soft tissue), compared to the regulatory limit (80 μg STX equivalent/100 g soft tissue). After the recent outbreak of red tide in Hong Kong waters, three further shellfish samples were collected within 40 days to investigate the impacts of this event. It was shown that high levels of PSP continued to exist in Hong Kong waters. This report provides the first report of DSP and PSP distribution along the Chinese coast. 相似文献
The aim of this study was to quantify climate change impact on future blue water (BW) and green water (GW) resources as well as the associated uncertainties for 4 subbasins of the Beninese part of the Niger River Basin. The outputs of 3 regional climate models (HIRHAM5, RCSM, and RCA4) under 2 emission scenarios (RCP4.5 and RCP8.5) were downscaled for the historical period (1976–2005) and for the future (2021–2050) using the Statistical DownScaling Model (SDSM). Comparison of climate variables between these 2 periods suggests that rainfall will increase (1.7% to 23.4%) for HIRHAM5 and RCSM under both RCPs but shows mixed trends (?8.5% to 17.3%) for RCA4. Mean temperature will also increase up to 0.48 °C for HIRHAM5 and RCSM but decrease for RCA4 up to ?0.37 °C. Driven by the downscaled climate data, future BW and GW were evaluated with hydrological models validated with streamflow and soil moisture, respectively. The results indicate that GW will increase in all the 4 investigated subbasins, whereas BW will only increase in one subbasin. The overall uncertainty associated with the evaluation of the future BW and GW was quantified through the computation of the interquartile range of the total number of model realizations (combinations of regional climate models and selected hydrological models) for each subbasin. The results show larger uncertainty for the quantification of BW than GW. To cope with the projected decrease in BW that could adversely impact the livelihoods and food security of the local population, recommendations for the development of adequate adaptation strategies are briefly discussed. 相似文献
The period between 21 June and 8 October, 2007 (Carrington rotations 2058 to 2061), comprising the Ulysses ecliptic plane crossing, was characterized by low solar activity. Excluding the small solar energetic particle events observed during July, the ion increases observed in the inner heliosphere between 100?keV/n and 10?MeV/n were associated with Corotating Interaction Regions (CIRs). In this work, we investigate CIR-related ion increases using multipoint observations from Ulysses, ACE, and the twin STEREO spacecraft. The ballistic backmapping technique has been used to correlate in situ observations of these spacecraft and remote-sensing observations of coronal holes. Although the radial, longitudinal and latitudinal separation of the spacecraft (except Ulysses) are relatively small, we find discrepancies when a detailed comparison of narrow structures like stream interfaces and CIR-associated shocks is performed. Therefore we concentrate on the two CIR events from day 5 to day 10 of August 2007 and from day 25 to day 31 of August 2007, which lend themselves to a more undisturbed comparison. Using the multi-spacecraft measurements we could determine a radial gradient of 230±30% AU?1, which is consistent with previous results by van Hollebeke et al. (J. Geophys. Res.83, 4723, 1978) of ~?350% AU?1 using Helios and Pioneer data.
We determined experimentally the Nernst distribution coefficient between orthopyroxene and anhydrous silicate melt for trace elements i in the system Na2O–CaO–MgO–Al2O3–SiO2 (NCMAS) along the dry model lherzolite solidus from 1.1 GPa/1,230°C up to 3.2 GPa/1,535°C in a piston cylinder apparatus.
Major and trace element composition of melt and orthopyroxene were determined with a combination of electron microprobe and
ion probe analyses. We provide partitioning data for trace elements Li, Be, B, K, Sc, Ti, V, Cr, Co, Ni, Rb, Sr, Y, Zr, Nb,
Cs, Ba, La, Ce, Sm, Nd, Yb, Lu, Hf, Ta, Pb, U, and Th. The melts were chosen to be boninitic at 1.1 and 2.0 GPa, picritic
at 2.3 GPa and komatiitic at 2.7 and 3.2 GPa. Orthopyroxene is Tschermakitic with 8 mol% Mg-Tschermaks MgAl[AlSiO6] at 1.1 GPa while at higher pressure it has 18–20 mol%. The rare earth elements show a continuous, significant increase in
compatibility with decreasing ionic radius from DLaopx−melt ∼ 0.0008 to DLuopx−melt ∼ 0.15. For the high-field-strength elements compatibility increases from DThopx−melt ∼ 0.001 through DNbopx−melt ∼ 0.0015, DUopx−melt ∼ 0.002, DTaopx−melt ∼ 0.005, DZropx−melt ∼ 0.02 and DHfopx−melt ∼ 0.04 to DTiopx−melt ∼ 0.14. From mathematical and graphical fits we determined best-fit values for D0M1, D0M2, r0M1, r0M2, E0M1, and E0M2 for the two different M sites in orthopyroxene according to the lattice strain model and calculated the intracrystalline
distribution between M1 and M2. Our data indicate extreme intracrystalline fractionation for most elements in orthopyroxene;
for the divalent cations DiM2−M1 varies by three orders of magnitude between DCoM2−M1 = 0.00098–0.00919 and DBaM2−M1 = 2.3–28. Trivalent cations Al and Cr almost exclusively substitute on M1 while the other trivalent cations substitute on
M2; DLaM2−M1 reaches extreme values between 6.5 × 107 and 1.4 × 1016. Tetravalent cations Ti, Hf, and Zr almost exclusively substitute on M1 while U and Th exclusively substitute on M2. Our
new comprehensive data set can be used for polybaric-polythermal melting models along the Earth’s mantle solidus.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
Amber occurrences in Brazil are rare. In this regard, the molecular composition of three such fossil resin samples from Brazilian Cretaceous sedimentary basins has been analyzed to determine the botanical origin of the resins. The samples were collected from the Amazonas (Alter do Chão Formation), Araripe (Santana Formation, Crato Member) and Recôncavo (Maracangalha Formation, Caruaçu Member) basins. The mono-, sesqui- and diterpenoids in the extracts were used as chemosystematic markers when compared with terpenoids in extant conifers. The compounds were mainly diterpenoids and their degradation products from the labdane, podocarpane, pimarane and isopimarane classes, in addition to paraffins, methoxyphenols and carboxylic acids. Tetracyclic diterpenoids such as phyllocladane, kaurenol and kauranol were also present. The biomarker compositions are certainly typical for conifers and, given the absence of triterpenoids and diterpenoids such as ozic acid, angiosperms can be excluded as a botanical source. The absence of phenolic diterpenoids (ferruginol, totarol) and their derivatives excludes podocarpaceous affinities for the ambers from the Amazonas and Araripe basins. The fossil records of the embedding sediments (e.g. Araucariaceae pollen and leaves) support the proposal of an Araucariacae origin for these ambers, but Cupressaceae and Cheirolepidiaceae cannot be excluded. On the other hand, the presence of phyllocladane and kaurane derivatives is evidence for Araucariaceae or Podocarpaceae origins for the amber from the Recôncavo basin, but Cupressaceae cannot be excluded. 相似文献