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81.
Is Ocean Acidification an Open-Ocean Syndrome? Understanding Anthropogenic Impacts on Seawater pH 总被引:2,自引:0,他引:2
Carlos M. Duarte Iris E. Hendriks Tommy S. Moore Ylva S. Olsen Alexandra Steckbauer Laura Ramajo Jacob Carstensen Julie A. Trotter Malcolm McCulloch 《Estuaries and Coasts》2013,36(2):221-236
Ocean acidification due to anthropogenic CO2 emissions is a dominant driver of long-term changes in pH in the open ocean, raising concern for the future of calcifying organisms, many of which are present in coastal habitats. However, changes in pH in coastal ecosystems result from a multitude of drivers, including impacts from watershed processes, nutrient inputs, and changes in ecosystem structure and metabolism. Interaction between ocean acidification due to anthropogenic CO2 emissions and the dynamic regional to local drivers of coastal ecosystems have resulted in complex regulation of pH in coastal waters. Changes in the watershed can, for example, lead to changes in alkalinity and CO2 fluxes that, together with metabolic processes and oceanic dynamics, yield high-magnitude decadal changes of up to 0.5 units in coastal pH. Metabolism results in strong diel to seasonal fluctuations in pH, with characteristic ranges of 0.3 pH units, with metabolically intense habitats exceeding this range on a daily basis. The intense variability and multiple, complex controls on pH implies that the concept of ocean acidification due to anthropogenic CO2 emissions cannot be transposed to coastal ecosystems directly. Furthermore, in coastal ecosystems, the detection of trends towards acidification is not trivial and the attribution of these changes to anthropogenic CO2 emissions is even more problematic. Coastal ecosystems may show acidification or basification, depending on the balance between the invasion of coastal waters by anthropogenic CO2, watershed export of alkalinity, organic matter and CO2, and changes in the balance between primary production, respiration and calcification rates in response to changes in nutrient inputs and losses of ecosystem components. Hence, we contend that ocean acidification from anthropogenic CO2 is largely an open-ocean syndrome and that a concept of anthropogenic impacts on marine pH, which is applicable across the entire ocean, from coastal to open-ocean environments, provides a superior framework to consider the multiple components of the anthropogenic perturbation of marine pH trajectories. The concept of anthropogenic impacts on seawater pH acknowledges that a regional focus is necessary to predict future trajectories in the pH of coastal waters and points at opportunities to manage these trajectories locally to conserve coastal organisms vulnerable to ocean acidification. 相似文献
82.
Heidi Moe Odd Sture Hopperstad Anna Olsen Østen Jensen Arne Fredheim 《Ocean Engineering》2009,36(12-13):992-1002
Creep in materials and structures may lead to increasing strains, permanent deformations, change in mechanical properties and rupture at loads significantly smaller than the breaking strength. In this paper, we present data on temporary-creep properties, recovery of strain post creep and post-creep tensile properties of a selection of Raschel knitted netting materials. Creep strain in wet netting materials subjected to a creep target load of 10–90% of average force at break for 30 min varied from 1.6% to 3.5%. The rate of creep decreased with time and decreased target load. The recovery of strain post creep was relatively fast and approximately half of the creep strain was elastic. Post-creep tensile testing showed that the length and force at break were not significantly affected by the creep load history. However, due to permanent deformations of the specimens from the creep test, the nominal breaking strain decreased and the stiffness increased with increased creep target load. 相似文献
83.
84.
Olsen GH Smit MG Carroll J Jæger I Smith T Camus L 《Marine environmental research》2011,72(4):179-187
Reliable risk assessment approaches for Arctic environments are requested to manage potential impacts associated with increased activities in Arctic regions. We performed toxicity tests on Arctic and temperate species exposed to the narcotic acting oil component, 2-methyl naphthalene. The experimental results were used to quantify concentration causing lethality to 50% of exposed individuals and no-effect concentration (individual level). For estimates at community level, the hazardous concentrations affecting 5% and 50% of the species were calculated from sensitivity distribution curves. These survival metrics were then used to elucidate whether temperate toxicity data used in risk assessment are sufficiently representative for the Arctic. Taking data uncertainty into consideration, we found no regional difference in tolerances to 2-methyl naphthalene either at the species level or at the community level. Hence these data support a conclusion that values of survival metrics for temperate regions are transferrable to the Arctic for the chemical 2-methyl naphthalene, as long as extrapolation techniques are properly applied and uncertainties are taken into consideration. 相似文献
85.
Lars A. Olsen Tonci Balic-Zunic Emil Makovicky Angela Ullrich Ronald Miletich 《Physics and Chemistry of Minerals》2007,34(7):467-475
A single-crystal sample of galenobismutite was subjected to hydrostatic pressures in the range of 0.0001 and 9 GPa at room temperature using the diamond-anvil cell technique. A series of X-ray diffraction intensities were collected at ten distinct pressures using a CCD equipped 4-circle diffractometer. The crystal structure was refined to R1(|F0| > 4σ) values of approximately 0.05 at all pressures. By fitting a third-order Birch-Murnaghan equation of state to the unit-cell volumes V 0 = 700.6(2) Å3, K 0 = 43.9(7) GPa and dK/dP = 6.9(3) could be determined for the lattice compression. Both types of cations in galenobismutite have stereochemically active lone electron pairs, which distort the cation polyhedra at room pressure. The cation eccentricities decrease at higher pressure but are still pronounced at 9 GPa. Galenobismutite is isotypic with CaFe2O4 (CF) but moves away from the idealised CF-type structure during compression. Instead of the two octahedral cation sites and one bi-capped trigonal-prismatic site, PbBi2S4 attains a new high-pressure structure characterised by one octahedral site and two mono-capped trigonal-prismatic sites. Analyses of the crystal structure at high pressure confirm the preference of Bi for the octahedral site and the smaller one of the two trigonal-prismatic sites. 相似文献
86.
87.
88.
Long-period (30 days1 year) electromagnetic sounding and the electrical conductivity of the lower mantle beneath Europe 总被引:5,自引:0,他引:5
Nils Olsen 《Geophysical Journal International》1999,138(1):179-187
The C -response connects the magnetic vertical component and the horizontal gradient of the horizontal components of electromagnetic variations and forms the basis for deriving the conductivitydepth profile of the Earth. Time-series of daily mean values at 42 observatories typically with 50 years of data are used to estimate C -responses for periods between 1 month and 1 yr. The Z : Y method is applied, which means that the vertical component is taken locally whereas the horizontal components are used globally by expansion in a series of spherical harmonics.
In combination with results from previous analyses, the method yields consistent results for European observatories in the entire period range from a few hours to 1 yr, corresponding to penetration depths between 300 and 1800 km.
1-D conductivity models derived from these results show an increase in conductivity with depth z to about 2 S m-1 at z =800 km, and almost constant conductivity between z =800 and z =2000 km with values of 310 S m-1 , in good agreement with laboratory measurements of mantle material. Below 2000 km the conductivity is poorly resolved. However, the best-fitting models indicate a further increase in conductivity to values between 50 and 150 S m-1 . 相似文献
In combination with results from previous analyses, the method yields consistent results for European observatories in the entire period range from a few hours to 1 yr, corresponding to penetration depths between 300 and 1800 km.
1-D conductivity models derived from these results show an increase in conductivity with depth z to about 2 S m
89.
P. Linsalata H. J. Simpson C. R. Olsen N. Cohen R. M. Trier 《Environmental Geology》1985,7(4):193-204
Isotopes of plutonium (Pu), cesium (Cs), and cobalt (Co) introduced into the Hudson River Estuary from fallout deposition,
the erosion of fallout-contaminated surface soils, and nuclear reactor effluent (isotopes of Cs and Co only) have been measured
in water column samples collected from 1975 to 1980 Isotopic measurements conducted independently by two research groups utilizing
different sampling and analytical techniques have been summarized. The major conclusions drawn from the work are that for
water samples collected by the two laboratories over similar time periods, the mean concentrations of nonfilterable239,240Pu (<0.45 μm) were identical at 0.13 fCi/l, mean concentrations of both137Cs and239,240Pu in suspended particulates were more divergent at 2,270±920 pCi/kg (±1 SD) and 1,430±430 pCi/kg for137Cs, and 19±8 pCi/kg and 12±4 pCi/kg for239,240Pu
The behavior of239,240Pu and137Cs within the water column is shown to diverge within brackish waters Specifically, the magnitude of the137Cs distribution coefficient (K
d
) can be expressed as an inverse power function of the chloride ion concentrations for chlorinities between 0.1 and 4 g Cl−/l No difference in the239,240PuK
d
has been observed between fresh and brackish waters
Based on the expected inventories of239,240Pu and137Cs within watershed soils, the current downstream transport of these radionuclides represents fractional mobilization rates
on the order of 1–4 (×10−4) per year 相似文献
90.
Abstract— The Eagle enstatite chondrite (presently 9.2 kg) was an observed fall in October 1946. It was not recovered until the spring of 1947 and was allowed to remain out-of-doors until 1984. The meteorite appears relatively unweathered, although the absence of oldhamite and the depletion of calcium indicates it has suffered chemical weathering during its 37 years of exposure. Its bulk composition classifies it as an EL6. Its lack of chondrules or remnants of chondrules place it among the most recrystallized of enstatite chondrites. It contains unusual rounded black inclusions, up to 1 cm, composed of the same minerals as the host, but of significantly finer grain size. We conclude Eagle is a post-metamorphic breccia, the breccia inclusions having been rounded by abrasion during regolith processing. 相似文献