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71.
72.
Stuart G Wakeham 《Marine pollution bulletin》1976,7(11):206-211
Hydrocarbon distribution in sediments from three lakes are related to the level of human activity in the respective drainage basins. Petroleum hydrocarbon contamination is found in surface sediments of a lake surrounded by a major city, compared to no detectable contamination in a lake located in a National Park. 相似文献
73.
Stuart Hamilton 《水文研究》2007,21(22):3105-3106
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Microbial biomass response to different quantities and sources of organic matter in Brazilian coastal sediments
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Cintia O. Quintana Paula C. de Moraes Marcos Y. Yoshinaga Stuart G. Wakeham Paulo Y. G. Sumida 《Marine Ecology》2015,36(3):766-779
This study investigates the benthic microbial responses to organic matter (OM) variations in quantity and sources in two shallow water bays (Fortaleza and Ubatuba Bays) on the SE coast of Brazil on six occasions during the year. The pelagic and benthic compartments of the bays were evaluated by: (i) nutrients and chlorophyll a (Chl a) in the water column; (ii) quantity and sources of OM in the sediment (Chl a, total organic carbon and total nitrogen and lipid biomarker composition); and (iii) microbial biomass in sediments as an indicator of active benthic response. Although there were changes in water‐column nutrients during the year, Chl a was fairly constant, suggesting a regular supply of microalgae‐derived OM to the sea bottom. Based on the composition of lipid biomarkers in sediments, OM sources were classified as mostly marine and with high contributions of labile (microalgae‐derived) OM. Labile OM composition varied from diatoms in the summer to phytoflagellates in the winter and tended to accumulate in areas protected by physical disturbances in one of the bays. Microbial biomass followed this trend and was 160% higher in protected than in exposed areas. This study suggests that the coupling between labile OM and benthic microbial biomass occurs primarily in protected areas, irrespective of the time of the year. Since meio‐ and macrofaunal assemblages depend upon secondary microbial production within the sediments, this coupling may have an important role for the benthic food‐web. 相似文献
78.
M.E. Stuart L. Maurice T.H.E. Heaton M. Sapiano M. Micallef Sultana D.C. Gooddy P.J. Chilton 《Applied Geochemistry》2010
The Maltese islands are composed of two limestone aquifers, the Upper and Lower Coralline Limestone separated by an aquitard, the ‘Blue Clay’. The Lower Coralline Limestone is overlain in part by the poorly permeable Globigerina Limestone. The upper perched aquifers are discontinuous and have very limited saturated thickness and a short water level response time to rainfall. Frequent detections of coliforms suggest a rapid route to groundwater. However, the unsaturated zone has a considerable thickness in places and the primary porosity of the Upper Coralline Limestone is high, so there is likely to be older recharge by slow matrix flow as well as rapid recharge from fractures. Measurement of SF6 from a pumping station in a deep part of one of the perched aquifers indicated a mean saturated zone age of about 15 a. The Main Sea Level aquifers (MSL) on both Malta and Gozo have a large unsaturated thickness as water levels are close to sea level. On Malta, parts of the aquifer are capped by the perched aquifers and more extensively by the Globigerina Limestone. The limited detection of coliform bacteria suggests only some rapid recharge from the surface via fractures or karst features. Transmissivity is low and 3H and CFC/SF6 data indicate that saturated zone travel times are in the range 15–40 a. On Gozo the aquifer is similar but is more-extensively capped by impermeable Blue Clay. CFC data show the saturated zone travel time is from 25 a to possibly more than 60 a. Groundwater age is clearly related to the extent of low-permeability cover. The δ13C signature of groundwater is related to the geochemical processes which occur along the flowpath and is consistent with residence time ages in the sequence; perched aquifers < Malta MSL < Gozo MSL. The 18O and 2H enriched isotopic signature of post 1983 desalinated water can be seen in more-modern groundwater, particularly the urbanized areas of the perched and Malta MSL aquifers. In all aquifers, movement of solutes from the surface travelling slowly through the matrix provide a long-term source of groundwater contaminants such as NO3. 相似文献
79.
Stuart J. Mills Anthony R. Kampf Mati Raudsepp William D. Birch 《Mineralogy and Petrology》2010,100(3-4):249-253
Sr- and Ca-rich waylandite, $ {\left( {{\hbox{B}}{{\hbox{i}}_{0.{54}}}{\hbox{S}}{{\hbox{r}}_{0.{31}}}{\hbox{C}}{{\hbox{a}}_{0.{25}}}{{\hbox{K}}_{0.0{1}}}{\hbox{B}}{{\hbox{a}}_{0.0{1}}}} \right)_{\Sigma 1.12}}{{\hbox{H}}_{0.{18}}}{\left( {{\hbox{A}}{{\hbox{l}}_{{2}.{96}}}{\hbox{C}}{{\hbox{u}}_{0.0{2}}}} \right)_{\Sigma 2.98}}{\left[ {{{\left( {{{\hbox{P}}_{0.{97}}}{{\hbox{S}}_{0.0{3}}}{\hbox{S}}{{\hbox{i}}_{0.0{1}}}} \right)}_{\Sigma 1.00}}{{\hbox{O}}_4}} \right]_2}{\left( {\hbox{OH}} \right)_6} $ , from Wheal Remfry, Cornwall, United Kingdom has been investigated by single-crystal X-ray diffraction and electron microprobe analyses. Waylandite crystallises in space group R $ \overline 3 $ ? m, with the cell parameters: a?=?7.0059(7) Å, c?=?16.3431(12) Å and V?=?694.69(11) Å3. The crystal structure has been refined to R 1?=?3.76%. Waylandite has an alunite-type structure comprised of a rhombohedral stacking of (001) composite layers of corner-shared AlO6 octahedra and PO4 tetrahedra, with (Bi,Sr,Ca) atoms occupying icosahedrally coordinated sites between the layers. 相似文献
80.
Thermochronometric constraints on the tectonic evolution of the Serifos detachment, Aegean Sea, Greece 总被引:1,自引:0,他引:1
Stephanie Brichau Stuart Thomson Uwe Ring 《International Journal of Earth Sciences》2010,99(2):379-393
We constrain the timing and kinematics of the Serifos detachment in the southwestern Cyclades, Greece, using low-temperature
thermochronometry. Fission-track dating shows that the Serifos detachment was active between ~13 and 6 Ma and that the Serifos
granodiorite in its footwall intruded at or before ~12–11 Ma into the extensional shear zone and initially cooled very rapidly
at rates >180°C per million year. The mylonite zone at the top of the granodiorite and mylonitic structures in its country
rocks record a consistent top-SSW shear sense in the ductile crust. In the brittle regime top-NNE shear-sense indicators occur
as well. Conjugate top-SSW and top-NNE high-angle normal faults are the youngest deformational features and cut across the
detachment. Age–distance relationships for the fission-track data display a relatively flat pattern. We discuss a model advocating
initial top-SSW movement on the Serifos detachment before and during emplacement of the granodiorite. Updoming of the detachment
during exhumation and cooling caused subsequent bivergent extension in the brittle crust. 相似文献