Drying effects on sorption capacity of coastal sediment: The importance of architecture and polarity of organic matter     

Zhanfei Liu  Cindy Lee 《Geochimica et cosmochimica acta》2006,70(13):3313-3324

Investigations on how desiccation changes sorption of organic compounds by salt marsh sediments provide insight into the physical and chemical properties of these wide-spread coastal sediments. We measured sorption of compounds with different polarities (lysine, tyrosine, naphthalene and aniline) onto natural sediments and sediments that were dried and rewetted. Sorption of lysine by marsh sediment decreased significantly when the sediment was dried using a freeze-drier, oven, or desiccator, and sorption capacity was not restored when sediments were rewetted. In contrast to lysine, the sorption capacity of more hydrophobic compounds (tyrosine, aniline and naphthalene) increased significantly after salt marsh sediment was dried. These results suggest that drying greatly increased sediment hydrophobicity. Consistently, water drop penetration time, an index of hydrophobicity, was significantly lower for combusted sediments than for those that were simply dried. Sediments treated with EDTA, or boiled in seawater, exhibited a similar or even greater reduction in lysine sorption capacity compared with sediments that were dried. Water retention capacity of salt marsh sediment decreased 50% after sediment was dried. The effects of pH and salinity on lysine sorption in wet and dry sediments suggest that carboxyl groups play a major role in lysine sorption through cation ion exchange, and drying may reduce access to carboxyl groups. We hypothesize that the three-dimensional (3D) structure of organic matter, originating mainly from Spartina alterniflora, is an important factor controlling sorption capacity in salt marsh sediment. The drying process makes sedimentary organic matter change conformation, shrink in volume, and expose hydrophobic groups, thus becoming more hydrophobic. In environments with wet and dry cycles, the distribution of hydrophobic or hydrophilic compounds between solution and particulate phases could thus be influenced by the 3D structure and polarity of organic matter.  相似文献   

Preservation of organic matter in mound-forming coral skeletons     

Anitra E Ingalls  Cindy Lee 《Geochimica et cosmochimica acta》2003,67(15):2827-2841

This study demonstrates that intracrystalline organic matter in coral skeletons is well preserved over century timescales. The extent of preservation of organic matter in coral skeletons was investigated by measuring total organic carbon (TOC), total hydrolyzable amino acid (THAA), chloropigment, and lipid concentrations in 0-300 year old annual growth bands from Montastraea annularis (Florida Keys) and Porites lutea (Red Sea). Organic matter intrinsic to the calcium carbonate mineral (intracrystalline) was analyzed separately from total skeletal organic matter. The Red Sea coral had less TOC (0.02-0.04 wt%) than the Florida Keys coral (0.04-0.11 wt%), but a higher percent of intracrystalline organic matter in all annual bands measured. Carbon in the form of THAA, most likely from mineral-precipitating proteins, contributed 30-45% of the TOC in both corals. Carbon in lipids represented about 3% of the TOC in the coral skeletons. Chlorophyll-a and b were present in annual bands where endolithic algae were present, but these compounds were minor contributors to TOC. The distribution of specific organic compounds showed that organic matter was well preserved throughout the time period sampled in both the total and intracrystalline pools. Variations in THAA were not correlated with TOC over time, suggesting that organic matter that is involved in biomineralization, like amino acids, may be deposited in response to different environmental factors than are other components of skeletal organic matter. Differences in the quantity and composition of organic matter between the two corals investigated here were assessed using principal components analysis and suggest that location, species and skeletal structure may all influence organic matter content and possibly the degree of physical protection of organic matter by the coral skeleton. Further, our study suggests that intracrystalline organic matter may be better protected from diagenesis than non-intracrystalline organic matter and may therefore be a more reliable source of organic matter for paleoceanographic studies than total skeletal organic matter.  相似文献   

GIS Spatial-Temporal Modeling of Water Systems in Greater Toronto Area, Canada   总被引：2，自引：0，他引：2  

ChengQiuming ZhangGeorge LuCindy KoConnie 《中国地质大学学报(英文版)》2004,15(3):275-282

Modeling landscape with high-resolution digital elevation model (DEM) in a geographic information system can provide essential morphological and structural information for modeling surface processes such as geomorphologic process and water systems. This paper introduces several DEM-based spatial analysis processes applied to characterize spatial distribution and their interactions of ground and surface water systems in the Greater Toronto Area (GTA), Canada. The stream networks and drainage basin systems were derived from the DEM with 30 m resolution and the regularities of the surface stream and drainage patterns were modeled from a statistical/multifractal point of view. Together with the elevation and slope of topography, other attributes defmed from modeling the stream system, and drainage networks were used to associate geological, hydrological and topographical features to water flow in river systems and the spatial locations of artesian aquifers in the study area. Stream flow data derived from daily flow measurements recorded at river gauging stations for multi-year period were decomposed into “drainage-area dependent“ and “drainage-area independent“ flow components by two-step “frequency“ and “spatial“ analysis processes. The latter component was further demonstrated to relate most likely to the ground water discharge. An independent analysis was conducted to model the distribution of aquifers with information derived from the records of water wells. The focus was given on quantification of the likelihood of ground water discharge to river and ponds through flowing wells, springs and seepages. It has been shown that the Oak Ridges Moraine (ORM) is a unique glacial deposit that serves as a recharge layer and that the aquifers in the ORM underlain by Hilton Tills and later deposits exposed near the steep slope zone of the ridges of ORM provide significant discharge to the surface water systems (river flow and ponds) through flowing wells, springs and seepages. Various statistics (cross- and auto-correlation coefficients, fractal R/S exponent) were used in conjunction with GIS to demonstrate the influence of land types, topography and geometry of drainage basins on short- and long-term persistence of river flows as well as responding time to precipitation events. The current study has provided not only insight in understanding the interaction of water systems in the GTA, but also a base for further establishment of an on-line GIS system for predicting spatial-temporal changes of river flow and groundwater level in the GTA.  相似文献   

Major goal achieved with major GAMs     

by Robert E. Mace  Cindy Ridgeway 《Ground water》2005,43(2):163-163

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Erratum to: Linking the thermal evolution and emplacement history of an upper-crustal pluton to its lower-crustal roots using zircon geochronology and geochemistry (Southern Adamello Batholith,N. Italy)     

Cindy Broderick  Jörn F. Wotzlaw  Daniel A. Frick  Axel Gerdes  Alex Ulianov  Detlef Günther  Urs Schaltegger 《Contributions to Mineralogy and Petrology》2016,171(3):27

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Amino acids in equatorial Pacific Ocean water     

Cindy Lee  Jeffrey L. Bada 《Earth and Planetary Science Letters》1975,26(1):61-68

Seawater samples from the Eastern Equatorial Pacific Ocean were analyzed for amino acids by a ligand-exchange chromatography technique. The results showed that dissolved free amino acids make up only 0.3% of DOC, much less than has been previously reported for open ocean waters. Substantially larger amounts of combined amino acids are present, however. Concentration variations of the combined amino acid fraction in the water column suggest their potential use as a water mass indicator.  相似文献   

Si–C interactions during degradation of the diatom Skeletonema marinoi     

Brivaëla Moriceau  Madeleine Goutx  Catherine Guigue  Cindy Lee  Robert Armstrong  Marie Duflos  Christian Tamburini  Bruno Charrire  Olivier Ragueneau 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(18):1381-1395

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Subtropical montane evergreen broad-leaved forests of Yunnan, China: diversity, succession dynamics, human influence     

Cindy Q. Tang 《Frontiers of Earth Science》2010,4(1):22-32

This paper integrates studies on the natural subtropical montane evergreen broad-leaved forests (EBLFs) and secondary succession of the forests and plantations in Yunnan, to provide a basis for evaluating the sustainability of the forests in the mountain ecosystems of Yunnan, China. The EBLFs include mid-montane moist, monsoon, and semi-humid categories. The monsoon EBLF yielded the highest indices of the Shannon-Wiener H, Equitability J, Simpson D and Fisher’s alpha, followed by the mid-montane moist EBLF, then by the semi-humid forest. Since human uses have varied widely, the plant communities ranged from pioneer deciduous broad-leaved and/or pioneer coniferous stands to late-successional evergreen broad-leaved stands. The secondary succession pathways were from pioneer deciduous stands of Alnus accompanied by stands of pioneer coniferous Pinus and Keteleeria, through broad-leaved and coniferous mixed stands, to late-successional evergreen broad-leaved forests of Cyclobalanopsis and Castanopsis. In Yunnan, the EBLF is commonly replaced by plantations of exotic fast-growing Eucalyptus to produce industrial wood, oil, pulp and fuel. The result has been reduced plant diversity, and great loss of soil nutrients by erosion and runoff, as compared to the EBLF. Seventy-six plant species in the area have been ranked as critically endangered, endangered, or vulnerable. Their condition is seen as largely attributable to habitat loss or degradation. A clear understanding of ecological features and succession pathways of the EBLF can lead to more effective conservation and management of these fragile forests and the mountain ecosystems.  相似文献   

Comparison of seismic activity for Llaima and Villarrica volcanoes prior to and after the Maule 2010 earthquake     

Cindy Mora-Stock  Martin Thorwart  Tina Wunderlich  Stefan Bredemeyer  Thor H. Hansteen  Wolfgang Rabbel 《International Journal of Earth Sciences》2014,103(7):2015-2028

Llaima and Villarrica are two of the most active volcanoes in the Chilean Southern Volcanic Zone and presently show contrasting types of activity. Llaima is a closed vent edifice with fumarolic activity, while Villarrica has an open vent with a lava lake, continuous degassing and tremor activity. This study is focused on characterizing the relationships between volcanic and seismic activity in the months before and after the 2010 M8.8 Maule earthquake, which was located in NNW direction from the volcanoes. Time series for tremors, long-period and volcano-tectonic events were obtained from the catalogue of the Volcanic Observatory of the Southern Andes (OVDAS) and from the SFB 574 temporary volcanic network. An increase in the amount of tremor activity, long-period events and degassing rates was observed at Villarrica weeks before the mainshock and continued at a high level also after it. This increase in activity is interpreted to be caused by enhanced magma influx at depth and may be unrelated to the Maule event. In Llaima, an increase in the volcano-tectonic activity was observed directly after the earthquake. The simultaneous post-earthquake activity at both volcanoes is consistent with a structural adjustment response. Since this enhanced activity lasted for more than a year, we suggest that it is related to a medium-term change in the static stress. Thus, the Maule earthquake may have affected both volcanoes, but did not trigger eruptions, from which we assume that none of the volcanoes were in a critical state.  相似文献   

Sampling the vertical particle flux in the upper water column using a large diameter free-drifting NetTrap adapted to an Indented Rotating Sphere sediment trap     

Michael L. Peterson  Joan Fabres  Stuart G. Wakeham  Cindy Lee  Ivn J. Alonso  Juan Carlos Miquel 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(18):1547-1557

Further development of the large, surface-tethered sediment trap (NetTrap) employed as part of the MedFlux program is described whereby the large collection capacity of the NetTrap is combined with an Indented Rotating Sphere/Sample Carousel (IRSC) sediment trap (IRSC–NT). This trap is capable of collecting particle flux either in a time series or settling velocity mode; settling velocity mode allows the collection of particles that fall within discrete settling velocity intervals. During short field deployments in the Mediterranean Sea the IRSC–NT configured in the settling velocity mode successfully collected unpoisoned samples for chemical and microbiological experiments. In addition to the development of the IRSC–NT, particle-settling behavior above and below the swimmer-excluding IRS valve was tested during on-deck experiments using a specially constructed water-tight trap. Chemical analyses of settling materials (published elsewhere) suggested that separation of particles by settling velocity was achieved. However, due to the motion of the ship, it was not possible to directly measure particle-settling velocities within the trap. Particle release from the IRS did not bias the apparent settling velocity spectrum. Rotation of the IRS did not engender turbulence at the surface of the sphere or within the skewed funnel below. Tests of different ball designs over the course of the MedFlux program showed that a “ridge and saddle” pattern was optimal for efficiently transferring particles under the IRS seal while still reducing swimmer entrance to the collection funnel. The large size of the IRSC–NT did not prevent it from drifting effectively with the current. Several modifications of the present design are proposed that should improve the accuracy of the settling velocity measurements.  相似文献