Calibration of diatoms along a nutrient gradient in Florida Everglades Water Conservation Area-2A, USA   总被引：2，自引：0，他引：2  

Sherri R. Cooper  Jacqueline Huvane  Panchabi Vaithiyanathan  Curtis J. Richardson 《Journal of Paleolimnology》1999,22(4):413-437

The relationship between diatom taxa preserved in surface soils and environmental variables at 31 sites in Water Conservation Area 2A (WCA-2A) of the Florida Everglades was explored using multivariate analyses. Surface soils were collected along a phosphorus (P) gradient and analyzed for diatoms, total P, % nitrogen (N), %carbon (C), calcium (Ca), and biogenic silica (BSi). Phosphorus varied from 315-1781 g g^-1, and was not found to be correlated with the other geochemical variables. Canonical correspondence analysis (CCA) was used to examine which environmental variables correlated most closely with the distributions in diatom taxa. Canonical correspondence analysis with forward selection, constrained and partial CCA, and Monte Carlo permutation tests of significance show the most significant changes in diatom assemblages along the P gradient (p < 0.01), with additional species differences correlated with soil C, N, Ca, and BSi.Weighted-averaging (WA) regression and calibration models of diatom assemblages to P and BSi were developed. The diatom-based inference model for soil [P] had a high apparent r² (0.86) with RMSE_boot = 218 g g^-1. Indicator diatom species identified by assessing species WA optima and WA tolerance to [P], such as Nitzschia amphibia and N. palea for high [P] (~1300-1400 g^-1) and Achnanthes minutissima var. scotica and Mastogloia smithii for low [P] (~400-600 g g^-1), may be useful as monitoring tools for eutrophication in WCA-2A as well as other areas of the Everglades. Diatom assemblages analyzed by cluster analysis were related to location within WCA-2A, and dominant taxa within clusters are discussed in relation to the geochemical variables measured as well as hydrology and pH. Diversity of diatom assemblages and a Disturbance Index based on diatom data are discussed in relation to the historically P-limited Everglades ecosystem. Diatom assemblages should be very useful for reconstructions of [P] through time in the Florida Everglades, provided diatoms are well preserved in soil cores.  相似文献   

Space physics: The study of plasmas in space: R. L. F. Boyd. Clarendon Press,Oxford, 1974. $11.25.     

F. Curtis Michel 《Icarus》1976,29(3):437

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Stability of minerals in surface weathering reactions: A general thermochemical approach     

C. D. Curtis 《地球表面变化过程与地形》1976,1(1):63-70

A list of formational free energy data is provided for a range of common rock forming minerals. Free energy changes accompanying their decomposition to realistic stable products are calculated and shown to be in agreement with persistence observations. Weathering mechanisms and environmental controls are discussed.  相似文献   

Photodegradation of pharmaceuticals in the aquatic environment: A review   总被引：6，自引：0，他引：6  

Anne?L.?Boreen  William?A.?ArnoldEmail author  Kristopher?McNeillEmail author 《Aquatic Sciences - Research Across Boundaries》2003,65(4):320-341

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Influence of vegetation change on watershed hydrology: implications for paleoclimatic interpretation of lacustrine δ18O records     

Michael F. Rosenmeier  David A. Hodell  Mark Brenner  Jason H. Curtis  Jonathan B. Martin  Flavio S. Anselmetti  Daniel Ariztegui  Thomas P. Guilderson 《Journal of Paleolimnology》2002,27(1):117-131

Stratigraphic shifts in the oxygen isotopic (¹⁸O) and trace element (Mg and Sr) composition of biogenic carbonate from tropical lake sediment cores are often interpreted as a proxy record of the changing relation between evaporation and precipitation (E/P). Holocene ¹⁸O and Mg and Sr records from Lakes Salpetén and Petén Itzá, Guatemala were apparently affected by drainage basin vegetation changes that influenced watershed hydrology, thereby confounding paleoclimatic interpretations. Oxygen isotope values and trace element concentrations in the two lowland lakes were greatest between ~ 9000 and 6800 ¹⁴C-yr BP, suggesting relatively high E/P, but pollen data indicate moist conditions and extensive forest cover in the early Holocene. The discrepancy between pollen- and geochemically-inferred climate conditions may be reconciled if the high early Holocene ¹⁸O and trace element values were controlled principally by low surface runoff and groundwater flow to the lake, rather than high E/P. Dense forest cover in the early Holocene would have increased evapotranspiration and soil moisture storage, thereby reducing delivery of meteoric water to the lakes. Carbonate ¹⁸O and Mg and Sr decreased between 7200 and 3500 ¹⁴C-yr BP in Lake Salpetén and between 6800 and 5000 ¹⁴C-yr BP in Lake Petén Itzá. This decline coincided with palynologically documented forest loss that may have led to increased surface and groundwater flow to the lakes. In Lake Salpetén, minimum ¹⁸O values (i.e., high lake levels) occurred between 3500 and 1800 ¹⁴C-yr BP. Relatively high lake levels were confirmed by ¹⁴C-dated aquatic gastropods from subaerial soil profiles ~ 1.0–7.5 m above present lake stage. High lake levels were a consequence of lower E/P and/or greater surface runoff and groundwater inflow caused by human-induced deforestation.  相似文献   

Trace-element distribution and ore formation in vein-metasomatised peridotite at Kalskaret,near Tafjord,South Norway     

R. Kanaris-Sotiriou  F. G. F. Gibb  D. A. Carswell  C. D. Curtis 《Contributions to Mineralogy and Petrology》1978,67(3):289-295

The concentration profiles of the trace elements, S, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Sr, and Y have been determined across a metasomatic vein in peridotite. The introduced elements Ti, V, Sr, and Y show specific enrichment in particular silicate phases in accordance with the availability of suitable lattice sites. In contrast, the other introduced trace elements (Cu and S) behave more like the redistributed elements, Cr, Ni, Mn, and Co which do not show concentration ‘fronts’ that can be simply related to the silicate minerals. Concentration of pentlandite, chalcopyrite, and Cr-magnetite near the boundary between the enstatite and anthophyllite zones gives rise to maxima in the Ni, Cu, S, and Cr distributions, while in the chlorite zone significant concentrations of Cr and Ni occur in the chlorite itself. Control of the distribution of Ni, Cu, and Cr is ascribed to the oxidation/reduction reactions involved in the formation of pentlandite, chalcopyrite and Cr-magnetite, together with the critical role of Al in limiting chlorite formation during metasomatism.  相似文献   

Aspects of the population dynamics of the polychaeteSabellaria vulgaris Verrill,in the Delaware Bay     

Lawrence A. Curtis 《Estuaries and Coasts》1978,1(2):73-84

Aspects of the population dynamics of the polychaeteSabellaria vulgaris Verrill 1874 were studied by observing the temporal occurrence of larvae in the plankton of Delaware Bay. Vertical plankton samples were collected monthly from July 1970 to October 1971. Four 25-hour plankton studies were conducted within this time period, and on one occasion samples were collected on a transect across the mouth of the bay.Sabellaria vulgaris larvae were present in the bay only from mid-April through October. July (1970) and August (1971) 25-hour plankton studies showed larvae present in the water column at virtually all times of the day and night. Horizontal dispersion of larvae in the plankton was clearly aggregated. However, correlation of larval presence, absence or abundance with the measured physical factors in the estuary was not apparent except on a seasonal scale. Six developmental stages were defined based upon observation of laboratory-reared larvae. Young larvae appeared in the plankton on numerous occasions, indicating that spawning occurred repeatedly during the April–October time period in Delaware Bay. Relative to other habitats within the geographic range ofS. vulgaris, Delaware Bay is a particularly well-suited environment for the construction of massive colonies by the species. Adults living in large aggregates would exhibit greater fitness because of the higher probability of eggs being fertilized. Indications are that a portion of the larvae produced in the Bay are retained in the estuary and undergo settlement there. Delaware Bay may be a population center for the species. A comparison of reproductive phenomena among sabellariid species is presented. It is apparent that the species,S. vulgaris, consists of several physiologically distinct populations, and that this is true of certain other sabellariid species as well.  相似文献   

The Persian gulf: holocene carbonate sedimentation and diagenesis in a shallow epicontinental sea: B.H. PURSER, ed. (1973): 471 pp. 250 figs. and folding maps. Berlin—Heidelberg—New York: Springer Verlag. DM 66,-, US$ 29.80     

Karl Butzer  Curtis Larsen 《Geoforum》1974,5(4):104

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Temporal Evolution of the Solar-Wind Electron Core Density at Solar Minimum by Correlating SWEA Measurements from STEREO A and B     

A. Opitz  J.-A. Sauvaud  A. Fedorov  P. Wurz  J. G. Luhmann  B. Lavraud  C. T. Russell  P. Kellogg  C. Briand  P. Henri  D. M. Malaspina  P. Louarn  D. W. Curtis  E. Penou  R. Karrer  A. B. Galvin  D. E. Larson  I. Dandouras  P. Schroeder 《Solar physics》2010,266(2):369-377

The twin STEREO spacecraft provide a unique tool to study the temporal evolution of the solar-wind properties in the ecliptic since their longitudinal separation increases with time. We derive the characteristic temporal variations at ～?1 AU between two different plasma parcels ejected from the same solar source by excluding the spatial variations from our datasets. As part of the onboard IMPACT instrument suite, the SWEA electron experiment provides the solar-wind electron core density at two different heliospheric vantage points. We analyze these density datasets between March and August 2007 and find typical solar minimum conditions. After adjusting for the theoretical time lag between the two spacecraft, we compare the two density datasets. We find that their correlation decreases as the time difference increases between two ejections. The correlation coefficient is about 0.80 for a time lag of a half day and 0.65 for two days. These correlation coefficients from the electron core density are somewhat lower than the ones from the proton bulk velocity obtained in an earlier study, though they are still high enough to consider the solar wind as persistent after two days. These quantitative results reflect the variability of the solar-wind properties in space and time, and they might serve as input for solar-wind models.  相似文献   

A submillimetre survey of the kinematics of the Perseus molecular cloud – I. Data     

Emily I. Curtis  John S. Richer  Jane V. Buckle 《Monthly notices of the Royal Astronomical Society》2010,401(1):455-472

We present submillimetre observations of the   J = 3 → 2  rotational transition of ¹²CO, ¹³CO and C¹⁸O across over 600 arcmin² of the Perseus molecular cloud, undertaken with the Heterodyne Array Receiver Programme (HARP), a new array spectrograph on the James Clerk Maxwell Telescope. The data encompass four regions of the cloud, containing the largest clusters of dust continuum condensations: NGC 1333, IC348, L1448 and L1455. A new procedure to remove striping artefacts from the raw HARP data is introduced. We compare the maps to those of the dust continuum emission mapped with the Submillimetre Common-User Bolometer Array (SCUBA; Hatchell et al.) and the positions of starless and protostellar cores (Hatchell et al.). No straightforward correlation is found between the masses of each region derived from the HARP CO and SCUBA data, underlining the care that must be exercised when comparing masses of the same object derived from different tracers. From the ¹³CO/C¹⁸O line ratio the relative abundance of the two species  ([¹³CO]/[C¹⁸O]∼ 7)  and their opacities (typically τ is 0.02–0.22 and 0.15–1.52 for the C¹⁸O and ¹³CO gas, respectively) are calculated. C¹⁸O is optically thin nearly everywhere, increasing in opacity towards star-forming cores but not beyond  τ₁₈∼ 0.9  . Assuming the ¹²CO gas is optically thick, we compute its excitation temperature, T _ex (around 8–30 K), which has little correlation with estimates of the dust temperature.  相似文献