Uptake and depuration of PAHs and chlorinated pesticides by semi-permeable membrane devices (SPMDs) and green-lipped mussels (Perna viridis)     

Bruce J. Richardson  Edmund S.-C. Tse  Sharon B. De Luca-Abbott  Michael Martin  Paul K.S. Lam 《Marine pollution bulletin》2005,51(8-12):975

Semi-batch seawater experiments were conducted to follow the uptake and release of selected PAHs (anthracene, fluorathene, pyrene and B[a]P) and organochlorine pesticides (α-HCH, aldrin, dieldrin, p,p′-DDT) in semi-permeable membrane devices (SPMDs) and green-lipped mussels (Perna viridis). Mathematical models were applied to describe the uptake and elimination curves of the contaminants for SPMDs, and kinetic parameters, such as uptake rate constants, and equilibrium triolein/water partitioning coefficients were calculated. SPMD data showed a good fit to estimate rate constant and partition coefficient equations, but only those contaminants which partitioned mainly in the dissolved phase (α-HCH and dieldrin) were well explained for mussels. Poor conformity of the other contaminants indicated mussels uptake by routes other than diffusion, such as ingestion of algae. An apparent equilibrium state was only noted for α-HCH in mussels. Aldrin was not detected in mussels in the first few days of exposure, indicating potential metabolism of this compound. B[a]P was not detected in the triolein of SPMDs, which suggests that the membrane may act as a reservoir. Loss of spiked B[a]P from the triolein was evident in a depuration experiment, which may indicate transfer to the membrane. Rate constants for mussels were higher than those for SPMDs, but the reverse was true for partition coefficients. Overall, mussels and SPMDs had similar uptake rates for all compounds in this study, excluding p,p′-DDT and dieldrin. Contaminant elimination took place more rapidly in mussels, implying that SPMDs are better candidates for detecting episodic discharge of organic contaminants.  相似文献   

Evidence from kimberlitic zircon for a decreasing mantle Th/U since the Archean     

Robert Eugene Zartman  Stephen H. Richardson 《Chemical Geology》2005,220(3-4):263-283

A decoupling in MORB of measured Th/U (κ = 2.5) from that calculated by Pb isotopes (κ = 3.8) for the depleted asthenosphere is well established, and has been referred to as the second Pb paradox (Kramers, J.D., and Tolstikhin, I.N., 1997. Two terrestrial lead isotope paradoxes, forward transport modelling, core formation and the history of the continental crust. Chem. Geol., 139, 75–110.) or the kappa conundrum (Elliott, T., Zindler, A., and Bourdon, B., 1999. Exploring the kappa conundrum: the role of recycling in the lead isotope evolution of the mantle. Earth Planet. Sci. Lett., 169, 129–145.). More controversial has been the cause and timing of this phenomenon, although a higher return flux of U⁶⁺ relative to Th⁴⁺ and(or) the recycling of crustal Pb into the mantle have become the preferred explanations of most workers. Such a combined mechanism effectively operating over the past 2.5 Ga was modelled in plumbotectonics (Zartman, R.E., and Haines, S., 1988. The plumbotectonics model for Pb isotopic systematics among major terrestrial reservoirs—a case for bi–directional transport. Geochim. Cosmochim. Acta, 52, 1327–1339. 709.33.), and found to be quantitatively feasible.A large TIMS, SIMS and LA-ICPMS database of Th and U concentrations for kimberlite-hosted zircon, particularly from Cr-poor megacrystic suites, now exists (Kinny et al., 1989, Berryman et al., 1999, Griffin et al., 2000 and Spetsius et al., 2002; Appendix A and Appendix B, this work). Six suites comprising 10 or more zircon grains with ages between 90 and 2550 Ma reveal consistent patterns when plotted on Th/U vs. U diagrams. We interpret these patterns as resulting from fractional crystallization of a melt with kimberlite affinity presumably derived from the asthenosphere, permitting the extrapolation to an initial Th/U at the time zircon crystallization began. A two-fold decrease is seen in this ratio over the past 2.5 Ga, suggesting that during this time a similar change has occurred in the parent silicate melt. Estimates of Th and U distribution coefficients between zircon and coexisting melt permit calculation of Th/U in the melt, which, for these highly incompatible elements, presumably is the same as for its mantle source rock. Kimberlitic zircon may thus indeed give evidence of a reduction in κ, tentatively calculated as from 4 to 2, since the Archean for the depleted asthenosphere.  相似文献   

Manganese oxidation in pH and O2 microenvironments produced by phytoplankton     

Richardson LL  Aguilar C  Nealson KH 《Limnology and oceanography》1988,33(3):352-363

Pure cultures of Chlorella sp. catalyzed the oxidation of soluble Mn(II) to particulate, extracellular, manganic oxides. Manganese oxidation was dependent on photosynthetic activity: no oxidation was observed in the dark when cells were grown heterotrophically on glucose, or in the light when photosystem II was inhibited by the addition of DCMU. Manganates were not formed when media were buffered below pH 8.0, suggesting that an important driving force for manganese oxidation was the high pH resulting from photosynthesis. Field studies with minielectrodes in Oneida Lake, New York, demonstrated steep gradients of O2 and pH and the presence of particulate manganic oxides associated with pelagic aggregates of the cyanobacterium Microcystis sp. The manganese oxidation reaction apparently occurs only when photosynthesizing algae are present as dense populations that can generate microenvironments of high (>9.0) pH, either as aggregates in the pelagic zone or concentrated cell cultures in the laboratory. A large-scale transition from soluble to particulate manganese was measured in the surface waters of Oneida Lake throughout summer 1986. Removal of Mn(II) was correlated with the presence of aggregate-forming cyanobacteria that oxidize Mn(II) by the mechanism described above.  相似文献   

Regional patterns in the paragenesis and age of inclusions in diamond, diamond composition, and the lithospheric seismic structure of Southern Africa   总被引：1，自引：0，他引：1  

Steven B. Shirey  Jeffrey W. Harris  Stephen H. Richardson  Matthew Fouch  David E. James  Pierre Cartigny  Peter Deines  Fanus Viljoen 《Lithos》2003,71(2-4):243-258

The Archean lithospheric mantle beneath the Kaapvaal–Zimbabwe craton of Southern Africa shows ±1% variations in seismic P-wave velocity at depths within the diamond stability field (150–250 km) that correlate regionally with differences in the composition of diamonds and their syngenetic inclusions. Seismically slower mantle trends from the mantle below Swaziland to that below southeastern Botswana, roughly following the surface outcrop pattern of the Bushveld-Molopo Farms Complex. Seismically slower mantle also is evident under the southwestern side of the Zimbabwe craton below crust metamorphosed around 2 Ga. Individual eclogitic sulfide inclusions in diamonds from the Kimberley area kimberlites, Koffiefontein, Orapa, and Jwaneng have Re–Os isotopic ages that range from circa 2.9 Ga to the Proterozoic and show little correspondence with these lithospheric variations. However, silicate inclusions in diamonds and their host diamond compositions for the above kimberlites, Finsch, Jagersfontein, Roberts Victor, Premier, Venetia, and Letlhakane do show some regional relationship to the seismic velocity of the lithosphere. Mantle lithosphere with slower P-wave velocity correlates with a greater proportion of eclogitic versus peridotitic silicate inclusions in diamond, a greater incidence of younger Sm–Nd ages of silicate inclusions, a greater proportion of diamonds with lighter C isotopic composition, and a lower percentage of low-N diamonds whereas the converse is true for diamonds from higher velocity mantle. The oldest formation ages of diamonds indicate that the mantle keels which became continental nuclei were created by middle Archean (3.2–3.3 Ga) mantle depletion events with high degrees of melting and early harzburgite formation. The predominance of sulfide inclusions that are eclogitic in the 2.9 Ga age population links late Archean (2.9 Ga) subduction-accretion events involving an oceanic lithosphere component to craton stabilization. These events resulted in a widely distributed younger Archean generation of eclogitic diamonds in the lithospheric mantle. Subsequent Proterozoic tectonic and magmatic events altered the composition of the continental lithosphere and added new lherzolitic and eclogitic diamonds to the already extensive Archean diamond suite.  相似文献   

Chemistry of rainfall,throughfall and stemflow in a eucalypt forest and a pine plantation in south-eastern Australia: 1. Rainfall     

R. H. Crockford  D. P. Richardson  R. Sageman 《水文研究》1996,10(1):1-11

Rainfall samples were collected from several hundred rainfall events. Up to nine samples per event were collected from sites 3–500 m apart. They differed substantially in both concentration and composition, even though great care was taken to wash all collectors beforehand. Dryfall, storage and analytical procedures could not explain the variation. When data for rainfall events of similar size (but very different cation inputs) were examined, the major differences were associated with the prevailing wind direction. Events leading to high concentrations were associated with easterly winds and showed the influence of a marine source. Chemical concentration and composition were not altered by the occurrence of a drought year followed by a very wet year. The mean pH was 5·3 and ranged from 4·6 to 5·8. For a given event, a difference of 0·5 often occurred between collection sites. Regular seasonal variations in the concentration of NO₃-N and the NO₃/NH₄ ratio occurred, with the ratio being higher in summer due primarily to bush fires. Organic nitrogen comprised 14% of total nitrogen.  相似文献   

Which way do you lean? Using slope aspect variations to understand Critical Zone processes and feedbacks   总被引：1，自引：0，他引：1       下载免费PDF全文

Jon D. Pelletier  Greg A. Barron‐Gafford  Hugo Gutiérrez‐Jurado  Eve‐Lyn S. Hinckley  Erkan Istanbulluoglu  Luke A. McGuire  Guo‐Yue Niu  Michael J. Poulos  Craig Rasmussen  Paul Richardson  Tyson L. Swetnam  Greg E. Tucker 《地球表面变化过程与地形》2018,43(5):1133-1154

Soil‐mantled pole‐facing hillslopes on Earth tend to be steeper, wetter, and have more vegetation cover compared with adjacent equator‐facing hillslopes. These and other slope aspect controls are often the consequence of feedbacks among hydrologic, ecologic, pedogenic, and geomorphic processes triggered by spatial variations in mean annual insolation. In this paper we review the state of knowledge on slope aspect controls of Critical Zone (CZ) processes using the latitudinal and elevational dependence of topographic asymmetry as a motivating observation. At relatively low latitudes and elevations, pole‐facing hillslopes tend to be steeper. At higher latitudes and elevations this pattern reverses. We reproduce this pattern using an empirical model based on parsimonious functions of latitude, an aridity index, mean‐annual temperature, and slope gradient. Using this empirical model and the literature as guides, we present a conceptual model for the slope‐aspect‐driven CZ feedbacks that generate asymmetry in water‐limited and temperature‐limited end‐member cases. In this conceptual model the dominant factor driving slope aspect differences at relatively low latitudes and elevations is the difference in mean‐annual soil moisture. The dominant factor at higher latitudes and elevations is temperature limitation on vegetation growth. In water‐limited cases, we propose that higher mean‐annual soil moisture on pole‐facing hillslopes drives higher soil production rates, higher water storage potential, more vegetation cover, faster dust deposition, and lower erosional efficiency in a positive feedback. At higher latitudes and elevations, pole‐facing hillslopes tend to have less vegetation cover, greater erosional efficiency, and gentler slopes, thus reversing the pattern of asymmetry found at lower latitudes and elevations. Our conceptual model emphasizes the linkages among short‐ and long‐timescale processes and across CZ sub‐disciplines; it also points to opportunities to further understand how CZ processes interact. We also demonstrate the importance of paleoclimatic conditions and non‐climatic factors in influencing slope aspect variations. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

1500 years of lake sedimentation due to fire,earthquakes, floods and land clearance in the Oregon Coast Range: geomorphic sensitivity to floods during timber harvest period          下载免费PDF全文

K.N.D. Richardson  J.A. Hatten  R.A. Wheatcroft 《地球表面变化过程与地形》2018,43(7):1496-1517

Sediment cores retrieved from landslide‐dammed Loon Lake recorded events back to the 5th century AD in a forested, mountainous catchment, thereby providing an opportunity to compare the impacts of known recent perturbations, including floods and timber harvesting with those of an early period in the cores, floods, fires, and earthquakes. High‐resolution multi‐parameter (grain size, %TC, %TN, and magnetic susceptibility) data allowed the core stratigraphy to be classified as background sedimentation and events. ¹³⁷Cs and radiocarbon dating, as well as a varved record in the last 75 years provided age control. Mean mass accumulation rate from 1939 to 1978 AD, the time of peak timber harvest and a cool wet phase of the Pacific Decadal Oscillation, was 0.79 (0.74–0.92, 95% C.L.) g cm^‐2 y^‐1, significantly higher than mean rates of both the more recent contemporary period (coincident with the passing of the legislation that regulated harvesting practices in the region), 1979–2012 AD, at 0.58 (0.48‐0.70) and the entire early period, 0.44 (0.41–0.46). Several event deposits are coeval with independently estimated ages of eight Cascadia subduction zone earthquakes in the early period, including the 1700 AD Mw 9.0 event. These deposits are predominantly formed by hyperpycnal flows, as are the known event deposits in the contemporary period. The high mass accumulation rate and greater frequency of thick event deposits during the early contemporary period point to the extraordinary role of timber harvesting in priming the landscape for subsequent sedimentary delivery during floods. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Decadal-scale changes in suspended wood after riparian recruitment in managed stands in headwater streams of coastal British Columbia,Canada     

Felipe Rossetti de Paula  John S. Richardson  Alex C.Y. Yeung  Stephen J. Mitchell  Devesh Bahuguna 《地球表面变化过程与地形》2020,45(9):1974-1989

Large wood (LW) affects several ecological and hydrogeomorphic processes in streams. The main source of LW is riparian trees falling inside channels. However, in confined valley floors, falling trees are more likely to be suspended above the channel. Eventually, these suspended trees will decompose and break to finally fall into the channel to better provide functions for streams. We evaluated changes in wood decay, length, diameter, and suspended status (suspended or non-suspended) 17 years post-harvest and nine years after the first sampling occurred in 2006 in 12 headwater streams of coastal British Columbia, Canada. We also evaluated whether changes differed among riparian management treatments (no-harvest buffers of 10 and 30 m in width, thinning, and unharvested reference sites), and identified the factors affecting wood changes and suspended status. Wood pieces advanced in decay, became shorter, and 34% of them (n = 108) changed status from suspended to non-suspended. Non-suspended wood pieces were more decayed and shorter than suspended wood. Suspended wood was longer, thicker, less decayed, and represented 46.5% (n = 147) of the wood sampled in 2006. Our findings revealed limited influences of riparian management on many aspects of wood changes considered in this study. Changes in wood characteristics were more likely for pieces that were smaller in diameter, longer, and suspended closer to the water. The transition from suspended to non-suspended LW can be a long-term process that can increase wood residence time and reduce LW in-stream functions particularly in confined stream valleys. The suspended stage is also an important mechanism underlying time lags in stream ecosystem responses to riparian tree fall. © 2020 John Wiley & Sons, Ltd.  相似文献   

Sailfish (Istiophorus platypterus) spawning and larval environment in a Florida Current frontal eddy     

David E. Richardson  Joel K. Llopiz  Kevin D. Leaman  Peter S. Vertes  Frank E. Muller-Karger  Robert K. Cowen 《Progress in Oceanography》2009,(4):252-264

Fronts and eddies are widely hypothesized to be critical spawning habitat for large pelagic fishes, due to increased larval and/or adult feeding opportunities at these features. We examined sailfish (Istiophorus platypterus) spawning around a cyclonic, submesoscale (∼13 × 7 km) Florida Current frontal eddy. The temporal progression of eddy dynamics over a 65 h period was determined using ocean color satellite imagery, continuous surface measurements along the cruise track, and non-linear least-squares fitting of the positions of three drifters deployed within the eddy. A peak in larval sailfish densities (n = 2435, stations = 49), composed primarily of yolk-sac and first-feeding larvae, occurred at the eddy frontal zone. A majority of these larvae were estimated to have been spawned during the formation of the eddy. A comparison between the distribution of similar-age sailfish and scombrid larvae indicated that the peak in larval sailfish density likely resulted from spawning directly at the front, rather than transport by convergent flow. The first-feeding prey items of larval sailfish (Farranula and Corycaeus copepods) were most abundant at the frontal zone and to a lesser extent inside the eddy. Egg distributions were used to indirectly assess the distribution of adult sailfish prey items. Euthynnus alleteratus and Auxis spp. eggs were in highest abundance outside the eddy, while the eggs of small carangids were in highest abundance at the eddy frontal zone. Overall, this study indicates that sailfish spawn at small-scale oceanographic features that provide a favorable feeding environment for their larvae and potentially also for the adults.  相似文献   

Regime shifts: Can ecological theory illuminate the mechanisms?   总被引：2，自引：0，他引：2  

Jeremy S. Collie  Katherine Richardson  John H. Steele 《Progress in Oceanography》2004,60(2-4):281

“Regime shifts” are considered here to be low-frequency, high-amplitude changes in oceanic conditions that may be especially pronounced in biological variables and propagate through several trophic levels. Three different types of regime shift (smooth, abrupt and discontinuous) are identified on the basis of different patterns in the relationship between the response of an ecosystem variable (usually biotic) and some external forcing or condition (control variable). The smooth regime shift is represented by a quasi-linear relationship between the response and control variables. The abrupt regime shift exhibits a nonlinear relationship between the response and control variables, and the discontinuous regime shift is characterized by the trajectory of the response variable differing when the forcing variable increases compared to when it decreases (i.e., the occurrence of alternative “stable” states). Most often, oceanic regime shifts are identified from time series of biotic variables (often commercial fish), but this approach does not allow the identification of discontinuous regime shifts. Recognizing discontinuous regime shifts is, however, particularly important as evidence from terrestrial and freshwater ecosystems suggests that such regime shifts may not be immediately reversible. Based on a review of various generic classes of mathematical models, we conclude that regime shifts arise from the interaction between population processes and external forcing variables. The shift between ecosystem states can be caused by gradual, cumulative changes in the forcing variable(s) or it can be triggered by acute disturbances, either anthropogenic or natural. A protocol for diagnosing the type of regime shift encountered is described and applied to a data set on Georges Bank haddock, from which it is concluded that a discontinuous regime shift in the abundance of haddock may have occurred. It is acknowledged that few, if any, marine data are available to confirm the occurrence of discontinuous regime shifts in the ocean. Nevertheless, we argue that there is good theoretical evidence for their occurrence as well as some anecdotal evidence from data collection campaigns and that the possibility of their occurrence should be recognized in the development of natural resource management strategies.  相似文献