20th-century industrial black carbon emissions altered Arctic climate forcing   总被引：1，自引：0，他引：1  

McConnell JR  Edwards R  Kok GL  Flanner MG  Zender CS  Saltzman ES  Banta JR  Pasteris DR  Carter MM  Kahl JD 《Science (New York, N.Y.)》2007,317(5843):1381-1384

Black carbon (BC) from biomass and fossil fuel combustion alters chemical and physical properties of the atmosphere and snow albedo, yet little is known about its emission or deposition histories. Measurements of BC, vanillic acid, and non-sea-salt sulfur in ice cores indicate that sources and concentrations of BC in Greenland precipitation varied greatly since 1788 as a result of boreal forest fires and industrial activities. Beginning about 1850, industrial emissions resulted in a sevenfold increase in ice-core BC concentrations, with most change occurring in winter. BC concentrations after about 1951 were lower but increasing. At its maximum from 1906 to 1910, estimated surface climate forcing in early summer from BC in Arctic snow was about 3 watts per square meter, which is eight times the typical preindustrial forcing value.  相似文献   

Changes in mean concentration, phase shifts, and dissipation in a forced oscillatory reaction   总被引：2，自引：0，他引：2  

J G Lazar  J Ross 《Science (New York, N.Y.)》1990,247(4939):189-192

Experiments are presented that confirm earlier predictions that the mode of supply of reactants to a nonlinear (bio)chemical reaction determines or controls concentrations at steady states far from equilibrium. The oxidation of nicotinamide adenine dinucleotide (NADH) catalyzed by the enzyme horseradish peroxidase with continuous input of oxygen was studied; NAD+ is continuously recycled to NADH through a glucose-6-phosphate dehydrogenase system. A comparison of steady-state concentrations is made with an oscillatory oxygen input and a constant input at the same average oxygen input for both modes. By varying the frequency and amplitude of the perturbation (O2 influx), the following may be changed: the average concentration of NADH; the Gibbs free energy difference delta G of the reactants and products at steady state; the average rate of the reaction; the phase relation between the oscillatory rate and delta G; and the dissipation. These results confirm the possibility of an "alternating current chemistry," of control and optimization of thermodynamic efficiency and dissipation by means of external variation of constraints in classes of nonlinear reactions and biological pumps, and of improvements of the yield in such reactions (heterogeneous catalysis, for example).  相似文献   

Bright Spots, Structure, and Magmatism in Southern Tibet from INDEPTH Seismic Reflection Profiling   总被引：8，自引：0，他引：8  

LD Brown  W Zhao  KD Nelson  M Hauck  D Alsdorf  A Ross  M Cogan  M Clark  X Liu  J Che 《Science (New York, N.Y.)》1996,274(5293):1688-1690

INDEPTH seismic reflection profiling shows that the decollement beneath which Indian lithosphere underthrusts the Himalaya extends at least 225 kilometers north of the Himalayan deformation front to a depth of approximately 50 kilometers. Prominent reflections appear at depths of 15 to 18 kilometers near where the decollement reflector apparently terminates. These reflections extend north of the Zangbo suture to the Damxung graben of the Tibet Plateau. Some of these reflections have locally anomalous amplitudes (bright spots) and coincident negative polarities implying that they are produced by fluids in the crust. The presence of geothermal activity and high heat flow in the regions of these reflections and the tectonic setting suggest that the bright spots mark granitic magmas derived by partial melting of the tectonically thickened crust.  相似文献   

Fighting liverflukes with food safety education     

Ziegler AD  Andrews RH  Grundy-Warr C  Sithithaworn P  Petney TN 《Science (New York, N.Y.)》2011,331(6015):282-283

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Evidence for a phytotoxic hydroxy-aluminum polymer in organic soil horizons     

Hunter D  Ross DS 《Science (New York, N.Y.)》1991,251(4997):1056-1058

The toxicity of A1 that has been mobilized in soil, streams, and lakes through acid deposition primarily has been attributed to mononuclear A1 species. Polynuclear A1 species are more toxic than mononuclear species, but they have not been considered to be significant in the environment. Aluminum-27 nuclear magnetic resonance (NMR) spectra of forested spodosol soil horizon samples show the presence of polynuclear A1O(4)A1(12)(OH)(24)(H(2)O)(12)(7+). The AlO(4)A1(12)(OH)(24)(H(2)O)(12)(7+) species accounted for 30 percent of the aqueous A1 observable by NMR, and this could make a significant contribution to the toxicity of the A1 in these soils.  相似文献   

A reverse keystone species affects the landscape distribution of woodland avifauna: a case study using the Noisy Miner (<Emphasis Type="Italic">Manorina melanocephala</Emphasis>) and other Australian birds     

Rebecca M. Montague-Drake  David B. Lindenmayer  Ross B. Cunningham  John A. Stein 《Landscape Ecology》2011,26(10):1383-1394

We explored the effects of a purported ‘reverse keystone species’, the Noisy Miner (Manorina melanocephala) using a long-term, large-scale dataset. Specifically, we identify whether this aggressive bird affects the landscape distribution patterns of other avifauna, by displacing them into, or restricting their distribution to, less productive areas, and in so doing, adheres to ‘isoleg theory’. We sought to determine the effect of abundance of the Noisy Miner on the abundance of other birds (individual species and groups), and determine whether that effect was consistent with varying site productivity, using a negative binomial distribution with a logarithmic link function, and an offset variable to account for variations in search effort. Relationships between abundance of Noisy Miners and habitat variables were examined using a Poisson distribution with a logarithmic link function scaled for extra-variation (quasi-Poisson regression). We demonstrate that when Noisy Miner abundance is low, many small passerine species are more abundant on high productivity sites. However, as Noisy Miner abundance increases, small passerine abundance decreases, with this decrease most apparent on productive sites. The same patterns were not evident for birds considered ‘non-competitors’ of the Noisy Miner. We identify that both site productivity and vegetation structure influence the abundance of the Noisy Miner. We reveal that the species increasingly tolerates ‘less desirable’ habitat attributes with increasing site productivity. The preference of the Noisy Miner for productive areas is likely to have deleterious impacts on the long-term survival and reproductive success of other Australian woodland bird species, many of which have already undergone severe declines.  相似文献   

Optimizing competitive uses of water for irrigation and fisheries     

Lap Doc Tran  Steven SchilizziMorteza Chalak  Ross Kingwell 《Agricultural Water Management》2011,101(1):42-51

Choosing the appropriate reservoir water management strategy can be difficult when the water has multiple uses. This study examines this problem for reservoir managers where water use involves irrigation and fisheries. A stochastic dynamic programming (SDP) model is developed to facilitate reservoir management, using a case study illustration for southern Vietnam. The model includes the response of rice and fish yields to key factors including reservoir water levels, the timing and quantity of water release, and climatic conditions. The model also accounts for variation in rainfall patterns, irrigation requirements, and the demand for low water levels during the fish harvest season. Three production scenarios are examined where the reservoir's water is used for: only producing rice (scenario 1), only producing fish (scenario 2), and producing rice and fish (scenario 3). Key findings are: (1) for scenario 1, adequate water should be released to meet rice growing water requirements and residual water should be stored as a source of water in case of low rainfall, (2) for scenario 2, sufficient water needs to be released prior to the fish harvest to maximize this harvest; and (3) for scenario 3, water should be released prior to fish harvest, but sufficient water should remain to satisfy the water requirements of rice. When the reservoir is managed for joint production of rice and fish, net benefits are 6% greater than when the reservoir is managed solely for rice production. The SDP model developed in this paper could be adapted and applied to other multiple-use resources such as forests, river basins, and land.  相似文献   

Earthworms in New Zealand sheep- and dairy-grazed pastures with focus on anecic Aporrectodea longa     

Nicole L. Schon  Alec D. Mackay  Ross A. Gray  Maria A. Minor 《Pedobiologia》2011

Earthworms play an important role as primary decomposers in the incorporation and initial mixing of plant litter. This study explored the response of earthworms to increasing fertiliser inputs, pasture production and livestock numbers (and their influence on food availability and soil physical condition) on six different managements in sheep-grazed and fifteen different managements in dairy-grazed pastures in a variety of New Zealand soils.Native earthworms were only found in some low-fertility pastures. Accidentally introduced peregrine earthworms, when present, dominate pasture soils. Of these, endogeic earthworms dominated the earthworm community and were positively associated with soil types with higher bulk densities. Peregrine anecic earthworms were absent from most hill-country sheep-grazed pastures, however in more fertile and productive dairy-grazed pastures they reached a biomass of up to 2370 kg ha^?1. Only anecic earthworms showed a positive response to the increasing pressures associated with higher potential dry matter inputs and liveweight loadings of grazing livestock on soil, while epigeic earthworms declined. The positive response of anecic earthworms probably reflects the combined effect of the increase in food resources, including dung and plant litter, available on the soil surface, and their lower susceptibility to livestock treading pressure. Anecic species may be a suitable substitute for incorporation of surface litter in those soils where livestock treading limits epigeic earthworm populations.This study confirmed previous observations of limited distribution of the introduced Aporrectodea longa in pastoral hill-country soils in the North Island, and their near absolute absence from the South Island of New Zealand. This would suggest that large areas of New Zealand pastoral farmed soils could benefit from the introduction of anecic species from other parts of New Zealand which already contain A. longa.  相似文献   

Field and incubation temperature effects on mobilization of nitrogen,phosphorus and potassium in peat     

S.M. Ross 《Soil biology & biochemistry》1985,17(4):479-482

Calluna-derived, amorphous H-horizon material from a peaty ferric stagnopodzol was incubated at two constant temperatures: 6° and 20°C and at two fluctuating temperatures: alternating days at 6° and 20°C and at field fluctuating temperatures. After 3 weeks, amounts of mobilized N, P and K at 6°, 20°C and field temperatures were higher than before incubation. Incubated peat at temperatures of 6° and 20°C on alternating days for 3 weeks produced smaller amounts of deionized-distilled water-extractable NH₄⁺-N, P and K than before incubation. For N, P and K, incubation at constant high temperature (20°C) produced similar amounts of mobilized nutrients compared to field surface soil temperatures.The magnitude of deionized-distilled water-extractable N and P in experimental treatments followed a similar sequence: 6°C incubation > field temperatures > 20°C incubation > before incubation > imposed fluctuating 6° and 20°C temperatures. For K, the mobilization sequence was slightly different: 6° incubation > 20°C incubation > field temperatures > before incubation > imposed fluctuation 6° and 20°C temperatures.  相似文献   

Changes in biochemical activities of soil incubated with the nematicides oxamyl and fenamiphos     

D.J. Ross  T.W. Speir 《Soil biology & biochemistry》1985,17(1):123-125

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