Endolithic biodegradation of cool-water skeletal carbonates on Scott shelf, northwestern Vancouver Island, Canada     

Harvey R. Young  Campbell S. Nelson 《Sedimentary Geology》1988,60(1-4):251-267

Biodegradation of shell material is widespread in the cool-water skeletal carbonate deposits on Scott shelf, northwestern Vancouver Island, and is especially evident in the large aragonitic bivalves, Glycymeris and Humilaria, major primary sediment contributors. Ten types of endolithic microborings have been identified in the shells, including representatives of green algae (e.g., Ostreobium quekettii), blue-green algae (e.g., Plectonema terebrans, ?Scytonema sp.), fungi, bacteria and clionid sponges, as well as macroborings of phoronids, polychaetes and naticid gatropods. Microcrystalline carbonate is not precipitated in vacated bores. Boring physically weakens the shells, rendering them more prone to mechanical abrasion during sediment transport and bioturbation, and to biological abrasion by grazing benthos. Tumbling experiments demonstrate that the rate of carbonate mud production is much greater for bored as compared to fresh bivalve shells, and that mud production rates decrease with tumbling time because most endolithic microborings are confined to the periphery of grains. Boring also increases significantly the porosity and surface area of skeletal grains, and destroys their organic matrix, making them susceptible to maceration and dissolution on cool-water shelves. Fostered by the generally low rates of carbonate production and accumulation, many aragonitic bivalve shells on Scott shelf have become thoroughly degraded through a combination of endolithic microboring, maceration and dissolution within about 1000 years in ambient sea water. In geologic terms, such selective taphonomic loss of skeletal material may be considerable in ancient temperate-shelf limestones and should be evaluated when interpreting their paleoecology and paleoenvironments.  相似文献   

El Nino/Southern oscillation signals in the global tropical ocean     

Fu Congbin  Dong Dongfeng  Ralph Slutz  Joseph Fletcher 《大气科学进展》1988,5(1):35-46

The monthly mean sea surface temperature data of 6 areas are used to study the El Nino/Southern Oscillation signals in the global tropical ocean. These areas are in the 5oN-5oS latitude zone at 1) eastern Pacific (110o-l40oW), 2) western Atlantic (30o-50oW), 3) eastern Atlantic (10oW-10oE), 4) western Indian Ocean (30o-50oE), 5) central Indian Ocean (70o-90oE) and 6) far western Pacific (120o-140oE), and the data cover the 120-month period of December 1968 to November 1978.A power spectrum analysts shows that the characteristic time of the El Nino/Southern Oscillation (about 3-4 years) appears not only in the eastern Pacific but also in other areas of the tropics except for the western Pa-cific, where the spectrum is of white noise. The amplitude of oscillation in the eastern Pacific is about 4 times larger than the others, making the El Nino/Southern Oscillation signal the strongest in this area. According to a cross-spectrum analysis, there is no time lag between the variation in the central Indian Ocean and that in the eastern Pacific. These two areas oscillate simultaneously and comprise the main feature of the El Nino/ Southern Oscillation. Other tropical areas are related with time lags, as shown by correlation and coherence calculations.It should be noted that the sea surface temperature in the eastern Pacific oscillates in phase with that in the Indian Ocean, while the pressure oscillations in these two areas are out of phase with each other, according to the Southern Oscillation definition. It is suggested that the Southern Oscillation cannot be explained simply by the sea surface temperature anomalies.Variations in the far western equatorial Pacific do not have the time scale of the El Nino/Southern Oscilla-tion, perhaps because it is a buffer zone between the monsoon system and the trade wind system.  相似文献   

Mercury,arsenic, antimony,and selenium contents of sediment from the Kuskokwim River,Bethel, Alaska,USA   总被引：1，自引：0，他引：1  

Harvey E. Belkin  Harold M. Sparck 《Environmental Geology》1993,22(2):106-110

The Kuskokwim River at Bethel, Alaska, drains a major mercury-antimony metallogenic province in its upper reaches and tributaries. Bethel (population 4000) is situated on the Kuskokwim floodplain and also draws its water supply from wells located in river-deposited sediment. A boring through overbank and floodplain sediment has provided material to establish a baseline datum for sediment-hosted heavy metals. Mercury (total), arsenic, antimony, and selenium contents were determined; aluminum was also determined and used as normalizing factor. The contents of the heavy metals were relatively constant with depth and do not reflect any potential enrichment from upstream contaminant sources.  相似文献   

Petrology     

Ralph Kretz 《Earth》1991,30(3-4):328-329

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Book review     

L. D. Danny Harvey 《Climatic change》1994,28(4):405-410

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Book reviews     

Boulding  Kenneth E.  Rosenberg  Norman J.  Harvey  L. D. Danny 《Climatic change》1985,7(4):461-466

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Book reviews     

Philip Rasch  L. D. Danny Harvey  R. G. Barry 《Climatic change》1987,10(2):201-206

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Estimates of CO2 from wood fuel based on forest harvest data     

Ralph M. Rotty 《Climatic change》1986,9(3):311-325

Wood continues to be a major fuel source for vast numbers of the world's people. Even in the highly industrialized countries, use of wood and wood wastes as fuel produces a small (in comparison to fossil fuels) but non-negligible amount of CO₂. Although information on the worldwide harvest and use of wood is not as complete or as reliable as fossil fuel data, this paper uses what is available and develops annual estimates of CO₂ emissions for the period 1968–1983. Woods are separated into two types, coniferous and non-coniferous, and average content and carbon amounts are estimated for each type. Wood utilization is divided into several categories, e.g., fuelwood, lumber, poles, and use of wood wastes as fuels in the lumber and paper industries is included. Results are given for major world regions. In recent years the worldwide CO₂ emissions from wood used as fuels is estimated to be about one-tenth as much as CO₂ emissions from fossil fuels. This does not include fires in the forests, either associated with forest clearing or those from natural causes.  相似文献   

Solar-hydrogen electricity generation in the context of global CO2 emission reduction     

L. D. Danny Harvey 《Climatic change》1995,29(1):53-89

The relative costs and CO₂ emission reduction benefits of advanced centralized fossil fuel electricity generation, hybrid photovoltaic-fossil fuel electricity generation, and total solar electricity generation with hydrogen storage are compared. Component costs appropriate to the year 2000–2010 time frame are assumed throughout. For low insolation conditions (160 W m^–2 mean annual solar radiation), photovoltaic electricity could cost 5–13 cents/kWh by year 2000–2010, while for high insolation conditions (260 W m^–2) the cost could be 4–9 cents/kWh. Advanced fossil fuel-based power generation should achieve efficiencies of 50% using coal and 55% using natural gas. Carbon dioxide emissions would be reduced by a factor of 2 to 3 compared to conventional coal-based electricity production in industrialized countries. In a solar-fossil fuel hybrid, some electricity would be supplied from solar energy whenever the sun is shining and remaining demand satisfied by fossil fuels. This increases total capital costs but saves on fuel costs. For low insolation conditions, the costs of electricity increases by 0–2 cents/kWh, while the cost of electricity decreases in many cases for high insolation conditions. Solar energy would provide 20% or 30% of electricity demand for the low and high insolation cases, respectively. In the solar-hydrogen energy system, some photovoltaic arrays would provide current electricity demand while others would be used to produce hydrogen electrolytically for storage and later use in fuel cells to generate electricity. Electricity costs from the solar-hydrogen system are 0.2–5.4 cents/kWh greater than from a natural gas power plant, and 1.0–4.5 cents/kWh greater than from coal plant for the cost and performance assumptions adopted here. The carbon tax required to make the solar-hydrogen system competitive with fossil fuels ranges from $70–660/tonne, depending on the cost and performance of system components and the future price of fossil fuels.Leakage of hydrogen from storage into the atmosphere, and the eventual transport of a portion of the leaked hydrogen to the stratosphere, would result in the formation of stratospheric water vapor. This could perturb stratospheric ozone amounts and contribute to global warming. Order-of-magnitude calculations indicate that, for a leakage rate of 0.5% yr^–1 of total hydrogen production -which might be characteristic of underground hydrogen storage - the global warming effect of solarhydrogen electricity generation is comparable to that of a natural gas-solar energy hybrid system after one year of emission, but is on the order of 1% the impact of the hybrid system at a 100 year time scale. Impacts on stratospheric ozone are likely to be minuscule.  相似文献   

Creating a global warming implementation regime     

LD Danny Harvey 《Global Environmental Change》1995,5(5)

This paper proposes a global warming implementation regime which addresses the issues of equity, flexibility, cost minimization, and population growth. Previously proposed international policy instruments, such as country by country targets, carbon taxes, and tradable permits, face major difficulties as stand alone proposals. The key element of the regime proposed here is to combine annual tradable permits which are allocated based on population in a fixed year with a small carbon tax ($5–10/tonne) on emissions in excess of permits. Both permits and carbon taxes are applied to national level governments, which in turn would use whatever mix of policies desired to reduce national emissions. It is suggested that the initial number of permits correspond to total global emissions in the base year; over time, the number of permits could be reduced and the tax rate increased if improved scientific knowledge so dictates. By allocating permits based on population the equity concerns of developing countries are addressed, while taxing emissions in excess of permit holdings removes the rigidity of a quota system and limits resource transfers by effectively capping the permit trading price, which is a major concern of industrialized countries. To accommodate the difficulties of countries which have not yet achieved the demographic transition, the permit allocation scheme could be subject to a one-time adjustment after 10–15 years based on some weighting of the initial and then-current populations. The proposed scheme is based on the premise that there is a large potential for reducing emissions in developed countries or limiting emission increases in developing countries, and the intention is to create competition between national level governments in implementing cost-effective emission reduction.  相似文献