The Mid-Atlantic Ridge at 33°N: the Hayes Fracture Zone     

R.H. Feden  H.S. Fleming  R.K. Perry  J.D. Phillips 《Earth and Planetary Science Letters》1975,26(3):292-298

A geophysical study was conducted over the Mid-Atlantic Ridge between 32–39°N and 30–40°W. A particularly deep fracture was observed which offset the ridge crest 110 km in the vicinity of 33°N. A pole of relative motion between the North American and African plates was deduced from this fracture zone as being at 63.1°N, 17°W.  相似文献   

Modeling of Trace Organics Biotransformation in the Subsurface   总被引：1，自引：0，他引：1  

Edward J. Bouwer  Perry L. McCarty 《Ground water》1984,22(4):433-440

Biofilm processes are potentially important for transformations of organic micropollutants in ground water. Some theoretical hypotheses and empirical observations suggest that a concentration threshold exists for some compounds below which the concentration cannot be reduced by bacterial action. However, in the presence of one compound at a relatively high concentration, termed the primary substrate, another compound present at trace concentrations, termed the secondary substrate, can be biotransformed as well. These concepts were evaluated through laboratory column studies with several halogenated organic compounds of importance in ground water. A biofilm model can successfully describe utilization of trace substrates, and application to modeling the subsurface is discussed. A simplified batch model with first-order kinetics may be adequate for describing subsurface microbial processes when low active organism and pollutant concentrations exist over a large scale.  相似文献   

Contributions of phytoplankton and nitrifying bacteria to ammonium and nitrite dynamics in coastal waters     

B.B. Ward  M.C. Talbot  M.J. Perry 《Continental Shelf Research》1984,3(4):383-398

Ammonium and nitrite dynamics in coastal waters off Washington were examined using stable nitrogen isotope methods. Assimilation rates of ammonium into particulate nitrogen exhibited maxima (up to 500 nmol l⁻¹d⁻¹ at shallow depths and were negligible below the photic zone. Rates of ammonium oxidation by nitrifying bacteria showed surface minima and increased with depth (up to 35 nmol l⁻¹ d⁻¹). Both processes showed evidence of control by light intensity: light stimulated assimilation and inhibited oxidation. Ammonium turnover was dominated by phytoplankton assimilation at shallow depths and at inshore stations, while the relative contribution of bacterial oxidation of ammonium to turnover increased with increasing depth and increasing distance from shore. Nitrite turnover due to ammonium oxidation approached 60% per day in the primary nitrite maximum at the outer stations.  相似文献   

Experimental studies in natural groundwater recharge dynamics: Assessment of recent advances in instrumentation     

Marios Sophocleous  Charles A. Perry   《Journal of Hydrology》1984,70(1-4):369-382

To quantify and model the natural groundwater-recharge process, two sites in south-central Kansas, U.S.A., were instrumented with various modern sensors and data microloggers. The atmospheric-boundary layer and the unsaturated and saturated soil zones were monitored as a unified regime. Data from the various sensors were collected using microloggers in combination with magnetic-cassette tape, graphical and digital recorders, analog paper-tape recorders, and direct observations to evaluate and automate data collection and processing.

Atmospheric sensors included an anemometer, a tipping-bucket raingage, an air-temperature thermistor, a relative-humidity probe, a net radiometer, and a barometric-pressure transducer. Sensors in the unsaturated zone consisted of soil-temperature thermocouples, tensiometers coupled with pressure transducers and dial gages, gypsum blocks, and a neutron moisture probe operated by an observer. The saturated-zone sensors consisted of a water-level pressure transducer, a conventional float gage connected to a variable potentiometer, soil thermocouples, and a number of multiple-depth piezometers.

Evaluation of the operation of these sensors and recorders indicated that certain types of equipment such as pressure transducers are very sensitive to environmental conditions. Extraordinary steps had to be taken to protect some of the equipment, whereas other equipment seemed to be reliable under all conditions. Based on such experiences, a number of suggestions aimed at improving such investigations are outlined.  相似文献   

Review of factors affecting the distribution and abundance of waterfowl in shallow-water habitats of Chesapeake Bay     

Matthew C. Perry  Amy S. Deller 《Estuaries and Coasts》1996,19(2):272-278

Long-term trends of waterfowl populations in Chesapeake Bay demonstrate the importance of shallow-water habitats for waterfowl species. Although recent increases in field feeding by geese and swans lessened the importance of shallow-water areas for these species, most duck species depend almost exclusively on shallow-water habitats. Many factors influenced the distribution and abundance of waterfowl in shallow-water habitats. Habitat degradation resulted in the decline in numbers of most duck species and a change in distribution of some species. Increased numbers of mallards (Anas platyrhynchos) in recent decades probably resulted from release programs conducted by the Maryland Department of Natural Resources and private individuals. Studies of food habits since 1885 showed a decline in submerged-aquatic vegetation in the diet of some species, such as the canvasback (Aythya valisineria), and an increase in the proportions of invertebrates in the diet. Diversity of food organisms for many waterfowl species has declined. Surveys of vegetation and invertebrates in the Chesapeake Bay generally reflect a degradation of shallow-water habitat. Human population increases in the Chesapeake Bay watershed directly and indirectly affected waterfowl distribution and abundance. The increase of exotic plant and invertebrate species in the bay, in most cases, benefited waterfowl populations. Increased contaminants have reduced the quality and quantity of habitat, although serious attempts to reverse this trend are underway. The use of shallow-water habitats by humans for fishing, hunting, boating, and other recreational and commercial uses reduced the use of shallow-water habitats by waterfowl. Humans can lessen the adverse influences on the valuable shallow-water habitats by restricting human population growth near these habitats and improving the water quality of the bay tributaries. Other affirmative actions that will improve these areas for waterfowl include greater restrictions on boat traffic in shallow-water habitats and establishing more sanctuaries in shallow-water areas that have complete protection from human disturbance. *** DIRECT SUPPORT *** A01BY074 00013  相似文献   

Public Awareness of and Visitation to National Parks by Racial/Ethnic Minorities     

Xiao Xiao  Robert Manning  Elizabeth Perry  William Valliere 《社会与自然资源》2018,31(8):908-924

National parks are an important manifestation of the United States’ democratic ideal and attract more than 300 million visits annually. However, racial/ethnic minorities are substantially underrepresented among visitors, and this has led to three hypotheses—marginality, subculture, and discrimination—designed to help explain this pattern of visitation. Moreover, research suggests that the awareness of and visitation to national parks may relate to several variables, including race/ethnicity, socio-economic characteristics, and childhood visitation history. To investigate these issues, an online general population survey of New York City residents was conducted. Study findings suggest that (1) racial/ethnic minorities are underrepresented at some types of parks but not others, (2) Hispanics and Blacks generally have lower rates of awareness about national parks than Whites, and (3) awareness and childhood visitation history significantly affect visitation to national parks. These findings suggest potential approaches to enable and encourage diverse racial/ethnic groups to engage with national parks.  相似文献   

Coastal Resident Trust,Similarity, Attitudes,and Intentions Regarding New Marine Reserves in Oregon     

Elizabeth E. Perry  Lori A. Cramer 《社会与自然资源》2017,30(3):315-330

This article examined coastal resident attitudes and behavioral intentions associated with new marine reserves (MRs) in Oregon, as well as resident perceived similarity and trust in the lead managing agency (Oregon Department of Fish and Wildlife). Data were obtained from a survey of residents along the Oregon coast (n?=?596). Most residents perceived moderate similarity and trust in the agency, had stronger attitudes toward potential advantages of MRs, and would vote in support for the establishment of these reserves. Those living nearest the reserves had the most positive attitudes and were most supportive. Residents who perceived themselves as similar to the agency were more likely to trust this agency, and those with higher trust had stronger attitudes toward advantages of MRs and less agreement with disadvantages of the reserves. Residents with stronger attitudes toward advantages were most likely to vote for MRs, whereas those who agreed with disadvantages were less supportive.  相似文献   

Carbon limitation of sediment bacterial production and denitrification in high nitrate low carbon systems     

Brian D. Grebliunas  William L. Perry 《Environmental Earth Sciences》2016,75(8):662

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Grain susceptibility to the effects of microboring: implications for the preservation of skeletal carbonates   总被引：2，自引：0，他引：2  

Christopher T. Perry 《Sedimentology》1998,45(1):39-51

The boring activity of microendolithic organisms such as cyanobacteria, chlorophytes, rhodophytes and fungi, represents a major destructive process affecting sediment preservation within reef environments. This study demonstrates the presence of two distinct assemblages of microborers within sediments collected from the fringing reefs of north Jamaica, correlating to the upper (<18 m depth) and lower (>18 m depth) photic zones. The upper photic zone assemblage is dominated by cyanobacteria and chlorophytes, whilst rhodophytes and fungi become more abundant with increasing water depth. Most significant from a grain preservation perspective is the variable nature of grain infestation observed between different reef sites and different carbonate grain types. The highest degree of grain infestation occurs within shallow, low-energy back-reef environments and the most susceptible grains (at all sites) are corals, molluscs and foraminifera. Coralline algae, Halimeda and echinoid fragments are rarely heavily infested. High rates of infestation at back-reef sites result in rapid diminution of the most susceptible grains, especially coral, which are either underrepresented, or contribute only to the finer sediment fractions, in the subsurface. Fore-reef grain assemblages undergo relatively little alteration. Microboring therefore has potential to bias the fossil record by removing the most susceptible skeletal grains. The impact of microboring upon back-reef grain assemblages must be considered when attempting to model depositional processes within both modern and ancient reef environments.  相似文献   

Why Worry About the Weather?     

John S. Perry 《Climatic change》1998,38(3):255-259

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