Definition and measurement of salinity in salt lakes   总被引：4，自引：0，他引：4  

W. D. Williams  J. E. Sherwood 《International Journal of Salt Lake Research》1994,3(1):53-63

Salinity is the most important chemical attribute of athalassic salt lakes. Even so, some confusion persists of what salinity means and how to measure it. For sal lakes, salinity is best defined as the sum total of all ion concentrations, or total ion concentration. Ideally, it is recommended that salinities be expressed on a mass per mass basis and as ppt (parts per thousand). Direct measurements of salinity can only be derived from full ionic analyses. Indirect measurements can be derived by determinations of density, conductivity, freezing point depression and total dissolved solids or matter.  相似文献   

Variations in water clarity and chlorophylla in Tampa Bay, Florida, in response to annual rainfall, 1985–2004     

Gerold Morrison  Edward T. Sherwood  Richard Boler  Joe Barron 《Estuaries and Coasts》2006,29(6):926-931

In the Tampa Bay region of Florida, extreme levels of annual and seasonal rainfall are often associated with tropical cyclones and strong El Niño episodes. We used stepwise multiple regression models to describe associations between annual and seasonal rainfall levels and annual, bay-segment mean water clarity (as Secchi depth [m]), chlorophylla (μg I^?1), color (pcu), and turbidity (ntu) over a 20-yr period (1985–2004) during which estimated nutrient loadings have been dominated by non-point sources. For most bay segments, variations in annual mean water clarity were associated with variations in chlorophylla concentrations, which were associated in turn with annual or seasonal rainfall. In two bay segments these associations with annual rainfall were superimposed on significant long-term declining trends in chlorophylla. Color was significantly associated with annual rainfall in all bay segments, and in one segment variations in color were the best predictors of variations in water clarity. Turbidity showed a declining trend over time in all bay segments and no association with annual rainfall, and was significantly associated with variations in water clarity in only one bay segment. While chlorophylla, color, and turbidity a affected water clarity to varying degrees, the effects of extreme rainfall events (El Niño events in 1998 and 2003, and multiple tropical cyclone events in 2004) on water clarity were relatively short-lived, persisting for periods of months rather than years. During the 20-yr period addressed in these analyses, declining temporal trends in chlorophylla and turbidity, produced in part by a long-term watershed management program that has focused on curtailing annual loadings of nitrogen and other pollutants, may have helped to prevent the bay as a whole from responding more adversely to the high rainfall periods that occurred in 1998 and 2003–2004.  相似文献   

Palaeomagnetic study of Archaean Banded Hematite Jasper Rocks from the Singhbhum-Orissa Craton, India     

Ashis K. Das  J. D. A. Piper  S. Basu Mallik  G. J. Sherwood   《Precambrian Research》1996,80(3-4)

The Banded Hematite Jasper Formation within the Iron Ore Supergroup of the Singhbhum Craton in eastern India comprises fine alternating layers of jasper and specularite. It was deposited at 3000 Ma and deformed by a mobile episode at 2700 Ma. Hematite pigment (<1 μm) mixed with cryptocrystalline silica and specularite (> 10 μm) is chiefly responsible for red to brown rhythmic bands in the hematite jasper facies although thermomagnetic study also shows that minor amounts (1–2%) of magnetite are present. Palaeomagnetic study identifies a dual polarity remanence resident in hematite (D/I = 283/60°, α₉₅ = 12°) which predates deformation. Studies of the fabric of magnetic susceptibility and rock magnetic results suggest a diagenetic origin for this magnetisation with the hematite formed from oxidation of primary magnetite. The palaeopole (32°E, 24°N, dp/dm = 14/18°) records the earliest post-metamorphic magnetisation event in the Orissa Craton. A minimum apparent polar wander motion of the Orissa-Singhbhum craton of through 80° is identified during Late Archaean times (2900-2600 Ma).  相似文献   

NONLINEAR COMPLEX RESISTIVITY OF SOME NICKEL SULPHIDES FROM WESTERN AUSTRALIA*     

S.H. HALL  G.R. OLHOEFT 《Geophysical Prospecting》1986,34(8):1255-1276

The electrochemical transfer characteristics of nickel sulphides from six West Australian localities are examined by the nonlinear complex resistivity (nlcr ) method. Ores are classified on the basis of their state of oxidation (supergene, transition zone and primary ores) in an equivalent mine water electrolyte; evidence is found for a systematic change of electrical response with oxidation that is symptomatic of electrochemical reactions varying from diffusion to charge-transfer controlled processes. The analysis is based on the assumption that the Randies’ circuit is an effective model of a rock's electrical response in its natural electrolyte. Both complex impedance plane graphs and computer inversion are used to study the model. Harmonic distortion is a useful aid in this interpretation.  相似文献   

Impact of agriculture on surface water in Ireland Part II. Prospects for the future     

Marie Sherwood 《Environmental Geology》1986,9(1):11-14

Agricultural activity is estimated to be responsible for only 6% (8 km) of the total length (135 km) of seriously polluted river channel, but for over 30% (294 km) of the slightly or moderately polluted length (963 km) of channel recorded to date in the state. This article examines the present sources and causes of pollution from agricultural wastes, and speculates on the likely direction of future trends. The most common sources of surface water pollution are animal manures, silage effluent, runoff from land following spreading, and fertilizers.  相似文献   

Some rock magnetic properties of mid-Cretaceous basalts from Israel and India (Rajmahal traps), and their bearing on palaeointensity experiments     

Graham J. Sherwood 《Physics of the Earth and Planetary Interiors》1992,70(3-4):237-242

A wide range of rock magnetic properties have been determined from two collections of mid-Cretaceous basalts; one from Israel, the other from the Rajmahal traps in northeast India. Deuteric oxidation is rare in both collections, with titanium-rich titanomagnetite being the principal remanence carrier in most cases. There are a number of differences in rock magnetic properties between the two groups. Some of these seem to be primary, whereas others appear to be caused by hydrothermal alteration and weathering, which are more prevalent in the Indian rocks. These rocks are being used in palaeointensity experiments, from which it is hoped to determine the strength of the Earth's magnetic field during the long period of normal polarity in the mid-Cretaceous. Thellier palaeointensity experiments have been performed on two samples from each site. The degree of agreement between the two results is highly variable. The low blocking temperatures and the presence of secondary viscous components in many samples make Thellier palaeointensity experiments very difficult. A further problem is that of thermal alteration, two main types of which are observed. The first manifests itself as a large and sudden increase in partial thermoremanent magnetization (pTRM) capacity, and the second as a steady decrease in the size of pTRM with increasing temperature.  相似文献   

Experimental diffusion of hydrogen into synthetic fluid inclusions in quartz   总被引：2，自引：0，他引：2  

D. L. HALL  S. M. STERNER 《Journal of Metamorphic Geology》1995,13(3):345-355

Abstract Quartz-hosted, synthetic CO₂-H₂O fluid inclusions behave as open systems with respect to diffusional transfer of hydrogen during laboratory-simulated metamorphic re-equilibration at 650, 750 and 825°C and 1.5 kbar total pressure with f_O2 defined by the C-CH₄ buffer. Microthermometry and Raman spectroscopy show that the initial CO₂-H₂O inclusions become CO₂-CH₄-H₂-H_2O
inclusions after diffusive influx of hydrogen from the reducing confining medium. Measurable changes are observed in inclusion compositions after only 15 days of re-equilibration, implying significant hydrogen mobility at still lower temperatures over geological time spans. Results of synthetic inclusion re-equilibrium experiments have profound implications for the interpretation of natural fluid-inclusion data; failure to account for potential hydrogen migration in inclusions from high-temperature geological environments may lead to erroneous estimates of P-T, and/or the compositions of metamorphic fluids.  相似文献   

Surface energy balance and the genesis of deserts     

Dr. Sherwood B. Idso 《Meteorology and Atmospheric Physics》1981,30(3):253-260

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REPLY TO the preceding Discussion by Ronald W. Crites and Sherwood C. Reed of "Land Application of Waste – An Accident Waiting to Happen"     

Ronald W. Crites  Sherwood C. Reed 《Ground water》1979,17(6):608-608

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On the use of equations to estimate atmospheric thermal radiation     

Sherwood B. Idso 《Theoretical and Applied Climatology》1974,22(3):287-299

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