Patterns of dissolved organic matter in subarctic peatlands

Samples of water from poor to very rich fens in the Schefferville region of subarctic Quebec revealed strong spatial and temporal variations in dissolved organic carbon (DOC), ranging from 2 to 40 mg 1^?1. Concentrations of DOC tend to increase during the summer and decrease in the autumn, at most sites, which probably reflects increased plant tissue decomposition and higher rates of evapotranspiration. Principal components analysis revealed that DOC is strongly associated with Fe, NO^?₃-N and NO^?₂-N, but essentially independent of other chemical properties of the peat water, such as pH, Ca, Mg, K, P, and NH⁺₄-N. Based on observed concentrations of DOC and estimates of summer runoff (June to September), export of DOC from four peatlands ranges from 1·1 to 4·9 gCm^?2, with the lowest values for peatlands underlain by dolomite. Molecular weight fractionation of four samples revealed significant differences in the dissolved organic matter (DOM), with the largest fractions (GF/C to 10 000 nmw) being dominant in the more acid samples. The ratio of absorbance at 400 and 600 nm wavelengths (E₄:E₆) has been used as a simple indicator of differences in DOM type, ranging from 3 to 15. There is a strong seasonal pattern of increasing E₄:E₆ ratio during the summer at many sites, though this ratio is essentially independent of other chemical properties of peat waters.     

Orthodoxy and creativity in theories of mountain building before 1922

In the 1870s, theories of mountain building emerged from little more than speculation to inference based on a growing body of observation and documentation. This coincided with abandonment of models stressing uplift, and their replacement, in the new orthodoxy, by models in which earth contraction led to lateral compression in its outer shell. Nevertheless, perceived weaknesses in this model gave impetus to new theories, some emphasizing primary vertical movement, and others continental displacement or subcrustal flow. The rebel theories added to the understanding of earth processes in important ways, by drawing attention to the weaknesses in the prevailing orthodoxy. But, in 1922, the complete answer remained out of reach.

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Zusammenfassung Die siebziger Jahre des vorigen Jahrhunderts brachten den Anfang von wissenschaftlich fundierten Theorien der Gebirgsbildung. Diese Zeit sah auch den Übergang von Erhebungstheorien zur neuen Lehrmeinung, nach welcher Erdkontraktion zu lateralen Drucken in der Außenhülle der Erde führte. Erkannte Schwächen dieses Modells führten jedoch zu neuen Gegentheorien, von denen einige primäre Vertikalbewegungen in den Vordergrund stellten, während andere Kontinentalverschiebung oder Unterströmungen als den Motor der Gebirgsbildung sahen. Diese Gegentheorien haben den Fortschritt der Erdwissenschaften gefördert, indem sie auf Schwächen der herrschenden Lehrmeinung aufmerksam machten. Aber selbst zu Argands Zeit war ein völlig befriedigendes Modell noch gar nicht erreichbar.

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Résumé C'est dans les années 1870–1880 que commençaient à s'établir les premières théories vraiment scientifiques de l'orogenèse. C'était la décade qui marqua l'abandon des théories à base de soulèvement et le début du règne de la nouvelle orthodoxie d'après laquelle la contraction de la terre mène à la compression latérale d'une pellicule extérieure. Néansmoins, certaines faiblesses du nouveau modèle servaient d'élan à des théories rebelles dont quelques-unes soulignaient l'importance des soulèvements primaires, tandisque d'autres cherchaient le moteur de l'orogenèse dans la dérive des continents ou dans des courants dans une masse quasi-fluide subcrustale. Ces théories rebelles ont avancé la science en soulignant les faiblesses de l'orthodoxie. En fin de compte, une solution complètement satisfaisante ne paraissait pas encore pouvoir être atteinte à l'époque d'Argand.

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Trace-element distribution in an active hydrothermal system, Roosevelt hot springs thermal area, Utah

Chemical interaction of thermal fluids with reservoir rock in the Roosevelt Hot Springs thermal area, Utah, has resulted in the development of characteristic trace-element dispersion patterns. Multielement analyses of surface rock samples, soil samples and drill cuttings from deep exploration wells provide a three-dimensional perspective of chemical redistribution within this structurally-controlled hot-water geothermal system.Five distinctive elemental suites of chemical enrichment are recognized, each characteristic of a particular combination of physical and chemical conditions within the geothermal system. These are: (1) concentrations of As, Sb, Be, and Hg associated with siliceous material at locations of liquid discharge, fluid mixing or boiling; (2) concentrations of Mn, Ba, W, Be, Cu, Co, As, Sb and Hg in manganese and iron oxide deposits; (3) high concentrations of Hg in argillized rock near fumaroles and lower concentrations in a broad diffuse halo surrounding the thermal center; (4) concentrations of As in sulfides and Li in silicate alteration minerals immediately surrounding high-temperature fluid flow-controlling fractures; (5) deposits of CaCO₃ at depth where flashing of brine to steam has occurred due to pressure release. The geochemical enrichments are not, in general, widespread, pervasively developed zones of regular form and dimension as are typical in many ore-forming hydrothermal systems.As the geothermal system develops, changes and eventually declines through time, the chemical deposits are developed, remobilized or superimposed upon each other, thus preserving within the rocks a record of the history of the geothermal system. Recognition of trace-element distribution patterns during the exploration of a geothermal system may aid definition of the present geometry and interpretation of the history of the system.     

Characteristics of air flow above and within soybean canopies

Air flow was observed above and within canopies of a number of kinds of soybeans. The Clark cultivar and two isolines of the Harosoy cultivar were studied in 1979 and 1980, respectively. Wind speed above the canopy was measured with cup anemometers. Heated thermistor anemometers were used to measure air flow within the canopy. Above-canopy air flow was characterized in terms of the zero-plane displacement (d), roughness parameter (z _o) and drag coefficient (C _d). d and z _o were dependent on canopy height but were independent of friction velocity in the range 0.55 to 0.75 m s^?1 · C _d for the various canopies ranged from 0.027 to 0.035. Greater C _d values were measured over an erectophile canopy than over a planophile canopy. C _d was not measurably affected by differences in leaf pubescence. Within-canopy wind profiles were measured at two locations: within and between rows. The wind profile was characterized by a region of great wind shear in the upper canopy and by a region of relatively weak wind shear in the middle canopy. Considerable spatial variability in wind speed was evident, however. This result has significant implications for canopy flow modeling efforts aimed at evaluating transport in the canopy. In the lower canopy, wind speed within a row increased with depth whereas wind speed between two rows decreased with depth. The wind speeds at the two locations tended to converge to a common value at a height near 0.10 m. The attenuation of within-canopy air flow was stronger in canopies with greater foliage density. Canopy flow attenuation seemed to decrease with increasing wind speed, suggesting that high winds distorted the shape of the canopy in such a manner that the penetration of wind into the canopy increased.     

Ground-water models for water resource planning

In the past decade hydrogeologists have emphasized the development of computer-based mathematical models to aid in the understanding of flow, the transport of solutes, transport of heat, and deformation in the ground-water system. These models have been used to provide information and predictions for water managers. Too frequently, ground-water was neglected in water resource planning because managers believed that it could not be adequately evaluated in terms of availability, quality, and effect of development on surface-water supplies. Now, however, with newly developed digital ground-water models, effects of development can be predicted. Such models have been used to predict hydrologic and quality changes under different stresses. These models have grown in complexity over the last ten years from simple one-layer models to three-dimensional simulations of ground-water flow, which may include solute transport, heat transport, effects of land subsidence, and encroachment of saltwater. Case histories illustrate how predictive ground-water models have provided the information needed for the sound planning and management of water resources in the USA.     

Composition and distribution of beach debris in Orange County, California

Many studies have quantified debris collected on beaches around the world. Only a few of those studies have been conducted in the United States, and they are largely limited to semi-quantitative efforts performed as part of volunteer clean-up activities. This study quantifies the distribution and composition of beach debris by sampling 43 stratified random sites on the Orange County, California coast, from August to September 1998. We estimated that approximately 106 million items, weighing 12 metric tons, occur on Orange County beaches. The most abundant items were pre-production plastic pellets, foamed plastics, and hard plastics. Debris density on the remote rocky shoreline was greater than that on high-use sandy beaches for most debris items. This finding partially reflects the periodic clean-up of high-use beaches by local municipalities, and also indicates that a high percentage of the observed debris was transported to the site from waterborne sources.     

Detection Time for Plausible Changes in Annual Precipitation, Evapotranspiration, and Streamflow in Three Mississippi River Sub-Basins

We use diagnostic studies of off-line variable infiltration capacity (VIC) model simulations of terrestrial water budgets and 21st-century climate change simulations using the parallel climate model (PCM) to estimate the time required to detect predicted changes in annual precipitation (P), evapotranspiration (E), and discharge (Q) in three sub-basins of the Mississippi River Basin. Time series lengths on the order of 50–350 years are required to detect plausible P, E, and Q trends in the Missouri, Ohio, and Upper Mississippi River basins. Approximately 80–160, 50, and 140–350 years, respectively, are needed to detect the predicted P, E, and Q trends with a high degree of statistical confidence. These detection time estimates are based on conservative statistical criteria (α = 0.05 and β = 0.10) associated with low probability of both detecting a trend when it is not occurring (Type I error) and not detecting a trend when it is occurring (Type II error). The long detection times suggest that global-warming-induced changes in annual basin-wide hydro-climatic variables that may already be occurring in the three basins probably cannot yet be detected at this level of confidence. Furthermore, changes for some variables that may occur within the 21st century might not be detectable for many decades or until the following century – this may or may not be the case for individual recording station data. The long detection times for streamflow result from comparatively low signal-to-noise ratios in the annual time series. Finally, initial estimates suggest that faster detection of acceleration in the hydrological cycle may be possible using seasonal time series of appropriate hydro-climatic variables, rather than annual time series.