Chemical character of return irrigation water in tropical volcanic islands

Unequivocal identification of irrigation return water through routine chemical analyses does not appear possible in tropical volcanic islands. Several constituents, nevertheless, will suggest an agricultural source if they are present in large concentrations. Nitrate is the most useful indicator; background concentrations are generally less than 2 ppm but return irrigation water will commonly have concentrations of between 5 and 50 ppm. Sulfate appears to be the next most useful indicator. Calcium, silica, and bicarbonate have also been reported to be significant. Where detailed studies have been made of agricultural water balances, regional ground-water flow directions, and deep-well hydraulics, hydrochemistry can provide critical supporting data for the identification of return irrigation water which could be a potential ground-water pollutant.     

Vegetation and associated environments during the past 14,000 years near Moulton Pond,Maine

Pollen influx and percentage diagrams were prepared from an 11.4 m core from Moulton Pond, Maine. The pond basin was deglaciated about 14,000 y. a., after which it was located on an island in a sea of subarctic character until about 12,400 y. a. when the surrounding area emerged from the sea. The terrestrial vegetation was tundra until about 10,000 y. a. A change in the tundra vegetation is synchronous with the emergence from the sea, but synchroneity with the Pineo Ridge glacial readvance, which reached its maximum 50 km to the east of the pond about 12,700 y. a., is also possible because of imprecision in the dating. Comparisons of the Moulton Pond results with late-glacial pollen sequences elsewhere in eastern United States and adjacent Canada reveal a lack of synchroneity in vegetational changes casting doubt on claims of major broad-scale climatic shifts over the entire area.The tundra period at Moulton Pond ended with a transition of a few hundred years to partly open, relatively xeric forests of low diversity dominated by white pine, oak, and birch trees. There was no intervening boreal forest. In the postglacial period the vegetation was continually changing, including in the early portion a series of immigrations of temperate tree taxa which later became important in the forests. The transient nature of these assemblages is further indicated by their differences from the closest modern analogs. From about 7100 y. a. until settlement by Europeans 200 y. a., the forests were closed. A major decline of conifers centering about 4700 y. a. was followed by maxima of mesic hardwoods about a thousand years later. In the most recent 2000 yr, the pollen record suggests greater environmental severity, evidenced by increasing spruce. But for the entire postglacial period, the closest modern vegetational analogs are all in the conifer-hardwood region. Much of the postglacial pollen sequence is inexplicable in climatic terms, as evidenced by nonsynchronous behavior of hemlock and beech.The pollen influx diagram is useful for distinguishing tundra from forest, but for the postglacial period it is difficult to interpret. Pollen influx data are strongly affected by shifts in the pattern of sedimentation in lakes. We propose that such shifts account for the major changes in influx in mid- and late-postglacial time at Moulton Pond and at Rogers Lake, Connecticut. This complicates the interpretation of influx data which otherwise are superior to percentage data.     

An investigation of a method for predicting dew duration

Summary A method is described for the prediction of dew duration with the aid of a nomogram involving synoptic parameters. In order to enter the nomogram, knowledge of the net radiation, a characteristic dew point depression, and the wind speed near the surface is required. Methods for estimating the net radiation and the dew point depression are described.Data collected in 1954 at 18 stations representing a variety of climatic zones in the United States were analysed in nomogram form. The characteristics of the nomograms are found to be dependent on the thermal characteristics of the underlying surface. An attempt is made to relate the synoptic parameters employed to the physical processes of heat exchange at the interface. Difficulties of the forecasting problem are discussed.

---

Zusammenfassung Eine Nomogramm-Methode zur Vorhersage des Auftretens und der Andauer von Tau wird beschrieben. Zur Anwendung dieser Methode werden Angaben über die Strahlungsbilanz an der Erdoberfläche, über eine charakteristische Differenz zwischen Luft- und Taupunktstemperatur sowie über die Windgeschwindigkeit in Bodennähe benötigt. Verfahren zur Abschätzung der Strahlungsbilanz und der Taupunktsdepression werden beschrieben.Die Ergebnisse umfangreicher Taubeobachtungen, welche im Sommer 1954 an 18 Stationen in verschiedenen Klimagebieten der Vereinigten Staaten gesammelt wurden, werden in Nomogrammform analysiert. Die Charakteristiken der Nomogramme erweisen sich als abhängig von den thermischen Eigenschaften der Bodenunterlage. Es wird der Versuch gemacht, die Nomogrammparameter zu den physikalischen Prozessen des Wärmeumsatzes an der Erdoberfläche in Beziehung zu setzen. Die Schwierigkeiten des Problems einer Tauvorhersage werden erörtert.

---

Résumé On décrit une méthode de prévision de la durée de rosée basée sur des nomogrammes. Pour appliquer cette méthode il faut connaître le bilan radiatif à la surface du sol, une différence caractéristique entre la température de l'air et celle du point de rosée, ainsi que la vitesse du vent près du sol. On décrit également des procédés pour estimer le bilan radiatif et la dépression du point du rosée.Les résultats d'un grand nombre d'observations de rosée, qui ont été faites pendant l'été 1954 à 18 stations dans diverses régions climatiques des Etats-Unis, sont analysés à l'aide de nomogrammes. Les caractéristiques de ceux-ci ont été reconnues comme dépendantes des conditions thermiques du sol. On tente de mettre en rapport les paramètres de ces nomogrammes avec les processus physiques de l'économie thermique à la surface du sol. Pour terminer on discute les difficultés du problème de la prévision de la rosée.

---

---

With 11 Figures     

Melt inclusions and crystal-liquid separation in rhyolitic magma of the Bishop Tuff

Melt inclusions in quartz phenocrysts from a single clast of pumice near the base of the plinian pumice fall of the Bishop Tuff were studied to test ideas concerning separation of melt and crystals in silicic magmas. Ten analyzed inclusions from the pumice clast are of high silica rhyolite composition with very low contents of the highly compatible elements Ba, Sr, and Eu, consistent with extensive fractionation. The concentrations of U, La, Ce, Mg, and Ca of these ten melt inclusions vary considerably as determined by ion microprobe. Petrologic considerations indicate that uranium is an incompatible element with a maximum bulk partition coefficient D of about 0.2 and that the evolution of the uranium content of the melt was controlled by crystallization of the magma. A minimum of 33 wt% perfect fractional crystallization is required to explain the observed range in uranium. However, only 17 wt% crystals occurred in the pumice clast. The greater calculated fraction of crystals requires significant separation of crystals and melt before the eruption of the plinian pumice fall in spite of the fact that crystal mixing (settling, etc.) did not occur in the Bishop magma.     

Ground Water Monitoring Statistics Update: Part I: Progress Since 1988

Current federal ground water monitoring statistical regulation dates from the revised RCRA Subtitle C Final Rule of 1988. That rule was a considerable advance over previous RCRA statistical rules. However, two major problem areas remained: facility-wide false positive rate (FWFPR) control and spatial variability. Progress has been made in the 1991 Subtitle D Final Rule and in guidance: the 1992 Addendum to Interim Final Guidance in particular includes a substantial conceptual advance toward resolving the FWFPR problem. Other areas of improvement include normality testing and distribution assumptions, dropping the four independent samples per monitoring period requirement, allowing a preliminary evaluation short of a 40 CFR Part 258 Appendix II assessment upon finding a statistically significant increase, and suggesting superior alternatives to analyses of variance (ANOVAs) and tests of proportions.
The problem of dealing with natural spatial variability remains. Although certain techniques listed in the regulations can control for inherent spatial variability and the performance standards require doing so "when necessary," little attention has been paid to the ubiquity of such spatial variation. Moreover, regulatory traditions favoring upgradient-downgradient comparisons often make control of natural spatial variation difficult and ineffective. With new. lined facilities easily implemented statistical solutions are available; however, dealing with the several existing solid waste facilities which will now be regulated under Subtitle D will present major challenges.
In short, the 1988 revision of the Subtitle C rules made it more possible to provide statistically sound monitoring programs, and there has been steady progress since then. Challenges remain, however. These vary from slate to slate, particularly with regard to controlling false positives and false negatives in the presence of natural spatial variability.