The geochemistry of lead in rivers,estuaries and the continental shelf of the Southeastern United States

Transport by southeastern rivers has insignificant influence on the lead concentration of southeastern shelf waters. If the rate of mobilization and transport of lead by these rivers is representative of uncontaminated fluvial transport during the Pleistocene, only about 5% of the prehistoric output of lead to the North Atlantic can be accounted for by river input.Lead concentrations in southeastern shelf waters are similar to those of North Atlantic Water from the upper 1000 m, which is probably similar to the intrusion source water for the shelf. Atmospheric inputs to the shelf of the same magnitude as observed for the Western North Atlantic are difficult to reconcile given the residence time of shelf waters and their lead concentration unless the rate of loss of lead to shelf sediments is about the same as the atmospheric flux.     

Partitioning of Ca and Al between forsterite and silicate melt in dynamic systems with implications for the origin of Ca,Al‐rich forsterites in primitive meteorites

Abstract— We report the results of dynamic crystallization experiments that were specifically designed to study the dependence of Ca and Al partitioning between forsterite and melt in rapidly cooling Caand Al‐rich melts. The partitioning of Ca between olivine and silicate melt is found to be independent of the cooling rate within the range of 1.5 to 1000°C/hr and at CaO contents of up to 25 wt%. Within analytical uncertainty, our data plot on the equilibrium partitioning curve obtained by Libourel (1999). The partitioning behavior of Al at high cooling rates is more complex. Aluminum is much more heterogenously distributed in the olivine and the co‐existing melt than Ca. But, no systematic trend of Al partition coefficient with cooling rate is observed. We apply the results of the experiments to the formation of meteoritic forsterites with relatively high contents of Ca and Al. Although these forsterites are found frequently inside chondrules, the Ca contents of their host chondrules are far too low to crystallize these high Ca‐forsterites. This is also true for very rapid cooling of chondrule melts. The parental melt of these forsterites requires CaO contents above 20 wt%.     

Coronal Holes and Icosahedral Symmetry

The study of the expansion of the solar wind out of a system of coronal holes is continued. To this end, we consider the numerical integration of partial differential equations for problems with icosahedral symmetry, in general. First, employing Weyl theory, orbifold coordinates are introduced. Second, the icosahedral coordinates are discussed in detail. Third, following an analysis of the properties of these coordinates and the derivation of a few expressions useful for grid construction, various alternatives for the distribution of lattice points required for numerical integration are considered. A comparison of these numerical grids motivates the choice of a specific grid optimized for the numerical integration carried out in the accompanying paper by Kalish et al.(2002). This revised version was published online in July 2006 with corrections to the Cover Date.     

An Example of Island-Arc Petrogenesis: Geochemistry and Petrology of the Southern Luzon Arc, Philippines

Volcanism throughout the Luzon arc is associated with eastwardsubduction of the South China Sea floor along the Manila Trench.The southern section of the arc, the focus of this study, extendsfrom the Lingayen-Dingalan fault to the small islands just southof Luzon. Two segments appear to exist along this section ofthe arc the northern Bataan and southern Mindoro segments whichare separated by the Macolod Corridor. The volcanic rocks have typical arc phenocryst mineralogies:olivine, clinopyroxene, plagioclase, and titanomagnetite inthe most mafic rocks and clinopyroxene, plagioclase, orthopyroxene,titanomagnetite, ? amphibole in the more felsic samples. Complexzoning, sieve textures, and decoupling of incompatible traceelements suggest that processes such as assimilation have takenplace. The rocks from the study area range from basalts to rhyolitesand show typical calc-alkaline features. The rocks of the MacolodCorridor and Mindoro segment are particularly enriched in largeion lithophile elements (LILE), light rare earth elements (LREE),and radiogenic Sr compared with the Bataan segment. The datafall within the mantle array on Sr-Nd isotopic diagrams andgrade toward higher Sr and lower Nd isotopic values from northto south. A likely source for the volcanics of this study is either amid-ocean ridge basalt (MORB)-type mantle that undergoes higherdegrees of partial melting than regions involved in MORB generationor a previously depleted source. We suggest that the high fieldstrength element (HFSE) anomalies have been derived throughdifferential element partitioning during fluid transport fromthe subducted lithosphere to the mantle wedge. Continental crustal material seems to play a significant roleparticularly in the Macolod Corridor and the Mindoro segment,based on the high LILE, La/Sm ratios, radiogenic Sr isotopes,and ¹⁸O values. The Macolod Corridor and the Mindoro segmenthave undergone source contamination by crustal material fromthe North Palawan-Mindoro crustal block either during the collisionof this block with the Manila Trench or by subduction of sedimentsrich in this crustal material. A similar component has alsobeen detected in the Bataan segment but in minor amounts. Thetrace element and isotopic differences between the northernand southern sections of the arc are interpreted in terms ofvariable composition (i. e., variable amounts of a crustal componentintroduced from the Palawan-Mindoro crustal terrain) of themetasomatic fluids released into the source.     

Modeling of water–rock interactions in an aquitard of sandy clay in the coastal area near Beihai,China

Unconsolidated sand, gravel and clay deposits near Beihai and in the Leizhou Peninsula in southern China form an unconfined aquifer, aquitard and a confined aquifer. Water and soil samples were collected from the two aquifers in the coastal Beihai area for the determination of chemical compositions, minerals and soluble ions. Hydrogeochemical modeling of three flow paths through the aquitard are carried out using PHREEQC to determine water–rock interactions along the flow paths. The results indicate that the dissolution of anorthite, fluorite, halite, rhodochrosite and CO₂, and precipitation of potash feldspar and kaolinite may be occurring when groundwater leaks through the aquitard from the unconfined aquifer to the confined aquifer. Cation exchanges between Na and Ca can also happen along the flow paths.     

Partitioning of Na between olivine and melt: An experimental study with application to the formation of meteoritic Na2O-rich chondrule glass and refractory forsterite grains

We report experimentally determined 1 atm olivine/melt D_Na partitioning data for low f_O2, a variety of melt compositions and a temperature range of 1325-1522 °C. We demonstrated that high-current electron microprobe analyses (EPMA, I = 500 nA, 600 s on the peak) allow quantitative determination of Na₂O in olivine down to ∼10 μg/g. The mean olivine/melt D_Na from 12 experimental runs is 0.0031 ± 0.0007 (1σ). This is the recommended value for low pressures and a wide range of natural compositions.This result is applied to the problem of the origin of alkalis in chondrules and the formation of chondritic refractory forsterite grains. The data on Semarkona (LL3.0) chondrules show that Na₂O is primordial and was present during olivine crystallization. For refractory forsterite grains from Murchison (CM2), we demonstrate that high CaO contents are not a result of equilibration with Na₂O-rich melts, but require high activities of CaO during their formation.     

Hydrometeorologische Ergebnisse aus Abflußmessungen im Bereich des Hintereisferners (Ötztaler Alpen) in den Jahren 1957 bis 1959

Zusammenfassung Während der Internationalen Geophysikalischen Jahre 1957 bis 1959 wurde an einer Pegelmeßstelle bei 2287 m Höhe der Abfluß vom Hintereis- und Kesselwandferner registriert. Im vorliegenden Arbeitsbericht sollen spezifischen Merkmale des Abflusses aus dem zu 58% vergleitscherten Einzugsgebiet 26,6 km²) im Zusammenhang mit den meteorologischen Beidingungen dargestellt werden.Der Jahresabfluß betrug im Haushaltsjahr 1957/58 1848 mm und im Haushaltsjahr 1958/59 1770 mm; bedingt durch den stark negative massenhaushat der Gletscher was die Gletscherspende mit 24% bzw. 20% des Jahresabflusses außergewöhnlich hoch. Der winterabfluß (Oktober bis März) betrug nur 5% bzw. 10% des Jahresabflusses; die drei Sommermonate Juli bis September Lieferten dagegen 76% bzw. 72%. Der größte Monatsabfluß wurde im August 1958 mit 575 mm, im Juli 1959 mit 559 mm registriert.Die Häufigkeitsverteilung der Tagesabflußmengen für das Jahr 1957/58 ließ eine Andauer des Niedrigwassers mit Tages-Mittelwerten kleiner als 18,8 l/s km² (0,5 m³/s) von 217 Tagen (Oktober bis Mai, 59% des Jahres) erkennen. Größere Tagesabflüsse als 225 l/s km² (6,0 m³/s) kamen nur im Juli und August vor. Als Maximum wurden Abflußwerte bis zu 640 l/s km² Gletscherfläche im Tagesmittel erreicht, entsprechen 55m Abflußhöhe von den Schnee- und Eisflächen. Der exponentielle Abfall der Abflußganglinie vom Herbst zum Minimum im Frühjahr deutet an, daß es sich bei Winterwasser vorwiegend um das verzögerte Abfließen von in den Gletschern zurückgehaltenem Schmelzwasser aus der vorangegangenen Ablationsperiode handelt. Das Ansteigen der Wasserführung nach dem Beiginn der Schneeschmelze im Frühjahr erfolgt wegen des Wiedergefrierens von Schmelzwasser und wegen des Retentionsvermögens der Schneedecke mit einiger Verzörgerung.Die unperiodischen Schwankungen im Abflußgang stehen in engem Zusammenhang mit Wettervorgängen, wobei Schneeniederschlägen die Größte Bedeutung zukommt, weil die hohe Albedo einer Neuschneedecke die Ablation auf den Gletschern tagelang fast völlig unterbrechen kann. Aus zweistündigen Mittelwerten wurde für die Monate Juni bis September der mittlere Tagesgang der Wasserführung ermittelt. Die Ursache für das frühere Eintreten des taglichen Abflußmaximums im Spätsommer durfte verminderte Abflußverzögerung sein. Die Beziehung zwischen den Abflußwerten der Pegel Steg-Hospiz und Vent läßt einen Jahresgang erkennen.

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Summary During the International Geophysical Years 1957–1959 the run-off from Hintereisferner and Kesselwandferner was recorded by a stream gauge installed at an altitude of 2287 m. a. s. 1. The annual run-off in relation to mass budget and precipitation has already been reported in [10, 11]. In the present report characteristic features of run-off from a catchment area (26.6 km²) glaciated to 58 per cent shall be discussed with regard to the meteorological conditions.In the budget years 1957/58 and 1958/59 the yearly run-off was 1848 mm and 1770 mm, respectively. Owing to the strongly negative mass budget of the glaciers the glacier quota of 24 per cent and of 20 per cent, respectively, of the annual run-off was exceptionally high. Winter run-off (October to March) amounting to 5 per cent and to 10 per cent, respectively, of the yearly run-off was only small while July to September supplied 76 per cent and 72 per cent, respectively. The maximum monthly run-off was recorded in August 1958 with 575 mm, and in July 1959 with 559 mm.The frequency distribution of the daily run-off in 1957/58 showed a period of low run-off during 217 days (October to May, 59 per cent of the year) with daily means below 18.8 l/s km² (0.5 m³/s). Daily run-off exceeding 225 l/s km² (6.0 m³/s) occurred only in July and August. Daily means exceeding 338 l/s km² (9.0 m³/s) were recorded only three times in July. The maximum daily means of run-off were up to 640 l/s km² of glacier surface which corresponds to 55 mm of run-off from the snow and ice surfaces. The highest two hourly mean value was 950 l/s km² of the glacier surface. The exponential decrease of the run-off curve from fall to the minimum in spring indicates that winter water consists mainly of the delayed run-off of melt water stored in the glaciers during the preceding ablation period. Owing to the refreezing of the melt water and to the storage capacity of the snow cover run-off is somewhat delayed after the snow melt has set in.The aperiodic variations in the run-off are closely related to weather conditions. Snow falls are of primary importance as the high albedo of a fresh snow cover may interrupt ablation on glaciers almost completely for days. The mean daily variation of run-off was determined from two-hourly mean values for the period June to September. The early occurrence of the daily run-off. The relation between the run-off values recorded at the water gauges Steg-Hospiz and Vent indicates and annual variation.

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Résumé Pendant les Années Géophysiques Internationales de 1957 à 1959 l'écoulement du Hintereisferner et du Kesselwandferner a été enregistré par un limnigraphe installé à une altitude 2287 m. Un rapport a déjà été présenté dans [10, 11] sur l'écoulement annuel en rapport avec le bilan hydrologique du bassin. Dans le présent rapoort il sera traité des caractères spécifiques de l'écoulement d'un bassin dont 58% sont recouverts par le glacier, les quels seront mis en rapport avec les conditions météorologiques.L'écoulement annuel au cours de l'année hydrologique 1957/58 a été de 1848 mm et dans l'année hydrologique 1958/59 de 1770 mm. L'eau libérée par la perte de substance glacière représente 24% pour 1957/58 et 20% pour 1958/59 de l'écoulement annuel. Les pourcentages extrêmement élevés doivent être attribués au bilan fortement négatif des glaciers. L'écoulement d'hiver (Octobre à Mars) représentant 5% pour l'année 1957/58 et 10% pour 1958/59 de l'écoulement annuel a été petit tandis que les trois mois d'été (Juillet–Septembre) fournissaient 76% (1957/58) et 72% (1958/59). L'écoulement mensuel le plus élevé a été enregistré en Aôut 1958 avec 575 mm, et, en Juillet 1959 avec 559 mm.La répartition des fréquences des écoulements journaliers pour l'année 1957/58 indique une période d'étiage de 217 jours (Octobre à Mai, 59% de l'année) avec valeurs journalières en dessous de 18.8 l/s km² (0.5 m³/s). Des écoulements dépassant 225 l/s km² (6.0 m³/s) n'ont été enregistrés qu'en Juillet et Aôut. Les moyennes journalières n'ont dépassé les 338 l/s km² (9.0 m³/s) que trois fois en Juillet. Les valeurs maximums des moyennes journalières d'écoulement se sont élevées à 640 l/s km² de la surface des glaciers, correspondant à 55 mm d'écoulement des surfaces de neige et de glace. La valeur maximum d'une moyenne de deux heures a été de 950 l/s km² de la surface des glaciers. La chute exponentielle de la courbe d'écoulement allant de l'automne au minimum enregistré au printemps indique que dans les cas d'étiage il s'agit de l'écoulement retardé des aux de fonte refenues dans les glaciers pendant la période d'ablation précédente. L'accroissement de l'écoulement après le comencement de la fonte de neige au printemps est retardé dans une certaine mesure par le regel des aux de fonte et la capacité de rétention de la couche de neige. Les variations apériodiques dans l'écoulement sont en relations étroites avec les conditions atmospheriques dont les chutes de neige sont de la plus grade importance car l'albédo élevé d'une couche de neige fraîche interrompt parfois et presque complétement l'ablation sur les glaciers pour des jours entiers.L'amplitude moyenne de la variation journalière de l'écoulement a été, pour les mois de Juin à Septembre, détérminée à la base des valeurs moyennes de deux heures. L'apparition précoce du maximum d'écoulement journalier en fin d'été est probablement due à la diminution du retardement de l'écoulement en cette période. La relation entre le valeurs d'écoulement des limnigraphes de Steg-Hospiz et de Vent met en évidence une variation annuelle.

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Die für diesen Bericht erforderliche weitere Bearbeitung der Abflußdaten und die Fertigstellung des Manuskriptes wurde dem Verfasser im Rahmen seiner Tätigkeit bei der Kommission für Glaziologie an der Bayerischen Akademie der Wissenschaften ermöglicht, wofür an dieser Stelle gedankt sei.     

Diel Patterns in Chlorophyll <Emphasis Type="Italic">a</Emphasis> Specific Absorption Coefficient and Absorption Efficiency Factor of Picoplankton

Diel patterns in the chlorophyll a specific absorption coefficient of surface picoplankton, a*_pico (γ) (m²·[mg chlorophyll a]⁻¹), were studied at 7 stations under daily cycle of in situ light condition in the western subarctic Pacific and Japan Sea. All the data were normalized by dividing the anomaly with daily averaged a*_pico (γ). Opposite diel patterns were observed for the normalized a*_pico (443) and a*_pico (675) with maximum toward dawn or dusk and minimum toward midday at 4 stations under low-irradiance (LI) conditions and vice versa at 3 stations under high-irradiance (HI) conditions. The absorption efficiency factors at red absorption peak, Q _a (675), were determined by reconstruction with intracellular chlorophyll a concentration and cell diameter. The normalized Q _a (675) also showed diel pattern with maximum toward midday and minimum toward dawn or dusk under LI. The diel pattern in a*_pico (675) and Q _a (675) were primarily caused by changes in intracellular chlorophyll a concentration due to photoadaptation under LI. The diel pattern in a*_pico (443) was influenced by pigmentation, as recognized by blue to red ratio [a*_pico (443)/a*_pico (675)] under HI. This study proposed that the opposite diel pattern in a*_pico (γ) might occur for a wide range of algal species. The results presented here have important consequences for the interpretation of diel variations in optical properties observed in the open ocean.     

CO<Subscript>2</Subscript> Flux Measurements over the Sea Surface by Eddy Correlation and Aerodynamic Techniques

The measurements of the vertical transport of CO₂ were carried out over the Sea of Japan using the specially designed pier of Kyoto University on September 20 to 22, 2000. CO₂ fluxes were measured by the eddy correlation and aerodynamic techniques. Both techniques showed comparable CO₂ fluxes during sea breeze conditions: −0.001 to −0.08 mg m⁻²s⁻¹ with the mean of −0.05 mg m⁻²s⁻¹. This means that the measuring site satisfies the fetch requirement for meteorological observations under sea breeze conditions. Moreover, the eddy diffusivity coefficient used in the aerodynamic technique is found to be consistent with the coefficient used in the eddy correlation technique. The present result leads us to conclude that the aerodynamic technique may be applicable to underway CO₂ flux measurements over the ocean and may be used in place of the bulk technique. The important point is the need to maintain a measuring accuracy of CO₂ concentration difference of the order of 0.1 ppmv on the research vessels or the buoys.