The activity of NaCl in seawater of 10–40‰ salinity and 5–25°C at 1 atmosphere

The activity of NaCl in artificial seawater was measured potentiometrically with Na⁺- and Cl^? -sensitive electrodes. The salinity of the solutions, examined at 25°C, ranged from 10–40‰ salinity. The change in the activity from 5–25°C was measured at 35‰ salinity.The molal mean activity coefficient of NaCl in 35‰ seawater at 25°C is 0.667. The relative partial molal enthalpy of NaCl in 35‰ seawater is ?130 ±50 cal mol^?1. This value is in good agreement with the value measured in pure 0.72 M NaCl.The results were compared with activity coefficients predicted by a specific interaction model and by an ion association model. Good agreement was found in both cases.     

Photospheric magnetic field rotation: Rigid and differential

An autocorrelation of the direction of the large-scale photospheric magnetic field observed during 1959–1967 has yielded evidence that the field structure at some heliographic latitudes can display both differential rotation and rigid rotation properties.     

The determination of the derivatives in Brown's lunar theory

The fundamental matrix solutionT for the variational equations of a Hamiltonian system is symplectic. We use this fact to completeT when it is only partially known. We discuss three cases. The last one gives an easy proof for the method invented by Brown in his lunar theory.Paper presented at the 1981 Oberwolfach Conference on Mathematical Methods in Celestial Mechanics.Dedicated to Victor Szebehely.     

Integrated fluxes for emission lines in the ultraviolet spectra of several planetary nebulae

The IUE satellite observatory has been used to obtain absolutely-calibrated emission line fluxes for diagnostic lines of multiply-ionized C, N, O, Si, Ne, and Ar which occur in the ultraviolet spectral region of planetary nebulae. These data, when combined with data from the blue, visual, and near infrared, will provide improved estimates of ionic concentrations, plasma temperatures and densities, and elemental abundances.     

Composition and distribution of larval fishes in New Jersey high marshes

The surface of the salt marsh is an important, but largely unrecognized, site for fish reproduction and larval growth. In an attempt to determine the composition and distribution of fishes utilizing these habitats, we sampled larval and juvenile fish with plankton nets, dip nets, and traps at a variety of microhabitats (tidal and nontidal ponds and ditches and the marsh surface) in three New Jersey high marshes. Two of the three marshes had been altered for mosquito control. During April to September 1980, we collected over 2,400 larvae and juveniles. All study sites were dominated by the larvae of the resident killifishes (Fundulus heteroclitus, Cyprinodon variegatus, F. luciae, andLucania parva) and less commonlyMenidia beryllina. However, the occurrence and abundance of each species varied with microhabitat. Larval production in all three marshes peaked during June–July, but extended from May until September. In most instances juveniles of the dominant fishes had microhabitat preferences similar to the larvae. High marshes may be more important for fish production than previously recognized because they serve as nursery areas for the resident killifishes.     

Oxygen consumption rates in pelagic sediments from the Central Pacific: First estimates from microelectrode profiles

Oxygen profiles in pelagic sediments from the Manganese Nodule Program calcareous and siliceous ooze sites (MANOP sites C and S) in the central Pacific Ocean were measured with microelectrodes and are used to predict oxygen consumption rates beneath the sediment-water interface. We explain possible artifacts which occur during sample recovery and argue that minimum estimates of 0.083 and 0.025 μ moles $\text{O}{}_2\text{cm}{}^2\text{day}$ (C and S, respectively) can be calculated from the data. These oxygen consumption rates are in good agreement with in situ respirometer measurements previously reported for comparable sediments in the north Pacific, but previous estimates based on modeling of pore water nitrate profiles at both sites are two to five times smaller than our minimum fluxes. The differences in oxygen fluxes calculated by the two methods are probably in part due to uncertainty in the assumptions inherent in the nitrate model. However, non-steady state fluctuations in particulate organic matter fluxes could also be a reason for the disparity.     

Holocene flooding and species diversity in southwestern Amazonia

A thick blanket of Holocene alluvium lies over southwestern lowland Amazonia, and may possibly occur throughout much of the Amazon Basin. These deposits resulted from massive, seasonal flooding from about 11,000 to about 5000 yr B.P. that was followed by two cycles of erosion and deposition. Interpretations based on these geologic data suggest that southwestern lowland Amazonia is ecologically an “island” in a state of supersaturated disequilibrium as a result of colonization from Pleistocene refugia on its perimeter, and that habitats of highest diversity may be the most recent in origin. Conservation efforts and studies of Amazonian biogeography, soils, and paleoethnography should be reevaluated in light of the geologic data.     

The determination of SO42-, NaSO4-, and MgSO40 tracer diffusion coefficients and their application to diagenetic flux calculations

Sulfur-35 was used to monitor the non-steady-state tracer diffusion of the free sulfate ion and sulfate ion-pairs in aqueous solutions of MgSO₄ and Na₂SO₄. Diffusion coefficients were derived from radiotracer flux measurements taken over ionic strengths ranging from 0.001 to 0.7. The experimental tracer diffusion coefficient is a function of the diffusion coefficients of the free sulfate ion and the sulfate ion-pairs as well as the ion pair equilibrium constant. The free sulfate ion tracer diffusion coefficient was determined independently from both the MgSO₄ and Na₂SO₄, experiments and found to be 1.11 and 1.08 (in units of 10^-5cm²sec^-1, ± 10%, respectively. These values closely agree with that calculated from the Nernst expression, 1.07 sx 10^-5cm²sec^-1. The tracer diffusion coefficients of MgSO₄⁰ and NaSO₄^- were determined to be 0.85 and 1.23 sx 10^-5cm²sec^-1, respectively. These numbers are in reasonable agreement with the earlier work on mutual diffusion coefficients by Rard and Miller (1979b) (D_MgSO4^o = 0.65, D_naso4^- = 1.19) and Harned and Hudson (1951)D_MgSO4⁰ = (0.70). A modified version of the theoretical equation developed by Pikal (1971) is proposed for predicting the tracer diffusion coefficients of many ion-pairs relevant to seawater. Many of these predicted values are found to be within 10–20% of the empirical values extracted from mutual diffusion data. The experimental and theoretical diffusion coefficient data are used to calculate revised coupled diffusion coefficients, D^g, according to the model of Lasaga (1979).