The role of lunar volcanism in the history of the moon is documented using lunar-orbit and earth-based data along with characterizations derived from Apollo and Luna sample-return missions. Characteristics of mare and highland volcanic features are described, Apollo and Luna results are discussed, and the characteristics of other mare deposits and of other highland features of possible volcanic origin are summarized. Major conclusions are that: (1) there is little unequivocal morphologic evidence for highland volcanism, (2) lunar mare lavas appear to have originated from depths of 100 to 500 km, (3) impact melting does not appear to have been a factor in the generation of mare lavas, (4) mare volcanism was characterized by massive outpourings of very fluid volatile-poor lava analogous to terrestrial flood basalts, (5) mare volcanism took place from 3.83 to about 2.5 billion years ago, (6) the preferential occurrence of mare deposits in large impact basins appears to be generically unrelated to basin formation, and (7) a thicker farside crust may be responsible for the distinctive nearside-farside asymmetry of mare deposits.

Lunar volcanism in space and time.

Organo and inorgano-organo-modified clays in the remediation of aqueous solutions: An overview

Clay minerals are abundant, inexpensive, and generally safe materials for environmental applications. Because of their large specific surface area, high porosity, surface charge, and surface functional groups, clay minerals function as adsorbents, filters, flocculates, and carbon stabilizers. Further, the surfaces of clay minerals can be modified from hydrophilic to hydrophobic, for example, making them good adsorbents and carriers of non-ionic organic compounds. This chapter summarizes the processes, mechanisms, and applications of clay minerals in the adsorption, removal, and stabilization of natural organic matter, heavy metal contaminants, organic and biological cations, and non-ionic organic compounds. It may serve as a research resource or as a graduate level reading for students in environmental, agricultural, and materials sciences.

Clays and Clay Minerals for Pollution Control

It is shown that erosion has been active on Mars so that many of the surface landforms are products of degradation. Unlike earth, erosion has not been a universal process, but one areally restricted and intermittently active so that a landscape is the product of one or two cycles of erosion and large areas of essentially undisturbed primitive terrain; running water has been the principal agent of degradation. Many features on Mars are most easily explained by assuming running surface water at some time in the past; for a few features, running water is the only possible explanation.

Water and processes of degradation in the Martian landscape

We studied the effect of humified organic matter (OM) on the mineralization of a representative labile organic compound in soil. In an incubation experiment, a 13 C-labeled 2-decanol was added to soil either alone (2-dec p ) or in mixture with two humic acids from compost (HAC p ) and lignite (HAL p ) which had different hydrophobic properties. Isotopic dilution (d 13 C) showed that after 3 months of incubation about 58, 40 and 28% of the added 13 C was retained in the whole soil treated with HAL p , HAC p and 2-dec p , respectively. The higher the hydrophobicity of the employed humic material, the larger was the sequestration of organic carbon in soil. Fractionation of incubated samples revealed that the labeled carbon progressively accumulated in the finest particle-size fractions. However, the high hydrophobicity of the lignite HA favored accumulation of 13 C also in the sand-sized fraction. The NMR spectra of humic extracts showed that the 13 C-methyl group in the original 2-decanol had been oxidized to a 13 C-carboxyl group during incubation for all treatments. This indicated that despite its hydrophilicity, the resulting carboxyl carbon was sequestered into the hydrophobic domains of the humic pool in soil. In fact, the residual 13 C was larger in humic than in fulvic extracts for the control sample (2-dec p ) and even more so in extracts from soil treated with both exogenous humic acids. Our results suggest that labile organic compounds may be effectively protected in soil by humified OM and their microbial mineralization substantially reduced. Innovative soil management practices employing hydrophobic humic substances may increase the biological stability of soil OM and thus contribute to significantly mitigate CO2 emissions from agricultural soils. q 2002 Elsevier Science Ltd. All rights reserved.

Increased soil organic carbon sequestration through hydrophobic protection by humic substances

Data obtained from batch kinetics sorption experiments for naphthalene and diuron using two organoclays [trimethylphenylammonium (TMPA)-clay and benzyldimethyltetradecylammonium (BDTDA)-clay] in aqueous and methanol−water systems were analyzed with a first-order one-site mass transfer model (OSMTM) to obtain kinetic parameters. The mass transfer coefficient (e) exponentially decreased as the sorption coefficient (Kp) increased, and a log-linear increase in e was observed with an increase in the volume fraction of cosolvent (f c) in the system. Regression equations relating e to f c, measured in mixed solvents, could be extrapolated to f c = 0 to obtain the coefficients in aqueous systems. The organic cosolvent effects on the sorption kinetics behavior of naphthalene and diuron depended on the sorbate structure, the cosolvent fraction, and the arrange ment of the exchanged quaternary alkylammonium ions in montmorillonite-clay interlayers.

Organic cosolvent effects on sorption kinetics of hydrophobic organic chemicals by organoclays

Mossbauer absorption spectrography can be used to establish the presence of Fe2+ and Fe3+ in clay minerals. In the sheet structure silicates, octahedrally coordinated iron can be distinguished from tetrahedrally coordinated iron. Siderite and goethite, common contaminants of the clay minerals, can usually be detected. Goethite has a well-organized structure, though, owing to its fine grain size, it may appear to be amorphous to x-rays. The various families of clay minerals show minor differences in isomer shift and quadrupole splitting values, caused by variations in the character of the octahedral layer.

https://science.sciencemag.org/content/sci/156/3774/504.full.pdf

Mössbauer Analysis of Iron in Clay Minerals

K, Ar, and mineral analyses of montmorillonitic mud samples 4233 ft to 16,450 ft deep from a well in the Mississippi Delta area show that, with depth, the apparent K-Ar ages of the bulk samples decrease 100 m.y.; the >2 μ fraction is relatively constant in apparent age at approximately 400 m.y.; and the apparent age of the μ fraction decreases 40 m.y. with depth. With increasing depth and temperature, K (0.8 percent) appears to be released from the course K-feldspar and mica and to become fixed between the montmorillonite layers. Due to the formation of chloritic layers, fewer illitic layers are formed than is commonly supposed. K-Ar data may be useful in reconstructing the thermal and burial history of shales.

J.M. Wampler

Papers

Organic cosolvent effects on sorption kinetics of hydrophobic organic chemicals by organoclays

Mössbauer Analysis of Iron in Clay Minerals

K, Ar, Illite Burial

The illite-phosphate association

Chapter 7 - Potassium-Argon