The overall purpose of the project was to explore and quantify the processes that control the formation and reactivity of biogenic iron microminerals and their impact on the solubility of metal contaminants. The research addressed how surface components of bacterial cells, extracellular organic material, and the aqueous geochemistry of the DIRB microenvironment impacts the mineralogy, chemical ...

THERMAL IONIZATION MASS SPECTROMETRY STUDIES OF SM AND GD ISOTOPIC SHIFTS IN LUNAR METEORITES DUE TO NEUTRON CAPTURE: A PROGRESS REPORT. K. C. Welten, T. L. Owens, D. J. DePaolo, Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450 (e-mail: [email protected]); Center for Isotope Geochemistry, Department of Earth and Planetary Science, UC Berkeley & Lawrence Berkeley ...

In this note we introduce a method for robust principal component regression. Robust principal components are computed from the predictor variables, and they are used afterwards for estimating a response variable by performing robust linear multiple regression. The performance of the method is evaluated at a test data set from geochemistry. Then it is used for the prediction of censored values ...

[1] We disagree that the comparison of the smallvolume MnO2 coprecipitation method and the MnO2 cartridge method of Hung et al. [2008] is adequate. This is because at least some of the small-volume Th data used for their comparison relied on an early protocol of the smallvolume method that did not include a recovery correction. Thus results are potentially biased. New data from the South China ...

Introduction The U.S. Geological Survey (USGS) has been producing reference materials since the 1950s [1]. Over 50 materials have been developed to cover bulk rock, sediment, and soils for the geological community. These materials are used globally in geochemistry, environmental, and analytical laboratories that perform bulk chemistry and/or microanalysis for instrument calibration and quality ...

Clumped isotope geochemistry is concerned with the state of ordering of rare isotopes in natural materials. That is, it examines the extent to which rare isotopes (D, C, N, O, etc.) bond with or near each other rather than with the sea of light isotopes in which they swim. Abundances of isotopic ‘clumps’ in natural materials are influenced by a wide variety of factors. In most cases, their conc...

Microbial abundance and diversity in deep subsurface environments is dependent upon the availability of energy and carbon. However, supplies of oxidants and reductants capable of sustaining life within mafic and ultramafic continental aquifers undergoing low-temperature water-rock reaction are relatively unknown. We conducted an extensive analysis of the geochemistry and microbial communities r...

The monitoring of oxyanions in waters, presents significant challenges due to their relatively low concentrations, and a characteristically changeable/unstable/reactive geochemistry with high spatial and temporal turnover. This results in a very heterogeneous pattern of mobility and bioavailability, which is difficult to capture reliably and in a cost effective manner. The diffusive gradients i...

A large regional geochemical data set of O-horizon samples from a 188,000 km2 area in the European Arctic, analysed for 38 chemical elements, pH, electrical conductivity (both in a water extraction) and loss on ignition (LOI, 480 oC), was used to test the influence of different variants of cluster analysis on the results obtained. Due to the nature of regional geochemical data (neither normal n...

This chapter summarizes the oxygen isotope geochemistry of terrestrial basalts and their mantle sources, including the conceptual framework for interpreting such data and the phenomenology of known variations. In particular, the first section outlines the motivations for and first-order results of oxygen isotope studies of terrestrial and lunar basalts over the last 30 years; the second section...