Sorption of nonionic compounds is strongly dependent on the content as well as the nature of the organic matter in soils and sediments. The composition and the structure of organic matter varies due to its origin and geological history and strongly influences the sorption affinity for nonionic organic compounds. Organic matter in unweathered shales and high-grade coals shows enhanced sorption (>1 order of magnitude) compared to organic matter in recent soils or geologically young material and low-grade coals. The results obtained indicate a decrease in sorption with increasing proportions of oxygen-containing functional groups in natural organic substances. A first approximation to estimate sorption coefficients for various organic matter is provided by an empirical correlation between the hydrogen/oxygen (H/O) atomic ratio as an index of the oxidation of the organic matter and the organic carbon normalized sorption coefficients (Koc). This approximation also permits adjustment of Kqc values derived from K0w data.

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Diffusion in natural porous media: contaminant transport, sorption/desorption and dissolution kinetics / by Peter Grathwohl. p. cm.-(Environmental fluid mechanics ; 1) Includes bibliographical references (p.

SignificanceIt has remained an unresolved question whether microorganisms recovered from the most arid environments on Earth are thriving under such extreme conditions or are just dead or dying vestiges of viable cells fortuitously deposited by atmospheric processes. Based on multiple lines of evidence, we show that indigenous microbial communities are present and temporally active even in the hyperarid soils of the Atacama Desert (Chile). Following extremely rare precipitation events in the driest parts of this desert, where rainfall often occurs only once per decade, we were able to detect episodic incidences of biological activity. Our findings expand the range of hyperarid environments temporarily habitable for terrestrial life, which by extension also applies to other planetary bodies like Mars.

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