Geologic temperature record | EPFL Graph Search

The geologic temperature record are changes in Earth's environment as determined from geologic evidence on multi-million to billion (109) year time scales. The study of past temperatures provides an important paleoenvironmental insight because it is a component of the climate and oceanography of the time. Methods PaleoclimatologyPaleothermometerMarine isotope stage and Timeline of glaciation Evidence for past temperatures comes mainly from isotopic considerations (especially ); the Mg/Ca ratio of foram tests, and alkenones, are also useful. Often, many are used in conjunction to get a multi-proxy estimate for the temperature. This has proven crucial in studies on glacial/interglacial temperature. Description of the temperature record Pleistocene The last 3 million years have been characterized by cycles of glacials and interglacials within a gradually deepening ice age. Currently, the Earth is in an interglacial period, beginning about 20,000 years

Hygiene considerations during the collection, storage and processing of source-separated urine into a marketable fertilizer

Tamar Kohn, Simon Schindelholz, Manfred Schoger

Laboratory and field studies along with inactivation data from the literature are used to model bacteria inactivation during urine storage and struvite production. The model is used to evaluate urine storage and struvite drying under the fluctuating temperature and relative humidity. Recommendations are made to enhance microbial inactivation during urine storage and struvite production in low-resource field settings and to promote the safety of using urine-derived fertilizers.

2016

Forced periodic temperature cycling of chemical reactions in microstructure devices

Lioubov Kiwi, Martin Luther, Albert Renken

In this publication, several stainless steel microstructure reactors specially designed to obtain rapid and periodic temperature changes are presented. Different microstructure reactor designs have been manufactured and tested for their thermal behaviour and equally by running a test reaction under stationary and non-stationary temperature conditions. The devices were continuously electrically heated and periodically cooled by a deionized water flow. The objective of the experimental measurements was to demonstrate that non-stationary temperature conditions may lead to an increase in the reaction rate compared to the stationary conditions. The heterogeneously catalysed oxidation of CO was chosen as the test reaction. The catalyst used was a dispersion of platinum on a porous alumina support generated by sol–gel technology. The experiments realized under non-stationary temperature conditions with a temperature oscillation amplitude of 41K and a period duration of 21 s show an increase in the mean CO2 concentration of a factor 1.72 compared to the mean concentration under quasi-stationary temperature conditions. The simulations of a simple monomolecular reaction under non-stationary temperature conditions indicate that the presence of a transitional surface coverage generated by the temperature oscillations may be a possible explanation for the observed phenomenon.

2008

Uranium Isotopes Fingerprint Biotic Reduction

Rizlan Bernier-Latmani, Malgorzata Alicja Stylo, Yuheng Wang

Knowledge of paleo-redox conditions in the Earth's history provides a window into events that shaped the evolution of life on our planet. The role of microbial activity in paleo-redox processes remains unexplored due to the inability to discriminate biotic from abiotic redox transformations in the rock record. The ability to deconvolute these two processes would provide a means to identify environmental niches in which microbial activity was prevalent at a specific time in paleo-history and to correlate specific biogeochemical events with the corresponding microbial metabolism. Here, we demonstrate that the isotopic signature associated with microbial reduction of hexavalent uranium (U), i.e., the accumulation of the heavy isotope in the U(IV) phase, is readily distinguishable from that generated by abiotic uranium reduction in laboratory experiments. Thus, isotope signatures preserved in the geologic record through the reductive precipitation of uranium may provide the sought-after tool to probe for biotic processes. Because uranium is a common element in the Earth's crust and a wide variety of metabolic groups of microorganisms catalyze the biological reduction of U(VI), this tool is applicable to a multiplicity of geological epochs and terrestrial environments. The findings of this study indicate that biological activity contributed to the formation of many authigenic U deposits, including sandstone U deposits of various ages, as well as modern, Cretaceous, and Archean black shales. Additionally, engineered bioremediation activities also exhibit a biotic signature, suggesting that, although multiple pathways may be involved in the reduction, direct enzymatic reduction contributes substantially to the immobilization of uranium.

Natl Acad Sciences2015