Identifying Olivine Composition in Tyrrhena Terra, Mars, Using Orbital Mid-Infrared Data

Magnificent rock / Crater floors of melted Mars / Hold the olivine

Characterizing the Aqueous Geochemical History at Tyrrhena Terra, Mars

Tyrrhena Terra is an intriguing region of Mars extending from the southern part of Isidis Basin at the Libya Montes southward to Hellas Basin. Noachian and Hesperian basement rocks are covered by Syrtis lavas, especially in the northwestern part of Tyrrhena Terra and the surface is carved by craters and fluvial features. The central region is marked by the craters Jarry-Desloges, Owen, and Briault, and contains abundant Fe/Mg-rich phyllosilicates and olivine-bearing outcrops in Noachian-Hesperian terrain [1,2]. Many of the phyllosilicates in this region are located in crater ejecta and in central crater mounds, consistent with uplift of ancient materials, but some are present in dissected terrains. We are investigating the mineralogy and geology of this region through a coordinated study using TES, THEMIS, CRISM multispectral strips, CTX and HRSC imagery, and HRSC digital elevation models at a regional scale, as well as CRISM targeted images and HiRISE views of the surface at a closer scale. The phyllosilicate spectra across the central Tyrrhena Terra region (see attached figure) are most consistent with chlorite, Fe/Mg-smectite, and mixed smectite-chlorite. A few hydrated silica and zeolite outcrops are also present. This mineralogy is consistent with higher temperature processes than the primarily Fe/Mg-smectite and carbonate spectra observed in the Libya Montes region [3,4]. A few sites towards the east of our study site contain more Fe/Mg-smectite than chlorite and additional hydrated phases including sulfates, which likely represent a different formation environment. Ongoing investigations of the targeted CRISM images at the eastern part of this area are characterizing the stratigraphy of these aqueous units and their association with higher temperature units towards the west and smectite-carbonate units towards the north

Binding of ²³⁹Pu and ⁹⁰Sr to organic colloids in soil solutions: evidence from a field experiment.

Colloidal transport has been shown to enhance the migration of plutonium in groundwater downstream from contaminated sites, but little is known about the adsorption of ⁹⁰Sr and plutonium onto colloids in the soil solution of natural soils. We sampled soil solutions using suction cups, and separated colloids using ultrafiltration to determine the distribution of ²³⁹Pu and ⁹⁰Sr between the truly dissolved fraction and the colloidal fraction of the solutions of three Alpine soils contaminated only by global fallout from the nuclear weapon tests. Plutonium was essentially found in the colloidal fraction (>80%) and probably associated with organic matter. A significant amount of colloidal ⁹⁰Sr was detected in organic-rich soil solutions. Our results suggest that binding to organic colloids in the soil solutions plays a key role with respect to the mobility of plutonium in natural alpine soils and, to a lesser extent, to the mobility of ⁹⁰Sr

High-resolution reconstruction of the 20th century history of trace metals, major elements, and organic matter in sediments in a contaminated area of Lake Geneva, Switzerland

Toxic trace metals in lacustrine sediments are of major concern since they can be hazardous to biota and human health. A high-resolution multiproxy study, including trace metals and major elements (measured by ICP-MS and XRF), total organic carbon, mineral carbon, Hydrogen Index, Oxygen Index, and C/N ratios, was performed on a sediment core from Vidy Bay in Lake Geneva. This bay has been affected by hazardous compounds released via the sewage effluent of a major wastewater treatment plant (WWTP). Anthropogenic trace metals, such as Pb, Cd, Cu, Zn, and Hg, increased following the industrial revolution in Europe. The highest amounts of these toxic metals, together with Ni, Cr, Co, Ag, Bi, and Fe, were recorded in sediments from 1964, the date of the WWTP implementation. During this period, all trace elements exceeded the sediment quality guideline “probable effect concentration” (PEC), with the following maximum concentrations (in mg kg): Pb 4000, Cd 23, Cu 1200, Zn 8600, Hg 11, Ni 140, Cr 270, Ag 130, and Bi 310. The geochemistry of detrital elements (Al, Si, Ca, Ti, K, Zr, Rb, and Sr), as well as S, Fe, P, and the nature and quality of organic matter were clearly also affected by the effluent. The sedimentary record revealed that, after some improvements in the wastewater treatment processes and the relocation of the outlet pipe, the sediments tended to return to concentrations similar to those prevailing before the WWTP implementation. However, despite the reduction in the contamination load from the WWTP, which could be reinforced with the construction of a new plant in the near future, the sediments deposited in Vidy Bay represent a major contaminant legacy that constitutes a potential threat to the lake biota in the case of sediment remobilization.Peer Reviewe

Noise identification and sampling frequency determination for precise Pb isotopic measurements by quadrupole-based inductively coupled plasma mass spectrometry

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