Water Content of Earth's Continental Mantle Is Controlled by the Circulation of Fluids or Melts

A key mission of the ARES Directorate at JSC is to constrain models of the formation and geological history of terrestrial planets. Water is a crucial parameter to be measured with the aim to determine its amount and distribution in the interior of Earth, Mars, and the Moon. Most of that "water" is not liquid water per se, but rather hydrogen dissolved as a trace element in the minerals of the rocks at depth. Even so, the middle layer of differentiated planets, the mantle, occupies such a large volume and mass of each planet that when it is added at the planetary scale, oceans worth of water could be stored in its interior. The mantle is where magmas originate. Moreover, on Earth, the mantle is where the boundary between tectonic plates and the underlying asthenosphere is located. Even if mantle rocks in Earth typically contain less than 200 ppm H2O, such small quantities have tremendous influence on how easily they melt (i.e., the more water there is, the more magma is produced) and deform (the more water there is, the less viscous they are). These two properties alone emphasize that to understand the distribution of volcanism and the mechanism of plate tectonics, the water content of the mantle must be determined - Earth being a template to which all other terrestrial planets can be compared

Metasomatic Control of Water in Garnet and Pyroxene from Kaapvaal Craton Mantle Xenoliths

Fourier transform infrared spectrometry (FTIR) and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) were used to determine water, rare earth (REE), lithophile (LILE), and high field strength (HFSE) element contents in garnet and pyroxene from mantle xenoliths, Kaapvaal craton, southern Africa. Water enters these nominally anhydrous minerals as protons bonded to structural oxygen in lattice defects. Pyroxene water contents (150-400 ppm in clinopyroxene; 40-250 ppm in orthopyroxene) correlate with their Al, Fe, Ca and Na and are homogeneous within a mineral grains and a xenolith. Garnets from Jagersfontein are chemically zoned for Cr, Ca, Ti and water contents. Garnets contain 0 to 20 ppm H2 Despite the fast diffusion rate of H in mantle m inerals, the observations above indicate that the water contents of mantle xenolith minerals were not disturbed during kimberlite entrainment and that the measured water data represent mantle values. Trace elements in all minerals show various degrees of light REE and LILE enrichments indicative of minimal to strong metasomatism. Water contents of peridotite minerals from the Kaapvaal lithosphere are not related to the degree of depletion of the peridotites. Instead, metasomatism exerts a clear control on the amount of water of mantle minerals. Xenoliths from each location record specific types of metasomatism with different outcomes for the water contents of mantle minerals. At pressures . 5.5 GPa, highly alkaline melts metasomatized Liqhobong and Kimberley peridotites, and increased the water contents of their olivine, pyroxenes and garnet. At higher pressures, the circulation of ultramafic melts reacting with peridotite resulted in co-variation of Ca, Ti and water at the edge of garnets at Jagersfontein, overall decreasing their water content, and lowered the water content of olivines at Finsch Mine. The calculated water content of these melts varies depending on whether the water content of the peridotite (2 wt% HO. 2O) or individual m inerals (<0.5-13 wt% H2O) are used, and also depend on the mineral-melt water partition coefficients. These metasomatic events are thought to have occurred during the Archean and Proterozoic, meaning that the water contents measured here have been preserved since that time and can be used to investigate viscocity and longevity of cratonic mantle roots

Aquatic Bacterial Communities Associated With Land Use and Environmental Factors in Agricultural Landscapes Using a Metabarcoding Approach

This study applied a 16S rRNA gene metabarcoding approach to characterize bacterial community compositional and functional attributes for surface water samples collected within, primarily, agriculturally dominated watersheds in Ontario and Québec, Canada. Compositional heterogeneity was best explained by stream order, season, and watercourse discharge. Generally, community diversity was higher at agriculturally dominated lower order streams, compared to larger stream order systems such as small to large rivers. However, during times of lower relative water flow and cumulative 2-day rainfall, modestly higher relative diversity was found in the larger watercourses. Bacterial community assemblages were more sensitive to environmental/land use changes in the smaller watercourses, relative to small-to-large river systems, where the proximity of the sampled water column to bacteria reservoirs in the sediments and adjacent terrestrial environment was greater. Stream discharge was the environmental variable most significantly correlated (all positive) with bacterial functional groups, such as C/N cycling and plant pathogens. Comparison of the community structural similarity via network analyses helped to discriminate sources of bacteria in freshwater derived from, for example, wastewater treatment plant effluent and intensity and type of agricultural land uses (e.g., intensive swine production vs. dairy dominated cash/livestock cropping systems). When using metabarcoding approaches, bacterial community composition and coexisting pattern rather than individual taxonomic lineages, were better indicators of environmental/land use conditions (e.g., upstream land use) and bacterial sources in watershed settings. Overall, monitoring changes and differences in aquatic microbial communities at regional and local watershed scales has promise for enhancing environmental footprinting and for better understanding nutrient cycling and ecological function of aquatic systems impacted by a multitude of stressors and land uses

A comparison of enrichment and direct-plating methods for isolation of <em>Listeria monocytogenes</em> from surface water

EA MERS CT3 Enjeu 3International audienceListeria monocytogenes is a facultative intracellular pathogen distributed in the environment. Reference isolation methods include an enrichment step. We compared 2 protocols: one based on enrichment and the other on direct plating, with respect to the efficiency of isolation of L. monocytogenes from surface water samples. From March to May 2006, 126 surface water samples were collected biweekly from 24 discrete sampling sites located in the South Nation River basin (Ontario). Presumptive Listeria spp. were isolated using the 2 methods, and L. monocytogenes isolates were confirmed based on colony morphology and amplification of 3 pathogenicity genes: iap, inlA, and hlyA. Listeria monocytogenes was detected in 31 water samples using the enrichment approach and in 27 using the direct-plating approach, with only 13 samples positive using both approaches. No correlation was observed between the ability of the enrichment procedure to fail in the detection of the pathogenic bacterium and the abundance of several indicator bacteria. The proportion of samples carrying isolates from serovar groups 1/2a, 3a; 1/2b, 3b, 7; 4b, 4d, 4e; and Listeria spp. was significantly different between the 2 approaches. This data indicate that a direct-plating approach would be suitable for the detection of L. monocytogenes in water samples, but that enrichment and direct-plating protocols both have specific biases.Listeria monocytogenes est un pathogène intracellulaire facultatif répandu dans l’environnement. La méthoded’isolement de référence inclut une étape d’enrichissement. Nous avons comparé 2 protocoles, basés sur un enrichissementou un étalement direct, pour l’efficacitéd’isolement de L. monocytogenes dans des échantillons d’eau de surface. De mars à mai 2006, 126 échantillons d’eau, provenant de 24 sites d’échantillonnage situés sur le bassin de la rivière South Nation (Ontario), ont été prélevés bimensuellement. Les colonies de Listeria spp. présumées ont été isolées par les 2 méthodes et les isolats confirmés sur la base de la morphologie des colonies et l’amplification de 3 gènes impliqués dans la pathogénicité de L. monocytogenes : iap, inlA et hlyA. Listeria monocytogenes a été détecté dans 31 échantillons par enrichissement et dans 27 échantillons par étalement direct, avec seulement 13 échantillons positifs par l’utilisation des 2 approches. Aucune corrélation n’a été observée entre la détection du pathogène et l’abondance de plusieurs bactéries indicatrices. La proportion d’échantillons contenant des isolats appartenant aux groupes sérologiques 1/2a, 3a; 1/2b, 3b, 7; 4b, 4d, 4e et Listeria spp. était significativement différente entre les 2 approches. Ceci indique que l’étalement direct serait adapté a` la détection de L. monocytogenes dans des échantillons d’eau, mais que chacune des approches présente ses propres biais

Ar-Ar and U-Pb ages of Chelyabinsk and a re-evaluation of its impact chronology

The LL5 chondrite Chelyabinsk has had numerous isotopic studies since its fall in 2013. These data have been used to suggest ~8 impact events recorded from multiple isotopic systems (e.g., Ar-Ar, U–Pb, Sm-Nd, Rb-Sr, among others). We report details of Ar-Ar and U-Pb results and re-evaluate the geochronology of Chelyabinsk. Argon has the youngest Ar-Ar age recorded in meteorites, 25 ± 11 Ma, and an older resetting event at ~2550 Ma. The U-Pb analysis has an upper concordia age of 4456 ± 23 Ma and a lower concordia age of 184 ± 200 Ma. The lower concordia intercept represents a later thermal event (e.g., an impact), the most recent time that lead loss occurred, and could represent resetting by the youngest event recorded by Ar-Ar. Combining our data with literature results, we find strong evidence of at least four impact events (~4450, 2550, 1700, 25 Ma), with some evidence for two additional impacts (~3700, 1000 Ma).12 month embargo; published 01 Dec 2022.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Water Use and Conservation on a Free-Stall Dairy Farm

Livestock watering can represent as much as 20% of total agricultural water use in areas with intensive dairy farming. Due to an increased emphasis on water conservation for the agricultural sector, it is important to understand the current patterns of on-farm water use. This study utilized in situ water meters to measure the year-round on-farm pumped water (i.e., blue water) on a ~419 lactating cow confined dairy operation in Eastern Ontario, Canada. The average total water use for the farm was 90,253 ± 15,203 L day−1 and 33,032 m3 annually. Water use was divided into nutritional water (68%), parlour cleaning and operation (14%), milk pre-cooling (15%), barn cleaning, misters and other uses (3%). There was a positive correlation between total monthly water consumption (i.e., nutritional water) and average monthly temperature for lactating cows, heifers, and calves (R2 = 0.69, 0.84, and 0.85, respectively). The blue water footprint scaled by milk production was 6.19 L kg−1 milk or 6.41 L kg−1 fat-and-protein corrected milk (FPCM) including contributions from all animal groups and 5.34 L kg−1 milk (5.54 L kg−1 FPCM) when excluding the water consumption of non-lactating animals. By applying theoretical water conservation scenarios we show that a combination of strategies (air temperature reduction, complete recycling of milk-cooling water, and modified cow preparation protocol) could achieve a savings of 6229 m3 annually, a ~19% reduction in the total annual water use

Facilitating soil-and plant-water research through the use of TDR

The development of TDR for measurement of soil water content and electrical conductivity has resulted in a large shift in measurement methods for a breadth of soil and hydrological characterization efforts. TDR has also opened new possibilities for soil and plant research. Five examples show how TDR has enhanced our ability to conduct our soil- and plant-water research. (i) Oxygen is necessary for healthy root growth and plant development but quantitative evaluation of the factors controlling oxygen supply in soil depends on knowledge of the soil water content by TDR. With water content information we have modeled successfully some impact of tillage methods on oxygen supply to roots and their growth response. (ii) For field assessment of soil mechanical properties influencing crop growth, water content capability was added to two portable soil strength measuring devices; (a) A TDT (Time Domain Transmittivity)-equipped soil cone penetrometer was used to evaluate seasonal soil strengthwater content relationships. In conventional tillage systems the relationships are dynamic and achieve the more stable no-tillage relationships only relatively late in each growing season; (b) A small TDR transmission line was added to a modified sheargraph that allowed shear strength and water content to be measured simultaneously on the same sample. In addition, the conventional graphing procedure for data acquisition was converted to datalogging using strain gauges. Data acquisition rate was improved by more than a factor of three with improved data quality. (iii) How do drought tolerant plants maintain leaf water content? Non-destructive measurement of TDR water content using a flat serpentine triple wire transmission line replaces more lengthy procedures of measuring relative water content. Two challenges remain: drought-stressed leaves alter salt content, changing electrical conductivity, and drought induced changes in leaf morphology affect TDR measurements. (iv) Remote radar signals are reflected from within the first 2 cm of soil. Appropriate calibration of radar imaging for soil water content can be achieved by a parallel pair of blades separated by 8 cm, reaching 1.7 cm into soil and forming a 20 cm TDR transmission line. The correlation between apparent relative permittivity from TDR and synthetic aperture radar (SAR) backscatter coefficient was 0.57 from an airborne flyover. These five examples highlight the diversity in the application of TDR in soil and plant research

Node-dated phylogeny of 530 species included in T. gondii analysis.

The maximum clade credibility topology of 10,000 trees is shown. The inner panel depicts the species-level T. gondii prevalence over all available studies. The outer panel identifies the taxonomic families.</p

Reference list of publications for which <i>T</i>. <i>gondii</i> prevalence data was available for free-ranging wild and domesticated mammal populations.

Reference list of publications for which T. gondii prevalence data was available for free-ranging wild and domesticated mammal populations.</p