scholarly journals The Effects of Glacial Cover on Riverine Silicon Isotope Compositions in Chilean Patagonia

2020 ◽  
Vol 8 ◽  
Author(s):  
Helena V. Pryer ◽  
Jade E. Hatton ◽  
Jemma L. Wadham ◽  
Jon R. Hawkings ◽  
Laura F. Robinson ◽  
...  
Keyword(s):  
Silicon Isotope ◽  
Silicate Phase ◽  
Subglacial Environment ◽  
Chilean Patagonia ◽  
Positive Linear Correlation ◽  
Ultra Filtration ◽  
Glacial Cover ◽  
Si Isotope ◽  
River Catchments ◽  
Natural Laboratory

Proglacial rivers have been shown to have distinctive silicon (Si) isotope compositions, providing new insights into the mechanisms controlling Si cycling in the subglacial environment and suggesting terrestrial Si isotope exports may have varied between glacial and interglacial periods. However, Si isotope data are currently limited to a small number of glacial systems in the northern hemisphere, and it is unclear how compositions might vary across a spectrum of glacial influence. Using Chilean Patagonia as a unique natural laboratory, we present Si isotope compositions of 0.45 μm filtered (fSi), 0.02 μm filtered (DSi), and reactive amorphous (ASi) fractions from 40 river catchments with variable glacial cover and explore the key controls on Si cycling. The 0.45 μm filtered glacier-fed river samples displayed isotopically light compositions and a positive linear correlation with upstream glacial cover. This relationship was controlled by the inclusion of an isotopically light colloidal-nanoparticulate (0.02–0.45 μm) silicate phase that was only present in glacier-fed rivers and dominated Si budgets in these catchments. This phase was predominately composed of feldspars and its lability in seawater is uncertain, representing a significant unknown in resolving glacial Si isotope exports from this region. When the colloidal-nanoparticulates were removed from solution by ultra-filtration, the resultant DSi isotope compositions of glacier-fed catchments were not isotopically distinct from some non-glacial rivers and exhibited no clear relationship with glacial cover. The colloidal-nanoparticulate concentration of other weathering-sensitive elements (Li, Mg, Ba, Sr) also showed a linear relationship with glacial cover, suggesting that their isotopic compositions could be affected in a similar manner. These findings highlight the benefit of size-fractionated sampling and the need for more research to understand the lability of colloidal-nanoparticulate species, especially in glacier-fed rivers. Finally, we explore the controls on river ASi isotope compositions and show how including these reactive particulate phases is critical to quantifying terrestrial Si isotope budgets, both in Patagonia and other global regions.

scholarly journals The Influence of Glacial Cover on Riverine Silicon and Iron Exports in Chilean Patagonia

2020 ◽  
Vol 34 (12) ◽  
Author(s):  
Helena V. Pryer ◽  
Jon R. Hawkings ◽  
Jemma L. Wadham ◽  
Laura F. Robinson ◽  
Katharine R. Hendry ◽  
...  
Keyword(s):  
Chilean Patagonia ◽  
Glacial Cover

scholarly journals Silicon isotope measurement in zircon by laser ablation multiple collector inductively coupled plasma mass spectrometry

2020 ◽  
Vol 35 (8) ◽  
pp. 1597-1606
Author(s):  
Martin Guitreau ◽  
Abdelmouhcine Gannoun ◽  
Zhengbin Deng ◽  
Johanna Marin-Carbonne ◽  
Marc Chaussidon ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Laser Ablation ◽  
Inductively Coupled Plasma ◽  
Silicon Isotope ◽  
Nanosecond Laser ◽  
Inductively Coupled ◽  
Nanosecond Laser Ablation ◽  
Plasma Mass Spectrometry ◽  
Isotope Measurement ◽  
Si Isotope

This study reports the first Si isotope data measured in zircon using nanosecond laser ablation multiple collector inductively coupled plasma mass spectrometry.

scholarly journals Controls on the Silicon Isotope Composition of Diatoms in the Peruvian Upwelling

2021 ◽  
Vol 8 ◽  
Author(s):  
Patricia Grasse ◽  
Kristin Haynert ◽  
Kristin Doering ◽  
Sonja Geilert ◽  
Janice L. Jones ◽  
...  
Keyword(s):  
Water Column ◽  
Silicic Acid ◽  
Isotope Composition ◽  
Size Fraction ◽  
Strong Relationship ◽  
Silicon Isotope ◽  
Main Driver ◽  
Subsurface Waters ◽  
Minimum Zone ◽  
Si Isotope

The upwelling area off Peru is characterized by exceptionally high rates of primary productivity, mainly dominated by diatoms, which require dissolved silicic acid (dSi) to construct their frustules. The silicon isotope compositions of dissolved silicic acid (δ30SidSi) and biogenic silica (δ30SibSi) in the ocean carry information about dSi utilization, dissolution, and water mass mixing. Diatoms are preserved in the underlying sediments and can serve as archives for past nutrient conditions. However, the factors influencing the Si isotope fractionation between diatoms and seawater are not fully understood. More δ30SibSi data in today’s ocean are required to validate and improve the understanding of paleo records. Here, we present the first δ30SibSi data (together with δ30SidSi) from the water column in the Peruvian Upwelling region. Samples were taken under strong upwelling conditions and the bSi collected from seawater consisted of more than 98% diatoms. The δ30SidSi signatures in the surface waters were higher (+1.7‰ to +3.0‰) than δ30SibSi (+1.0‰ to +2‰) with offsets between diatoms and seawater (Δ30Si) ranging from −0.4‰ to −1.0‰. In contrast, δ30SidSi and δ30SibSi signatures were similar in the subsurface waters of the oxygen minimum zone (OMZ) as a consequence of a decrease in δ30SidSi. A strong relationship between δ30SibSi and [dSi] in surface water samples supports that dSi utilization of the available pool (70 and 98%) is the main driver controlling δ30SibSi. A comparison of δ30SibSi samples from the water column and from underlying core-top sediments (δ30SibSi_sed.) in the central upwelling region off Peru (10°S and 15°S) showed good agreement (δ30SibSi_sed. = +0.9‰ to +1.7‰), although we observed small differences in δ30SibSi depending on the diatom size fraction and diatom assemblage. A detailed analysis of the diatom assemblages highlights apparent variability in fractionation among taxa that has to be taken into account when using δ30SibSi data as a paleo proxy for the reconstruction of dSi utilization in the region.

The feedback between climate and weathering

2008 ◽  
Vol 72 (1) ◽  
pp. 317-320 ◽  
Author(s):  
S. R. Gislason ◽  
E. H. Oelkers ◽  
E. S. Eiriksdottir ◽  
M. I. Kardjilov ◽  
G. Gisladottir ◽  
...  
Keyword(s):  
Chemical Weathering ◽  
Mean Annual Temperature ◽  
Weathering Rate ◽  
North East ◽  
Temperature And Precipitation ◽  
Glacial Cover ◽  
Positive Correlations ◽  
Mechanical Weathering ◽  
River Catchments

AbstractLong-term climate moderation is commonly attributed to chemical weathering; the greater the temperature and precipitation the faster the weathering rate. To test this widely-held hypothesis, we performed a field study and determined the weathering rates of eight nearly pristine north-east Iceland river catchments with varying glacial cover over 44 y. Statistically significant linear positive correlations were found between mean annual temperature and chemical weathering in all eight catchments and between mean annual temperature and mechanical weathering and runoff in seven of the eight catchments. The runoff, mechanical weathering flux, and chemical weathering fluxes in these catchments are found to increase from 6 to 16%, 8 to 30%, and 4 to 14%, respectively, depending on the catchment for each degree of temperature increase. Positive correlations were found between time and mechanical and chemical weathering for all catchments. In summary, these results demonstrate a significant feedback between climate and Earth surface weathering, and suggest that this weathering rate is currently increasing with time due to global warming.

scholarly journals Silicon Isotope Signatures of Radiolaria Reveal Taxon-Specific Differences in Isotope Fractionation

2021 ◽  
Vol 8 ◽  
Author(s):  
Kristin Doering ◽  
Claudia Ehlert ◽  
Katharina Pahnke ◽  
Martin Frank ◽  
Ralph Schneider ◽  
...  
Keyword(s):  
Isotope Fractionation ◽  
Critical Role ◽  
Silicon Isotope ◽  
Intermediate Water ◽  
Fractionation Factor ◽  
Mean Values ◽  
Promising Tool ◽  
Cycle Plays ◽  
Si Isotope ◽  
Species Specific

The global silicon (Si) cycle plays a critical role in regulating the biological pump and the carbon cycle in the oceans. A promising tool to reconstruct past dissolved silicic acid (DSi) concentrations is the silicon isotope signature of radiolaria (δ30Sirad), siliceous zooplankton that dwells at subsurface and intermediate water depths. However, to date, only a few studies on sediment δ30Sirad records are available. To investigate its applicability as a paleo proxy, we compare the δ30Sirad of different radiolarian taxa and mixed radiolarian samples from surface sediments off Peru to the DSi distribution and its δ30Si signatures (δ30SiDSi) along the coast between the equator and 15°S. Three different radiolarian taxa were selected according to their specific habitat depths of 0–50 m (Acrosphaera murrayana), 50–100 m (Dictyocoryne profunda/truncatum), and 200–400 m (Stylochlamydium venustum). Additionally, samples containing a mix of species from the bulk assemblage covering habitat depths of 0 to 400 m have been analyzed for comparison. We find distinct δ30Sirad mean values of +0.70 ± 0.17‰ (Acro; 2 SD), +1.61 ± 0.20 ‰ (Dictyo), +1.19 ± 0.31 ‰ (Stylo) and +1.04 ± 0.19 ‰ (mixed radiolaria). The δ30Si values of all individual taxa and the mixed radiolarian samples indicate a significant (p < 0.05) inverse relationship with DSi concentrations of their corresponding habitat depths. However, only δ30Si of A. murrayana are correlated to DSi concentrations under normally prevailing upwelling conditions. The δ30Si of Dictyocoryne sp., Stylochlamydium sp., and mixed radiolaria are significantly correlated to the lower DSi concentrations either associated with nutrient depletion or shallower habitat depths. Furthermore, we calculated the apparent Si isotope fractionation between radiolaria and DSi (Δ30Si ∼ 30ε = δ 30Sirad − δ 30SiDSi) and obtained values of −1.18 ± 0.17 ‰ (Acro), −0.05 ± 0.25 ‰ (Dictyo), −0.34 ± 0.27 ‰ (Stylo), and −0.62 ± 0.26 ‰ (mixed radiolaria). The significant differences in Δ30Si between the order of Nassellaria (A. murrayana) and Spumellaria (Dictyocoryne sp. and Stylochlamydium sp.) may be explained by order-specific Si isotope fractionation during DSi uptake, similar to species-specific fractionation observed for diatoms. Overall, our study provides information on the taxon-specific fractionation factor between radiolaria and seawater and highlights the importance of taxonomic identification and separation to interpret down-core records.

Direct Assessment of Effective Renal Plasma Flow from Renoscintigraphy with a Gamma Camera and an On-Line Computer

1981 ◽  
Vol 20 (06) ◽  
pp. 274-278
Author(s):  
J. Liniecki ◽  
J. Bialobrzeski ◽  
Ewa Mlodkowska ◽  
M. J. Surma
Keyword(s):  
Count Rate ◽  
Renal Plasma Flow ◽  
Early Period ◽  
Least Square Method ◽  
Least Square ◽  
Uptake Coefficient ◽  
Positive Linear Correlation ◽  
On Line ◽  
Best Fit ◽  
Plasma Activity

A concept of a kidney uptake coefficient (UC) of 131I-o-hippurate was developed by analogy from the corresponding kidney clearance of blood plasma in the early period after injection of the hippurate. The UC for each kidney was defined as the count-rate over its ROI at a time shorter than the peak in the renoscintigraphic curve divided by the integral of the count-rate curve over the "blood"-ROI. A procedure for normalization of both curves against each other was also developed. The total kidney clearance of the hippurate was determined from the function of plasma activity concentration vs. time after a single injection; the determinations were made at 5, 10, 15, 20, 30, 45, 60, 75 and 90 min after intravenous administration of 131I-o-hippurate and the best-fit curve was obtained by means of the least-square method. When the UC was related to the absolute value of the clearance a positive linear correlation was found (r = 0.922, ρ > 0.99). Using this regression equation the clearance could be estimated in reverse from the uptake coefficient calculated solely on the basis of the renoscintigraphic curves without blood sampling. The errors of the estimate are compatible with the requirement of a fast appraisal of renal function for purposes of clinical diagknosis.

TEKNOLOGI PENYEDIAAN AIR MINUM UNTUK KEADAAN TANGGAP DARURAT

2018 ◽  
Vol 6 (1) ◽  
Author(s):  
Arie Herlambang
Keyword(s):  
Water Quality ◽  
Emergency Response ◽  
Distribution Systems ◽  
Treatment Plant ◽  
Piping System ◽  
Process Technology ◽  
Treatment Technology ◽  
Disaster Victims ◽  
Ultra Filtration ◽  
Quality Water

In the event of natural disasters such as earthquakes, tsunamis, landslides, floods and droughts, water occupies a key role in disaster relief. The presence of water is important for drinking, cooking and support the refugee areas of environmental sanitation and avoiding disaster victims of diseases waterborn disease. Water problem in disaster conditions may occur partly as a result: the disturbance of water sources because change of water quality, to become turbid or salty, the destruction of a piping system, treatment plant damage, disruption of distribution systems, or the scarcity of water in evacuation areas. Introduction of water quality becomes important to determine which process technology will be used and saved investments in emergency conditions. Priority handling of clean water usually comes first in the refugee areas with communal system, because the need of water for bathing, washing and toilet is big enough, while for a drink in the early events during disaster dominated by bottled water, but for their long-term, they have to boil water. For remote areas and difficult to reach individuals who usually use  system more simple and easily operated. Water Supply Technology for emergency response has the characteristic 1). Able to operate with all sorts of water conditions (flexible adaptable), 2). Can be operated easily, 3). Does not require much maintenance, 4). Little use of chemicals, and 5). Portable and easy removable (Mobile System). Keywords :  Water Quality, Water Treatment Technology, Drinking Water, Emergency Response, filtration, ceramic filtration, Ultra filtration, Reverse Osmosis, Ultraviolet Sterilizer, Ozonizer, Disinfection.

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