Biogeochemical Stoichiometry of Antarctic Dry Valley Ecosystems

Among aquatic and terrestrial landscapes of the McMurdo Dry Valleys, Antarctica, ecosystem stoichiometry ranges from values near the Redfield ratios for C:N:P to nutrient concentrations in proportions far above or below ratios necessary to support balanced microbial growth. This polar desert provides an opportunity to evaluate stoichiometric approaches to understand nutrient cycling in an ecosystem where biological diversity and activity are low, and controls over the movement and mass balances of nutrients operate over 10–10⁶ years. The simple organisms (microbial and metazoan) comprising dry valley foodwebs adhere to strict biochemical requirements in the composition of their biomass, and when activated by availability of liquid water, they influence the chemical composition of their environment according to these ratios. Nitrogen and phosphorus varied significantly in terrestrial and aquatic ecosystems occurring on landscape surfaces across a wide range of exposure ages, indicating strong influences of landscape development and geochemistry on nutrient availability. Biota control the elemental ratio of stream waters, while geochemical stoichiometry (e.g., weathering, atmospheric deposition) evidently limits the distribution of soil invertebrates. We present a conceptual model describing transformations across dry valley landscapes facilitated by exchanges of liquid water and biotic processing of dissolved nutrients. We conclude that contemporary ecosystem stoichiometry of Antarctic Dry Valley soils, glaciers, streams, and lakes results from a combination of extant biological processes superimposed on a legacy of landscape processes and previous climates

State of the Antarctic and Southern Ocean Climate System

This paper reviews developments in our understanding of the state of the Antarctic and Southern Ocean climate and its relation to the global climate system over the last few millennia. Climate over this and earlier periods has not been stable, as evidenced by the occurrence of abrupt changes in atmospheric circulation and temperature recorded in Antarctic ice core proxies for past climate. Two of the most prominent abrupt climate change events are characterized by intensification of the circumpolar westerlies (also known as the Southern Annular Mode) between ∼6000 and 5000 years ago and since 1200–1000 years ago. Following the last of these is a period of major trans-Antarctic reorganization of atmospheric circulation and temperature between A.D. 1700 and 1850. The two earlier Antarctic abrupt climate change events appear linked to but predate by several centuries even more abrupt climate change in the North Atlantic, and the end of the more recent event is coincident with reorganization of atmospheric circulation in the North Pacific. Improved understanding of such events and of the associations between abrupt climate change events recorded in both hemispheres is critical to predicting the impact and timing of future abrupt climate change events potentially forced by anthropogenic changes in greenhouse gases and aerosols. Special attention is given to the climate of the past 200 years, which was recorded by a network of recently available shallow firn cores, and to that of the past 50 years, which was monitored by the continuous instrumental record. Significant regional climate changes have taken place in the Antarctic during the past 50 years. Atmospheric temperatures have increased markedly over the Antarctic Peninsula, linked to nearby ocean warming and intensification of the circumpolar westerlies. Glaciers are retreating on the peninsula, in Patagonia, on the sub-Antarctic islands, and in West Antarctica adjacent to the peninsula. The penetration of marine air masses has become more pronounced over parts of West Antarctica. Above the surface, the Antarctic troposphere has warmed during winter while the stratosphere has cooled year-round. The upper kilometer of the circumpolar Southern Ocean has warmed, Antarctic Bottom Water across a wide sector off East Antarctica has freshened, and the densest bottom water in the Weddell Sea has warmed. In contrast to these regional climate changes, over most of Antarctica, near-surface temperature and snowfall have not increased significantly during at least the past 50 years, and proxy data suggest that the atmospheric circulation over the interior has remained in a similar state for at least the past 200 years. Furthermore, the total sea ice cover around Antarctica has exhibited no significant overall change since reliable satellite monitoring began in the late 1970s, despite large but compensating regional changes. The inhomogeneity of Antarctic climate in space and time implies that recent Antarctic climate changes are due on the one hand to a combination of strong multidecadal variability and anthropogenic effects and, as demonstrated by the paleoclimate record, on the other hand to multidecadal to millennial scale and longer natural variability forced through changes in orbital insolation, greenhouse gases, solar variability, ice dynamics, and aerosols. Model projections suggest that over the 21st century the Antarctic interior will warm by 3.4° ± 1°C, and sea ice extent will decrease by ∼30%. Ice sheet models are not yet adequate enough to answer pressing questions about the effect of projected warming on mass balance and sea level. Considering the potentially major impacts of a warming climate on Antarctica, vigorous efforts are needed to better understand all aspects of the highly coupled Antarctic climate system as well as its influence on the Earth\u27s climate and oceans

Rare gases in Samoan xenoliths

The rare gas isotopic compositions of residual harzburgite xenoliths from Savai'i (SAV locality) and an unnamed seamount south of the Samoan chain (PPT locality) provide important constraints on the rare gas evolution of the mantle and atmosphere. Despite heterogeneous trace element compositions, the rare gas characteristics of the xenoliths from each of the two localities are strikingly similar. SAV and PPT xenoliths have ^3He/^4He ratios of 11.1 ± 0.5 R_A and 21.6 ± 1 R_A, respectively; this range is comparable to the ^3He/^4He ratios in Samoan lavas and clearly demonstrates that they have trapped gases from a relatively undegassed reservoir. The neon results are not consistent with mixing between MORB and a plume source with an atmospheric signature. Rather, the neon isotopes reflect either a variably degassed mantle (with a relative order of degassing of Loihi < PPT < Reunion < SAV < MORB), or mixing between the Loihi source and MORB. The data supports the conclusions of Honda et al. that the ^(20)Ne/^(22)Ne ratio in the mantle more closely resembles the solar ratio than the atmospheric one. ^(40)Ar/^(36)Ar ratios in the least contaminated samples range from 4,000 to 12,000 with the highest values in the 22 R_A PPT xenoliths. There is no evidence for atmospheric ^(40)Ar/^(36)Ar ratios in the mantle source of these samples, which indicates that the lower mantle may have ^(40)Ar/^(36)Ar ratios in excess of 5,000. Xenon isotopic anomalies in ^(129)Xe and ^(136)Xe are as high as 6%, or about half of the maximum MORB excess and are consistent with the less degassed nature of the Samoan mantle source. These results contradict previous suggestions that the high ^3He/^4He mantle has a near-atmospheric heavy rare gas isotopic composition

Mantle neon and atmospheric contamination

The apparent distinction between atmospheric and mantle ^(20)Ne/^(22)Ne ratios may provide a technique to quantify air contamination in mantle-derived materials. In the absence of mantle nuclear reactions, which produce either ^(20)Ne or ^(22)Ne in substantial quantities, it is likely that the entire mantle is characterized by a single, uniform ^(20)Ne/^(22)Ne ratio; a value of around 12.5 is suggested by analyses of MORBs, OIBs, diamonds and xenoliths. If this premise is correct, then any measured ^(20)Ne/^(22)Ne ratios in mantle samples that are lower than this must result from addition of an air component, with ^(20)Ne/^(22)Ne= 9.8. This is most likely a syn- or post-eruptive contaminant. The degree of air contamination inferred from ^(20)Ne/^(22)Ne ratios is generally small for diamonds, but is increasingly significant for MORBs and OIBs; many OIB's may carry > 90% air neon. We calculated “air-neon corrected” ^(21)Ne/^(22)Ne and ^(40)Ar/^(36)Ar ratios for the highly degassed MORB mantle and for the less degassed (high ^3He/^4He) “plume” reservoir. The inferred MORB composition is indistinguishable from measurements of some gas-rich glasses. The calculated plume composition is similar to the least air-like measurements from ocean islands, but is less air-like than has been proposed previously. This plume composition is not consistent with a completely undegassed reservoir. From these corrected mantle compositions, we calculated the relative time-integrated rare gas abundances in the mantle, using a simple evolutionary model, which simultaneously considers the isotopic compositions of He, Ne, Ar and Xe. The model shows that both MORB and plume reservoirs have evolved with nearly solar elemental abundances. This provides strong support to suggestions based on Ne isotopes that the Earth accreted with gases nearly solar in composition. Importantly, the inferred mantle Ne/Ar ratios are much higher than atmospheric, which is consistent with simultaneous fractionation of both the atmospheric neon isotope ratio and the Ne/Ar ratio by massive hydrodynamic escape. Mixing between MORB and plume reservoirs (with our calculated elemental and isotopic abundances), plus varying amounts of added air, can account for the rare gases in nearly all mantle-derived rocks

The impact of the cycling vat inlet’s shape on the process of forming the cone of substitute sediment

Podczas procesu klarowania brzeczki piwnej w kadzi wirowej dobór odpowiedniej konstrukcji oraz parametrów procesów gwarantuje prawidłowy przebieg oddzielenia osadu gorącego od brzeczki. W pracy przedstawiono wyniki analizy wpływu dwóch nowatorskich konstrukcji otworów wlotowych w kadzi wirowej na czasy występowania poszczególnych etapów formowania się stożka osadu zastępczego. W wyniku eksperymentu wykazano, iż użycie zaprojektowanych dysz znacznie skróciło czas zjawiska formowania się stożka osadu. Najbardziej skuteczny w realizacji procesu klarowania okazał się otwór wlotowy o konstrukcji dyszy płaskiej.Suitable construction and parameters for the process of separating hot trub from wort ensure its proper conduct. The presented work is an analysis of impact of two innovative inlet constructions on the timing of occurrence of consecutive phases of forming the cone of substitute sediment in a cycling vat. As a result of the experiment, it has been proved that using the nozzles of our design has significantly shortened the time it takes to form the break cone. During the execution of the process of separation, the flat nozzle inlet has proved as the most effective

Formation phases of a sediment cone inside a test tank of a whirlpool vat

Artykuł stanowi prezentację wyników badań eksperymentalnych przepływu mieszaniny separowanej w zbiorniku laboratoryjnej kadzi wirowej. Przedmiotem badań były charakterystyczne etapy formowania się stożka osadu w zależności od umiejscowienia (wysokości) otworu wlotowego i prędkości napełniania. Badania eksperymentalne zostały wykonane z wykorzystaniem zbiornika modelowego kadzi wirowej (tzw. whirlpoola) o pojemności V=2 hl i średnicy D=640 mm. W wyniku przeprowadzonych doświadczeń ustalono, iż w zjawisku formowania się stożka można wydzielić pewne charakterystyczne stany. W ramach przeprowadzonych badań porównano czasy ich występowania, a poprzez ich porównanie określono najkorzystniejsze prędkości napełniania, a także najkorzystniejsze wysokości umiejscowienia otworu wlotowego.The article presents results of the experimental research on the flow of mixture separated inside a laboratory cycling vat. The specific stages of forming the sediment cone depending on the position of the inlet (the placement height) and the speed of filling were the subject of the research. The research was carried out using a cycling vat (also called a whirlpool) scale model with capacity of V = 2hl and diameter of D = 640 mm. As a result of the experiments it was determined that as a part of the phenomenon of forming the cone, a few specific stages can be distinguished. The research involved a comparison of their timing, which allowed determination of the optimal speed of filling as well as the best height of placing the inlet

Wpływ kąta pochylenia zbiornika kadzi wirowej na położenie stożka osadu zastępczego

The article presents the results of the experimental research on the placement of the cone of substitute sediment at the bottom of the laboratory whirlpool tank with capacity of V=2 hl and diameter D=640 mm. The subject of the research was the influence of the whirlpool tilt angle on the process of forming the cone of break. Different tilt angles of the tank's inlet were also taken into account and, for each characteristic states of forming the cone of break were registered. The research led to finding a tilt angle beneficial in terms of movement of the cone of substitute sediment in comparison to cycling in a tank without any tilt.W artykule przedstawiono wyniki badań eksperymentalnych dotyczących umiejscowienia stożka osadu zastępczego na dnie zbiornika laboratoryjnej kadzi wirowej (tzw. whirlpoola) o pojemności V=2 hl i średnicy D=640 mm. Przedmiotem badań był wpływ kąta pochylenia zbiornika kadzi wirowej na formowanie się stożka osadu. Dodatkowo uwzględniono warianty odchylenia zbiornika względem otworu wlotowego. Dla poszczególnych wariantów zarejestrowano występowanie stanów charakterystycznych formowania się stożka osadu. Przeprowadzone doświadczenia pozwoliły stwierdzić, iż istnieje wariant pochylenia zbiornika whirlpoola, który jest korzystny ze względu na przemieszczenie uformowanego się stożka osadu zastępczego w odniesieniu do wirowania w zbiorniku niepochylonym

Technological and quality aspects of brewers wort clarification with the use of carrageenan

W pracy przedstawiono wyniki analizy parametrów jakościowych brzeczek poddanych wstępnej klaryfikacji z zastosowaniem karagenu. Celem przeprowadzonych badań było określenie wpływu stosowania karagenu na jakość brzeczki oraz przebieg procesu jej fermentacji. Karagen dodawano do wrzącej brzeczki słodowej w postaci wodnej zawiesiny w ilości 50, 100 i 200 mg·l⁻¹. Uzyskane wyniki pozwoliły stwierdzić, iż zastosowanie karagenu do wstępnej klaryfikacji w stężeniu 50 mg·l⁻¹ zdecydowanie poprawia klarowność brzeczki piwnej o ekstrakcie 10%. Jednakże nie miało to istotnego wpływu na przebieg fermentacji. Zastosowanie karagenu spowodowało obniżenie barwy brzeczek z ok. 11 EBC, w przypadku brzeczki kontrolnej, do ok. 7,5–8,0 w brzeczkach klarowanych karagenem w ilości 50 i 100 mg·l⁻¹.Colloidal stability of beer is one of the key factors ensuring a good visual impact of the product on the customers. Traditionally, it used to be achieved by a long period of maintaining beer at low temperature, in the process called lagering. Nowadays there is a rising interest in application of various types of auxiliary materials to ensure the colloidal stability of beer. Carrageenan is a type of linear polysaccharide extracted from red seaweeds. It is used as an auxiliary material used to facilitate clarification of wort at the stage of brew house operations. In the study we analyzed the quality parameters of wort and beer, after applying the clarification with the use of carrageenan. The aim of the work was to determine the effects of carrageenan added in various amounts, on the wort quality, course of the fermentation process and some physico-chemical parameters of the product. Carrageenan was added to the wort during boiling, in the form of an aqueous suspension, in order to allow for an equal distribution of the polysaccharide within the volume of the wort. It was added to reach the amount of 50,100 and 200 mg·l⁻¹. We found that the use of carrageenan in a concentration of 50 mg·l⁻¹ was the most appropriate for clarification of wort, in terms of the clarity and the amount of trub created. The haze of wort clarifi ed with carrageenan (50 mg·l⁻¹) was more than three times lower than in the reference sample (10 EBC haze units as compared with ca. 34 EBC). At the same time the amount of trub created was the lowest at this dose of carrageenan. Higher amount of carrageenan caused an excessive creation of the trub, which in consequence may lead to severe losses during industrial wort production. The application of carrageenan caused a decrease of wort colour, giving a 7.5–8.0 EBC (in case of 50 and 100 mg·l⁻¹), as compared with ca. 11 EBC in the reference wort. No significant impact on the course of fermentation was noted. The attenuation of wort clarified with carrageenan was the same as the reference wort, around 72%

Substitute sediment separation in a cycling vat equipped with a sediment plate

W pracy przedstawiono wyniki badań eksperymentalnych dotyczących przepływu separowanej mieszaniny wody i osadu zastępczego w zbiorniku laboratoryjnej kadzi wirowej – whirlpool, o pojemności V=2 hl i średnicy D=640 mm. Przedmiotem badań było określenie czasu trwania charakterystycznych etapów (stanów) formowania się stożka osadu zastępczego w zależności od wysokości otworu wlotowego oraz zastosowanej modyfikacji kształtu dna zbiornika w porównaniu do jego konstrukcji klasycznej. W ramach przeprowadzonych badań porównano czasy występowania stanów charakterystycznych formowania się stożka osadu dla 6 wariantów doświadczenia. W wyniku przeprowadzonych doświadczeń stwierdzono, że użycie elementu zabudowy wewnętrznej w whirlpoolu nie zakłóca rotacji mieszaniny podczas wirowania. Nie zarejestrowano również znacznych odchyleń w uzyskanych wartościach czasów (stanów) charakterystycznych formowania się stożka osadu w porównaniu z konstrukcją klasyczną. Opracowane rozwiązanie może, w warunkach przemysłowych, ułatwić spływ brzeczki i lepsze osuszanie stożka osaduThis paper presents results of the experimental research on flows in a whirlpool laboratory cycling vat’s tank (with the capacity of V=2 hl and the diameter of D=640 mm) filled with water and substitute sediment. The main subject of the research were the timings of the characteristic stages of the substitute sediment cone formation in relation to the shape modifications of the tank’s bottom and the height, at which the tank’s inlet was placed, in comparison to the traditional solution. As a part of the research we compared the timings from of sediment cone formation all 6 variants of the experiment. As a result, we determined that introduction of structural elements to the tank’s interior does not have negative impact on the rotational flow of the swirled mixture. As for timing of occurrence of characteristic stages of sediment cone formation – in comparison to with the classic construction - no noticeable deviations of the obtained values were observed.The developed solution can, under industrial conditions, to facilitate the flow of wort and better drainage sediment cone