Phase transition in K2Cd2(SO4)3: Order parameter and microscopic distortions

The transition from P2₁3(T ⁴) to P2₁2₁2₁(D ₂ ⁴ ) in the langbeinite K₂Cd₂(SO₄)₃ has been analyzed using group theoretical methods and previously published structural data above and below the transition. We find that because the transition is strongly first-order, the primary-order parameter has relatively large values at the transition temperature, and higher order terms which involve the order parameter, the strain, and the coupling of the two must be included in the Landau expansion for the free energy. Complex displacements occur at the transition for all atoms of the unit cell, but these displacements can be resolved into contributions which can be shown from symmetry considerations to transform as the _{2 3} irrep of P2 ₁ 3(T ⁴) as well as contributions from symmetry-preserving displacements which transform under the irrep ₁. Therefore, the transition is not a simple one and involves sulfate rotations and cadmium and potassium ion displacements.     

Comparative study of sampling methods and in situ and laboratory analysis for shallow-water submarine hydrothermal systems

A primary aim for sampling of submarine hydrothermal vents is to minimize inclusion of ambient seawater. Here, we compare the results of three different sampling methods (air displacement, two-valve bottle, and syringes) for shallow submarine systems. Mixing of hydrothermal fluid with seawater is unavoidable; however, calculations based on linear mixing models allow estimation of the hydrothermal fluid end-member composition. The results show that sampling with a two-valve bottle and syringes are the best options because they allow collection of samples with a large proportion of hydrothermal fluid. Additionally, we compare the results of in situ and laboratory analyses of the fluid samples, and demonstrate that determination of chemical composition in situ is the best option for some components, as re-equilibration affects some component concentrations (i.e. bicarbonate). Conversely, silica determination in situ usually underestimates the concentration in the fluid, as it does not account for polymeric silica. Other components can be measured either in the field or in the laboratory.     

MinIdent: An application to the identification and classification of amphiboles

Summary Amphibole data in the MinIdent database (Smith andLeibovitz, 1986) were initially entered using species names quoted in the original source. The database has been updated by reclassifying these early data using the program AMPHTAB supplied by N. M. S. Rock and by adding supplemental data from the more recent literature, with the species names again checked using AMPHTAB. Associated MinIdent mineral identification software was utilized to determine which minerals in the database most closely resemble a series of unknown specimens chemically, as expressed in the Chemical Matching Index, CM, a relative figure-of-merit. Chemical data fromMogessie and Tessadri (1982) and Hawthorne (1983) were used to check the agreement between MinIdent and AMPHTAB for the classification of 221 unknown amphiboles.With 450 amphibole analyses entered and compiled in MinIdent, the name assigned by AMPHTAB showed the highest value of CM in MinIdent for 127 of the 221 unknown amphiboles (57.5°/x) and the second highest value for another 32 (14.5%). A chemically adjacent amphibole field had the highest value of CM for 59 of the 221 unknowns (26.7%), where chemically adjacent refers to a change in one chemical parameter. The greatest discrepancy between the two programs occurred in the hornblendes, with an agreement of just 20%, although for 58% of the unknowns the species with the highest CM in MinIdent was in a chemical field adjacent to the species name assigned by AMPHTAB. In many cases the disagreement between MinIdent and AMPHTAB could be ascribed to a lack of data in MinIdent.A comparison of the two programs suggests that the assignment of a single name to an unknown amphibole by AMPHTAB with no direct indication of its reliability may be; misleading. Standard analytical errors are frequently sufficient to overlap the arbitrary boundaries between amphibole species fields. In such cases it may be preferable to use a program such as MinIdent which, rather than assigning an arbitrary amphibole name, presents a list of 20 amphiboles with the degree of similarity between them and the unknown amphibole indicated. MinIdent offers the additional benefit of allowing input of other than chemical data and bases the match between unknown and standard data upon all input data. This will become more of an advantage as instruments such as automated refractometers become available for routine use.

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Zusammenfassung Ausgangspunkt war das Amphibol-Datenmaterial (Smith und Leibovitz, 1986) mit den dort verwendeten Artnamen. Diese Basisdaten wurden vervollständigt und erneuert durch Reklassifizierung mittels des AMPHTAB Programms, ergänzt durch N. M. S. Rock, und durch Hinzufügung weiterer Daten aus der neuesten Literatur, deren Speciesnamen wiederum mit AMPHTAB überprüft wurden. Außerdem wurde eine MinIdent Mineralidentifizierungs-Software verwendet, um die Minerale zu bestimmen, die in ihrem Chemismus am ehesten einer Serie von unbekannten Amphibol-Species entsprechen, wie sie im Chemical Matching Index (CM) aufscheinen. Zur Klassifikation von 221 unbekannten Amphibolen wurden chemische Daten von Mogessie und Tessadri (1982) verwendet um die Übereinstimmung zwischen MinIdent und AMPHTAB zu überprüfen.Unter den 450 in MinIdent zusammengestellten und eingegebenen Amphibolanalysen zeigen die bei AMPHTAB angegebenen die höchsten CM Werte, nämlich 127 von 221 unbekannten Amphibolen (57,5%) und weitere 32 (14,5%) die zweithöchsten Werte. Innerhalb eines chemisch benachbarten Amphibolfeldes hatten 59 der 221 unbekannten Amphibole (26,7%) die höchsten CM Werte, wobei unter achemisch benachbart die Änderung eines chemischen Parameters zu verstehen ist. Die größten Unterschiede zwischen den beiden Programmen traten bei den Hornblenden auf. Die Übereinstimmung lag bei nur 20%, obwohl bei 58% der unbekannten Amphibole die Species mit dem höchsten CM Wert in MinIdent in ein chemisches Feld zu liegen kamen, welches zu den bei AMPHTAB angegebenen Speciesnamen eine benachbarte Position einnimmt. Die Unterschiede zwischen MinIdent und AMPHTAB könnten in vielen Fällen auf ein Fehlen von Daten in MinIdent zurükzuführen sein.Ein Vergleich beider Programme deutet an, daß die Angabe eines Einzelnamens für ein unbekanntes Amphibol im AMPHTAB Programm ohne Angaben über die Zuverlässigkeit zu Mißverständnissen führen kann. Normale analytische Fehler können bereits dazu führen, daß die Grenzen zweier willkürlicher Amphibolfelder überlappen. In derartigen Fällen emphiehlt sich die Anwendung des MinIdent Programmes, welches eben nicht einen willkürlichen Amphibolnamen angibt, sondern eine Liste von 20 Amphibolen mit dem Grad ihrer Ähnlichkeit, und einem Hinweis auf den unbekannten Amphibol. MinIdent bietet den zusätzlichen Vorteil, daß man außer chemischen auch andere Daten eingeben kann, und stellt dann sämtliche Daten des unbekannten Amphibols den Standard Daten gegenüber. Dieser Klassifizierungsvorgang wird mit der zunehmenden Routineanwendung von automatischen Refraktometern verstärkte Anwendung finden.

     

Zooplankton dynamics in an intertidal salt-marsh basin

We determined tidal, diel (day-night), and diurnal (day to day) patterns of occurrence for the summer zooplankton assemblage in an intertidal salt marsh basin at North Inlet Estuary, South Carolina. In one time series, 153 μm pump and 365 μm net collections were made every 1–2 h during four consecutive tidal cycles. Taxonomic composition remained unchanged throughout most of the 48-h period, but densities and proportionalities of individual taxa were highly variable. Recurring patterns of abundance were observed and taxon-specific relationships with the tidal and diel cycles were indicated. Zooplankton were not uniformly distributed within flooding-ebbing water masses and distributions could not be explained by simple passive advection with the tides. Diel differences in densities of copepods and bivalves resulted from behavioral responses to changing light conditions. Large pulses of crab and shrimp larvae originating from nocturnal hatching events within the intertidal basin exited but did not return during the next flood tide. Higher densities of postlarval decapods on flood tides indicated settlement and recruitment to the shallow basin. In a second time series, replicated collections of the 153 μm and 365 μm assemblages were made during the daytime ebb tide every 1–3 d from May through October 1991 to determine relationships between diurnal changes in depth, salinity, and temperature and zooplankton composition and abundance. Diurnal variations in densities and proportionalities were less than those observed during the 48-h study and patterns were not regular. For most taxa, relationships between depth and abundance were the same in both time series. During periods of reduced salinity, densities of copepods,Uca zoeae, and barnacle nauplii decreased and densities ofUca megalopae andPenaeus postlarvae increased. However, zoeae emerged and postlarvae recruited throughout the 5-mo period, indicating that considerable flexibility in responses and tolerances existed within the populations. The diversity of life-history strategies and behavioral adaptations found among the zooplankton assures continuous occupation of flooded intertidal habitats. We suspect that the evolution and maintenance of temporally staggered recurring patterns of occurrence results in reductions in the competition for resources.     

Fe, Ni and Co variations in the metals of some antarctic chondrites

Nearly 4,000 Fe, Ni and Co analyses have been carried out on the metal phases of 12 Antarctic chondritic meteorites by means of the electron microprobe. H-group chondrites show relatively simple patterns of variation for these elements but L- and LL-group members show much more scatter in both Ni and Co concentrations. A single member of the CO3 group investigated shows some scatter in the concentrations and also much higher Co concentrations in the high-Ni (awaruite?) phase (1.25–2%) than in the coexisting kamacite (0.2–0.5%). Thus, analysis of the metal phases can provide not only a means of identifying the group to which a meteorite belongs, but also the possibility of distinguishing between individual chondrites from the same group.

The overall concentrations of Co in the metal particles in the different groups are considered to be related inversely to the abundance of metal grains in meteorites of these groups while the scatter is interpreted as reflecting characteristics inherited at the time of accretion. The absence of homogenisation of the concentrations of Fe, Ni and Co in the metal particles, even in so-called equilibrated chondrites, provides further evidence against the widely held notion that these meteorites have been involved in a high-temperature prograde metamorphism.     

Interpreting CO2–SIc relationship to estimate CO2 baseline in limestone aquifers

Saturation index with respect to calcite (SIc) and equilibrium CO₂ partial pressure are important parameters to study groundwater in limestone aquifers. Aside from their use in time series, CO₂ and SIc are used to estimate the baseline of CO₂ in the vadose zone. The objective of this paper is to present conceptual examples on the use of the CO₂–SIc relationship to have new information from usual parameters. Case study was considered as an example of use from Cussac site, a limestone aquifer in southwest of France. The result showed that CO₂ baseline in unsaturated zone is found close to 25,000 ± 1,000 ppm.     

Survivorship of coral juveniles in a fish farm environment

Intensive fish farming is an emerging coastal activity that can potentially enhance sedimentation and promote eutrophication in fringing coral reefs. Here, we investigate the effect of fish farm effluent on the juvenile survivorship of the reef-building coral Seriatopora caliendrum. One-month old juvenile corals (on terracotta tiles) were deployed in fish farm and reference (reef) sites in Bolinao, the Philippines at a depth of 2m. After forty days, no survivor was recovered in the fish farm, while survivorship was low (11%) in the reference site, with the survivors' growth rate at 3.3polypsmo(-1) or 1.3mm(2)mo(-1). The fish farm deployed tiles were covered with muddy sediment and were colonized by barnacles, whereas those in the reference site were overgrown by a short stand of filamentous macroalgae. Environmental monitoring revealed higher nutrient levels (ammonia and phosphate), sedimentation rate, and organic matter flux, as well as diminished water transparency and dissolved oxygen levels in the fish farm compared to the reference site. Hence, intensive fish farming offers a suite of physical, chemical and biological modifications of the coastal marine environment which have a detrimental effect on the survivorship of coral juveniles.     

Large debris flows in Chosica,Lima, Peru: the application of hydraulic infrastructure for erosion control and disaster prevention

Abstract

Large debris flows in steep-sloped ravines debouching to the Rimac River, in metropolitan Lima (Peruvian capital), have resulted in considerable loss of life and property adversely impacting communities in the region. Temporal, spatial and volumetric features of debris flows are difficult to predict, and it is of utmost importance that achievable management solutions are found to reduce the impact of these catastrophic events. The emotional and economic toll of these debris flows on this increasingly densely populated capital city in South America is devastating where communities must live in such inadequate and dangerous conditions. To address this problem, the application of advanced Japanese technology, Sustainable Actions Basin Orientation (SABO), has been investigated using a geomorphological modelling to develop an implementation plan. Rayos de Sol stream basin in Chosica, was selected as a pilot to develop the proposal, as it is considered high risk due to the presence of ancient debris flows and recent flows in 2012, 2015 and 2017. The recurrence of debris flows in this location has resulted in numerous deaths and catastrophic property losses. This study combines geologic and geomorphic mapping and hydraulic and landform evolution numerical modelling. The implementation of a SABO Master Plan based on the multidisciplinary assessment hazard scenarios, will allow the implementation of feasible mitigation actions. The SABO technology has been applied successfully in Japan and other countries in areas with steep short slopes, similar to the conditions surrounding the Peruvian capital. Results from this study will be presented to the Peruvian Government as part of an action plan to manage debris-flow impact.

1. KEY POINTS

2. High-risk mass slope failure is linked to poor urban planning in urban developing regions of Lima the capital of Peru.

3. A multidisciplinary study including geotechnical and hydrological analysis, engineering design, and socio-economic research is required to implement a SABO Master Plan, and this basin is pilot study basin.

4. At the present time, a maintenance programme for existing hydraulic structures should be implemented, and a flood risk management plan developed may propose the relocation of some communities and infrastructure.

     

The Influence of Community Size and Location on Different Dimensions of Vulnerability: a case study of Australian coastal communities

ABSTRACT

Coastal communities are part of the Australian identity but little is known about their characteristics and their long-term prosperity prospects. Increased migration to coastal areas and increased exposure to extreme climatic events indicates a need for social and economic data to inform socio-ecological systems planning. Here, we undertake a geo-spatial analysis to develop a typology of Australian coastal communities and assess relative vulnerability to climate-driven environmental change for a range of social and economic indicators. The aim of this study is to understand how the vulnerability of Australian coastal communities varies with geographic location or community size, and in comparison to other community types. Results show that both the population size and location of a coastal community matter and that coastal communities overall are more vulnerable on some socio-economic dimensions to climate-driven environmental change than their rural equivalents. However, results also demonstrate that the smallest coastal communities are strong in some important aspects of the human, social and financial domains, putting them in a good position to deal with some changes. Scale-appropriate and context-specific social policies are needed to address identified socio-economic vulnerabilities, supported by a range of formal and informal institutional structures, such as strategies to improve education and female workforce participation, and encourage participation in volunteering to increase human and social capital.