Coupling an equation of state and Henry's Law to model the phase equilibria of gases and brines: Examples in the N2–H2O–NaCl system

We propose a thermodynamic model for the mixing of gases in aqueous sodium chloride solutions valid to high pressures, high temperatures, and high ionic strength solutions. Our model couples Henry's Law with any equation of state to reproduce experimental data in the aqueous-rich liquid and gas-rich vapor region. In our model, the chemical potential of the solute in the brine is related to the chemical potential of the solute in pure water through salting-out coefficients. The model reproduces all crucial phenomena of binary (gas–water) and pseudo-binary (gas–water–salt) vapor–liquid mixtures below their critical point. We applied the model to reproduce the phase behavior of nitrogen in water and NaCl brines. Results and discussions are shown.     

Not all those who Wander are lost: exploring human mobility using a smartphone application

Since the 1970s, activity diaries have been the principal source of data used by geographers and urban planners to capture human mobility patterns; however, memory recall requirements and participant burden are limiting features of this approach. While handheld GPS devices were initially used to simply validate activity diaries, the ubiquity of smartphones makes GPS-based technology a viable alternative for collecting human mobility data. This research visualises human mobility patterns using spatiotemporally GPS-rich traces collected from 24 participants during a pilot study of a new smartphone application—Wander. The results illustrate the utility of such data for capturing individuals’ multi-nodal activity spaces to better understand people–place interactions in the context of increasingly fluid and mobile lifestyles. Finally, we draw on our experiences of implementing this pilot study to discuss the benefits and limitations of this technology for its broader application in domains such as transportation planning, tourism management, and in the management of crime and disorder.     

Stand structure,floristic composition and species diversity along altitudinal gradients of a Bornean mountain range 30 years after selective logging

The mountain ecosystem is a hotspot of biodiversity and provides a significant contribution to the humans' livelihoods. However, there is still a lack of information regarding floral diversity and how it has been affected due to a logging operation in Sarawak. A study was conducted to determine vegetation recovery at the Heart of Borneo conservation area at different elevations: 750–1200 m(S1), 1200–1500 m(S2) and 1500 m(S3). A total of 891 trees were enumerated. The trees comprised 55 families, 98 genera and 203 species. The lowest elevation site, S1, contained the highest number of species(117) and families(42), while the highest elevation site, S3, contained the lowest diversity(25 families and 59 species). A similar forest structure was recorded, whereby diameter at breast height(dbh), basal area and height decreased as elevation increased. The most speciose families in S1 were Dipterocarpaceae(11 species) and Lauraceae(10 species), while Lauraceae and Fagaceae were the dominant tree families at S2 and S3. Secondary tree species are still abundantly found in the logged plots, especially at S2(45.5%), indicating that after 30 years, these stands are still in the recovery stages. The logged plots retained typical secondary forest appearances with lower canopy diameters and heights and dbh than the unlogged forest. Although the species richness approached that of the unlogged plots, especially at S1(90.9%) and S3(94.9%), there were still major differences in the floristic compositions between logged and unlogged plots(35.4%, 21.5% and 44.7% for S1, S2 and S3, respectively). Although potential seed sources were in close proximity, succession at S2 has proceeded much slower than at S1 and S3. Lower concentrations of soil nutrients, especially N, may be the main reason for the slow recovery. In conclusion, the results suggested that the selectively logged forest at the Payeh Maga Highland required more than three decades to recover and achieve a climate forest stage.     

A model for partitioning gases among brines and hydrocarbons in oil reservoirs: Examples from the IEA-GHG Weyburn CO2 Monitoring and Storage Project, Saskatchewan, Canada

We derive a thermodynamic model useful for calculating the partitioning of gases in brine–oil closed systems. We assumed real binary mixtures of all components, and solved a set of equilibrium equations relating the solubility of gases in brines to the solubility of gases in petroleum liquids. We applied the model to understand the distribution of gases in the IEA-GHG Weyburn CO₂ Monitoring and Storage Project, in Saskatchewan, Canada, throughout the first and second year after commencement of CO₂ injection. Results indicate that a free-gas phase formed in the south-east of the field 363 days after injection, which increased in size and volume with time, but did not correlate with zones showing excess CO₂ production. We also observed overlaps between areas of ¹³C depleted HCO₃⁻ and areas with free-vapor phase. We conclude that gas injection leads to short-term CO₂ dissolution in liquids, followed by the creation of a CO₂-rich vapor phase.     

The Potassium‐Argon Laser Experiment (KArLE): In Situ Geochronology for Planetary Robotic Missions

Geochronology is a fundamental measurement for planetary samples, providing global and solar system context for the conditions prevailing on the planet at the time of major geological events. The potassium (K)‐Argon (Ar) laser experiment (KArLE) will make in situ noble gas geochronology measurements aboard planetary robotic missions such as rovers and landers. Laser‐induced breakdown spectroscopy (LIBS) is used to measure the K abundance in a sample and to release its noble gases; the evolved Ar is measured by mass spectrometry, and relative K content is related to absolute Ar abundance by sample mass, determined by optical measurement of the ablated volume. This approach allows K and Ar to be measured on identical volumes multiple times to create an isochron, which improves the age determination and reveals irregularities in the rock if they exist. The KArLE technique measures a whole‐rock K‐Ar age with 10% uncertainty or better for rocks 2 Ga or older, sufficient to resolve the absolute age of many planetary samples. The LIBS–mass spectrometry approach is attractive because the analytical components have been flight‐proven, do not require further technical development and provide essential measurements (complete elemental abundance, evolved volatile analysis, micro‐imaging) as well as in situ geochronology.     

Tornado folk science in Alabama and Mississippi in the 27 April 2011 tornado outbreak

In this paper, we collect, categorize, and discuss the existence of numerous ways of knowing about tornado threat that largely differ from the perspective taken by the meteorological community. These alternate ways of knowing became apparent during interviews with survivors of the 27 April 2011 tornado outbreak in the US southeast, particularly in Alabama and Mississippi. Phenomena discussed herein include perceptions of safety near waterways, vulnerability near a specific highway with a recently modified landscape, the protective nature of hills, relative optimism about home sites, and local observational weather knowledge. Theoretical explanations offered for these observed phenomena include ideas from risk perception and place attachment literatures.     

Young Asteroid 832 Karin shows no rotational spectral variations

We have made near-IR spectral observations of the very young (5.75 Myr) S-type asteroid 832 Karin, well sampled in rotational phase over its 18.35-h period. We find no significant variations in its reflectance spectrum. Karin, the brightest member of the Karin cluster (a sub-family of the larger, older Koronis dynamical family), was shown to be exceptionally young by Nesvorný et al. [Nesvorný, D., Bottke, W.F., Dones, L., Levison, H., 2002. Nature 417, 720-722], using backward numerical integration of orbital elements of cluster members. Their precise dating of the collisional breakup gives us an opportunity, for the first time and without age-dating of physical samples, to monitor time-evolution of processes, like space weathering, that operate on timescales of ∼1-10 Myr. Sasaki et al. [Sasaki, T., Sasaki, S., Watanabe, J., Sekiguchi, T., Yoshida, F., Kawakita, H., Fuse, T., Takato, N., Dermawan, B., Ito, T., 2004. Astrophys. J. 615, L161-L164; Sasaki, T., Sasaki, S., Watanabe, J., Sekiguchi, T., Yoshida, F., Ito., T., Kawakita, H., Fuse, T., Takato, N., Dermawan, B., 2005. Lunar Planet. Sci. XXXVI. Abstract #1590] had made similar measurements of Karin, although more sparsely sampled than ours, and claimed dramatically different colors as a function of rotational phase. Sasaki et al. interpreted their data to be showing the reddish, space-weathered exterior surface of the precursor asteroid, as well as an interior face, which had not had time to become space-weathered. On five nights over 2006 January 7-14 UT, we observed Karin with the SpeX (0.8-2.5 μm) spectrometer of the IRTF. We analyze data in 30° intervals of rotational longitude, some of which we sampled on two different nights. The spectra are consistent with little or no spectral variation as the asteroid rotates; certainly there are no changes as large as previously reported. The previous observations were probably spurious. Our average spectrum resembles the “blue” spectrum of Sasaki et al., which they interpreted to be the “fresh” surface. Karin is not quite as red as typical S-types, yet has rather shallow absorption bands. We surmise that the space-weathering process affecting Karin has had time to reduce spectral contrast, but has not operated long enough to redden its spectrum—an intermediate case of space weathering, which has gone to completion for most main-belt asteroids. This work sets an important constraint on the timescale for the ubiquitous space-weathering process affecting S-types, namely that its effects are evident, but not yet complete, at ∼6 Myr.     

Influences of organic matter and calcification rate on trace elements in aragonitic estuarine bivalve shells

A suite of elements (B, Na, Mg, S, K, Ca, V, Mn, Cr, Sr, and Ba) was measured in aragonitic shells of the estuarine bivalve Corbula amurensis, the Asian clam, using the Sensitive High-Resolution Ion MicroProbe with Reverse Geometry (SHRIMP RG). Our initial intent was to explore potential geochemical proxy relationships between shell chemistry and salinity (freshwater inflow) in northern San Francisco Bay (SFB). In the course of this study we observed variations in shell trace element to calcium ([M]/Ca) ratios that could only be attributed to internal biological processes. This paper discusses the nature and sources of internal trace element variability in C. amurensis shells related to the shell organic fraction and shell calcification rates. The average organic content of whole C. amurensis shells is 19%. After treating whole powdered shells with an oxidative cleaning procedure to remove organic matter, shells contained on average 33% less total Mg and 78% less total Mn. Within our analytical uncertainty, Sr and Ba contents were unchanged by the removal of organic matter. These results show that aragonitic C. amurensis shells have a large component of non-lattice-bound Mg and Mn that probably contribute to the dissimilarity of [M]/Ca profiles among five same-sized shells. Non-lattice-bound trace elements could complicate the development and application of geochemical proxy relationships in bivalve shells. Because B, Ba and Sr occur exclusively in shell aragonite, they are good candidates for external proxy relationships. [M]/Ca ratios were significantly different in prismatic and nacreous aragonite and in two valves of the same shell that had different crystal growth rates. Some part of these differences can be attributed to non-lattice-bound trace elements associated with the organic fraction. The differences in [M]/Ca ratios were also consistent with the calcification rate-dependent ion transport model developed by Carré et al. [Carré M., Bentaleb I., Bruguier O., Ordinola E., Barrett N. T. and Fontugne M. (2006) Calcification rate influence on trace element concentrations in aragonitic bivalve shells: evidences and mechanisms. Geochim. Cosmochim. Acta70, 4906-4920] which predicts that [M]/Ca ratios increase as calcification rates increase and Ca²⁺ channel specificity decreases. This result, in combination with the possibility that there were ontogenetic variations in growth rates among individuals younger than 2 years, underscores the need to develop an independent age model for C. amurensis shells. If growth-rate effects on lattice-bound [M]/Ca ratios can be constrained, it may yet be possible to develop high-resolution geochemical proxies for external solution chemistry in low-salinity regions of SFB.     

Mg/Ca, Sr/Ca, and stable isotopes in modern and Holocene Protothaca staminea shells from a northern California coastal upwelling region

This study explores the potential of intertidal Protothaca staminea shells as high-resolution geochemical archives of environmental change in a coastal upwelling region. Mg/Ca and Sr/Ca ratios were analyzed by excimer laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) at sub-weekly temporal resolution in shells growing ∼1 mm per month. Growth patterns of a modern P. staminea shell from Humboldt Bay, California, collected in December 1999 made it possible to infer a lifespan from 1993 to 1998. Growth hiatuses in the shell may have excluded records of extreme events. Mg/Ca ratios appeared to be partly controlled by water temperature; the correlation coefficient between temperature and Mg/Ca was r = 0.71 in one of four growth increments. Significant year-to-year differences in the sensitivity of Mg/Ca to temperature in P. staminea could not be explained, however. Sr/Ca ratios appeared to be more closely related to shell growth rate. Oxygen isotopes, measured at 2-week temporal resolution in the same shell, did not show a clear relation to local temperature in summer, possibly because temperatures were higher and less variable at the King Salmon mudflat, where the shell was collected, than in the main channel of Humboldt Bay, where water properties were monitored. Negative shell δ¹³C values (<−0.5‰) marked spring and summer coastal upwelling events.The Mg contents of P. staminea midden shells dated to ∼3 ka and ∼9 ka were significantly lower than in the modern shell. This may have resulted from degradation of a Mg-rich shell organic matrix and precluded quantitative interpretation of the older high-resolution records. Elevated δ¹³C values in the ∼3 ka shell suggested that the individual grew in highly productive or stratified environment, such as a shallow coastal embayment or lagoon.     

Seasonal dynamics and exports of elements from a first‐order stream to a large inland lake in Michigan

Headwater streams are critical components of drainage systems, directly connecting terrestrial and downstream aquatic ecosystems. The amount of water in a stream can alter hydrologic connectivity between the stream and surrounding landscape and is ultimately an important driver of what constituents headwater streams transport. There is a shortage of studies that explore concentration–discharge (C‐Q) relationships in headwater systems, especially forested watersheds, where the hydrological and ecological processes that control the processing and export of solutes can be directly investigated. We sought to identify the temporal dynamics and spatial patterns of stream chemistry at three points along a forested headwater stream in Northern Michigan and utilize C‐Q relationships to explore transport dynamics and potential sources of solutes in the stream. Along the stream, surface flow was seasonal in the main stem, and perennial flow was spatially discontinuous for all but the lowest reaches. Spring snowmelt was the dominant hydrological event in the year with peak flows an order of magnitude larger at the mouth and upper reaches than annual mean discharge. All three C‐Q shapes (positive, negative, and flat) were observed at all locations along the stream, with a higher proportion of the analytes showing significant relationships at the mouth than at the mid or upper flumes. At the mouth, positive (flushing) C‐Q shapes were observed for dissolved organic carbon and total suspended solids, whereas negative (dilution) C‐Q shapes were observed for most cations (Na⁺, Mg²⁺, Ca²⁺) and biologically cycled anions (NO₃^?, PO₄^3?, SO₄^2?). Most analytes displayed significant C‐Q relationships at the mouth, indicating that discharge is a significant driving factor controlling stream chemistry. However, the importance of discharge appeared to decrease moving upstream to the headwaters where more localized or temporally dynamic factors may become more important controls on stream solute patterns.