A thermochemical study of vaterite

Vaterite is shown to be unstable with respect to calcite at 25°C by measurements of the enthalpies of solution in 0·1 N HCl under 0·97 atm CO₂ and the solubilities in water under 0·97 atm CO₂ of the two polymorphs. For a pure, synthetic vaterite ΔH (tr) = ?1036 ±16 cal mol^?1 and ΔG(tr) = ?790 ± 25 cal mol^?1 for the transition to calcite. For other vaterites aged longer during preparation ΔH(tr) is smaller and shows a linear relationship with the X-ray line broadening which extrapolates to ΔH(tr) = ?545 ± 30 cal mo^?1 for zero broadening. The use of X-ray line broadening as a measure of crystal imperfection and stability is discussed for various synthetic and natural vaterites.     

Ammonium Ion, Humic Materials, and Trihalomethane Potential in Northeastern Kansas Ground Waters

Glacial buried-valley aquifers serve as primary sources of potable ground water in northeastern Kansas. A long known problem, however, is that a large percentage of well waters in this region exceed the U.S. Environmental Protection Agency (EPA) limits for nitrate (NO⁻₃). A detailed study of the hydrogeology and water quality of the buried valleys has confirmed the nitrate problem and led to a recognition that some well waters with low ( 5 mg/l) NO⁻₃ concentrations have anomalous ( 0.5 mg/l) ammonium ion (NH⁺₄) levels, with an NH⁺₄ range from <0.1 to 4.8 mg/l. The extractable NH⁺₄ concentrations in related glacial sediments range up to approximately 75 mg/kg, and the amounts generally increase from an average of 2 mg/kg in the topsoil downward to bedrock. Migration of brines from subjacent Permian or Pennsylvanian bedrock into the unconsolidated sediments locally may cause desorption of NH⁺₄ and an increase in its levels in the associated ground waters. Numerous test holes drilled in the study area showed a black scum on the fluid and cuttings, which may be from buried humic materials. Recently measured total organic carbon (TOC) contents of the ground waters confirm a significant level in some areas, with a range from 0.1 to 2.4 mg/l as C. Chlorination of water with dissolved organics may lead to production of halogenated compounds. Two public-water-supply well waters contained total trihalomethane (TTHM) levels close to the maximum contaminant level (MCL) of 100 /μg/l in chlorinated samples quenched after one week. The presence of NH⁺₄ inhibits the formation of THMs, but it also can give rise to odor and taste problems in the finished water. The inhibition of THM formation by NH⁺₄ is achieved by reactions which compete with the organics for combination with chlorine. These reactions make maintaining appropriate chlorine residuals difficult and also may lead to production of undesirable side products. Present efforts to evaluate the regional water-quality problems are focused in Nemaha County, Kansas.     

Layered ultramafic-gabbro bodies in the Lewisian of northwest Scotland: geochemistry and petrogenesis

Layered ultramafic-gabbro bodies occur widely in the Archaean of northwest Scotland. They were metamorphosed at granulite or high amphibolite facies and were tectonically thinned and broken up during deformation. They comprise repeated ultramafic-gabbro layers, locally with Ni-poor sulphide-rich tops, each rhythmic unit showing decreasing MgO, Ni and normative anorthite with stratigraphic height. Major, trace and rare earth element data are presented for the range of rock types. In ultramafic rocks, MgO varies from 22 to 37 wt.%, Ni from 1000 to 2500 ppm and TiO₂ from 0.08 to 0.40 wt.%, while the MgO content of the gabbros ranges from 14 to 6 wt.%. The REE patterns are flat to LREE enriched with no significant Eu anomalies. In ultramafic rocks REE are from 4 to 10 times chondrite, and in the gabbros LREE range from 8 to 30 times chondrite and HREE from 6 to 15 times chondrite. Study of incompatible elements (Ti, Zr, Y) which are relatively immobile during metamorphism shows that neither garnet nor hornblende were involved in fractionation. Trace element modelling shows it is improbable that the ultramafic rocks represent primary MgO-rich liquids even though their incompatible element contents are quite high. The chemical trends are interpreted in terms of olivine and pyroxene settling from a tholeiitic high-Mg magma with 15–20 wt.% MgO derived by 30–40% partial melting of an undepleted mantle. The ultramafic rocks are the cumulates and the gabbros the derived liquids.     

The role of horizontal resolution in simulating drivers of the global hydrological cycle

The role of atmospheric general circulation model (AGCM) horizontal resolution in representing the global energy budget and hydrological cycle is assessed, with the aim of improving the understanding of model uncertainties in simulating the hydrological cycle. We use two AGCMs from the UK Met Office Hadley Centre: HadGEM1-A at resolutions ranging from 270 to 60 km, and HadGEM3-A ranging from 135 to 25 km. The models exhibit a stable hydrological cycle, although too intense compared to reanalyses and observations. This over-intensity is explained by excess surface shortwave radiation, a common error in general circulation models (GCMs). This result is insensitive to resolution. However, as resolution is increased, precipitation decreases over the ocean and increases over the land. This is associated with an increase in atmospheric moisture transport from ocean to land, which changes the partitioning of moisture fluxes that contribute to precipitation over land from less local to more non-local moisture sources. The results start to converge at 60-km resolution, which underlines the excessive reliance of the mean hydrological cycle on physical parametrization (local unresolved processes) versus model dynamics (large-scale resolved processes) in coarser HadGEM1 and HadGEM3 GCMs. This finding may be valid for other GCMs, showing the necessity to analyze other chains of GCMs that may become available in the future with such a range of horizontal resolutions. Our finding supports the hypothesis that heterogeneity in model parametrization is one of the underlying causes of model disagreement in the Coupled Model Intercomparison Project (CMIP) exercises.     

The scramble for the Waste Lands: Tracking colonial legacies,counterinsurgency and international investment through the lens of land laws in Burma/Myanmar

This article traces the revenue category and legal concept of the Waste Land in Burma/Myanmar from its original application by the British colonial apparatus in the nineteenth century, to its later use in tandem with Burma Army counterinsurgent tactics starting in the 1960s, and finally to the 2012 land laws and current issues in international investment. This adaptation of colonial ideas about territorialization in the context of an ongoing civil war offers a new angle for understanding the relationship between military tactics and the political economy of conflict and counterinsurgent strategies which crucially depended on giving local militias—both government and nongovernment—high degrees of autonomy. The recent government changes, including the more civilian representation in parliament and its shift to engage with Western economies, raise questions regarding the future of the military, as well as local autonomy and the rural peasantry's access to land. As increasing numbers of international investors are poised to enter the Myanmar market, this article will revisit notions of land use and appropriation, and finally the role of the army and its changing relationship with Waste Lands.     

Long-term changes in polychaete assemblages of Botany Bay (NSW, Australia) following a dredging event

The long-term effects of marine aggregate dredging on near-shore benthic assemblages are still largely unknown, despite a global increase in demand for, and extraction of, marine aggregates. This study assessed the state of recovery of polychaete assemblages in Botany Bay, temperate NSW, Australia, at sites dredged for aggregate material more than 10 years previously. Sedimentary and faunal samples were collected from impact sites in Botany Bay, and from reference sites in nearby Pittwater estuary. This study was based on, and included data from, a study conducted by the Australian Museum at the same sites in the 2 years following cessation of dredging. Abundance, species richness and evenness of polychaetes, as well as overall polychaete assemblage structure, were compared between localities over time.