Upper limits on hydrogen halides in Jupiter from Cassini/CIRS observations

We have determined the following upper limits for the mole fraction of hydrogen halides in Jupiter's atmosphere from Cassini/CIRS observations: [HF]<2.7×10−11, [HCl]<2.3×10−9, [HBr]<1.0×10−9, [HI]<7.6×10−9. These limits are smaller than solar composition for HF and HCl, and support the halogens' condensation in ammonium salts predicted by thermochemical models for the upper jovian troposphere.     

Origin of the Tongbai-Dabie-Sulu Neoproterozoic low-δ 18O igneous province, east-central China

Zircons from 71 diverse rocks from the Qinling-Tongbai-Dabie-Sulu orogenic belt in east-central China and, for comparison, eight from adjoining areas in the South China and North China blocks, have been analyzed for in situ ¹⁸O/¹⁶O ratio and/or U–Pb age to further constrain the spatial distribution and genesis of Neoproterozoic low-δ ¹⁸O magmas, that is, δ ¹⁸O(zircon) ≤4 ‰ VSMOW. In many metaigneous rock samples from Tongbai-Dabie-Sulu, including high-pressure and ultrahigh-pressure eclogites and associated granitic orthogneisses, average δ ¹⁸O values for Neoproterozoic “igneous” zircon cores (i.e., 800–600 Ma) vary from ?0.9 to 6.9 ‰, and from ?9.9 to 6.8 ‰ for Triassic metamorphic rims (i.e., 245–200 Ma). The former extend to values lower than zircons in primitive magmas from the Earth’s mantle (ca. 5–6 ‰). The average Δ ¹⁸O (metamorphic zircon ? “igneous” zircon) values vary from ?11.6 to 0.9 ‰. The large volume of Neoproterozoic low-δ ¹⁸O igneous protoliths at Tongbai-Dabie-Sulu is matched only by the felsic volcanic rocks of the Snake River Plain hotspot track, which terminates at the Yellowstone Plateau. Hence, the low-δ ¹⁸O values at Tongbai-Dabie-Sulu are proposed to result from shallow subcaldera processes by comparison with Yellowstone, where repeated caldera-forming magmatism and hydrothermal alteration created similar low-δ ¹⁸O magmas. However, the possibility of involvement of meltwaters from local continental glaciations, rather than global Neoproterozoic glaciations, cannot be precluded. Our data indicate that Neoproterozoic low-δ ¹⁸O magmas that are either subduction- or rift-related are present locally along the western margin of the South China Block (e.g., Baoxing Complex). It appears that Neoproterozoic ¹⁸O-depletion events in the South China Block as the result of hydrothermal alteration and magmatism affected a much larger area than was previously recognized.     

A comparative study of the thermal behaviour of length-fast chalcedony, length-slow chalcedony (quartzine) and moganite

The thermal behaviour of silica rocks upon heat treatment is dependent on the constituent minerals and petrographic texture types. These constituents can be shown to be mainly quartz in the form of two types of chalcedony (Length-fast (LF) chalcedony and Length-slow (LS) chalcedony, the latter also being termed quartzine) and moganite. Even though the thermal behaviour of LF-chalcedony is well understood, major uncertainties persist concerning the high-temperature behaviour of LS-chalcedony and moganite. We present here a comparative study of these three constituents of common silica rocks. Our results show that the chemical reaction is the same in all three, Si–OH + HO–Si → Si–O–Si + H₂O, but that the reaction kinetics and activation temperatures are very different. LS-chalcedony begins to react from 200 °C upwards, that is at temperatures 50 °C below the ones observed in LF-chalcedony, and shows the fastest reaction kinetics of this ‘water’ loss. Chemically bound water (SiOH) in moganite is more stable at high temperatures and no specific activation temperature is necessary for triggering the temperature-induced ‘water’ loss. Moganite is also found to act as a stabilizer in silica rocks preventing them from temperature-induced fracturing. These findings have implications for the study of potential heat treatment temperatures of silica rocks (in industry and heritage studies), but they also shed light on the different structures of SiO₂ minerals and the role of OH impurities therein.     

South Australian farmers’ markets: tools for enhancing the multifunctionality of Australian agriculture

This paper critically examines the role of farmers’ markets in Australian agriculture. A case study is undertaken in South Australia, where all stallholders at three farmers’ markets situated in Adelaide, Willunga and Berri were surveyed regarding their production and marketing techniques. Overall responses supported literature highlighting the importance of farmers’ markets to the producers who chose to exploit this marketing niche. A strong co-reliance on ‘wholesale sales’ was also recognised, suggesting an important integration of productivist and post-productivist approaches to agricultural development. Of most promise for long-term agricultural sustainability was evidence that certain groups of farmers were found to be realising the potential of these and other alternative markets, in terms of their risk reducing capacity, and diversifying to include various conservation values into their agricultural enterprises. These groups were less concerned about market fluctuations and more concerned with issues of social equity, environmental health and having fun, which meant they unwittingly epitomised the goals of political ecology, by challenging the dominant agricultural methods of production and marketing. It seems these groups also recognised that the direct nature of their transactions would sow beneficial social, environmental and economic ‘seeds’ for change. Finally, it is argued that policies to improve access to farmers’ markets and reduce the cost of participation would assist small scale Australian agricultural producers to evolve smoothly into a multifunctional era.     

Late quaternary chronology of the riverine plain of southeastern Australia

Studies of the Murray River have revealed that its ancestral river system is the result of three separate phases of river activity, each consisting of a degradational and aggradational sub‐phase. To illustrate the relations, certain sections of the rivers were mapped in detail revealing characteristic terrace levels for the various phases. The regional pattern shows that immediately upstream from the Cadell Fault, and for a distance of 100 miles (160 km.) downstream, tectonically induced topographical changes have separated the individual ancestral rivers representative of each phase. Elsewhere, the three rivers are superimposed and follow the same general course. This pattern of separation by diversion also applies to the present rivers so that, in the diverted sector of the river system, old floodplains occur which were deserted by the present river. Initial water logging and salting problems were restricted to these deserted floodplains where they occur in the Irrigation Districts. A relative chronology of Quaternary events has been drawn up.     

Dark Carbon Fixation in the Columbia River’s Estuarine Turbidity Maxima: Molecular Characterization of Red-Type cbbL Genes and Measurement of DIC Uptake Rates in Response to Added Electron Donors

Dark CO₂ fixation has been shown to rival the importance of oxygenic photosynthesis in the global carbon cycle, especially in stratified environments, such as salt wedge estuaries. We investigated this process in the Columbia River estuary using a variety of techniques including functional gene cloning of cbbL (the large subunit of form I RuBisCO), quantitative real-time PCR (qPCR) estimations of cbbL abundance, and analyses of stimulated ¹⁴C-bicarbonate assimilation. A diversity of red-type cbbL genes were retrieved from clone libraries, with 28 unique operational taxonomic units determined from 60 sequences. The majority of the sequences formed two clusters that were distinct from the major clusters typically found in soil environments, revealing the presence of a unique community of autotrophic or facultatively autotrophic/mixotrophic microorganisms in the Columbia River estuary. qPCR estimates indicated that roughly 0.03–0.15 % of the microbial population harbored the cbbL gene, with greater numbers of total bacteria and cbbL gene copies found in the estuarine turbidity maxima (ETM) compared to non-ETM events. In vitro incubations with radiolabeled bicarbonate indicated maximum stimulation by thiosulfate and also suggested that a diversity of other potential electron donors may stimulate CO₂ fixation, including nitrite, ammonium, and Mn(II). Taken together, these results highlight the diversity of the microbial metabolic strategies employed and emphasize the importance of dark CO₂ fixation in the dynamic waters of the Columbia River estuary despite the abundance of organic material.     

Anthropogenic impacts on reduced inorganic sulfur and heavy metals in coastal surface sediments, north Yellow Sea

This study investigated the organic carbon, reduced inorganic sulfur, and heavy metal distribution in superficial sediments at an estuary, a wastewater discharge area, and a mariculture area, as compared with an unpolluted distal site, in the north Yellow Sea, China. Sediment grain size, acid volatile sulfur (AVS), chromium (II)-reducible sulfur, elemental sulfur, total sulfur, total organic carbon (TOC), total nitrogen and trace metal content were determined for each site. These results indicate that pollution leads to increased TOC at all affected sites, which in turn leads to elevated AVS. The resultant change in diagenetic environment leads to changes in the mineralogical fate of Mn. Pb, Zn, Cu, and Cd: all are present at elevated concentrations, and with more metal in the non-residual fractions. Cd shows by far the most elevated concentrations and most significant increase in non-residual fractions and consequently poses the most significant pollution risk.     

Teleconnections and predictive characteristics of Australian seasonal rainfall

A new methodology is proposed that allows patterns of interannual covariability, or teleconnections, between the intraseasonal and slow components of seasonal mean Australian rainfall and the corresponding components in the Southern Hemisphere atmospheric circulation to be estimated. In all seasons, the dominant rainfall–circulation teleconnections in the intraseasonal component are shown to have the characteristic features associated with well-known intraseasonal dynamical and statistical atmospheric modes and their relationship with rainfall. Thus, for example, there are patterns of interannual covariability that reflect rainfall relationships with the intraseasonal Southern Annular Mode, the Madden-Julian Oscillation and wavenumber 3 and 4 intraseasonal modes of variability. The predictive characteristics of the atmospheric circulation–rainfall relationship are shown to reside with the slow components. In all seasons, we find rainfall–circulation teleconnections in the slow components related to the El Niño-Southern Oscillation. Each season also has a coupled mode, with a statistically significant trend in the time series of the atmospheric component that appears to be related to recent observed trends in rainfall. The slow Southern Annular Mode also features in association with southern Australian rainfall, especially during austral winter and spring. There is also evidence of an influence of Indian Ocean sea surface temperature variability on rainfall in southeast Australia during austral winter and spring.     

A new index for variations in the position of the South Pacific convergence zone 1910/11–2011/2012

Quality controlled and recently homogenised mean sea level pressure records for the South Pacific are used to specify the location and variability of the South Pacific convergence zone (SPCZ) during the austral warm season (November–April). The SPCZ is the world’s largest rainfall band during the austral summer, when it dominates the climate of the South Pacific. A new index called the South Pacific convergence zone index (SPCZI) is derived, and is shown to be coherent with changes in low level wind convergence associated with the SPCZ. This index replaces the earlier SPCZ position index because it uses higher quality mean sea level pressure data than the superseded index and extends the time series further forward in time. The SPCZI allows interannual to decadal variability in the climate of the South Pacific to be tracked for more than a century from 1910/1911 to 2011/2012. During El Niño episodes the SPCZ is displaced by about 1°–3° east, and La Niña events 1°–3° west of the mean position on average. The index indicates a striking movement eastward for the period 1977/78–1998/99, compared with 1944/45–1976/77 in association with the Interdecadal Pacific oscillation (IPO). The eastward movement of the SPCZ in the late twentieth century is related to significant precipitation trends in the South Pacific region. Since 1998/99 the SPCZ has regressed westward with the negative phase change of the IPO. The long-term trend in the SPCZI is very small relative to the interannual to decadal variability and is not statistically significant, suggesting that there has been little overall change in the mean position of the SPCZ over the past century.     

Salinity changes in the World Ocean since 1950 in relation to changing surface freshwater fluxes

Global hydrographic and air–sea freshwater flux datasets are used to investigate ocean salinity changes over 1950–2010 in relation to surface freshwater flux. On multi-decadal timescales, surface salinity increases (decreases) in evaporation (precipitation) dominated regions, the Atlantic–Pacific salinity contrast increases, and the upper thermocline salinity maximum increases while the salinity minimum of intermediate waters decreases. Potential trends in E–P are examined for 1950–2010 (using two reanalyses) and 1979–2010 (using four reanalyses and two blended products). Large differences in the 1950–2010 E–P trend patterns are evident in several regions, particularly the North Atlantic. For 1979–2010 some coherency in the spatial change patterns is evident but there is still a large spread in trend magnitude and sign between the six E–P products. However, a robust pattern of increased E–P in the southern hemisphere subtropical gyres is seen in all products. There is also some evidence in the tropical Pacific for a link between the spatial change patterns of salinity and E–P associated with ENSO. The water cycle amplification rate over specific regions is subsequently inferred from the observed 3-D salinity change field using a salt conservation equation in variable isopycnal volumes, implicitly accounting for the migration of isopycnal surfaces. Inferred global changes of E–P over 1950–2010 amount to an increase of 1 ± 0.6 % in net evaporation across the subtropics and an increase of 4.2 ± 2 % in net precipitation across subpolar latitudes. Amplification rates are approximately doubled over 1979–2010, consistent with accelerated broad-scale warming but also coincident with much improved salinity sampling over the latter period.