A community-wide intercomparison exercise for the determination of dissolved iron in seawater

The first large-scale international intercomparison of analytical methods for the determination of dissolved iron in seawater was carried out between October 2000 and December 2002. The exercise was conducted as a rigorously “blind” comparison of 7 analytical techniques by 24 international laboratories. The comparison was based on a large volume (700 L), filtered surface seawater sample collected from the South Atlantic Ocean (the “IRONAGES” sample), which was acidified, mixed and bottled at sea. Two 1-L sample bottles were sent to each participant. Integrity and blindness were achieved by having the experiment designed and carried out by a small team, and overseen by an independent data manager. Storage, homogeneity and time-series stability experiments conducted over 2.5 years showed that inter-bottle variability of the IRONAGES sample was good (< 7%), although there was a decrease in iron concentration in the bottles over time (0.8–0.5 nM) before a stable value was observed. This raises questions over the suitability of sample acidification and storage.     

Global occurrence of tellurium-rich ferromanganese crusts and a model for the enrichment of tellurium

Hydrogenetic ferromanganese oxyhydroxide crusts (Fe-Mn crusts) precipitate out of cold ambient ocean water onto hard-rock surfaces (seamounts, plateaus, ridges) at water depths of about 400 to 4000 m throughout the ocean basins. The slow-growing (mm/Ma) Fe-Mn crusts concentrate most elements above their mean concentration in the Earth’s crust. Tellurium is enriched more than any other element (up to about 50,000 times) relative to its Earth’s crustal mean of about 1 ppb, compared with 250 times for the next most enriched element.We analyzed the Te contents for a suite of 105 bulk hydrogenetic crusts and 140 individual crust layers from the global ocean. For comparison, we analyzed 10 hydrothermal stratabound Mn-oxide samples collected from a variety of tectonic environments in the Pacific. In the Fe-Mn crust samples, Te varies from 3 to 205 ppm, with mean contents for Pacific and Atlantic samples of about 50 ppm and a mean of 39 ppm for Indian crust samples. Hydrothermal Mn samples have Te contents that range from 0.06 to 1 ppm. Continental margin Fe-Mn crusts have lower Te contents than open-ocean crusts, which is the result of dilution by detrital phases and differences in growth rates of the hydrogenetic phases.Correlation coefficient matrices show that for hydrothermal deposits, Te has positive correlations with elements characteristic of detrital minerals. In contrast, Te in open-ocean Fe-Mn crusts usually correlates with elements characteristic of the MnO₂, carbonate fluorapatite, and residual biogenic phases. In continental margin crusts, Te also correlates with FeOOH associated elements. In addition, Te is negatively correlated with water depth of occurrence and positively correlated with crust thickness. Q-mode factor analyses support these relationships. However, sequential leaching results show that most of the Te is associated with FeOOH in Fe-Mn crusts and ≤10% is leached with the MnO₂.Thermodynamic calculations indicate that Te occurs predominantly as H₅TeO₆⁻ in ocean water. The speciation of Te in ocean water and charge balance considerations indicate that Te should be scavenged by FeOOH, which is in agreement with our leaching results. The thermodynamically more stable Te(IV) is less abundant by factors of 2 to 3.5 than Te(VI) in ocean water. This can be explained by preferential (not exclusive) scavenging of Te(IV) by FeOOH at the Fe-Mn crust surface and by Fe-Mn colloids in the water column. We propose a model in which the extreme enrichment of Te in Fe-Mn crusts is likely the result of an oxidation reaction on the surface of FeOOH. A similar oxidation process has been confirmed for Co, Ce, and Tl at the surface of MnO₂ in crusts, but has not been suggested previously to occur in association with FeOOH in Fe-Mn crusts. Mass-balance considerations indicate that ocean floor Fe-Mn deposits are the major sink for Te in the oceans. The concentration and redox chemistry of Te in the global ocean are likely controlled by scavenging on Fe-Mn colloids in the water column and Fe-Mn deposits on the ocean floor, as is also the case for Ce.     

Rescaling of Access and Property Relations in a Frontier Landscape: Insights from Jambi,Indonesia

The recent expansion of protected areas and oil palm plantations in Jambi (Sumatra), Indonesia, has been notably disruptive. This article investigates the scalar dimensions of land conflicts within a privately managed conservation area. We built on qualitative research focusing on struggles related to the formation of two informal settlements within the conservation area. Results indicate that, especially in the context of rapid rescaling (e.g., decentralization), new power constellations emerge, thereby altering preexisting property relations. We argue that competing scales of meaning and regulation are structuring the ability of actors to access land and, consequently, reflect tensions between structure and agency.     

Observations of longitudinal roll vortices during arctic cold air outbreaks over open water

An evolving convective Arctic planetary boundary layer (PBL) containing longitudinal roll vortices (rolls) was observed with aircraft data during the 1983 Marginal Ice Zone Experiment and the 1984 Arctic Cyclone Experiment.The PBL is observed to grow rapidly as the very cold and dry air flows off the ice over the relatively warm water. There is very large sensible heat flux, a result of the large surface-air temperature differences. Coherent structures were identified in these PBL's by use of power, coherence squared and phase spectra of the data. A systematic method of separating the rolls from organized thermal plumes was devised, based on theoretical characteristics for roll circulations and the resulting modified mean wind profile. The rapid mixing by the rolls aids in the establishment of equilibrium and an observed adiabatic modified mean Ekman layer. Rolls that form in a thermally neutral atmosphere over ice have different characteristics than those that appear in the unstable stratification over water. The rolls become increasingly more convective in character with distance from the ice edge. They have aspect ratios (wavelength/PBL height) that decrease with distance from the ice edge in agreement with linear theory. This is in contrast to the cloud street wavelength to inversion height ratio which is observed to increase downwind from the ice edge.     

Effects of toluene on the survival,respiration, and adenylate system of a marine isopod

Median times to narcotization (ET₅₀) of Cirolana borealis Lilljeborg by various levels of toluene in seawater were determined. Narcotization quickly became irreversible, and the ET₅₀ values can be regarded as estimates of median lethal times. Respiratory rate, ATP concentration, and energy charge (E.C.) were not significantly affected by sublethal toluene levels which caused behavioural disturbance. At 12.5 ppm of toluene (nominal concentration; ET₅₀:69 h) ATP dropped gradually to less than 1% and E.C. to about 50% of the control values during 8 days, after which time all the individuals were dead. At 125 ppm neither ATP concentration nor E.C. changed significantly during 24 h although the animals were inactive after about 1 h and died within 100 h. Due to the high degree of stabilization of adenine nucleotide levels and E.C. during environmental changes, these parameters do not appear useful as general indices of stress in environmental pollution studies.