47242 research outputs found
Sort by
The multi-criteria analysis for dumped munition prioritization tool (MCA-DuMP): Handbook and Criterion Descriptions
No full text
Optimisation of contamination-control, extraction and analysis of trace levels of phthalic acid esters in seawater
No full textQuantification of phthalates and phthalic acid esters (PAEs) in seawater is challenging due to matrix overlaps, self-absorbance and contamination from plastic laboratory materials that release PAEs. Plastic materials are ubiquitous in sampling devices, analytical instruments and the laboratory environment, thereby making it more difficult to reliably analyse trace concentrations of PAEs in collected seawater samples. In the current study a reliable protocol was established for OAE analysis in seawater including control of blank contamination and optimisation of experimental conditions. The mass of PAEs in blank tests of selected materials ranged from 3 ± 0.7 to 35 ± 6 ng for liquid-liquid extraction (LLE) and from 5 ± 1.8 to 63 ± 15 ng for solid-phase extraction (SPE). Higher blank values were measured for dibutyl phthalate (DBP, 35 ± 6 ng, 12 ± 3 ng), and di(2-Ethylhexyl) phthalate (DEHP, 63 ± 12 ng, 23 ± 5 ng) in LLE and SPE, respectively. Recoveries of PAEs in LLE were 90–97%, and up to 86–90% for SPE. The method quantification limits (MQL) for PAEs were 10–20 ng L–1 for LLE and 10–35 ng L–1 for SPE. In coastal seawater samples from Sharm Obhur, PAE concentrations obtained using SPE ranged from 138–282 ng L–1 (Di(2-ethylhexyl) phthalate, BEP), 143–276 ng L–1 (diethyl phthalate, DEP) and 8.9–238 ng L–1 (DBP). The method shows lower MQL values for LLE and SPE than reported values of 10–100 ng L–1 and 30–100 ng L−1, respectively. The MQL values meet the requirements for PAEs analysis in seawater. The results suggest that LLE or SPE combined with GC-MS form efficient methods to quantify PAEs concentrations in seawater
Ecology of Moroteuthopsis longimana at the sub-Antarctic Prince Edward Islands, revealed through stable isotope analysis of squid beaks
No full textUnderstanding the underlying ecological factors that affect the distribution patterns of organisms is vital for their conservation. Cephalopods such as giant warty squids Moroteuthopsis longimana are important in the diets of marine predators, including grey-headed albatrosses Thalassarche chrysostoma, yet our understanding of their habitat and trophic ecology remains limited. We investigated the habitat and trophic niche utilised by M. longimana through the delta C-13 and delta N-15 profiles captured in their beaks. M. longimana beaks were collected around grey-headed albatross nests at the Prince Edward Islands during 2004 and 2013 (n = 40 beaks). The results showed distinctly Antarctic distributions (delta C-13 = -24.0 +/- 1.0 parts per thousand, mean +/- SD) for M. longimana, consistent with albatrosses foraging at the Southwest Indian Ridge, as opposed to broader foraging zones utilised by albatrosses from Iles Crozet and Iles Kerguelen. Slightly lower delta N-15 values (5.4 +/- 0.7 parts per thousand) were found compared to other islands in the Indian Sector of the Southern Ocean, which may indicate more crustaceans in the squid diets. Sequential sampling along the lateral walls of individual beaks (n = 4) revealed ontogenetic shifts in delta C-13 and delta N-15 values, but individual variation in these shifts requires further investigation
Variable roles of oceanic transform faults in plume dispersion along segmented mid-ocean ridges
No full textHighlights
• Three interaction modes: on-ridge, off-ridge, and on-transform–fracture zone.
• Transform faults act as barrier-, bridge-, or booster-like on plume dispersion.
• Roles of transforms in plume dispersion depend on plume–ridge–transform geometry.
Abstract
Transform faults are integral to the mid-ocean ridge system, yet their role in modulating mantle plume dispersion along segmented ridges remains poorly understood. By compiling and analyzing the tectonic characteristics of 24 global plume–ridge–transform systems, we categorize them into three types: on-ridge, off-ridge, and on-transform–fracture zone interactions. Using 3D geodynamic models, we evaluate how transform fault length, plume–transform distance, plume–ridge distance, and spreading rate influence plume behavior. Our results reveal that transform faults can play three distinct roles in plume dispersion, depending on plume positioning relative to the ridge–transform system. Barrier-like behavior occurs when transform offset increases the separation between the plume and two ridge segments and plume material needs to cross the lithospheric discontinuity boundary along the transform fault to spread, thus strongly reducing along-ridge plume dispersion (e.g., on-ridge plumes and most off-ridge plumes beneath the outside corner of a ridge segment). Bridge-like behavior arises when plumes beneath fracture zones or near ridge–transform intersections bypass these discontinuities, enabling dispersion to both ridge segments with little reduction. Booster-like behavior emerges under certain geometries, such as inside-corner plumes or plumes beneath transform centers. In these scenarios, dispersion is enhanced by shorter plume–ridge distance, avoidance of lithospheric discontinuities, and localized strengthening of along-ridge mantle flow near the transform fault induced by strike-slip motion. These findings highlight the geometric controls on plume–ridge–transform interactions and underscore the complexity of transform fault influence in plume dynamics
Trace elements in rivers draining tropical peat swamp forests
No full textTropical peat swamp forests are wetland ecosystems characterized by peat accumulation from partially decomposing organic matter in lowland areas. In southeast Asia, tropical peat swamps account for about 11-14% of the carbon stored in all peatlands. However, converting these ecosystems for agricultural activities has potential implications for releasing materials, including trace elements. This study explores the interplay of anthropogenic activities and trace element export to the estuaries and coastal waters.
The result indicated the role of pH, salinity, dissolved organic carbon (DOC), and iron (Fe) and manganese (Mn) oxides in regulating the global biogeochemical cycling of trace elements. Seasonal variabilities contribute to trace element fluxes, especially during the wet season (December), with implications for material supplies to the coastal waters. The NICA- Donnan model was used to investigate the combined impact of DOC and pH on the formation of solid iron hydroxide (Fe(OH)3(s)). The Maludam River was predicted to be supersaturated for Fe hydroxides, and the field results affirmed our model prediction. The output showed Fe and Cu had a strong affinity for DOC and, to a lesser extent, Al and Ni in the conditions prevailing at the study sites.
Furthermore, the concentration of DOC (12000 μmol L−1) in the natural peat increased, while the concentration of trace elements increased in the disturbed peat. Porewater samples from the disturbed and natural peat also indicated enhanced trace element concentrations in the disturbed peat compared to the natural peat. The observed increase in trace element concentrations reflects the impact of peat conversion on agricultural activities and catchment chemistry
World Oceean Review: Marine Biodiversität - das vitale Fundament unserer Meere
No full textDas Leben auf der Erde ist untrennbar mit dem Ozean verbunden. Dessen Artenvielfalt kennen wir allerdings bislang nur in Ausschnitten. Sie ist jedoch unverzichtbar für das Wohlergehen der Menschheit. Je gesünder und bunter das Leben im Meer, desto besser für Mensch und Natur. Welche Arten aber leben im Meer und welche Umweltfaktoren bestimmen ihre Verteilung oder die Größe ihres Lebensraumes? Aus welchen Gründen nimmt der Artenreichtum des Ozeans ab und wie ließe er sich erfolgreich schützen? Antworten auf diese und viele andere Fragen zum Leben im Meer liefert die neue Ausgabe des World Ocean Review
A Comparison Between the (μ+ λ) and (μ, λ) Genetic Algorithm
No full textFor genetic algorithms, there are many strategies to choose individuals: general, and elitist. The general approach is the simplest approach, in which the algorithm replaces the whole current population by the offspring generated so far. In the elitist strategy, parents and offspring compete for survival. With the elitist approach, only the best individuals are selected from the current generation. In this article, we compare the results of the non-elitist genetic algorithm, and the elitist genetic algorithm improved with the parenting fitness. Results show that the elitist genetic algorithm improved with parenting fitness outperforms the non-elitist one in 93% cases
Evidence for the transition from Cretaceous asthenospheric to Cenozoic lithospheric melting sources on the Chatham Islands, New Zealand
No full textHighlights
• New major/trace element and Sr-Nd-Pb-Hf isotope data from the Chatham Islands.
• Evolution from Cretaceous St. Helena HIMU-type to Cenozoic HIMU-like composition.
• Geochemistry reflects change from asthenospheric to lithospheric melting source.
Abstract
Late Cretaceous–Cenozoic diffuse intraplate volcanism is widespread across the continent of Zealandia, but only in the Chatham Islands have intraplate volcanoes erupted repeatedly for over 80 million years. Here we use new whole rock major and trace element, and Sr-Nd-Pb-Hf isotope geochemical data from the Chatham Islands to characterize changes in the geochemical fingerprint of the melting sources over time to provide a better understanding of Zealandian intraplate volcanism. The first and most voluminous magmatic stage (∼85–75 Ma; Southern Volcanics) at the Chatham Islands has an isotopic signature nearly identical to the St. Helena HIMU-type endmember. The following Red Bluff Tuff volcanic stage (∼65–50 Ma) has a distinct isotopic composition, influenced by an enriched mantle one-type, probably derived from the neighboring Hikurangi Plateau. The following magmatic stages, the Northern Volcanics (∼40–30 Ma) and Rangitihi Volcanics (< 10 Ma) extend from this compositional array to compositions with higher 206Pb/204Pb and 208Pb/204Pb ratios at given 207Pb/204Pb ratio. This ‘Cenozoic array’ reflects radiogenic in-growth with high U/Pb and Th/U ratios derived from a metasomatized lithospheric mantle source. The recorded temporal geochemical evolution confirms a widespread Late Cretaceous HIMU melting event in Zealandia, which metasomatized the lithospheric mantle forming the Cenozoic HIMU-like melting source. This also reflects a change from asthenospheric to lithospheric melting sources. The nearly continuous volcanism during the Cenozoic in the Chathams and wider eastern Chatham Rise could have been triggered by asthenospheric upwelling causing melting of the base of the metasomatized lithosphere. Considering the fast-northward motion of Zealandia during the Cenozoic (∼2500 km), the upwelling is most plausibly explained by the change in lithospheric thickness caused by the partly subducted Hikurangi Plateau that lies directly north of the Chatham Islands