Anomalous travel times of teleseismic P-waves reflected under Arctic marine areas

The travel-time residuals of teleseismic PP waves can indicate velocity anomalies near the reflection points. Deep structure can thus be inferred in areas which are not well observed by conventional techniques. In this paper, published data are used to examine parts of the Arctic Ocean, the adjacent shelves and Greenland.Late reflections occur under part of the Alpha Ridge, and the Lomonosov Ridge near the North Pole, and early reflections tend to occur under much of the Nansen spreading ridge. It is suggested that a hotter than normal region underlies a section of the Lomonosov Ridge, while extensive mantle upwelling does not appear to occur directly under the Nansen Ridge, which may be a passive spreading center. A zone of very late reflections occupies much of the East Siberian Shelf. This may be due to intrusion of the asthenosphere into lithospheric sutures or thickening of the asthenosphere. travel-time delays under the rest of the Eurasian shelf are consistent with the known structure of the area. Late reflections in east Greenland and Baffin Bay could be due to Tertiary hot spot activity in these locations.     

Characterisation of choline esterases and their tissue and subcellular distribution in mussel (Mytilus edulis)

Acetylcholinesterase in mussel is potentially a useful biomarker of exposure to organophosphates (OP) in the marine environment. This study looked at cholinesterase activity in subcellular fractions of various tissues from the common mussel, Mytilus edulis. Measurement of enzyme rates demonstrated that although highest specific activity was found in foot 'mitochondrial' fraction, recovery of activity was very low. Gill 'microsomal' fraction had the second highest specific activity with a useful level of recovery and therefore was the most suitable tissue fraction for biomarker applications. Comparative studies of alternative alkylthiocholine substrates and competitive inhibitors suggest there is a single cholinesterase enzyme type present in this fraction. Inhibition of alkylcholine hydrolysis by BW284C51, specific to acetylcholinesterase in vertebrates, showed that cholinesterase activity in gill 'microsomal' fraction is inhibited by this compound but to a lesser extent than in vertebrate AChE. Inhibition of cholinesterase activity by azamethiphos in gill 'microsomal' fraction gave an IC50 of approximately 100 microM and showed both time and concentration dependence. However this indicates a lower potency compared to other animals and it is debatable whether mussel cholinesterase activity is useful as a biomarker of exposure in the field.     

Modeling projected changes of mangrove biomass in different climatic scenarios in the Sunda Banda Seascapes

ABSTRACT

Mangroves are critical in the ecological, economic and social development of coastal rural and urban communities. However, they are under threat by climate change and anthropogenic activities. The Sunda Banda Seascape (SBS), Indonesia, is among the world’s richest regions of mangrove biomass and biodiversity. To inform current and future management strategies, it is critical to provide estimates of how mangroves will respond to climate change in this region. Therefore, this paper utilized spatial analysis with model-based climatic indicators (temperature and precipitation) and mangrove distribution maps to estimate a benchmark for the mangrove biomass of the SBS in six scenarios, namely the Last Inter-glacial Period, the current scenario (1950–2000) and all four projected Representative Concentration Pathways in 2070 due to climate change. Despite mangroves gaining more biomass with climate change (the increase in CO₂ concentration), this paper highlighted the great proportion of below-ground biomass in mangrove forests. It also showed that the changes in spatial distribution of mangrove biomass became more variable in the context of climate change. As mangroves have been proposed as an essential component of climate change strategies, this study can serve as a baseline for future studies and resource management strategies.     

The divergence between acceptability of municipal services and urbanization in developing countries: insights from Accra and Sekondi-Takoradi,Ghana

Abstract

In most developing countries, the provision of municipal services and infrastructure invariably fails to match the pace and demands of urbanization. The outcome is often increased informality due to improper planning, official bureaucratic barriers and perhaps insufficient and shrinking public resources, which then makes leveraging private capital for public service provision imperative. Drawing on in-depth qualitative fieldwork in two Ghanaian cities, this paper aims to extend literature on the divergence between service provision and urbanization in developing countries. More specifically, it attempts to qualify recent macro-level data indicating that access to water, sanitation and electricity services in Accra and Sekondi-Takoradi is improving substantively. Contrary to dominant policy narratives circulating in Ghana, we illustrate how the acceptability of key municipal services within urban settings is often inadequate, and how acceptability is tied to spatial and temporal factors. We then identify and examine the reasons underpinning these variations. Through exploring residents’ perceptions of key services, and examining critically the possibility and feasibility of meeting urban service needs through leveraging private resources, this paper contributes to broader academic debates over urban service provision, while also feeding into contemporary policy discussions concerning how to achieve several of the Sustainable Development Goals by 2030.     

Hydrochemistry of carbonate terrains in alpine glacial settings

Nearly 200 analyses of meltwaters, ice and snow from three alpine glacial sites in carbonate terrain are summarized and discussed in terms of sources of solutes and kinetic controls on the progress of weathering reactions. Most data derive from the Swiss Glacier de Tsanfleuron which is based on Cretaceous and Tertiary pure and impure limestones. Two other sites (Marmolada, Italian Dolomites and the Saskatchewan Glacier, Alberta) are based on a mixed calcitic-dolomitic substrate. Most solutes originate from carbonate dissolution; moreover, where pyrite is present its oxidation supplies significant sulphate and forces more dissolution of carbonate. The ratios Sr²⁺/Ca²⁺ and Mg²⁺/Ca²⁺ are much higher in Tsanfleuron melt-waters than local bedrock, a phenomenon that can be reproduced in the laboratory at small percentages of dissolution. These anomalous ratios are attributed to incongruent dissolution of traces of the metastable carbonates Mg-calcite and aragonite. These phases also provide Na⁺ to solution. K⁺ is argued to originate mainly by ion-exchange on clays with solute Ca²⁺. Quartz and very minor feldspar dissolution are also inferred. Locally enhanced input from atmospheric sources is recognized by high Cl^? and associated Na⁺. The progress of weathering reactions has been evaluated by the trends in the data, computer modelling and some simple laboratory experiments. The most dilute samples show a trend towards removal of CO₂ to low partial pressures (c. 10^?5.5 atmospheres), reflecting initially rapid carbonate dissolution and relatively slow dissolution of gaseous CO₂. Later addition of atmospheric CO₂ or acid from pyrite oxidation allows further carbonate dissolution, but solutions show a wide range of saturations, and CO₂ pressures as high as 10^?2.2 where pyrite oxidation is important. In a carbonate terrain, measurement of electroconductivity (corrected to 25°C) and alkalinity in the field allows the following preliminary deductions (where meq stands for milliequivalents): where S is the minimum meq(Ca²⁺ + Mg²⁺) produced by simple dissolution of carbonate unconnected with pyrite oxidation. As with any proxy method, these deductions do not remove the need for chemical analysis of waters in a given study area.