Geochemical evolution and timescale of seawater intrusion into the coastal aquifer of Israel

This study is an attempt to quantify the geochemical processes and the timescale of seawater intrusion into a coastal aquifer from changes in the major ionic composition of the water and the natural distribution of the cosmogenic isotopes ¹⁴C and ³H. For that purpose, we sampled saline and brackish groundwaters from the Israeli coastal aquifer. A multilayer sampler (MLS) was used to obtain very high resolution (10 cm) profiles across the fresh-saline water interface (FSI).The chemical and stable isotope data revealed three distinct water types (end members) that are located in different zones on the route to the coastal aquifer: (1) slightly modified Mediterranean seawater (SWS); (2) slightly diluted (with up to 20% fresh groundwater) saline groundwater (SDS); and (3) fresh groundwater (FGW).The SWS samples generally show an excess of total alkalinity and total dissolved inorganic carbon (DIC), and a depletion of ¹³C_DIC and ¹⁴C_DIC with respect to normal seawater indicating that anaerobic oxidation of organic matter is the first diagenetic reaction that affects seawater during its penetration into the bottom sediments. SDS waters appear when SWS is slightly diluted, gain Ca²⁺ and Sr²⁺, and is depleted in K⁺, suggesting that the main processes that transform SWS into SDS are slight dilution with fresh groundwater and cation exchange. At the fresh-saline water interface, SDS generally shows conservative mixing with FGW.Inspection of chemical data from coastal aquifers around the world indicates that intensive ion exchange in slightly diluted saline groundwater is a globally important phenomenon of seawater intrusion. Most of our saline groundwater samples contain substantial amounts of ³H suggesting that penetration of Mediterranean seawater and its inland travel to a distance of 50-100 m onshore occurred 15-30 yr ago. This is supported by the ¹⁴C_DIC mass balance that explains the relatively low ¹⁴C_DIC activities in the SDS as influenced by diagenesis and not by simple radioactive decay.     

The chronostratigraphy of a quaternary sequence at the distal part of the nile littoral cell,Haifa Bay,Israel

The current detailed chronostratigraphic framework of the last 1 Ma of an eastern Mediterranean sequence (Haifa Bay, Israel) aims to examine the relative roles of sea‐level changes, climate and tectonics. Seven continuous marine cores, up to ～120 m long, were recovered from shallow water depths. The cores were dated by optically stimulated luminescence, ¹⁴C, magnetostratigraphy, ²³⁰Th/²³⁴U, ²⁶Al/¹⁰Be, occurrence of index fossils and correlated to the global sea‐level curve and Marine Isotope Stages (MIS). The sedimentary sequence accumulated during the last ca. 1.0 Ma consists of 21 transgression–regression units with hiatuses between them. Five marine/terrestrial cycles, which occur in the lower part of the sequence, are attributed to the Jaramillo subchron and the Brunhes–Matuyama boundary, and correspond to MIS 29–21. The top ～50 m includes three sedimentary cycles deposited in the last ca. 400 ka. The regressive phases during this interval correspond to Glacial MIS 8, 6 and 2, while the transgressions correspond to Interglacial MIS 11, 7, 5 and 1. Thus, for the first time, this study documents the longest Quaternary succession dated so far in a key area of the Levant, sensitive to global history of sea‐level changes and glacial/interglacial fluctuations. Copyright © 2012 John Wiley & Sons, Ltd.     

地下水水源保护区范围计算的KLF法及其在徐州张集地区的应用

详细介绍了地下水水源保护区范围的计算方法:Krijgsman-Lobo-Ferreira(KLF)法,分别推导出了正水流梯度方向、负水流梯度方向和垂直于地下水流方向保护区范围的计算公式,并就方法的适用性及参数取值等问题进行了探讨.在徐州张集地区应用的结果表明,KLF法提供了一种计算地下水保护区范围的便捷、科学、有效的方法,计算结果对于确定地下水源保护区范围及有效保护地下水源具有实际意义.     

A review of the assessments of the major fisheries resources in South Africa

The waters off South Africa's coastline boast a rich mix of commercially fished species. Quantitative assessments of these marine resources have developed from simple methods first applied in the 1970s, to models that encompass a wide range of methodologies. The more valuable resources have undergone regular assessments in recent decades, with frequencies closely related to the management approach employed for each fishery. Many of these assessments form the operating models used to simulation-test candidate management procedures. This paper provides a comprehensive review of the assessments of 11 of the most important fisheries resources in South Africa. Some assessments use simple biomass dynamics models, whereas others are a hybrid of age- and length-based models, each designed to model the specific characteristics of the resource and fishery concerned. Many of the assessments have been disaggregated by species/stock and/or area as related multispecies/stock/ distribution hypotheses have arisen. This paper explores the similarities and differences in the data available and the methods applied. The review indicates that, whereas the status of three of these resources cannot be estimated reliably at present, the status of six resources is considered to be reasonable to good, whereas that of abalone Haliotis midae and West Coast rock lobster Jasus lalandii remains poor.     

Whose carbon is burnable? Equity considerations in the allocation of a “right to extract”

Carbon emissions—and hence fossil fuel combustion—must decline rapidly if warming is to be held below 1.5 or 2 °C. Yet fossil fuels are so deeply entrenched in the broader economy that a rapid transition poses the challenge of significant transitional disruption. Fossil fuels must be phased out even as access to energy services for basic needs and for economic development expands, particularly in developing countries. Nations, communities, and workers that are economically dependent on fossil fuel extraction will need to find a new foundation for livelihoods and revenue. These challenges are surmountable. In principle, societies could undertake a decarbonization transition in which they anticipate the transitional disruption, and cooperate and contribute fairly to minimize and alleviate it. Indeed, if societies do not work to avoid that disruption, a decarbonization transition may not be possible at all. Too many people may conclude they will suffer undue hardship, and thus undermine the political consensus required to undertake an ambitious transition. The principles and framework laid out here are offered as a contribution to understanding the nature of the potential impacts of a transition, principles for equitably sharing the costs of avoiding them, and guidance for prioritizing which fossil resources can still be extracted.     

Predatory pelagic fishes of the Bijagós Archipelago (Guinea-Bissau) show high overlap in diets dominated by sardinella

Knowledge of trophic interactions between the key components of marine communities is required to understand food-web dynamics and develop ecosystem-based management approaches. In West Africa, where fisheries sustain the livelihoods of a significant part of the human population, this understanding is even more urgent, especially in the face of rapidly expanding fisheries and some stock collapses in the region. We studied the feeding ecology of the Crevalle jack Caranx hippos, West African Spanish mackerel Scomberomorus tritor and Guinean barracuda Sphyraena afra in the Bijagós Archipelago, Guinea-Bissau. These are the most abundant pelagic predatory teleost fishes in the area, but little is known about their ecology despite being species with commercial and recreational value, and they likely also play an important role in various African coastal ecosystems. Our findings show a high degree of dietary overlap among these three predator species, despite some degree of segregation by prey size and type. All three predators depend on Sardinella maderensis as the most important prey, which together with other members of the Clupeidae represented 47–96% of the ingested prey items. There was little difference in the diets of the predators between the dry and rainy seasons. These novel findings suggest a ‘wasp-waist’-structured ecosystem in the Bijagós Archipelago in which S. maderensis is the central small-sized pelagic fish species, and stress the need for an ecosystem-based approach to fisheries management in the region, with precautionary measures taken to avoid the overexploitation of clupeids.     

The Spectroscopic Orbit of the Planetary Companion Transiting HD 209458

Three new silicon-bearing radicals of astrophysical interest, SiCCH and the two nearly isoenergetic isomers SiCN and SiNC, were detected in a laboratory discharge in their X2Pi ground states by Fourier transform microwave and millimeter-wave absorption spectroscopy. Hyperfine structure was observed in the low rotational transitions of the (2)Pi(1/2) ladder, and well-resolved Lambda-doubling was observed in both fine-structure ladders. With the spectroscopic constants derived from the laboratory measurements, the spectra of all three can be calculated to an uncertainty of less than 0.1 km s(-1) in equivalent radial velocity over the entire range of interest to radio astronomers. SiCN, with a dipole moment of 2.9 D, is probably the most promising of the three for astronomical discovery.     

Two centuries of coastal change at Caesarea,Israel: natural processes vs. human intervention

The coast at Caesarea, Israel, has been inhabited almost continuously for the last 2,400 years, and the archeological sites are today a major international tourist attraction. Because the sites straddle the shoreline, they are subject to constant damage by wave action, and must therefore be frequently restored. In this paper, local shoreline migrations over the last 200 years are investigated with the aim of distinguishing between natural and man-made coastal changes. In order to assess these changes accurately, geomorphological and sedimentological data were examined based on detailed beach profile measurements, bathymetric surveys, and grain-size analyses. In addition, series of old aerial photographs, as well as historical topographic maps and nautical charts were consulted. The results show that shoreline changes can be grouped into two main time periods. During the first period from 1862 to 1949 before the expansion of modern settlements, the position of the shoreline changed irregularly by up to 30 m. In the second period from 1949 onward, numerous coastal structures have been erected, and various coastal modifications have been carried out. The evaluation of the data suggests that human interventions have had relatively little effect on the overall position of the shoreline, as displacements ranged only from 5 to 18 m. Thus, coastal changes at Caesarea are predominantly due to natural wave action reflected in the heterogeneous geomorphological and sedimentological characteristics of the shore. This contradicts the common assumption that human activities are always mainly responsible for large-scale shoreline modifications in the region. It is concluded that, in order to implement meaningful mitigating countermeasures, coastal archeological sites need to be individually assessed with respect to the dominant factors causing local coastal change.     

Natural iodine in a clay formation: Implications for iodine fate in geological disposals

Iodine is one of the most problematic radioisotopes in the context of nuclear waste geological disposal due to its high mobility. Considerable effort has been dedicated to the measurement of its potential retardation during diffusive transport leading to conflicting results, from no retardation to significant retardation, leading in turn to considerable debate. The present study aims at providing new insights into this aspect of the iodine problem by careful quantification of iodine reservoirs in the Callovian-Oxfordian (COx) clay rock taken here as model material for these studies. The present study confirmed the ubiquitous presence of iodine at 1-5 mg kg⁻¹ level in the COx clayey formation. The iodide concentration level in the porewater is also confirmed at a value in the range ∼20-40 μmol L⁻¹, i.e. higher than the expected range of radio-iodine concentration in the far-field of the storage. Surprisingly, most of the iodine was found not to be associated with organic matter but rather in an inorganic form associated with carbonate minerals. This result has potentially significant implications for the fate of radio-iodine. In undisturbed far-field conditions, most natural iodine would not be accessible for isotopic exchange with radioactive iodine, reducing the effective Kd to negligible values. During laboratory experiments, good monitoring of the geochemical parameters (at least the Eh, pH, P_CO2, [Ca] and [Mg]) is mandatory to avoid iodine-bearing carbonate precipitation and to enable rigorous interpretation of the iodide diffusion/retention experiments.