Remote and in situ plume measurements of acid gas release from La Soufrière volcano, Guadeloupe

This paper presents the first remote measurements of La Soufrière gas emissions since the fumarolic and seismic reactivation in 1992. The chemical composition of the plumes has been measured from May 2003 to September 2004 using an Open Path Fourier Transform InfraRed (OP-FTIR) spectrometer, up to 15 m downwind the South Crater. HCl is clearly detected (concentration between 2.4 and 12 ppmv) whereas SO₂ and H₂S generally remain below the detection limit of the OP-FTIR. Direct measurements of SO₂ and H₂S near the South Crater with a Lancom III analyzer show a fast decrease of their concentrations with the distance. Calculated Cl / S mass ratios are high: from 9.4 ± 1.7 at 15 m from the vent to 2.8 ± 0.6 at 140 m. The enrichment in HCl of the gas emitted at La Soufrière, observed since 1998, corresponds to the degassing of a magma enriched in Cl and depleted in S. This result agrees with isotopic measurements which suggest a magmatic origin of the gases. Readjustments inside the volcanic system may have taken place during the seismic activity beginning in 1992 and enhance the transfer of magmatic gases to the summit.     

TSIP中期地震预报方法在辽宁地区的应用与研究

本文用ＣＮ算法研究了辽宁省两个地震重点监视防御区的中强震前的强震发生概率增长时间,结果表明预测效果较好,有震报准率为９０％,ＴＩＰ预测警戒占时空率为３０％左右,Ｒ值评分为０．６左右。在ＴＩＰ预测的基础上,进一步用ＳＩＰ方法分析这两个区域的空间背景发震概率的不均匀分布。综合应用ＴＩＰ方法和ＳＩＰ方法,对辽宁省及邻近地区进行了试验性地震预报。     

Crustal make-up of the northern Andes: evidence based on deep crustal xenolith suites, Mercaderes, SW Colombia

Samples of the deep crust and upper mantle in the Northern Andes occur as abundant xenoliths in the Granatífera Tuff, a late Cenozoic vent in the Mercaderes area of SW Colombia. The lower crustal assemblage includes granulites, hornblendites, pyribolites, pyroxenites and gneisses; mafic rocks predominate, but felsic material is also common. P–T conditions for the pyribolite assemblages (i.e. Hbl+Fs/Scp+Grt+Cpx+Qtz±Bt), which are the best constrained, are 720–850 °C and 10–14 kbar, consistent with a deep-to-lower crustal origin. A notable feature of this xenolith suite is that it is dominated by hornblende. However, mineral reactions within the suite show that there is a transition from amphibolite to granulite facies, and there is a probable restite–melt relationship represented within the suite. However, the latter appears to be dominated by hornblende and garnet.The mafic rocks mostly lack the high Cr and Ni that would be expected of cumulates. Neither do they possess the positive Sr and Eu anomalies that would be consistent with resite or cumulate models for the lower crust. They bear greatest similarity to oceanic basalts (s.l.). The Rb contents of the xenoliths, whether mafic or silicic, are very low, and the more silicic members of the suite tend to have small positive Sr and Eu anomalies, which are transitional to adakitic compositions. The Sr isotopic compositions of the xenoliths lie between 0.704 and 0.705; however, the Nd isotopic compositions are much more variable, indicating considerable long-term heterogeneity. Few of the xenoliths can be compositionally recognised as metasedimentary; however, a sedimentary component is evident in the Pb isotopic compositions. Within these constraints, our favoured model is a deep crust formed by basaltic components (subduction–accretion?), and minor sediment, which is subject to an increase in thermal gradient to produce the granulites, any melting being dominated by hornblende-out reactions involving garnet. However, there is no evidence of any pervasive crustal melting, leading to the conclusion that the voluminous Andean magmatism arises from the mantle wedge.     

A Theoretical Framework for Hyperspectral Anomaly Detection Using Spectral and Spatial A Priori Information

This letter presents a new theoretical approach for anomaly detection using a priori information about targets. This a priori knowledge deals with the general spectral behavior and the spatial distribution of targets. In this letter, we consider subpixel and isolated targets that are spectrally anomalous in one region of the spectrum but not in another. This method is totally different from matched filters that suffer from a relative sensitivity to low errors in the target spectral signature. We incorporate the spectral a priori knowledge in a new detection distance, and we propose a Bayesian approach with a Markovian regularization to suppress the potential targets that do not respect the spatial a priori. The interest of the method is illustrated on simulated data consisting in realistic anomalies that are superimposed on a real HyMap hyperspectral image.     

Fate and effects of picric acid and 2,6-DNT in marine environments: toxicity of degradation products

The toxicity of transformation products of 2,6-dinitrotoluene (2,6-DNT) and 2,4,6-trinitrophenol (picric acid) were assessed in spiked sandy and fine-grained marine sediments and in seawater. Toxicity of pore water from sediments spiked with 2,6-DNT decreased for the macro-alga, Ulva fasciata, zoospores as biotransformation proceeded, but increased for the copepod, Schizopera knabeni, nauplii. The primary biotransformation product of 2,6-DNT, 2-amino-6-nitrotoluene, was also more toxic than the parent compound to copepod nauplii, but not to alga zoospores, in spiked seawater tests. Two biotransformation products of picric acid, picramic acid and 2,4-DNP, were more toxic than their parent compound. Porewater toxicity from picric acid-spiked sediments decreased significantly at the end of six-months incubation. Fine-grained sediment spiked with either ordnance compound had lower toxicity than its sandy counterpart after six months, suggesting faster microbial transformation in the former and production of less toxic products. Photo-transformation of 2,6-DNT in seawater resulted in a reduction in toxicity.     

Three-dimensional finite-element modelling of magnetotelluric data with a divergence correction

A finite-element method for computing the electric field in a 3-D conductivity model of the Earth for plane wave sources, thus enabling magnetotelluric responses to be calculated, is presented. The method incorporates in the iterative solution of the electric-field system of equations the divergence correction technique introduced for finite-difference solutions by Smith (1996). The correction technique accelerates the development of the discontinuity of the normal component of the approximate electric field across conductivity discontinuities. The convergence rate of the iterative solution is improved significantly, especially for low frequencies. The correction technique involves computing the divergence of the current density for the approximate electric field, computing the static potential whose source is this divergence of the current density, and ‘correcting’ the approximate electric field by subtracting from it the gradient of the potential. This is repeated at regular intervals during the iterative solution of the electric-field system of equations. For the method presented here, the Earth model is discretised using a rectilinear mesh comprising uniform cells. Edge-element basis functions are used to approximate the electric field and nodal basis functions are used to approximate the correction potential. The Galerkin method is used to derive the systems of equations for the approximate electric field and correction potential from the respective differential equations. A bi-conjugate gradient solver was found to be adequate for the system of equations for the correction potential; a generalised minimum residual solver was found to be better for the electric-field system of equations. The method is illustrated using the COMMEMI 3D-1A and 3D-2A models.     

Deciphering the weathering processes using environmental mineralogy and geochemistry: Towards an integrated model of laterite and podzol genesis in the Upper Amazon Basin

This article reports major results from collaborative research between France and Brazil on soil and water systems, carried out in the Upper Amazon Basin. It reveals the weathering processes acting in the partly inundated, low elevation plateaus of the Basin, mostly covered by evergreen forest. Our findings are based on geochemical data and mineral spectroscopy that probe the crystal chemistry of Fe and Al in mineral phases (mainly kaolinite, Al- and Fe-(hydr)oxides) of tropical soils (laterites). These techniques reveal crystal alterations in mineral populations of different ages and changes of metal speciation associated with mineral or organic phases. These results provide an integrated model of soil formation and changes (from laterites to podzols) in distinct hydrological compartments of the Amazon landscapes and under altered water regimes.     

Impact of the Doha outcome on surplus emission allowances and their effect on developed country emissions

The outcome from the December 2012 climate negotiations in Doha has clarified the rules regarding surplus units for the Kyoto Protocol. We summarize these new rules and estimate the resulting effective emissions during the second commitment period using our unit trade model. Other options to deal with surplus emission allowances are employed as benchmarks to assess the Doha outcome. The effective emissions for developed countries as a group under the Doha outcome could be 10–11 % below 1990 levels or 4–5 % points below business-as-usual levels for the second commitment period if we assume that non-Kyoto Protocol countries domestically achieve their targets. However, if mechanisms exist where non-Kyoto Protocol countries can trade units, their emissions could increase and effective emissions for developed countries could be 7–8 % below 1990 levels. In this low-ambition situation we find the main impact of the Doha surplus rules to be the introduction of the historical cap on emissions allowances. Without the effect of the cap, the Doha outcome allows the Parties to the second commitment period to emit at business-as-usual levels until 2020, while still leaving surplus units at the end of the second commitment period.