Partitioning,bioavailability and origin of heavy metals from the Nador Lagoon sediments (Morocco) as a basis for their management

Nador Lagoon sediments show low trace element concentrations, and, in relation to the lagoon geochemical baseline, only some anomalies for As, Cd, Cu and Pb in the NW of the lagoon deserve to be outstanding. The distribution of major, minor and trace elements in the lagoon allows a breakdown in four zones. Between “Beni Ensar” and “Atelouane” (zone A), a quite confined zone rich in organic matter and S, the most important trace-element anomalies (As, Cd, Co, Cu, Mn, Pb, Zn) were found, mainly around industry and old mining activities. In the surrounding of the city of Nador (zone B), the anomalies correspond to Mn, Cu and Zn. The coastal barrier and Kebdana channel (zone C) show moderately concentrations of Cd, Cr and Ni at specific sites. The less polluted area is the SE of the lagoon (zone D), with no outstanding anomaly. In lagoon sediments, metal bioavailability is very low. The metal partitioning patterns show that Cu, Pb and Zn present a low availability because they are bounded to the residual, non-mobile phases of the sediments. Only in some sites, the fraction was associated with organic matter, which could be liberated easily. Arsenic is concentrated in both the residual phases and the organic matter, the latter being more available. Cadmium is mainly concentrated in some samples in the interchangeable fraction, which could be considered as a potentially toxic element because it is easily released. Concerning the origin of these trace elements, those found in zone A correspond mostly to a natural source by weathering of mount Gourougou volcanic rocks (As, Co, Cu, Pb and Zn), and to an anthropogenic origin (Cd) owing to the presence of industry and old mines. In zone B, contributions of Cu and Zn enter the lagoon through soil weathering and river-borne, and as anthropogenic pollution from urban wastes. In zone C the most important pollutant is Cd deduced to be of anthropogenic origin from the close industry and intensive agriculture area. In spite of the intense socio-economic activities developed in the Nador Lagoon (agriculture, industry, fishing, tourism) trace element concentrations in the sediments are low and with scarce bioavailability. Only the NW sector is relativity polluted because of geogenic features.     

The infrared dielectric properties of maghemite, γ-Fe2O3, from reflectance measurement on pressed powders

The infrared complex permittivity functions of three varieties of maghemite, γ-Fe₂O₃, having different degrees of vacancy ordering, have been determined from their IR reflectance spectra, measured at near to normal incidence on pressed powder pellets. The optical constants therefrom obtained have been verified by using them in the simulation of the corresponding absorption spectra for KBr-diluted pellets, and these are in excellent agreement with the experimental spectra. All calculations are based on a procedure for the estimation of the effective dielectric function of a mixture, which incorporates percolation features, recently developed by the authors.     

Reducing standard errors by incorporating spatial autocorrelation into a measurement scheme for soil carbon credits

Several studies have suggested that geostatistical techniques could be employed to reduce overall transactions costs associated with contracting for soil C credits by increasing the efficacy of sampling protocols used to measure C-credits. In this paper, we show how information about the range of spatial autocorrelation can be used in a measurement scheme to reduce the size of the confidence intervals that bound estimates of the mean number of C-credits generated per hectare. A tighter confidence interval around the mean number of C-credits sequestered could increase producer payments for each hectare enrolled in a contract to supply C-credits. An empirical application to dry land cropping systems in three regions of Montana shows that information about the spatial autocorrelation exhibited by soil C could be extremely valuable for reducing transactions costs associated with contracts for C-credits but the benefits are not uniform across all regions or cropping systems. Accounting for spatial autocorrelation greatly reduced the standard errors and narrowed the confidence intervals associated with sample estimates of the mean number of C-credits produced per hectare. For the payment mechanism considered in this paper, tighter confidence intervals around the mean number of C-credits created per hectare enrolled could increase producer payments by more than 100 percent under a C-contract.     

Pennsylvanian carbonate platforms adjacent to deltaic systems in an active marine foreland basin (Escalada Fm., Cantabrian Zone,NW Spain)

The Pennsylvanian marine foreland basin of the Cantabrian Zone (NW Spain) is characterized by the unique development of kilometre‐size and hundred‐metre‐thick carbonate platforms adjacent to deltaic systems. During Moscovian time, progradational clastic wedges fed by the orogen comprised proximal alluvial conglomerates and coal‐bearing deltaic sequences to distal shelfal marine deposits associated with carbonate platforms (Escalada Fm.) and distal clay‐rich submarine slopes. A first phase of carbonate platform development (Escalada I, upper Kashirian‐lower Podolskian) reached a thickness of 400 m, nearly 50 km in width and developed a distal high‐relief margin facing a starved basin, nearly 1000‐m deep. Carbonate slope clinoforms dipped up to 30° and consisted of in situ microbial boundstone, pinching out downslope into calciturbidites, argillaceous spiculites and breccias. The second carbonate platform (Escalada II, upper Podolskian‐lower Myachkovian) developed beyond the previous platform margin, following the basinward progradation of siliciclastic deposits. Both carbonate platforms include: (1) a lower part composed of siliciclastic‐carbonate cyclothems characterized by coated‐grain and ooid grainstones; and (2) a carbonate‐dominated upper part, composed of tabular and mound‐shaped wackestone and algal‐microbial boundstone strata alternating at the decametre scale with skeletal and coated‐grain grainstone beds. Carbonate platforms initiated in distal sectors of the foreland marine shelf during transgressions, when terrigenous sediments were stored in the proximal part, and developed further during highstands of 3rd‐order sequences in a high‐subsidence context. During the falling stage and lowstand systems tracts, deltaic systems prograded across the shelf burying the carbonate platforms. Key factors involved in the development of these unique carbonate platforms in an active foreland basin are: (1) the large size of the marine shelf (approaching 200 km in width); (2) the subsidence distribution pattern across the marine shelf, decreasing from proximal shoreline to distal sectors; (3) Pennsylvanian glacio‐eustacy affecting carbonate lithofacies architecture; and (4) the environmental conditions optimal for fostering microbial and algal carbonate factories.     

Response of single benthic metrics and multi-metric methods to anthropogenic pressure gradients, in five distinct European coastal and transitional ecosystems

In recent times many benthic indices have been proposed to assess the ecological quality of marine waters worldwide. In this study we compared single metrics and multi-metric methods to assess coastal and transitional benthic status along human pressure gradients in five distinct environments across Europe: Varna bay and lake (Bulgaria), Lesina lagoon (Italy), Mondego estuary (Portugal), Basque coast (Spain) and Oslofjord (Norway). Hence, 13 single metrics (abundance, number of taxa, and several diversity and sensitivity indices) and eight of the most common indices used within the European Water Framework Directive (WFD) for benthic assessment were selected: index of size spectra (ISS), Benthic assessment tool (BAT), Norwegian quality index (NQI), Multivariate AMBI (M-AMBI), Benthic quality index (BQI), (Benthic ecosystem quality index (BEQI), Benthic index based on taxonomic sufficiency (BITS), and infaunal quality index (IQI). Within each system, sampling sites were ordered in an increasing pressure gradient according to a preliminary classification based on professional judgement. The different indices are largely consistent in their response to pressure gradient, except in some particular cases (i.e. BITS, in all cases, or ISS when a low number of individuals is present). Inconsistencies between indicator responses were most pronounced in transitional waters (i.e. IQI, BEQI), highlighting the difficulties of the generic application of indicators to all marine, estuarine and lagoonal environments. However, some of the single (i.e. ecological groups approach, diversity, richness) and multi-metric methods (i.e. BAT, M-AMBI, NQI) were able to detect such gradients both in transitional and coastal environments, being these multi-metric methods more consistent in the detection than single indices. This study highlights the importance of survey design and good reference conditions for some indicators. The agreement observed between different methodologies and their ability to detect quality trends across distinct environments constitutes a promising result for the implementation of the WFD’s monitoring plans. Moreover, these results have management implications, regarding the dangers of misclassification, uncertainty in the assessment, use of conflicting indices, and testing and validation of indices.     

Some Insights into Topographic,Elastic and Self-gravitation Interaction in Modelling Ground Deformation and Gravity Changes in Active Volcanic Areas

Surface displacements and gravity changes due to volcanic sources are influenced by medium properties. We investigate topographic, elastic and self-gravitation interaction in order to outline the major factors that are significant in data modelling. While elastic-gravitational models can provide a suitable approximation to problems of volcanic loading in areas where topographic relief is negligible, for prominent volcanoes the rough topography could affect deformation and gravity changes to a greater extent than self-gravitation. This fact requires the selection, depending on local relief, of a suitable model for use in the interpretation of surface precursors of volcanic activity. We use the three-dimensional Indirect Boundary Element Method to examine the effects of topography on deformation and gravity changes in models of magma chamber inflation/deflation. Topography has a significant effect on predicted surface deformation and gravity changes. Both the magnitude and pattern of the geodetic signals are significantly different compared to half-space solutions. Thus, failure to account for topographic effects in areas of prominent relief can bias the estimate of volcanic source parameters, since the magnitude and pattern of deformation and gravity changes depend on such effects.     

华夏植物群起源中心的研究

要贺兰山一带石炭纪、二叠纪地层发育,晚石炭世早期至二叠纪的地层连续出露,其中富含植物化石,特别是晚石炭世纳缪尔B—C期的红土洼组含丰富的早期华夏植物群分子。笔者多年来的研究表明,在此连续剖面上,植物化石反映出植物群的演化趋势颇为明显,构成石炭纪和二叠纪植物群较为连续的演化序列。植物群中含有大量的华夏型分子,属典型的华夏植物群。内蒙古阿拉善左旗呼鲁斯太剖面晚石炭世早期红土洼组是迄今为止含华夏植物群的最有代表性层位,所含植物化石是目前已记载的最为丰富的晚石炭世早期华夏型植物组合,因此笔者认为贺兰山一带可视为华夏植物群的起源中心。     

Objective method for classifying air masses: an application to the analysis of Buenos Aires’ (Argentina) urban heat island intensity

Summary ?During recent years, numerous studies have examined the Buenos Aires urban climate, but the relationship between large-scale weather conditions and the Buenos Aires urban heat island (UHI) intensity has not been studied. The goal of this paper is to apply an objective synoptic climatological method to identify homogeneous air masses or weather types affecting Buenos Aires during winter, and to relate the results to the UHI intensity. A K-means clustering method was used to define six different air masses considering the 03:00, 09:00, 15:00 and 21:00 LT surface observations of dry bulb temperature, dew point, cloud cover, atmospheric pressure and wind direction and velocity at Ezeiza, the most rural meteorological station of the Buenos Aires metropolitan area (Fig. 1). Results show that the mean UHI intensity is at its maximum (2.8 °C) a few hours before sunrise when conditions are dominated by cold air masses associated with cold-core anticyclones, weak winds and low cloud cover. Inverse heat islands are found during the afternoon for all air masses indicating that surface processes are not dominant at that time. The relatively infrequent and warmest air mass is the only one that presents a mean negative urban-rural temperature difference (−0.1 °C) during the afternoon with the smallest diurnal cycle of the UHI intensity probably due to the prevailing high humidity and cloudy sky conditions. The paper provides an insight into the Buenos Aires urban–rural temperature difference under a variety of winter weather types and results could be useful to improve local daily temperature forecasts for the metropolitan area of Buenos Aires on the basis of the routine forecasts of weather types. Received October 24, 2001; revised June 12, 2002; accepted October 10, 2002