Tributyltin and polycyclic aromatic hydrocarbon levels in Mobile Bay, Alabama: a review     

Peachey RB 《Marine pollution bulletin》2003,46(11):1365-1371

A review of the levels of polycyclic aromatic hydrocarbons (PAH) and tributyltin (TBT) in sediments from Mobile Bay, Alabama, shows that overall levels of PAH decrease from the upper bay (RI) to the lower bay (RIV). Analysis of PAH ratios indicate that pyrogenic sources such as fossil fuel combustion are dominant. There are so few data on TBT in sediments that spatial trends cannot be identified.Levels of PAHs in oyster tissues decrease from the upper bay (RI) to the lower bay (RIII). Although there is no significant temporal trend for PAH levels in bivalves for the US; in the bay, levels in Region II (RII) have decreased significantly and are currently below the national median. There is no trend in Region III (RIII), where levels remain below RII and the national median. RI and RIV had too few data for trend analysis.Mean levels of TBT in oyster tissues decrease from the upper bay (RI) to the lower bay (RIII). Temporal trend analysis indicates a significant decreasing trend for TBT in the US but no significant trend was detected for RII and RIII in Mobile Bay. TBT levels in RII are consistently higher than levels in the US and RIII, which are similar. Data from RI are too limited for analysis and there are no data for RIV.  相似文献   

The Impact of Herder Sedentarization on Natural Resource Access in Northeastern Ghana     

Rita Yembilah  Miriam Grant 《社会与自然资源》2014,27(6):621-635

The Fulani of West Africa have increasingly migrated to humid West Africa since the Sahelian droughts of the 1970s, drawing opposition from indigenous groups that are concerned about the deprivation of their livelihood and monopolization of resources for herders’ livestock. This research, which involved farmers, shepherds, and Fulani herders, addressed three issues: the nature of indigenous grazing and watering regimes, shepherd–herder relations, and herders’ impact on resource access for indigenes’ livestock. The research indicates that in-community and off-community platforms for resource access exist. The former has not been impacted by the herders; the latter has experienced changes insufficient to constitute an overhaul of resource access at the expense of indigenes’ livestock. Instead, a “shepherd–herder” category of resource access has emerged that is characterized by negotiation for resource space, opening avenues for addressing broader resource access issues, and typically tense indigene–herder relationships.  相似文献   

Simulating sub-daily hydrological process with SWAT: a review     

Tássia Mattos Brighenti  Nadia Bernardi Bonumá  Raghavan Srinivasan  Pedro Luiz Borges Chaffe 《水文科学杂志》2013,58(12):1415-1423

ABSTRACT

The Soil and Water Assessment Tool (SWAT) is a watershed-scale hydrologic model that integrates water quantity and quality modules. Despite the large amount of knowledge on the SWAT model, specific understanding of sub-daily applications remains limited. In this review, we identify the shortcomings and possible ways forward in simulating sub-daily processes with the model. A literature review was conducted, along with a participatory method based on a questionnaire. We reviewed 28 scientific articles and categorized them into: (i) model development, (ii) streamflow methods comparison, (iii) water quality, and (iv) other applications. We found that using sub-daily data improves hydrograph peak simulation, while for medium flows use of daily data was better. From all the reviewed studies, a 1-hour time step was the most suitable time scale for the sub-daily model application. The participatory questionnaire confirmed the hypothesis that the main challenge for using the sub-daily routine was the lack of high-resolution data.  相似文献   

Effects of coastal orientation and depth on the distribution of subtidal benthic assemblages     

Gustavo M. Martins  Rita F. Patarra  Nuno V. Álvaro  Afonso C. L. Prestes  Ana I. Neto 《Marine Ecology》2013,34(3):289-297

A better understanding of biological systems can only be gained if we understand what processes are important and how they operate to determine the distribution of organisms. Coastal orientation and depth can influence environmental conditions, including the degree of water motion and availability of light, which in turn may influence the horizontal and vertical patterns of organism distribution. Here, we used a mixed‐model design to examine the effects of coastal orientation and depth on the structure of benthic assemblages by comparing the abundance and distribution of macroalgae and invertebrates in shallow and deep waters on the opposing coasts of São Miguel. Generally, coastal orientation had little influence on the distribution of most taxa. In contrast, significant differences were generally associated with depth, although patterns were spatially variable at the scale of locations. This study suggests that depth, and processes operating at the scale of location, but not at the scale of the coast, have an important influence on these assemblages, and that failure to recognise such a scale of variability may hamper our ability to better understand the processes that structure these communities.  相似文献   

Clay minerals in sediments of Portuguese reservoirs and their significance as weathering products from over-eroded soils: a comparative study of the Maranhão, Monte Novo and Divor Reservoirs (South Portugal)     

Rita M. F. Fonseca  Fernando J. A. S. Barriga  Patrícia I. S. T. Conceição 《International Journal of Earth Sciences》2010,99(8):1899-1916

The Southern region of Portugal is subjected to several forms of over-erosion. Most leached products, mainly composed of fine particles containing nutrients, metals or pesticides, are easily transported by river flows. When these are hindered by a physical barrier such as a dam, the particulate load accumulates on the bottom of the reservoirs, often leading to a pronounced decrease of water quality. Bottom sediments from three reservoirs were subjected to grain-size analysis and a study of clay minerals by X-ray diffraction. Most sediments contain a diverse set of clay minerals, mostly illites, smectites, chlorites and kaolinites. The nature of the clay minerals reflects the nature of the parent rocks. During the cycles of transport and temporary deposition, they may undergo significant chemical and physical transformations, which lead to an increase of expandable properties and therefore, to a higher cationic exchange capacity, determining its important role as vehicles of environmental pollutants.  相似文献   

Characterization and provenance of the slabs of the Puigseslloses Megalith,Barcelona, Spain     

Enric Vicens  M. Eugenia Arribas  Xavier Clop  M. Rita Estrada  Eudald Maestro  Oriol Oms  David Serrat  Miquel Molist 《Geoarchaeology》2010,25(2):195-219

The Puigseslloses megalith tomb (Barcelona, Spain) is located on the summit of a hill in the Vic Plain where the sedimentary rocks that were used in its construction do not crop out. A sedimentological and petrological characterization of the monument's slabs and a multidisciplinary analysis of the outcropping materials in nearby areas has allowed the identification of three possible source areas associated with the Paleogene Banyoles Marls Formation and the Folgueroles Sandstone Formation and allows us to propose possible routes by which the slabs were transported from the catchment site to the place where the monument was built. In addition, the lithology and position of different slabs within the megalith denote the intention to separate the chamber from the corridor by using different types of slab. The position of the monument also reveals that tomb location was more of a priority than proximity to the slab sources. © 2010 Wiley Periodicals, Inc.  相似文献   

Geology of the Murcia Valley and Flood Plain Modifications in the Construction of the Circus Maximus,Rome, Italy     

Elena Carpentieri  Donatella de Rita  Giuseppe Della Monica 《Geoarchaeology》2015,30(6):483-494

This paper presents a morphological and hydrogeological reconstruction of the Murcia Valley at the location of the great Roman stadium Circus Maximus in Rome. We reconstruct a valley segment using ERT (electrical resistivity tomography) and geoarchaeological drilling data that identified three main layers. The basal layer, with high resistivity values and convex shapes, is correlated to alluvial gravel and lithified silt‐clay sediments. The middle layer shows low‐to‐medium resistivity values extending to concavities between the basal convex shapes. The very low resistivity values of this middle layer characterize elliptical to circular morphologies and have been ascribed to the presence of water‐saturated clay‐silt and peaty sediments. The surface layer is characterized by widespread lateral inhomogeneity interpreted as anthropogenic fill. The data indicate a pre‐Roman anastomosed alluvial plain subsequently modified by human intervention. In an effort to reclaim the valley for construction of the Circus, the Romans utilized the natural topography and created a central embankment, later becoming the Spina, by filling depressions with sand taken from adjacent bars. Our study contributes to (1) knowledge of the pre‐Roman landscape, (2) understanding anthropogenic modification of the Murcia Valley flood plain, and (3) archaeological interpretation of the monument.  相似文献