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Fossil record of Phanerozoic non-spicular sponges, beside of being important with respect to the lineage evolution per se, could provide valuable references for the investigation of Precambrian ancestral animal fossils. However, although modern phylogenomic studies resolve non-spicular demosponges as the sister group of the remaining spiculate demosponges, the fossil record of the former is extremely sparse or unexplored compared to that of the latter; the Middle Cambrian Vauxiidae Walcott 1920, is the only confirmed fossil taxon of non-spicular demosponges. Here, we describe carbonate materials from Devonian (Upper Givetian to Lower Frasnian) bioherms of northern France and Triassic (Anisian) microbialites of Poland that most likely represent fossil remnants of keratose demosponges. These putative fossils of keratose demosponges are preserved as automicritic clumps. They are morphologically distinguishable from microbial fabrics but similar to other spiculate sponge fossils, except that the skeletal elements consist of fibrous networks instead of assembled spicules. Consistent with the immunological behavior of sponges, these fibrous skeletons often form a rim at the edge of the automicritic aggregate, separating the inner part of the aggregate from foreign objects. To confirm the architecture of these fibrous networks, two fossil specimens and a modern thorectid sponge for comparison were processed for three-dimensional (3-D) reconstruction using serial grinding tomography. The resulting fossil reconstructions are three-dimensionally anastomosing, like modern keratose demosponges, but their irregular and nonhierarchical meshes indicate a likely verongid affinity, although a precise taxonomic conclusion cannot be made based on the skeletal architecture alone. This study is a preliminary effort, but an important start to identify fossil non-spicular demosponges in carbonates and to re-evaluate their fossilization potential. 相似文献
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This paper presents a methodology for quantifying the effectiveness of water-trading under uncertainty, by developing an optimization model based on the interval-parameter two-stage stochastic program (TSP) technique. In the study, the effectiveness of a water-trading program is measured by the water volume that can be released through trading from a statistical point of view. The methodology can also deal with recourse water allocation problems generated by randomness in water availability and, at the same time, tackle uncertainties expressed as intervals in the trading system. The developed methodology was tested with a hypothetical water-trading program in an agricultural system in the Swift Current Creek watershed, Canada. Study results indicate that the methodology can effectively measure the effectiveness of a trading program through estimating the water volume being released through trading in a long-term view. A sensitivity analysis was also conducted to analyze the effects of different trading costs on the trading program. It shows that the trading efforts would become ineffective when the trading costs are too high. The case study also demonstrates that the trading program is more effective in a dry season when total water availability is in shortage. 相似文献
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Residues of organochlorine pesticides in Hong Kong soils 总被引:22,自引:0,他引:22
It was short of research on the organochlorine pesticides (OCPs) residues in the soils of Hong Kong. Sixty-six representative soil samples were collected from the 46 sites covering five types of land uses in Hong Kong. Hexachlorohexanes (HCH) and 7 Stockholm Convention OCPs were analyzed by gas chromatograph (GC) equipped with a Nickel 63 electronic capture detector (muECD). The results presented that HCH and 5 Stockholm Convention pesticides were detected in Hong Kong soils although the detectable ratio varies to a great extent. The concentration sequence of the five detectable OCPs was HCH > dichlorodiphenyltrichloroethane (DDT) > hexachlorobenzene (HCB) approximately = Endrin > alpha-endosulfan. Among the OCPs and their homologues or isomers, beta-HCH and p,p'-DDE were the two predominant substances according to the concentrations and detectable ratios, concentrations of which in soils were averagely 6.12 microg kg(-1) and 0.41 microg kg(-1) respectively. Soil horizon samples of 0-10 cm, 10-30 cm and >30 cm depth were selected from nine soil profiles to demonstrate the depth distributions of DDT and HCH in soil profiles. Concentrations of HCH tended to increase gradually from the topsoil to bottom layer while the lowest concentration of DDT is usually found in the subsoil (10-30 cm) in most sampling sites. In addition, close correlations of pH(KCl) and total organic carbon (TOC) with HCH indicated an effect on the residues of HCH caused by these two soils properties, but such relationships were not found with DDT or other OCPs. 相似文献
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Marie Trydeman Knudsen Qiao Yu-Hui Luo Yan Niels Halberg 《Journal of Cleaner Production》2010,18(14):1431-1439
Growing global trade with organic products has increased the demand for environmental impact assessments during both production and transport. Environmental hotspots of organic soybeans produced in China and imported to Denmark were identified in a case study using a life cycle assessment approach. Furthermore, environmental impacts of organic and conventional soybeans at farm gate were compared in the case study. The total global warming potential (GWP) per ton organic soybeans imported to Denmark revealed that 51% came from transportation and 35% from the farm level. Comparing organic and conventional soybean at farm gate showed that GWP, non-renewable energy use, acidification and eutrophication was lower per ton organic soybeans, whereas land use was slightly higher. 相似文献
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