排序方式： 共有10条查询结果，搜索用时 31 毫秒
1
1.
多环芳香烃由于诱发突变和致癌的性质威胁着人类的健康,近年来,其降解问题得到了广泛的关注。笔者研究了在没有光照的条件下,改变相对湿度(5%至30%之间),苯并芘(一种典型的多环芳烃物质)在石英,矾土,蒙脱石,高岭石,腐殖酸和吸附了腐殖酸的石英上的稳定性,继而可以检测出矿物表面催化多环芳烃降解的效果。苯并芘的稳定性主要是由吸附剂的物化性质决定的。石英表现出很好的催化效果,即便其表面被腐殖酸所包覆。在整个实验过程中(3天)吸附在蒙脱石和腐殖酸表面的苯并芘依然很稳定。实验装置中的湿度影响在某些特定的矿物中的苯并芘的稳定性。特… 相似文献
2.
Nick Marriner Jean-Philippe Goiran Bernard Geyer Valérie Matoïan Michel al-Maqdissi Marion Leconte Pierre Carbonel 《Quaternary Research》2012,78(1):35-49
Ras Ibn Hani peninsula, a wave-dominated tombolo (800 × 1000 m) on the Syrian coast, provides evidence for significant Holocene changes that can be linked to geological inheritance, rising post-glacial sea level, sediment supply and human impacts. Initial development of Ras Ibn Hani's coastal system began ~ 8000 years ago when shallow marine environments formed in a context of rising post-glacial sea level. Following relative sea-level stabilization ~ 6000 cal yr BP, beach facies trace the gradual formation of a wave-dominated sandbank fronted by a ~ 2300 × ~ 500 m palaeo-island whose environmental potentiality was attractive to Bronze Age societies. A particularly rapid phase of tombolo accretion is observed after ~ 3500 cal yr BP characterised by a two- to fourfold increase in sedimentation rates. This is consistent with (i) a pulse in sediment supply probably driven by Bronze Age/Iron Age soil erosion in local catchments, and (ii) positive feedback mechanisms linked to regionally attested neotectonics. Archaeological remains and radiocarbon datings confirm that the subaerial tombolo was probably in place by the Late Bronze Age. These data fit tightly with other eastern Mediterranean tombolo systems suggesting that there is a great deal of predictability to their geology and stratigraphy at the regional scale. 相似文献
3.
Rodriguez Fabian Toulkeridis Theofilos Sandoval Washington Padilla Oswaldo Mato Fernando 《Natural Hazards》2017,85(1):605-618
Natural Hazards - The Cotopaxi volcano in north-central Ecuador is one of the most dangerous volcanoes of the world due to its ability to generate far-reaching lahars, which are able to destroy... 相似文献
4.
Shuji TAMAMURA Tsutomu SATO Yukie OTA Ning TANG Kazuichi HAYAKAWA 《《地质学报》英文版》2006,80(2):185-191
The fate of Polycyclic Aromatic Hydrocarbons （PAHs） residing in the atmosphere has received enormous attention in recent years due to their mutagenic and carcinogenic risks on human health. In this context, the stability of pyrene （as a representative PAHs） on quartz, alumina, montmorillonite, kaolinite, humic acid and quartz coated with sorbed humic acid was investigated at controlled relative humidity （RH： i.e. 5% and 30%） without light irradiation in order to detect the presence of catalytic effect of mineral surface on PAHs decomposition. The stability of pyrene was found to depend strongly on the physicochemical properties of the substrates. Quartz showed a strong catalytic effect for the decomposition of pyrene even though it was coated with sorbed humic acid. Pyrene sorbed on montmorillonite and humic acid remained stable during the experimental period （i.e. 3 days）. Moisture in the experimental cell also affected the stability of pyrene in particular minerals. Especially, pyrene sorbed on alumina was rapidly decomposed at higher RH. However, there were almost no effect in the case of quartz, kaolinite and humic acid. Depending on the physicochemical properties of aerosols and RH, PAHs associated with minerals in the atmosphere would be decomposed and/or stably reside in the atmosphere. 相似文献
5.
6.
Yuko Ogata Kaoruko Mizukawa Satoru Iwasa Yukie Mato Keiji Okuda Michio Murakami Ruchaya Booyatumanondo Le Quang Dung Carlos Miguez Charles Moore Steven Weerts Erick Burres Michael Van Velkenburg Richard C. Lang Brenda Danner Richard C. Thompson 《Marine pollution bulletin》2009,58(10):1437-1446
Samples of polyethylene pellets were collected at 30 beaches from 17 countries and analyzed for organochlorine compounds. PCB concentrations in the pellets were highest on US coasts, followed by western Europe and Japan, and were lower in tropical Asia, southern Africa and Australia. This spatial pattern reflected regional differences in the usage of PCBs and was positively correlated with data from Mussel Watch, another monitoring approach. DDTs showed high concentrations on the US west coast and in Vietnam. In Vietnam, DDT was predominant over its metabolites (DDE and DDD), suggesting the principal source may be current usage of the pesticide for malaria control. High concentrations of pesticide HCHs were detected in the pellets from southern Africa, suggesting current usage of the pesticides in southern Africa. This study demonstrates the utility and feasibility of the International Pellet Watch approach to monitor POPs at a global scale. 相似文献
7.
8.
Guilhem Amin Douillet Benjamin Bernard Mlanie Bouysson Quentin Chaffaut Donald Bruce Dingwell Lukas Gegg Inga Hoelscher Ulrich Kueppers Clia Mato Vanille Ariane Ritz Fritz Schlunegger Patrick Witting 《Sedimentology》2019,66(5):1531-1559
Pyroclastic currents are catastrophic flows of gas and particles triggered by explosive volcanic eruptions. For much of their dynamics, they behave as particulate density currents and share similarities with turbidity currents. Pyroclastic currents occasionally deposit dune bedforms with peculiar lamination patterns, from what is thought to represent the dilute low concentration and fluid‐turbulence supported end member of the pyroclastic currents. This article presents a high resolution dataset of sediment plates (lacquer peels) with several closely spaced lateral profiles representing sections through single pyroclastic bedforms from the August 2006 eruption of Tungurahua (Ecuador). Most of the sedimentary features contain backset bedding and preferential stoss‐face deposition. From the ripple scale (a few centimetres) to the largest dune bedform scale (several metres in length), similar patterns of erosive‐based backset beds are evidenced. Recurrent trains of sub‐vertical truncations on the stoss side of structures reshape and steepen the bedforms. In contrast, sporadic coarse‐grained lenses and lensoidal layers flatten bedforms by filling troughs. The coarsest (clasts up to 10 cm), least sorted and massive structures still exhibit lineation patterns that follow the general backset bedding trend. The stratal architecture exhibits strong lateral variations within tens of centimetres, with very local truncations both in flow‐perpendicular and flow‐parallel directions. This study infers that the sedimentary patterns of bedforms result from four formation mechanisms: (i) differential draping; (ii) slope‐influenced saltation; (iii) truncative bursts; and (iv) granular‐based events. Whereas most of the literature makes a straightforward link between backset bedding and Froude‐supercritical flows, this interpretation is reconsidered here. Indeed, features that would be diagnostic of subcritical dunes, antidunes and ‘chute and pools’ can be found on the same horizon and in a single bedform, only laterally separated by short distances (tens of centimetres). These data stress the influence of the pulsating and highly turbulent nature of the currents and the possible role of coherent flow structures such as Görtler vortices. Backset bedding is interpreted here as a consequence of a very high sedimentation environment of weak and waning currents that interact with the pre‐existing morphology. Quantification of near‐bed flow velocities is made via comparison with wind tunnel experiments. It is estimated that shear velocities of ca 0·30 m.s?1 (equivalent to pure wind velocity of 6 to 8 m.s?1 at 10 cm above the bed) could emplace the constructive bedsets, whereas the truncative phases would result from bursts with impacting wind velocities of at least 30 to 40 m.s?1. 相似文献
9.
The inselberg structure and the local habitats of the Aïr mountains (Niger) are hypothesized to generate the coexistence of geographically isolated plant species with high conservation values. By studying the diversity and the distribution of plants on the highest peak of these mountains, we aimed to identify the respective effects of local and regional abiotic factors on isolated species. We estimated the regional effects of elevation by comparing 103 floristic quadrats with existing data in the adjacent lowlands, and we tested the effects of local abiotic variables on species distribution with ordination methods. Among the 151 species identified, 12 were recorded for the first time in Niger and 53 were not found in the adjacent lowlands, thus evidencing true mountain specificity. A five-class habitat variable separated a relatively high portion of Saharan-Mediterranean species (8%) located in volcanic gullies, and Guinean-Sudanian-Zambezian species (13%) located in granite boulders. These two habitats provided local abiotic refuges (boulders, gullies), which protected a pool of relictual species from aridity, and probably from grazers. Species persistence may thus be dependent both on regional and local abiotic variables. With probable high genetic divergence because of the surrounding desert matrix, their conservation value may be particularly high. 相似文献
10.
The life history of the freshwater shrimp Palaemonetes antennarius (H. Milne Edwards, 1837) was investigated from April 1993 to November 2002 at 13 sites in the delta of the Neretva River, Croatia. The sex ratio (males vs. females) was in favour of females throughout the study year . The breeding period lasts from April to August with a peak of 75% of the ovigerous female in June. The maximum number of eggs carried by ovigerous females was 73, and there was a positive significant linear correlation between fecundity (number of early embryonic stage eggs per female) and female body size (carapace length) (R2=0.698, p<0.01). The breeding period was longer in limnocrenes and lakes with oligohaline-limnic water than in other habitat types because the water is more rapidly warmed in spring and cooled more slowly in autumn in these habitats. Larvae were present from June to October, with a peak reaching 19.4% of the total population in June. The shrimps follow a synchronic univoltine life cycle with a short egg-laying period and a new summer generation. Their larvae, apparently having no ecological flexibility, did not appear in any environment with high oscillations of salinity. 相似文献
1