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21.
Numerical studies of vertical Cl−, δ2H and δ18O profiles in the aquifer–aquitard system in the Pearl River Delta,China 下载免费PDF全文
Sedimentation may have a significant effect on the transport of solutes and environmental isotopes in sediment. The depth profiles of the Cl?, δ2H and δ18O in a borehole in the aquifer–aquitard system in the Pearl River Delta (PRD), China, were obtained by centrifuging the core sediment samples. A one‐dimensional model based on the sedimentation and sea level changes of the PRD during the Holocene was built to investigate numerically the transport mechanisms of Cl?, δ2H and δ18O. The sedimentation process was modelled as a moving boundary problem with the moving rate equal to the sedimentation rate. The model was calibrated and the parameters were obtained by comparing simulated and measured data. Very good agreement between all the three observed profiles and the simulated ones demonstrates the reliability of the model and the parameters. Simulation results show that the shapes of the curves are controlled by the combination of sedimentation and upper boundary conditions. Diffusion solely is adequate to reconstruct the observed profiles, which indicates that diffusion is the dominant vertical transport mechanism. The effective diffusion coefficients of the aquitard and the aquifer equal to 5.0 × 10?11 and 2.0 × 10?10 m2/s, respectively. The results of this study will help in understanding the transport mechanisms of solutes and environmental tracers in deltas with geology and hydrogeology similar to the PRD. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
22.
Natural Hazards - The adverse impact of climate change-associated extreme weather events is becoming more significant globally, particularly the flood impact on coastal and low-lying areas such as... 相似文献
23.
Roger Kwok Jimmy C. H. Fung Alexis K. H. Lau Zion S. Wang 《Journal of Atmospheric Chemistry》2012,69(1):1-22
The Tagged Species Source Apportionment (TSSA) algorithm is applied to study contributions to pollutants PM sulfate, SO2 and elemental carbon (EC) in Hong Kong by emitting sectors as well as non-emitting sources within and beyond the Pearl River Delta (PRD) region. We look at three areas of Hong Kong: western new towns, central downtown, and eastern countryside. Pollutant transport from beyond the PRD influenced all three areas during January and October 2004 but the source sectors impacting the three areas were different. Specifically, power plant SO2 from Hong Kong and Shenzhen, and vehicle EC from Shenzhen contribute to 11?~?66?% of SO2 concentration, and 33?~?75?% of EC concentration in the western new towns, respectively. Ships in and around Hong Kong contribute 8?~?56?% to the sulfate concentration in the downtown area, while local moving vehicles take up 28?~?81?% of the EC concentration there. The study also shows that diurnal variation of planetary boundary layer (PBL) causes day-night difference in SO2 by as much as 50?%. In addition, 13?~?38?% of all SO2 emissions have been converted to PM sulfate. 相似文献
24.
The exposure time is a variable which is usually not incorporated into models for toxicity. However, with persistent organic pollutants (POPs) exhibiting a nonspecific mode of action and lipophilic properties this variable can be modeled by the usage of the internal concentrations as a measure of the toxicity with fish. The bioconcentration process with fish is a relatively well understood and predictable process which allows the calculation of the internal lethal concentration. When the exposure time is relatively short the critical internal lethal concentrations are relatively constant for the group of POPs whereaas the LC50 measured in the ambient water is quite variable. When the exposure time is relatively long, results on the measurement of the critical internal concentration with fish over different exposure times has demonstrated that the internal lethal concentration falls with increasing exposure times in a consistent and predictable manner. This reduction in life expectancy can be described in a model which can be used to estimate the critical internal concentration for any exposure time. It also provides information useful in assessing the risk to fish and potentially other species due to the occurrence of residues of POPs in natural aquatic systems. It is suggested that these relationships can be extended to other groups of organisms and chemicals. 相似文献
25.
Recent advances on study of hadrosaurid dinosaurs in Heilongjiang(Amur) River area between China and Russia 下载免费PDF全文
Pascal Godefroit Pascaline Lauters Jimmy Van Itterbeeck Yuri L. Bolotsky Ivan Y. Bolotsky 《世界地质(英文版)》2011,(3):160-191
Four main dinosaur-bearing sites have been investigated in latest Cretaceous deposits from the Amur/Heilongjiang Region: Jiayin and Wulaga in China (Yuliangze Formation) ,Blagoveschensk and Kundur in Rus- sia (Udurchukan Formation) . More than 90% of the bones discovered in these localities belong to hollowcrested lambeosaurine hadrosaurids: Charonosaurus jiayinensis at Jiayin,Amurosaurus riabinini at Blagoveschensk, Olorotitan arharensis at Kundur,and Sahaliyania elunchunorum at Wulaga. Flat-headed hadrosaurine hadrosau- rids are much less numerous,but appear well diversified as well: Kerberosaurus manakini at Blagoveschensk, Wulagasaurus dongi at Wulaga,and a new genus at Kundur. Theropods are represented by shed teeth and isolated bones; isolated scutes and teeth discovered at Kundur are tentatively attributed to nodosaurids. Palynologi- cal studies suggest that these sites are probably synchronous with the Lancian’ vertebrate localities of western North America,which represent the youngest dinosaur faunas in this area. However,the latest Cretaceous dinosaur assemblages are completely different in the Amur/Heilongjiang region (lambeosaurines abundant,ceratopsids absent) and in western North America (ceratopsids abundant,lambeosaurines extremely rare or absent) . This probably reflects some kind of geographical barrier between both areas by Maastrichtian time rather than strong differences in palaeoecological conditions. 相似文献
26.
Myrl E. Beck Steven D. Sheriff Jimmy F. Diehl Ernest A. Hailwood Peter W. Lipman 《Earth and Planetary Science Letters》1977,37(1):124-130
Combining paleomagnetic data for 17 new sites from the northwest portion of the (Oligocene) San Juan volcanic field of southern Colorado with data for 29 sites previously published yields a paleomagnetic pole at 85°N, 114°E (with a 95% confidence circle of 7.5° radius). A further combination of the San Juan data with the results of other studies on rocks of Oligocene age from tectonically stable parts of North America gives a mid-Tertiary reference pole located at 81°N, 132.5°E, with a confidence circle of approximately 4°. Mid-Tertiary paleomagnetic poles for the western edge of the continent diverge markedly from this reference pole. 相似文献
27.
Tidal Fluctuation Influenced Physicochemical Parameter Dynamics in Coastal Groundwater Mixing Zone 总被引:1,自引:0,他引:1
Tidal fluctuation could modify the physicochemical parameters in coastal groundwater mixing zone (CGMZ) notably, which in turn largely impacts on the reactive transport, discharge, and cycling of carbon, nutrients, trace metals, and other dissolved constituents. In this study, to capture the dynamic of groundwater physicochemical parameters (e.g., salinity, dissolved oxygen, pH, temperature, and oxidation/reduction potential) under the effect of tidal fluctuation, in situ measurement of groundwater is conducted along a 2D transection at different tidal stages. The results demonstrate visible periodic variations of parameters like salinity, temperature, DO, and pH, while the groundwater pH oscillation displays a phase lag behind the tidal fluctuation. Furthermore, the salinity variation at the near-surface area is mainly controlled by the mixing process between the infiltrated seawater and groundwater. Barring the mixing process, the groundwater temperature at the near-surface area is also affected by day and night air temperature difference. Meanwhile, the depleting DO and declining pH indicate that the biodegradation via aerobic respiration is highly active in CGMZ and acts as one of the major impact factors for the DO dynamic. The sharp contrast between the high removal rate of DO (7.25 mmol m?3 day?1) and relatively low production rate of H+ (9.38 μmol m?3 day?1) demonstrates the existence of the processes consuming H+ and DO besides aerobic respiration such as dissolution of carbonates, and respiration of microorganism and mangrove roots. Moreover, owing to the mixing process, the salinity transition zone overlaps with the oxidization/reduction potential transition zone. The enrichment of Fe2+ and Mn2+ could well explain the highly reducing saline groundwater observed in this study. In a nutshell, all physicochemical parameters are sensitive to tidal fluctuation, which provides implication for further study on the variation of biogeochemical process in CGMZ. 相似文献
28.
Jimmy Byakatonda B P Parida Piet K Kenabatho D B Moalafhi 《Journal of Earth System Science》2018,127(2):25
Arid and semi-arid environments have been identified with locations prone to impacts of climate variability and change. Investigating long-term trends is one way of tracing climate change impacts. This study investigates variability through annual and seasonal meteorological time series. Possible inhomogeneities and years of intervention are analysed using four absolute homogeneity tests. Trends in the climatic variables were determined using Mann–Kendall and Sen’s Slope estimator statistics. Association of El Niño Southern Oscillation (ENSO) with local climate is also investigated through multivariate analysis. Results from the study show that rainfall time series are fully homogeneous with 78.6 and 50% of the stations for maximum and minimum temperature, respectively, showing homogeneity. Trends also indicate a general decrease of 5.8, 7.4 and 18.1% in annual, summer and winter rainfall, respectively. Warming trends are observed in annual and winter temperature at 0.3 and 1.5% for maximum temperature and 1.7 and 6.5% for minimum temperature, respectively. Rainfall reported a positive correlation with Southern Oscillation Index (SOI) and at the same time negative association with Sea Surface Temperatures (SSTs). Strong relationships between SSTs and maximum temperature are observed during the El Niño and La Niña years. These study findings could facilitate planning and management of agricultural and water resources in Botswana. 相似文献
29.
30.
Riccardo Briganti Giorgio Bellotti Leopoldo Franco Julien De Rouck Jimmy Geeraerts 《Coastal Engineering》2005,52(12):351-1174
This paper describes a new station for full-scale measurement of wave overtopping at the Rome yacht harbour rubble mound breakwater in Ostia (Italy) and the results of the successful first measurement campaign carried out during the winter season 2003–2004. The equipment and the research activities were supported by the EU project CLASH, focusing on scale effects for wave overtopping at coastal structures. The site is characterized by a very small tidal range, a long shallow foreshore and depth-limited breaking waves which interact with a shallow sloping porous rock structure. Overtopping water is collected by a steel tank installed on the crown slab behind the parapet wall. The measurement of water level variation inside the tank by means of two pressure transducers allows the calculation of individual overtopping volumes. Incident waves, sea levels and wind are also measured. During seven independent storms, more than 400 individual overtopping events were recorded and about 86 h of valid data are available. This extensive dataset is presented, discussed and then used for comparison with two commonly used overtopping prediction formulae based on small-scale model tests showing their tendency to underestimate the prototype results. A strong correlation between the hourly mean overtopping discharge and corresponding maximum volume is also presented. The paper generally confirms the validity of the approach used in Troch et al. (2004) [Troch, P., Geeraets, J., Van de Walle, B., De Rouck, J., Van Damme, L., Allsop, W., Franco, L., 2004. Full-scale wave overtopping measurements on the Zeebrugge rubble mound breakwater. Coastal Engineering 51, 609–628] for field measurement of wave overtopping. 相似文献