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61.
Sediment accretion was measured at four sites in varying stages of forest-to-marsh succession along a fresh-to-oligohaline gradient on the Waccamaw River and its tributary Turkey Creek (Coastal Plain watersheds, South Carolina) and the Savannah River (Piedmont watershed, South Carolina and Georgia). Sites included tidal freshwater forests, moderately salt-impacted forests at the freshwater–oligohaline transition, highly salt-impacted forests, and oligohaline marshes. Sediment accretion was measured by use of feldspar marker pads for 2.5 year; accessory information on wetland inundation, canopy litterfall, herbaceous production, and soil characteristics were also collected. Sediment accretion ranged from 4.5 mm year?1 at moderately salt-impacted forest on the Savannah River to 19.1 mm year?1 at its relict, highly salt-impacted forest downstream. Oligohaline marsh sediment accretion was 1.5–2.5 times greater than in tidal freshwater forests. Overall, there was no significant difference in accretion rate between rivers with contrasting sediment loads. Accretion was significantly higher in hollows than on hummocks in tidal freshwater forests. Organic sediment accretion was similar to autochthonous litter production at all sites, but inorganic sediment constituted the majority of accretion at both marshes and the Savannah River highly salt-impacted forest. A strong correlation between inorganic sediment accumulation and autochthonous litter production indicated a positive feedback between herbaceous plant production and allochthonous sediment deposition. The similarity in rates of sediment accretion and sea level rise in tidal freshwater forests indicates that these habitats may become permanently inundated if the rate of sea level rise increases.  相似文献   
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This study focuses on the characterization of leachate generated from Gohagoda dumpsite in Kandy, Sri Lanka, assessment of its spatial and temporal variations, and identification of subsurface canals and perched water bodies in the wetland system affected by the leachate flow. Leachate samples were collected monthly throughout dry and rainy seasons from different points of the leachate drainage channel over a period of 1 year and they were tested for quality parameters: pH, temperature, electrical conductivity, total dissolved soils, alkalinity, hardness, total solids, volatile solids, total suspended solids, volatile suspended solids, biochemical oxygen demand (BOD5), chemical oxygen demand, nitrate-nitrogen, nitrite-nitrogen, phosphates, ammonium-nitrogen, chloride, dissolved organic carbon, total organic carbon and heavy metals. Sequential soil extraction procedures were performed for the characterization of leachate-affected local soil. A geophysical survey using direct current resistivity technique was conducted at locations downstream of the dumpsite. Leachate characteristics indicated that the leachate is in the methanogenic phase and the results strongly suggest that the leachate may be polluting the river where the leachate is discharged directly. Leachate exceeds the allowable limits of Sri Lankan wastewater discharge standards for many of the parameters. Significant difference (P < 0.05) was observed for most of organic and inorganic parameters among all sampling locations. Many parameters showed a negative correlation with pH. The affected soils showed high heavy metal concentrations. Resistivity study confirmed a confined leachate flow at the near surface with few subsurface canals. However, no separate subsurface plume movement was observed. The results of this research can effectively be used for the establishment of an efficient and effective treatment method for the Gohagoda landfill leachate.  相似文献   
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In situ Pleistocene reefs form a gently sloping nearshore terrace around the island of Oahu. TIMS Th–U ages of in situ corals indicate that most of the terrace is composed of reefal limestones correlating to Marine Oxygen Isotope Stage 7 (MIS 7, ~ 190–245 ka). The position of the in situ MIS 7 reef complex indicates that it formed during periods when local sea level was ~ 9 to 20 m below present sea level. Its extensiveness and geomorphic prominence as well as a paucity of emergent in situ MIS 7 reef-framework deposits on Oahu suggest that much of MIS 7 was characterized by regional sea levels below present. Later accretion along the seaward front of the terrace occurred during the latter part of MIS 5 (i.e., MIS 5a–5d, ~ 76–113 ka). The position of the late MIS 5 reefal limestones is consistent with formation during a period when local sea level was below present. The extensiveness of the submerged Pleistocene reefs around Oahu compared to the relative dearth of Holocene accretion is due to the fact that Pleistocene reefs had both more time and more accommodation space available for accretion than their Holocene counterparts.  相似文献   
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We simulated the effects of irrigation on groundwater flow dynamics in the North China Plain by coupling the NIES Integrated Catchment‐based Ecohydrology (NICE) model with DSSAT‐wheat and DSSAT‐maize, two agricultural models. This combined model (NICE‐AGR) was applied to the Hai River catchment and the lower reach of the Yellow River (530 km wide by 840 km long) at a resolution of 5 km. It reproduced excellently the soil moisture, evapotranspiration and crop production of summer maize and winter wheat, correctly estimating crop water use. So, the spatial distribution of crop water use was reasonably estimated at daily steps in the simulation area. In particular, NICE‐AGR reproduced groundwater levels better than the use of statistical water use data. This indicates that NICE‐AGR does not need detailed statistical data on water use, making it very powerful for evaluating and estimating the water dynamics of catchments with little statistical data on seasonal water use. Furthermore, the simulation reproduced the spatial distribution of groundwater level in 1987 and 1988 in the Hebei Plain, showing a major reduction of groundwater level due mainly to overpumping for irrigation. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
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The High-Resolution Coronal Imager (Hi-C) was flown on a NASA sounding rocket on 11 July 2012. The goal of the Hi-C mission was to obtain high-resolution (≈?0.3?–?0.4′′), high-cadence (≈?5 seconds) images of a solar active region to investigate the dynamics of solar coronal structures at small spatial scales. The instrument consists of a normal-incidence telescope with the optics coated with multilayers to reflect a narrow wavelength range around 19.3 nm (including the Fe xii 19.5-nm spectral line) and a 4096×4096 camera with a plate scale of 0.1′′?pixel?1. The target of the Hi-C rocket flight was Active Region 11520. Hi-C obtained 37 full-frame images and 86 partial-frame images during the rocket flight. Analysis of the Hi-C data indicates the corona is structured on scales smaller than currently resolved by existing satellite missions.  相似文献   
69.
Cokriging is applied to the estimation of mineral resources in a polymetallic deposit. Several major steps, which should be taken in using cokriging, are highlighted as necessary practical considerations. The case study is related to an ultramafic copper-nickel deposit. Six elements, Cu, Ni, Au, Ag, Pt, and Pd, occurring in the deposit, are partitioned into three subgroups and the elements within each group are simultaneously estimated on the basis of over 4000 drill assays. A comparison was made between ordinary kriging and cokriging methods through cross-validation. The results show that cokriging has significantly improved the estimates of resources by reducing the overall estimation error by over 15% and the variance of error by over 20%.  相似文献   
70.
The flash spectra of the partial Sun and the chromosphere were obtained at the total solar eclipse on 7 March, 1970. We studied the distributions of the surface brightness of the continuum at six wavelengths in the visual region to compare them with the previous observations and the existing model atmospheres. All of the distributions show a shallow dip and a small hump similar to those of Heintze's observation at the 1954 eclipse. But the hump in our results is of quite a different type from that given by Heintze's revised model. It was found that none of the existing model atmospheres can reproduce this hump. The intensity distribution in the low chromosphere was also examined.  相似文献   
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