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21.
In the present study, an attempt has been made to characterize the biophysical land units in Kanholi bara river basin of sub-humid
tropical ecosystem of central India using remotely sensed data, field surveys and GIS based multi-criteria overlay analysis.
The geo-spatial database on elevation, slope, landforms, soil depth, soil erosion, land use/land cover and hydrogeomorphological
parameters has been generated using IRS-ID LISS-III satellite data coupled with soil survey data in GIS. The methodology followed
in characterization of biophysical land units in GIS includes assigning scores for different classes of the layers and weighatges
for different layers based on their characteristics and degree of influence on desired output. GIS based ‘multi criteria overlay’
analysis reveals seventeen distinct biophysical land units in the river basin. Severe (50.5-59.5) to very severe (59.5) biophysical
stress units are found in plateau spurs, isolated mounds, linear ridges, dissected plateau and escarpments. These zones are
associated with severe to very severe erosion, steep to very steep, extremely shallow soils, poor to very poor groundwater
prospects, wastelands and scrublands. The characterization of biophysical land units helps in analysis of their potentials,
problems and stress environment to plan and execute site-specific landscape management practices and maximize the productivity
from each biophysical land unit. The present study demonstrates that generation of geo-spatial database based on remotely
sensed data and field surveys in GIS and their analysis helps great extent in characterization of biophysical land units and
analysis of their stress environment for management. 相似文献
22.
SHARE Asia自动气象站网络:喜马拉雅山—喀喇昆仑山地区气候研究的一个必要组成部分 总被引:1,自引:0,他引:1
E. Vuillermoz L. Bertolani C. Smiraglia GP. Verza G. Tartari A. Marinoni P. Bonasoni 《地球科学进展》2006,21(12):1244-1253
Ev K2 CNR SHARE Asia计划的目标就是建立一个沿喜马拉雅山—喀喇昆仑山脉的监测网络,为气象学和气候研究提供参数,特别是为季风变化、大气化学、冰川学、高海拔湖沼学和古湖沼学等研究,同时也为准确地确定地球表面坐标。SHARE Asia 计划的一个特殊的目的是发展一套完整的测量系统,以满足不断进步的环境与地球科学;促进当地的技术升级和建设的能力。
就像WMO CEOP 和UNEP ABC一样,SHARE Asia 气象—气候及大气化学观测站已经成为重要的国际科学计划的一部分。 相似文献
23.
24.
Arsenic concentrations exceeding the U.S. EPA's 10 μg/L standard are common in glacial aquifers in the midwestern United States. Previous studies have indicated that arsenic occurs naturally in these aquifers in association with metal-(hydr)oxides and is released to groundwater under reducing conditions generated by microbial oxidation of organic matter. Despite this delineation of the arsenic source and mechanism of arsenic mobilization, identification of arsenic-impacted aquifers is hindered by the heterogeneous and discontinuous nature of glacial sediments. In much of the Midwest, the hydrostratigraphy of glacial deposits is not sufficiently characterized to predict where elevated arsenic concentrations are likely to occur. This case study from southeast Wisconsin presents a detailed characterization of local stratigraphy, hydrostratigraphy, and geochemistry of the Pleistocene glacial deposits and underlying Silurian dolomite. Analyses of a single core, water chemistry data, and well construction reports enabled identification of two aquifers separated by an organic-rich aquitard. The upper, unconfined aquifer provides potable water, whereas arsenic generally exceeds 10 μg/L in the deeper aquifer. Although coring and detailed hydrostratigraphic characterization are often considered impractical, our results demonstrate that a single core improved interpretation of the complex lithology and hydrostratigraphy. This detailed characterization of hydrostratigraphy facilitated development of well construction guidelines and lays the ground work for further studies of the complex interactions among aquifer sediments, hydrogeology, water chemistry, and microbiology that lead to elevated arsenic in groundwater. 相似文献
25.
Bridging the gap: linking climate-impacts research with adaptation planning and management 总被引:1,自引:0,他引:1
Michael D. Mastrandrea Nicole E. Heller Terry L. Root Stephen H. Schneider 《Climatic change》2010,100(1):87-101
A critical challenge in supporting climate change adaptation is improving the linkage between climate-impacts and vulnerability
research and public and private planning and management decisions. We highlight the need for bottom-up/top-down vulnerability
assessment, bringing together bottom-up knowledge of existing vulnerabilities with top-down climate-impact projections, as
a transparent basis for informing decisions intended to reduce vulnerability. This approach can be used to evaluate the likelihood
of crossing identified thresholds of exposure, and to evaluate alternative adaptation strategies based on their ability to
reduce sensitivity to projected changes in exposure and their robustness across uncertainty in future outcomes. By identifying
thresholds for which adaptive capacity is limited in particular systems, adaptation and mitigation become complements where
the magnitudes of climate change at which such thresholds cluster can help to define mitigation targets. 相似文献
26.
Mysids form a large biomass and mediate the benthic–pelagic coupling of numerous estuaries in southern New Zealand. An intra-annual (2011–2012) field survey in the breeding seasons (i.e. austral spring followed by summer) of mysids Tenagomysis chiltoni and Tenagomysis novaezealandiae, examining the body and brood sizes, was conducted. Samples were collected from six open and eight intermittently open/closed estuaries along the Otago coastline. Brood size of gravid females of T. chiltoni was not significantly related to their body size. Brood size of gravid females of T. novaezealandiae showed a significantly positive relationship with body size in spring but not in summer. It appears that brood size of gravid mysids do not always necessarily depend on body size, but may be influenced by breeding season (e.g. spring) and estuarine typology (e.g. intermittently open/closed). 相似文献
27.
Potential Effects of Global Warming on Waterfowl Populations Breeding in the Northern Great Plains 总被引:4,自引:0,他引:4
Lisa G. Sorenson Richard Goldberg Terry L. Root Michael G. Anderson 《Climatic change》1998,40(2):343-369
The Prairie Pothole Region (PPR) of the Northern Great Plains is the most important breeding area for waterfowl in North America. Historically, the size of breeding duck populations in the PPR has been highly correlated with spring wetland conditions. We show that one indicator of climate conditions, the Palmer Drought Severity Index (PDSI), is strongly correlated with annual counts (from 1955 to 1996) of both May ponds (R2 = 0.72, p < 0.0001) and breeding duck populations (R2 = 0.69, p < 0.0001) in the Northcentral U.S., suggesting the utility of PDSI as an index for climatic factors important to wetlands and ducks. We then use this relationship to project future pond and duck numbers based on PDSI values generated from sensitivity analyses and two general circulation model (GCM) scenarios. We investigate the sensitivity of PDSI to fixed changes in temperature of 0°C, +1.5°C, +2.5°C, and +4.0°C in combination with fixed changes in precipitation of -10%, +0%, +7%, and +15%, changes spanning the range of typically-projected values for this region from human-induced climatic change. Most (11 of 12) increased temperature scenarios tested result in increased drought (due to greater evapotranspiration under warmer temperatures) and declining numbers of both wetlands and ducks. Assuming a doubling of CO2 by 2060, both the equilibrium and transient GCM scenarios we use suggest a major increase in drought conditions. Under these scenarios, Northcentral U.S. breeding duck populations would fluctuate around means of 2.1 or 2.7 million ducks based on the two GCMs, respectively, instead of the present long-term mean of 5.0 million. May pond numbers would fluctuate around means of 0.6 or 0.8 million ponds instead of the present mean of 1.3 million. The results suggest that the ecologically and economically important PPR could be significantly damaged by climate changes typically projected. We make several recommendations for policy and research to help mitigate potential effects. 相似文献
28.
GP. Horedt 《Astrophysics and Space Science》1976,45(2):353-367
In dense interstellar clouds or in the surroundings of just-formed stars, the larger grains form proto-cores by segregating from the gas under the influence of the gravitational field of the cloud during intervals of the order 108 yr.If the mass of the proto-cores is smaller than a certain limit, the object possesses a negligible atmosphere and remains composed mainly of solid grain material. If the mass of the proto-core exceeds the limiting mass, the proto-core can bind around it an atmosphere. When the temperature of the opaque part of the atmosphere is only fractions of a degree above the temperature of the surrounding tenuous gas, gravitational contraction of the opaque part of the atmosphere sets in, forming gaseous objects up to stellar mass range.Binary and multiple systems originate from neighbouring proto-cores, through gravitational contraction of both their separate and common outer atmospheres.Pycnonuclear reactions are not able to prevent a star with mass 0.08M
from cooling to the black dwarf stadium. 相似文献
29.
A XANES and Raman investigation of sulfur speciation and structural order in Murchison and Allende meteorites
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Insoluble organic matter (IOM) and hydrothermally treated IOM extracted from two carbonaceous chondrites, Murchison and Allende, was studied using sulfur K‐edge XANES (X‐ray absorption near edge structure) and μ‐Raman spectroscopy, with the aim to understand their IOM's sulfur speciation and structural order, and how aqueous alteration or thermal metamorphism may have transformed these materials. We found that the sulfur‐functional group chemistry of both the Murchison IOM and hydrothermally treated IOM samples have a large chemical variability ranging from oxidation states of S?2 to S+6, and exhibit a transformation in their oxidation state after the hydrothermal treatment (HT) to produce thiophenes and thiol compounds. Sulfoxide and sulfite peaks are also present in Murchison. Sulfates considered intrinsic to Murchison are most likely preaccretionary in nature, and not a result of reactions with water at high temperatures on the asteroid parent body. We argue that the reduced sulfides may have formed in the CM parent body, while the thiophenes and thiol compounds are a result of the HT. Micro‐Raman spectra show the presence of aliphatic and aromatic moieties in Murchison's material as observed previously, which exhibits no change after HT. Because the Murchison IOM was modified, as seen by XANES analysis, absence of a change observed using micro‐Raman indicated that although the alkyl carbons of IOM were cleaved, the aromatic network was not largely modified after HT. By contrast, Allende IOM contains primarily disulfide and elemental sulfur, no organic sulfur, and shows no transformation after HT. This nontransformation of Allende IOM after HT would indicate that parent body alteration of sulfide to sulfate is not feasible up to temperatures of 300°C. The reduced sulfur products indicate extreme secondary chemical processing from the precursor compounds in its parent body at temperatures as high as 624°C, as estimated from μ‐Raman D band parameters. The Raman parameters in Allende IOM that was interpreted in terms of amorphous carbon with regions of large clusters of benzene rings, was transformed after the HT to those with fewer benzene rings. 相似文献
30.
Resource estimation from historical data: Mercury, a test case 总被引:4,自引:0,他引:4
A simple technique based on historical records of tonnage and grade of ore produced provides a means for calculating how much of a mineral product will be available in the future at various average grades. Estimates made on this basis are independent of geologic considerations or changing economic and political factors, although they are based on mining history, which was largely determined by these factors. The relatively minor element, mercury, was used for the test case reported here, but the method has been found applicable to forecasts of resources for other mineral products. Mercury resources available in ore in which the average grade is as low as 0.1% are estimated to be 53 ×10
6
kg (1.5 ×10
6
flasks) for the United States and 1551 ×10
6
kg (45 ×10
6
flasks) for the world; this amount is more than adequate to meet predicted demand to the year 2000. The expectable price of mercury in 1978 dollars at this 0.1% grade is projected to be $58.75 per kg ($2,025 per flask), but at a 10% annual inflation rate, it would be more than $12,000 per flask. To satisfy just the projected U.S. demand for mercury by 2000, the price is calculated to be $48.96 per kg ($1,688 per flask) in 1978 dollars at an average annual grade of 0.12%. 相似文献