87Sr/86Sr ratio: a natural tracer to monitor groundwater flow paths during artificial recharge in the Bangkok area, Thailand     

Janina S. Klaus  Bent T. Hansen  Somkid Buapeng 《Hydrogeology Journal》2007,15(4):745-758

The aquifer system in the Thon Buri sedimentary basin below the deltaic flood plain of the Chao Phraya River, central Thailand, has been exploited for public water supply for the capital Bangkok since the early 1920s. Groundwater withdrawal, currently 1.4 million m³/d, has resulted in a maximum decline in hydraulic head of up to 40 m. This has induced land subsidence of as much as 1.7 m (1940–1992) in the eastern suburbs of the metropolis. Artificial injection of purified water within an area-wide network of recharge wells could constitute a remedy to slow the water level depression within the sedimentary basin, and thus the subsidence. This requires a prior shutdown of water withdrawal. The flow paths of the injected water can be traced by changes in the ⁸⁷Sr/⁸⁶Sr ratio of the groundwater and injected water mixture within the three main aquifers in the basin that are used for public supply. The ratios, monitored at five monitoring stations within the cone of depression, have been constant over 3 years. Injection of the calculated cone volume of 5.2?×?10⁹ m³ would take at least 10 years, depending on the injection pressure and the number and position of wells.  相似文献   

Whole-rock, Phosphate, and Silicate Compositional Trends across an Amphibolite- to Granulite-facies Transition, Tamil Nadu, India   总被引：2，自引：0，他引：2  

Hansen  Edward C.; Harlov  Daniel E. 《Journal of Petrology》2007,48(9):1641-1680

Chemical trends from north (amphibolite facies) to south (granulitefacies) along a 95 km traverse in Tamil Nadu, Southern India,include: whole-rock depletion of Rb, Cs, Th and U, enrichmentin Ti and F, and depletion in Fe and Mn in biotite and amphibole;increases in Al and decreases in Mn in orthopyroxene; enrichmentof fluorapatite in F. K-feldspar blebs are widespread alongquartz–plagioclase grain boundaries, and could indicateeither partial melting or metasomatism. In the northernmostportion of the traverse the principal rare earth element (REE)-bearingminerals are allanite and titanite. South of a clinopyroxeneisograd, monazite grains independent of fluorapatite are themajor REE- and Th-bearing phase. Further south independent monaziteis rare but Th-free monazite inclusions are common in fluorapatite.During prograde metamorphism, independent monazite was replacedby REE-rich fluorapatite in which the monazite inclusions laterformed. The loss of independent monazite was accompanied bya loss of whole-rock Th and possibly a small depletion in lightREE. Most mineralogical features along the traverse can be accountedfor by progressive dehydration and oxidation reactions. Trace-elementdepletion is best explained by the action of an externally derivedlow H₂O activity brine migrating from a source at greater depth,possibly preceded or accompanied by partial melting. KEY WORDS: granulite facies; charnockite; metasomatism; Archean; Tamil Nadu, India; fluorapatite; monazite; allanite; titanite; biotite  相似文献   

Long-term comparisons of net radiation calculation schemes   总被引：1，自引：0，他引：1  

J. H. Kjaersgaard  R. H. Cuenca  F. L. Plauborg  S. Hansen 《Boundary-Layer Meteorology》2007,123(3):417-431

Six commonly used models for calculating daily net radiation were tested against measured net radiation. Meteorological data from 32 and 7 consecutive years obtained at two temperate sites were used. The extensive duration of the datasets ensured that all weather conditions and extreme events were captured. A set of statistical procedures was used to evaluate the performance of the models. The mean bias errors ranged from 0.0 W m⁻² to 24.8 W m⁻² and 0.1–24.7 W m⁻² and root mean square error from 11.0 W m⁻² to 28.1 W m⁻² and 10.0–27.9 W m⁻² at the two sites respectively, for days without snow cover on the ground. The best agreement was found when locally calibrated model coefficients were used. Only negligible differences in model performances were found between the two sites and the differences were lower than the inaccuracies of the net radiation instruments used. Including days with snow cover in the analysis lead to a slight increase in the bias and scatter of the predictions. Model performances were in general better during summertime than wintertime. Altered albedo values during winter caused by generally low sun angles were likely the cause of this. Analysis showed that at least 5 years of data were needed to obtain stable calibration coefficients for local calibration of the models. Based on the results from this study, and due to their physical background, two physical based models were recommended for calculating daily values of net radiation under temperate climate regimes. A simple adjustment of the calibration coefficients based on climate regime was suggested for these models.  相似文献   

Progress in NTHMP Hazard Assessment     

Frank I. González  Vasily V. Titov  Harold O. Mofjeld  Angie J. Venturato  R. Scott Simmons  Roger Hansen  Rodney Combellick  Richard K. Eisner  Don F. Hoirup  Brian S. Yanagi  Sterling Yong  Mark Darienzo  George R. Priest  George L. Crawford  Timothy J. Walsh 《Natural Hazards》2005,35(1):89-110

The Hazard Assessment component of the U.S. National Tsunami Hazard Mitigation Program has completed 22 modeling efforts covering 113 coastal communities with an estimated population of 1.2 million residents that are at risk. Twenty-three evacuation maps have also been completed. Important improvements in organizational structure have been made with the addition of two State geotechnical agency representatives to Steering Group membership, and progress has been made on other improvements suggested by program reviewers.  相似文献   

Observations of coronal disturbances from 1 to 9 R ⊙     

Stewart  R. T.  McCabe  Marie K.  Koomen  M. J.  Hansen  R. T.  Dulk  G. A. 《Solar physics》1974,36(1):203-217

Solar Physics - Hα, white-light and radio observations of a coronal disturbance on 1973 January 11 commencing at about 00h36m UT show that a piston-driven shock wave propagated outwards...  相似文献   

In-situ registration of oxygen utilization at sediment-water interfaces     

H.P. Hansen  K. Grasshoff  J. Petersen 《Marine Chemistry》1980,10(1):47-54

A polyacrylic dome was anchored over natural sediments, enclosing a water volume of 0.125 m³ over an area of 0.45 m² of sediment. A vertical convection was produced in the dome, by means of a small pump, to prevent formation of gradients. Oxygen partial pressure and temperature were measured at 20-min intervals by an automatic data system and stored on magnetic tape in digitized form. After some days the system was recovered. The data were read by a microprocessor system, interpreted, listed and plotted against time. Chemical and hydrographic data, from a sample taken at the location of the experiment at the instant it was started, were used as calibration data to calculate oxygen utilization of the sediments in the Kiel Bight.  相似文献   

Observations of coronal disturbances from 1 to 9 R ⊙     

Stewart  R. T.  Howard  R. A.  Hansen  F.  Gergely  T.  Kundu  M. 《Solar physics》1974,36(1):219-231

Observations of a coronal disturbance on 1973 January 11 commencing at 18^h01^m UT are described. The event is homologous with an earlier disturbance from the same region of the corona. The observations suggest that a cloud of coronal gas containing 4 × 10³⁹ electrons propagated outwards to 5 R behind a piston-driven shock wave travelling at a velocity of 800 to 1200 km s^–1.On leave from Division of Radiophysics, CSIRO, Sydney, Australia.  相似文献   

Equatorial coronal arches and geomagnetic disturbance     

C. Sawyer  Shirley F. Hansen 《Solar physics》1972,26(2):370-377

Central-meridian passage of coronal equatorial arches is followed, statistically, after about 7 days by geomagnetic disturbance. Sector-boundary crossings at Earth are most likely to occur 5 days after arch CMP, while metric noise sources cluster at the location of the arches. This agrees with the location of the noise sources relative to sector boundaries described by Sakurai and Stone (1971), rather than with that found by Martres et al. (1970) for 1964 and 1966, and may indicate evolution of the relation between coronal and interplanetary structure. We looked for, but did not find, clustering of coronal arches at a particular phase of the Olsen rotation scheme.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

On the spread function for stray light     

Truls Hansen 《Solar physics》1973,32(2):505-506

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Editorial     

Jens Christian Hansen 《GeoJournal》1977,1(1):5-6

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