Ground Water Discharge of Agricultural Pesticides and Nutrients to Estuarine Surface Water   总被引：2，自引：0，他引：2  

Daniel L. Gallagher  rea M. Dietrich  William G. Reay  Mary C. Hayes  George M. Simmons Jr. 《Ground Water Monitoring & Remediation》1996,16(1):118-129

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Recent chronologies for tree rings and terrestrial archives using C bomb fallout history     

E.J. McGee  D. Gallagher  M. Baillie  S.M. Keogh 《Geochimica et cosmochimica acta》2004,68(11):2509-2516

Tree rings representing the period from the mid-1950s up to 2001 were studied as part of an investigation of anthropogenic radionuclide input to terrestrial systems. A live specimen of Pinus sylvestris from the east coast of Ireland was felled, sampled and analysed for comparison with a similar tree felled close to the Atlantic seaboard on the west coast of Ireland. Data for the tree ring sequences were examined relative to the radionuclide content of peat profiles sampled in close proximity to the locations of the studied Pine trees.The data indicate that ¹⁴C concentrations in tree ring sequences from the east and west coasts of Ireland are virtually identical. The sequences show maximum ¹⁴C concentrations (185 and 189 pMC at east and west coast sites, respectively) that correspond closely with published data for atmospheric levels during the height of the nuclear weapons test period (1945-1980). The tree ring count for the specimen from the east coast places the ¹⁴C peak precisely at 1964, the year following the known peak in atmospheric concentrations due to above ground testing of nuclear weapons. However, ¹⁴C data show that simple ring counting of the west coast tree did not provide an accurate chronology. The data demonstrate the importance of applying dendrodating techniques using replicated site chronologies, and the value of the ¹⁴C bomb fallout curve for the construction of recent chronologies. Data show no evidence of enhanced uptake at the east coast that might suggest incorporation of output from the Sellafield nuclear complex or from the release of radioactivity resulting from an accidental fire at the plant in 1957.  相似文献   

Some observations of airflow over a large hill of moderate slope     

M. W. Gallagher  T. W. Choularton  M. K. Hill 《Boundary-Layer Meteorology》1988,42(3):229-250

Measurements are presented of mean windspeed and turbulence over Great Dun Fell, which is rather larger than hills investigated in the past, viz., 847 m high, which is comparable to the boundary-layer depth. The Fell is well suited for study, being covered by rough grass with no trees and few other obstructions. It was found that the speed-up of the wind is dominated by the elevated stratification and generally agrees closely with the predictions of the model of Carruthers and Choularton (1982) except when the flow is blocked. On the hill summit, the turbulence is approximately in local equilibrium in at least the lowest 10 m and the turbulence measurements are similar to those obtained within the inner layer at other sites. The transverse and longitudinal components show spectral lags at wavelengths greater than 30 m. This suggests an inner-layer depth of about 1/3 that predicted by Jackson and Hunt (1975). At reduced frequencies (>0.1), a recovery in spectral energy is observed due to gravity wave activity. A large variation in the streamline tilt at the summit is observed depending on whether the airflow regime is supercritical or subcritical.  相似文献   

Tourmaline in the central Swedish ore district   总被引：2，自引：0，他引：2  

R. H. Hellingwerf  K. Gatedal  V. Gallagher  J. H. Baker 《Mineralium Deposita》1994,29(2):189-205

More than 40 recently discovered tourmaline occurrences have been investigated in the Mid-Proterozoic Bergslagen ore district of central Sweden. Some are spatially associated with ores, others with zones of leaching, remobilization and migmatization. Among the tourmaline-bearing ore deposits are the Dammberg ZnPb-Fe sulphide deposit, the Sala Pb-Zn-Ag deposit, the Dalkarlsberg, Pershyttan and Håksberg Fe oxide deposits, the Leja Cu deposit, and the Zinkgruvan Zn-Pb-Ag deposit. Tourmaline has been recorded a) as tourmalinites and tourmaline-bearing chemical sediments; b) in tourmaline-bearing skarns; c) in tourmaline-quartz veins; d) as disseminations along the foliation in schists; e) in tourmaline pegmatites; f) in tourmalinized haloes in metavolcanites along tourmaline pegmatites; and g) in late joints. Tourmalinites, tourmaline-bearing chemical sediments and tourmaline-bearing skarns are spatially associated with sulphide and oxide mineralizations. The dravite components in these tourmalines are proportional to the size of Zn-Pb sulphide mineralizations. Tourmalines from quartz veins close to and within ore deposits contain high Zr and Cr contents. With increasing distance away from these deposits, the Zr and Cr contents fall significantly. Tourmalines from pegmatites have inherited a number of trace element enrichments through partial melting and assimilation of volcaniclastic sediments into granitic melts. Despite magmatic homogenization, Zn contents in these tourmalines reflect the proximity of Zn-Pb-sulphide deposits, decreasing away from them. Tourmalines from late joints with Zn contents above the 100 ppm level are also indicative for the proximity of Zn-Pb sulphide mineralizations. Thus, some trace elements in these tourmalines may represent suitable exploration tools.  相似文献   

Facets of hydrology II: John C. Rodda (editor). Wiley, New York, N.Y., 1985. xvi + 447 pp., £ stg.38.00 (hardback)     

R.E. Gallagher 《Journal of Hydrology》1987,90(3-4):360-362

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Bayesian Mixture Modelling in Geochronology via Markov Chain Monte Carlo     

Ajay Jasra  David A. Stephens  Kerry Gallagher  Christopher C. Holmes 《Mathematical Geology》2006,38(3):269-300

In this paper we develop a generalized statistical methodology for characterizing geochronological data, represented by a distribution of single mineral ages. The main characteristics of such data are the heterogeneity and error associated with its collection. The former property means that mixture models are often appropriate for their analysis, in order to identify discrete age components in the overall distribution. We demonstrate that current methods (e.g., Sambridge and Compston, 1994) for analyzing such problems are not always suitable due to the restriction of the class of component densities that may be fitted to the data. This is of importance, when modelling geochronological data, as it is often the case that skewed and heavy tailed distributions will fit the data well. We concentrate on developing (Bayesian) mixture models with flexibility in the class of component densities, using Markov chain Monte Carlo (MCMC) methods to fit the models. Our method allows us to use any component density to fit the data, as well as returning a probability distribution for the number of components. Furthermore, rather than dealing with the observed ages, as in previous approaches, we make the inferences of components from the “true” ages, i.e., the ages had we been able to observe them without measurement error. We demonstrate our approach on two data sets: uranium-lead (U-Pb) zircon ages from the Khorat basin of northern Thailand and the Carrickalinga Head formation of southern Australia.  相似文献   

Trans-dimensional inverse problems, model comparison and the evidence   总被引：1，自引：0，他引：1  

M. Sambridge  K. Gallagher  A. Jackson  P. Rickwood 《Geophysical Journal International》2006,167(2):528-542

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Rhizome growth dynamics of native and exotic haplotypes ofPhragmites australis (Common reed)     

Michael T. League  Erin P. Colbert  Denise M. Seliskar  John L. Gallagher 《Estuaries and Coasts》2006,29(2):269-276

Phragmites australis (common reed), a clonal grass, has expanded from a minor component of the mid-Atlantic wetlands to a dominant species. It has been suggested that invasive populations ofPhragmites are an exotic haplotype responsible for the dramatic increase in the distribution of the species. We used field observations and measurements and a greenhouse assay to compare native (haplotype F) and exotic (haplotype M) populations, growing adjacent to one another in a brackish marsh near Odessa, Delaware. In the marsh, shoots of the exotic strain emerged from the rhizomes earlier than those of the native and by March there was an order of magnitude more new shoots of the exotic strain than the native. In August, the exotic strain was 30% taller than the native, had twice the leaf biomass, and twice the total biomass. Nine of ten morphological and biomass characteristics measured differed significantly between the native and exotic strains. A greenhouse assay was conducted by planting rhizomes collected in March in shallow trays and growing them for 70 d followed by shoot harvest (Harvest 1). Rhizomes were measured, replanted, and grown for 35 d after which time they were measured and shoots were harvested (Harvest 2). At Harvest 1, shoot height was approximately 80% greater in the exotic strain, shoot biomass was three times higher, aboveground to belowground biomass ratio was twice as high, and rhizome internode length was 50% greater in the exotic strain than the native. These traits, in addition to number of shoots, were also greater in the exotic strain at Harvest 2. The number of rhizome buds at Harvest 1 was three times greater in the native than in the exotic strain. The greater number of rhizome buds in the native would seem to be an advantage, but it did not result in more shoot production. Buds were maintained in an inactive state that does not allow this strain to compete well in a wetland environment inhabited by a more efficient spreader. The earlier emergence of new shoots from the rhizomes, the greater aboveground structure, the greater rhizome internode length, and the quick transition of rhizome buds to shoot or rhizome explain in part the exotic strain's advantage over the native and the mechanisms for its invasive nature.  相似文献   

Long-Term Tracking of Corotating Density Structures Using Heliospheric Imaging     

I. Plotnikov  A. P. Rouillard  J. A. Davies  V. Bothmer  J. P. Eastwood  P. Gallagher  R. A. Harrison  E. Kilpua  C. Möstl  C. H. Perry  L. Rodriguez  B. Lavraud  V. Génot  R. F. Pinto  E. Sanchez-Diaz 《Solar physics》2016,291(6):1853-1875

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Automatic Detection of Magnetic δ in Sunspot Groups     

Sreejith Padinhatteeri  Paul A. Higgins  D. Shaun Bloomfield  Peter T. Gallagher 《Solar physics》2016,291(1):41-53

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