Groundwater Quality Impacts from a Full‐Scale Integrated Constructed Wetland     

Mawuli Dzakpasu  Miklas Scholz  Rory Harrington  Valerie McCarthy  Siobhán Jordan 《Ground Water Monitoring & Remediation》2014,34(3):51-64

The concept of integrated constructed wetlands (ICW) promotes in‐situ soils to construct and line wetland cells. The integrity of soil material, however, may provide a potential pathway for contaminants to flow into the underlying groundwater. This study assessed the extent of groundwater quality deterioration due to the establishment of a full‐scale ICW system treating domestic wastewater in Ireland. The ICW is located at Glaslough in Co. Monaghan, Ireland. It consists of two sedimentation ponds and a sequence of five shallow vegetated wetland cells. The ICW cells were lined with 500‐mm thick local subsoil material, which comprised a mixture of alluvium, organic soils, tills, and gravel. Groundwater samples and head data were collected from eight piezometers, which were installed around the ICW cells. The groundwater and wetland water samples were analysed for water quality parameters such as bulk organic matter, nutrients, and pathogens. Overall, the quality of groundwater underlying the ICW system recorded some contamination with bulk organic matter and some inorganic nutrients. Significantly higher contaminant concentrations were recorded in monitoring wells upgradient and near to the distal wetland cells than downgradient ones, which were near to the proximal cells. For the downgradient piezometers, concentrations seldomly exceeded the natural background levels. Detailed analyses through the application of chemometrics models indicated that the source of contamination was largely of geogenic origin. Findings suggest that ICW systems pose a minimal risk to the groundwater quality; the greatest risk was associated with the distal wetland cells.  相似文献   

Multi-century variability in the Pacific North American circulation pattern reconstructed from tree rings     

Valerie Trouet  Alan H. Taylor 《Climate Dynamics》2010,35(6):953-963

We here present a reconstruction (1725–1999) of the winter Pacific North American (PNA) pattern based on three winter climate sensitive tree ring records from the western USA. Positive PNA phases in our record are associated with warm phases of ENSO and PDO and the reorganization of the PNA pattern towards a positive mode is strongest when ENSO and PDO are in phase. Regime shifts in our PNA record correspond to climatic shifts in other proxies of Pacific climate variability, including two well-documented shifts in the instrumental period (1976 and 1923). The correspondence breaks down in the early 19th century, when our record shows a prolonged period of positive PNA, with a peak in 1800–1820. This period corresponds to a period of low solar activity (Dalton Minimum), suggesting a ‘positive PNA like’ response to decreased solar irradiance. The distinct 30-year periodicity that dominates the PNA reconstruction in the 18th century and again from 1875 onwards is disrupted during this period.  相似文献   

EXOTIME: searching for planets around pulsating subdwarf B stars     

Sonja Schuh  Roberto Silvotti  Ronny Lutz  Björn Loeptien  Elizabeth M. Green  Roy H. Østensen  Silvio Leccia  Seung-Lee Kim  Gilles Fontaine  Stéphane Charpinet  Myriam Francœur  Suzanna Randall  Cristina Rodríguez-López  Valerie van Grootel  Andrew P. Odell  Margit Paparó  Zsófia Bognár  Péter Pápics  Thorsten Nagel  Benjamin Beeck  Markus Hundertmark  Thorsten Stahn  Stefan Dreizler  Frederic V. Hessman  Massimo Dall’Ora  Dario Mancini  Fausto Cortecchia  Serena Benatti  Riccardo Claudi  Rimvydas Janulis 《Astrophysics and Space Science》2010,329(1-2):231-242

In 2007, a companion with planetary mass was found around the pulsating subdwarf B star V391 Pegasi with the timing method, indicating that a previously undiscovered population of substellar companions to apparently single subdwarf B stars might exist. Following this serendipitous discovery, the EXOTIME (http://www.na.astro.it/~silvotti/exotime/) monitoring program has been set up to follow the pulsations of a number of selected rapidly pulsating subdwarf B stars on time scales of several years with two immediate observational goals:

1. determine $\dot{P}$ of the pulsational periods P
2. search for signatures of substellar companions in O–C residuals due to periodic light travel time variations, which would be tracking the central star’s companion-induced wobble around the centre of mass

These sets of data should therefore, at the same time, on the one hand be useful to provide extra constraints for classical asteroseismological exercises from the $\dot{P}$ (comparison with “local” evolutionary models), and on the other hand allow one to investigate the preceding evolution of a target in terms of possible “binary” evolution by extending the otherwise unsuccessful search for companions to potentially very low masses. While timing pulsations may be an observationally expensive method to search for companions, it samples a different range of orbital parameters, inaccessible through orbital photometric effects or the radial velocity method: the latter favours massive close-in companions, whereas the timing method becomes increasingly more sensitive toward wider separations. In this paper we report on the status of the on-going observations and coherence analysis for two of the currently five targets, revealing very well-behaved pulsational characteristics in HS?0444+0458, while showing HS?0702+6043 to be more complex than previously thought.  相似文献   

GIS-based hydrogeological databases and groundwater modelling   总被引：4，自引：2，他引：2  

Radu Gogu  Guy Carabin  Vincent Hallet  Valerie Peters  Alain Dassargues 《Hydrogeology Journal》2001,9(6):555-569

Reliability and validity of groundwater analysis strongly depend on the availability of large volumes of high-quality data. Putting all data into a coherent and logical structure supported by a computing environment helps ensure validity and availability and provides a powerful tool for hydrogeological studies. A hydrogeological geographic information system (GIS) database that offers facilities for groundwater-vulnerability analysis and hydrogeological modelling has been designed in Belgium for the Walloon region. Data from five river basins, chosen for their contrasting hydrogeological characteristics, have been included in the database, and a set of applications that have been developed now allow further advances. Interest is growing in the potential for integrating GIS technology and groundwater simulation models. A "loose-coupling" tool was created between the spatial-database scheme and the groundwater numerical model interface GMS (Groundwater Modelling System). Following time and spatial queries, the hydrogeological data stored in the database can be easily used within different groundwater numerical models. Electronic Publication  相似文献   

Spatial Mismatch and Employment in a Decade of Restructuring*     

Sara McLafferty  Valerie Preston 《The Professional geographer》1996,48(4):420-431

Spatial barriers to employment limit women's job opportunities, but their effects differ among racial/ethnic minority groups. This study evaluates the degree of spatial mismatch for minority women and men by comparing the commuting times of African American, Latino, and white workers in the New York metropolitan region. Using Public Use Microdata for 1980 and 1990, we perform a partial decomposition analysis to assess the role of spatial mismatch in lengthening commuting times for minority workers. The results show that African American men and women living in the center of the region have poorer spatial access to employment than their white counterparts. In the suburbs, African American women and Latinas suffer no spatial mismatch; rather, their longer commuting times reflect greater reliance on mass transit. Comparison with 1980 findings reveals little change in spatial mismatch over time despite significant economic and social restructuring in the 1980s. Spatial barriers still limit employment prospects for the majority of minority women living at the core of the region.  相似文献   

Application of Markov analysis to the Banff Formation (Mississippian), Alberta   总被引：1，自引：0，他引：1  

Valerie G. Ethier 《Mathematical Geosciences》1975,7(1):47-61

The Banff Formation (Mississippian) is a sequence of limestone and shale exposed in the southern Canadian Rocky Mountains and underlying the adjacent plains. It was chosen as a vehicle to evaluate Markov-inspired techniques in sedimentary sequences where repetition of rock types is typical but a pattern of cyclicity is not obvious. Distributions of rock-unit thickness in two outcrop sections of the Banff Formation are not all exponential, therefore a one-step Markov model using an equal observational interval is not valid. Memory is indicated by the embedded-chain model. The most likely pattern of recurrence is delineated; shale is the most independent lithologic type and therefore the initial lithology in any ideal pattern. Neither factoring nor powering a probability matrix for the Banff Formation revealed geological cyclicity as defined by W. Schwarzacher. Several problems limit the application of Markov models to sedimentary sequences. Statistical validity requires a minimum number of observations, and in the attainment of a sound statistical basis, geological pertinence may be seriously reduced. Treatment of the probability matrix, by principal components analysis or by powering, yields an exacting criterion for cyclicity.  相似文献   

Reconstruction of Summer Temperatures in Interior Alaska from Tree-Ring Proxies: Evidence for Changing Synoptic Climate Regimes     

Valerie A. Barber  Glenn Patrick Juday  Bruce P. Finney  Martin Wilmking 《Climatic change》2004,63(1-2):91-120

Maximum latewood density and δ ¹³C discrimination of Interior Alaska white spruce were used to reconstruct summer (May through August) temperature at Fairbanks for the period 1800–1996, one of the first high-resolution reconstructions for this region. This combination of latewood density and δ ¹³C discrimination explains 59.9% of the variance in summer temperature during the period of record 1906–1996. The 200-yr. reconstruction is characterized by 7 decadal-scale regimes. Regime changes are indicated at 1816, 1834, 1879, 1916, 1937, and 1974, are abrupt, and appear to be the result of synoptic scale climate changes. The mean of summer temperature for the period of reconstruction (1800–1996) was 13.49 °C. During the period of instrument record (1903–1996) the mean of summer temperature was 13.31 °C for both the reconstruction and the recorded data. The coldest interval was 1916–1937 (12.62 ° C) and the warmest was 1974–1996 (14.23 °C) for the recorded data. The reconstruction differs from records of northern hemisphere temperatures over this period, especially because of Interior Alaska warm periods reconstructed from 1834 to 1851 (14.24 °C) and from 1862 to 1879 (14.19 °C) and because of the cool period in the early part of the 20th century (1917–1974). We show additional tree ring data that support our reconstruction of these warm periods. Alternate hypotheses involving autogenic effect of tree growth on the site, altered tree sensitivity, or novel combinations of temperature and precipitation were explored and while they cannot be ruled out as contributors to the anomalously warm 19th century reconstruction, they were not supported by available data. White spruce radial growth is highly correlated with reconstructed summer temperature, and temperature appears to be a reliable index of carbon uptake in this system.  相似文献   

Mantle dynamics and geoid Green functions     

Valerie Corrieu  Catherine Thoraval  Yanick Ricard 《Geophysical Journal International》1995,120(2):516-523

  相似文献   

Placing gender/making policy: an introduction     

Fran Klodawsky  Valerie Preston 《GeoJournal》2006,65(4):243-247

  相似文献   

Diagnostic study and modeling of the annual positive water temperature onset     

Anik Daigle  Andr St-Hilaire  Valrie Ouellet  Julie Corriveau  Taha B.M.J. Ouarda  Laurent Bilodeau 《Journal of Hydrology》2009,370(1-4):29-38

A data-driven model is designed using artificial neural networks (ANN) to predict the average onset for the annual water temperature cycle of North-American streams. The data base is composed of daily water temperature time series recorded at 48 hydrometric stations in Québec (Canada) and northern US, as well as the geographic and physiographic variables extracted from the 48 associated drainage basins. The impact of individual and combined drainage area characteristics on the stream annual temperature cycle starting date is investigated by testing different combinations of input variables. The best model allows to predict the average temperature onset for a site, given its geographical coordinates and vegetation and lake coverage characteristics, with a root mean square error (RMSE) of 5.6 days. The best ANN model was compared favourably with parametric approaches.  相似文献