Groot M.H.M.,University of Amsterdam |
van der Plicht J.,University of Groningen |
van der Plicht J.,Leiden University |
Hooghiemstra H.,University of Amsterdam |
And 2 more authors.
Quaternary Geochronology | Year: 2014
Challenges and pitfalls for developing age models for long lacustrine sedimentary records are discussed and a comparison is made between radiocarbon dating, visual curve matching, and frequency analysis in the depth domain in combination with cyclostratigraphy. A core section of the high resolution 284-ka long temperature record developed from Lake Fúquene in the Northern Andes is used to explore four different age models (a-d). (a) A model based on 46 AMS 14C dates of bulk sediment is hampered by low concentrations of organic carbon. (b) A model based on the comparison of the radiocarbon dated pollen record to the well-established record from Cariaco Basin using curve matching and visual tie points. Forthe upper 26m of the core this approach yields an age interval of 28-59.5ka. (c) Another age modelis based on curve matching and the Intcal09 radiocarbon calibration curve, yielding an age range of 22.5-80.4ka for the same core interval. (d) Finally, a model is developed based on spectral analysis in the depth domain of the temperature-related altitudinal migrations of the upper forest line. This method identifies periodicities without a pre-conceived idea of age. The main frequency of 9.07m appears to reflect the 41-kyr orbital signal of obliquity, which is tuned to the filtered 41-kyr temperature signal from the well-constrained LR04 marine benthic ∂18O stack record (Lisiecki and Raymo, 2005). Using this last age-modelling approach, the upper 26m of core Fq-9C yields a temporal interval of 27-133ka. Problems arising from radiocarbon dating carbon poor sediments from a large lake are addressed and the visual curve matching approach is compared to the analysis of cyclic changes in sediment records in developing an age model. We conclude that the frequency analysis and cyclostratigraphy model is the most reliable one of the four approaches. These results show that cyclostratigraphy may provide a useful method for developing an age model for long terrestrial records including multiple orbital cycles. © 2014 Elsevier B.V.
Garre S.,Earth and Environmental science |
Garre S.,University of Liege |
Coteur I.,Earth and Environmental science |
Wongleecharoen C.,University of Hohenheim |
And 3 more authors.
Vadose Zone Journal | Year: 2013
Electrical resistivity tomography can be used to monitor soil moisture depletion under field conditions and with multiple plants. We showed that even though there are limitations arising from soil heterogeneity and dry measurement conditions, important knowledge about spatial and temporal patterns of water depletion on can be obtained. Agriculture on shallow or steep soils in the humid tropics often leads to low resource use efficiency. Contour hedgerow intercropping systems have been proposed to reduce run-off and control soil erosion. However, competition for water and nutrients between crops and associated hedgerows may reduce the overall performance of contour hedgerow systems. Electrical resistivity tomography (ERT) is a valuable technique used to assess the distribution and dynamics of soil moisture noninvasively. In this study, we demonstrated its potential to measure soil water depletion in the field in distinct cropping patterns in Ratchaburi province, Thailand. The measurements showed that the soils of our experimental plots were very heterogeneous both along the slope as with depth. This observation highlighted some constraints of the ERT method for soil moisture monitoring in the field, such as the difficulty of defining a relationship between electrical conductivity and soil moisture in very heterogeneous soils. Nevertheless, spatial analysis of the data revealed contrasting water depletion patterns under monocropping and intercropping systems. In this way, ERT provides access to information about the vadose zone moisture dynamics that would be unavailable with classical soil moisture measurements. © Soil Science Society of America, 5585 Guilford Rd., Madison, WI 53711 USA. All rights reserved.
Garre S.,Earth and Environmental science |
Garre S.,University of Liege |
Gunther T.,Leibniz Institute for Applied Geophysics |
Diels J.,Earth and Environmental science |
Vanderborght J.,Julich Research Center
Vadose Zone Journal | Year: 2012
Contour hedgerow intercropping systems have been proposed as an alternative to traditional agricultural practice with a single crop, as they are effective in reducing run-offand soil ero- sion. However, competition for water and nutrients between crops and associated hedgerows may reduce the overall performance of these systems. To get a more detailed understanding of the competition for water, spatially resolved monitoring of soil water contents in the soil- plant-atmosphere system is necessary. Electrical resistivity tomography (ERT) is potentially a valuable technique to monitor changes in soil moisture in space and time. In this study, the performance of different ERT electrode arrays to detect the soil moisture dynamics in a mono- and an intercropping system was tested. Their performance was analyzed based on a synthetic study using geophysical measures, such as data recovery and resolution, and using spatial statistics of retrieved water content, such as an adjusted coefficient of variation and semivariances. The synthetic ERT measurements detected differences between the cropping systems and retrieved spatial structure of the soil moisture distribution, but the variance and semivariance were underestimated. Sharp water content contrasts between horizons or in the neighborhood of a root water uptake bulb were smoothened. The addition of electrodes deeper in the soil improved the performance, but sometimes only marginally. ERT is there- fore a valuable tool for soil moisture monitoring in the field under different cropping systems if an electrode array is used which can resolve the patierns expected to be present in the medium. The use of spatial statistics allowed to not only identify the overall model recovery, but also to quantify the recovery of spatial structures. © Soil Science Society of America.
Rollinson H.,Earth and Environmental science |
Adetunji J.,Earth and Environmental science |
Greenwood M.,University of Derby
Mercian Geologist | Year: 2012
We report the results of a pilot study, carried out at the University of Derby during 2010 on the nature of the inorganic particulate matter in the air in west Derby. We have found three chemically distinct groups of particles. 1 : Sulphates, including Ca-sulphates (Gypsum), Na-sulphates and mixed grains in which sulphate has nucleated on a silicate host, which reflect a combination of anthropogenic and natural processes; the sulphate may be derived from industrial areas around the Bristol Channel or more locally from the A38 road adjacent to the sampling site. 2: Phosphate-silicate compounds that may be derived from fertilisers or from the local crematorium. 3: A variety of silicates, including quartz and feldspar, of natural origin but not necessarily of local provenance, and also an unusual anthropogenic iron-rich silicate. We conclude from a study of the measured compositions, grain shape and grain size that they are not harmful to human health. © 2012 East Midlands Geological Society.
Vesselinov V.V.,Earth and Environmental science |
Vesselinov V.V.,Los Alamos National Laboratory |
O'Malley D.,Earth and Environmental science |
Katzman D.,Los Alamos National Laboratory
Vulnerability, Uncertainty, and Risk: Quantification, Mitigation, and Management - Proceedings of the 2nd International Conference on Vulnerability and Risk Analysis and Management, ICVRAM 2014 and the 6th International Symposium on Uncertainty Modeling and Analysis, ISUMA 2014 | Year: 2014
In contrast to many other engineering fields, the uncertainties in subsurface processes (e.g., fluid flow and contaminant transport in aquifers) and their parameters are notoriously difficult to observe, measure, and characterize. This causes severe uncertainties that need to be addressed in any decision analysis related to optimal management and remediation of groundwater contamination sites. Furthermore, decision analyses typically rely heavily on complex data analyses and/or model predictions, which are often poorly constrained, as well. Recently, we have developed a model-driven decision support framework (called MADS; http://mads.lanl.gov) for the management and remediation of subsurface contamination sites in which severe uncertainties and complex physics-based models are coupled to perform scientifically defensible decision analyses. The decision analyses are based on Information Gap Decision Theory (IGDT). We demonstrate the MADS capabilities by solving a decision problem related to optimal monitoring network design. © 2014 American Society of Civil Engineers.