This work aims at gaining information on the effects of different thermal treatments on radiocarbon measurements of organic (OC) and elemental (EC) carbon fractions in the atmospheric aerosol. ...Improvements to the traditional approaches for the determination of the fraction of modern carbon of OC and EC−fm(OC) and fm(EC)- are proposed.
As for fm(EC) determination, we propose to add a He step at high temperature to the standard oxygen treatment. Our tests demonstrate that the addition of a high temperature He step (final choice: 750°C) to the oxygen treatment is effective in removing the refractory OC.
As for fm(OC) determination, we propose to quantify it by measuring either the fraction of modern carbon of TC and EC or the fraction of modern carbon of water soluble (fm(WSOC)) and water insoluble (fm(WINSOC)) organic carbon to limit the influence of possible pyrolysis on the direct determination of fm(OC). Tests on the equivalence of the approaches have shown good agreement between them.
Our tests were carried out on samples collected in a heavily polluted area (Milan, Italy) during wintertime. fm(OC), fm(EC), and fm(TC) values obtained in our tests were also used to attempt a preliminary source apportionment in the area using 14C measurements. Wintertime EC resulted to be mainly fossil (84%), whereas OC was dominated by modern contribution (63%).
Two approaches were tested for the evaluation of the wood burning contribution to OC and a good agreement was found. Wood burning primary contribution accounted for about 18% of OC in Milan during wintertime.
Secondary OC from biomass burning and the contribution from other urban sources were tentatively identified following literature approaches, with the aim of evaluating the biogenic contribution to OC in the area, which was estimated to be about 18%.
► Improvements to thermal protocols for 14C analysis of OC and EC were carried out. ► A suitable filter washing procedure was set up. ► A high temperature He step was added to the oxygen step to improve EC isolation. ► Two alternative approaches for fm(OC) determination were tested. ► Carbonaceous particles source apportionment was attempted.
Prescriptive research is at the heart of the project management (PM) disciplines. For decades, researchers and practitioners alike have been searching for methodological solutions to practical ...project management problems. Scheduling methods or risk management methodologies are just two examples. Despite this long tradition of prescriptive research, PM methods suffer from a number of problems, such as a lack of acceptance in practice, limited effectiveness, and unclear application scenarios. In this article, we identify a lack of empirical and theoretical foundations as one cause of these deficiencies. Based on a review of existing PM literature and a thorough analysis of other successful prescriptive disciplines, we develop a framework designed to serve as a guideline for theoretically grounded prescriptive PM research. The framework outlines how theories and empirical investigations can help build applicable and useful prescriptive research results. We illustrate our framework by applying it to the case of the critical chain method. Our contribution is twofold: our research results can foster the discourse on methodological support for prescriptive PM research; it may also help set up viable prescriptive research designs.
► We develop a framework designed to serve as a guideline for prescriptive PM research. ► The framework shows how theories and empirical data can help build prescriptive research results. ► We illustrate our framework by applying it to a critical chain method.
We present a potential-field-constrained inversion procedure based on a priori information derived exclusively from the analysis of the gravity and magnetic data (self-constrained inversion). The ...procedure is designed to be applied to underdetermined problems and involves scenarios where the source distribution can be assumed to be of simple character. To set up effective constraints, we first estimate through the analysis of the gravity or magnetic field some or all of the following source parameters: the source depth-to-the-top, the structural index, the horizontal position of the source body edges and their dip. The second step is incorporating the information related to these constraints in the objective function as depth and spatial weighting functions. We show, through 2-D and 3-D synthetic and real data examples, that potential field-based constraints, for example, structural index, source boundaries and others, are usually enough to obtain substantial improvement in the density and magnetization models.
The LABEC laboratory, the INFN ion beam laboratory of nuclear techniques for environment and cultural heritage, located in the Scientific and Technological Campus of the University of Florence in ...Sesto Fiorentino, started its operational activities in 2004, after INFN decided in 2001 to provide our applied nuclear physics group with a large laboratory dedicated to applications of accelerator-related analytical techniques, based on a new 3 MV Tandetron accelerator. The new accelerator greatly improved the performance of existing Ion Beam Analysis (IBA) applications (for which we were using since the 1980s an old single-ended Van de Graaff accelerator) and in addition allowed to start a novel activity of Accelerator Mass Spectrometry (AMS), in particular for
14
C dating. Switching between IBA and AMS operation became very easy and fast, which allowed us high flexibility in programming the activities, mainly focused on studies of cultural heritage and atmospheric aerosol composition, but including also applications to biology, geology, material science and forensics, ion implantation, tests of radiation damage to components, detector performance tests and low-energy nuclear physics. This paper describes the facilities presently available in the LABEC laboratory, their technical features and some success stories of recent applications.
SUMMARY
We use a multiscale approach as a semi‐automated interpreting tool of potential fields. The depth to the source and the structural index are estimated in two steps: first the depth to the ...source, as the intersection of the field ridges (lines built joining the extrema of the field at various altitudes) and secondly, the structural index by the scale function. We introduce a new criterion, called ‘ridge consistency’ in this strategy. The criterion is based on the principle that the structural index estimations on all the ridges converging towards the same source should be consistent. If these estimates are significantly different, field differentiation is used to lessen the interference effects from nearby sources or regional fields, to obtain a consistent set of estimates. In our multiscale framework, vertical differentiation is naturally joint to the low‐pass filtering properties of the upward continuation, so is a stable process. Before applying our criterion, we studied carefully the errors on upward continuation caused by the finite size of the survey area. To this end, we analysed the complex magnetic synthetic case, known as Bishop model, and evaluated the best extrapolation algorithm and the optimal width of the area extension, needed to obtain accurate upward continuation. Afterwards, we applied the method to the depth estimation of the whole Bishop basement bathymetry. The result is a good reconstruction of the complex basement and of the shape properties of the source at the estimated points.
We analyzed new magnetic, bathymetric, and seismic data acquired in the offshore sector of Somma‐Vesuvius volcano (Italy). We detected a group of high‐intensity, short wavelength magnetic anomalies ...corresponding to partly buried volcanic dome‐like structures located by seismic data. The magnetic anomalies are aligned along a NW‐SE strike that is the preferential orientation of an eruptive fracture of the pre‐19 ka activity of Vesuvius. Four cones emplaced after the Last Glacial Maximum (19 ka), whereas a fifth one emplaced more recently suggesting a rejuvenation of the eruptive system offshore the volcano in historical times. We also identified a NE‐SW elongated magnetic anomaly consistent with a dike‐like body associated to an on‐land tectonic structure that was active in recent times at Vesuvius. A delta‐like area with diffuse low‐intensity magnetic anomalies reflects the seaward fronts of lava flows that entered the sea mainly during the Middle Ages.
Key Points
Volcanic vents <19 ka in the Somma‐Vesuvius offshore near the coast
Lava delta in the offshore formed between about 1000 and 1861 A.D.
Submarine volcanism and lava entering the sea must be included in the Vesuvian area hazard evaluation
A simple and fast determination of the limiting depth to the sources may represent a significant help to the data interpretation. To this end we explore the possibility of determining those source ...parameters shared by all the classes of models fitting the data. One approach is to determine the maximum depth-to-source compatible with the measured data, by using for example the well-known Bott–Smith rules. These rules involve only the knowledge of the field and its horizontal gradient maxima, and are independent from the density contrast.
Thanks to the direct relationship between structural index and depth to sources we work out a simple and fast strategy to obtain the maximum depth by using the semi-automated methods, such as Euler deconvolution or depth-from-extreme-points method (DEXP).
The proposed method consists in estimating the maximum depth as the one obtained for the highest allowable value of the structural index (Nmax). Nmax may be easily determined, since it depends only on the dimensionality of the problem (2D/3D) and on the nature of the analyzed field (e.g., gravity field or magnetic field). We tested our approach on synthetic models against the results obtained by the classical Bott–Smith formulas and the results are in fact very similar, confirming the validity of this method. However, while Bott–Smith formulas are restricted to the gravity field only, our method is applicable also to the magnetic field and to any derivative of the gravity and magnetic field. Our method yields a useful criterion to assess the source model based on the (∂f/∂x)max/fmax ratio.
The usefulness of the method in real cases is demonstrated for a salt wall in the Mississippi basin, where the estimation of the maximum depth agrees with the seismic information.
► The maximum-depth to potential field sources is an important information. ► We compare results provided by classical formulas and semi-automated methods. ► These results are identical if cylinder (2D) or sphere (3D) models are considered. ► Our procedure can be applied to gravity and magnetic fields or tensors. ► It can be applied to source models for which classical formulas do not hold.
PDF
