Remediation actions at contaminated sites are based on multiple numerical model scenarios considering different parameter distributions, source positions and contaminant transport paths. In some cases the excess of scenarios is due to uncertainties in the conceptual model as a result of the spread of contamination through heterogeneities in the physical system. Reduction of project hypotheses and conceptual model uncertainty is therefore needed. This result can be achieved by coupling hydrogeological investigations with environmental forensic techniques, better localization of the source and understanding of contamination history. In this respect, in the present study, compositional fingerprinting and groundwater flow modeling were applied to a former oil storage facility where, even though a hydraulic barrier had been built to stop the hydrocarbon plume, the presence of some hydrocarbons was still found in downgradient monitoring wells. The final aim was to evaluate the efficacy of the hydraulic barrier and identify of the source of pollution. Fingerprinting results indicated pollution with a gasoline-diesel mixture much altered by water washing and/or biodegradation. Comparison of seven groundwater samples collected in wells and monitoring wells was performed by analyzing the volatile fraction (BTEX) and the total ion chromatogram (TIC), focusing attention on: n-alkanes (m/z 85), alkylcyclohexanes (m/z 83), isoprenoids (m/z 113), C4-alkylbenzenes (m/z 134), C3-C6 alkylbenzenes and polycyclic aromatic hydrocarbons (PAHs). The most probable scenario was then identified by combining the results of fingerprinting with different contaminant paths obtained using the numerical model. 相似文献
Nitrate is a worldwide pollutant in aquifers. Shallow aquifer nitrate concentrations generally display vertical stratification, with a maximum concentration immediately below the water level. The concentration then gradually decreases with depth. Different techniques can be used to highlight this stratification. The paper aims at comparing the advantages and limitations of three open hole multilevel sampling techniques (packer system, dialysis membrane samplers and bailer), chosen on the base of a literary review, to highlight a nitrate vertical stratification under the assumption of (sub)horizontal flow in the aquifer. The sampling systems were employed at three different times of the year in a shallow aquifer piezometer in northern Italy. The optimal purge time, equilibration time and water volume losses during the time in the piezometer were evaluated. Multilevel techniques highlighted a similar vertical nitrate stratification, present throughout the year. Indeed, nitrate concentrations generally decreased with depth downwards, but with significantly different levels in the sampling campaigns. Moreover, the sampling techniques produced different degrees of accuracy. More specifically, the dialysis membrane samplers provided the most accurate hydrochemical profile of the shallow aquifer and they appear to be necessary when the objective is to detect the discontinuities in the nitrate profile. Bailer and packer system showed the same nitrate profile with little differences of concentration. However, the bailer resulted much more easier to use.
Nanomaterials have widespread applications in several industrial sectors. ZnO nanoparticles (NPs) are among the most commonly
used metal oxide NPs in personal care products, coating and paints. However, their potential toxicological impact on the environment
is largely unexplored. 相似文献
Aim of this work is to shed light on sustainable value and develop a model, based on vSa and translated at applicative level through the system dynamics methodology for measuring sustainable value. By adopting vSa perspective, value, characterized by strongly subjective contents, will be considered as a vector quantity, as the result of the subjective weighting of the different dimensions that may change according to the considered organization. Starting from the analysis of system dynamics and vSa, we will implement the theoretical framework into a model developed with system dynamics, hence through a methodology capable of addressing systemic problems which is also an expressive approach to solve issues arising in complex systems (characterized by interdependence, mutual interaction, information feedback, circular causality). In order to translate theory into “action and application” we will develop a model through which it will be possible to exploit the advantages of vSa implemented into an SD model, which ultimately can also be instantiated to specific cases and then simulated for further quantitative insights. Currently, there is no theoretical/practical approach to sustainable value measurement for business organizations that simultaneously considers the dimensions of the triple bottom line together with the subjective perspective of decision-makers. From these considerations, we derived the idea to integrate vSa and system dynamics with the aim of analyzing the issue of sustainable value, whose triple dimension is usually (erroneously) seen under a perspective that does not consider the interactions among those three dimensions. The integration of the subjective perspective within a model for calculating sustainable value can be seen as considering vSa as the theoretical framework, and system dynamics as the methodology that allows translating such an approach into a model that can later be simulated. It is also worth mentioning that through the application of the vSa theory to the case of sustainable value, by means of a transcoding approach like the system dynamics one, we are somehow trying to “redefine”, or better “enhance”, the vSa theory itself, by “operationalizing” it. 相似文献