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Abstract: Fracture networks control the permeability of many reservoirs. Since the fracture patterns of petroleum reservoirs in situ are difficult to study in detail, field analogues are very important for understanding their fracture-related permeability. Here we present the results of a study of the fracture system of carbonate rocks of Lower Cretaceous age in a quarry associated with the damage zone and fault core of a major fault zone on the Gargano Peninsula in South Italy. We measured the attitude of 1541 fractures and faults along several vertical and horizontal scan lines. There are two main fracture sets: one strikes between E–W and ESE–WNW, the other NNE–SSW. A total of 675 fracture-spacing measurements indicate log-normal spacing distributions, with an arithmetic mean fracture spacing of 0.29m and a median of 0.15m. The data, plotted on a log–log plot, suggest three main spacing subpopulations, each of which follows approximately a power law with different fractal dimensions. Subpopulation 1, where the spacing ranges from 1 to 10cm and the straight-line slope D (“fractal dimension”) is 0.20, represents fractures confined to laminated carbonate mudstones (multilayers) that form the microbial mat deposits of a peritidal cycle. Subpopulation 2, where the spacing ranges from 11 to 55cm and D is 0.77, represents fractures confined to thicker layers, forming a part of a peritidal cycle, the contacts of which are marked by stylolites. Subpopulation 3, where the spacing ranges from 56 to 243cm and D is 2.81, represents fractures that dissect comparatively thick units of an entire peritidal cycle. For the spacing, the minimum coefficient of variation, Cv, defined as standard deviation divided by the mean, is 1.00 (essentially randomly spaced fractures) while its maximum Cv is 1.62, suggesting that some fractures form clusters, some clusters being denser than others. The clusters, composed of fractures with varying attitudes and therefore commonly intersecting, are likely to contribute significantly to the overall permeability of the carbonate rock. Fracture-aperture (opening) data (N =324) also show a log-normal size distribution, with a mean opening of 1.01cm and median of 0.29cm. Log–log plots indicate that a part of this data groups into two subpopulations, I and II, each of which follows approximately a power law. The straight-line slope D (“the fractal dimension”) of subpopulation I is 0.46, whereas that of subpopulation II is 1.49. We present boundary-element models showing that laminated carbonate mudstones and their contacts modify the local stress fields so as to encourage fracture offset and, commonly, arrest. Our results also show that when a fluid-driven subpopulation 2 fracture approaches subpopulation 1 fractures, the induced tensile stresses may result in the opening up of many of the subpopulation 1 fractures directly above the tip of the subpopulation 2 fractures. If, in addition, the contacts between the multilayers are weak, they also tend to open up, thus generating a large interconnected cluster of vertical fractures and horizontal contacts. The results suggest that the tensile stresses induced by a comparatively large fluid-driven subpopulation 2 fracture may contribute to the formation of an interconnected cluster of subpopulation 1 fractures and associated contacts, thereby significantly increasing the permeability of the carbonate rock. [Copyright &y& Elsevier]

A novel approach for measuring vertical profiles of HCs and particle number concentrations was described and applied in the low troposphere over Milan (Italy) during typical spring and summer days. Particle profiles yielded nearly homogeneous concentrations below the mixing height, with level-to-ground concentration ratios of 92-97%, while HCs showed a more pronounced decrease (74-95%). Vertical mixing and photochemical loss of HCs were demonstrated to cause these gradients. Much lower concentrations were observed for the profiles above the mixing height, where the HC mixtures showed also a different composition, which was partially explained by the horizontal advection of air with HC sources different to those prevailing at the site. The application of pseudo-first order kinetics for reactions between HCs and the hydroxyl radical allowed for the estimation of the vertical mixing time scale in the order of 100 ± 20 min., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

The European Ozone Directive 2002/3/EC specifies the analysis of 30 individual C2-C9 hydrocarbons in urban air with the attribution of emission sources to pollution concentrations as a major objective. In the present study, we investigate an approach for source apportionment of these ozone precursor hydrocarbons in urban air based on reliable semi continuous volatile organic compound (VOC) analysis in the field and in vehicle emission laboratory combined with multivariate receptor modeling. The GC system relies on an hourly analytical cycle based on a trap sample enrichment phase followed by a dual column gas chromatographic flame ionisation detector (FID) analysis and has successfully been tested during an air monitoring campaign at an urban site (Milan, Italy, September 2003) and in the vehicle laboratory performing exhaust emission measurements while running driving cycles on a chassis dynamometer (mopeds, gasoline and diesel cars). The receptor modeling relies on two complementary principles. The chemical mass balance (CMB) modeling apportions well characterized source profiles for the 30 individual C2-C9 hydrocarbons in the Ozone Directive to the concentrations in ambient air and produces source contribution estimates (SCE) as output. The positive matrix factorization (PMF) analyses variability in the ambient air concentration data and searches for latent variables consisting of co-varying hydrocarbons and produces profiles as output, which in this study could be attributed to known emission sources. Both CMB and PMF rely on an estimated uncertainty for each input data. A new approach is presented, by which the uncertainty is allowed to float as function of the photochemical reactivity of the atmosphere and the stability of each individual compound.

Human milk from four major Italian cities was analyzed for individual congeners of polychlorinated biphenyls (PCB), DDT, DDE, hexachlorobenzene, and beta-hexachlorocyclohexane. Minimum and maximum concentrations in milk from individual mothers for most compounds ranged between one order of magnitude below and above the mean value of all mothers. Good agreements were found between results from pooled samples and mean values of individual samples. No statistically significant difference between cities was found and the levels in milk from Italian mothers did not differ significantly from published levels from other parts of the world. Principal component analyses revealed that the PCB congener distribution pattern was very similar in all mothers, independent of location. Average concentrations in milk from the four cities were 19(+/- 5) micrograms liter-1 total PCB or 3.2(+/- 0.8) ng liter-1 toxicity equivalents according to the most conservative TCDD toxicity equivalent factors of PCBs proposed in the literature, 70(+/- 18) micrograms liter-1 DDE, 4.5(+/- 1.2) micrograms liter-1 DDT, 5.6(+/- 1.9) micrograms liter-1 HCB, and 4.4(+/- 1.7) micrograms liter-1 beta-hexachlorocyclohexane.