A Parameter Estimation and Identifiability Analysis Methodology Applied to a Street Canyon Air Pollution Model

Mathematical models are increasingly used in environmental science thus increasing the importance of uncertainty and sensitivity analyses. In the present study, an iterative parameter estimation and identifiability analysis methodology is applied to an atmospheric model – the Operational Street Pollution Model (OSPMr). To assess the predictive validity of the model, the data is split into an estimation and a prediction data set using two data splitting approaches and data preparation techniques (clustering and outlier detection) are analysed. The sensitivity analysis, being part of the identifiability analysis, showed that some model parameters were significantly more sensitive than others. The application of the determined optimal parameter values was shown to succesfully equilibrate the model biases among the individual streets and species. It was as well shown that the frequentist approach applied for the uncertainty calculations underestimated the parameter uncertainties. The model parameter uncertainty was qualitatively assessed to be significant, and reduction strategies were identified.

The Southern Ischia canyon system: examples of deep sea depositional systems on the continental slope off Campania (Italy)

The Southern Ischia canyon system has been investigated in detail through Multibeam bathymetry and Sparker seismic data and has been put in the geological framework of the deep sea depositional systems off the Campania region. The geological and geomorphological characteristics of the canyon system have been also compared with the characters of the Mediterranean submarine canyons and with the deep sea depositional systems of the Tyrrhenian sea. The Southern Ischia canyon system engraves a narrow continental shelf from Punta Imperatore to Punta San Pancrazio, being limited southwestwards from the relict volcanic edifice of the Ischia Bank. It consists of twenty-two drainage axes, whose planimetric trending has been reconstructed in a sketch morphological map realized through the geological interpretation of Multibeam bathymetry. While the eastern boundary of the canyon system is controlled by extensional tectonics, being limited by a NE-SW trending (anti-Apenninic) normal fault, its western boundary is controlled by volcanism, due to the growth of the Ischia volcanic bank. Submarine gravitational instabilities also acted in relationships to the canyon system, allowing for the individuation of large-scale creeping at the sea bottom and hummocky deposits already interpreted as debris avalanche deposits. Quaternary marine seismic sequences have been reconstructed through a densely spaced seismic grid recorded through a Sparker multitip seismic source, allowing for a detailed observation of steep erosional slopes occurring on the southern flank of the island and related deep sea depositional systems. Important implications of this study will regard the coastal monitoring and beach nourishment of the southern flank of the island, being involved by a strong erosion of marine and coastal systems.

An Integrated approach to street canyon pollution modelling.

An integrated method for the prediction of the spatial pollution distribution within a street canyon directly from a microscopic traffic simulation model is outlined. The traffic simulation package Paramics is used to model the flow of vehicles in realistic traffic conditions on a real road network. This produces details of the amount of pollutant produced by each vehicle at any given time. The authors calculate the dispersion of the pollutant using a particle tracking diffusion method which is superimposed on a known velocity and turbulence field. This paper shows how these individual components may be integrated to provide a practical street canyon pollution model. The resulting street canyon pollution model provides isoconcentrations of pollutant within the road topography.

Sea-level control on the connection between shelf-edge deltas and the Bourcart canyon head (western Mediterranean) during the last glacial/interglacial cycle

A dense grid of high- and very high resolution seismic data, together with piston cores and borehole data providing time constraints, enables us to reconstruct the history of the Bourcart canyon head in the western Mediterranean Sea during the last glacial/interglacial cycle. The canyon fill is composed of confined channel–levee systems fed by a series of successively active shelf fluvial systems, originating from the west and north. Most of the preserved infill corresponds to the interval between Marine Isotope Stage (MIS) 3 and the early deglacial (19 cal ka BP). Its deposition was strongly controlled by a relative sea level that impacted the direct fluvial/canyon connection. During a period of around 100 kyr between MIS 6 and MIS 2, the canyon “prograded” by about 3 km. More precisely, several parasequences can be identified within the canyon fill. They correspond to forced-regressed parasequences (linked to punctuated sea-level falls) topped by a progradational-aggradational parasequence (linked to a hypothetical 19-ka meltwater pulse (MWP)). The bounding surfaces between forced-regressed parasequences are condensed intervals formed during intervals of relative sediment starvation due to flooding episodes. The meandering pattern of the axial incision visible within the canyon head, which can be traced landward up to the Agly paleo-river, is interpreted as the result of hyperpycnal flows initiated in the river mouth in a context of increased rainfall and mountain glacier flushing during the early deglacial.

Fluid dynamic analysis of trees influence in dispersion of pollutant in urban street canyon

degli elementi vegetali nella dinamica e nella dispersione degli inquinanti nello street canyon urbano. In particolare, è stato analizzata la risposta fluidodinamica di cespugli con altezze diverse e di alberi con porosità e altezza del tronco varianti. Il modello analizzato consiste in due edifici di altezza e larghezza pari ad H e lunghezza di 10H, tra i quali corre una strada in cui sono stati modellizati una sorgente rappresentativa del traffico veicolare e, ai lati, due linee di componenti vegetali. Le simulazioni sono state fatte con ANSYS Fluent, un software di "Computational Fluid Dynamics"(CFD) che ha permesso di modellizare la dinamica dei flussi e di simulare le concentrazioni emesse dalla sorgente di CO posta lungo la strada. Per la simulazione è stato impiegato un modello RANS a chiusura k-epsilon, che permette di parametrizzare i momenti secondi nell'equazione di Navier Stokes per permettere una loro più facile risoluzione. I risultati sono stati espressi in termini di profili di velocità e concentrazione molare di CO, unitamente al calcolo della exchange velocity per quantificare gli scambi tra lo street canyon e l'esterno. Per quanto riguarda l'influenza dell'altezza dei tronchi è stata riscontrata una tendenza non lineare tra di essi e la exchange velocity. Analizzando invece la altezza dei cespugli è stato visto che all'aumentare della loro altezza esiste una relazione univoca con l'abbassamento della exchange velocity. Infine, andando a variare la permeabilità delle chiome degli alberi è stata trovatta una variazione non monotonica che correla la exchange velocity con il parametro C_2, che è stata interpretata attraverso i diversi andamenti dei profili sopravento e sottovento. In conclusione, allo stadio attuale della ricerca presentata in questa tesi, non è ancora possibile correlare direttamente la exchange velocity con alcun parametro analizzato.

Marine litter in the upper São Vicente submarine canyon (SW Portugal): abundance, distribution, composition and fauna interactions

Marine litter has become a worldwide environmental problem, tainting all ocean habitats. The abundance, distribution and composition of litter and its interactions with fauna were evaluated in the upper S. Vicente canyon using video images from 3 remote operated vehicle exploratory dives. Litter was present in all dives and the abundance was as high as 3.31 items100m(-1). Mean abundance of litter over rock bottom was higher than on soft substrate. Mean litter abundance was slightly higher than reported for other canyons on the Portuguese margin, but lower in comparison to more urbanized coastal areas of the world. Lost fishing gear was the prevalent type of litter, indicating that the majority of litter originates from maritime sources, mainly fishing activity. Physical contact with sessile fauna and entanglement of specimens were the major impacts of lost fishing gear. Based on the importance of this region for the local fishermen, litter abundance is expected to increase.

Observations of anti-winds in a deep alpine valley, Lake Tekapo, New Zealand

This paper presents observations of summertime anti-winds monitored under ideal conditions in the Lake Tekapo hydro-catchment situated in the central Southern Alps, New Zealand. Onset and cessation of anti-winds was observed to coincide with the change in phase of the surface limbs of thermally generated valley and mountain winds under settled anti-cyclonic conditions. Anti-winds were best developed in the early morning before surface heating and associated convective mixing of the valley atmosphere began to mask the boundaries between the surface based limb of the mountain-valley wind and the corresponding anti-wind. By mid-day, the anti-valley wind exceeded the height of the surrounding ridgeline and became embedded in the topographically channeled gradient wind. Observations presented here have both theoretical and applied implications with regard to the development of thermally generated wind systems in deep alpine valleys, and their role in the dispersion of air pollution.

Comparative genetic study confirms exceptionally low genetic variation in the ancient and endangered relictual conifer, Wollemia nobilis (Araucariaceae)

The Wollemi pine, Wollemia nobilis (Araucariaceae), was discovered in 1994 as the only extant member of the genus, previously known only from the fossil record. With fewer than 100 trees known from an inaccessible canyon in southeastern Australia, it is one of the most endangered tree species in the world. We conducted a comparative population genetic survey at allozyme, amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) loci in W. nobilis, Araucaria cunninghatnii and Agathis robusta - representatives of the two sister genera. No polymorphism was detected at 13 allozyme loci, more than 800 AFLP loci or the 20 SSR loci screened in W. nobilis. In Ag. robusta only one of 12 allozyme loci, five of 800 AFLP loci and none of the 15 SSR loci were variable. For A. cunninghamii, 10 of > 800 AFLP loci and five of 20 SSR loci were variable. Thus low genetic diversity characterizes all three species. While not ruling out the existence of genetic variation, we conclude that genetic diversity is exceptionally low in the Wollemi pine. To our knowledge this is the most extreme case known in plants. We conclude that the combination of small population effects, clonality and below-average genetic variation in the family are probable contributing factors to the low diversity. The exceptionally low genetic diversity of the Wollemi pine, combined with its known susceptibility to exotic fungal pathogens, reinforces current management policies of strict control of access to the pines and secrecy of the pine locations.