PAH Distributions in Sediments from High Mountain Lakes

Abstract

The PAH distributions in sediment cores from eight remote lakes distributed over Europe have been investigated. All sites show a similar qualitative composition, being dominated by parent compounds from phenanthrene to coronene. Perylene, a diagenetically produced PAH, dominates the mixtures in deep sediment layers. The distribution and ratios of specific compounds indicate that these hydrocarbons are of pyrolitic origin, mainly from coal combustion processes, but contributions from other sources are also present (i.e., retene is probably indicative of wood combustion inputs). The qualitative differences due to inputs, sources or physico-chemical conditions are discussed.     

Discrimination between different samples of olive oil using variable selection techniques and modified fuzzy artmap neural networks

An electronic nose for classification of olive oil samples is presented. Principal component analysis and a modified fuzzy artmap neural network where applied to data acquired from 12 sensors. A custom designed variable selection technique was also used to boost performance. Ten different samples of olive oils were classified with 78% accuracy, and confusion occurred mostly between similar olive oils. Defective samples were separated from defect-free olive oil with 97% accuracy. These results show that careful variable selection, coupled to a modified fuzzy artmap algorithm, can significantly improve electronic nose performance.     

The infection capacity of P. expansum and P. digitatum on apples and histochemical analysis of host response

Fruit ripening is a complex process that involves a variety of biochemical changes and is also associated with increased susceptibility to pathogens. The present study determined the effects of fruit maturity and storage conditions on the infection capacity of a host (P. expansum) and non-host (P. digitatum) pathogen on apple. A range of inoculum concentrations and two different storage temperatures were utilized. Exposure to P. expansum at 20 °C resulted in significant differences in rot dynamics in apples collected at the earliest harvest date compared to all later harvest dates and inoculum concentrations assayed. Greater differences in infection capacity between harvests were obtained when fruit was stored at low temperature (0 °C). In contrast, P. digitatum was able to infect apples only under specific conditions and disease symptoms were limited to the initial wound inoculation site. When apples were resistant to P. digitatum, a visible browning reaction around the infection site was observed. Histochemical analyses of tissues surrounding the wound site were conducted. A positive reaction for lignin was observed in immature apples as early as 1 day after inoculation with either pathogen. Experiments conducted with the non-host pathogen indicated that lignification was an essential component of resistance in apples harvested prior to maturity or at commercial maturity. Apples harvested at an over-mature stage and inoculated with P. digitatum did not show evidence of staining for lignin until 7 days post-inoculation. Control samples only showed positive reaction in immature harvest. Results demonstrated that the maturity stage of fruit is an important factor in apple resistance to both P. expansum and P. digitatum and that lignin accumulation seems to play an important role when resistance is observed. Moreover, this is the first report demonstrating that P. digitatum, a non-host pathogen, has a limited capacity to infect apples.     

Infection capacities in the orange-pathogen relationship: compatible (Penicillium digitatum) and incompatible (Penicillium expansum) interactions

Penicillium digitatum and Penicillium expansum are the most devastating pathogens of citrus and pome fruits, respectively. Whereas P. digitatum is a very specific pathogen that only infects Citrus fruits, P. expansum has a broader host range but has not been reported to be infectious in Citrus. To determine the responses of fruits and the infection capacities of both moulds, two varieties of oranges at different maturity stages, different inoculum concentrations and two different storage temperatures were studied. In compatible interactions, no significant differences in rot dynamics among harvests were found with a 10⁷ conidia mL⁻¹ inoculum concentration at both temperatures tested (20 °C and 4 °C). However, at other inoculum concentrations, significant differences in rot dynamics were found, especially in immature fruits. Incompatible interactions showed that P. expansum could infect oranges at commercial maturity in both tested varieties. Decay incidence and severity were higher at 4 °C than at 20 °C. In addition to infection capacity studies, histochemical tests were performed to detect wound-healing compounds for both pathogens. A positive reaction for lignin was detected for both pathogens in immature oranges over a short period (48 h). In all cases, no reactions were found in control samples. Our results indicate that pathogen concentration, host maturity and storage temperature can play important roles in the defence mechanisms of fruit. Furthermore, to our knowledge, this is the first work that demonstrates that P. expansum can infect oranges under favourable conditions.     

Selective methane detection under varying moisture conditions using static and dynamic sensor signals

This paper reports the development of a methane analyser, which meets some of the requirements of a reliable domestic methane detector. The equipment is based on a five-element array that includes four tin oxide gas sensors and a humidity sensor. The pattern recognition engine is based on multilayer perceptron (MLP) neural networks trained with the back-propagation algorithm. Both static and dynamic signals from the sensors are fed into the neural networks to identify and quantify methane and ethanol. The system identifies and quantifies unknown samples of these contaminants, even when the ambient relative humidity varies broadly (from 25% to 80%). As a result, the equipment detects methane, rejects false alarms caused by ethanol and complies with some aspects of the European directive for domestic methane detectors.     

Volatile composition of wines from cvs. Blanco lexítimo,Agudelo and Serradelo (Vitis vinifera) grown in Betanzos (NW Spain)

Wine aroma is formed by volatile compounds of different chemical natures and origins. Betanzos is the most northern viticole geographic area from Galicia (NW Spain). The aromatic profiles of wines produced from two white varieties (Blanco lexítimo and Agudelo) and one red variety (Serradelo) from Betanzos, harvested in 2006 and 2007, have been established by gas chromatography (GC/FID). A total of 35 varietal and fermentative aroma compounds were identified and quantified in free volatile form, which include terpenols, C₁₃‐norisoprenoids, alcohols, esters, volatile fatty acids and volatile phenols. To ascertain the compounds with major impact odours, the Odour Activity Value (OAV) was calculated. Twelve compounds showed concentrations above their perception threshold (OAV>1). The results obtained suggest that ethyl octanoate (apple), isoamyl acetate (banana), ethyl hexanoate (fruity) and β‐damascenone (floral) were the most powerful odorants for the white wines Blanco lexítimo and Agudelo from Betanzos. Ethyl octanoate and β‐damascenone (fruity and floral aroma respectively) were the most odorant for the red wine Serradelo.     

Nanoparticle metal-oxide films for micro-hotplate-based gas sensor systems

We report on the use of either reactive magnetron sputtering or screen printing to deposit tin and tungsten-oxide gas-sensitive layers onto integrated micromachined arrays. The procedures allow the deposition of the sensing layers before membranes have been etched, which leads to gas microsensors with an excellent fabrication yield. The microstructure of the sensitive films is analyzed by means of SEM and EDX. The response of the different microarrays to ethanol, acetone, and ammonia vapors and their binary mixtures, and toxic gases such as NO/sub 2/ and CO, is studied at different operating temperatures. The response of the different sensors to ambient humidity is also investigated. Finally, it is shown that by using PCA and fuzzy ARTMAP neural networks, it is possible to simultaneously identify and quantify the toxic gases with a 100% success rate. A 95% success rate is obtained in the semi-quantitative analysis of vapors and vapor mixtures. These results prove the viability and usefulness of the techniques introduced to obtain integrated sensor microarrays that are suitable for battery-powered gas/vapor monitors.     

First study of determination of aromatic compounds of red wine from Vitis vinifera cv. Castañal grown in Galicia (NW Spain)

Wines produced from Vitis vinifera cv. Castañal from Galicia (NW Spain), harvest 2002 and 2003, were submitted to gas chromatography (GC/FID). A total of 36 varietal and fermentative aroma compounds were identified and quantified. The total concentration of aroma compounds in 2002 and 2003 vintage was 872.06 and 520.70 mg/L, respectively, which include free and bound terpenes and C₁₃-norisoprenoids, alcohols, acetates and ethyl esters. To estimate the contribution of specific compound to the aroma, the odour activity value (OAV) was calculated using the concentration of each component and the corresponding odour threshold reported in the literature. From 36 compounds identified, 10 were determined as the most powerful odorants: β-ionone, 3-methyl-1-butanol, benzyl alcohol, 2-phenylethanol, ethyl acetate, isoamyl acetate, ethyl lactate, ethyl butyrate, ethyl hexanoate and ethyl octanoate. These data suggested Castañal wines as a fruity (blackberry) and floral (rose) product.