Evaluation of the use of photochemical indicators to assess ozone—NOx—VOC sensitivity in the Southwestern Iberian Peninsula

Understanding the chemical links between ozone (O₃) and its two main precursors, nitrogen oxides (NOx) and volatile organic compounds (VOC), is important for designing effective photochemical smog reduction strategies. This chemical relationship will determine which precursor (NOx or VOC) emission reduction will be more effective for decreasing the ozone formation. Under certain conditions, ozone levels decrease as a result of a reduction in NOx emissions but do not respond significantly to changes in VOC emissions (NOx-sensitive condition), while under other conditions ozone concentrations decrease in response to reductions in VOCs and may even increase when NOx emissions are reduced (VOC-sensitive conditions). Indicator species can be used to assess the sensitivity of ozone to changes in the emissions of its precursors. These indicators are species or species ratios involved in ozone photochemistry which reflect the primary chemical process through which the ozone was formed. In this work we use the MM5-CAMx model system to explore the behaviour of various indicator species during two meteorological situations featuring different atmospheric conditions in a complex terrain area. The results show that indicators based on nitrogen compounds (i.e,. NOy and NOz) are suitable for defining the transition range from VOC- to NOx-sensitive chemistry, and that despite the uncertainties associated with the use of chemical indicators, the ratios O₃/NOy and O₃/NOz may provide a simple and useful way to summarize the response of ozone to changes in NOx and VOC emissions in Southwestern Spain.     

Study of the Interaction between Biological Cells of Different Shapes and Sizes and Electromagnetic Fields Produced by Natural Phenomena

We carry out a study of the interaction between electromagnetic fields produced innature and cells with no structure but with different shapes and sizes, considered asapproximations of those observed in the human body. Magnetic fields produced byvarious atmospheric and geomagnetic phenomena are compared with the fieldsgenerated by the cells themselves. Working with frequencies up to 10⁵ Hz, we found that in most cases lightning is the natural phenomena capable of producingfield intensities comparable to those generated by the cells. As a first approximationwe assume that a cell might be affected only if a field of intensity comparable to thecell's field is present. Oscillating fields of less intensity and their harmonics can involveresonant interactions with the cells, however this situation is not considered here. Under the approximation of our study we found that the size and the shape are parameters of paramount importance: lightning represents a natural hazard only for the largest cells, while the quadrangular cells are not affected by any of the natural phenomena considered here.     

Weathering phases recorded by gnammas developed since last glaciation at Serra da Estrela, Portugal

The morphometrical analysis of gnammas (weathering pits) in granite landscapes has been used to establish the relative chronology of recent erosive surfaces and to provide the weathering history in a region. To test the validity of gnammas as relative chronometer indicators, and the reliability of the obtained weathering record, two sites have been studied in Serra da Estrela, Portugal. The first site is within the limits of the glacier that existed in these mountains during the last glaciation, whereas the second site is located in an unglaciated sector of the mountains, which preserves a longer record of weathering in the bedrock surface. The number of gnamma weathering phases recorded in the latter site (8) is larger than those from the former (6). Correlation between both measurement stations based on morphometrical criteria is excellent for the younger six weathering phases (1 to 6). Consequently, the parameter used for relative chronology (δ-value) has been verified to be age dependent, although absolute values are modulated by microclimate due to altitude variations. The weathering record was essentially duplicated once the surfaces at both sites were exposed, demonstrating the reliability of gnamma evolution as a post-glacial environmental indicator for the region.     

Geologic evolution of the Serrinha nucleus granite–greenstone terrane (NE Bahia, Brazil) constrained by U–Pb single zircon geochronology

U–Pb single zircon crystallization ages were determined using TIMS and sensitive high resolution ion microprobe (SHRIMP) on samples of granitoid rocks exposed in the Serrinha nucleus granite–greenstone terrane, in NE Brazil. Our data show that the granitoid plutons can be divided into three distinct groups. Group 1 consists of Mesoarchaean (3.2–2.9 Ga) gneisses and N-S elongated TTG (Tonalite-Trondhjemite-Granodiorite) plutons with gneissic borders. Group 2 is represented by ca. 2.15 Ga pretectonic calc-alkaline plutons that are less deformed than group 1. Group 3 is ca. 2.11–2.07 Ga, late to post-tectonic plutons (shoshonite, syenite, K-rich granite and lamprophyre). Groups 2 and 3 are associated with the Transamazonian orogeny. Xenocryst ages of 3.6 Ga, the oldest zircon yet recorded within the São Francisco craton, are found in the group 3 Euclides shoshonite within the Uauá complex and in the group 2 Quijingue trondhjemite, indicating the presence of Paleoarchaean sialic basement.Group 1 gneiss-migmatitic rocks (ca. 3200 Ma) of the Uauá complex constitute the oldest known unit. Shortly afterwards, partial melting of mafic material produced a medium-K calc-alkaline melt, the younger Santa Luz complex (ca. 3100 Ma) to the south. Subsequent TTG melts intruded in different phases now exposed as N-S elongated plutons such as Ambrósio (3162 ± 26 Ma), Araci (3072 ± 2 Ma), Requeijão (2989 ± 11 Ma) and others, which together form a major part of the Archaean nucleus. Some of these plutons have what appear to be intrusive, but are probably remobilized, contacts with the Transamazonian Itapicuru greenstone belt. The older gneissic rocks occur as enclaves within younger Archaean plutons. Thus, serial additions of juvenile material over a period of several hundred m.y. led to the formation of a stable micro-continent by 2.9 Ga. Evidence for Neoarchaean activity is found in the inheritance pattern of only one sample, the group 2 Euclides pluton.Group 2 granitoid plutons were emplaced at 2.16–2.13 Ga in a continental arc environment floored by Mesoarchaean crust. These plutons were subsequently deformed and intruded by late to post-tectonic group 3 alkaline plutons. This period of Transamazonian orogeny can be explained as a consequence of ocean closure followed by collision and slab break-off. The only subsequent magmatism was kimberlitic, probably emplaced during the Neoproterozoic Braziliano event, which sampled older zircon from the basement.     

The impact of dolomite and plagioclase weathering on the chemistry of shallow groundwaters circulating in a granodiorite-dominated catchment of the Sila Massif (Calabria,Southern Italy)

This work is aimed at investigating the weathering processes of the granodiorites cropping out in a small catchment of the Sila Massif. The mineral constituents in this granodiorite are plagioclase, often zoned with a Ca-rich core and a Na-rich rim, quartz, chlorite, K-feldspar, white mica and epidote. During this study, dolomite was discovered in local stream sediments, as separate monomineralic grains, probably resulting from erosion of veins cutting the crystalline rocks. Prevailing dissolution of foreign dolomite and a Ca-rich plagioclase is suggested by the Ca–Mg–HCO₃ chemical composition of local groundwaters and stream waters, which is rather unexpected for waters interacting with granitoid rocks. These qualitative observations are quantitatively confirmed by reaction path modelling of the weathering processes occurring in the study area, which was carried out using the EQ3/6 software package, version 8.0, and the Double Solid Reactant Method. Indeed, it was possible to ascertain that the release of both major dissolved constituents and several trace elements (Ba, Co, Cr, Fe, Mn, Ni, Pb, Sr, V and Zn), from rocks to waters, is chiefly controlled by the dissolution of foreign dolomite and the Ca-rich core of zoned plagioclases.     

Analysis of the degree of contamination and evolution in the last 100 years of the composition of the bed sediments of the Anllóns Basin

In this study, five cores of the Anllóns River bed sediments were analyzed in order to evaluate the downcore and downstream variations in their chemical composition. The first step was the evaluation of the metal distribution in the bulk (<2 mm) and fine fractions (<63 μm). The analysis revealed that most of the metals followed the same trend in both fractions, although the fine fraction presented usually higher concentrations. However, the concentration of both fractions tended to equalize with increasing contamination. No general increase was observed in the metal concentrations toward the surface which could be attributed to recent anthropogenic contributions. Instead, the distributions were homogeneous or peaked at various depths downcore. The most important historical feature was observed at the mouth of the river, at 96-cm depth, corresponding to the end of the eighteenth century. Upcore increased metal concentrations in parallel with increased fine fraction occurred from this depth, which were attributed to a bridge construction and consequent changes in sediment dynamics. As the metal concentrations can be influenced by variations in texture or other sediment characteristics, the second step was to evaluate the efficiency of several normalized indexes in the assessment of the degree of contamination, by calculating the enrichment factor (EF), the geoaccumulation index (I _GEO) and the pollution load index (PLI). The EFs obtained were <10, thus revealing little anthropogenic inputs to the basin. The I _GEO produced higher values when compared with the EFs. Instead of absolute EF or I _GEO absolute values, the use of cumulative probability plots allowed identifying more accurately potential outliers indicating contamination. Only one population was identified for Zn and Pb, with a reduced number of outliers at the highest concentrations for Pb. As shown, a more complex plot with the outliers identified at C4 and C5. Finally, the PLI allowed determining the absence of a significant contamination in the bed sediments. The bioavailable and non-geogenic fractions contribute up to a 90% of the total concentrations in the case of As and Cu, and showed similar (dissimilar) profiles in comparison with total metals. Also, the quality guidelines were surpassed, so the high solubility of As, Zn, Pb and Ni in the sediments revealed the need to monitor the bed sediment quality of the Anllóns River.     

Heterotrophic bacteria community and pollution indicators of mussel--farm impact in the Gulf of Gaeta (Tyrrhenian Sea).

Field studies were carried out to determine and compare the impact of organic loads due to the biodeposition of a mussel farm on the water quality and sediment in a coastal area of the Tyrrhenian Sea (Western Mediterranean). A total of five environmental and five microbial parameters were examined from March, 1997 to February, 1998 on a monthly basis at three stations: the first was located under the mussel farm, the second located at about 40 m away from the mussel farm, while the third designed as a control was at about 1-km. No clear changes in the physical characteristics of the water masses were observed, comparing the three sampling sites and the water column generally showed homogeneous conditions (in terms of temperature and salinity). Changes in density of aerobic heterotrophic bacteria, Escherichia coli and Enterococci in the water column are apparently independent from changes in environmental parameters. At all stations a constant significant correlation between temperature and presumptive Vibrio parahaemolyticus was reported suggesting that this abiotic factor exerted a major control on this bacterial group and its distribution in the water column is not related to the biodeposition of the mussel farm. The major impact identified was on the sediment where variations in bacterial abundance was observed. In the Mussel station sediment enrichment of organic compounds, and the consequent modification of the characteristics of the benthic environment, determined an increase in aerobic heterotrophic bacteria, and particularly of vibrios density (on average about 60%), suggesting that these bacteria are good indicators of organic enrichment.     

Compact Groups of Galaxies: Evolution of the Stellar Population

We present a study focusing on the nature of compact groups (CGs) through the study of their elliptical (E) galaxies. Parameters describing the internal dynamics and the stellar populations of the galaxies are compared with their counterparts in other environments. Our sample has24 bright E galaxies located in the core of Hickson CGs and 11 bright ‘bona fide’ Es, located in the field or very loose groups. Their spectra were obtained with the 2.1 m Telescope at KPNO and have a 4.1 Å resolution over the wavelength range 3500–7000 Å. We have found that, from the dynamical point of view, E galaxies in CGs are essentially similar to those in dense clusters. Moreover, the stellar populations of Es in CGs seem to be older and less metal rich than those in the field, behaviour which has also been observed by Rose et al. (1994).     

Energy release in solar flares

Team 2 of the Ottawa FLARES 22 Workshop dealt with observational and theoretical aspects of the characteristics and processes of energy release in flares. Main results summarized in this article stress the global character of the flaring phenomenon in active regions, the importance of discontinuities in magnetic connectivity, the role of field-aligned currents in free energy storage, and the fragmentation of energy release in time and space.Report of Team 2, Flares 22 Workshop, Ottawa, May 25–28, 1993.