A. M. G. Pacheco

An evaluation of olive-tree bark for the biological monitoring of airborne trace-elements at ground level

There is a need to start looking into the possibility of tree bark for biomonitoring. Bark from olive trees (Olea europaea Linn.) has been collected over an area in northwestern Portugal, featuring a blend of rural lands, industrial towns and coastal environments. Samples were analysed through INAA and PIXE for their elemental contents. Results from both techniques were reconciled and then compared with an extensive database on 46 trace elements in Parmelia spp. thalli from the same sites and mostly from the very bark substrates. Distribution-free, nonparametric statistics show that, despite signal magnitude, variation patterns of bark and lichen concentrations follow one another in a most significant way. Selected elements in bark also correlate to a superior extent. As far as this investigation goes, there is no reason whatsoever for discarding bark as an alternative to lower epiphytes.

Investigating tree bark as an air-pollution biomonitor by means of neutron activation analysis

The olive tree (Olea europaea) is an icon of southern Europe and awidespread evergreen in mainland Portugal. First results of a continuing studyon the ability of olive-tree bark to act as an air-pollution biomonitor arepresented and discussed here. Other than lower signals and an anticipatedsystemic control over some elements, there seems to be no a priori reasonfor ruling out the possibility of using bark in atmospheric trace-elementsurveys. In fact, nonparametric statistics show that, despite their relativemagnitude, the variation patterns of bark and lichen concentrations significantlyfollow one another all across the study area.

Monitoring of environmental contaminants: 10 years of application of k0-I INAA

Examples of the application of k0 standardized instrumental neutron activation analysis (k0-INAA) to aerosols and biological monitors in the last 10 years at Instituto Tecnológico e Nuclear (ITN) are given. As an analytical technique, INAA, in association with the k0 method was applied to these materials in four different projects, aiming at monitoring concentrations of heavy metals and others elements in the atmosphere in the Portuguese territory. In these studies we analysed the lichen Parmelia sulcata Taylor and olive tree bark as monitors as well as aerosol samples. For each project some representative results are presented, followed by a discussion of the application of this technique to environmental studies.

Effect of particulate matter, atmospheric gases, temperature, and humidity on respiratory and circulatory diseases’ trends in Lisbon, Portugal

This study addresses the significant effects of both well-known contaminants (particles, gases) and less-studied variables (temperature, humidity) on serious, if relatively common, respiratory and circulatory diseases. The area of study is Lisbon, Portugal, and time series of health outcome (daily admissions in 12 hospitals) and environmental data (daily averages of air temperature, relative humidity, PM10, SO2, NO, NO2, CO, and O3) have been gathered for 1999–2004 to ascertain (1) whether concentrations of air pollutants and levels of temperature and humidity do interfere on human health, as gauged by hospital admissions due to respiratory and circulatory ailments; and (2) whether there is an effect of population age in such admissions. In general terms, statistically significant (p < 0.001) correlations were found between hospital admissions and temperature, humidity, PM10, and all gaseous pollutants except CO and NO. Age appears to influence respiratory conditions in association with temperature, whereas, for circulatory conditions, such an influence likely involves temperature as well as the gaseous pollutants NO2 and SO2.

Trace-element measurements in atmospheric biomonitors—A look at the relative performance of INAA and PIXE on olive-tree bark

Abstract As part of an ongoing evaluation of its suitability for atmospheric biomonitoring, bark from olive trees ( Olea europaea Linn.) has been collected and searched for trace elements by means of two nuclear-analytical techniques—instrumental neutron activation analysis (INAA) and proton-induced X-ray emission (PIXE). The sampling for the present study was carried out across two separate sections of an established grid for air-quality surveys in mainland Portugal. The dual location comprises 58 collection sites—littoral-north (29 sites) and littoral-centre (29 sites). Both techniques are intrinsically accurate and may be seen to complement each other in the way that, as a whole, they yield 46 elements, with an overlap of 16 elements. Among the latter, this paper focuses on four of them and looks into their joint determination. Descriptive statistics for soil-related Al and Ti, and for sea-related Cl and Br, show results for each element to be fairly comparable. The degree of association between elemental patterns by either technique, as seen through nonparametric tests (Kendalls R K ), is outstanding. No statistical evidence (Wilcoxons T ) for relative bias in correlated samples—consistently higher or lower results by one technique—could be found as well. As far as this study goes, INAA and PIXE may be used interchangeably for determining the present elements in olive-tree bark.

An investigation of the dependence of atmospheric corrosion rate on temperature using printed-circuit iron cells

Abstract Chloride-mediated atmospheric corrosion was simulated on multilaminar, printed-circuit cells, in order to ascertain the effect of temperature on iron corrosion rate (early stages). Tests were carried out at 25, 35 and 45°C, under salt contaminations equivalent to chloride deposition rates of 0.25, 1.00 and 4.00 mg dm −2 day −1 ; relative humidity was kept at 85% throughout and surface wetness was allowed to result solely from moisture uptake. Electrochemical data generated by linear polarization and zero-resistance ammetry are discussed with reference to acceleration factors, energy barriers (Arrhenius model) and process control. Temperature has a direct, marked influence on the rate of corrosion and also seems to regulate the catalytic rate dependence on [Cl − ] through Freundlich isotherms. The apparent activation energy goes up to 87.5 kJ mol −1 , and gives almost perfect plots with [Cl − ] (semi-log) and electrode overpotential (linear). All features concerning energy barriers suggest an overall corrosion process under mixed control, bearing a significant, if not predominant contribution from charge transfer.

Trace-element enrichment in epiphytic lichens and tree bark at Pico Island, Azores, Portugal.

Abstract The Azores archipelago (nine islands) stretches across a sizable longitude span and sits directly on the pathway of long-range transport for airborne species over the North Atlantic Ocean. These airborne species include dusts from Africa’s Sahara and Sahel and non-natural contaminants from the United States’ eastern seaboard. Therefore, it is an ideal platform for watching significant deposition episodes in the area and/or simply keeping track of regular downward fluxes at ground level, either through conventional or unconventional (biological) air-monitoring approaches. For this purpose, thalli of the epiphytic lichens Parmotrema bangii (Vain.) Hale, and Parmotrema robustum (Degel) Hale; and outer bark from trunks of Cryptomeria japonica (Thunb. ex L.f.) D. Don—Japanese cedar—were collected in early 2003 at three sampling locations of Pico Island, Azores, Portugal. Lichens’ phorophyte was the cedar, and local soils were sampled as well. Following suitable handling and preparation procedures, all field samples were put through instrumental neutron activation analysis (INAA; k 0-variant) for elemental assessment. Reference data on airborne particulates were provided by a seven-wavelength aethalometer that continuously collects aerosols near the summit of Pico Mountain (observatory: 2225 m above mean sea level [AMSL]; peak: 2351 m AMSL) in quartz filter tapes. The overall results indicate that (1) the patterns of significant elemental enrichment (enrichment factor >10, relative to scandium) in lichen and bark samples are quite dissimilar, with lichen data reflecting more of the local inputs from some characteristic human activities, whereas bark appears predominantly enriched with far-ranged elements arriving in Pico’s atmosphere after long-distance transport; (2) regardless of prospective elemental sources—local or global, anthropogenic or natural—bark displays a more conservative (consistent) pattern through the sampling locations; and (3) not unlike earlier indications, altitude may have a negative influence in lichen enrichment, yet the present data seem insufficient to uphold such a trend.

Development and calibration of epiphytic lichens as saltfall biomonitors—dry-deposition modelling

Lichen transplants (Ramalina calicaris and Usnea spp.) were investigated as biomonitors of the atmospheric deposition of marine salt, and a calibration model was set up to predict the dry deposition of saline elements from the concentration of salt tracers in lichens. The study was performed in the Portuguese Atlantic coast, where a monthly transplantation program was run in two stations that show clear differences in terms of precipitation regimes. At both stations, dry deposition and precipitation records were kept for the whole duration of the program. General trends in results have indicated that rainwater may wash saline elements out of lichens, though such an effect does not appear to be linear. A multiple-regression approach was taken to look for a calibration between dry-deposition fluxes and lichen concentrations through a stepwise technique. The calibration model for data obtained in both stations features two break points that define precipitation ranges for low, moderate and heavy rain conditions. The results show that lichens can really be used to indicate the dry deposition of sea salt.

Assessment of bioaccumulation of REEs by plant species in a mining area by INAA

Native plant species, lichens and tailings, sampled from a copper–sulphide mining area located in southern–eastern Portugal, were analysed by neutron activation analysis (INAA) for determination of rare earth elements (REEs). Values of ΣREEs and individual REEs concentration of tailing samples are higher than those of natural background concentrations. The higher values of REEs are found in modern slags and the mixture of oxidized gossan and sulphide disseminated country rocks when compared with the alluvial sediments contaminated by mine tailings. The total concentrations of light REEs are higher than those of heavy REEs in all tailing samples. Distribution patterns of PAAS-normalized REEs in mine tailings show slightly LREE enriched and flat HREE pattern with negative Eu anomaly. Lichens accumulated higher concentration of lanthanides than vascular plants. The elevated levels of REEs in lichen, native plant species and tailing samples reflect the contamination of REEs in São Domingos mining area. The Carlina corymbosa, Erica australis and Lavandula luisierra accumulated the higher amounts of La, Ce and other REEs than the other plant species grown in this mining area.

Saline variability at ground level after kriging data from Ramalina spp. biomonitors

Abstract Sea-salt input over the land masses is known to have deleterious effects on man-made structures, plants (crops and natives) and soil/water resources. Recent work has shown the ability of some epiphytic-lichen species to monitor the deposition of airborne salts of marine origin. The atmospheric transport and inland deposition of marine salts can thus be assessed by measuring saline elements in lichens growing over coastal areas. The concentration of Cl − and Na + was determined in lichen thalli collected on three different occasions in south-western Portugal. The extracellular fraction of Na + was obtained by a sequential elution procedure and surface Cl − was recovered after leaching samples with water. The dispersion of element concentration in the area was studied through geostatistical analysis. Numerical values were estimated by two interpolation methods: ordinary kriging and kriging with an external drift. The latter method used the logarithm of the distance to the coast as an auxiliary variable and yielded more reliable results. Every set of data produced a similar spatial pattern, showing a steep gradient in the first 3 km from the coast. However, considerable variation can be observed between surveys. The variability of results is interpreted using the precipitation data obtained for the region under consideration.