A. J. Sousa

Distribution of trace metals in moss biomonitors and assessment of contamination sources in Portugal.

A biomonitoring survey using the moss species [Hypnum cupressiforme Hedw. and Scelopodium touretii (Brid.) L. Kock] was performed in the whole territory of Portugal, in order to evaluate the atmospheric deposition of the following elements: Cd. Cr, Cu, Fe, Mn, Ni, Pb and Zn. The concentrations of the same elements were also obtained in two types of soil samples, collected under the moss and in nearby plots without any plant coverage, and relationships between moss and soil concentrations was investigated using the multivariate statistical method of Co-inertia Analysis. Also, relationships between concentrations in moss and several anthropogenic, geologic, pedologic and environmental parameters were screened using the same method of Co-inertia Analysis. Higher concentrations of Cu, Pb and Zn were found in areas of higher population density, with higher gasoline consumption, while higher values of Fe and Cr occur in the driest region, with lower plant coverage, indicating strong contamination by resuspended soil particles. Results also show good agreement between moss and soil contents, even for elements with high contribution of anthropogenic sources. The spatial pattern in Portugal of element contents in mosses were also detected and discussed in relation to local contamination sources.

Application of geostatistical methods in gold geochemical anomalies identification (Montemor-O-Novo, Portugal)

Abstract The study described herein concerns the application of geostatistical methods to data soil from Montemor-O-Novo area (Southern Portugal). In the area, the gold mineralised zones (Banhos, Caeiras, Fales, Gamela, Malaca and Monfurado) are characterised by different geological settings and mineralogical assemblages. A total of 1211 soil samples were collected in Montemor-O-Novo area and analysed for Cu, Pb, Zn, As, Ba and Au by atomic absorption spectrometry. To account for spatial structure, simple and cross variograms were computed for the main directions of the grid sampling. From the experimental variograms a linear model of coregionalization composed of three structures, a nugget effect and two anisotropic spherical structures, was fitted to each of the six variables. The coregionalization matrices deduced from the theoretical model show the relationships between the variables at different scales. These matrices were compared with those obtained by principal component analysis (PCA). This methodology was the basis for estimating the corresponding spatial components (Y0, Y1 and Y2) using factorial kriging analysis (FKA). Maps of raw data, Y0, Y1 and Y2 were made for each variable. The use of multivariate analysis permit the study of the spatial structure intrinsic to geochemical data and the identification and refinement of significant anomalies related to Au-bearing mineral deposits.

Geochemistry, mineralogy, solid-phase fractionation and oral bioaccessibility of lead in urban soils of Lisbon

AbstractAn urban survey of Lisbon, the largest city in Portugal, was carried out to investigate its environmental burden, emphasizing metallic elements and their public health impacts. This paper examines the geochemistry of lead (Pb) and its influence on human health data. A total of 51 soil samples were collected from urban recreational areas used by children to play outdoors. The semi-quantitative analysis of Pb was carried out by inductively coupled plasma mass spectrometry after an acid digestion. X-ray diffraction was used to characterize the soil mineralogy. The solid-phase distribution of Pb in the urban soils was investigated on a subset of 7 soils, out of a total of 51 samples, using a non-specific sequential extraction method coupled with chemometric analysis. Oral bioaccessibility measurements were obtained using the Unified BARGE Method developed by the Bioaccessibility Research Group of Europe. The objectives of the study are as follows: (1) investigation of Pb solid-phase distribution; (2) interpretation of Pb oral bioaccessibility measurements; (3) integration of metal geochemistry with human health data; and (4) understanding the influence of geochemistry and mineralogy on oral bioaccessibility. The results show that the bioaccessible fraction of Pb is lower when major metal fractions are associated with less soluble soil phases such as Fe oxyhydroxides, and more increased when the metal is in the highly soluble carbonate phase. However, there is some evidence that the proportion of carbonates in the soil environment is also a key control over the oral bioaccessibility of Pb, irrespective of its solid-phase fractionation.

Identification of geochemical anomalies using principal component analysis and factorial kriging analysis

Abstract The purpose of this paper is to identify geochemical anomalies using the combined application of data analysis and geostatistical methods. Data from a local multi-element geochemical prospecting soil survey in NW Spain were used to illustrate this application. The principal component analysis was first used to establish the different associations among variables and afterwards to obtain a homogeneous group for applying the geostatistical methodology. The selected group was composed of Zn, Co, Ni, Cr, Cu, and Fe, which were strongly correlated with the first principal component (PC1). Taking advantage of this high correlation between the group of elements and the component 1, we used PC1 as a new variable for numerically identifying anomalies. The geostatistical approach to this problem involved computing variograms of PC1 and subsequently a decomposition of this variable using factorial kriging analysis. The results of the use of factorial kriging analysis demonstrate its value as a filter in geochemical prospecting when attempting to differentiate between anomalous samples and those belonging to geochemical background. The use of a variable that groups an association of elements, instead of identifying individual anomalies, is one of the advantages of applying principal component analysis.

Soil geochemical prospecting for gold at Marrancos (Northern Portugual)

Abstract This paper discusses some geochemical mapping techniques and their effectiveness in detecting of gold and its pathfinders geochemical anomalies. The study area (Marrancos area) is situated in Northern Portugal. Gold occurs in a quartz breccia with pyrite and arsenopyrite hosted by metamorphic rocks (hornfels) and it is present in these two sulphide minerals as inclusions or disseminated in the crystal lattice. In this area, the geochemical anomalies obtained by isoconcentration mapping of single elements were difficult to interpret. The use of alternative geochemical mapping such as multielement halos (additive halos) proved to be effective in the definition of Au, As, Bi, Sb, Te and Se secondary geochemical signature.

Lead availability in soils from Portugal’s Centre Region with special reference to bioaccessibility

Previous environmental biomonitoring studies indicated higher environmental lead (Pb) pollution levels at the districts of Aveiro and Leiria (Portugal). In evaluating the risk for human health, which is associated with contaminated soils after oral uptake, total soil concentrations have generally been held against criteria established from toxicological studies based upon the assumption that the uptake of the contaminant is similar in the toxicological studies and from the soils assessed. This assumption is not always valid, as most toxicological studies are carried out with soluble forms of the contaminants, whereas many soil contaminants are or become embedded in the soil matrix and thus exhibit limited availability. This study intends to estimate the soluble fraction of Pb in the soils from central Portugal, and to assess the bioaccessibility of Pb and, hence, infer exposure and risk for human health. Yet, as the physical–chemical properties of the soil exert some control over the solubility of Pb in the surface environment, the relation between such soil properties and the estimated soluble and/or bioaccessible fractions of Pb is also investigated. Other objective, with a more practical nature, was to give some contribution to find a suitable in vitro mimetic of the gastrointestinal tract environment. The results indicate relatively low total metal concentrations in the soils, even if differences between regions were observed. The Aveiro district has the higher total Pb concentration and the metal is in more soluble forms, that is, geoavailable. Soils with higher concentrations of soluble Pb show higher estimates of bioaccessible Pb. Soil pH seems to influence human bioaccessibility of Pb.

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 human exposure to environmental heavy metals in soils and bryophytes of the central region of Portugal

This study intends to identify the spatial patterns of variation for some metals and metalloids, in soils and mosses, in the central region of Portugal. The purposes were: (i) to identify relationships amongst five elements (Cu, Pb, Zn, Cr and As) in three different media (topsoil, bottom soil and bryophytes) and with some site-specific characteristics, using Multiple Correspondence Analysis; (ii) to define spatial patterns of variation for the associations identified by Multiple Correspondence Analysis using Variography and Ordinary Kriging; and (iii) to assess atmospheric deposition as a source of heavy metals to the topsoil by crossing results with the biomonitors. The results indicated relatively low metal concentrations in soils and mosses. Some metal associations and dissociations were identified. The spatial patterns of variation of bottom and topsoil are distinct. There is some evidence that different site-specific characteristics control the spatial distribution of different elements. The areas within the central region of Portugal with a higher vulnerability to metal contamination were identified.

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.

Soil data analysis from central Portugal by Principal Component Analysis and geostatistical techniques

The area under study is located near Estarreja, in central Portugal where chemical industries are the main source of pollution. Until 1975, liquid effluents produced by these industrial units were discharged directly into several nearby streams. These effluents contained many different types of contaminants, such as aniline, benzene, monochlorobenzene, mononitrobenzene, As, Hg, Zn and Pb, amongst others. The industrial units also dumped a large amount of solid waste, which was stockpiled, directly on the surrounding land. This solid waste contains pyrite-rich ashes, dusts and sludge containing Hg and calcium hydroxide. A geochemical soil survey was conducted in a 49-km2 area where a total of 985 soil samples were collected during 1998 and 1999, on a regular grid of 200 × 200 m. The soil samples were analysed for Cu, Pb, Zn, Fe, Mn, Co, Ni, Cr and As, following an HCl–HNO3–HF digestion. To identify the main soil contaminants and to map the most important contaminated areas, Principal Component Analysis (PCA) and geostatistical techniques (Variography and Kriging map) were used. The results of PCA data analysis, compared to the available information in pollution indices (Contamination Index – Cidx), outline one important area contaminated by Cu, Pb, Zn and As as a result of effluent dumping by the chemical industry.