M. C. Freitas

Distribution in Portugal of some pollutants in the lichen Parmelia sulcata

During the months of July and August 1993 a lichen (Parmelia sulcata Taylor) collection campaign was held in Portugal where samples were obtained from olive tree bark at 228 sites, following a grid of 10 x 10 km along the Atlantic coast and 50 x 50 km in the interior of the country. The samples were analysed by instrumental neutron activation analysis and proton induced X-ray emission techniques. Concentration data patterns for the pollutants As, Cr, Hg, Ni, Pb, S, Sb, Se, and V were obtained for the whole country surface by making use of an extinction rule of 1/r(3), preventing any cut-off distance from being artificially introduced. Some pollution sources were identified: (1) oil-powered plants on the Lisbon-Setúbal axis (V, Ni), (2) coal-power plants in Porto and Sines (S, Se), (3) traffic in the northern area and the Lisbon-Setúbal axis (Pb), (4) a chemical industry south of Porto (Hg, As), and (5) soil influence (Cr, Sb). Arsenic and chromium results largely exceed, in a few areas, the concentrations acceptable to plants, and in a few spots also Hg, Ni, and Pb data.

The geological record of environmental changes in southwestern Portuguese coastal lagoons since the Lateglacial

Abstract The multidisciplinary study (sedimentology, palaeoecology, geochemistry, isotopic dating) of the sedimentary infill of selected coastal lagoons of the southwestern Portuguese coast suggests that during the Early Holocene, eustasy was the dominating element forcing coastal change and controlled the sedimentation patterns of these areas. The strong decrease of the mean sea-level rise rate observed in the Middle Holocene defined an important threshold of regional significance. The flooded lowlands developed terminal barriers and started to silt up initially driven by natural forcing factors (e.g. climate, sediment supply) of local expression, which were later added or overwhelmed by anthropic influence. The latter relates with deforestation and agriculture, inducing changes of sedimentation rates and sediment delivery to the coast; human interference with the natural rhythms of barrier breaching generated significant change of the whole physico-chemical setting of the lagoonal basins that translated into sediments, water quality and depth and local ecosystems structure. This paper presents examples of the impacts of global versus local factors and natural versus anthropic influences as driving factors of coastal change since the Lateglacial. The available data suggest that this line of research is crucial to support objective and accurate models of past and future coastal evolution.

Bio-monitoring of trace-element air pollution in Portugal: Qualitative survey

During the months of July and August 1993 a lichen collection campaign was held in Portugal where about 250 samples were collected and analysed by thick target TIPIXE and INAA. Results for 44 different elements were obtained and a data base was built and subjected to Monte Carlo Aided Target Transform Factor Analysis (MCATTFA), a method developed at IRI (Delft). 10×10 km2 coast and 50×50 km2 far from coast sampling grids were used for collection. In this work we will present the results which were obtained based on a reduced data set of 36 elements measured by INAA. The results for 22 elements obtained by TTPIXE were published elsewhere. In this work we will also present the conclusions considering all the 44 elements determined by both techniques.

Comparing historic records of storm frequency and the North Atlantic Oscillation (NAO) chronology for the Azores region

The storminess of the Azores region was investigated using newspaper records from AD 1836 onwards. The information obtained was rank-ordered for intensity and the time series of storm frequency analysed for interannual- to century-scale variability. The documentary data set was validated by comparison with objective cyclones intensity for the period AD 1958—2000. Results indicate that four periods of contrasting storm frequency are present (AD 1836—1870, 1870—1920, 1920—1940 and 1940—1998). The average storm lasts for 2.3 days and the average secular storm frequency is 3.1 storms/yr. Low intensity events occur four times every five years whereas an extreme storm occurs on average once every seven years. The documentary index of storminess is highly variable at different timescales, which is consistent with other studies of storminess in the North Atlantic. Nevertheless, an objective comparison between late nineteenth- and late twentieth-century storm frequency does not reveal a significant difference. Between AD 1865 and the late twentieth century the winter NAO and storminess indices show a statistically significant anti-correlation pattern at the monthly and seasonal scales. In the late nineteenth century and between AD 1950 and 1970 the NAO index was low and the storminess index high, whilst the opposite occurred from the early twentieth century until the middle 1950s; since AD 1970 both indexes reveal positive trends and are predominantly positive. The NAO mode of circulation is partially responsible for the storminess spatial pattern and temporal distribution over the Azores region since AD 1865 and for about a century, however this relation appears to have weakened since the 1960s.

Main atmospheric heavy metal sources in Portugal by biomonitor analysis

Abstract During the months of July and August of 1993 a lichen collection campaign was held in Portugal where about 250 samples were collected and analysed by thick target PIXE and INAA. Results for 43 different elements were obtained and a data base was built and subjected to Monte Carlo aided target transform factor analysis (MCATTFA), method developed at IRI TU Delft. 10 × 10 km coast and 50 × 50 km far from coast sampling grids were used for collection, concentration data as well as factor patterns were extrapolated to the whole country making use of an extinction rule of 1/r 3 . In this work we present the results that were obtained based on a reduced data set of 22 elements measured by TTPIXE. The results for INAA data subset and the total data set are presented elsewhere.

Elemental analysis of particulate matter and source identification in Lisbon

A Gent PM10 air sampler with stacked filter units was used to collect size-fractionated aerosol samples in Lisbon between October 1993 and January 1995. Sampling was made on a twice-a-week basis (one weekend day and one midweek day). The filter loads were measured by gravimetry and elemental analyses were carried out by PIXE and INAA techniques. The complementarity of the techniques allowed the determination of the concentrations of 22 elements in more than 30% of all samples. Monitoring of NO, NO 2 , CO and SO 2 concentrations was also performed. Time variations for both total particulate mass and elemental concentrations are presented. Weekend and midweek data are compared. Enrichment factors were calculated for the fine and coarse fractions and the ratios between the two fractions were derived. Principal components analysis was applied to the identification of aerosol sources Correlations were found between the gases and coarse particle elemental concentrations. A tendency for a concentration increase in the total suspended particle mass was observed at the end of each year. The concentration pattern for the rare earth elements measured was altered owing to the activity of a nearby refinery.

Dune, Bluff and Beach Erosion due to Exhaustive Sand Mining – the Case of Santa Barbara Beach, São Miguel (Azores, Portugal).

ABSTRACT Coastal dunes are relatively rare features in the Azores islands and contribute to less then 1% to the total length of the archipelagos littoral zone, circa 844 km. Localised indications of aeolian activity, contemporaneous to the arrival of the first colonists in the 15th century have been found, but at present most of the coastal dunes are vegetated and stabilised. Dune sand has been exploited during the 20th century for industrial use, leading to severe damage or complete removal of a significant proportion of these features. In the 1950s the Santa Barbara area contained a rare and well-preserved example of an undisturbed active beach-foredune system, free of anthropogenic activities. It displayed a well-nourished beach profile margined by a coastal foredune and a climbing dune, which covered the adjacent bluff and extended landwards through an aeolian sand-sheet. Persistent sand mining between the early sixties and the late eighties, lead to volumetric depletion of the dune cover, lowering of the surface of the berm and triggering cliff erosion. In total, some 950,000 m3 of sand has been removed, the dunes making up half of this figure. Although this activity was stopped in 1995 by legal enforcement, the erosive process still currently persists indicating a surpassing of the natural resilience and maximum vulnerability of the coastal dune system. At present the bluff retreats at very high rates (0.6 m/yr), the dune features were totally obliterated and the sandy beach has been reduced in width to a single swash ramp which floods during half of the tidal cycle.

A tsunami record in the sedimentary archive of the central Algarve coast, Portugal: Characterizing sediment, reconstructing sources and inundation paths

This study describes sedimentation associated with the tsunami generated by the Lisbon earthquake of ad 1755. It is argued here that the tsunami deposited a sand sheet across the Lagoa dos Salgados (central Algarve, Portugal), that is intercalated with late-Holocene estuarine/lagoonal sediments. A wide range of proxies (sedimentological, exoscopic and palaeontological) are used to establish the provenance of the sandy material as well as to constrain the age of the deposit. Stratigraphic criteria are used to distinguish the uniqueness of the event layer. Exoscopic and textural analysis suggest that the source of the event deposit is mainly the dune, beach and underlying layer. Micropalaentological analysis (Foraminifera) indicates a conspicuous increase in diversity and dominance of marine species within the event sediment sheet. The spatial characteristics of the tsunami layer suggests that the barrier prevented widespread overtopping by the incoming tsunami allowing inference of c. 10 m as maximum height at the coast; they also indicate the inlet as the preferential route for both water and sediment transported inland. Dating results (14C, 210Pb and 137Cs) allow extrapolation of an age of deposition compatible with the ad 1755 Lisbon earthquake and tsunami, the most devastating event that affected this coastal area in historical times. Correlations with similar deposits detected in nearby lowlands strengthen the argument that the tsunami sediment layer represents a marker horizon in the coastal stratigraphy along the Portuguese Algarve coast. The stratigraphic uniqueness of this event might have implications in the establishment of millennial scale recurrence intervals for this type of high-energy marine inundation.

Holocene Changes in the Douro Estuary (Northwestern Iberia)

Abstract Holocene changes are recorded by sedimentology and palynology on a 20 m long core retrieved in the mouth of the Douro estuary (northwestern Portugal). Results show that the early Holocene (10720–6530 calibrated [cal] YBP) was characterized by a warm and humid climate as testified by a well-established Pinus–Quercus–Alnus regional forest. Shelf and slope foraminifera assemblages as well as echinoderms gradually increased toward the end of this period, reflecting the sea-level rise that occurred between 11500 and 6000 cal yr BP. A gravel barrier developed in the southern part of the estuary as a result of sea-level rise attenuation and strong hydrodynamism of the river. A radical change from regional fluvially transported pollen assemblages (mainly composed of trees) to pollen spectra derived from local vegetation (mainly Ericaceae and Poaceae) occurred between 6530 and 1500 cal yr BP, contemporaneously to the settlement of the gravel barrier. This suggests that the northward migration of the river main channel, already testified by the existence of a palaeovalley with its axis located southward of the present main channel, occurred as early as 6530 cal yr BP.

The sedimentary record of recent (last 500 years) environmental changes in the Seixal Bay marsh, Tagus estuary, Portugal

The inner Tagus estuary is essentially a sedimentation basin that receives cohesive sediment from terrestrial, marine, biological and anthropogenic sources. Three short cores from one site in a marsh area of this estuary (Seixal Bay) were analysed for sedimentary, geochemical and micropalaeontological contents (benthic foraminifera and nannoplankton). The length of the cores represents about half a millennium of sedimentation. Textural analysis suggests a highly uniform mud sedimentation for most of the cores but geochemical, mineralogical and micropaleontological results indicate climatic and environmental changes and anthropogenic disturbance. Three Foraminifera zones were identified. The lower part of the lower zone indicates sedimentation in an open channel or a lower domain of an exposed high-energy sandflat. Sediments of the upper part of the lower zone and of the middle zone were deposited in a lower-energy environment, probably associated with a sheltered, vertically aggrading mudflat located within the Seixal Bay. Biological and mineralogical indicators suggest that periods of total or partial closure of this bay occurred. Clay minerals indicate that drier and colder conditions prevailed in the lower half of this zone evolving gradually to a wetter and warmer environment towards the top. The upper zone indicates persistence of low-energy sedimentation and evolution towards the present salt-marsh conditions. Anthropogenic pollution is clear in geochemical proxies at the top of the sedimentary column and was used for dating purposes.