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H Freitas

Publications and source records attributed to H Freitas.

10 recordsLinked to original sources
PubMed2006

Sources of phenolic compounds in two catchments of southern Portugal - effect of season, land use and soil type.

Water quality monitoring in reservoirs used for human water consumption, carried out by the Alentejo Regional Authorities of the Environment (south Portugal), revealed seasonal peaks of phenolic compounds above the water-quality legislation. The main objectives of this work were to identify the main phenolic compounds present in water and soil leachates, and to determine the sources of the seasonal concentrations of phenolic compounds in two catchments with different land use patterns: Roxo and Santa Clara catchments. The main phenolic compound detected was 2,4-dinitrophenol (2,4-DNP), both in stream water and soil leachates, with concentrations higher in Roxo catchment. Roxo catchment represents a larger agricultural area than Santa Clara, and it is likely that the origin of the 2,4-DNP is associated with the use of pesticides. A peak of 2,4-DNP concentrations was observed in stream water of both catchments during February, when farmers plough their fields and apply pesticides. The 2,4-DNP peak was probably caused by a precipitation event shortly after the application of pesticides, increasing their transfer from land surfaces to adjacent streams. The leaching behaviour of 2,4-DNP was strongly dependent on the type of soil and pH. In soils with high clay content and low pH, 2,4-DNP was easily adsorbed, and its runoff from the soil to adjacent streams was reduced. Ribeira de Santa Vitória, from Roxo catchment, was the only stream showing a high abundance of vegetation, and the lowest concentrations of 2,4-DNP in water. Plants may play a role in removing contaminants from stream water.

2,4-Dinitrophenol↗
PubMed2004

Effects of Li+ transport and intracellular binding on Li+/Mg2+ competition in bovine chromaffin cells.

Li(+) transport, intracellular immobilisation and Li(+)/Mg(2+) competition were studied in Li(+)-loaded bovine chromaffin cells. Li(+) influx rate constants, k(i), obtained by atomic absorption (AA) spectrophotometry, in control (without and with ouabain) and depolarising (without and with nitrendipine) conditions, showed that L-type voltage-sensitive Ca(2+) channels have an important role in Li(+) uptake under depolarising conditions. The Li(+) influx apparent rate constant, k(iapp), determined under control conditions by (7)Li NMR spectroscopy with the cells immobilised and perfused, was much lower than the AA-determined value for the cells in suspension. Loading of cell suspensions with 15 mmol l(-1) LiCl led, within 90 min, to a AA-measured total intracellular Li(+) concentration, [Li(+)](iT)=11.39+/-0.56 mmol (l cells)(-1), very close to the steady state value. The intracellular Li(+) T(1)/T(2) ratio of (7)Li NMR relaxation times of the Li(+)-loaded cells reflected a high degree of Li(+) immobilisation in bovine chromaffin cells, similar to neuroblastoma, but larger than for lymphoblastoma and erythrocyte cells. A 52% increase in the intracellular free Mg(2+) concentration, Delta[Mg(2+)](f)=0.27+/-0.05 mmol (l cells)(-1) was measured for chromaffin cells loaded with the Mg(2+)-specific fluorescent probe furaptra, after 90-min loading with 15 mmol l(-1) LiCl, using fluorescence spectroscopy, indicating significant displacement of Mg(2+) by Li(+) from its intracellular binding sites. Comparison with other cell types showed that the extent of intracellular Li(+)/Mg(2+) competition at the same Li(+) loading level depends on intracellular Li(+) transport and immobilisation in a cell-specific manner, being maximal for neuroblastoma cells.

Animals↗
PubMed2004

Analysis of serpentinophytes from north-east of Portugal for trace metal accumulation--relevance to the management of mine environment.

In north-east of Portugal, the serpentinized area is about 8000 ha with a characteristic geology and flora. The serpentine plant community and respective soils were analyzed to examine the trace metal budget in different tissues of the plants exhibiting resistance to trace metals. One hundred and thirty five plant species belonging to 39 families and respective soils have been analyzed for total Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn. Substantial amounts of Ni, Cr, Co and Mn were detected in plant tissues which are listed below: NI: Alyssum serpyllifolium (38105); Bromus hordeaceus (1467); Linaria spartea (492); Plantago radicata (140); Lavandula stoechas (118) and Cistus salvifolius (114); CR: L. spartea (706.7); Ulmus procera (173.4); A. serpyllifolium (129.3); Cistus ladanifer (40.8); L. stoechas (29.5); P. radicata (27.81); Setariopsis verticillata (25.7); Plantago lanceolata (24); Digitalis purpurea (23.4); Logfia minima (23.1); Arenaria querioides (23); Hieracium peleteranum (22.7); Arenaria montana (14.5); CO: A. serpyllifolium (145.1); L. spartea (63.2); P. radicata (10.4); H. peleteranum (7.3); Lepidium heterophyllum (6.9); A. querioides (6.6); C. salvifolius (6.5); C. ladanifer (6.3); L. stoechas (6.1); Anthyllis lotoides (6.1); L. minima (6.1); Euphorbia falcata (5.7) and B. hordeaceus (5.6); MN: A. serpyllifolium (830); L. spartea (339); L. stoechas (187.1); L. minima (182.7); Castanea sativa (125); Spergula pentandra (124); P. radicata (119); Cytisus striatus (115.4); Quercus pyrenaica (110); Teucrium scorodonia (109.4); Fraxinus vulgaris (109); Anthyllis sampaiana (108); Quercus ilex (108). The significance of serpentine flora, need for conservation of these fragile and environmentally invaluable plant resources for possible use for in situ remediation of metalliferous substrates are presented in this paper.

Environment↗
PubMed2004

Plant community tolerant to trace elements growing on the degraded soils of São Domingos mine in the south east of Portugal: environmental implications.

The selection of trace element tolerant species is a key factor to the success of remediation of degraded mine soils. Mining activities generate a large amount of waste rocks and tailings, which get deposited at the surface. The degraded soils, the waste rocks and tailings are often very unstable and will become sources of pollution. The direct effects will be the loss of cultivated land, forest or grazing land, and the overall loss of production. The indirect effects will include air and water pollution and siltation of rivers. These will eventually lead to the loss of biodiversity, amenity and economic wealth. Restoration of a vegetation cover can fulfil the objectives of stabilization, pollution control, visual improvement and removal of threats to human beings. Thus, remediation of mine spoils/tailings and biogeochemical prospecting would rely on the appropriate selection of plant species. Plant community responds differently on their ability to uptake or exclude a variety of metals. In this work, plant species were sampled from all populations established in an abandoned copper mine of São Domingos, SE Portugal. Plants belonging to 24 species, 16 genera and 13 families were collected from the degraded copper mine of São Domingos. Plant samples were analysed for total Ag, As, Cu, Ni, Pb, and Zn. The highest concentrations of metals in soils dry matter were 11217.5 mg Pb kg(-1), 1829 mg Cu kg(-1), 1291 mg As kg(-1), 713.7 mg Zn kg(-1), 84.6 mg Cr kg(-1), 54.3 mg Co kg(-1), 52.9 mg Ni kg(-1) and 16.6 mg Ag kg(-1). With respect to plants, the higher concentrations of Pb and As were recorded in the semi-aquatic species Juncus conglomeratus with 84.8 and 23.5 mg kg(-1) dry weight (DW), Juncus efusus with 22.4 and 8.5 mg kg(-1) DW, and Scirpus holoschoenus with 51.7 and 8.0 mg kg(-1) DW, respectively. Thymus mastichina also showed high content of As in the aboveground parts, 13.6 mg kg(-1) DW. Overall, the results indicate accumulation of various metals by different plant species, with some of these metals being partitioned to the shoots. Environmental implications of these observations are discussed.

Copper↗
PubMed2000

Removal of toxic metals from solution by leaf, stem and root phytomass of Quercus ilex L. (holly oak).

Increased consciousness for safeguarding the aqueous environment has prompted a search for alternative technologies for the removal of toxic metal ions from aqueous solutions. In this regard, a wide variety of biomass is being considered as adsorbents of heavy metals for treatment of industrial and domestic wastewaters as well as natural waters, including drinking water. In the present investigation, the potential of Quercus ilex phytomass from stem, leaf and root as an adsorbent of chromium (Cr), nickel (Ni), copper (Cu), cadmium (Cd) and lead (Pb) at ambient temperature was investigated. The metal uptake capacity of the root for different metals was found to be in the order: Ni>Cd>Pb>Cu>Cr; stem Ni>Pb>Cu>Cd>Cr; and leaf Ni>Cd>Cu>Pb>Cr. The highest amount adsorbed was Ni (root>leaf>stem). Data from this laboratory demonstrated that Ni is sequestered mostly in the roots, where concentrations can be as high as 428.4 ng/g dry wt., when 1-year-old seedlings were treated with Ni (2000 mg/l) in pot culture experiments, compared to 7.63 ng/g dry wt., control (garden and greenhouse soil) topsoil where Ni was present in trace amounts. This proves that the root biomass of Q. ilex has the capacity for complexing Ni. Cr exhibited the least adsorption values for all the three types of phytomass compared to other metals. The trend of adsorption of the phytomass was similar for Ni and Cd, i.e. root>leaf>stem. Desorption with 10 mM Na(4) EDTA was effective (55-90%) and, hence, there exists the possibility of recycling the phytomass. The biosorption results of recycled phytomass suggest that the selected adsorbents are re-usable. The advantages and potential of the Q. ilex phytomass as a biofilter of toxic trace metals, the scope and need for enhancing the efficiency of the Q. ilex phytomass as an adsorbent of metals are presented.

Journal Article↗
PubMed1999

Plant diversity and productivity experiments in european grasslands

At eight European field sites, the impact of loss of plant diversity on primary productivity was simulated by synthesizing grassland communities with different numbers of plant species. Results differed in detail at each location, but there was an overall log-linear reduction of average aboveground biomass with loss of species. For a given number of species, communities with fewer functional groups were less productive. These diversity effects occurred along with differences associated with species composition and geographic location. Niche complementarity and positive species interactions appear to play a role in generating diversity-productivity relationships within sites in addition to sampling from the species pool.

Journal Article↗
PubMed1999

Dendroanalysis: a tool for biomonitoring environmental pollution?

Trees of temperate regions usually form visible annual growth rings, which can be dated accurately. It is therefore possible to collect wood samples of different age and analyse their heavy metals content in order to get a chronological record of trace elements pollution in the tree's environment. This method of retrospective biomonitoring was called dendroanalysis. A basic assumption of dendroanalysis is the stability of the mineral distribution patterns, i.e. once the elements are stored, no significant mobility should occur. Additionally, neighbouring trees growing in the same environment should show similar radial element patterns. While some studies presented good correlations between radial distributions of heavy metals in tree rings and temporal records of pollution from industry or traffic, others failed in using dendroanalysis as a chronological record of pollution. Probably some elements can move at a certain rate in radial direction through the ray parenchyma cells. In this way the radial element distributions are subsequently changed. Growth rates of tree rings can also influence the concentrations of elements in wood. During periods of slow growth higher concentrations of elements can be found in the wood. Therefore, radial distribution patterns of heavy metals in tree rings should be used with caution as a tool for retrospective biomonitoring of environmental pollution.

Air Pollution↗
PubMed1995

Giant diverticulum of the sigmoid colon.

While diverticulosis of the colon is a relatively common disease, a solitary giant diverticulum (GD) of the sigmoid is rare. Although there exist some theories about the formation of a GD, none is really conclusive. Symptoms are similar to diverticular disease, and diagnosis is easy with the aid of radiology. Early surgical treatment is necessary since the complication rate is high (19%).

Diagnosis, Differential↗
PubMedDate not supplied

Genetic diversity of the Macaronesian leafy liverwort Porella canariensis inferred from RAPD markers.

Plant colonization of the North Atlantic raises the intriguing question of the relationships between extant island species with their continental counterparts (European, African, and American), which may provide clues to past geographic distribution and colonization history. It has been suggested that during past glaciations, many plant species with typical Mediterranean distributions survived in the Atlantic islands that belong to what is today known as Macronesia. We used random amplified polymorphic DNA (RAPD) markers to study 12 populations of the liverwort Porella canariensis partly covering its present-day distribution (Azores, Madeira, Canary and Cape Verde Islands, and Iberian Peninsula). Unweighted pair-group (UPGMA) and principal component (PCO) analyses showed a similar geographical pattern that suggested a close relationship between Iberian populations and those from the Canaries and Cape Verde Islands. Populations from Madeira had more genetic variation than those from the Azores, a result from either a richer diversity of habitats in Madeira, which prompted more population diversification, successive colonization waves from different origins, or an older colonization of Madeira. The data show that continuous patches of liverworts are often comprised of more than one individual. Finally, RAPDs can be used to investigate intraspecific diversity within a comparatively large geographic area and, with utmost care, can be used to infer a historic context to explain the patterns observed.

Atlantic Islands↗