[Show abstract][Hide abstract] ABSTRACT: The potentially hazardous effects of rock wastes disposed at open pit in three different areas (Pr: Ore processing; Wr: Waste rock and Bd: Border) of an abandoned copper mine were evaluated in this study, with emphasis on acid drainage generation, metal contamination and copper geochemical dynamics in soils. Samples of waste rock were analyzed by Energy dispersive X-ray fluorescence (XRF), scanning electron microscopy with microanalysis (SEM-EDS) and X-ray diffraction (XRD). Soil samples were analyzed to determine the total metal contents (XRF), mineralogy (XRD), pH (H2O and H2O2), organic and inorganic carbon, % of total N, S and P, particle size, and a sequential extraction procedure was used to identify the different copper fractions. As a result of the prevalence of carbonates over sulphides in the wastes, the soil pH remained close to neutral, with absence of acid mine drainage. The geochemical interaction between these mineral phases seems to be the main mechanism to release Cu(2)(+) ions. Total Cu in soils from the Pr area reached 11,180mg.kg(-1), while in Wr and Bd areas the values reached, on average, 4683 and 1086mg.kg(-1), respectively, indicating a very high level of soil contamination. In the Pr and Wr, the Cu was mainly associated with carbonates and amorphous iron oxides. In the Bd areas, the presence of vegetation has influenced the geochemical behavior of copper by increasing the dissolution of carbonates, affecting the buffer capacity of soils against sulphide oxidation, reducing the pH levels and enhancing the proportion of exchangeable and organic bound Cu. The present findings show that the use of plants or organic amendments in mine sites with high concentration of Cu carbonate-containing wastes should be viewed with caution, as the practice may enhance the mobilization of copper to the environment due to an increase in the rate of carbonates dissolution.
Science of The Total Environment 09/2014; 500-501C:91-102. · 3.16 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Greenhouse pot experiments were conducted over 13 months to evaluate the effect of two amendment mixture doses (30 and 75 Mg/ha) on the geochemical dispersion of trace elements by leaching hazardous mine wastes from the São Domingos mine. Mineralogical evolution of these materials was also evaluated. Amendment mixtures containing solid wastes from agriculture (plant remains + strawberry substrate and rockwool used for the strawberry crop) and from distillation of Ceratonia siliqua L. and Arbutus unedo L. fruits were used to improve the chemical characteristics of leachates from sulfide mine wastes. Sulfide mine wastes had acidic characteristics, as well as high electrical conductivity and total element concentrations (g/kg; Al: 54.8–61.2; Fe: 104.0–110.0; Pb: 9.0–13.8; S: 63.6–68.0; As: ≈ 1). These features contributed to the large capacity for leaching of hazardous elements during, at least, the first four months of incubation. In the seventh month of incubation, there was a significant decrease in the leachate concentration of the majority of hazardous elements. The addition of amendments minimised trace element dispersion in leachate percolation during the first seven months (25 to 99% reduction compared to control, depending on the element and sampling period). However, the leachate characteristics were not influenced by amendment doses and no significant differences were observed in leachate composition (control and amended treatments) after 13 months. Amendment application led to differences between the solid phases of the efflorescent salts formed on the surface of the control and the amended treatments. The efflorescent salts contained very soluble aluminium sulfates, together with alunite–jarosite-group solid phases in amended samples, and copiapite-group solid phases in control. In the core materials (5 to 10 cm in depth), the mineralogy was similar in both control and amended samples. The presence of various stable solid phases from alunite–jarosite-group, such as jarosite and beudantite (mainly in deeper materials), can explain the low concentrations of trace elements in the leachates after thirteen months.
Geoderma 08/2014; s 226–227:188–203. · 2.35 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Se determinó la capacidad máxima de adsorción de fosfatos en un Tecnosol con propiedades ándicas. El Tecnosol fue diseñado, formulado y elaborado para reducir las concentraciones de P en sistemas acuáticos, contribuyendo a la reducción de la eutrofización y sus consecuencias nocivas. Después de seis meses sumergido en aguas del río Limia, la capacidad de adsorción del Tecnosol apena disminuyó. Por este motivo, se decidió realizar un ensayo de adsorción en laboratorio y someter el Tecnosol a ciclos de aporte de P. Para simular condiciones naturales en aguas eutrofizadas, los ensayos se realizaron con concentraciones de 1 mg.L-1, mientras que para monitorizar la respuesta a condiciones extremas se añadieron también dosis de 100 mg.L-1 en paralelo. Para contrastar el efecto que tuvo ese periodo sumergido en agua sobre el Tecnosol se utilizaron dos grupos de muestras: el Tecnosol usado y el mismo Tecnosol conservado sin uso. La máxima de adsorción del Tecnosol sin usar puede llegar a 7500 mg.kg-1.
[Show abstract][Hide abstract] ABSTRACT: Wastewater discharge from shrimp farming is one of the main causes of eutrophication in mangrove ecosystems. We investigated the phosphorus (P) geochemistry in mangrove soils affected by shrimp farming effluents by carrying out a seasonal study of two mangrove forests (a control site (CS); a site affected by shrimp farm effluents (SF)). We determined the soil pH, redox potential (Eh), total organic carbon (TOC), total phosphorus (TP), and dissolved P. We also carried out sequential extraction of the P-solid phases. In SF, the effluents affected the soil physicochemical conditions, resulting in lower Eh and higher pH, as well as lower TOC and higher TP than in CS. Organic P forms were dominant in both sites and seasons, although to a lesser extent in SF. The lower TOC in SF was related to the increased microbial activity and organic matter decomposition caused by fertilization. The higher amounts of P oxides in SF suggest that the effluents alter the dominance of iron and sulfate reduction in mangrove soils, generating more reactive Fe that is available for bonding to phosphates. Strong TP losses were recorded in both sites during the dry season, in association with increased amounts of exchangeable and dissolved P. The higher bioavailability of P during the dry season may be attributed to increased mineralization of organic matter and dissolution of Ca-P in response to more oxidizing and acidic conditions. The P loss has significant environmental implications regarding eutrophication and marine productivity.
Environmental Monitoring and Assessment 05/2014; · 1.68 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to identify metal-tolerant plants with potential application in phytoremediation strategies. For this we evaluated the distribution and chemical fractionation of heavy metals in soils and their accumulation or exclusion by native plant species growing in an abandoned Pb/Zn mine in NW Spain. Mine-soils (I = 0–20 cm, II = 20–40 cm) and shoots of the dominant plants were sampled at 39 sampling points in a (100 m × 100 m) regular grid at two sites (mine zone (MZ) and tailing ponds (TP)).
Total metal contents in mine-soils presented a high heterogeneity and the principal contaminants were Cd, Hg, Pb and Zn (in agreement with the mineralogy of the site). Total concentrations varied from 2 to 95 mg Cd kg−1, 0.2 to 24.8 mg Hg kg−1, 46 to 6100 mg Pb kg−1, and 340 to 52,000 mg Zn kg−1. Soil metal distribution did not vary significantly with depth, but total and EDTA-extractable metal concentrations were higher in MZ than TP. On the other hand, the relative extractability of soil metals (EDTA-extractable concentration expressed as a % of total concentration) was higher in TP. The residual fraction was dominant for Co, Cr, Cu, and Ni, representing generally more than 50% of total concentration. Pb was preferentially associated with the oxidisable fraction, followed by the acid-extractable fraction. Both Cd and Zn were amply represented by the oxidisable, reducible and acid-extractable fractions. All the studied plant species were metal-tolerant (pseudometallophytes), although differences were found between species. Significant differences were found in plant accumulation of Cd and primarily, Zn. Cytisus scoparius and C. multiflorus were efficient metal-excluding species, and could be interesting candidates for phytostabilisation techniques and/or revegetation of heavily contaminated soils. Salix atrocinerea, presented significantly higher concentrations of Zn in its aerial biomass (543 ± 108 mg Zn kg−1) than the remaining species and bioconcentration factors (BCF) of up to 2.35 for Zn and 4.17 for Cd, respectively. This population could be interesting in the phytoextraction of low to moderately-contaminated soils.
[Show abstract][Hide abstract] ABSTRACT: Gossan wastes represent one of the most hazardous mine wastes in several mining areas from the Iberian Pyrite Belt. Phytostabilization of mine wastes with Cistus ladanifer L. could be a good option, but its growth and germination are impaired by substrata conditions. To overcome these limitations, application of organic and inorganic amendments may speed up the growth of C. ladanifer while improving the mine wastes. This study evaluated the simultaneous influence of different application rates of amendments and growth of C. ladanifer on chemical and biological properties of gossan wastes.
Amendments used were mixtures (30, 75, 150 Mg/ha, 1:1:1) of rockwool, agriculture wastes and wastes from liquor distillation of Arbutus unedo L. fruits. A microcosm assay with four treatments was carried out (control and three amended treatments) under controlled conditions in a greenhouse during 505 days. C. ladanifer was sown in half of the pots from each treatment while the remainder was left bare.
Gossan wastes had large total concentrations of several elements (g/kg; Al: 24.8, As: 3.03, Cu: 0.23, Pb; 9.21) whereas the available concentrations of these elements were small (< 5.7 % of total). The amendments applied (in particular at 75 and 150 Mg/ha) improved the structure and increased the water-holding capacity, pH and nutrients concentrations in the available fraction of the gossan materials. They also led to increases in dehydrogenase and β-glucosidase activities and in plant growth (plant cover, plant height, length of young leaves, fresh biomass). In addition, plants from amended treatments presented lower concentrations of hazardous elements in shoots than plants from unamended control. The presence of the plant did not increase the available concentrations of hazardous elements in wastes, except for As when 150 Mg/ha of amendments were applied.
Phytostabilization with C. ladanifer using a Technosol, resulting from the application of the studied amendments at 75 and 150 Mg/ha to gossan materials seems a promising solution for rehabilitation of this type of mine wastes.
Journal of Geochemical Exploration 04/2014; · 1.95 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A semi-arid mangrove estuary system in the northeast Brazilian coast (Ceará state) was selected for this study to (i) evaluate the impact of shrimp farm nutrient-rich wastewater effluents on the soil geochemistry and organic carbon (OC) storage and (ii) estimate the total amount of OC stored in mangrove soils (0–40 cm). Wastewater-affected mangrove forests were referred to as WAM and undisturbed areas as Non-WAM. Redox conditions and OC content were statistically correlated (P b 0.05) with seasonality and type of land use (WAM vs. Non-WAM). Eh values were from anoxic to oxic conditions in the wet season (from −5 to 68 mV in WAM and from b40 to N 400 mV in Non-WAM soils) and significantly higher (from 66 to 411 mV) in the dry season (P b 0.01). OC con-tents (0–40 cm soil depth) were significantly higher (P b 0.01) in the wet season than the dry season, and higher in Non-WAM soils than in WAM soils (values of 8.1 and 6.7 kg m −2 in the wet and dry seasons, respectively, for Non-WAM, and values of 3.8 and 2.9 kg m −2 in the wet and dry seasons, respectively, for WAM soils; P b 0.01). Iron partitioning was significantly dependent (P b 0.05) on type of land use, with a smaller degree of pyritization and lower Fe-pyrite presence in WAM soils compared to Non-WAM soils. Basal respiration of soil sediments was significantly influenced (P b 0.01) by type of land use with highest CO 2 flux rates measured in the WAM soils (mean values of 0.20 mg CO 2 h −1 –g −1 C vs. 0.04 mg CO 2 h −1 –g −1 C). The OC storage reduction in WAM soils was potentially caused (i) by an increase in microbial activity induced by loading of nutrient-rich effluents and (ii) by an increase of strong electron acceptors [e.g., NO 3 − ] that promote a decrease in pyrite concentration and hence a reduction in soil OC burial. The current estimated OC stored in mangrove soils (0–40 cm) in the state of Ceará is approximately 1 million t.
[Show abstract][Hide abstract] ABSTRACT: Bacterial and archaeal community structures and diversity of three different sedimentary environments (BH1A, BH2A and BH3A) in the acid pit lake of a chalcopyrite mine at Touro (Spain) were determined by 16S rRNA gene PCR-DGGE and sequencing of clone libraries. DGGE of bacterial and archaeal amplicons showed that the sediments harbor different communities. Bacterial 16S rRNA gene sequences were assigned to Acidobacteria, Actinobacteria, Cyanobacteria, Planctomycetes, Proteobacteria, Chloroflexi and uncultured bacteria, after clustering into 42 operational taxonomic units (OTUs). OTU 2 represented approximately 37, 42 and 37 % of all sequences from sediments BH1A, BH2A and BH3A, respectively, and was phylogenetically related to uncultured Chloroflexi. Remaining OTUs were phylogenetically related to heterotrophic bacteria, including representatives of Ferrithrix and Acidobacterium genera. Archaeal 16S rRNA gene sequences were clustered into 54 OTUs. Most of the sequences from the BH1A sediment were assigned to Euryarchaeota, whereas those from BH2A sediment were assigned to Crenarchaeota. The majority of the sequences from BH3A sediment were assigned to unclassified Archaea, and showed similarities to uncultured and unclassified environmental clones. No sequences related to Acidithiobacillus and Leptospirillum, commonly associated with acid mine drainage, were detected in this study.
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to evaluate the chemical characteristics and ecotoxicity of a mine soil developed on gossan materials and amended with hydrophilic polyacrylate polymers after a growth cycle of Spergularia purpurea. Different acute bioassays (Daphnia magna immobilization; microalgae growth inhibition; germination and growth of lettuce and oat) were carried out with simulated leachates, pore water and soil samples. The germination and growth of native shrubs (Cistus ladanifer and Lavandula sampaioana) were also evaluated in the lysimeters where S. purpurea had grown. The soil had high total concentrations (g/kg) of Al (3.50-8.60), As (2.55-2.73), Cu (0.13-0.91) and Pb (4.48-6.16). However, the percentages of elements in aqueous extracts (simulating leachates, pore water, and the conditions of the rhizosphere soil) were small when compared to their total soil concentrations (less than 9% except for Na in leachates). Growth of S. purpurea and other natural colonization of plant species (Poaceae, Fabaceae and Asteraceae families) improved chemical characteristics but the application of the polyacrylate polymers contributed to a further improvement of soil quality. However, this was not sufficient to ensure the growth of a large number of shrubs despite a great germination rate. Among the several species used on the ecotoxicological assessment, the D. magna test was the only bioassay that showed a clear toxicity of soil leachates, suggesting the importance of using several ecotoxicological tests to assess the environmental risk of soil contamination and its rehabilitation. Although the studied soil can be considered contaminated taking into account the total soil concentrations of Al, As, Cu and Pb, the low concentrations of the same chemical elements in extractable solutions, that simulated the fractions really available for organisms, did not demonstrate a substantial toxic effects in the organisms and, consequently, negative impact on the environment.
Science of The Total Environment 06/2013; 461-462C:360-370. · 3.16 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The soil organic matter (SOM) extracted under different vegetation types from a Brazilian mangrove (Pai Matos Island, São Paulo State) and from three Spanish salt marshes (Betanzos Ría and Corrubedo Natural Parks, Galícia, and the Albufera Natural Park, Valencia) was investigated by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The chemical variation was larger in SOM from the Spanish marshes than in the SOM of the Brazilian mangroves, possibly because the marshes included sites with both tidal and nontidal variation, whereas the mangrove forest underwent just tidal variation. Thus, plant-derived organic matter was better preserved under permanently anoxic environments. Moreover, given the low number of studied profiles and sedimentary¿vegetation sequences in both areas, depth trends remain unclear. The chemical data also allow distinction between the contributions of woody and nonwoody vegetation inputs. Soil organic matter decomposition was found to cause: (i) a decrease in lignin contents and a relative increase in aliphatics; (ii) an increase in short-chain aliphatics at the expense of longer ones; (iii) a loss of odd-over-even dominance in alkanes and alkenes; and (iv) an increase in microbial products, including proteins, sterols, short-chain fatty acids, and alkanes. Pyrolysis-gas chromatography/mass spectrometry is a useful tool to study the behavior and composition of SOM in wetland environments such as mangroves and salt marshes. Additional profiles need to be studied for each vegetation type, however, to improve the interpretability of the chemical data
Soil Science Society of America Journal 02/2013; Ferreira, Fernando Perobelli(73):841-851. · 1.82 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The analysis of phytolith assemblages is an important method in studies that uses the soil as an environmental record in order to reconstruct the paleoclimatic conditions. Despite being underused in soil science, this technique is used complementary to the analysis of pollen and other microfossils, as well as to evaluate silicon reserves in the soil. Currently, there are several concentration methods for phytolith extraction from sediments, soils, and paleosols. Most were developed and applied to materials of temperate zones or hydromorphic environments. Few have been conducted in tropical soils where oxides and hydroxides of iron and aluminum, as well as organic matter that often blankets the soil matrix, are common and hamper the extraction, the observation and identification of phytoliths, compromising the morphological analysis and quantification of phytolith assemblage in soils. In this paper, three methods of pre-treatment for the removal of the coating of silt and sand particles were applied to samples of an Oxisol (Humic Hapludox) in order to compare the cleaning efficiency, integrity and number of phytoliths. The first method consisted of the oxidation of soil organic matter and of an acid hydrolysis for the removal of carbonates and oxides. In the second method, the dominant process was the reduction of iron using a combination Dithionite-Citrate-Sodium Bicarbonate. In the third method, only acetate and sodium dithionite dissolved in water was used. Overall, Method 1 was the most aggressive to phytoliths and proved less efficient and more selective in phytolith extraction. Methods 2 and 3 were similar in the pre-treatment of samples. Method 2 allows the conservation of greater variety and number of phytoliths, and smaller quantities of other particles. Method 3 is relatively inexpensive and faster because it uses fewer chemicals and centrifugation procedures.
Quaternary International 02/2013; 287:56-62. · 2.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The potential of soils as a sink of atmospheric carbon and the implications related to mitigate greenhouse-gas emissions are well recognized. The raising of tree crops on agricultural soils can augment soil-carbon sequestration more than do other agricultural uses such as corn crops. Thus, 6 plots with different durations of use as poplar plantation (5, 10, 20, 30, 50, and 100 years) were studied in comparison with 6 adjacent plots with corn crop. The carbon pool in poplar-plantation soils was positively correlated to the time of use at the three soil depths studied (0–20, 20–50, and 50–100 cm), the mean annual increase being 1.16 Mg C ha−1 year−1. Poplar-plantation soils also increased the total carbon content in a more effective way because the duration of use was also correlated with the most recalcitrant carbon forms. Therefore, land-use change from corn crops to poplar-plantation soils is economically profitable as well as positive both for the total organic-carbon pool as well as for the efficiency of carbon sequestration by the increase of non-oxidizable forms in the soil.
Soil and Tillage Research 01/2013; 130:1-6. · 2.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose To characterise soil humic acids (HAs) extracted from Spanish marshes formed under different vegetation types (Spartina maritima (GSp), Juncus maritimus (GJc), Phragmites australis (GPh), and Scirpus maritimus (VSc)), soil depths (0–20, 20–40 and 40–60 cm), physiographic position (low and high marshes), wetland types (salt marshes and lagoons) and environmental conditions (Atlantic and Mediterranean coast). Material and methods Soil samples were collected in five Spanish marshes, three on the Galicia province and two on the Valencia province. Humic acids were extracted and their elemental composition, semiquinone-type free radical (SFR) content, FTIR and CPMAS 13 C NMR spectra determined. Total carbon (TC), total nitrogen (TN), total sulphur (TS), CaCO 3 content, and field pH and Eh (mV) in the marsh soils sampled were also measured. Results and discussion The field pH and Eh values were typical of coastal areas submitted to periodic inunda-tions and the highest TC, TN and TS contents were found in the soil of lagoon marshes as an effect of physiographic position and wetland type. The HAs, in general, were highly aliphatic and exhibited a low SFR content, which suggests a low humification degree of the SOM formed in the studied areas. This is a result of the anaerobic decomposition to which SOM is submitted and the high input of plant-derived organic matter (OM) by vegetation. However, among the studied sites low salt marsh and subsurface layer of the high salt marsh showed higher SFR content, simpler FTIR spectra, higher lignin degradation and lower O-alkyl C/alkyl C ratio than the lagoon marshes, thus suggesting the pres-ence of a more humificated SOM in these sites. Conclusions From the different factors analysed, only phys-iographic position (low versus high salt marshes) and wet-land type (marshes versus lagoons) caused variations in the HAs characteristics, because as the studied soils are under anaerobic conditions, they control the exportation of plant-derived OM and the allochthonous OM contribution in the studied areas.
Journal of Soils and Sediments 01/2013; 13(253):264. · 1.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The study area, Mount Martial, is located in the South of Argentina, in
the Tierra de Fuego province (54°S, 68°W). The climate in Tierra
del Fuego is temperate-cold and humid, with a strong and markedly
seasonal oceanic influence. The mean air temperature that we recorded in
the study zone, at 1050 m above sea level, between February 2005 and
January 2010 was -1.9° C, with an absolute maximum of 12.5° C
and an absolute minimum of -12.8° C. Although we have no rainfall
data, in Ushuaia, which is close to sea level, the mean annual rainfall
for 1961-1970 was 550 mm; however, it would be inaccurate to
extrapolate this value given the marked variability in precipitation
favoured by the relief. Biogeographically, the area is included in the
so-called "Andean Desert", which is almost barren of large plants and
with poor vegetable cover. At 800 a.s.l., the vegetation consists of
shrubs of specialised taxons such as Bolax gummifera, Moschopsis
rosulata and Saxifraga magellanica. In the present study, samples of
Bolax gummifera rhizosphere (Umbelliferae), bulk soil and subsurface
soils (>5 cm to rock layer) were collected from a small homogeneous
area (≈500m2). The soils were characterized by analysis of pH (H2O
and KCl), electrical conductivity, total organic carbon, total nitrogen,
organic carbon, iron extracted with sodium pyrophosphate, and particle
size. Sequential extraction of Fe in the samples was also carried out to
determine the following fractions: F1: exchangeable fraction (extracted
with 1M MgCl2), F2: amorphous Fe oxyhydroxides (extracted with sodium
ascorbate-citrate buffering to pH 8 with sodium bicarbonate), F3:
crystalline Fe oxyhydroxides (extracted with 0.11 sodium citrate+ sodium
bicarbonate +3 g of sodium dithionite), and F4: organic Fe (extracted
with 0.02M HNO3+30%H2O2 at 85°C) and bioavailability nutrients
(soluble in Mehlich 3 extratant). The results obtained for the basic
physicochemical characteristics of the soils revealed some differences
between samples. Thus, Although these are poorly developed soils,
significant differences were foundAlthough being incipient soils,
significant differences were found in relation to the effect of the
rhizosphere on soil properties. For example, the total organic C was 8
times higher and the total nitrogen and C pyrophosphate were 4 times
higher in the rhizosphere than in the bulk soil. The results of the
sequential extraction of Fe and bioavailability nutrients, such Ca, Mg,
K and Fe, also revealed significant differences between rhizosphere and
bulk soil, whereas the deeper samples (> 5 cm) displayed intermediate
characteristics. These results are consistent with the hypothesis that
plants affect the biogeochemical processes in soils by accelerating
weathering processes. This aspect may be of particular importance within
the context of global climate change, as higher temperatures will favour
expansion of vegetation and at the same time the flow of nutrients
towards oceans and lakes, which may have a direct effect on primary
EGU General Assembly Conference Abstracts; 01/2013
[Show abstract][Hide abstract] ABSTRACT: Persistent organic pollutants (POPs) are within the most dangerous pollutants released into the environment by human activities. Due to their resistance to degradation (chemical, biological or photolytic), it is critical to assess the fate and environmental hazards of the exchange of POPs between different environmental media. System Dynamics enables to represent complex systems and analyze their dynamic behavior. It provides a highly visual representation of the structure of the system and the existing relationships between the several parameters and variables, facilitating the understanding of the behavior of the system. In the present study the fate of γ-hexachlorocyclohexane (lindane) in a contaminated soil was modeled using the Vensim® simulation software. Results show a gradual decrease in the lindane content in the soil during a simulation period of 10years. The most important route affecting the concentrations of the contaminant was the biochemical degradation, followed by infiltration and hydrodynamic dispersion. The model appeared to be highly sensitive to the half-life of the pollutant, which value depends on environmental conditions and directly affects the biochemical degradation.
[Show abstract][Hide abstract] ABSTRACT: O objectivo deste trabalho foi avaliar, a médio prazo, a eficiência de Tecnossolos formulados a partir de resíduos orgânicos/inorgânicos e materiais de escombreira ricos em sulfuretos da mina de São Domingos, na redução da contaminação multielementar nos lixiviados. A escombreira apresentava características químicas extremas, tal como os seus lixiviados (extracção DIN 38414-S4): pH <2.6 e elevadas concentrações de aniões e catiões, muitos deles potencialmente gravosos para o ambiente. Os Tecnossolos foram eficientes na diminuição da maioria dos elementos químicos nos lixiviados, principalmente até aos sete meses de ensaio, não havendo diferenças significativas entre as doses de resíduos orgânicos/inorgânicos incluídos nos Tecnossolos.
III Seminário Luso-Brasileiro em Ciências do Ambiente e Empresariais, Lins – Brasil; 10/2012
[Show abstract][Hide abstract] ABSTRACT: The rhizosphere is a narrow zone of soil influenced by plant root and their exudates and its extent varies with soil type, plant species, age and many other factors. The rhizosphere microenvironment therefore has different characteristics from those of bulk soils. In the present study, the physicochemical parameters, exchangeable micronutrients (extracted with 1M NH4Cl), available micronutrients (extracted with Mehlich-III: Fe, Mn, Cu, and Zn), toxic metals (Cr, Pb, Ni, Cd), the Fe associated with the organic matter (extracted with Na-pyrophosphate) and the poorly crystalline Fe (extracted with 0.2M oxalic acid) were studied in the bulk soil and in the rhizosphere of the spontaneous vegetation growing at an abandoned copper mine. The natural vegetation colonising the mine dump included two species of Ericaceae (Erica cinerea, Calluna vulgaris) and Salix atrocinerea, whereas only the first two grew on the mine slope.The results showed that plants influence the physicochemical conditions of the rhizosphere, although not all in the same way. Thus the pH of the rhizosphere of the ericaceous species was extremely low, approximately 2–3units lower than the pH of the bulk soil, whereas the pH of the Salix rhizosphere remained close to the respective bulk soil, which has a pH of 6.6. Furthermore, the concentration of organic matter was higher in the rhizosphere than in the bulk soil. In general the same pattern was observed for the most labile fractions of the micronutrients and toxic metals, with higher concentrations in the rhizosphere than in the bulk soil. However, there were clear differences between the ericaceous species and Salix, which prevents general conclusions being reached about the processes to which trace metals are submitted in the rhizosphere. On the other hand, although the elements under study are included in the term trace metals, they display different geochemical behaviour. Thus the exchangeable fraction was clearly correlated with the TOC for all micronutrients except Cu, presumably because the organic matter selectively adsorbs this element, thereby reducing its mobility. Finally, as regards the potential toxicity, only the concentrations of Cu and Fe surpassed the limits above which phytotoxicity may occur, while toxic metals were present at very low concentrations.
Journal of Geochemical Exploration 01/2012; 112:84-92. · 1.95 Impact Factor