[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. · 3.26 Impact Factor
[show abstract][hide abstract] ABSTRACT: Cistus ladanifer is considered a good option for phytostabilization of
mine wastes, composed of several materials, but its growth is very slow
due to substrata conditions (acidic pH, low fertility and water
availability, high total concentrations of hazardous elements). To
enhance the growth of C. ladanifer with application of organic/inorganic
amendments can be a strategy to speed up remediation. This study aimed
to evaluate the influence of different rates of amendments and C.
ladanifer growth on the improvement of chemical and biological
characteristics of gossan wastes. Composite samples of mining wastes
(gossan+host rocks) were collected at the São Domingos mine.
Amendments used were mixtures (30, 75, 150 Mg/ha) of rockwool,
agriculture wastes and wastes from liquor distillation obtained from
fruits of Arbutus unedo. Four treatments (n=6 replicates) were carried
out (control and three amended treatments) under controlled conditions
in a greenhouse. After one month of incubation at 70% of water holding
capacity, C. ladanifer was sown in half of the pots from each treatment
(n=3), and the other three pots remained in the same conditions without
plant. Chemical and biological characteristics of the wastes
(with/without plants) were analysed after incubation and fifteen months.
Gossan wastes had great total concentrations of several elements
(g/kg; Al: 24.8, As: 3.03, Cu: 0.23, Pb; 9.21) whereas in an extracting
solution (diluted solution of organic acids) these were small (0.5
units), fertility (Corganic, Pextractable, Ntotal) and dehydrogenase
activity of mine wastes, principally with the rate of 150 Mg/ha, even
after one month of incubation and after the plants be sown. In both
sampling periods (beginning/end of the experiment), Kextractable
concentrations increased only with the high application rates (control
and 30 Mg/ha treatment: 1.02-1.88 mg/kg; other amended treatments:
2.13-3.55 mg/kg). At the end of the experiment, the presence of the
plant increased Corganic and Pextractable concentrations, compared to
treatments without plants, reaching the highest values in the treatments
combining amendments and plants. After one month of incubation, the
dehydrogenase activities in wastes were more than twice in the amended
treatments (1.71-33.55 μg TPF g sample 16h-1, depending on amendments
application rate and sampling period). Nevertheless, wastes from
treatments with plants had higher dehydrogenase activities (9.66-33.55
μg TPF g sample 16h-1, depending on amendments application rate) than
in treatments using only amendments (4.98-22.30 μg TPF g sample
16h-1), but both were higher than control. The plants in control
presented lower fresh biomass than in amended treatments. Plants growth
in control was not sufficient to enhance dehydrogenase activity of mine
wastes (1.51 and 1.72 μg TPF g sample 16h-1, with/without plants,
respectively). The extractable nutrients (Ca, Fe, K, Mg, Mn, Zn)
increased with amendment application, an advantage for remediation
purposes. Although extractable Al, As, Na also increased in the same
treatments, they remained small. In contrast, extractable Cu and Pb
were, generally, lower in amended treatments than in control. The
presence of the plant did not increase the concentration of elemental in
the extractant solution.
[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 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 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 01/2013; 287:56-62. · 1.96 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: 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
[show abstract][hide abstract] ABSTRACT: Different analytical techniques were used to find the most reliable and economic method for determining the labile fraction of C in biochar. Biochar was produced from pine, poplar and willow (PI, PO and WI, respectively) at two temperatures (400 and 550 °C) and characterised using spectroscopic techniques [solid state 13 C nuclear magnetic resonance spectroscopy (NMR)], molecular markers [pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS)], thermogravimetry (TG), elemental composition and wet oxidation (potassium permanganate and potassium dichromate). Short term incubation (110 h) of an A horizon from an Umbrisol amended with the biochar samples at two doses (7.5 and 15 t ha À1) was also carried out to provide supplementary information on the influence of biochar–soil interaction on CO 2 evolution. Spectroscopic analysis demonstrated that the degree of biochar carbonisation was influenced by the type of feedstock and heating conditions and followed the order WI-400 < PI-400 $ WI-550 $ PO-400 < PO-550 < PI-550. The thermo-labile fraction of the biochar samples, estimated from TG, ranged between 21% and 49%. The fraction of total C oxidised with potassium permanganate (C per /C total) was <50 g kg À1 in all cases, whereas potassium dichromate (C dichro /C total) oxidation efficiency ranged between 180 and 545 g kg À1 . For each type of feedstock, the highest values of either chemically or thermally degradable C corresponded to the biochar produced at low temperature. Results indicate that low cost methodologies, such as dichromate oxidation and TG, reflected the degree of biochar carbonisa-tion, and could therefore be used to estimate the labile fraction of C in biochar.
[show abstract][hide abstract] ABSTRACT: The geochemical characteristics of coal cleaning rejects (CCR) in Santa Catarina State, Brazil, were investigated. Around 3.5 million ton/year of coal waste are dumped in Santa Catarina State. Coal beneficiation by froth flotation results in large amounts of CCR composed of coaly and mineral matter, the latter characterised by the occurrence of sulphide minerals and a broad array of leachable elements. The total and leachable contents of more than 60 elements were analysed. Atmospheric exposure promotes sulphide oxidation that releases substantial sulphate loads as well as Ca2+, K+, Mg2+, Cl- and Al3+. The metals with the most severe discharges were Zn, Cu, Mn, Co, Ni and Cd. Most trace pollutants in the CCR displayed a marked pH-dependent solubility, being immobile in near-neutral samples. The results highlight the complex interactions among mineral matter solubility, pH and the leaching of potentially hazardous elements.
Environmental Monitoring and Assessment 04/2011; 175(1-4):109-26. · 1.59 Impact Factor
[show abstract][hide abstract] ABSTRACT: The main objective of this research was to study the oxidizability of soil organic matter (SOM). Forty-one surface horizons of forest soils under Fagus sylvatica L. developed on different lithologies (limestones, sandstones, marlstones, and shales) were sampled. The oxidizability of SOM was assessed by reacting air-dried samples with 33 mmol/L of potassium permanganate for different incubation times (1, 3, 6, and 24 h). None of the soil properties analyzed (including organic C content and oxidizability of SOM) showed significant differences (P < 0.05) based on the lithology of the parent material. The amount of oxidized C (OCper) at each reaction time was strongly correlated to the initial organic C content of the soil (r2 > 0.850). The cumulative amount of OCper increased with time following an asymptotic trend that fitted to a power model (r2 > 0.700); oxidation rates showed that the first hour was the most reactive (0.069-0.094 g of C g−1 of soil h−1). On average, 9% of the total initial organic C was oxidized at 1 h, 12% at 3 h, 15% at 6 h, and 23% at 24 h, which are values comparable to those found in previous studies. Principal component analysis revealed that the samples were composed of two groups of soils. Both groups showed an increase in total soil organic C content (and oxidizability) with increasing contents of reactive soil colloids (clay and metal-SOM complexes) but had different slopes in their relationship to the scores of the first principal component, suggesting different dynamics.
[show abstract][hide abstract] ABSTRACT: In the present investigation, a study was undertaken to understand the origin of Fe-minerals presents in Brazilian coal mining and to understand the environmental implication and the chemical heterogeneity in the study area. Coal cleaning residue samples rich in clays, quartz, sulphides, carbonates, sulphates, etc. were sampled from Lauro Muller, Urussanga, Treviso, Siderópolis, and Criciúma cities in the Santa Catarina State and a total of 19 samples were collected and Mössbauer, XRD, SEM/EDX, and TEM analyses were conducted on the samples. The major Fe-minerals identified are represented by the major minerals chlorite, hematite, illite, and pyrite, while the minor minerals include, ankerite, chalcopyrite, goethite, hematite, jarosite, maghemite, magnetie, marcasite, melanterite, natrojarosite, oligonite, pyrrhotite, rozenite, schwertmannite, siderite, and sideronatrile. Pyrite is relatively abundant in some cases, making up to around 10% of the mineral matter in several samples. The sulphates minerals such as jarosite and others, probably represent oxidation products of pyrite, developed during exposure or storage.
Environmental Monitoring and Assessment 01/2011; 172(1-4):367-78. · 1.59 Impact Factor
[show abstract][hide abstract] ABSTRACT: PurposeThe present study was carried out to identify and quantify the aluminum species present in the bulk and rhizospheric soil
solution of the spontaneous vegetation colonizing the dump (Calluna vulgaris, Erica cinerea) and slope (C. vulgaris, E. cinerea, Salix atrocinerea) of an abandoned Cu mine in Touro (Galicia, NW Spain).
Materials and methodsTotal dissolved aluminum was speciated into reactive Al (Alr) and acid-soluble Al (Alsa). Acid-soluble aluminum comprises
colloids, polymers and/or organo-aluminum complexes, whereas Alr comprises non-labile monomeric aluminum (AlnL) and labile
monomeric aluminum (AlL). The latter fraction included Al3+, Al–OH complexes, Al–F complexes, and Al–SO4 complexes.
Results and discussionThe results show that Ericaceae modified the pH of the rhizosphere from 6.6 to 4.0 (C. vulgaris) in the slope, whereas S. atrocinerea only grew in close-to-neutral soil conditions and increased the rhizosphere pH by 0.8 units. The total concentration of Al
in the soil solution was low (<75μmol L–1) and was higher in the rhizosphere than in the bulk soil solution in all samples. Under Ericaceae, the Alr represented between
80% and 98% of the total Al in solution and the concentration was higher in the rhizosphere; under S. atrocinerea the Alsa was always higher than 80%, with higher concentrations in the rhizosphere. AlL predominated over AlnL in all samples.
The distribution of labile Al into different species depended on the pH and the concentration of labile Al: Al3+ predominated in all samples from the dump (>40% of the AlL) and in the C. vulgaris rhizosphere in the slope (>52% of the AlL); the Al–F complexes were more abundant in the E. cinerea rhizosphere in the slope (>40% of the AlL), and Al–OH complexes predominated in all samples associated with S. atrocinerea (>70%). In the mine dump, the Ca/AlL ratio changed from 0.07 (bulk soil) to higher than 1.4 in the root zone of the Ericaceae
thus decreasing the risk of toxicity by this element.
ConclusionsLabile aluminum is the prevailing fraction in all dump samples and in the rhizosphere of Ericaceae growing on the slope. Al3+ is the predominant species in the most acidic samples with the highest concentration of labile Al and the highest AlL/F ratio.
In areas where there may be a risk of Al toxicity, Ericaceae accumulated Ca in the vicinity of the roots, thus increasing the Ca/AlL ratio relative to that in the bulk soil and preventing
absorption of Al and the associated phytotoxicity.
–Fractionation and speciation of Al in soil solution–Mine soil–Rhizosphere–
Journal of Soils and Sediments 01/2011; 11(2):221-230. · 1.97 Impact Factor
[show abstract][hide abstract] ABSTRACT: Soil organic matter (SOM) in Alu-andic Andosols and Alu-humic Umbrisols is believed to accumulate because of the protection caused by binding to aluminium (Al). We investigated soils that differed in the abundance of organo-Al complexes to determine the effect of such binding on SOM chemistry. For this, the surface horizons of three types of acid soils in the Basque Country (northern Spain) under forest stands were studied: (i) Alu-andic Andosols (AND soils) on basalts and trachytes, (ii) Umbrisols or so-called 'aluminic'(ALU) soils also on basalts and trachytes and (iii) soils with a podzolizing trend (POD), on quartzites. Values of Al extractable with sodium pyrophosphate (Al p) in the surface horizons of these soils ranged between 8.5 and 13.1, 1.9 and 9.3, and 0.8 and 3.7 g kg −1 dry weight, for the AND, ALU and POD soils respectively. For POD and ALU soils, surface horizons were sampled at two depths, 0–5 and 5–20 cm, whereas the AND soils were sampled at different depths down to the B horizon. NaOH-extractable SOM from three AND soils, 12 ALU soils and 12 POD soils was studied by pyrolysis-gas chromatography/mass spectrometry. The POD soils had the largest loads of plant-derived markers (lignin, long-chain alkanes and alkenes, methyl ketones, fatty acids); SOM of the AND soils had the smallest amounts of plant-derived SOM and the largest amounts of microbial products (microbial sugars and N-compounds) of the soils studied. ALU soils had an intermediate pattern, as expected. The results indicate that the SOM of Alu-andic Andosols, developed from basalt and trachyte rocks, is essentially dissimilar to that of soils derived from quartz-rich parent material, under the same climate conditions and similar forest stands. The dominance of secondary (microbial-derived) SOM in Alu-andic Andosols, also observed in previous research on Sil-andic Andosols (these are dominated by short-range ordered Si compounds in contrast to the dominance of organo-Al complexes in Alu-andic Andosols), reveals the small contribution of primary (plant-derived) material to SOM in soils with andic properties.
European Journal of Soil Science 01/2011; · 2.65 Impact Factor