Phytoextraction of heavy metals from mine soils using hyperaccumulator plants.

Phytoextraction is an environmental-friendly and cost-effective technology that uses metal hyperaccumulator plants to remove heavy metals from soils. The metals are absorbed by the roots, transported and accumulated in the aerial parts of the plants, which can be harvested and eliminated. The aim of this work was to study some hyperaccumulator species that could be useful to decontaminate mine soils and also to investigate the bioavailability and uptake of these metals by plants with the addition of organic amendments. Pot experiments were performed with soil samples collected from two mining areas in the north of Madrid, where there was an intense mining activity more than 50 years ago. Three species (Thlaspi arvense, Brassica juncea and Atriplex halimus) were grown under controlled conditions in pots filled with contaminated soils mixed with 0 Mg, 30 Mg and 60 Mg per hectare of two different organic amendments: a commercial compost made of pine bark, peat and wood fiber and other made of horse and sheep manure and wood fiber. Plants were harvested at the end of their crop cycle and were digested in order to measure metal concentration (Zn, Cu and Cd) in roots and shoots. Highest plant metal concentration was observed in pots treated with pine bark amendment and with pure soil due to an increase in metal bioavailability with decreasing pH. Also in those treatments the total plant biomass was lower, even some plants could not germinate. On the contrary, there was a lower metal concentration in plant tissues of pots with manure because its higher pH whereas plant growth was significantly larger so there was an incresing amount of metals removed from soil by plants. Comparing the three species results indicate a higher total metal uptake in A. halimus than B. juncea and T. arvense. In conclusion, results show that pH affects metal bioavailability and uptake by hyperaccumulator plants. Addition of organic amendments could be a successful technique for stabilization of metals in contaminated soils.

Bioavailability and extraction of heavy metals from contaminated soil by Atriplex halimus

Pot experiments were performed to evaluate the phytoremediation capacity of plants of Atriplex halimus grown in contaminated mine soils and to investigate the effects of organic amendments on the metal bioavailability and uptake of these metals by plants. Soil samples collected from abandoned mine sites north of Madrid (Spain) were mixed with 0, 30 and 60 Mg ha?1 of two organic amendments, with different pH and nutrients content: pine-bark compost and horse- and sheep-manure compost. The increasing soil organic matter content and pH by the application of manure amendment reduced metal bioavailability in soil stabilising them. The proportion of Cu in the most bioavailable fractions (sum of the water-soluble, exchangeable, acid-soluble and Fe?Mn oxides fractions) decreased with the addition of 60 Mg ha?1 of manure from 62% to 52% in one of the soils studied and from 50% to 30% in the other. This amendment also reduced Zn proportion in water-soluble and exchangeable fractions from 17% to 13% in one of the soils. Manure decreased metal concentrations in shoots of A. halimus, from 97 to 35 mg kg?1 of Cu, from 211 to 98 mg kg?1 of Zn and from 1.4 to 0.6 mg kg?1 of Cd. In these treatments there was a higher plant growth due to the lower metal toxicity and the improvement of nutrients content in soil. This higher growth resulted in a higher total metal accumulation in plant biomass and therefore in a greater amount of metals removed from soil, so manure could be useful for phytoextraction purposes. This amendment increased metal accumulation in shoots from 37 to 138 mg pot?1 of Cu, from 299 to 445 mg pot?1 of Zn and from 1.8 to 3.7 mg pot?1 of Cd. Pine bark amendment did not significantly alter metal availability and its uptake by plants. Plants of A. halimus managed to reduce total Zn concentration in one of the soils from 146 to 130 mg kg?1, but its phytoextraction capacity was insufficient to remediate contaminated soils in the short-to-medium term. However, A. halimus could be, in combination with manure amendment, appropriate for the phytostabilization of metals in mine soils.

Phytoextraction of heavy metals from mine soils using hyperaccumulator plants

The aim of this work was to study some hyperaccumulator species that could be useful to decontaminate mine soils and also to investigate the bioavailability and uptake of these metals by plants with the addition of organic amendments. Pot experiments were performed with soil samples collected from two mining areas in the north of Madrid, where there was an intense mining activity more than 50 years ago. Three species (Thlaspi arvense, Brassica juncea and Atriplex halimus) were grown under controlled conditions in pots filled with contaminated soils mixed with 0 Mg, 30 Mg and 60 Mg per hectare of two different organic amendments: a commercial compost made of pine bark, peat and wood fiber and other made of horse and sheep manure and wood fiber. Plants were harvested at the end of their crop cycle and were digested in order to measure metal concentration (Zn, Cu and Cd) in roots and shoots. Highest plant metal concentration was observed in pots treated with pine bark amendment and with pure soil due to an increase in metal bioavailability with decreasing pH. Also in those treatments the total plant biomass was lower, even some plants could not germinate. On the contrary, there was a lower metal concentration in plant tissues of pots with manure because its higher pH whereas plant growth was significantly larger so there was an incresing amount of metals removed from soil by plants. Comparing the three species results indicate a higher total metal uptake in A. halimus than B. juncea and T. arvense. In conclusion, results show that pH affects metal bioavailability and uptake by hyperaccumulator plants. Addition of organic amendments could be a successful technique for stabilization of metals in contaminated soils.

Effects of sheep and horse manure and pine bark amendments on metal distribution and chemical properties of contaminated mine soils.

Mine soils usually contain large levels of heavy metals and poor fertility conditions which limit their reclamation and the application of phyto-remediation technologies. Two organic waste materials (pine bark compost and sheep and horse manure compost), with different pHs and varying degrees of humification and nutrient contents, were applied as amendments to assess their effects on copper (Cu) and zinc (Zn) bioavailability and on fertility conditions of mine soils. Soil samples collected from two abandoned mining areas near Madrid (Spain) were mixed with 0, 30 and 60 t ha?1 of the organic amendments. The concentrations of metals among the different mineral and organic fractions of soil were determined by several extraction procedures to study the metal distribution in the solid phase of the soil affected by the organic amendments. The results showed that the manure amendment increased the soil pH and the cation exchange capacity and enhanced the nutrient levels of these soils. The pine bark amendment decreased the soil pH and did not significantly change the nutrient status of soil. Soil pH, organic matter content and its degree of humification, which were altered by the amendments, were the main factors affecting Cu fractionation. Zn fractionation was mainly affected by soil pH. The addition of manure not only improved soil fertility, but also decreased metal bioavailability resulting in a reduction of metal toxicity. Conversely, pine bark amendment increased metal ioavailability. The use of sheep and horse manure could be a cost-effective practice for the restoration of contaminated mine soils.

Effects of soluble humic acids on the uptake of heavy metals by Vetiveria zizanioides (L.) Nash in contaminated mining soils

In the past, mining wastes were left wherever they might lie in the surroundings of the mine area. Unfortunately, inactive and abandoned mines continue to pollute our environment, reason why these sites should be restored with minimum impact. Phytoextraction is an environmental-friendly and cost-effective technology less harmful than traditional methods that uses metal hyperaccumulator or at least tolerant plants to extract heavy metals from polluted soils. One disadvantage of hyperaccumulator species is their slow growth rate and low biomass production. Vetiveria zizanioides (L.) Nash, perennial species adapted to Mediterranean climate has a strong root system which can reach up to 3 m deep, is fast growing, and can survive in sites with high metal levels (Chen et al., 2004). Due to the fact that metals in abandoned mine tailings become strongly bonded to soil solids, humic acids used as chelating agents could increase metal bioavailability (Evangelou et al., 2004; Wilde et al., 2005) and thereby promote higher accumulation in the harvestable parts of the plant. The objective of this study was to examine the performance of humic acid assisted phytoextraction using Vetiveria zizanioides (L.) Nash in heavy metals contaminated soils.

Target gene search for the metal-responsive transcription factor MTF-1

Activation of genes by heavy metals, notably zinc, cadmium and copper, depends on MTF-1, a unique zinc finger transcription factor conserved from insects to human. Knockout of MTF-1 in the mouse results in embryonic lethality due to liver decay, while knockout of its best characterized target genes, the stress-inducible metallothionein genes I and II, is viable, suggesting additional target genes of MTF-1. Here we report on a multi-pronged search for potential target genes of MTF-1, including microarray screening, SABRE selective amplification, a computer search for MREs (DNA-binding sites of MTF-1) and transfection of reporter genes driven by candidate gene promoters. Some new candidate target genes emerged, including those encoding α-fetoprotein, the liver-enriched transcription factor C/EBPα and tear lipocalin/von Ebner’s gland protein, all of which have a role in toxicity/the cell stress response. In contrast, expression of other cell stress-associated genes, such as those for superoxide dismutases, thioredoxin and heat shock proteins, do not appear to be affected by loss of MTF-1. Our experiments have also exposed some problems with target gene searches. First, finding the optimal time window for detecting MTF-1 target genes in a lethal phenotype of rapid liver decay proved problematical: 12.5-day-old mouse embryos (stage E12.5) yielded hardly any differentially expressed genes, whereas at stage 13.0 reduced expression of secretory liver proteins probably reflected the onset of liver decay, i.e. a secondary effect. Likewise, up-regulation of some proliferation-associated genes may also just reflect responses to the concomitant loss of hepatocytes. Another sobering finding concerns γ-glutamylcysteine synthetasehc (γ-GCShc), which controls synthesis of the antioxidant glutathione and which was previously suggested to be a target gene contributing to the lethal phenotype in MTF-1 knockout mice. γ-GCShc mRNA is reduced at the onset of liver decay but MTF-1 null mutant embryos manage to maintain a very high glutathione level until shortly before that stage, perhaps in an attempt to compensate for low expression of metallothioneins, which also have a role as antioxidants.

Synthesis and characterisation of pillared clay catalysts for hydro-cracking of heavy liquid fuels

A range of chromia pillared montmorillonite and tin oxide pillared laponite clay catalysts, as well as new pillared clay materials such as cerium and europium oxide pillared montmorillonites were synthesised. Methods included both conventional ion exchange techniques and microwave enhanced methods to improve performance and/or reduce preparation time. These catalytic materials were characterised in detail both before and after use in order to study the effect of the preparation parameters (starting material, preparation method, pillaring species, hydroxyl to metal ratio etc.) and the hydro cracking procedure on their properties. This led to a better understanding of the nature of their structure and catalytic operation. These catalysts were evaluated with regards to their performance in hydrocracking coal derived liquids in a conventional microbomb reactor (carried out at Imperial College). Nearly all catalysts displayed better conversions when reused. The chromia pillared montmorillonite CM3 and the tin oxide pillared laponite SL2a showed the best "conversions". The intercalation of chromium in the form of chromia (Cr203) in the interlayer clearly increased conversion. This was attributed to the redox activity of the chromia pillar. However, this increase was not proportional to the increase in chromium content or basal spacing. In the case of tin oxide pillared laponite, the catalytic activity might have been a result of better access to the acid sites due to the delaminated nature of laponite, whose activity was promoted by the presence of tin oxide. The manipulation of the structural properties of the catalysts via pillaring did not seem to have any effect on the catalysts' activity. This was probably due to the collapse of the pillars under hydrocracking conditions as indicated by the similar basal spacing of the catalysts after use. However, the type of the pillaring species had a significant effect on conversion. Whereas pillaring with chromium and tin oxides increased the conversion exhibited by the parent clays, pillaring with cerium and europium oxides appeared to have a detrimental effect. The relatively good performance of the parent clays was attributed to their acid sites, coupled with their macropores which are able to accommodate the very high molecular mass of coal derived liquids. A microwave reactor operating at moderate conditions was modified for hydro cracking coal derived liquids and tested with the conventional catalyst NiMo on alumina. It was thought that microwave irradiation could enable conversion to occur at milder conditions than those conventionally used, coupled with a more effective use of hydrogen. The latter could lead to lower operating costs making the process cost effective. However, in practice excessive coke deposition took place leading to negative total conversion. This was probably due to a very low hydrogen pressure, unable to have any hydro cracking effect even under microwave irradiation. The decomposition of bio-oil under microwave irradiation was studied, aiming to identify the extent to which the properties of bio-oil change as a function of time, temperature, mode of heating, presence of char and catalyst. This information would be helpful not only for upgrading bio-oil to transport fuels, but also for any potential fuel application. During this study the rate constants of bio-oil's decomposition were calculated assuming first order kinetics.

Avaliação do potencial da macrófita Pistia stratiotes na exposição de íon cromo (VI): biossorção e tolerância

The environmental pollution caused by industries has increased the concentration of pollutants in the environment, especially in water. Among the most diverse contaminants, there is the metals, who may or may not to be heavy/toxic, causing effluent of difficult treatment when in low concentrations. The search for alternative measures of wastewater effluent treatment has led to studies using phytoremediation technique through the various matrices (plant, fungi, bacteria) as means of polishing treatment to remove contaminants by means of biosorption/bioaccumulation. In order to use the phytoremediation technique for removing metals of the environmental, it have been performed bioassay with the macrophyte Pistia stratiotes. The bioassays were realized with healthy plants of P. stratiotes acclimatized in a greenhouse, at room temperature and lighting conditions during 28 days of cultivate. The cultivations were performed in glass vessels containing 1 L of the hydroponic solution with chromium (VI) in the potassium dichromate form with concentration range 0.10 to 4.90 mg L-1. The experiments were performed by Outlining Central Composite Rotational (OCCR), where the kinetics of bioaccumulation and chlorophyll a fluorescence were monitored in plants of P. stratiotes during cultivation. The collections of the samples and cultive solution were performed according to the OCCR. The chromium levels were measured in samples of P. stratiotes and the remaining solutions by the methodology of atomic absorption spectrometry by flame. The tolerance of P. stratiotes in relation to exposure to chromium (VI) was analyzed by parameters of physiological activity by means of chlorophyll a fluorescence, using the portable fluorometer PAM (Pulse Amplitude Modulation). The development of P. stratiots and their biomass were related to the time factor, while bioaccumulation capacities were strongly influenced by factors of time and chromium concentration (VI). The chlorophyll fluorescence parameters were affected by chromium and the exposure time at the bioassays. It was obtained an higher metal removal from the root in relation to the sheet, reaching a high rate of metal removal in solution. The experimental data removal kinetics were represented by kinetic models Irreversibly Langmuir, Reversible Langmuir, Pseudo-first Order and Pseudo-second Order, and the best fit for the culture solution was the Reversible Langmuir model with R² 0.993 and for the plant the best model was Pseudo-second order with R² 0.760.

Biosorción en tanque agitado de Cd(+2) y Pb(+2) con cáscara de cacao

En la búsqueda de tecnologías más limpias para el tratamiento de efluentes que contienen metales pesados se ha dirigido la atención hacia la biosorción. Este estudio permitió abordar el proceso de biosorción de 〖Cd〗^(+2)y 〖Pb〗^(+2) en efluentes mineros a través de la cáscara de cacao. Se determinó las características físico-químicas del biosorbente y el resultado obtenido fue: la cáscara de cacao tiene una superficie neutra, compuesta principalmente por grupos ésteres alifáticos; además se estudió los factores que afectan este proceso como son: pH, tamaño de partícula, tiempo de contacto, Temperatura, y la concentración inicial del metal. El pH óptimo para la biosorción de plomo es entre 4 y 5 y para el cadmio fue entre 5 y 6; con respecto al tiempo de contacto necesario para eliminar la mayor cantidad de iones metálicos fue de 10 minutos, siendo el resultado obtenido en la remoción tanto de cadmio como de plomo de 86,92% y 96,74% respectivamente. Se observó que la temperatura no afecta significativamente el proceso de biosorción como el pH y se determinó como óptima 25℃ ; también se analizó que la cáscara de cacao tiene mayor afinidad por el cadmio por tener un radio iónico más pequeño que el plomo permitiéndole alcanzar poros reducidos; además al aumentar la concentración, la eliminación de cadmio disminuyó y para el plomo aumentó pero no de forma significativa. Los datos experimentales de la biosorción de plomo y cadmio en cáscara de cacao, reproducen favorablemente el modelo cinético Pseudo Segundo Orden, con coeficientes de correlación (R^2) para 〖Pb〗^(+2) de 0,999 y 〖Cd〗^(+2) de 1. Finalmente en el estudio de equilibrio el modelo de Langmuir describe el proceso de adsorción para 〖Cd〗^(+2) y el modelo de Fleundlich se ajustó mejor a los datos experimentales para 〖Pb〗^(+2).

Initial growth of sunflower in soils with high concentrations of boron and heavy metals.

2008

Assessment of heavy metals in soils of a vineyard region with the use of principal component analysis.

Agricultural management with chemicals may contaminate the soil with heavy metals. The objective of this study was to apply Principal Component Analysis and geoprocessing techniques to identify the origin of the metals Cu, Fe, Mn, Zn, Ni, Pb, Cr and Cd as potential contaminants of agricultural soils. The study was developed in an area of vineyard cultivation in the State of São Paulo, Brazil. Soil samples were collected and GPS located under different uses and coverings. The metal concentrations in the soils were determined using the DTPA method. The Cu and Zn content was considered high in most of the samples, and was larger in the areas cultivated with vineyards that had been under the application of fungicides for several decades. The concentrations of Cu and Zn were correlated. The geoprocessing techniques and the Principal Component Analysis confirmed the enrichment of the soil with Cu and Zn because of the use and management of the vineyards with chemicals in the preceding decades.