Lina Sun

Evaluation of phytoextracting cadmium and lead by sunflower, ricinus, alfalfa and mustard in hydroponic culture

Soil contaminated with heavy metals cadmium (Cd) and lead (Pb) is hard to be remediated. Phytoremediation may be a feasible method to remove toxic metals from soil, but there are few suitable plants which can hyperaccumulate metals. In this study, Cd and Pb accumulation by four plants including sunflower (Helianthus annuus L.), mustard (Brassica juncea L.), alfalfa (Medicago sativa L.), ricinus (Ricinus communis L.) in hydroponic cultures was compared. Results showed that these plants could phytoextract heavy metals, the ability of accumulation differed with species, concentrations and categories of heavy metals. Values of BCF (bioconcentration factor) and TF (translocation factor) indicated that four species had dissimilar abilities of phytoextraction and transportation of heavy metals. Changes on the biomass of plants, pH and Eh at different treatments revealed that these four plants had distinct responses to Cd and Pb in cultures. Measurements should be taken to improve the phytoremediation of sites contaminated with heavy metals, such as pH and Eh regulations, and so forth.

Adsorption characteristics of copper, lead, zinc and cadmium ions by tourmaline

The adsorption characteristics of heavy metals: Cu(II), Pb(II), Zn(II) and Cd(II) ions on tourmaline were studied. Adsorption equilibrium was established. The adsorption isotherms of all the four metal ions followed well Langmuir equation. Tourmaline was found to remove heavy metal ions efficiently from aqueous solution with selectivity in the order of Pb(II)>Cu(II)>Cd(II)>Zn(II). The adsorption of metal ions by tourmaline increased with the initial concentration of metal ions increasing in the medium. Tourmaline could also increase pH value of metal solution. -The maximum heavy metal ions adsorbed by tourmaline was found to be 78.86, 154.08, 67.25, and 66.67 mg/g for Cu(II), Pb(II), Zn(II) and Cd(R), respectively. The temperature (25-55 degrees C) had a small effect on the adsorption capacity of tourmaline. Competitive adsorption of Cu(II), Pb(II), Zn(II) and Cd(II) ions was also studied. The adsorption capacity of tourmaline for single metal decreased in the order of Pb>Cu>Zn >Cd and inhibition dominance observed in two metal systems was Pb>Cu, Pb>Zn, Pb>Cd, Cu>Zn, Cu>Cd, and Cd>Zn.

Iron-deficiency induces cadmium uptake and accumulation in Solanum nigrum L.

Phytoremediation is a promising tool in removing pollutants from the environment or in rendering them harmless. The objective of this research was to determine the effect of iron-deficiency on the uptake of cadmium by Solanum nigrum L. Results showed that iron-deficiency induced cadmium uptake, biomass decrease and changes in pH and Eh in hydroponic culture. Under iron-deficiency status, the decrease in pH and the increase in Eh might result in higher cadmium availability. Bioconcentration and translocation factors indicated that iron-deficiency status affected cadmium accumulation and translocation in Solanum nigrum L.

Solubility of ion and trace metals from stabilized sewage sludge by fly ash and alkaline mine tailing

Stabilized sewage sludge (SS) by fly ash (FA) and alkaline mine tailing as artificial soil, to be applied on the ecological rehabilitation at mining junkyards, offers a potentially viable utilization of the industrial by-product, as well as solves the shortage of soil resource in the mine area. An incubation experiment with different ratios of SS and FA was conducted to evaluate the solubility of ions and trace elements from stabilized sewage sludge. Results showed that fly ash offset a decrease in pH value of sewage sludge. The pH of (C) treatment (FA:SS = 1:1) was stable and tended to neutrality. The SO4(2-) and Cl- concentrations of the solution in the mixture were significantly decreased in the stabilized sewage sludge by alkaline fly ash and mine tailing, compared to the single SS treatment. Stabilized sewage sludge by FA weakened the nitrification of total nitrogen from SS when the proportion of FA in the mixture was more than 50%. The Cr, Ni, and Cu concentrations in the solution were gradually decreased and achieved a stable level after 22 days, for all treatments over the duration of the incubation. Moreover stabilized sewage sludge by fly ash and/or mine tailing notably decreased the trace metal solubility. The final Cr, Cu, and Ni concentrations in the solution for all mixtures of treatments were lower than 2.5, 15, and 50 microg/L, respectively.

Influences of phosphate nutritional level on the phytoavailability and speciation distribution of cadmium and lead in soil

A pot experiment was conducted to examine the influence of phosphate levels on the phytoavailability and speciation distribution of cadmium (Cd), lead (Pb) in soil. Spring wheat (Triticum aestivum L.) was selected as the tested plant. There were 5 phosphate fertilizer(Ca(H2PO4)2) levels including 0, 50, 100, 200, and 400 mg P2O5/kg soil, marked by PO, P1, P2, P3, and P4, respectively. CdCl2 x 2.5H2O and Pb(NO3)2 were added to soil as the following levels: Cd + Pb = 25+0, 0+1000, and 25+1000 mg/kg, marked by T1, T2, and T3, respectively. The results showed that the P fertilizer promoted the dry weight of wheat in all treatments and alleviated the contamination induced by Cd and Pb. With increasing levels of the additional P fertilizer, Cd concentration in different parts (root, haulm, chaffand grain) of wheat decreased at the P1 level at first and then increased. The soluble plus exchangeable (SE) fraction of Cd in soil decreased at the P1 level and then increased from P2 to P4 levels. The moderate P fertilizer reduced the phytoavailability of Cd. The application of P could obviously restrain the uptake of Pb by wheat and there were significantly negative correlations between the levels of P and the uptake of Pb. Phosphorus supply resulted in a decrease in the SE fraction of Pb and there was a significantly negative correlation between the levels of P and the SE fraction of Pb in soil. All the levels of the P fertilizer in this experiment could reduce the phytoavailability of Pb. Thus, it is feasible to apply the P fertilizer (Ca(H2PO4)2) to Pb contaminated soils. However, the levels of P application should be restricted in case that redundant P may increase the phytoavailability of Cd.

Effects of Bacteria on Cadmium Bioaccumulation in the Cadmium Hyperaccumulator Plant Beta Vulgaris Var. Cicla L.

To investigate the effects of two cadmium-tolerant bacteria, Staphylococcus pasteuri (S. pasteuri X1) and Agrobacterium tumefaciens (A. tumefaciens X2), on cadmium uptake by the cadmium hyperaccumulator plant Beta vulgaris var. cicla L., a pot experiment with artificially contaminated soil was conducted. The results demonstrated that both cadmium-tolerant bacteria enhanced the dry weight of Beta vulgaris var. cicla L. The total dry weights of plants in the control CK20, S. pasteuri X1 and A. tumefaciens X2 treatments were 0.85, 1.13, and 1.38 g/pot, respectively. Compared with the control CK20 findings, the total dry weight of plants was increased by 32.8 and 61.1% after inoculation with S. pasteuri X1 and A. tumefaciens X2, respectively, indicating that A. tumefaciens X2 more strongly promoted the growth of Beta vulgaris var. cicla L. than S. pasteuri X1. In addition, inoculation with S. pasteuri X1 and A. tumefaciens X2 significantly (p < 0.05) promoted cadmium uptake by plants and improved the bioaccumulation of cadmium by the plants from the soil. Moreover, the inoculation of S. pasteuri X1 and A. tumefaciens X2 effectively facilitated the transfer of cadmium in the soil from the Fe-Mn oxide and residual fractions to the soluble plus exchangeable and weakly specially adsorbed fractions in the rhizosphere soils of plants. The bacterial enhancement of cadmium phytoavailability might provide a potential and promising method to increase the efficiency of phytoextraction.

Relationships Between Changes of Three Organic Acids (Oxalic Acid, Citric Acid and Tartaric Acid) and Phytoextration by Sunflower (Helianthus annuus L.) in Sand Cultures Contaminated with Cadmium and Lead

Sand culture was used to investigated the Cd and Pb phyto extraction by sunflower, and changes of organic acids including oxalic acids, citric acids and tartaric acids. The results showed that bioconcentration factors (BCF) of Cd or Pb increased with time and decreased with concentrations, the highest Cd-BCF and Pb-BCF appeared in Cd5 (21) and Pb50(7.95), respectively. The contents of oxalic acids in Cd 40 were the highest (152.20 mg¡¤L-1) at the 90th day. Citric acids in Cd10and Pb400 treatments were higher than other Cd and Pb treatments, which was 578.12 mg¡¤L-1, 413.87 mg¡¤L-1, respectively at the end of the test. Tartaric acids in single Cd or Pb treatments showed increasing trend with time obviously, the highest (474.15 mg¡¤L-1) appeared in Cd5 treatments at the end of this experiment. The presence of heavy metals may influence organic acids secretion from roots. And organic acids could promote bio availability of heavy metals or impact the mechanism of metals uptake, which might result the distinction of Cd or Pb phyto extraction by sunflower. This study may supply useful information for phytoremediation of soil contaminated with cadmium and lead in situ.

Relations Between Cadmium Accumulation and Organic Acids in Roots Exudation of Zea Mays L.

The influence of Cadmium(Cd) on exudation of low molecular weight organic acids (LMWOAs) were investigated based on the hydroponic culture experiment. Tartaric, citric, malic, and acetic acids were chosen as representatives of LMWOAs commonly present in roots exudation. We investigated the Cadmium accumulation in Zea Mays L.. In particular, the relationship of exudation of LMWOAs by roots with Cd accumulation in Zea Mays L. were also investigated. The results showed that under the different levels of Cd, the exudation of four organic acids by roots had the different change trend. The concentrations of four organic acids in roots exudation were in the same following sequence tartaric>citric>malic>acetic. And the content of Cd in plants increased with increasing Cd concentrations. Cd accumulation in plants had significant (P<0.05 or P<0.01) positive correlations with exudation of citric, tartaric and acetic acids.

Relationships between Changes of Three Organic Acids (Oxalic Acid, Citric Acid and Tartaric Acid) and Phytoextraction by Sunflower (Helianthus annuus L.) in Sand Cultures Contaminated with Cadmium and Lead

Sand culture was used to investigated the Cd and Pb phyto extraction by sunflower, and changes of organic acids including oxalic acids, citric acids and tartaric acids. The results showed that bioconcentration factors (BCF) of Cd or Pb increased with time and decreased with concentrations, the highest Cd-BCF and Pb-BCF appeared in Cd5 (21) and Pb50(7.95), respectively. The contents of oxalic acids in Cd 40 were the highest (152.20 mgi¤L-1) at the 90th day. Citric acids in Cd10and Pb400 treatments were higher than other Cd and Pb treatments, which was 578.12 mgi¤L-1, 413.87 mgi¤L-1, respectively at the end of the test. Tartaric acids in single Cd or Pb treatments showed increasing trend with time obviously, the highest (474.15 mgi¤L-1) appeared in Cd5 treatments at the end of this experiment. The presence of heavy metals may influence organic acids secretion from roots. And organic acids could promote bio availability of heavy metals or impact the mechanism of metals uptake, which might result the distinction of Cd or Pb phyto extraction by sunflower. This study may supply useful information for phytoremediation of soil contaminated with cadmium and lead in situ.

Evaluation of Iron on Cadmium Accumulate by Triticum aestivum L. in Hydroponic Culture

The objective of this research was to determine the effect of Fe deficiency on the uptake of cadmium (Cd) by wheat (Triticum aestivum L.) in hydroponic culture. Results showed that Fe deficiency induced cadmium uptake, biomass decrease and changes of pH and Eh in hydroponic culture. Under Fe deficiency status, the decrease in pH and the increase in Eh might result in higher cadmium availability. Values of bioconcentration factor (BCF) and translocation factor (TF) indicated that Fe-deficiency status affected cadmium accumulation and translocation in wheat. The results of this research would significantly improve the understanding of metal removal from the contiminated environment.