The influence of cadmium contamination and salinity on the survival,growth and phytoremediation capacity of the saltmarsh plant Salicornia ramosissima

The major aim of this study was to evaluate the capacity of Salicornia ramosissima on Cadmium phytoremediation under distinct salinities and, consequently, the toxic effects on the plant's development. A greenhouse experiment was performed, using two Cd concentrations (50 and 100 μg l⁻¹) in different salinities (0, 5 and 10). Mortality and weight variation, observed at the end of the experiment, showed significant differences between some treatments, meaning that these variables were affected by the salinity and Cd concentrations. The highest Cd accumulation was detected in the roots, and decreased with the increase of salinity and Cd concentration. S. ramosissima is a potential candidate for Cd phytoremediation at salinities close to 0 and its capabilities in Cd phytoaccumulation and phytoestabilization proved to be quite interesting. The optimization of phytoremediation processes by S. ramosissima could turn possible the use of this plant in the recovery of contaminated ecosystems.     

土壤砷污染特点与植物修复探讨

土壤砷污染一直是国内外关注的热点,植物修复技术是20世纪80年代提出的利用植物治理土壤污染的一种"绿色技术".土壤中砷主要以无机态的形式存在,并主要为Al、Fe、Ca等所吸附而产生共沉淀,水溶态的砷含量一般小于总砷的5%.砷污染区的植物砷含量一般高于非污染区,具有耐贫瘠、耐干旱且地带性不是很强的特点.到目前为止,世界范围内已发现3种超富集砷的植物.根据野外调查与分析,利用超富集植物治理土壤轻度砷污染是可行的.     

Promoted dissipation of phenanthrene and pyrene in soils by amaranth (<Emphasis Type="Italic">Amaranthus tricolor</Emphasis> L.)

A study was conducted to investigate the performance of amaranth, a known hyperaccumulator of cesium, on the promotion of the dissipation of soil phenanthrene and pyrene, which are PAHs (polycyclic aromatic hydrocarbons). Amaranthus tricolor L. een choi was the cultivar used. The presence of Amaranthus tricolor L. evidently enhanced the dissipation of these PAHs in soils with initial phenanthrene concentrations of 7.450–456.5 mg/kg dw (dw, dry weight) and pyrene of 8.010–488.7 mg/kg dw. At the end of the experiment (45 days), the residual concentrations of phenanthrene and pyrene in spiked soils with plants were generally higher than those with no plants. The loss of phenanthrene and pyrene in vegetated soils was 87.85–94.03% and 46.89–76.57% of the soil with these chemicals, which was 2.55–13.66% and 11.12–56.55% larger than the loss in non-vegetated soils, respectively. The accumulation of phenanthrene and pyrene by the plant was evident. Root and shoot concentrations of these chemicals monotonically increased with increasing soil PAH concentrations. Bioconcentration factors (BCFs), defined as the ratio of chemical concentrations in plants and in the soils (on a dry weight basis), of phenanthrene and pyrene by roots were 0.136–0.776 and 0.603–1.425, while by shoots were 0.116–0.951 and 0.082–0.517, respectively. BCFs of phenanthrene and pyrene tended to decrease with the increasing concentrations of soil phenanthrene and pyrene. Plant accumulation only accounted for less than 0.32% (for phenanthrene) and 0.33% (for pyrene) of the total amount enhancement of the dissipated PAHs in vegetated vs. non-vegetated soils. In contrast, plant-promoted microbial biodegradation was the predominant contribution to the plant-enhanced dissipation of soil phenanthrene and pyrene. These results suggested the feasibility of the radionuclide hyperaccumulator in phytoremediating the soil PAH contaminants.     

Effects of Compost Addition on Pyrene Removal from Soil Cultivated with Three Selected Plant Species

A greenhouse pot experiment was conducted to investigate the effect of compost addition on the phytoremediation ability of Medicago sativa, Brassica napus, and Lolium perenne in soils contaminated with pyrene. Pyrene concentrations were evaluated after 90 days in contaminated uncultivated amended‐soil, cultivated amended‐soils, and shoots and roots of the three plant species. The addition of compost enhances significantly pyrene dissipation from 16 to 26% in uncultivated soil, whereas in cultivated soils it appears not to have any significant effect on pyrene dissipation, neither pyrene was detectable in shoots and roots of the three species examined. The high partition coefficient of pyrene to compost dissolved organic matter (DOM) and the molar absorptivity values at 280 nm (ε₂₈₀) indicate a high affinity of pyrene to compost DOM molecules, likely due to their aromatic character. These results suggest that compost improves pyrene removal from soil, possibly by promoting its adsorption onto compost DOM. This property is very important in indicating that compost can be used, besides for its amendment capacity, also as a potential tool for remediation of contaminated soils.     

Growth and survival of Halimione portulacoides stem cuttings in heavy metal contaminated soils

The halophytic shrub Halimione portulacoides demonstrates a high tolerance to heavy metal contamination and a capacity for accumulating metals within its tissues. On the Iberian Peninsula, this species has colonized habitats with high levels of metal pollution. The aim of this study is to analyze the response of H. portulacoides stem cuttings to this pollution. Growth, photosynthesis and metal uptake were examined in H. portulacoides through an experiment in which stem cuttings were replanted in metal-contaminated soil. This condition decreased growth and lowered both photosynthetic rate and stomatal conductance. Reduced photosynthetic performance was largely due to the reduced concentration of photosynthetic pigments. Despite these responses, there was some important evidence suggesting the phytoremediatory potential of Halimione stem cuttings. The results of our study indicate that this salt-marsh shrub may represent a biotool of value in the restoration of polluted areas.