The Cd and Zn accumulation and phytoextraction potential of seven willow clones was investigated in a pot experiment for two vegetation periods. Heavily polluted Fluvisol-Litavka, moderately contaminated Cambisol-Pribram, and unpolluted control Chernozem-Suchdol were used. Significant differences were found in Cd and Zn accumulation between the willow clones. Cd and Zn were transferred from roots to aboveground tissues and all tested clones confirmed higher Cd and Zn accumulation in leaves than in twigs. Cd and Zn amounts removed by willow leaves were the highest from the most polluted soil (up to 83% Cd and 71% Zn of total removal). Therefore the harvest of leaves is necessary if willows are planted for heavy metal phytoextraction. Although the extremely high Zn contamination of Fluvisol-Litavka significantly reduced biomass production, willows planted in this soil showed the highest Zn removal because of extremely high Zn accumulation (max. 5061 ppm in leaves). Clones planted in moderately contaminated soil achieved the highest Cd removal. Clones showed different abilities to remove Cd and Zn, which was dependent on soil type and contamination level. Remediation factors were determined less than 1% for Zn in the heavily polluted soil and also unsatisfactory for Cd. However, it was shown that willows were suitable phytoextractors of moderately contaminated soil. About 20% of Cd and 4% of Zn were removed by harvested biomass from the total content of soil after two vegetation periods.

Abstract:The experiment assessed the variability of in seven clones of willow plants of high biomass production (Salix smithiana S-218, Salix smithiana S-150, Salix viminalis S-519, Salix alba S-464, Salix 'Pyramidalis' S-141, Salix dasyclados S-406, Salix rubens S-391). They were planted in a pots for three vegetation periods in three soils differing in the total content of risk elements. Comparing the calculated relative decrease of total metal contents in soils, the phytoextraction potential of willows was obtained for cadmium (Cd) and zinc (Zn), moderately contaminated Cambisol and uncontaminated Chernozem, where aboveground biomass removed about 30% Cd and 5% Zn of the total element content, respectively. The clones showed variability in removing Cd and Zn, depending on soil type and contamination level: S. smithiana (S-150) and S. rubens (S-391) demonstrated the highest phytoextraction effect for Cd and Zn. For lead (Pb) and arsenic (As), the ability to accumulate the aboveground biomass of willows was found to be negligible in both soils. The results confirmed that willow plants show promising results for several elements, mainly for mobile ones like cadmium and zinc in moderate levels of contamination. The differences in accumulation among the clones seemed to be affected more by the properties of clones, not by the soil element concentrations or soil properties. However, confirmation and verification of the results in field conditions as well as more detailed investigation of the mechanisms of cadmium uptake in rhizosphere of willow plants will be determined by further research.

As, Cd, Pb and Zn accumulation in the aboveground biomass of seven clones of Salix spp. and changes in element uptake by plants after element addition to soil were studied in a pot experiment. Unpolluted Chernozem (Suchdol) as a control and soils with addition of As (100 mg/kg), Cd (40 mg/kg) and either Pb (2000 mg/kg) (Suchdol-Pb) or Zn (2000 mg/kg) (Suchdol-Zn) were used for the experiment. Significant differences were found in the accumulation of elements between willow clones and also between different element additions to the soil. Although As and Cd uptake slightly increased in Suchdol-Zn soil compared to Suchdol-Pb soil, the element removal from soil was significantly higher in Suchdol-Pb soil due to a significant reduction of aboveground biomass yield in Suchdol-Zn soil caused by Zn phytotoxicity. The yield reduction decreased the uptake of plant-available elements by biomass, thus higher plant-available portions of As and Cd were found in Suchdol-Zn soil. Element removal from soil was more dependent on element contents in willow tissues in Suchdol-Pb soil than in Suchdol-Zn soil, where willow plants exhibited physiological symptoms of phytotoxicity.

High-biomass tree species holds promise for a clean up of metal contaminated soils. Root and fungal activities modify soil characteristics that are important factors for the phytoextraction process (metal availability and toxicity). In a rhizobox experiment, two clones of Salix × rubens derived from contaminated and non-contaminated sites were tested for growth performance and metal (Cd, Pb and Zn) accumulation on a polluted Calcaric Cambisol. The largest metal concentrations in leaves were 66.7 mg Cd/kg, 12.8 mg Pb/kg and 1090 mg Zn/kg. The results indicate that metal tolerance and accumulation of S. × rubens may be a constitutive rather than an adaptive property. Soil pH did not differ among rhizobox compartments. However, acid neutralization capacity was decreased in rhizosphere. DOC in rhizosphere was increased by 37% and seemed to enhance labile fraction of Pb and Zn, whereas Cd was not affected. The replenishment of labile metals from less labile soil fractions was efficient enough to almost compensate the plant uptake. S. × rubens can effectively induce chemical changes in the rhizosphere is very promising for a clean up of metal-polluted soils.

A set of 45 samples of the sludge from wastewater factories in the area of the Czech Republic was completed. The selection of wastewater factories reflected the extent of observed area as well as the occurrence of the industrial wastewater. The contents of persistent organic pollutants (POPs) were determined in the samples. Moreover, the contents of polychlorinated dibenzo-p-dioxins and dibenzofuranes (PCDD/F) were detected in 16 samples. The set of analytical data summarises the level of sewage sludge contamination by POPs within Czech wastewater factories. The results were compared with the directive of Czech Ministry of Environment, No. 382/2001 Sb. and with the proposed limit values of the EU directive, No. 86/278. Among all the determined substances only the value of the sum of polycyclic aromatic hydrocarbons (PAHs) content exceeded the threshold value given by the proposed EU directive.