Phytoextraction of cadmium-contaminated soil and potential of regenerated tobacco biomass for recovery of cadmium

Abstract

The aim of this study was to estimate the influence of regenerated tobacco on the extraction of Cd from two acidic soils as well as to address the problem of how to deal with contaminated leaves following phytoextraction. Results showed that a coppicing tobacco led to a decline in Cd concentration in regenerated leaves and stalks when plants were grown in pots, but increased concentrations in regenerated lower and middle leaves when plants were grown under field conditions. The highest recorded bioconcentration factors in Chaling and Guanxi soil were 37.53 and 19.21 in lower leaves in the field, respectively. Total Cd extraction efficiency in practice (9.43% for Chaling soil and 6.24% for Guanxi soil) under field conditions confirmed our theoretical calculations (10.0% for Chaling soil and 6.73% for Guanxi soil). Use of a 0.5% hydrochloric acid(HCl) solution was sufficient to reduce Cd (98.4%) in tobacco leaves to permissible levels as required by the Hygienic Standard for Feeds in China (≤0.5 mg kg−1). Regenerated tobacco has the potential to allow cultivation of Cd contaminated farmland to produce animal feed, assist in lowering total Cd content of soil, and allow income generation for farmers.

The influence of compost and nitrilotriacetic acid on mercury phytoextraction by Lepidium sativum L.

“…The effectiveness of assisted phytoextraction can be also described as a percentage amount of Hg removed from polluted soil. In accordance with Yang et al the PE of the top soils (0–20 cm) in practice is defined as a ratio of Hg concentration in soil before cleaning minus its concentration after the process to Hg initial concentration in soil . Based on the results presented in Table it can be seen that the amount of Hg removed during phytoextraction by L. sativum L. for soil polluted by 10 or 100 mg of Hg kg −1 soil dry weight was equal to around 15% or 11%, respectively.…”

“…The data presented by Yang et al using Nicotiana tabacum L. in phytoextraction of Cd contaminated soil showed that PE ranged between 33 and 66% of total Cd removed in pot experiments. The experiment took 80 days . However, the study of Niu et al demonstrated that the removal rate for Cd hyperaccumulating species Solanum nigrum cultivated for 90 days was equal to an average of 11% in unassisted phytoextraction and increased twice for the process assisted by combined use of glycine, glutamic acid and cysteine .…”

“…In accordance with Yang et al the PE of the top soils (0-20 cm) in practice is defined as a ratio of Hg concentration in soil before cleaning minus its concentration after the process to Hg initial concentration in soil. 33 Based on the results presented in Table 3 it can be seen that the amount of Hg removed during phytoextraction by L. sativum L. for soil polluted by 10 or 100 mg of Hg kg −1 soil dry weight was equal to around 15% or 11%, respectively. Changing the soil substrate by simultaneous application of compost + NTA enabled to increase the PE of 5% and 9% for growing medium pollution at Hg concentration 10 and 100 mg kg −1 dry weight, respectively.…”

“…Phytoextraction efficiency (PE) was calculated using (Eqn (3)) as follows: …”

“…The experiment took 80 days. 33 However, the study of Niu et al demonstrated that the removal rate for Cd hyperaccumulating species Solanum nigrum cultivated for 90 days was equal to an average of 11% in unassisted phytoextraction and increased twice for the process assisted by combined use of glycine, glutamic acid and cysteine. 60 In the present study the pot experiment took only 7 days.…”