Large-Area Experiment on Uptake of Metals by Twelve Plants Growing in Soils Contaminated with Multiple Metals

Abstract

A site in central Taiwan with an area of 1.3 ha and contaminated with Cr, Cu, Ni, and Zn was selected to examine the feasibility of phytoextraction. Based on the results of a pre-experiment at this site, a total of approximately 20,000 plants of 12 species were selected from plants of 33 tested species to be used in a large-area phytoextraction experiment at this site. A comparison with the initial metal concentration of 12 plant species before planting demonstrated that most species accumulated significant amounts of Cr, Cu, Ni, and Zn in their shoots after growing in this contaminated site for 31 d. Among the 12 plant species, the following accumulated higher concentrations of metals in their shoots; Garden canna and Garden verbena (45–60 mg Cr kg⁻¹), Chinese ixora and Kalanchoe (30 mg Cu kg⁻¹), Rainbow pink and Sunflower (30 mg Ni kg⁻¹), French marigold and Sunflower (300–470 mg Zn kg⁻¹). The roots of the plants of most of the 12 plant species can accumulate higher concentrations of metals than the shoots and extending the growth period promotes accumulation in the shoots. Large-area experiments demonstrated that phytoextraction is a feasible method to enable metal-contaminated soil in central Taiwan to be reused.

KEY WORDS:

• phytoextraction
• multiple metals-contaminated soils
• large-area experiment

ACKNOWLEDGMENTS

The authors would like to thank the Environmental Protection Administration of the Republic of China, Taiwan, for financially supporting this research under Contract Number EPA-94-GA12-03-A212. Professors Ren-Shih Chung, Dar-Yuan Lee, Chao-Ming Lai, and Chien-Ten Chen at the Department of Agricultural Chemistry, National Taiwan University are appreciated for their assistance with the experimental design. Prof. B. C. Chen of the Department of Post-Modern Agriculture, MingDao University, is commended for helping with field management. Ted Knoy is appreciated for his editorial assistance.

Notes

^aSoil Pollution Control Standards (SPCS) of Soil and Groundwater Pollution Remediation Act in Taiwan.

^bSoil Pollution Monitoring Standards (SPMS) of Soil and Groundwater Pollution Remediation Act in Taiwan.

^cOnly for normal lands (non-farmland), no standards for cropped lands (farmland).

^dMean ± standard deviation (n = 134).

^aThe highest metal concentration according to the survey result of spacial distribution (Table 1).

^bSoil Pollution Monitoring Standards of Soil and Groundwater Pollution Remediation Act in Taiwan (Table 1).

^cTotal amounts of metal needed to be removed (kg ha⁻¹) = (a − b) × 2,000,000 kg ha⁻¹ × 10⁻⁶; 2,000,000 kg ha⁻¹ of soil weight was estimated for topsoil (0–15 cm) and bulk density was estimated as 1.3 to 1.4 Mg m⁻³.

^dResult of 1st large area experiment (Figure 2).

^eEstimated period needed = c/d/5 (planting the tested plants five times per year).