Effects of Two Amendments on Heavy Metal and Nutrient Absorption of Lettuce Grown on Contaminated Soil

Abstract:

In order to understand remediation effect of wollastonite (WS) and 4A molecular sieve (MS) on Cd-contaminated soils collected from northern Guangdong Province, the absorption of heavy metal and nutrient of lettuce (Lactuca sativa) was studied by using pot experiment. The results showed that the available Cd and Pb contents of soil significantly reduced with ≥660 mg Si/kg MS and WS, on the contrary, those increased with low dose (220 mg Si/kg). Therefore, it indicated that ≥660 mg Si/kg MS and WS had significant inhibitory effect on the accumulation of Cd and Pb of lettuce. WS inhibited lettuce Cd uptake through enhancing Ca-Cd competition rather than reducing Cd availability in soil. MS reduced Ca, Mg, Mn and Zn contents and slightly increased Cu content in lettuce. WS decreased Mn and Zn contents and slightly increased Ca and Cu contents in lettuce. The lettuce yield reduced by 29% with high dose of MS (880 mg Si/kg), and increased by 10%-12% with high dose of WS (≥660 mg Si/kg). In conclusion, WS had better performance in boosting crop yield and decreasing crop Cd, showing a potential for remediation of Cd-contaminated soils. Besides, the decreases of Zn and Mn contents in crops should be addressed by the proper addition of Zn and Mn nutrients into soils.

Key words:Heavy metal contamination;Wollastonite;Molecular sieve;Immobilization amendment;Soil remediation