Effects of Different Organic Materials on Bio-availability of Cd, Pb in a Contaminated Greenhouse Soil

Abstract

A two-season soil culture experiment was continually conducted to study the effects of three organic materials,namely Danty, Peat and Biochar,respectively,on combined forms and bio-availability of cadmium (Cd) and lead (Pb) under Cd and Pb in single and combined pollution during 2014-2015. This study aimed to provide a theoretical basis for remediating greenhouse soil contaminated with heavy metals Cd and Pb using organic materials. The main results were as follows: the content of DTPA-Cd decreased significantly by 11.9%(P<0.05) in the soil of Cd and Pb combined pollution with the application of danty, the total of exchangeable Cd, carbonate-bound Cd and iron-manganese oxide bound Cd was reduced by 26.4% and 34.4% in the soil, and the accumulation of Cd in shoots was significantly cut down by 32.0% and 28.0% (P<0.05) respectively in Cd single and Cd and Pb combined pollution after applying danty; the content of DTPA-Pb was significantly depleted by 83.5% and 83.8%(P<0.05), the total of exchangeable Pb, carbonate-bound Pb and iron-manganese oxide bound Pb was decreased by 34.5% and 13.9% in the soil and the accumulation of Pb in shoots was significantly reduced by 32.0% and 30.0% (P<0.05) in Pb single and Cd and Pb combined pollution respectively as the use of danty. The content of DTPA-Cd was significantly decreased by 18.9% (P<0.05) in the soil of Cd and Pb combined pollution with the use of peat, the accumulation of Cd in shoots was reduced by 38.0% and 23.4%(P<0.05) in Cd single and Cd-Pb combined pollution respectively after the application of peat; The content of DTPA-Pb was significantly decreased by 2.7% and 7.2%(P<0.05), the total of exchangeable Pb, carbonate-bound Pb and iron-manganese oxide bound Pb was decreased by 15.8% and 14.6% in the soil and the accumulation of Pb in shoots was significantly reduced by 12.7% and 23.4% (P<0.05) respectively in Pb single and Cd and Pb combined pollution due to the application of peat. The pH value of the soil was increased by the use of biochar, the content of DTPA-Cd was reduced by 4.7% and 15.0% respectively in the soil of Cd single and Cd and Pb combined pollution, and the accumulation of Cd in shoots was significantly minified by 38.0% and 23.4% respectively in Cd single and Cd and Pb combined pollution as the application of biochar. The content of DTPA-Pb was decreased by 6.8% and 1.0% and the total of exchangeable Pb, carbonate-bound Pb and iron-manganese oxide bound Pb was cut down by 11.9% and 30.0% in the soil of Pb single and Cd and Pb combined pollution respectively by the application of biochar. The content of Cd in plant was most significantly positively correlated with the content of exchangeable Cd in soil (P<0.01). The content of Pb in plant was most significantly positively correlated with the total of exchangeable Pb, carbonate-bound Pb and iron-manganese oxide bound Pb (P<0.01). In summary, after the application of danty, peat and biochar, the proportion of highly active content of Cd and Pb was minified through adjusting soil pH and immobilizing Cd and Pb by means of adsorption and complexation in greenhouse soil. With the analysis of input-output, the application of danty, peat and biochar costs 4050 yuan·hm-2, 11250 yuan·hm-2 and 22500 yuan·hm-2, respectively. Thus danty, peat and biochar could be used as effective organic agents in the remediation of Cd and Pb contaminated greenhouse soil.