Effect Of Organic Acids On Activity Of Copper And Cadmium In Soil And Their Phytoavaliability

The results of pot culture test and imitate test in room showed that the effects of tartraric acid (TA) and fumic acid (FA) and EDTA on sorption-desorption and transportation and activity and phytoavaliability of Cu 2+ and Cd 2+ in cinnamon soil. The main results were shown as follows:1. The sorption of Cu2+ by soil was increased in the presence of EDTA. At lower concentration (0-0.1mmol -L-1) of TA and FA, sorption of Cu2+ by soil increased with the increment of TA and FA, and at higher concentration (0.1-5mmol L-1) of TA and FA, sorption of Cu2+ by soil decreased with the increment of TA and FA. The sorption of Cd2+ by soil was increased in the presence of TA and EDTA. At lower concentration (0-0.4mmol -L-1) of FA, sorption of Cd2+ by soil increased with the increment of FA, and at higher concentration (0.4-5mmol L-1) of FA, sorption of Cd2+ by soil decreased with the increment of FA. The desorption of Cd2+ by DTPA was increased in the presence of FA, TA and EDTA. The desorption of Cd2+ by DTPA was increased in the presence of EDTA. The desorption of Cd2+ by soil was decreased in the presence of TA and FA.2. The results of leaching test showed that EDTA enhanced the rate of total leach of Cu2+ and Cd2+. Leaching with 3 mmol L-1 EDTA, the rate of total leach of Cu2+ was 72%.It was 65 times of check group. Leaching with 1 mmol L-1 EDTA, the rate of total leach of Cd2+ was 91%. It was 14 times of check group. It showed that EDTA enhanced the mobility of Cu2+ and Cd2+ in soil column. Most of Cu2+ and Cd2+ was leached from soil column. Humic acid (HA) and TA restrained the rate of total leach of Cu2+ and Cd2+. Leaching with 3 mmol L-1 TA and HA, the rate of total leach of Cu2+ was 0.19% and 0.08%, the rate of totle leach of Cd2+ was 0.79% and 0.61%. It showed that humic acid (HA) and TA restrained the mobility of Cu2+ and Cd2+ in soil, and most of Cu2+ and Cd2+ was retain in the soil column3. In the heavy metal-contaminated soils, the content of exchangeable species Cu2+ and Cd2+ increased and carbonate-bound species and Fe-Mn oxide-bound species Cu2+ and Cd2+ decreased with the rate of EDTA added. It implicated that EDTA promoted the transformation from carbonate-bound species and Fe-Mn oxide-bound species Cu2+ and Cd2+ to exchangeable species Cu2+ and Cd2+. TA enhanced the content of exchangeable 河北农业大学2003届顿十毕业论文species Cu2+ and Cd2+, but it inferior to EDTA in effect. The effect of HA was different from EDTA and TA, organic-bound species Cu2+ and Cd2+ was increased, and exchangeable species and carbonate-bound species Cu2+ and Cd2+ were decreased with the increment of HA. It implicated that EDTA promotes the transformation from carbonate-bound species and exchangeable species Cu2+ and Cd2+ to organic-bound species Cu2+ and Cd2+.4. The pot culture test showed that EDTA obviously enhanced the availability of Cu2+ and Cd2+ in soils, and enhanced the Cu2+ and Cd2+ uptake by wheat. EDTA restrained the activity of nitrate reductase (NR), peroxidase (POD), catalase (CAT) in wheat, and enhanced malonyl (MDA) content. HA obviously restrained the availability of Cu2+ and Cd2+ on soils, and restrained the Cu2+ and Cd2+ uptake by wheat. The activity of CAT, POD, NR was restored to normal level, and MDA content also decreased to normal level. There was no significant effect of TA on the availability of Cu2+ and Cd2+and uptake by wheat.