Effect Of Submerging And Wetting-Redrying On Cd Speciation And Uptake By Sorghum Hybrid Sudangrass And Switchgrass In Two Paddy Soils Under Spied Cd

The increasing severity of Cd pollution in the soil due to human activities such as sewage waster, sewage earth and fertilizers may have serious consequences for mankind, environment and agriculture. The main way to risk human healthy was to entering the plant by way of soil and directly or indirectly enter the human body. Cd bioavailability was the main factor on the influence of that way. Meanwhile, many results showed that the Cd content absorption by plant was not correlative with the total Cd content but the Cd availability in soils. Therefore, decreasing the content of Cd availability in soils was the key to reduce the amount of Cd entering the plants and Cd toxicity to human healthy. Currently, the reports about pH, organic matter and ameliorants' effect on controlling the mobility were so more, while the studies of water pretreatment on Cd bioavailability was insufficiency.The effect of continuously submerging and wetting-redrying on Cd speciation and uptake by Sorghum Hybrid Sudangrass and Switchgrass in a Ferric-accumulic Stagnic Anthrosol and a Tipical Halpudult collected from the Tai Lake region and the rolling downs of Yingtan, Jiangxi, China respectively, was studied by pot experiment with Cd spike in 2003.The main results obtained were as follow:1 .Compared to that under wetting-redrying treatment, the MgCl2-extracted pool of Cd in Huangnitu with spiked Cd of 5mg.kg-1 and 10 mg.kg-1 was decreased from 21.8% and 28.5% to 8.0% and 16.9% while NH2OH-HCl-extracted pool increased from 17.7% andl7.3% to 28.1% and 37.5% under continuous submerging. However, in the Typical Halpudult, NaAc-extracted pool of Cd decreased from 20.8% and 29.6% to 11.6% and 12.6%, but MgCl2-extracted pool of Cd was the main speciation. There had different Cd distribution after pastures planted, compared to no-plant cultivated, which was that MgCl2-extracted pool of Cd increased, while other three Cd speciation decreased in huangnitu and NaAc-extracted pool of Cd decreased while other three Cd speciation have no obviously different in the Typical Halpudult under continuously submergingpretreatment compared to immediately planted treatment and that MgCl2-extracted pool of Cd increased while NaAc-extracted pool of Cd decreased in paddy soils under wetting-redrying treatment compared to immediately planted treatment. In the totally speaking, after pastures harvested, compared to immediately planted treatment, NH2OH·HCl- extracted pool of Cd was the main speciation in no Cd spiked and MgCl2-extracted pool of Cd in Cd spiked under water pretreatment, but the total content of four extracted pool of Cd was significant decreased.2. In huangnitu, compared to immediately planted treatment, water pretreatment can obviously decreased the Cd absorption by Sorghum Hybrid Sudangrass and Switchgrass by mainly effect on the underground of Sorghum Hybrid Sudangrass and the overground and underground of Switchgrass, while continuously submerging pretreatment had better effect to decreased the pasture absorption of Cd than that of wetting-redrying pretreatment. The main effect speciation was the MgCl2-extracted pool of Cd in huangnitu.3. In the Typical Halpudult, water pretreatment had no obviously effect on Sorghum Hybrid Sudangrass to the absorption of spiked Cd but on the overground of Sorghum Hybrid Sudangrass under low spiked Cd treatment which was mainly effected by MgCl2-extracted pool of Cd. Compared to immediately planted treatment, water pretreatment can obviously decreased the Cd absorption by Switchgrass by the effect on the overground of Switchgrass, but the effect degree between those two water pretreatment had no different. The main effect speciation to Switchgrass absorption of Cd was NaAc-extracted pool of Cd.