Effects of Amendments on Soil Cd Effectiveness and Rice Cd Accumulation in Paddy Fields in Central of Hunan Province
This study aimed to reveal the effects of different amendments on the Cd effectiveness and rice Cd accumulation with different Cd contamination levels in paddy fields in central of Hunan province,and screen immo-bilization materials suitable for safe utilization in lightly/moderately Cd-contaminated farmlands in central of Hunan province.Hence,two contaminated soils were selected,and four modified or composite materials,i.e.,sulfhydry-lated seafoam(SGP),seafoam composite(ISS),iron-modified woody peat(IMP),and bioorganic fertilizer(OF),were chosen as passivating agents.Effects of the four immobilization materials on soil pH,soil organic mat-ter,soil Cd form,soil effective state Cd content,and Cd contents in various parts of rice during different periods of time were comparatively investigated under two different test conditions,namely,field plot tests and pot tests.Re-sults show as follows.1)In pot trials,compared with CK,the soil effective Cd contents reduce by 1.59%～25.40%,3.57%～26.79%,and 15.67%～37.32%at the tillering,filling,and maturing stages of rice,respectively.The weak acid extractable Cd content reduces by 4.29%～7.27%in the maturing stage of rice,the Cd content in the oxidizable state increases by 6.86%～11.00%,and the Cd contents in the rice root,stem,and husk decrease by 26.45%～44.34%,35.79%～59.01%,and 21.24%～45.36%,respectively.The root enrichment coefficients are in the range of 0.24～0.32.2)In field trials,compared with CK,the soil pH treated by ISS and OF at the filling and tillering stages of rice increases by about 0.3.The effective state Cd contents of soil reduce by 15.11%～35.95% and 27.19%～49.24%at the filling and maturity stages of rice,respectively.The Cd contents in the rice root,stem/leaf,and brown rice reduce by 61.29%～84.86%,41.00%～84.42%,and 26.47%～85.29%,respectively.The enrichment coefficients of rice root and brown rice are in ranges of 0.13～0.32 and 0.04～0.20,respectively,and the rice root-stem and stem-shell transfer coefficients are in ranges of 0.18～0.31 and 0.32～1.11,respectively.The results of this study show that the application of SGP,IMP,and ISS treatments significantly reduces the soil ef-fective state Cd content and the enrichment coefficient of soil Cd in rice,and affects the translocation uptake of Cd by various parts of rice,thus reducing the uptake and accumulation of soil Cd by the plant,enriching Cd in leaf,and reducing its accumulation in rice.The ISS treatment can significantly increase soil pH.
composite materialCdriceavailabilityuptake and transportfractionation
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