复合改良剂对稻田Cd、As活性与累积的协同调控

为同时降低水稻糙米中Cd、As含量,以达到国家标准食品污染物限量标准,选取湘南某矿区Cd-As复合污染稻田土壤,以盆栽实验研究复合改良剂QFJ(羟基磷灰石+沸石+酸改性炭化秸秆)对土壤中Cd、As生物有效性及对水稻各部位累积Cd、As的影响,探讨QFJ对土壤Cd、As生物活性与稻米Cd、As累积的协同调控.结果表明:施用QFJ降低了水稻糙米中的Cd、As含量,施加量2g/kg时,糙米中Cd、As含量分别为0.19mg/kg和0.14mg/kg,均低于对照组的0.49mg/kg和0.27mg/kg,且同时低于0.2mg/kg,达到了国家标准食品污染物限量标准.施用QFJ提高了土壤pH值0.02~0.68单位,增加了土壤CEC、OM含量,同时土壤中Cd 的酸可提取态、交换态及TCLP提取态含量分别降低了7.3%~32.5%、12.6%~39.8%和40.7%~60.1%,对As的交换态和TCLP提取态含量的影响趋势是先降低后增大.糙米中Cd含量与土壤中Cd的3种提取态含量存在极显著正相关关系,As含量与其土壤中TCLP提取态含量存在极显著正相关关系.当QFJ施加量在2g/kg水平时,土壤中Cd、As的生物活性可协同控制在较低水平,从而同时降低了糙米中Cd、As含量.施用QFJ使得Cd在水稻根表铁膜中的含量呈增大趋势,在水稻其他部位含量呈减小趋势;As在谷壳中含量呈减少趋势,在其他各部位呈先减小后增大的趋势.水稻吸收的Cd和As大部分累积在根部和茎叶部,各部位Cd累积率大小是白根 > 茎叶 > 糙米 > 谷壳,As是茎叶 > 白根 > 糙米 > 谷壳.根据Cd-As污染程度不同,可考虑施用2~4g/kg QFJ以达到水稻的安全生产.

Synergistic control of combined amendment on bioavailability and accumulation of Cd and As in rice paddy soil

To reduce the contents of Cd and As in brown rice, meeting requirements of the National Food Standards (GB 2762~2012), a pot experiment was conducted to study the synergistic controlling effects of combined amendment QFJ (hydroxyapatite + zeolite + biochar) on the bioavailability of Cd and As in contaminated paddy soil collected from a mining area in southern Hunan and on the accumulation of Cd and As in the various organs of rice plants. The results showed that application of QFJ could reduce the contents of Cd and As in brown rice. When QFJ applying at a 0.2%, the contents of Cd and As in brown rice were 0.19mg/kg and 0.14mg/kg, respectively, lower than those of 0.49mg/kg and 0.27mg/kg in the control group, and also lower than 0.2mg/kg, meeting the requirements of the GB 2762~2012. Application of QFJ increased soil pH values (ranging 0.19~0.79), soil CEC, and soil OM. Meanwhile, compared with the control, the contents of acid extractable, exchangeable and TCLP extractable soil Cd were decreased by 7.3%~32.5%, 12.6%~39.8% and 40.7%~60.1%, respectively, resulting in a reduction in the bioavailability of soil Cd. However, the contents of exchangeable and TCLP extractable soil As were declined firstly and then increased. The Cd contents in brown rice showed significant positive correlations with the contents of acid extractable, exchangeable and TCLP extractable soil Cd. The same correlation was only found for the As contents in brown rice and the contents of TCLP extractable soil As. These explained that the bioavailability of soil Cd and As could be synergistic controlled at 0.2% of QFJ application, resulting in reducing the accumulation of Cd and As in brown rice simultaneously. In addition, application of QFJ significantly increased Cd contents in the iron plaque outside roots of rice plants, and decreased Cd contents in the other rice organs; meanwhile, As contents were decreased in the rice hulls, and decreased in the other rice organs firstly and then increased. Most Cd and As in rice plants were accumulated in the roots and stem-leaves. The sequence of Cd accumulation in the rice organs was root > stem-leaf > brown rice > hull, and that of As accumulation was stem-leaf > root > brown rice > hull. For the safe production of rice, 0.2%~0.4% of QFJ was supposed to apply to paddy soils dependent on the Cd-As pollution level of the soils.