铊在土壤-根系-水稻系统中的迁移转化过程与机制研究

Thallium (Tl) is a metallic element with greater toxicity to mammals than mercury, arsenic, cadmium, or lead. It is one of the most important objects in the 12th Five-Year Plan on comprehensive prevention and control of heavy metal pollution, but the exploration and utilization of Tl-bearing mineral resources caused soil pollution in the surrounding areas. Thallium fractionation in polluted paddy soils can be obtained by means of indoor simulation experiment and modified BCR sequential extraction procedure. The distribution and combination of Tl in paddy soils which come from typical Tl-bearing mining district in south China can be analyzed by inductively coupled plasma-mass spectrometry(ICP-MS),scanning electron microscopy (SEM), X-ray diffraction (XRD) and fourier-transform infrared (FTIR) spectra. The difference of Tl uptake by rice varieties can be studied and the highest and lowest Tl accumulation rice varieties can be screened out by laboratory incubation and pot culture experiment. A compartmented soil-sand culture system with rhizo-bag can be used to investigate characteristics of Tl accumulation in rhizosphere soil-roots-rice system at key growth stages of the rice variety with the highest and lowest Tl accumulation respectively. Tl polluted paddy soils from typical Tl-bearing mining district in south China can be used to cultivate rice,therefore the changes of iron forms in rhizosphere soils, the changes of iron forms in root surface iron plaque, the amount of root surface iron plaque,the transformation of thallium speciation and the amount of soil fixed thallium can be analyzed. The aim of this research is to investigate the relationship of iron plaque on root surface of rice plants and the bioavailability of Tl, identifying the temporal and spatial distribution of thallium in the rhizosphere soil-roots- rice system of two rice varieties and to study the formation of dynamic of root surface iron plaque and the effect of the root surface iron plaque adsorption on uptake of thallium in rice plant. The research results will preliminary clarify the migration and transformation laws of thaillum in rhizosphere soil-roots-rice system, and have an important reference value for the prevention and control of thallium contamination paddy soils.

铊是毒性大于Hg、As、Cd、Pb的一种有毒金属元素，是重金属污染综合防治"十二五"规划的重点对象之一，但含铊矿产资源开发利用已导致矿区周边土壤污染。本项目拟通过室内模拟试验和改良的BCR法提取不同形态铊，利用ICP-MS、SEM、XRD、FTIR等分析手段，研究华南典型含铊矿区水稻土中铊的形态分布特征及其结合方式；采用土培实验模拟含铊水稻土，筛选出对铊的高、低吸收品种；以矿区含铊水稻土为研究对象，采用土-砂根袋培养模拟试验，分析铊高、低吸收品种水稻的关键生育期根际土壤铁形态、根表铁膜的铁形态、根表铁膜量以及铊形态的动态变化和铊固定量；探讨水稻根表铁膜与铊生物有效性的关系，明确铊在吸收累积能力不同水稻根际土-根系-水稻体内的时空分布规律，研究水稻根表铁膜形成动态及其对铊吸附和吸收的影响。通过本项目研究，可初步明确铊在土壤-根系-水稻体系中的迁移转化规律，为水稻土铊污染防控等提供相应参考。

铊是毒性大于Hg、As、Cd、Pb的一种有毒金属元素，是重金属污染综合防治“十二五”规划的重点对象之一，但含铊矿产资源开发利用已导致矿区周边土壤污染。本项目通过室内模拟试验和改良的BCR法提取不同形态铊，利用ICP-MS、SEM等分析手段，研究华南典型含铊矿区水稻土中铊的形态分布特征及其结合方式；采用土培实验筛选出对铊的高、低吸收品种；以矿区含铊水稻土为研究对象，采用土-砂根袋培养模拟试验，分析铊高、低吸收品种水稻的根际土壤铁形态、根表铁膜量以及铊形态的动态变化；探讨水稻根表铁膜与铊生物有效性的关系，明确铊在吸收累积能力不同水稻根际土-根系-水稻体内的时空分布规律，研究水稻根表铁膜形成动态及其对铊吸附和吸收的影响。.分析了云浮矿区24个采样点水稻土0-60cm深度范围内pH、CEC、OM和铊的垂直分布特征以及水稻植株根、茎、叶和稻米中铊与土壤铊含量的相关性。结果表明水稻土、植株根、茎、叶和稻米铊含量均超出规定水平，在0－30cm深范围内水稻土铊含量随深度增加而增加，30－60cm深范围内随深度增加而减少。土壤铊含量与pH存在显著的负相关性，铊在植株中不同部位的含量具有根>叶>茎（稻米）的特点，而且根中铊的含量与叶和稻米中铊含量呈显著的正相关性。研究了不同形态Tl含量与水稻土总Tl含量的相互关系，结果表明云浮矿区水稻土Tl以铁锰氧化物结合态为主，总Tl含量与不同形态Tl含量呈显著正相关。探讨了沸石和五种生物炭对Tl的吸附动力学及吸附机制，结果表明与沸石及其它生物炭相比，榕树叶生物炭有较好的吸附效果；以15个广东地区栽培的水稻品种为研究对象，探明了这些品种水稻对Tl的累积特征，筛选出粤农丝苗和Y两优321两个高、低吸收Tl的水稻品种；研究了水稻根表铁氧化物形成动态及其对Tl吸附和吸收的影响，结果表明根表铁氧化物形成数量与其富集Tl的量呈正相关，水稻根系形成铁膜数量与水稻根系中Tl浓度呈正相关。对龙葵作为铊的修复植物进行了研究，结果表明龙葵对于中度铊污染的土壤（<10mg•kg-1）有较好的修复潜力。通过本项目的研究，初步明确了铊在土壤-根系-水稻体系中的迁移转化规律，为水稻土铊污染防控等提供了相应参考。