为探寻适合广东省典型镉(Cd)污染稻田土壤镉生物有效性测定方法及其管控阈值,以广东韶关、清远和广州三种典型Cd污染稻田土壤为供试土壤,系统比较了四种有效Cd提取方法(CaCl2法、HCl法、EDTA法和DTPA法)对土壤Cd的浸提能力,并分析两个品种水稻对Cd的累积吸收量与土壤有效Cd含量的相关性,探讨糙米Cd超过食品安全标准时各测定方法的风险管控值.结果表明,四种化学提取剂对土壤Cd的提取能力大小依次为0.1 mol·L-1 HCl>0.05 mol·L-1 EDTA>0.005 mol·L-1 DTPA>0.1 mol·L-1 CaCl2;外源添加条件下土壤Cd有效性高,土壤总Cd和各提取态Cd均与糙米Cd极显著相关(P<0.01),四种有效Cd测定值与水稻Cd累积量的相关系数均超过0.9,其中CaCl2提取态Cd与水稻Cd含量的相关性更强,但自然污染型土壤全Cd含量与水稻Cd累积量的相关性最弱;根据各方法测定值与糙米Cd相关性计算获得了广东Cd污染稻田的风险管控值.采用四种有效Cd测定方法评价广东酸性稻田土壤Cd的生物有效性优于土壤全Cd的方法,其中CaCl2提取法测定的结果与稻米Cd含量相关性最高,进一步深入研究可确立基于0.1 mol·L-1 CaCl2提取态Cd含量的稻田Cd污染风险管控阈值.

Excessive cadmium (Cd) in rice grain has become a major global public health problem. Here, the effect of foliar glycerol application on Cd accumulation in brown rice was examined. Various spraying concentrations of glycerol between 0.4mM and 50mM were investigated and the results showed that 0.8 mM was the best application concentration for decreasing Cd content in brown rice. After different application period experiment, filling stage was considered as the optimal spraying time. 0.4mM-5mM glycerol application one time at the filling stage could significantly reduce Cd concentration in brown rice by 28.5%-60.4%. Cd transport factors (the ratio of brown rice and flag leaf/node) were decreased by 48.5% and 27.3%, respectively, with glycerol application. Glycerol application also significantly increased Cd concentration in soluble fraction in flag leaf while reduced inorganic Cd and water-soluble Cd in both flag leaf and stem. Our results showed foliar spraying glycerol inhibited Cd transport to brown rice through Cd compartmentalisation in the vacuole and transformation of cadmium chemical form. This study may provide a new method to effectively alleviate the problem of excessive Cd in rice. (C) 2020 Elsevier Ltd. All rights reserved.

在研究生思想政治教育中,导师作为首要责任人,发挥着不可或缺的重要作用.但在实际工作中,因为导师对自身角色和作用的认识模糊、考核评价制度的不完善、缺乏导师与辅导员沟通交流的长效机制等种种原因,导师的作用还没有得到真正的落实和发挥.对此,可以通过端正和强化导师对自身角色和作用的认识、健全和完善考核评价制度、建立导师与辅导员沟通交流的长效机制等途径加以解决.