应用生物配体模型研究阳离子及pH值对水稻锌毒性的影响  

Effects of cations and pH in nutrient solution on zinc toxicity to rice( Oryza sativa) root elongation by the biotic ligand model

作　　者：李晓敏[1] 胡莹[1] 黄益宗[2] 刘云霞[1] 李季[1] 

机构地区：[1]中国科学院生态环境研究中心,北京100085 [2]农业部环境保护科研监测所,天津300191

出　　处：《环境化学》2017年第8期1724-1734,共11页Environmental Chemistry

基　　金：国家自然科学基金(21377152)资助~~

摘　　要：采用室内水培实验,通过改变溶液中pH值及主要阳离子(Ca^(2+)、Mg^(2+)、Na+和K+)浓度研究锌对水稻的毒性,建立了Zn对水稻根伸长毒性的生物配体模型(Biotic ligand model,BLM).研究结果表明,增加Ca^(2+)、Mg^(2+)和H+的活度均可以减缓Zn^(2+)对水稻根伸长的毒性,而增加Na+、K+的活度对Zn^(2+)的毒性影响不大;在低pH(4.5—6.0)条件下,主要是Zn^(2+)对水稻根伸长产生毒性,在高pH(6.5—8.0)条件下,Zn^(2+)和ZnOH+是主要的致毒形态.根据生物配体模型理论估算的Zn^(2+)、ZnOH+、Ca^(2+)、Mg^(2+)和H+的生物配体络合的平衡常数分别为:lg KZnBL=4.97、lg KZnOHBL=5.30、lg KCa BL=2.96、lg KMg BL=3.30和lg KHBL=5.21.根据各平衡常数计算可得,当Zn结合水稻的生物配体位点达到73%之后,水稻根伸长的抑制率达50%(即f50=73%).利用上述参数建立的生物配体模型预测的EC50值均在实测值的2倍变化范围之内,表明生物配体模型可以有效地预测锌对水稻根伸长的急性毒性.Acute toxicity of zinc（ Zn） to rice（ Oryza sativa） root elongation was investigated by changing the pH value and major cation（ Ca^2＋,Mg^2＋,Na＋and K＋） concentrations to develop an appropriate biotic ligand model（ BLM） in solution culture. The results showed that the toxicity of Zn^2＋was reduced with increasing avtivities of Ca^2＋,Mg^2＋and H＋,while the avtivities of Na＋and K＋did not significantly affect the Zn^2＋toxicity. The toxicity could be explained mainly by Zn^2＋binding to a biotic ligand（ BL） at pH from 4.5 to 6.0 and by the joint toxicity of Zn^2＋and ZnOH＋at pH from6.5 to 8.0. According to the biotic ligand model（ BLM） concept,the conditional stability constants for the binding of Zn^2＋,ZnOH＋,Ca^2＋,Mg^2＋and H＋to the BL were lg KZnBL= 4.97,lg KZnOHBL= 5.30,lg KCa BL= 2.96,lg KMg BL= 3.30 and lg KHBL= 5.21,respectively. It was calculated that on average 73%of BL sites were occupied by Zn^2＋when the rice root elongation was inhibited by 50%（ f50= 73%）.On the basis of these estimated parameters,the BLM developed in this study could predict EC50 within a factor of 2 of the observed EC50. It was implicated that Zn-BLM could predict reliably the toxicity of Znto rice.

关 键 词：生物配体模型 阳离子 PH 水稻 ZN 

分 类 号：X171.5[环境科学与工程—环境科学] X53