纳米二氧化钛(nTiO_2)与双酚A对斜生栅藻(Scenedes-mus obliquus)的联合毒性效应

The Combined Toxic Effect of Nanoscale Titanium Dioxide(nTiO_2) and Bisphenol A( BPA) on Scenedesmus obliquus

纳米二氧化钛(n Ti O2)在被人们广泛使用的同时,其潜在的环境影响也受到越来越多的关注。为深入探讨n Ti O2与环境中现有污染物的相互作用及生物效应,以斜生栅藻(Scenedesmus obliquus)为受试生物,按照毒性单位法、相加指数法和混合毒性指数法,研究了n Ti O2与双酚A(BPA,一种常见的环境类雌激素)的联合毒性效应。结果显示,n Ti O2与BPA对S.obliquus生长的72 h半抑制浓度(EC50)分别为28.7 mg·L-1与1.81 mg·L-1。而n Ti O2与BPA共存时,在不同毒性比(4:1,3:1,2:1,1:1,1:2和1:3)下,其联合毒性作用(以BPA计)的72 h EC50值分别为2.198,1.58,1.153,0.428,0.306和0.189 mg·L-1。两者的联合毒性作用不仅仅是简单的相加,而是随着两者毒性比的变化,由拮抗作用转变为相加作用,继而转变为协同作用。这表明,n Ti O2进入环境后与现有污染物的毒性比(浓度比)可能是其联合毒性作用模式的一个重要影响因素。

Nanoscale titanium dioxide（n Ti O2） has been widely used in industries such as electronics, optics, and material sciences. However, increasing concerns have been raised in regards to its ecotoxicity and toxicity on the aquatic environment as well as to humans. In order to better understand the interactive effects of n Ti O2 and the existing pollutants in the environment, the combined toxic experiments between n Ti O2 and bisphenol A（BPA, a typical estrogen in aquatic environment） were carried out according to three joint toxicity evaluation methods（toxic unit, additive index and mixture toxic index）, using green algae Scenedesmus obliquus as an experimental model. The results showed that the separate 72 h EC50 of n Ti O2 and BPA for S. obliquus was 28.7 mg·L-1and 1.81 mg·L-1, respectively. When nanoparticles coexist with BPA, the 72 h EC50（showed by BPA） values in different toxic ratios（4：1, 3：1, 2：1, 1：1, 1：2 and 1：3） were 2.198,1.58,1.153,0.428,0.306 and 0.189 mg·L-1, respectively. The results tell us the combined toxic effect was not simply one-step additive. Instead, it depends on the various toxic ratios pattern, the observed toxic effects turned from antagonism to additive effect and then to synergism process. These results indicated that the toxic ratios（concentration ratios） between n Ti O2 and the existing pollutants in the environment would play a key role for determining their combined toxic effects.