为更好地认识和预测淡水环境中砷的生态风险,通过室内培养实验分析了铜绿微囊藻在溶解态无机磷(DIP)和有机磷[腺苷-5'-三磷酸二钠盐(ATP-P)、β-甘油磷酸钠(β-P)]这3种不同磷源下的生长差异,并探讨了不同磷源下藻细胞对砷酸盐[As(Ⅴ)]的胁迫响应.结果表明,该藻在不同磷源下均可进行生长繁殖,且在前5 d内无明显差异;之后与DIP相比,有机磷(DOP)源下的藻细胞增殖相对较差;培养7 d时β-P和ATP-P环境下藻体光密度(D)分别只有DIP的78.0%和75.4%.各磷源下藻体实际光能转化率(Yield)与叶绿素a(Chl-a)和D的负相关表明Yield不能作为藻体营养缺乏与否的稳定性衡量指标.不同磷源下藻体对As(Ⅴ)胁迫的响应因磷形态不同而表现出明显差异,Yield能很好地表征这种胁迫响应.由D、Yield和Chl-a得出铜绿微囊藻对As(Ⅴ)的96 h EC_(50)均表现为DIP>β-P>ATP-P;β-P和ATP-P条件下其对As(Ⅴ)的耐受性较为接近,但与DIP相比差1~5个数量级.
The gas phase hydration of glyoxal （HCOCHO） in the presence of sulfuric acid （H2SO4） were studied by the high-level quantum chemical calculations with M06-2X and CCSD（T） theoretical methods and the conventional ...
详细信息
The gas phase hydration of glyoxal （HCOCHO） in the presence of sulfuric acid （H2SO4） were studied by the high-level quantum chemical calculations with M06-2X and CCSD（T） theoretical methods and the conventional transition state theory （CTST）. The mechanism and rate constant of the five different reaction paths are consid- ered corresponding to HCOCHO＋H2O, HCOCHO＋H2O… H2O, HCOCHO… H2O＋H2O, HCOCHO＋H2O… H2SO4 and HCOCHO… H2O＋H2SOa. Results show that H2SO4 has a strong catalytic ability, which can significantly reduce the energy barrier for the hydration reaction of glyoxal. The energy barrier of hydrolysis of glyoxal in gas phase is lowered to 7.08 kcal/mol from 37.15 kcal/mol relative to pre-reactive complexes at the CCSD（T）/6- 311＋＋G（3df, 3pd）//M06-2X/6-311＋＋G（3df, 3pd） level of theory. The rate constant of the H2SO4 catalyzed hydrolysis of glyoxal is 1.34×10-11 cm3/（molecule.s）, about 1013 higher than that involving catalysis by an equal number of water molecules, and is greater than the reaction rate of glyoxal reaction with OH radicals of 1.10×10-11 cm3/（molecule·s） at the room temperature, indicating that the gas phase hydrolysis of glyoxal of H2SO4 catalyst is feasible and could compete with the reaction glyoxal＋OH under certain atmospheric condi- tions. This study may provide useful information on understanding the mechanistic features of inorganic acid-catalyzed hydration of glyoxal for the formation of oligomer.
暂无评论