pH对不同来源溶解性有机质光致生成活性物种量子产率的影响

Effect of p H on the quantum yield of reactive photo-induced species generated in different sources of DOM

溶解性有机质(DOM)普遍存在于地表水中,DOM吸收太阳光可生成多种光致活性物种(RPS),如激发三线态DOM(~3DOM*)、单线态氧(~1O_2)和羟基自由基(·OH)等.这些RPS对污染物的降解具有重要作用.天然水p H改变可导致DOM的粒径、官能团和分子量等变化,但p H对DOM生成RPS的影响少有研究.本文在模拟日光条件下,采用分子探针的方法测定了提取的黄海海水DOM(L-DOM)和两种购于国际腐殖酸协会的DOM(NAFA和SRHA)在p H值为4.0、7.0和9.0条件下生成~3DOM~*,~1O_2和·OH的量子产率.结果表明,3种DOM均可光致生成RPS,L-DOM生成RPS的量子产率远高于SRHA和NAFA.p H对不同来源DOM生成RPS的量子产率的影响不同,其中对L-DOM的影响最为显著.本研究有助于揭示水中有机污染物的光化学转化动力学.

Dissolved organic matter （DOM） exists widely in surface waters. DOM can absorb sunlight to generate reactive photo-induced species （RPS）, such as triplet excited DOM （3DOM＊）, singlet oxygen （1 O2 ） and hydroxyl radicals （ · OH）. These RPS is important for the degradation of organic micropollutants. It is known that variation in pH of natural waters can change the size, structure and molecular weight of DOM. However, the relation between in pH and photogeneration of RPS by DOM has been rarely investigated. In this study, the effect of pH on the quantum yield of 3 DOM ＊ , 1 O2 and · OH was investigated. DOM isolated from Yellow Sea （L-DOM） and two DOM purchased from the International Humic Substances Society （NAFA and SRHA） were used in the study. Molecular probes were employed to determine the formation of the RPS by DOM irradiated by simulated sunlight. Results show all the DOM were capable of photogenerating RPS, and the RPS quantum yield of L-DOM was higher than that of NAFA and SRHA. The effects of pH on the RPS quantum yield of three sources of DOM was different, and the influence of pH on RPS quantum yield of L-DOM was most significant. The study helps to predict photodegradation kinetics of organic pollutants in water.