土壤中胡敏酸的光化学降解及其对苯并[α]芘结合性质的影响

Photochemical Degradation of Dissolved Soil Humic Acid and Its Effects on Binding Property of Benzo(a)pyrene

在不同光照时间、pH和溶解氧浓度下,研究了土壤中胡敏酸经模拟太阳光照射后对苯并[α]芘结合性质的影响。结果表明胡敏酸经模拟太阳光照射后,其与苯并[α]芘的结合系数K_∝下降。光化过程中胡敏酸的分子量或SUVA_(270)与K_∝之间有较好的指数回归关系。在pH 4.1～8.0范围内,在光照后pH条件下测定经光照处理样品的K_∝值平均下降34.3%±4.1%,在光照前pH条件下测定经光照处理样品的K_∝值平均下降33.8%±8.3%。溶解氧浓度的升高能加速胡敏酸的光氧化降解过程,与相应的未经光照处理样品相比,在空气饱和与氧气饱和条件下光照后的K_∝分别下降37.2%和47.1%。

The effects of photochemical degradation of soil humie acid on the binding property of benzo（a）pyrene were investigated under solar-simulated irradiations, in which the influence of O2 abundance, irradiation time, and pH were discussed in details. The irradiations substantially decreased the binding coefficient Koc, which positively correlated with the molecular weight and aromatieity of humic acid in the time-course of irradiation. After irradiations, Kocdecreased averagely by 33.8% ± 8.3% （determined at the initial pH） and 34.3% ± 4.1% （determined at the post-irradiation pH） respectively in the pH range of 4.1 to 8.0. Increasing O2 abundance accelerated the decrease of the binding coefficient resulted from enhanced photo-degradation of fulvic acids. Compared with the unirradiated sample, the binding coefficient of humic acid-BaP under air-saturated and oxygen-saturated irradiations decreased by 37.2% and 47.1% respectively.