UV-C辐照对河水溶解有机质降解及微生物可利用性的影响

从黄浦江及其上游支流采集表层水样,进行了微生物培养、UV-C辐照和微生物再培养等处理过程,测定水样ρ(DOC)(DOC为溶解有机碳)、紫外可见吸收光谱和荧光光谱,探讨河水DOM(溶解有机质)的光化学降解和微生物可利用性特征. 结果表明:不同处理过程对DOM不同组分去除的贡献率不同,黄浦江河水经微生物培养后,ρ(DOC)和CDOM(有色溶解有机质)含量〔以a₃₃₅(335nm处的吸收系数)计〕分别下降了5%~27%和5%左右,而FDOM(荧光溶解性有机质)含量(以最大荧光强度表示)稍有增加；继续经UV-C辐照24h后,ρ(DOC)和CDOM含量分别下降了7%~36%和79%~96%,而FDOM含量下降了95%以上,说明水体中大部分CDOM和FDOM可通过UV-C辐照去除,并且去除率显著高于微生物降解. UV-C辐照不仅可以降解DOM,而且可以改变DOM的微生物可利用性,其中一部分SLDOM(半活性溶解有机质)经UV-C辐照后能够再次被微生物利用,其中4%~28%的DOC和5%~14%的CDOM可再次被微生物降解. 

Effect of UV-C Irradiation on Dissolved Organic Matter and Its Bioavailability

Laboratory batch experiments of bacterial cultures and ultraviolet-C(UV-C)irradiation were conducted using surface water samples collected from Huangpu River and its upper tributaries. Dissolved organic carbon (DOC) concentrations, UV-Visible absorption spectra and fluorescence spectra were measured to investigate the bioavailability and photodegradation of dissolved organic matter (DOM). The results showed that the removals of DOC, fluorescent dissolved organic matter (FDOM) and chromophoric dissolved organic matter (CDOM) varied with different treatments. Approximately 5%-27% of DOC and 5% of CDOM were consumed during the microbial growth progress. However, the FDOM intensity increased slightly. After 24-hour UV-C irradiation, further loss of DOC (7%-36%) was much lower than those of CDOM (79%-96%) and FDOM (more than 95%). The removal rates of CDOM and FDOM during the UV-C irradiation were much higher than those during the microbial degradation. Besides, some SLDOM (semiactive DOM), which were difficult to be utilized by microorganisms, can be used once again. It indicated that UV-C irradiation can change the bioavailability of DOM. In this study, 4%-28% of DOC and 5%-14% of CDOM were further biodegraded after UV-C irradiation.