Chow Alex T, Leech Dina M, Boyer Treavor H, Singer Philip C
College of Environmental Sciences and Engineering, South China University of Technology, Guangzhou 510641, PR China.
Environ Sci Technol. 2008 Aug 1;42(15):5586-93. doi: 10.1021/es800206h.
The Sacramento-San Joaquin Delta is the major drinking water source for 23 million California residents. Consequently, many studies have examined disinfection byproduct (DBP) formation in relation to Delta dissolved organic carbon (DOC) concentration. However, DOC characteristics within the Delta are not the same as those entering downstream water treatment facilities. As water is transferred to Southern California through the California Aqueduct, a 714.5 km-open channel, it is exposed to sunlight, potentially altering DBP precursors. We collected water from three sites within the Delta and one nearthe California Aqueduct, representing different DOC sources, and irradiated them in a solar simulator at a dose equivalent to that received during four days conveyance in the aqueduct. Photolytic changes in DOC were assessed by measuring CO2 and organic acid production, fluorescence, and ultraviolet absorbance over time. Trihalomethane (THM) and haloacetic acid (HAA) formation potentials, as well as the distribution of hydrophobic, transphilic, and hydrophilic acid fractions were determined at exposures equivalent to one and four days. Solar irradiation significantly decreased ultraviolet absorbance and fluorescence intensity, produced organic acids, and increased the hydrophilic fraction of waters. These changes in DOC caused a shift in bromine incorporation among the THM and HAA species. Our results are the first to demonstrate the importance of sunlight in altering DOC with respect to DBP formation.
萨克拉门托 - 圣华金河三角洲是2300万加利福尼亚居民的主要饮用水源。因此，许多研究都考察了与三角洲溶解有机碳（DOC）浓度相关的消毒副产物（DBP）的形成。然而，三角洲内的DOC特性与进入下游水处理设施的DOC特性并不相同。当水通过714.5公里长的明渠加利福尼亚水道输送到南加州时，它会暴露在阳光下，这可能会改变DBP前体。我们从三角洲内的三个地点以及靠近加利福尼亚水道的一个地点采集了水，这些地点代表了不同的DOC来源，并在太阳模拟器中以相当于在水道中四天输送过程中所接受的剂量对其进行辐照。通过测量随时间变化的二氧化碳和有机酸产量、荧光以及紫外线吸光度来评估DOC的光解变化。在相当于一天和四天的辐照暴露下，测定了三卤甲烷（THM）和卤乙酸（HAA）的生成潜力以及疏水、跨亲和亲水酸组分的分布。太阳辐照显著降低了紫外线吸光度和荧光强度，产生了有机酸，并增加了水的亲水组分。DOC的这些变化导致了THM和HAA物种中溴掺入的转变。我们的结果首次证明了阳光在改变与DBP形成相关的DOC方面的重要性。
