Temporal And Spatiat Variations Of Dissolved Organic Matter And Disinfection Byproduct Precursors In The Pearl River, China

During the disinfection process, commonly used chlorine-containing disinfectantswould react with different organic components in water and produce a variety ofcarcinogenic and mutagenic disinfection byproducts (DBPs). The reaserches of drinkingmainly focus on the natural organic matter (NOM)，but few researches on the fractionsof DOC and its relationship with precursors of DBPs has been done in the Pearl River.In the two-year quarterly monitoring study between2009and2010, our research teamcollected water samples from a total of29sites along West River (Wuzhou, Deqing,Zhaoqing), North River (Shaoguan, Yingde, Qingyuan), East River (Heyuan, Huizhou,Dongguan), and the tributaries confluence (Guangzhou). Water samples were analyzedin terms of DOC concentration, pH，UVA254and electrical conductivity (EC). DOC inthe Pearl River System in Guangdong Province was further fractioned using XAD resinsinto hydrophobic acid (HPOA), hydrophobic neutral (HPON), transphilic acid (TPHA),transphilic neutral (TPHN) hydrophilic acid (HPIA). In addition, the species andTHMFP were determined by applying Uniform Formation Condition Test (UFC).Results showed that the concentration of DOC in the Pearl River ranged from0.7to33.0mg·L-1. The distribution order of DOC was as follow: West River (0.7~4.3mg·L-1)<North River (1.3~12.8mg·L-1)<East River (0.7~20.5mg·L-1)<theconfluence (8.5~33.0mg·L-1). On the spatial distribution, under the influence of runoffand sewage emissions around, all tributaries of the DOC concentrations graduallyincreased along the downstream direction. On the temporal distribution, only DOCconcentration of the downstream cities such as Guangzhou showed distinct seasonalchanges. While the upstream cities had no significant change, as their flow was muchhigher than the downstream city. In the Chlorine experiment, the THMFP in the PearlRiver (30.39~1091.52μg·L-1), was linearly related to DOC concentration. Therefore,temporal and spatial distribution of THMFP was basically the same as DOC. After XADseparation, HPO was found the main fration of DOC (42.0%±0.8%) and the maindisinfection by-product precursor in the Pearl River (accounting for64.6%of trihalomethane in the Pearl River), whose specific trihalomethanes formation potential(STHMFP) was more than twice than that of the other organic components. In theanalysis of THMs species, a higher ratio of bromo-THMs was found in Guangzhou,indicating that water there contained a high concentration of bromide ions. In addition,UVA254were linearly related to DOC concentration and THMFP, which suggests thatUVA254is the important indicator for the research of drinking water.