大亚湾南海石化排污口海域海水总有机碳的分布特征

2013年7月22、23日对大亚湾南海石化排污口海域进行了采样调查，分析了大亚湾南海石化排污口海域海水中总有机碳（TOC）、CODMn、石油类和叶绿素 a 含量的分布特征及排污口处连续12 h 的变化趋势，并讨论了大亚湾南海石化排污口海域 TOC 与 CODMn、石油类和叶绿素 a 等环境因子之间的关系。监测结果显示，大亚湾南海石化排污口海域12个调查站位的 TOC 含量在1．23～1．49 mg／L，各站点差异不大，基本处于同一水平。1号站位连续12 h 监测结果显示，TOC 含量在1．30～1．57 mg／L，各时段差异不大，基本处于同一水平。南海石化排污口附近的站点所监测到的 TOC、CODMn及石油类并没有出现明显的高值，与其他站位监测结果差别不大。监测数据分析结果表明南海石化排污未引起该海域明显有机污染。大亚湾南海石化排污口海域海水中 TOC 与石油类呈显著正相关，与 CODMn亦呈正相关但未达显著程度。

Distribution of Total Organic Carbon in Wastewater Discharged from Daya Bay Petrochemical Industrial Zone to the South China Sea

Total organic carbon is a comprehensive index of the degree of organic pollution in a water body and can be used to evaluate organic pollution in the sea. Huizhou Daya Bay petrochemical industrial area is world-class and the wastewater from this industrial area is discharged, after standard treatment, into the northeast sea area of Sangzhou Island and the northwest sea area of Bijia Port. The primary contaminant is petroleum wastes, causing a high chemical oxygen demand (COD), and this has become the most critical concern of all the interested parties since the industrial area was put into production. In this study, we investigated the spatial distribution and temporal changes in four water quality parameters in Daya Bay near the petrochemical wastewater outlet; total organic carbon (TOC), permanganate chemical oxygen demand (CODMn), oil and chlorophyll-a (Chl-a). TOC was determined on a Liqui TOC analyzer, CODMn and petroleum content were determined according to the national marine measurement standard (GB17378.4-2007), and Chl-a concentration was detected by the fluorescence method. The correlation between TOC and the other three parameters was analyzed using SPSS software to help understand the organic pollution level and provide scientific data to better protect the environment and conserve the ecology of Daya Bay. Twelve monitoring stations (No.1-No.12) were selected in the study area and samples were collected at 0.5m below the surface on July 22, 2013. Hourly sampling over 12 hr for the same parameters at station No.1 was conducted on July 23 (08:00-19:00). TOC concentration in the study area ranged from 1.23 to 1.49 mg•L-1, with no significant differences among the twelve monitoring stations. The hourly samples collected at station No.1 ranged from 1.30 to 1.57 mg•L-1, indicating little temporal variation in TOC concentration. No elevated levels of TOC, CODMn or oil pollution were detected in the waters around the Daya Bay petrochemical wastewater outlet, indicating that petrochemical wastewater discharges do not cause obvious organic pollution. Correlation analysis reveals a significant positive correlation between TOC concentration and oil pollution, and positive correlation was also observed between TOC and CODMn, but was not statistically significant. It is well known that TOC is associated with many environmental variables including monsoon rains and seasonal runoff, hydrodynamic factors, biogeochemistry and biology. This study is a preliminary exploration of the feasibility of TOC as organic pollutant indicator for the waters around Daya Bay petrochemical wastewater outlet because of insufficient monitoring frequency and samples. Further study must be carried out in terms of the feasibility of TOC as organic pollution indicator and the accuracy of TOC for organic pollution assessment in Daya Bay.