景观河道病原微生物分布特征及其与环境因子的关系

鉴于当前城市人口密集、公众与景观水体接触日益增多、水体整体环境较差的现状,为正确评价景观河道环境现状,以上海市中心城区3条不同营养状态及功能河道为例,选取2017年汛期5场连续降雨,分析了河道病原微生物的分布特征及其与环境因子的相关关系。结果表明,劣Ⅴ类水质的河道a晴天粪大肠菌群平均浓度为1.72×10~3MPN/mL,雨天为3.34×10~3MPN/mL,水质较好的河道b和河道c晴天与雨天粪大肠菌群平均浓度保持10~2MPN/mL。晴天3条河道大肠菌群平均浓度相差2个数量级,河道a为5.15×10~3CFU/mL,河道b和河道c分别为30 CFU/mL和99 CFU/mL;雨天大肠菌群平均浓度河道a为1.04×10~5CFU/mL,河道b和河道c分别为289 CFU/mL和147 CFU/mL。在变化趋势上,降雨导致粪大肠菌群和大肠菌群浓度增加,但大肠菌群浓度增加的程度明显高于粪大肠菌群。相关分析显示,3条河道内粪大肠菌群和大肠菌群与环境因子相关性存在一定差异,但基本都表现为与TN、TP和NH_3-N显著正相关,控制河道氮磷营养水平能显著抑制病原微生物增殖。

Distributions of Coliform and Fecal Coliform in Three Urban Rivers and the Influence of Environmental Factors

Microbial contamination by water-borne pathogens is one of the most serious health hazards in the world today and a key determinant of surface water quality. Previous studies have shown that the overall water environment is poor in urban rivers and stormwater runoff is frequently the primary source of bacteria. In this study, the water quality and indicator microorganisms in three urban rivers in central Shanghai City, with different nutritional status and primary functions, were monitored following five rainfalls during the flood season of 2017. The distribution of pathogenic microorganisms and their correlation with environmental factors were analyzed during precipitation events and in dry weather. Water samples were collected at five sites in the three rivers: Sites A-C were in River a and located, respectively, 500m above a pumping station outfall, in the mixing area of the outfall and 500m below the outfall; Site D and E were located in the middle reach of Rivers b and c. Two water samples were collected at each site, one for determination of water quality parameters (SS, CODcr, BOD5, TP, TN and NH3-N) and the other for determination of microbiological indicators, fecal coliform (FC) and total coliforms (TC). The average fecal coliform count in River a was 1.72×103 MPN/mL in dry weather and 3.34×103 MPN/mL during rain, neither meeting the Class V water quality standard. The average fecal coliform counts in River b and c remained at 102 MPN/mL in both dry and wet weather. In dry weather, the average coliform count in River a was 5.15×103 CFU/mL, two orders of magnitude higher than in River b (30 CFU/mL) and River c (99 CFU/mL). In wet weather, the average coliform count in River a was 1.04×105 CFU/mL,289 CFU/mL in River b and 147 CFU/mL in River c. Rainfall increased fecal coliform and coliform counts in all three rivers, but the increase in counts was significantly higher for coliform than fecal coliform. The correlation between fecal coliform and environmental factors was different from the correlation between coliform and environmental factors, but both displayed a significant positive correlation with TN, TP and NH3-N. These results indicate that controlling nitrogen and phosphorus levels can significantly reduce the proliferation of pathogenic microorganisms. This study provides basic data for evaluating the current condition and health risk of urban rivers.