南通长江口北支咸潮上溯对水环境的影响

针对长江口北支近20多年来咸潮超常上溯的状况,通过现场调查监测及与文献资料对比,分析了咸潮上溯对水源地供水水质、河口区河道水质和地下水水质的影响。结果表明,长江口北支咸潮上溯对北支水环境影响主要在于入侵时水体中电导率和氯化物浓度急剧升高,一定程度上影响了北支沿线水源地的供水功能。咸潮对现有水质评价体系下的水质类别影响尚不明显,但高氯离子对化学需氧量的测定有明显的干扰。由于受堤围和水闸控制,咸潮期间入江闸门普遍关闭,导致间接水环境影响,主要集中在入海主河道。部分区域咸潮上溯严重时氯化物浓度升高,水质已不能满足农田灌溉需求。北支沿线启东市24%的地下水采样点氯化物浓度已属轻度入侵水,采样区域已属于海水轻度入侵范围。

The Impact of Saline Water Intrusion on Water Environment in the North Branch of Yangtze River Estuary

According to the situation of the saltwater upwelling in the North Branch of the Yangtze River estuary over the past 2 decades, the influence of the upwelling of the saltwater on the water supply quality of the water source, the water quality of the river channel and the water quality of the groundwater in the estuarine area has been studied through the field investigation and monitoring and the comparison with the literature. The results show that the impact of saltwater upwelling on the water environment of the North Branch of the Yangtze River estuary is mainly due to the sharp increase of conductivity and chloride concentration in the water body during the invasion, which affects the water supply function of the water sources along the North Branch. The influence of salt tide on water quality is not obvious under the existing water quality evaluation system, but the high chloride ion has obvious interference on the determination of chemical oxygen demand. Due to the control of embankments and sluices, the gates into the river are generally closed during the salt tide period. This results in indirect impact on water environment, mainly concentrated in the main channel into the sea. In some areas, when the salt tide is serious, the chloride concentration increases, and the water quality can no longer meet the needs of farmland irrigation. The chloride concentration of 24% groundwater sampling points in Qidong City along the North Branch has been classified as slightly invasive water, and the sampling area has been classified as slightly invasive sea water.