苏北平原隐伏玄武岩地下水研究

针对苏北平原地表水污染严重,深层承压水成为主开采层,在大量抽取地下水之后,依然存在高水位地区的问题,对连云港、淮安、扬州、泰州和盐城等地的河水、地下水进行采样,测试分析了样品的氢氧同位素以及水化学特征。结果表明:苏北平原承压水氢氧同位素相对于地表水和浅层地下水贫化,并非来自当地降水下渗以及上部含水层越流补给,补给源具有明显的同位素贫化的特征；地下水接受现代降水补给,承压水中测到明显的来自核试验的氚；地下水水岩反应以硅酸盐反应为主,上新世以来东亚地区发生了多期火山喷发,第四纪地层下的隐伏玄武岩地区可能是深层地下水发生水岩反应并产生偏硅酸的主要含水层,而后这些富含偏硅酸的地下水通过断裂带运移到第四纪承压含水层中。

Study on the concealed basalt groundwater in Subei Plain

The surface water Subei Plain was polluted eriously, and the deep confined groundwater becomes the main exploitation aquifer, but high-water levels areas still exist after the extensive groundwater extraction. In order to investigate the cause of this phenomenon, the hydrogen and oxygen isotopes as well as water chemistry of river water and groundwater in Lianyungang,Huaian, Yangzhou, Taizhou and Yancheng were sampled and analyzed. The results showed that the hydrogen and oxygen isotopes of confined water in the Subei Plain are depleted relative to the surface water and the shallow groundwater, rather than from local infiltration of precipitation and recharge of the upper aquifer by transgressive flow. The recharge source is characterized by the obvious isotope depletion. Tritium dating data indicates that the groundwater receives modern precipitation recharge and apparent tritium from nuclear testing has been detected in the confined water. The large amount of metasilicic acid in the deep groundwater indicates that the groundwater water-rock reaction is dominated by the silicate reaction. Because multiple volcanic eruptions have occurred since the Pliocene in the northern Jiangsu area, the area of occult basalt beneath the Quaternary strata may be the main aquifer where deep groundwater reacted with water-rock to produce the metasilicic acid, and these metasilicic acid-rich groundwater then transported through the faults to the Quaternary confined aquifer.