江苏南通地下水补给源、水化学特征及形成机理

Recharge source,hydrochemical characteristics and formation mechanism of groundwater in Nantong,Jiangsu Province

在地下水的大规模开采条件下,江苏沿海一带,特别是南通许多地区的地下水一度出现咸化趋势,对区域水资源及环境产生了极大的影响,已成为制约生态环境建设和经济社会发展的重要因素。为查明地下水的补给来源、水化学特征和矿化度增高的机理,对南通地区深浅层地下水开展了野外调查取样。通过对各种水化学参数的讨论分析,系统地研究了该区地下水的水化学组成特征。从各种水化学组成可以看出,浅层地下水矿化度普遍比深层地下水偏高,沿海一带普遍比内陆地区偏高,中、西部深浅层地下水矿化度都比较低,但东部沿海局部地区地下水咸化现象比较严重。针对这些水化学特征,展开对H、O同位素分布的研究及对各种水化学系数的分析,指出浅层和深层地下水的补给源均为不同条件下的大气降水。淋滤古海相地层盐分和上层咸水下渗是东部沿海深层地下水矿化度增高的主要原因,而中、西部深层地下水总体水质较好,水化学演化以正常的水-岩作用为主。浅层地下水东部沿海寅阳镇、海晏镇受到一定程度的海水入侵影响,水质普遍咸化,其他区域矿化度较高的浅层地下水水化学演化以蒸发浓缩、溶滤地层盐分作用为主。因此,南通东部沿海矿化度增高的区域深层地下水应大力加强保护,特别是随着全球变暖,黄海海平面上升的趋势,东南角寅阳镇、东部海晏镇受海水入侵影响较大的区域更应引起高度重视。

Salinity of groundwater in the coastal aquifers of Jiangsu Province becomes high, especially in some areas of Nantong because of the heavy usage due to economic development. This problem has great impact on the regional water resources and it potentially has high negative effects on the ecological environment, economic and social development. Groundwater samples were collected from the superficial and deep confined aquifers of Nantong to identify the water recharge source, hydrochemical characteristics and evolution mechanism of water chemistry. The total dissolved solids （TDS） of the superficial aquifer is higher than the deep aquifer in most areas, and it is higher in the coastal areas than in inland areas; groundwater of the superficial aquifer in the central and western areas has a low TDS, but the TDS shows very high in some special areas near the coastal region. Oxygen and hydrogen isotopes （D, O） and hydrochemical coefficients indicate that the local precipitation is the recharge source of superficial and deep aquifers. Dissolving salts of ancient marine strata is the major cause that increases the TDS of the deep confined groundwater in eastern coastal areas. The water quality of the deep aquifer in central and western areas is good as a whole, and the hydrochemical evolution is the natural water-rock interaction. The superficial aquifer water in Yinyang, Haiyan areas in southeastern coastal areas shows a very high TDS, to some extend due to seawater intrusion. In other areas, evapor-concentration and dissolving the salts of strata are the dominated hydrochemical evolution patterns of the superficial aquifer. Hence, the deep aquifer groundwater in eastern coastal areas where TDS is high should be protected effectively, especially the salified areas such as Yinyang and Haiyan.