The study on Quaternary groundwater resources in Sanmen Bay coastal zone
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摘要: 利用三门湾海岸带最近施工完成的水文地质孔、工程地质孔和地下水碳(14C)测年以及前人的分析研究资料,对三门湾海岸带第四系分布、第四系承压含水层富水性和咸淡水资源分布、承压水年龄和可更新能力进行了深入研究。三门湾海岸带蛇盘滩涂围垦区第一承压含水层(组)富水性较好,绝大部分地区为淡水;宁海县长街镇区域承压水淡水资源总体呈“人”字型分布,北部的大湖−车岙港区域淡水主要分布在第一承压含水层(组)中,在大湖−下洋涂区域淡水主要分布在第二承压含水层(组)中。三门湾海岸带第四系承压水年龄普遍较老。蛇盘滩涂围垦区第一承压含水层地下水年龄为21 642~22 012 cal a BP,未受到后期海侵作用影响;长街下洋涂滩涂围垦区第二承压含水层地下水的年龄为35 052~45 439 cal a BP,部分地段受到后期海侵影响。在目前未开采利用条件下,承压水补给条件差、水资源更新性差。对于拟作为应急供水水源地靶区,应加强地下水资源管理。Abstract: Quaternary distribution, Quaternary confined aquifer productivity, distribution of freshwater and seawater resources, confined groundwater age and renewability are further studied based on recently completed hydrogeological borehole, engineering pores and AMS 14C dating combined with previous data. The first confined aquifer productivity in Shepan tideland reclamation area of Sanmen Bay coastal zone is better, most of groundwater is fresh water. As a whole, freshwater resources of confined aquifer at Changjie Town of Ninghai County are distributed by herringbone patterns. Freshwater resources are mainly distributed in first confined aquifer at Dahu-Cheaogang of north Changjie Town, and freshwater resources are mainly distributed in second confined aquifer at Dahu-Xiayangtu of Changjie Town. The Quaternary confined aquifer ages are generally older. The groundwater ages of the first confined aquifer in Shepan tideland reclamation area are 21 642−22 012 cal a BP, the groundwater is not affected by late transgression. The groundwater ages of the second confined aquifer in Xiayangtu tideland reclamation area are of Changjie Town are 35 052−45 439 cal a BP, the groundwater in partial site is affected by late transgression. Under present unexploited conditions the condition of confined groundwater recharge is bad, the renewability of groundwater resources is not good. Therefore, the management of groundwater resources should be strengthened in emergency water source.
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表 1 蛇盘滩涂围垦区第一承压含水层地下水年龄
Tab. 1 Groundwater ages of the first confined aquifer in Shepan tideland reclamation area
样号 14C/a BP 日历年龄/(cal a BP) 含水层位置/m 水化学类型 矿化度/(g·L−1) 中值 范围(2σ) SW02 17 820 21 642 21 397~21 915 49.2~63.0 Cl·HCO3-Mg·Ca·Na 0.769 SW03 18 060 22 012 21 807~22 201 45.6~59.5 Cl·HCO3-Na·Mg·Ca 0.815 SW11 17 560 21 199 20 962~21 412 51.4~81.0 HCO3-Na 0.506 表 2 长街镇下洋涂围垦区第二承压含水层地下水年龄
Tab. 2 Groundwater ages of the second confined aquifer in Xiayangtu, Changjie town tideland reclamation area
样号 14C/a BP 日历年龄/(cal a BP) 含水层位置/m 水化学类型 矿化度/(g·L−1) 中值 范围(2σ) SW7 30 710 35 052 34 500~35 634 91.0~96.5 Cl·HCO3-Na 1.411 SW13 42 860 45 439 43 822~47 588 98.1~110.5 HCO3·Cl-Na 0.84 -
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