摘要:
工作范围在乌兰布和沙漠北部,面积共约4200km2.年平均降水量85～140mm,由西南向东递增,降水同位素组成δD～δ18O恰与Craig线一致,并与阿拉善地区相同.测得地下水中同位素含量范围,δ18O为-74‰～121‰,氚为0～190TU,14C为17～97pMC.由地下水同位素组成区别出与降水线平行或相交的6种类型.从所有地下水水点,以及可能有补给关系的其它水点的各类同位素关系,包括δ18O,T,δ13C和pMC,识别出两类承压水的各3个补给源和潜水的3个补给源,并区别出一组氚含量极低的潜水,对不同位置的承压水和潜水,由其同位素关系估算出了各补给源的组成和变幅.
关键词:
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地下水
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水资源
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环境同位素
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干旱地区
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沙漠
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内蒙古
Abstract:
The study area of about 4 200 km2 includes mainly the north part of the Wulan-Buhe Desert which is situated to the west of the Yellow River in Inner Mongolia,with an annual mean precipitation of 140 mm to 85 mm from its east to southwest.There are 68 sampling sites for groundwaters.In the relation δD=Sδ18O+d,S=8 and d=10 are get for the precipitation,it is just the same as the WMWL.For the groudwaters,the most δ18O values lie in the range of -7.4‰ to -12.1‰,the tritium content ranges from 0-190TU while the 14C values of 1.7-97 pMC are found.In comparison with the precipitation line,six kinds of groundwater with same or different A and d are found.From the isotopic relationships,four recharge sources are identified for the confined groundwater,i.e.,the paleogroundwater,the spring from fissued rocks of Lang Shan mountainous area situated to the northwest of the Desert,the percolation from the Yellow River,and the deep infiltration water from sand dunes which is formed by precipitation with special mechanism.Three source waters of phreatic groundwater are identified,too.They are the recent precipitation,the early episodic precipitation recharge and the water from sand dunes.The contribution of individual recharge source to the confined/phreatic groundwater at different places is estimated by using the mixing model.
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