摘要
根据2000年丰水期和2001年枯水期银川平原地下水、河水的同位素测试结果,分析了该地区地下水的同位素组成特点。研究结果发现,银川平原中浅层地下水与深层地下水具有不同的水循环模式。山前洪积倾斜平原中地下水为当地雨水补给。冲洪积和河湖积平原中潜水的主要补给来源为黄河灌溉水,潜水受到蒸发作用的影响比较明显,而且沿地下水流方向,潜水蒸发作用逐渐增强;承压水为古地质时期补给形成的。承压水地下水水位漏斗区中,承压水δ18O和3H浓度较高的现象反映有潜水向承压水的越流排泄。银川平原中浅层地下水积极参与现代水循环,其更新时间为30年;14C的证据表明该区承压水为地质历史时期形成的古地下水,其年龄大于2000年。潜水的更新能力明显大于深层承压水。
The knowledge about groundwater renewablity is the important basis for evaluating the groundwater resources and establishing the reasonable developing pattern of groundwater resources. Isotope tracing is one of the mostly adopted advanced techniques in research of hydrological cycle. Based on the isotope analysis result of the groundwater and river water samples in rainy season of 2000 and dry season of 2001 in Yinchuan basin, this paper shows that the shallow and deep groundwater have different water cycle patterns. The isotopes such as δ^(18)O and ()~3H of the phreatic water in the inclined mountain apron are very close to that of the local precipitation, which signifies that the origin of the phreatic water here is meteoric water. The δ^(18)O and ()~3H concentration of the phreatic water in the alluvial plain and lacustrine plain is very close to the Yellow river water. In the transect along the groundwater flow direction, δ^(18)O has a general 'U' distribution but ()~3H has a 'n' distribution, which is very different from that in the large groundwater basin. All of these imply that the phreatic water in these areas is mainly recharged by the irrigated river water through canal and field infiltration. In the diagram of δ^(18)O and ()~δD, all the phreatic water samples are distributed along the evaporative line with high correlation, which signifies that evaporation has an obvious effect on the isotopes of the groundwater. Isotopic evidence shows that he evaporation effect becomes more and more intensive along the groundwater flow direction. The confined water of free tritium is formed in the paleo-geologic time with lower ratios of hydrogen and oxygen isotopes than the shallow groundwater. But in the cone of groundwater depression, the higher δ^(18)O and ()~3H concentration of the confined water samples implies the result of leakage from the upper unconfined aquifer. The result of the Tritium mathematical physical model calculation shows that the mean residence time of the phreatic water in the shallow aquifer in Yinchuan plain is about 30 years. The deep paleo-groundwater has the ()^(14)C-correction age of more than 2000. The fact that the circulation time of the phreatic water in shallow aquifer is lower than that of confined water in deep aquifer shows that the renewablity of the shallow groundwater is larger than that of deep confined water.
出处
《资源科学》
CSSCI
CSCD
北大核心
2004年第2期29-35,共7页
Resources Science
基金
国家(973)重点基础研究发展规划项目(编号:G1999043606)
高等学校博士点学科专项研究基金资助项目(编号:2000002712)。
