中国北方第四系地下水同位素分层及其指示意义

Groundwater Isotopic Stratification and Its Implications in Northern China

中国北方第四系地下水中的D ,18O ,3 H和14 C含量存在明显的分层现象 ,这种现象与末次冰期以来的古气候变化有着较好的对应性 ,反映了全新世和末次冰期气候条件的差别以及地下水不同的形成机制 .深层地下水为晚更新世末次冰期时期形成 ,其δ(D)和δ(18O)值与全新世补给形成的浅层地下水相比 ,分别贫 4× 10 -3 ～ 16× 10 -3 和 1× 10 -3 ～ 2× 10 -3 ,说明末次冰期时期年均气温较低 .古地下水中D和18O的大陆梯度与全新世以来地下水中的梯度基本相同 ,说明在过去 30 0 0 0a来尽管气温发生变化 ,但中国北方大陆的大气循环模式没有发生实质性的改变 .地下水同位素分层现象反映了 3种不同的补给机制及参与现代水循环程度 .

The underground water compositions of δ (D), δ ( 18 O), 3H and 14 C are distinct in shallow and deep Quaternary aquifers in northern China and reflect differences in average paleoclimatic conditions between the Holocene and the last glacial period of Pleistocene. The recharge of the groundwater in deep confined aquifer during the last glacial period caused δ (D) and δ ( 18 O) to deplete by 4×10 -3 -16×10 -3 and 1×10 -3 -2×10 -3 when compared to shallow aquifer recharged in Holocene, which suggests that annual mean temperature was lower in the last glacial period than that in the Holocene. While the similarity of the continental gradient of δ (D) and δ ( 18 O) found in old groundwater to that in Holocene suggests that atmospheric circulation may not have gone substantial changes over northern China for the past 30 000 years even though the temperature had changed. The fact that groundwater isotopic stratification implies three different recharge mechanisms and influence of modern hydrological circulation is very important for understanding the continental hydrological circulation and sustaining development for groundwater resources.