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湖泊和海洋沉积物中正构烷烃氢同位素作为有潜力的古水文和古气候指标已经得到广泛应用,但是在干旱区由于蒸发强烈而严重影响正构烷烃氢同位素比值,因此其能否记录降水同位素变化受到质疑.本研究在青藏高原干旱区采集了21个湖泊表层沉积物(其中20个湖泊年平均降水量<400 mm),发现其正构烷烃氢同位素(δD_(wax))与年均降水平均氢同位素(δD_(ann))呈现较强相关(r~2=0.84,P<0.001),其与夏季降水平均氢同位素(δD_(sum))相关性更好(r~2=0.91,P<0.001),说明降水是控制湖泊沉积物中正构烷烃氢同位素(δD_(wax))变化的主要因素,在干旱地区正构烷烃氢同位素(δD_(wax))仍然可以反映降水氢同位素(δD_p)信息.本研究中湖泊表层沉积物正构烷烃和降水之间的氢同位素表观分馏平均值(ε_(wax-p))为-113‰,较湿润地区偏正,可能是由于干旱区蒸发强烈引起.因此沉积正构烷烃氢同位素(δD_(wax))可以作为夏季降水平均氢同位素(δDp)的替代指标,记录夏季风强度和古水文变化.
Hydrogen isotopes of n-paraffin in lakes and marine sediments have been widely used as potential Paleohydrological and palaeoclimate indicators, but they can record changes in isotopic variation of precipitation due to the strong evaporation that strongly affects the n-alkane hydrogen isotope ratio in arid zones Was questioned.In this study, 21 lake sediments were collected in the arid region of the Qinghai-Tibet Plateau (20 of which average annual precipitation was <400 mm), and found that the n-alkanes hydrogen isotope (δD_ (wax)) and the average annual precipitation (R ~ 2 = 0.84, P <0.001), which is more correlated with δD_ (sum) of mean summer precipitation (r ~ 2 = 0.91, P < 0.001), indicating that precipitation is the main factor controlling the δD_ (wax) changes of n-alkanes in lake sediments. Hydrogen isotopes (δD_p) of n-alkanes can still reflect precipitation hydrogen isotope (δD_p) information in arid areas In this study, the average (ε-wax-p) hydrogen isotope fraction between n-alkanes and precipitation in the surface sediments was -113 ‰, which was more positive than that in the wet areas, probably due to strong evaporation in the arid region Therefore, deposition of n-alkane hydrogen isotopes (δD_ (w ax) can be used as a surrogate indicator of mean δDp in summer precipitation, and the summer monsoon intensity and paleo-hydrological changes are recorded.