祁连山周边内流区人类活动对表层沉积物的影响

Effects of Human Activities on Surface Sediments in the Endorheic Zone Around the Qilian Mountain

【目的】表层沉积物代用指标可以指示现代环境要素进而推断古环境演化过程,但是在人类活动较强的地区,人类对沉积物产生作用的时间和作用方式以及这种作用是否影响表层沉积物代用指标对该地区气候进行反演的评估较少。【方法】选取祁连山及周边地区所采集的456个表层沉积物,通过总有机氮(TN)、总有机碳(TOC)、碳氮比(C/N)、有机碳同位素(δ^(13)C_(org))、碳酸盐碳同位素(δ^(13)C_(carb))和氧同位素(δ^(18)O)等代用指标分析,建立了代用指标与海拔、经纬度、温度、降水等要素之间的关系,探究了现代人类活动对表层沉积物古环境代用指标的影响。【结果与结论】研究发现人类活动影响区表层沉积物古环境代用指标在该区域波动明显,相较其他地区,相关性大幅降低,表明人类活动影响可以改变古环境代用指标的指示意义。通过系统分析和计算表层沉积物与环境要素之间的关系,探讨了人类活动对表层沉积物的影响,进一步明确代用指标的现代环境指示意义,从而为后续利用沉积地层中古环境代用指标反演过去气候变化和分析人类活动提供理论依据。

[Objective]Surface sediment proxies indicate modern environmental elements and thus infer paleoenvi⁃ronmental evolution,but few assessment have been reported on the effect of intensive human activity on sediments,and whether this affects the indication of the climate of the area by surface sediment proxies.[Methods]In this study,456 surface sediments from the Qilian Mountains and surrounding areas were collected and proxies such as to⁃tal organic nitrogen(TN),total organic carbon(TOC),carbon to nitrogen ratio(C/N),organic carbon isotope(δ^(13)C_(org)),carbonate carbon isotope(δ^(13)C_(carb))and oxygen isotope(δ^(18)O)were analyzed.Relationships between proxies and elevation,latitude,longitude,temperature and precipitation were examined,and the influence of modern hu⁃man activity on the paleoenvironmental proxies of surface sediments was explored.[Results and Conclusions]It was found that these proxies in the anthropogenic zone fluctuate significantly in this region and the correlation is sig⁃nificantly less than in other areas.This suggests that the influence of human activity has changed the indicative mean⁃ing of paleoenvironmental proxies.Systematic analysis and calculation of the relationship between surface sediments and environmental elements explored the influence of human activities on surface sediments,and clarified the use of proxies as modern environmental indicators.This provides a theoretical basis for the use of paleoenvironmental proxies in sedimentary strata to infer past climatic conditions and to analyze human activities.