用南黄海沉积岩心中氮同位素重建海水营养盐利用率的历史变化

Historical changes of nutrient utilization of seawater reconstructed with nitrogen isotopes in sedimentary cores from the southern Yellow Sea

基于2006年黄东海航次获得的表层沉积物和2009年航次南黄海3个柱状沉积物岩心,分析了表层沉积物总氮(TN)、C/N比值和氮稳定同位素比值(δ^(15)N)的分布特征及南黄海柱状沉积物中这些参数的长期变化规律。结果表明,黄海、东海表层沉积物TN含量、C/N比值和δ^(15)N的变化范围分别为0.023%～0.33%、1.4～50.3和4.0‰～16.0‰。其中,TN与C/N比值存在较显著的负相关性,而TN与δ^(15)N以及C/N比值与δ^(15)N之间无明显的相关性,这反映出黄海和东海陆架边缘海中氮循环的复杂性。对南黄海柱状沉积物的分析结果表明:3个柱状岩心中的TN、C/N比值和δ^(15)N随年代的波动均呈现一定的周期性变化趋势。3个岩心中TN随年代的变化趋势基本一致,100 a来总体呈波动上升趋势,且3个岩心中C/N比值也呈较为类似的变化趋势。柱状沉积物中δ^(15)N的平均变化周期约为24 a左右。由此,重建200 a来南黄海海水中营养盐利用率的历史变化,并初步探讨了其对气候变化的响应。

The distributions of total nitrogen(TN),C/N,and nitrogen stable isotope ratio(δ^15 N)in surface sediments are first studied in the Yellow Sea and East China Sea.The content of TN in surface sediment ranges from 0.023% to 0.33%,while C/N and δ^15 N are about 1.4-50.3 and 4.0‰-16.0‰ respectively.Significant negative correlation exists between TN and C/N,and no correlation is found between TN and δ^15 N or between C/N and δ^15 N.These relationships reflect the complexity of the nitrogen cycles in the Yellow Sea and the East China Sea,both belonging to typical continental shelf marginal sea.Then,three sediment cores collected from the southern Yellow Sea were analyzed for TN,C/N and δ^15 N values.And the long-term change trends of TN,C/N and δ^15 N were subsequently rebuilt combing with 210 Pb chronological study.The results indicate that the long-term changes of TN,C/N and δ^15 N show some periodical trends.The temporal changes of TN show similar change trends in the three sea areas,with generally increasing trends over the past 100 years.And C/N trends also follow relatively similar patterns in the three sediment cores,while the average cycle of δ^15 N is about 24 years.Finally,the historical changes of nutrient usability in the upper water of the southern Yellow Sea over the past 200 years are reconstructed,and their responses to climate change are discussed preliminarily.