CAJ | 학술논문

兹格塘错是青藏高原中部一个典型的半混合型咸水湖泊.本文在~(210)Pb和~(137)Cs定年的基础上,研究了兹格塘错重力岩芯(ZGTC A-1)小于38.5 μm细颗粒组分碳酸盐稳定碳同位素1950年以来的变化及其影响因素.对冬夏季湖水水化学特征的分析表明,夏季湖水溶解CO_2呈逸出状态,冬季湖水钙离子浓度是夏季湖水的10倍,据此可以得出兹格塘错碳酸盐矿物主要在夏季沉淀.通过与那曲气象站气象记录对比发现,1950年以来A-1岩芯碳酸盐碳同位素变化与年均温度有很好的相关性,表现出年均温度高时碳同位素偏重,而年均温度低时碳同位素偏轻的特征.兹格塘错1950年以来自生碳酸盐碳同位素的变化是由湖区及水体碳循环(如碳酸盐沉淀,有机质的沉淀与分解,有机碳和无机碳的转化等)的变化引起的,但各种因素的相互作用非常复杂.碳酸盐含量也与温度有关,温度越高,碳酸盐含量越高,同时降水量与碳酸盐含量也存在明显的相关关系.1950年以来有机质含量与温度呈反相关,可能与湖泊生产力的下降有关.
자격당착시청장고원중부일개전형적반혼합형함수호박.본문재~(210)Pb화~(137)Cs정년적기출상,연구료자격당착중력암심(ZGTC A-1)소우38.5 μm세과립조분탄산염은정탄동위소1950년이래적변화급기영향인소.대동하계호수수화학특정적분석표명,하계호수용해CO_2정일출상태,동계호수개리자농도시하계호수적10배,거차가이득출자격당착탄산염광물주요재하계침정.통과여나곡기상참기상기록대비발현,1950년이래A-1암심탄산염탄동위소변화여년균온도유흔호적상관성,표현출년균온도고시탄동위소편중,이년균온도저시탄동위소편경적특정.자격당착1950년이래자생탄산염탄동위소적변화시유호구급수체탄순배(여탄산염침정,유궤질적침정여분해,유궤탄화무궤탄적전화등)적변화인기적,단각충인소적상호작용비상복잡.탄산염함량야여온도유관,온도월고,탄산염함량월고,동시강수량여탄산염함량야존재명현적상관관계.1950년이래유궤질함량여온도정반상관,가능여호박생산력적하강유관.
Zigetang Co,located on the central Tibetan Plateau,is a meromictic saline lake.A 96-cm-long core(ZGTC A-1)was taken from Zigetan8 Co(the water depth 25m)in summer 2006.The age of the upper 9.25cm(since 1890AD)of the core was got through CIC model of ~(210)Pb.The δ~(13)C during the past 60 years had good correlation with the average temperature in Naqu Station,which indicated that it was mainly controlled by average temperature in a year.When the annual mean temperature was higher,the δ~(13)C value in the sediment became heavier and vice versa.In Zigetang Co,the main factor controlling the δ~(13)C was the CO_2 exchange between lake water and atmosphere.Seasonal variation of Ca~(2+) and dissolved inorganic carbon(DIC)indicated that the calcium carbonate(mainly composed of calcite and aragonite)mainly precipitated in summer.The dissolved CO_2 in the lake water escaped into the atmosphere due to the relatively high temperature in summer.When the average temperature in a year was higher,the escape of CO_2 into the atmosphere became larger due to the shorter frozen time on the lake surface in winter and higher water temperature in summer,which induced the δ~(13)C of the dissolved inorganic carbon in the lake water was more positive,so do the δ~(13)C in carbonates.