摘要
在210Pb定年的基础上,分析了长江口外东南泥质区柱样沉积物稀土元素含量、特征参数分布特征及其与粒径、常量元素等的相关性,探讨了150 a以来稀土元素的来源、制约因素及对沉积环境的响应。结果表明,柱样稀土元素总量(ΣREE)变化范围不大,分布范围为158.38～197.87μg/g,平均值为183.49μg/g,总体趋势由下向上逐渐增加;轻、重稀土元素比值(ΣLREE/ΣHREE)无明显的变化趋势,平均值为7.90;各层位球粒陨石标准化REE分布模式几乎完全一致,具有负斜率、Ce弱负异常、Eu明显负异常、轻稀土元素相对重稀土元素富集的河流沉积物特征,表明百年来沉积物REE主要来源于长江流域风化产物且基本继承了源区的组成特征。REE与Ti、Al、Fe呈负相关关系,与粒度相关性不明显,重矿物对沉积物REE组成和分布模式有重要影响,生物碎屑沉积对REE含量有一定的稀释作用。δCe值在0.94～1.01之间,百年来呈递减趋势,平均值为0.96,呈微弱负异常;δEu在0.67～0.69之间,百年来基本不变且具明显的负异常,平均值为0.69。百年来δCe递减可能与沉积物所在的长江口高生产力区持续增强的缺氧现象有关。
One drillcore collected from the Changjiang Estuary mud area was selected for this study. The grain size,rare earth elements （REE） and major elements were determined on the 210Pb-dated sediment core. The sediment REE provenance, main controlling factors and the responding to the sedimentary environment over the last 150 years were discussed. The total content of rare earth element （ΣREE） varies between 158.38 μg/g and 197.87 μg/g,in average of 183.49 μg/g, increasing upwards along the core. The ΣLREE/ΣHREE ratio remains relatively constant with an average of 7.90. Chondrite-normalized REE distribution patterns of samples from different depth remain the same and show riverine sediment characteristics, i.e. negative slope, the enrichment of LREE and weak depletion of HREE. The results indicate that the REE of core sediment mainly came from weathered materials of the Changjiang River and conserved the REE patterns of provenance. REE negatively correlates with Ti, Al, Fe without obvious correlation with grain sizes. Heavy minerals exert important influence on REE composition. The biogenic sedimentary matter might dilute the REE concentration of the sediment. δCe ranges between 0.94 and 1.01, decreasing slightly upwards, with an average of 0.96, showing weak negative Ce anomaly. δEu is fairly constant with obvious negative Eu anomaly, varying between 0.67 and 0.69, with an average of 0.69. The decreasing trend of δCe distribution over the last 150 years may be related to the progressive hypoxia and high productivity in the Changjiang Estuary.
出处
《地球化学》
CAS
CSCD
北大核心
2011年第5期464-472,共9页
Geochimica
基金
国家自然科学基金(41076036)
"我国近海海洋综合调查与评价"专项(908-02-02-05)
浙江省自然科学基金(Y506287,Y5110171)
关键词
稀土元素
沉积柱样
长江口
rare earth elements(REE)
sediment core
Changjiang Estuary
