热带地理 ›› 2017, Vol. 37 ›› Issue (1): 82-90.doi: 10.13284/j.cnki.rddl.002913

• 论文 • 上一篇    下一篇

海南东寨港红树林沉积物中稀土元素分布特征及其制约因素

王鸿平,季一诺,伏箫诺,赵志忠   

  1. (海南师范大学 地理与环境科学学院,海口 571158)
  • 出版日期:2017-01-05 发布日期:2017-01-05

Distribution and Restriction Factors of Rare Earth Elements in the Sediments from the Mangrove in Dongzhai Harbor,Hainan Island

WANG Hongping,JI Yinuo,FU Xiaonuo,ZHAO Zhizhong   

  1. (School of Geography and Environmental Science,Hainan Normal University,Haikou 571185,China)
  • Online:2017-01-05 Published:2017-01-05

摘要: 红树林湿地是海陆交汇带内的一个特殊生态系统,其沉积物中各种元素的地球化学特征受多种因素制约。对海南岛东寨港红树林湿地沉积物中的65个样品进行稀土元素(REE)分析,结果表明:东寨港红树林湿地沉积物中稀土元素总量(∑REE)变化范围为141.28~269.20 mg/kg,平均值为221.88 mg/kg,明显高于中国土壤(163.86 mg/kg)和中国浅海沉积物(159.53 mg/kg)中稀土元素的总量,与海南砂页岩母质(216.88 mg/kg)稀土元素总量接近。沉积物REE质量分数显示出轻稀土明显富集、重稀土亏损的特征,∑LREE/∑HREE为12.87,铕(Eu)呈明显负异常(0.58)以及铈(Ce)呈中等程度正异常(1.98)等陆源沉积物特征。不同类型湿地的∑REE表现为:林内>林缘>光滩,随着离岸距离的增加,稀土元素质量分数逐渐降低;∑REE与粒度之间没有明显的相关性,稀土元素的分布主要受化学风化的影响。

关键词: 红树林沉积物, 稀土元素, 东寨港

Abstract: The rare earth elements (REE) of 65 samples have been analyzed, which were taken from mangrove wetland sediments in Dongzhai Harbor, Hainan Island. The results showed that the total amount of ΣREE ranged from 141.28~269.20 mg/kg, with an average value of 221.88 mg/kg. We found that the lowest value appeared in the S1 region, and the highest value in the S3 region. The mean values of ∑REE in S2, S3 and S5 were all higher than that of the whole study area, but the mean values of ∑REE in S1, S4 and S6 were lower than that of the whole study area. The distribution regularity was as follows: S3 >S5 >S2 >S4 >S6 >S1. In general, in the study area, the mean value of the LREE was 205.88 mg/kg, which was relatively enriched, accounting for 93% of the ∑REE content. The mean value of HREE was 16.00 mg/kg, accounting for 7% of the REE content, which was significantly lower than that of LREE, showing that LREE was the major contribution of ∑REE. The chondrite-normalized pattern of rare earth elements in the sediments of the study area showed that LREE was rich and HREE had relatively loss. LREE/HREE varied from 7.96 to 15.20, with an average value of 12.87, and the (La/Yb)CN varied from 7.99 to 13.11, with an average value of 10.12, fractionation between light and heavy REEs was obvious, indicating that REE in the sediments obviously had a differentiation and the main material sources of sediments were of matter coming from the mainland, as compared to the chondrite-normalized pattern . In addition, δEu ranged from 0.44 to 0.77, with an average of 0.58, showing an obviously negative anomaly. The distribution regularity was: barren shoal (0.56) > edge of forest (0.59)> inside of forest (0.65); but it showed a moderate positive Ce anomalies, δCe ranged from 1.48 to 2.46, with an average of 1.98. The sediments of different wetland showed that: inside of forest (225.38 mg/kg) >edge of forest (218.23 mg/kg)>barren shoal (212.91 mg/kg), ∑REE decreased gradually with the increase of the distance from the shore. The correlation showed that for the barren shoal R2=0.168, the edge forest R2=0.246 and inside of forest R2=0.295. There was no obvious correlation between ΣREE and grain size, the distribution of ΣREE was not controlled by grain size in the study area. As the forest, forest edge and barren shoal were in the same study area with the same material source, the material sources didn’t have influences on the REE differentiation among them. Regional chemical weathering, the scouring effect of seawater and the salinity of ocean waters resulted in the difference of REE composition among barren shoal, forest edge and inside of forest.

Key words: mangrove sediment, rare earth element, the Dongzhai Harbor