钦州湾口沉积物中重金属变化特征及其与粒度的关系

Variation Characteristics of Heavy Metals and Their Relationship With Grain Sizes in Qinzhou Bay Mouth,Guangxi

关键词:  晚全新世  重金属  粒度  关系

Key words:  late Holocene  heavy metal  grain size  relationship

摘要:

[目的]开展钦州湾口晚全新世以来沉积物中重金属变化特征及其与粒度关系的研究,为掌握近岸海区重金属分布、迁移、积累规律提供依据。[方法]利用钦州湾口内和湾口外水下斜坡沉积物样品测试数据,着重分析近2.20 m深度即晚全新世以来重要重金属Pb、Cr、Zn的变化特征及其与沉积物粒度的关系,并与其在表层沉积物的积累行为进行比较。[结果]重金属Pb、Cr、Zn具有陆源性,相对含量介于0.0328~0.3630,变异性以Cr最大,Zn最小,在垂向上呈现分段变化;岩芯沉积物颗粒主要分布在1φ~F,主成分为8φ~F,临界粒级为3φ~4φ;在与粒级关系上,Pb、Zn满足粒度控制律,Cr为反粒度控制律,均与其相态有关,同步变化概率P曲线、重金属对粒级变化的响应率k的共轭特征也进一步佐证;Cr具有正响应区间窄、负响应区间宽的特征,而Pb、Zn则相反;在表层沉积物中,Cr与粒度之间的关系已经与Pb、Zn趋向一致,且临界粒级有所右移,表明重金属对细颗粒的选择性增强。[结论]重金属与粒度的关系反映出钦州湾口沉积环境的演变情况;Cr对环境变化敏感,其与粒度的关系具有环境变化示踪意义。

Abstract:

[Objective] The relationship between heavy metals and grain parameters is studied in order to understand the distribution, transportation and accumulation of heavy metals in Guangxi coast waters since late Holocene.[Methods] The distribution variation of heavy metals and their relationship with grain sizes and grain parameters are mainly analyzed, based on the sample test data from surficial and 2.20 m length of core sediments since late Holocene near the mouth of Qinzhou Bay.[Results] The heavy metals in above sediments have land-souring characteristics.The vertical relative concentration of Pb, Cr and Zn is from 0.0328 to 0.3630 in an oscillation way, and the variance of Cr reaches the maximum among above heavy metals.Vertical grain sizes fall into 1φ~F and the primary component is 8φ~F in grain series with 3φ~4φ as critical grain size.Related with chemical phases, Pb and Zn meet grain-controlled law, whereas Cr behaves anti-grain-controlled law, which is further proven by the conjugate of probability P curves and the response k to grain size variation.Cr shows narrow positive response interval and wide negative interval in grain size series, but Pb and Zn oppose to Cr instead.Considering the relationship with grain sizes, Cr has acted almost the same as Pb and Zn in surficial sediments, and the critical grain size moves right to 4φ~5φ, suggesting that the enhancement of selectivity shifts to finer grain sizes.[Conclusion] The relationship between heavy metals and grain sizes in the studied area reflects the environmental change in this area, and Cr is sensitive to environmental change and its relationship with grain sizes owns the significance of environmental change tracer.