基于地球化学特性的海州湾海洋牧场沉积物重金属研究

海洋牧场是一种新的可持续的生产方式,对中国海洋经济的转型具有重要作用.本文根据海底构筑物的密集程度与投放时间把海州湾海洋牧场划分为3个区(外侧区、内测区、中心区),对表层沉积物的温度(T)、酸碱度(p H)、氧化还原电位(Eh)、表面积平均粒径(D3,2])、总有机碳(TOC)这5种地球化学指标进行原位调查,采用改进的BCR方法对重金属Cr、Cu、Ni、Zn、Pb、Cd进行连续提取.结果表明,沉积物Eh的横向分布受到了海底构筑物的影响,TOC在11.7~13.5 g·kg-1之间,与p H呈显著负相关;Cu、Zn、Ni、Cr以原生相为主要赋存形态,Pb、Cd以次生相的铁锰氧化物结合态(F2)为主要赋存形态,并受Eh控制;相关性及聚类分析表明,Cr、Cu、Ni、Zn为天然源,Cd、Pb存在明显的人为来源;Cr、Ni、Cu、Zn、Pb、Cd的可交换及碳酸盐结合态(F1)与TOC显著相关,Cr、Ni、Cu、Zn、Pb、Cd铁锰氧化物结合态(F2)、Cr、Ni、Cu、Zn的残渣态(F4)都与沉积物粒度显著相关,不同形态的Cd受多环境因子控制;海洋牧场中心区和外侧区沉积物中重金属总量、次生相含量均较内侧区和对照区要低.由于海底构筑物和水动力学的差异性,海洋牧场内侧区细颗粒与有机质对沉积物重金属Cr、Ni、Cu、Zn次生相的富集、吸附作用要大于颗粒再悬浮的释放作用,而在中心区、外侧区细颗粒和有机质影响较小;沉积物富集系数显示Cd出现了富集现象.

Heavy Metals in Sediments from the Haizhou Bay Marine Ranching Based on Geochemical Characteristics

Marine ranching is a new sustainable production method, which plays an important role in the transformation of China''s marine economy. In this paper, Haizhou Bay marine ranching was divided into 3 areas according to the intensity and delivery time of the submarine structures. Five geochemical indicators of temperature (T), pH, oxidation-reduction potential (Eh), grain size (D3,2]) and total organic carbon (TOC) were determined on-site. A modified European Community Bureau of Reference(BCR)sequential extraction procedure was applied to determine the chemical speciation of different heavy metals (i.e. Cr, Cu, Ni, Zn, Pb, and Cd). The results showed a horizontal distribution of the Eh was influenced by the submarine structures. The TOC content ranged from 11.7 to 13.5 g·kg^-1, which had a significant negative correlation with pH. Pb and Cd mainly present in the secondary phase of iron manganese oxide forms (F2), which were controlled by the Eh, however, Cu, Zn, Ni, and Cr were mainly present in the primary phase. A correlation and cluster analysis indicated that the Cr, Cu, Ni, and Zn present in sediments were from natural sources, while the Cd and Pb content obviously came from anthropogenic metal sources. The exchangeable and carbonate fractions (F1) of Cr, Ni, Cu, Zn, Pb, and Cd were significantly correlated with TOC. The residuals (F4) of Cr, Ni, Cu, Zn, Pb, Cd were significantly correlated with the grain size of sediments as well as the iron-manganese oxide forms (F2) of Cr, Ni, Cu, and Zn. A different speciation of Cd was controlled by multiple geochemical characteristics of the sediment. The heavy metal levels of the primary and secondary phases in the central and lateral areas were lower than the control and medial areas because of differences in the submarine structures and hydrodynamics. The enrichment and adsorption of Cr, Ni, Cu, and Zn in sediment was stronger than the release of particles that were resuspended. While the influence of fine particles and organic matter from the sediment in the central and outer areas was limited, an enrichment factor analysis suggested that Cd in sediment showed enrichment to some extent. This paper provides a scientific basis for the construction of marine ranching and ecological restoration in Haizhou Bay.