This study investigated the total concentrations and geochemical compositions of metals (Cd, Cr, Cu, Ni, Pb, Zn, Fe and Mn) in surface sediments of Zhanjiang Bay (ZJB) in spring and summer, to assess the contamination status, mobility and influencing factors of spatial-seasonal changes of these metals. The average total concentration for each studied metal in the surface sediments of ZJB was 0.173 μg/g for Cd, 58.25 μg/g for Cr, 17.11 μg/g for Cu, 16.89 μg/g for Ni, 28.70 μg/g for Pb, 67.91 μg/g for Zn, 30.18 mg/g for Fe, and 275.5 μg/g for Mn during the investigation period. Generally higher total concentrations of metals were found in the channel and coastal sediments of ZJB compared with those in the central ZJB, which may be probably resulted by the input of Suixi river, domestic sewage and industrial wastewater. The grain size compositions and TOC contents also had influences on the distributions of metals in ZJB. In the channel, total metals and reducible and bioavailable fractions of metals generally showed decreased concentrations in summer compared with those in spring, suggesting the release of metals from sediments. Organic matter degradation and Fe and Mn (hydr)oxides reduction processes may contribute much to this phenomenon. Relatively high proportions of Cd and Zn (average of 21.7% and 14.6%, respectively) were associated with the acid soluble fraction, indicating their high risk to the environment. The combined assessment results of enrichment factor, contaminated factor and the percentages of acid soluble fraction indicated that Cd and Zn in the surface sediments of ZJB were generally contaminated and they had medium to high risk to the environment. The average values of pollution load index in the channel, coastal and central ZJB were 1.28, 0.93 and 0.81, respectively, indicating the deterioration of surface sediments in the channel of ZJB. More attention should be paid on the metals in surface sediments of the channel of ZJB.

本研究调查了春季和夏季湛江湾（ZJB）表层沉积物中金属（Cd、Cr、Cu、Ni、Pb、Zn、Fe和Mn）的总浓度和地球化学成分，以评估污染状况、流动性和这些金属的时空变化的影响因素。ZJB表层沉积物中每种研究金属的平均总浓度为Cd为0.173 μg/g，Cr为58.25 μg/g，Cu为17.11 μg/g，Ni为16.89 μg/g，Pb为28.70 μg/g，在调查期间，Zn 为 67.91 μg/g，Fe 为 30.18 mg/g，Mn 为 275.5 μg/g。与中部相比，浙江省河道和海岸沉积物中的金属总浓度普遍较高，这可能与遂溪河、生活污水和工业废水的输入有关。晶粒尺寸组成和 TOC 含量也对 ZJB 中金属的分布有影响。在河道中，总金属和金属的可还原和生物可利用部分在夏季的浓度普遍低于春季，这表明金属从沉积物中释放出来。有机物降解和铁和锰（氢）氧化物的还原过程可能对这种现象有很大贡献。相对较高比例的 Cd 和 Zn（平均分别为 21.7% 和 14.6%）与酸溶性部分相关，表明它们对环境的高风险。富集因子综合评价结果，污染因子和酸溶组分的百分比表明，ZJB表层沉积物中的Cd和Zn普遍受到污染，对环境具有中到高风险。河道、沿海和中部污染负荷指数平均值分别为1.28、0.93和0.81，表明河道表层沉积物恶化。ZJB河道表层沉积物中的金属应引起更多关注。