鄱阳湖三角帆蚌软组织中稀土元素累积与沉积物金属形态响应研究
Distribution of Rare Earth Elementsin the Soft Tissue of Hyriopsis cumingii and the Correlation with Metal Speciation of Sediments in Poyang Lake

摘要 为了研究稀土元素对水生态安全的影响, 于2014年秋季对鄱阳湖5个代表性监测点的三角帆蚌及沉积物进行样品采集, 分析三角帆蚌软组织及沉积物不同提取形态稀土元素的含量。结果表明, 三角帆蚌软组织中稀土元素总量均值为15.52 mg/kg, 轻稀土元素更易累积, 表明轻稀土元素对贝类的生物效应强于重稀土元素。沉积物样品中稀土元素总量均值为285.22 mg/kg, 含量高于中国土壤平均值; 轻稀土元素明显富集, 重稀土元素相对亏损, 呈现较强的陆源属性。各监测点沉积物中稀土元素4种赋存形态的平均含量: 残渣态>可还原态>可氧化态>酸可提取态, 酸可提取态含量最低, 且空间分布差异较大, 风险评估表明其均处于无风险或低风险水平。三角帆蚌软组织中大部分稀土元素与沉积物中可氧化态和全量显著正相关, 表明三角帆蚌对沉积物中稀土元素的生物可利用性以可氧化态为主。
Abstract Hyriopsis cumingii and corresponding sediment in five respective monitoring sections of Poyang Lake were sampled in autumn 2014, followed by the detection of rare earth elements (REEs) in the soft tissue of Hyriopsis cumingii and sediments treated by BCR sequential exaction. As results, the mean value of total REEs in the soft tissue of Hyriopsis cumingii was 15.52 mg/kg, and light REEs were more easily accumulated, indicating that the biological effect of light REEs on Hyriopsis cumingii was stronger than heavy REEs. Correspondingly, the mean value of total REEs in sediments was 285.22 mg/kg with higher light REEs, suggesting the strong terrigenous properties. The REEs concentration in the sediment treated by BCR sequential extraction ranked as: residual fraction>reducible fraction>oxidizable fraction>exchangeable fraction. The exchangeable fraction displayed the lowest REEs concentration but the largest difference in spatial distribution; however, they were all under low risk level analyzed by Risk Assessment Code. Significant and positive correlations can be observed between REEs in Hyriopsis cumingii and that in the oxidizable fraction of sediments, suggesting that the bioavailability of REEs would mainly depend on REEs bound to organic matter.