广州市南沙区第四系剖面镉富集特征及生物有效性

了解土壤重金属镉的分布格局及富集规律，掌握其活性及影响因素，对保障农用地和建设用地土壤环境安全，改善土壤环境质量至关重要.测试南沙区第四系剖面重金属Cd含量，采用地质累积指数(I_geo)和潜在生态风险指数法（E_r）对污染水平进行评价，采用因子分析（FA-MLR）方法，确定镉元素全量及各形态与土壤理化性质的相关性.结果表明，土壤pH值的差异导致镉含量随深度呈现不同的变化趋势，酸性环境中深层土壤镉的迁移量及纵向迁移深度更大；第四系沉积物镉含量随深度的变化趋势呈双峰分布，镉含量分别在20～25 m和5～10 m达到峰值，该段岩心沉积物多为海相沉积物的淤泥和淤泥质黏土，阳离子交换量及有机质均较高；以黏性土为主的细粒级沉积物中镉元素I_geo和E_r明显高于以砂性土为主的粗粒级沉积物；pH变化对镉迁移转化的影响不完全体现在对镉全量的影响上，更重要的是改变了镉的有效态，从而影响了镉的生物有效性；由水溶态、离子交换态和碳酸盐态组成的不稳定镉约占总镉的37.92%～49.10%,土壤镉有较强的不稳定性.今后需要进一步研...

Cadmium Enrichment and Bioavailability of Quaternary Profiles in Nansha District, Guangzhou, China

Comprehending the distribution pattern and enrichment rule of the heavy metal cadmium (Cd) in soil and grasping its activity and influencing factors is crucial for guaranteeing the soil environment safety of agricultural and construction land and improving the overall quality of the soil environment. The concentration of heavy metal Cd in the quaternary profile of Nansha was measured, and the pollution level was evaluated using the geographical accumulation index (I_geo) and potential ecological risk index (E_r). Then, we determined the correlation between the total amount of Cd and the physicochemical properties of the soil using factor analysis (FA-MLR). The results showed that the average content of Cd in shallow soil (0-20 cm) in the Nansha area was 0.54 mg·kg^-1, and the soil was mainly weakly acidic and neutral. The average content of Cd in deep soil (150-200 cm) was 0.42 mg·kg^-1, and the soil was mainly neutral. At the same time, the variation coefficient of Cd content in shallow soil was significantly greater than that in deep soil, and Cd content tended to be consistent with the increase in depth. The Cd content of quaternary sediments showed a bimodal distribution with depth, reaching a peak at 20-25 m and 5-10 m, respectively, whereas the core sediments in this section were mostly marine sediments of silt and silty clay, with high cation exchange capacity and organic matter. The I_geo and E_r of Cd in the fine-grained sediments dominated by clayey soil were significantly higher than those in the coarse-grained sediments dominated by sandy soil. The difference in soil pH value led to the different trend of Cd content with depth; the migration amount and vertical migration depth of Cd in deep soil were greater in the acidic environment. The influence of pH change on the migration and transformation of Cd was not completely reflected in the influence on the total amount of Cd, but more importantly, it changed the effective state of Cd, thus affecting the bioavailability of Cd. The unstable Cd composed of water-soluble, ion-exchangeable, and carbonate states accounted for 37.92%-49.10% of the total Cd, resulting in a strong instability of soil Cd. Further investigation on the migration and toxicity of heavy metals associated with human health risks is needed in future studies.