贵阳污灌区菜地土壤团聚体中有机碳和重金属的含量特征及相关性分析

以贵阳某污灌区菜地土壤为研究对象,分别采用微波消解-电感耦合等离子体质谱(ICP-MS)法和水合热重铬酸钾氧化分光光度法分析不同粒径土壤团聚体中重金属和有机碳的含量特征,并对有机碳和重金属的相关性进行分析。结果表明,以2mm粒径团聚体的含量为最高,约占75%。Cu、Zn、Cd和Pb在0.25～0.5mm粒径团聚体中含量最高,Cr在5～8mm粒径团聚体中含量最高,As在不同粒径团聚体中的含量变化不大,重金属含量随土层深度增大而减小。土壤重金属富集因子表现为CuPbCdZnCrAs,Cu、Zn、Cd和Pb在0.25～0.5mm粒径团聚体中分布因子最高,而在5～8mm粒径团聚体中重金属的质量负载因子最大。土壤有机碳含量随团聚体粒径的增大表现为先增大后减小,不同粒径团聚体中Cu、Cd、Pb和As含量与有机碳含量均呈显著正相关(p0.05)。污灌区菜地土壤Cr、As在5～8mm粒径团聚体中富集现象显著,Cu、Zn、Cd、Pb在0.25～0.5mm粒径团聚体中均表现出显著的富集特征。6种重金属在5～8mm粒径团聚体中的质量负载因子均为最高,表明6种重金属在5～8mm粒径团聚体中的贡献最大。

Content characteristics and correlation of organic carbon and heavy metals in aggregates of wastewater irrigation soil of Guiyang

Organic carbon and heavy metal concentrations in different sizes of soil aggregates in wastewater irrigated vegetable soils of Guiyang were studied. Simultaneous determination of six heavy metals in soil by ICP-MS with microwave digestion. The concentration of organic carbon was measured in soil aggregates with different particle sizes by hydration heat potassium dichromate oxidation colorimetry. The correlation between organic carbon and heavy metals were analyzed in different sizes of soil aggregates in wastewater irrigated vegetable soils. Results showed that >2 mm soil aggregate was largest, being about 75%. The highest contents of heavy metals were distributed in the 0.25-0.5 mm aggregate for Cu, Zn, Cd and Pb, and in the 5-8 mm aggregate for Cr, while there was no difference among the concentration of As in different size aggregates. The content of different heavy metals decreased with increasing of the depth of soil layer. Heavy metal enrichment factors in polluted soil was Cu>Pb>Cd>Zn>Cr>As, the highest distribution factor of heavy metals were showed in the 0.25-0.5 mm aggregate for Cu, Zn, Cd and Pb, and the 5-8 mm particle size aggregates had the largest loading factor of heavy metals. The soil organic carbon content as a whole increased first and then decreased with the aggregate particle size increasing. The contents of Cu, Cd, Pb and As in different particle size aggregates were positively correlated with organic content (p<0.05). The highest significantly enriched of heavy metals were showed in the 5-8 mm aggregate for Cr and As in the wastewater irrigation soil. Cu, Zn, Cd, and Pb show significant enrichment characteristics in the 0.25-0.5 mm particle size aggregates. The six heavy metals have the highest mass load factors in the 5-8 mm particle size aggregates, indicating that the six heavy metals occupy the most contribution in the 5-8 mm particle size aggregates.