关键词: 绿肥, 根系互作, 土壤有机碳, 土壤团聚体, 紫色土

Abstract: Metal oxides (such as manganese oxides) have received great concerns, due to its reactive surfaces which could affect the fate of fluoroquinolone antibiotics (FQs) in soil. In this study, batch and column experiments were conducted to investigate the effects of manganese oxides coated sand (MOCS, mimicking soil metal oxides) on transport of target compound ciprofloxacin (CIP, a widely prescribed fluoroquinolone). Batch experiments were carried out using Freundlich model to quantify the adsorption of CIP on manganese oxides. Column experiments were conducted at three levels of manganese oxides in sand (0, 55 and 109 μg Mn·g^-1 sand) to explore the effects of manganese oxides on CIP transport. Results showed that the K_F values were 1.63fold higher on MOCS than on sand, indicating that CIP had higher affinity in adsorption MOCS, due to the microporous structure of manganese oxides. It resulted in manganese oxides reducing the transport of CIP, as the content of manganese oxides increased from 0 to 109 μg Mn·g^-1 sand and C/C₀ decreased from 0.96 to 0.72. These were consistent with the twosite kinetic estimated parameters of k_att1 values, k_att2 values and S_max1 values, which with 109 μg Mn·g^-1 sand column were 2.04-2.33 and 4.21-12.69 times higher than the corresponding values with 55 μg Mn·g^-1 sand column and 0 μg Mn·g^-1 sand column, respectively. After eluting with a low surface tension solution (20% v/v ethanol in background solution), the total recovery rates reached up to 95%, illustrating that the adsorption of CIP on manganese oxides was reversible. Based on the transport behavior of CIP, our results showed that manganese oxides had higher affinity in adsorption cationic microorganic pollutants, which reduced the transport of cationic microorganic pollutants.

Key words: green manure, purple soil, soil organic carbon, root interaction, soil aggregate