入侵植物凋落物浸提液对紫色土吸附金霉素的影响

用3种入侵植物的地上(O)和地下(U)凋落物浸提液(Le)对紫色土进行修饰,采用批处理法研究各Le修饰土样对金霉素(CTC)的等温吸附特征,分析pH值、离子强度和温度对CTC吸附的影响。结果表明：各Le修饰紫色土对CTC的吸附等温线最适用于Freundlich模型描述;当pH值为2,离子强度为0.1 mol/L和试验温度40 ℃时,一年蓬(Conyzaannumus)Le修饰紫色土对CTC的吸附效果最佳,最大吸附量为1.68 mmol/kg~7.94 mmol/kg;当Le修饰比例为100%时,OLe和ULe修饰紫色土对CTC的吸附量均达到最大,且OLe修饰紫色土对CTC的吸附效果相比ULe更佳。     

Transformation kinetics and pathways of tetracycline antibiotics with manganese oxide

Tetracycline antibiotics including tetracycline (TTC), oxytetracycline (OTC) and chlorotetracycline (CTC) undergo rapid transformation to yield various products in the presence of MnO₂ at mild conditions (pH 4-9 and 22 °C). Reaction rates follow the trend of CTC > TTC > OTC, and are affected by pH and complexation of TCs with Mg²⁺ or Ca²⁺. Experimental results of TTC indicate that MnO₂ promotes isomerization at the C ring to form iso-TTC and oxidizes the phenolic-diketone and tricarbonylamide groups, leading to insertion of up to 2 O most likely at the C9 and C2 positions. In contrast, reactions of OTC with MnO₂ generate little iso-OTC, but occur mainly at the A ring’s dimethylamine group to yield N-demethylated products. CTC yields the most complicated products upon reactions with MnO₂, encompassing transformation patterns observed with both TTC and OTC. The identified product structures suggest lower antibacterial activity than that of the parent tetracyclines.