地下水中两种典型抗生素复合对反硝化作用的影响

选取氟喹诺酮类抗生素中的环丙沙星（CIP）与洛美沙星（LOM）作为典型抗生素代表，选择乙酸钠为碳源，采用批实验方法开展室内模拟试验，探究了CIP与LOM在单独作用和联合作用下对反硝化进程的影响.在此基础上，通过测定反硝化菌数量、活性和反硝化酶活性等指标变化探究其影响机理.实验结果表明，与空白组体系相比，LOM （100μg/L）组、CIP （100μg/L）组和LOM （50μg/L）+CIP （50μg/L）组对NO₃^--N降解和NO₂^--N降解均产生抑制作用，抑制率：LOM+CIP>CIP>LOM，抗生素暴露会不同程度抑制微生物数量活性及反硝化关键酶活性.NO₃^--N降解受反硝化菌活性以及硝酸盐降解酶（NaR）活性的共同影响，NO₂^--N降解则主要受到亚硝酸盐还原酶（NiR）活性的影响.对抗生素联用效果的探究表明，LOM+CIP组在NO₃^--N降解与NO₂^--N降解环节的抑制率均大于单一用药组，表现为LOM与CIP在上述两阶段的协同抑制作用；联合组对反硝化关键酶活性同样表现出两种典型抗生素的协同抑制；而联合组对微生物数量与活性的抑制则表现出两种抗生素的拮抗作用.不同抗生素对反硝化的主要作用环节不同，LOM体系主要作用于NO₃^--N降解环节，而CIP体系对NO₃^--N降解与NO₂^--N降解环节的抑制率相差无几，LOM+CIP体系对上述两环节的抑制率同样无明显差异.

Effects of the combination of two typical antibiotics on denitrification process in groundwater

Ciprofloxacin (CIP) and lomefloxacin (LOM) were selected as typical fluoroquinolone antibiotics, sodium acetate was used as the carbon source, and batch experiments were carried out to explore the effects of CIP or/and LOM on denitrification process. Then the influencing mechanisms were investigated by measuring the changes of indicators, such as the number and activity of denitrifying bacteria and the denitrifying enzyme activity. The results showed that compared with the blank system, LOM (100μg/L) group, CIP (100μg/L) group and LOM (50μg/L)+CIP(50μg/L) group had inhibitory effects on degradation both NO₃^--N and NO₂^--N. The inhibition rates followed an order of LOM + CIP > CIP > LOM. Antibiotic exposure could inhibit the quantity and activity of microorganisms and the activity of key denitrifying enzymes to varying degrees. The NO₃^--N degradation was affected by the activity of denitrifying bacteria and the activity of nitrate reductase (NaR), while the NO₂^--N degradation was mainly affected by the activity of nitrite reductase (NiR). The results of the combined effects of antibiotics showed that the inhibition rates of LOM + CIP group in NO₃^--N and NO₂^--N degradation stages were greater than those of single-antibiotic groups, indicating the synergistic inhibition of LOM and CIP; the synergistic inhibition of two typical antibiotics on the activities of key denitrifying enzymes was also observed; however, the inhibition of the combined antibiotics group on the quantity and activity of microorganisms indicated the antagonistic effects. The effects of different antibiotics on denitrification effects were different. LOM mainly affected on the NO₃^--N degradation stage, while the CIP or LOM+CIP showed similar inhibition effects on both stages of NO₃^--N degradation and NO₂^--N degradation.