三种抗生素对土壤呼吸和硝化作用的影响

Effects of three types of antibiotics on soil respiration and nitrification

抗生素广泛用于人体和动物疾病治疗,但使用后大部分以母体形式排除体外,通过污泥还田、污灌及其他各种途径进入土壤环境,对陆生生态环境产生潜在威胁。为评价抗生素对土壤微生物活性和功能的影响,以3种不同抗生素(磺胺嘧啶、氧四环素和诺氟沙星)为靶标化合物,采用OECD标准土壤呼吸实验和氮硝化实验方法,运用SPSS软件对实验结果进行统计分析,考察抗生素对土壤微生物活性和氮转化功能的影响。实验结果显示:在呼吸实验中,磺胺嘧啶和氧四环素在初始阶段对土壤呼吸具有一定的抑制作用,并且氧四环素的抑制强度低于磺胺嘧啶,其最高抑制率分别为76.8%和20.7%;在实验后期则出现一定激活作用,最高激活率分别为343%和218%,随着时间的推移激活效应减弱。诺氟沙星在呼吸实验初期对微生物活性出现激活作用,最高激活率为15.4%;后期则出现一定的抑制作用,最高抑制率为21.9%。在硝化实验中,磺胺嘧啶对土壤A的微生物硝化作用在各处理之间未出现显著性差异,而对土壤B则具有一定抑制作用,最高抑制率为20%;氧四环素和诺氟沙星则相反,在土壤A中对微生物硝化作用的抑制率分别为50%和19%,这种硝化作用差别性可能是由于土壤pH值和抗生素本身的抗菌谱所引起。通过以上实验结果可得出如下结论:3种不同类型的抗生素对土壤的微生物活性和氮转化功能会产生不同的作用,这种不同主要来自于抗生素种类、土壤类型及抗生素的浓度等因素的影响。因此,土壤中抗生素的引入将可对陆生生态环境造成一定影响,在实际粪便还田过程中应开展风险评估。

Antibiotics are widely administrated in human and livestock to treat diseases and most of them were excreted as mother molecules. Subsequently, antibiotic residues can enter into environment through the route of biosolid application in field, wastewater irrigation and others, which might pose a potential threaten to terrestrial eco-environment. For assessing the role of different types of antibiotics in influencing soil microbial activity and function, this paper investigated the effects of antibiotics on soil respiration and nitrification using sulfadiazine, oxytetracycline and norfloxacin as target chemicals and OECD standard method. In the respiration experiments, both sulfadiazine and oxytetracycline inhibited soil microbial respiration at the early stage of experiments, but the inhibiting rate for sulfadiazine was stronger than oxtetracycline. The highest inhibiting rates for sulfadiazine and oxytetracycline were 76.8%and 20.7%. The stimulation effects of sulfadiazine and oxytetracycline were found at the later stage of soil respiration experiments and the highest activating rates were 343%and 218%, respectively. However, the stimulation effects became weaker as time elapse. At the early stage of experiment, norfloxacin stimulated the micriobial respiration with the highest rate of 15.4%and the highest inhibiting rate of 21.9%was found at the later stage of experiment. In the nitrification experiments, sulfadiazine inhibited microbial nitrification for soil B a, not for soil A. The strongest inhibition rate was 20%for sulfadiazine in soil B. On the contrary, the inhibition effect of nitrification was found for oxytetracycline and norfloxacin in soil A and the inhibiting rates were 50%and 19%, respectively. The difference in effects of antibiotics on nitrification is contributed to soil pH and antibacterial spectrum of antibiotics. In conclusion, the results of soil microbial activity and nitro-transformation function is different for three types of antibiotics, which rise from antibiotics types, soil types and antibiotics concentration. Therefore, the risk should be assessed when antibiotics enter into terrestrial environment as manure form.