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汞是一种危害和毒性极强的重金属元素,自20世纪50年代日本水俣病事件以来,汞污染事件就被全球所重视。汞在自然界环境中的存在有多种形态,不同形态之间特征有较明显的差异,且不同形态之间可以进行转化。自然水体中把汞形态分为活性汞(RHg)、溶解性气态汞(DGM)、甲基汞(MeHg)和二甲基汞等[1]。DGM是水体中汞的一种主要形态,虽然其毒性不是最强,但影响也不容小觑。DGM的主要存在形式是零价态汞,在水中的质量浓度一般低于0.2 ng·L−1[2]。区别于其他重金属,汞在常温下可以以气态形式挥发,因此零价态汞在全球汞的循环中占有重要的作用。水体及陆地表面的零价汞可以挥发进入到大气中,且在大气中停留时间较长,从而进行长距离迁移,最终通过干沉降或湿沉降进入水生环境和陆地环境。在人为活动较少的南极、北极以及中国青藏高原地区,也都监测到较高浓度的汞[1]。这说明汞的污染是全球性的,而零价态汞的生成又异常重要。抗生素滥用已经成为中国环境主要问题之一。土霉素(OTC)是四环素家族的一员,也是兽医和水产养殖中使用的广谱抗生素之一。由于抗生素耐药性在微生物中的传播,引起了越来越多的关注。它被广泛地用作养殖鱼的饲料添加剂和家畜的生长刺激物质,也可用于植物细菌性疾病的预防性治疗。在欧洲,超过2 500 t四环素类作为兽药治疗,其中以土霉素应用最广泛[3]。中国在2003年时土霉素产量已经达10 000 t,占世界总产量的65%[4]。然而,它很难在动物体内被代谢,这导致土霉素会随粪便或尿液排出体外。由于其水溶性和耐降解性,土霉素已在土壤环境、沿海环境甚至饮用水中被广泛检测到。在水体、底泥以及污泥硝化过程中,重金属会和抗生素发生络合反应,或促进或抑制抗生素的降解。同时,金属与抗生素之间的络合对金属的价态也会产生一定影响。由于汞的特殊性,抗生素与汞之间的络合反应有可能会对汞形态变化产生影响。但是,目前关于抗生素与汞的络合反应还鲜有报道。鉴于此,本研究采用实验室模拟水生环境,配制汞和抗生素的混合反应溶液,研究不同环境因子对抗生素与汞络合条件下DGM产生的影响,以期为解决抗生素与汞复合污染提供理论依据。
Effects of different factors on dissolved gaseous mercury in the complexation reaction of antibiotics with mercury
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摘要:
目的 研究不同环境因子下土霉素(OTC)与汞(Hg)络合后溶解性气态汞(DGM)的变化特征,可了解抗生素与汞的复合污染问题。 方法 利用实验室模拟实验,以OTC(1 μmol·L−1)和氯化汞(HgCl2 1 μmol·L−1)溶液为材料,以pH、光照、盐度和氧化还原为不同影响条件,探究反应后DGM的变化特征。 结果 不同环境因子对水体DGM的影响起主要作用,DGM随pH的增加呈减少趋势,酸性条件下的DGM显著高于碱性条件。光照条件下DGM略高于黑暗条件。淡水条件中的DGM显著高于海水条件。厌氧条件下的DGM在试验初期低于好氧条件,在第10天之后高于好氧条件。 结论 OTC与汞会发生络合反应,且络合反应有利于DGM的形成。不同环境因子也会影响两者络合后产生的DGM。OTC与Hg络合后反应生成的DGM要高于对照组,但OTC的影响程度低于本身环境因子的影响。图3参27 Abstract:Objective To better understand the combined pollution of antibiotics and mercury, an investigation is conducted of the influence of different environmental factors on the dissolved gases mercury (DGM) formed in the liquid phase after the complexion reaction of oxytetracycline (OTC) with mercury. Method With OTC solution (1 μmol·L−1) and mercury chloride (HgCl2 1 μmol·L−1) selected as materials, simulation experiments were conducted in the laboratory with pH, light, salinity, and redox employed as the environmental factors to explore the changing characteristics of DGM concentration after the reaction. Result Environmental factors have significant impact on the formation of DGM. There is a significant decrease in DGM concentration with the increase of pH. The DGM concentration in the condition of light irradiation was slightly higher than that in the dark condition. The DGM concentration in sea water was significantly higher than that in freshwater. The DGM concentration in anaerobic condition was slightly lower than that in aerobic condition but the situation was reversed after ten days. Conclusion The complexation reaction of OTC with mercury occurs and is beneficial to the formation of DGM which is subject to the impact of different environmental factors. The DGM formed by the reaction of OTC and Hg is higher than that in the control group. However, the influence of OTC on the formation of DGM is not as strong as the environmental factors. [Ch, 3 fig. 27 ref.] -
Key words:
- environmental chemistry /
- dissolved gases mercury(DGM) /
- antibiotic /
- pH /
- light /
- salinity /
- redox
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https://zlxb.zafu.edu.cn/article/doi/10.11833/j.issn.2095-0756.20190568