四环素类抗生素对土壤-生菜系统的生物效应及其迁移降解特性

四环素类抗生素（TCs）会随畜禽粪便的施用而残留在农田土壤，对蔬菜生长和土壤生态带来风险.本文通过温室土壤盆栽试验，外源添加3种不同水平的土霉素（OTC）、四环素（TC）和金霉素（CTC），研究了TCs对生菜的生理毒性和在生菜中的吸收转运特性，同时研究了TCs在土壤中的降解和对土壤酶活性以及土壤微生物数量的影响.结果表明，OTC、TC和CTC降低了生菜的生物量，减少了叶绿素a、叶绿素b和类胡萝卜素的含量，抑制了净光合速率，提高了SOD、POD和CAT活性；生菜对TCs的吸收量根系>地上部分，随土壤施加的TCs增加吸收量增加，而生物富集系数和转运系数降低；通过人体预测每日摄入量（EDI）和人体每日允许摄入量（ADI）的比值计算TCs暴露引起的人体健康潜在风险值（HQ），当土壤中OTC、TC和CTC含量低于150 mg·kg^-1时，生菜可食部位的健康风险较低（HQ<0.1）；TCs在不同土壤中的降解速率：对照土 > 根际土 > 非根际土，OTC在土壤中的降解速率显著低于TC和CTC；高含量的TCs（150~1350 mg·kg^-1）处理显著抑制土壤脲酶和根际土的过氧化氢酶活性，减少土壤细菌和真菌的数量.

Biological Effect of Tetracycline Antibiotics on a Soil-Lettuce System and Its Migration Degradation Characteristics

Residual tetracycline antibiotics (TCs) in farmland soils with the application of livestock manure cause risks to the growth of vegetables and soil ecology. Here, pot experiments are carried out using through exogenous addition of different levels of oxytetracycline (OTC), tetracycline (TC), and chlortetracycline (CTC), to study the physiological toxicity, uptake, and transportation of TCs in lettuce. The subsequent degradation of TCs in soil was also evaluated along with analyses of soil enzyme activity and microbial population dynamics. The results showed that the biomass of lettuce decreased with application of TCs as well as the chlorophyll-a, chlorophyll-b, and carotenoid content. Consequently, net photosynthetic rates were inhibited, and SOD, POD, and CAT increased under the stress imposed by the TCs. With an increase in the level of TC application, uptake by lettuce plants increased while the bioconcentration and translocation factors decreased. When OTC, TC, and CTC in the soil were below 150 mg·kg^-1, the health risk from the edible parts of lettuce was low (HQ<0.1). The TC degradation rate in different soils was ranked in the order of control soil > rhizosphere soil > bulk soil. The OTC degradation rates in the soils were significantly lower than for TC and CTC. TCs (150-1350 mg·kg^-1) significantly inhibited urease and rhizosphere catalase activity in soil and reduced the number of soil culturable bacteria and fungi.