离子强度和离子类型对土霉素在草甸土中被吸附的影响

土霉素是四环素类抗生素中使用较为广泛的一种,探索土霉素在土壤中的吸附解吸规律对抗生素环境风险评价与污染控制具有重要的理论与现实意义。通过改变土壤水溶液中离子强度及类型研究其对土霉素在草甸土中吸附的影响,以期为评价该种抗生素对草甸土土壤环境风险提供科学依据。土霉素测定方法选择高效液相色谱法。以V（乙腈）∶VNaH2PO4（0.01mol·L-1）]=25∶75为流动相,在流速为1 mL·min-1,检测波长为355 nm条件下进行测定。试验以OECD Guideline 106为基础,采用批平衡法研究不同离子强度（0.01、0.03、0.05、0.08、0.10 mol·L-1CaCl2溶液）和不同阳离子（0.01 mol·L-1的NaCl、KCl、MgCl2溶液）对土霉素在草甸土中的吸附影响。结果表明：随着CaCl2浓度的增加,土霉素在草甸土中的吸附量呈降低趋势,且不同浓度的土霉素在草甸土中吸附量受离子强度的影响是不同的。土霉素浓度较低时,其在草甸土中吸附能力受离子强度影响较土霉素浓度高时小。以土壤吸附系数Kd衡量土壤吸附抗生素能力,当土壤样品中离子强度增大时,其对应Kd值呈非线性趋势减小。这说明,在某一Ca2＋浓度范围内,其对吸附的影响较其他浓度范围要大。对相邻CaCl2浓度处理得出的Kd值进行t检验,在CaCl2溶液浓度在0.01与0.03 mol·L-1间得出的Kd值存在显著性差异（p≤0.05）,在0.03、0.05、0.08、0.10 mol·L-1浓度间得出的Kd值均没有显著性差异（p〉0.05）。这一结果说明当CaCl2溶液浓度在0.01~0.03 mol·L-1时,其对土霉素在草甸土中的吸附影响较其他浓度范围大。以Freundlich方程对NaCl、KCl、MgCl2溶液条件下土霉素在草甸土中的吸附进行拟合,土样lg Kf值为lg Kf（Mg2＋）0.05）。这说明,不同阳离子对土霉素在草甸土上的吸附量（lg Kf）影响的差异并不显著。

Influence of different strength and species of cation on adsorption of oxytetracycline in meadow soils

Oxytetracycline （OTC）, one of the tetracycline class of antibiotics, is more widely used in China. It has important significance theoretically and practically to explore the law of adsorption-desorption of OTC in soil for environmental riskassessment and pollution control of antibiotics. In this study, ionic strength and type in soil water solution were changed to reveal the influence on the adsorption of OTC in meadow soil, aiming at providing a scientific basis for evaluating the environmental risk of OTC in meadow soil. HPLC was the determination method of OTC, which acetonitrile： NaH2PO4 （0.01 mol·L-1） =25∶75 （volume ratio） was as mobile phase at a flow rate of 1 mL·min-1and detection wavelength was 355 nm. On the basis of OECD Guideline 106, bath sorption methods were employed to reveal the effect of cation strength （ranging from 0.01 to 0.10 mol·L-1CaCl2） and different cation （0.01 mol·L-1solution of NaCl, KCl, MgCl2） on OTC sorption process in the meadow soil. Results indicated that the adsorption capacity of OTC in meadow soil gradually decreased with the increasing of concentrations of CaCl2, and the adsorption capacity of different concentrations of OTC in meadow soil was affected by different ionic strength. Compared with higher OTC concentrations, the influence of ionic strength was negligible to the sorption at lower OTC concentrations. The soil adsorption coefficient （Kd） was used to measure the ability of adsorption of OTC in meadow. When ionic strength in soil samples increased, its correspondingKdwould decreased with a non-linear trend. This result showed that there definitely existed a certain concentration range of Ca2＋ that had the biggest effect on adsorption than other concentration range. TheKd of the adjacent concentration CaCl2 were handled with T-test, showing that the value ofKd existed a significant difference when the concentration ranges of CaCl2 were from 0.01 mol·L-1 to 0.03 mol·L-1（p≤0.05）, while when the the concentration ranges of CaCl2w