Abstract:

It is of great significance to study the toxicity threshold and sensitivity distribution of antibiotics to vegetables for scientifical evaluation on the ecological risks of soil pollution by antibiotics. In this study, tetracycline (TC) was selected as the representative antibiotic to investigate its effect on the seed germination of a variety of vegetables that are widely grown in the Pearl River Delta using the indoor culture method. Taking the index with the greatest influence degree as the test endpoint, the Log-logistic distribution model was used to fit the toxic dose-response relationship of TC, and its IC₅₀ and IC₁₀ were calculated. Taking IC₅₀ as the evaluation parameter, the species sensitivity distribution (SSD) method was employed to construct the SSD curves of TC pollution on different varieties of vegetables, and the toxicity thresholds (hazardous concentration for 5% of the species, HC₅) and the non-effect concentration (PNEC) of TC were obtained. The results showed that the effects of TC contamination on the seed germination of the selected of vegetables in the experiment followed: root elongation>shoot elongation>germination rate. At TC concentration of 10 mg∙L⁻¹, the relative root elongation, relative shoot elongation and germination rates for 9 species of vegetable seeds were 16.9%-72.5%, 42.3%-129.4% and 83%-100%, respectively. The influence level of TC contamination on seed germination not only depended on the measured parameters, but also was closely related to the vegetable species. At TC concentration of 10 mg∙L⁻¹, the relative root elongation of corn (Zea mays L.), cucumber (Cucurbita pepo L.) and squash (Cucurbita pepo L.) were 72.5%, 35.9% and 16.9%, respectively, showing significant differences. The toxic dose-response curves showed that there was considerable difference in toxicity thresholds of TC among different vegetable species, with the maximum IC₅₀ value of 83.60 mg∙L⁻¹ (corn) and the minimum IC₅₀ value of 2.98 mg∙L⁻¹ (cucumber). The SSD curves indicated that the order of cumulative frequency of the sensitivity of different vegetable species to TC toxicity ranked: corn>Chinese flowering cabbage (Brassica parachinensis L.)>Chinese kale (Brassica alboglabra L.)>beans (Vigna unguiculata L.)>Chinese cabbage (Brassica pekinensis L.)>line pepper (Capsicum annuum L.)>mustard (Brassica juncea L.)>squash>cucumber. The results suggested that the corn seeds had the strongest tolerance to TC contamination, while cucumber seeds were the most sensitive to TC. Therefore, cucumber may be selected as the vegetable species to evaluate the ecological risks of TC contamination in the Pearl River Delta. In this experiment, the HC₅ and PNEC values of different vegetable species were 9.64 μg∙L⁻¹ and 1.93 μg∙L⁻¹, respectively.

Key words: tetracycline, ecological risk, species sensitivity distribution, biotoxicity, seed germination experiment, vegetables

摘要：

研究抗生素污染对蔬菜毒性阈值及其敏感性分布，对于科学评价土壤抗生素污染的生态风险具有重要意义。采用室内培养方法，选取四环素（TC）作为代表抗生素，调查其对珠三角地区多种蔬菜品种种子萌发的影响。以影响程度最大的指标为测试终点，采用Log-logistic分布模型，对TC的毒性剂量-效应关系进行拟合，并计算其IC₅₀和IC₁₀。以IC₅₀为评价参数，采用物种敏感性分布法（Species sensitivity distributions，SSD），构建TC污染对不同蔬菜品种的SSD曲线，并获得TC毒性阈值（HC₅）和无效应浓度（PNEC）。结果表明，TC污染对实验所选品种蔬菜种子萌发指标的影响程度为：根长>芽长>发芽率，当TC质量浓度为10 mg∙L⁻¹时，9种品种蔬菜种子相对根长、相对芽长和发芽率分别为16.9%－72.5%，42.3%－129.4%，83%－100%。TC污染对种子萌发的影响程度不仅与测试指标相关，还与蔬菜品种密切相关。当TC质量浓度为10 mg∙L⁻¹时，玉米（Zea mays L.）、青瓜（Cucumis sativus L.）和白瓜（Cucurbita pepo L.）种子的相对根长分别为72.5%、35.9%和16.9%，差异显著。毒性剂量-效应曲线表明，TC对不同品种蔬菜毒性阈值差异较大，IC₅₀最大值为83.60 mg∙L⁻¹（玉米），最小值为2.98 mg∙L⁻¹（青瓜）。SSD曲线表明，不同品种蔬菜对TC毒性敏感性频次分布顺序为：玉米>菜心 (Brassica parachinensis L.)>芥兰 (Brassica alboglabra L.)>豆角 (Vigna unguiculata L.)>白菜 (Brassica pekinensis L.)>线椒 (Capsicum annuum L.)>花叶芥菜 (Brassica juncea L.)>白瓜>青瓜，即玉米种子对TC污染的耐受性最强，青瓜种子对TC最为敏感，可以作为珠三角地区TC污染生态风险评估的蔬菜品种。该实验获得TC对珠三角地区多种蔬菜品种的HC₅为9.64 μg∙L⁻¹，PNEC为1.93 μg∙L⁻¹。

关键词: 四环素, 生态风险, 物种敏感性分布, 生物毒性, 种子发芽实验, 蔬菜