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

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