模拟湿地土壤微塑料暴露下藓类植物的生长和抗氧化酶活的响应特征

Response characteristics of the growth and antioxidant enzyme activity of mosses under microplastics stress in simulated wetland soils

为评价湿地土壤环境中微塑料(Microplastics, MPs)对藓类植物的生态效应,选取聚丙烯(PP)、聚苯乙烯(PS)和聚乙烯(PE)3种微塑料,通过室内模拟湿地土壤环境微塑料的暴露胁迫实验,观测藓类的主要生长指标和抗氧化酶活指标的变化,研究不同粒径微塑料胁迫下藓类的生理生态响应特征.结果表明,当粒径Φ48μm的PP和PS微塑料暴露浓度分别达到800 mg·kg^(-1)和640 mg·kg^(-1)时,植株高和鲜重均受显著抑制,且PS对藓类生长的抑制影响最显著;而粒径分别为Φ74μm和Φ150μm的PP和PS及3种粒径的PE暴露对植株高和鲜重均无显著抑制.不同微塑料胁迫对藓类植物的抗氧化酶活指标SOD(超氧化物歧化酶)、POD(过氧化物酶)、CAT(过氧化氢酶)的影响均较一致.粒径Φ48μm的PP和PE微塑料在800 mg·kg^(-1)暴露浓度下,以及Φ48μm的PS微塑料暴露浓度在640 mg·kg^(-1)以上时,藓类植物的3种酶活指标均有显著变化,且呈先升后降趋势,以PS对植物的抗氧化系统影响最显著;但粒径Φ74μm和Φ150μm的3种微塑料暴露对藓类的抗氧化酶活影响均不显著.湿地土壤中藓类植物对微塑料具有一定的耐受性,能够适应一定粒径(Φ74μm)以上的微塑料胁迫,并依靠其特殊的形态结构特征阻止微塑料污染物破坏其抗氧化酶系统.因此,可以考虑以藓类植物作为水陆交错区湿地土壤中截留或阻控微塑料等污染物的主要植物类群,并在未来可开展应用开发领域的可行性研究,将藓类植物作为拦截地表径流中携带的微塑料等新型污染物进入水体的天然有效植物屏障,为湿地微塑料的植物截留或污染防控提供一定的参考指导.

In order to evaluate the ecological effects of microplastics(MPs)on mosses in wetland soil environment,three types of MPs,including polypropylene(PP),polystyrene(PS)and polyethylene(PE),were selected in this study,and the changes of plant height,fresh weight and the main antioxidant enzyme activity indexes of mosses were observed through indoor simulated stress control experiments of microplastics in wetland soil environment to study the physiological and ecological responses of mosses under different particle sizes of MPs stress.The results showed that moss plant height and fresh weight were significantly inhibited when PP-MPs and PS-MPs withΦ48μm particle size were exposed to 800 mg·kg^(-1) and 640 mg·kg^(-1),respectively,and PS-MPs had the most significant inhibitory effect on the growth of moss plants,while PP and PS withΦ74μm andΦ150μm particle size and PE with three particle sizes did not significantly inhibit the plant height and fresh weight of moss plants.The effects of the MPs stress on superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT),the main indicators of antioxidant enzyme activities in mosses,were relatively consistent.The three enzyme activity indicators of mosses were significantly changed at the exposure concentration of 800 mg·kg^(-1) for PP-MPs and PE-MPs with the particle size ofΦ48μm,when the exposure concentration of PS-MPs was 640 mg·kg^(-1) or more with the particle size ofΦ48μm,it showed a trend of increasing and then decreasing,and PS-MPs had the most significant effects on the antioxidant system of mosses.However,the effects of the three types of MPs with the particle size ofΦ74μm andΦ150μm on the antioxidant enzyme activities of mosses were not significant.In this study,it is found that moss plants in wetland soils can adapt to various MPs above a certain particle size(Φ74μm)stresses and can rely on their special morphological and structural characteristics to prevent MPs pollutants from damaging their antioxidant enzyme systems.Therefore,moss plants can be considered as the main plant groups for retaining or blocking MPs and other emerging pollutants of the wetland soils in water-land interface areas,and feasibility studies can be carried out in the future on the application and development of moss plants as a natural and effective plant barrier to intercept surface runoff carrying MPs and other new pollutants into water bodies,so as to provide important references for plant retention and pollution prevention and control of MPs in wetlands.