蚯蚓对2,4-DCP污染土壤的毒性响应及微生物群落影响

Toxic response of earthworms(Eisenia fetida)to 2,4-DCP contaminated soil and the impact of microbial community

2.4-二氯苯酚(2.4-DCP)作为合成农药、医药的中间体,在我国广泛生产和使用,其生态危害性已引起广泛关注.然而,关于土壤动物、微生物对2.4-DCP的毒性响应知之尚少.基于此,本研究以赤子爱胜蚓(Eisenia fetida)为受试生物,从致死浓度、抗氧化系统、病理学和行为特征角度评价2.4-DCP对蚯蚓的毒性,通过高通量测序分析土壤微生物群落变化.此外,还探讨了蚯蚓对土壤中2.4-DCP的降解动力学和微生物多样性影响.结果表明,2.4-DCP对蚯蚓7 d半致死浓度(LC_(50))值为29.55 mg·kg^(-1),14 d为28.76 mg·kg^(-1);蚯蚓体内超氧化物歧化酶(SOD)随暴露时间、浓度增加总体呈下降趋势(P<0.01),而过氧化氢酶(CAT)和丙二醛(MDA)呈缓慢上升趋势(P<0.01);当2.4-DCP暴露浓度为15 mg·kg^(-1)时,14 d可使蚯蚓表皮细胞发生凹陷并破裂,浓度达到25 mg·kg^(-1)时,蚯蚓表皮细胞丧失规则细胞排列结构,肠上皮细胞发生细胞间隙扩大和破裂现象;2.4-DCP浓度越高,对蚯蚓的行为特征影响越明显;2.4-DCP在添加蚯蚓和未添加蚯蚓土壤中的降解动力学均符合一级动力学模型,在添加蚯蚓土壤中的降解速率(0.20 d^(-1))明显高于未添加(0.08 d^(-1));2.4-DCP可抑制土壤微生物群落多样性,但蚯蚓活动、蚓粪的产生可分别增加土壤中一些具有降解有机物功能的好氧、厌氧菌属丰度.本研究旨在揭示2.4-DCP与土壤动物及微生物的相互作用关系,为综合评价2.4-DCP的毒性和风险提供理论参考.

2,4-dichlorophenol(2,4-DCP),as an intermediate in the synthesis of pesticides and pharmaceuticals,is widely produced and used in China,and its ecological hazard has aroused widespread concern.However,little is known about the toxic response of soil animals and microorganisms to 2,4-DCP.Based on this,this study took Eisenia fetida as the test organism,evaluate the toxicity of 2,4-DCP to earthworms from the perspective of lethal concentration,antioxidant system,pathology and behavioral characteristics,and analyze the changes of soil microbial community through high-throughput sequencing.In addition,the degradation kinetics and microbial diversity of 2,4-DCP by earthworms were also discussed.The results showed that the LC_(50) value of 2,4-DCP to earthworms was 29.55 mg·kg^(-1) for 7 days,and 28.76 mg·kg^(-1) for 14 days;The superoxide dismutase(SOD)in earthworms decreased with the increase of exposure time and concentration(P<0.01),while catalase(CAT)and malondialdehyde(MDA)increased slowly(P<0.01);When the exposure concentration of 2,4-DCP is 15 mg·kg^(-1),the earthworm epidermal cells can be dented and ruptured for 14 days,when the concentration reaches 25 mg·kg^(-1),the earthworm epidermal cells lose the regular cell arrangement structure,and the intestinal epithelial cells have the phenomenon of cell gap expansion and rupture;The higher the concentration of 2,4-DCP,the more obvious the effect on the behavioral characteristics of earthworms;The degradation kinetics of 2,4-DCP in the soil with and without earthworms conforms to the first-order kinetic model,and the degradation rate in the soil with earthworms(0.20 d^(-1))is significantly higher than that in the soil without earthworms(0.08 d^(-1));2,4-DCP can inhibit the diversity of soil microbial community,but the activity of earthworms and the production of earthworm manure can respectively increase the abundance of aerobic and anaerobic bacteria in the soil that have the function of degrading organic matter.The purpose of this study is to reveal the interaction between 2,4-DCP and soil animals and microorganisms,and provide theoretical reference for comprehensive evaluation of 2,4-DCP toxicity and risk.