Abstract:

Coastal saline land is a valuable agricultural resource in China, but the pollution of polycyclic aromatic hydrocarbons (PAHs) in these areas has been exacerbated by human and other activities. Microbial degradation is an important method for remediation of PAH-contaminated soil. However, the limited environmental adaptability of exogenous microorganisms hinders their practical applications, and there is a growing interest in enhancing in situ remediation by indigenous microorganisms. The tricyclic aromatic hydrocarbon-anthracene, which is difficult to degrade, was used as the representative of PAHs. The mild coastal saline-alkali soil in Zhanjiang City was used as the research object, and Eisenia foetida was used as the test organism. Four groups of treatments were set up (sterilized control: SS, sterilized soil plus earthworm: SE, natural control: OS, and natural soil plus earthworm: OE). The objective was to compare the degradation efficiency anthracene, as well was the physicochemical properties and microbial community structure of soil at the end of incubation in each treatment at different time periods. Additionally, we aimed to determine the enhancement effect of earthworms on anthracene degradation in coastal farmland soils in the western part of Guangdong Province, as well as the contribution rate of the degrading functional microbial populations and key environmental factors. The results showed that earthworms could affect the degradation of anthracene in coastal saline-alkali soil and accelerate its degradation. The degradation rate of anthracene in OS was 40.7%, while the degradation rate of anthracene in SS was only 17.7%. The degradation of anthracene in soil was mainly biodegradable (23.0%), rather than non-biodegradable (17.7%). The highest degradation efficiency of the OE treatment was 62.1%, and the degradation efficiency of the SE treatment was 50.4%. The combined effect of earthworms on non-biodegradation and intestinal flora (32.7%) was higher than their impact on indigenous microbial degradation (21.4%). Furthermore, earthworms influenced the abundance of microorganisms in the soil, particularly increasing the abundance of degrading microorganisms such as Pseudomonadaceae, Burkholderiaceae and Aeromonadaceae. Correlation network analysis showed a significant negative correlation between the residual concentration of anthracene and Burkholderiaceae, Aeromonas, Sphingomonas, and Flavobacteriaceae. In contrast, a significant positively correlation was observed with pH and organic matter. These findings suggest that earthworms can accelerate the degradation of anthracene in coastal saline-alkali soil by affecting pH, organic matter and soil microorganisms.

Key words: coastal saline agricultural soils, earthworms, polycyclic aromatic hydrocarbons, soil properties, biodegradable, microbial community structure

摘要：

滨海盐碱地是中国重要的耕地资源，而人类活动等加重了滨海盐碱地的多环芳烃（PAHs）污染。微生物降解是去除土壤PAHs污染的重要手段。外源微生物的低环境适应性限制了其实际应用，诱导强化土著微生物原位修复具有重要意义。以较难降解的三环芳烃-蒽为多环芳烃代表，湛江市轻度滨海盐碱土为污染研究对象，赤子爱胜蚓（Eisenia foetida）为受试生物，设置4组处理（灭菌对照，SS；灭菌土壤加蚯蚓，SE；自然对照，OS；自然土壤加蚯蚓，OE）。比较不同时间段各处理土壤中蒽的降解效率、理化性质和培养结束时土壤微生物群落结构，明确蚯蚓对粤西地区滨海农田土壤蒽降解的强化效果、降解功能微生物种群和关键环境因子的贡献率。结果表明：蚯蚓能够影响滨海盐碱土壤中蒽的降解，并且加速其降解。在OS中蒽降解率为40.7%，而SS中蒽的降解率仅为17.7%。土壤中蒽的降解以生物降解为主（23.0%），而不是非生物降解（17.7%）。OE处理的降解效率最高为62.1%，SE处理的降解效率为50.4%。蚯蚓强化非生物降解和肠道菌群作用共同的效果（32.7%）高于蚯蚓强化土著微生物降解的效果（21.4%）。同时，蚯蚓影响了土壤中微生物的丰度，提高了假单胞菌科（Pseudomonadaceae）、伯克氏菌科（Burkholderiaceae）和气单胞菌科（Aeromonadaceae）等降解微生物的丰度。相关性网络分析表明，蒽的残留浓度与伯克氏菌科、气单胞菌科、鞘脂单胞菌和黄杆菌（Flavobacteriaceae）为显著负相关，而与pH、有机质为显著正相关，说明蚯蚓能够通过影响pH、有机质和土壤中的微生物，加速滨海盐碱土壤中蒽的降解。

关键词: 滨海盐碱农田土壤, 蚯蚓, 多环芳烃, 土壤性质, 生物降解, 微生物群落结构