Pedosphere 23(4): 523--531, 2013
ISSN 1002-0160/CN 32-1315/P
©2013 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Effects of earthworms and ryegrass on the removal of fluoranthene from soil |
JING Yong-Ping, LIU Man-Qiang, YIN Qi-Peng, LI Hui-Xin and HU Feng |
| College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095 (China) |
| ABSTRACT |
| Earthworms can promote the bioremediation of contaminated soils through enhancing plant growth and microorganism development as well. The individual and combined effects of earthworms and ryegrass (Lolium multiflorum Lam.) on the removal of fluoranthene from a sandy-loam alluvial soil were investigated in a 70-d microcosm experiment. The experiment was set up in a complete factorial design with treatments in four replicates: without earthworms or ryegrass (control, CK), with earthworms only (E), with ryegrass only (P), and with both earthworms and ryegrass (EP). The residual fluoranthene, microbial biomass C, and polyphenol oxidase activity in the soil changed significantly (P < 0.01) with time. In general, the residual concentration of fluoranthene in the soil decreased sharply from 71.8--88.7 to 31.7--37.4 mg kg-1 in 14 d, and then decreased gradually to 19.7--30.5 mg kg-1 on the 70th d. The fluoranthene concentration left in the soil was the least with both earthworms and ryegrass, compared to the other treatments at the end of the experiment. Half-life times of fluoranthene in the E, P, and EP treatments were 17.8%--36.3% smaller than that of CK. More fluoranthene was absorbed by earthworms than ryegrass. However, the total amounts of fluoranthene accumulated in both the ryegrass and earthworms were small, only accounting for 0.01%--1.20% of the lost fluoranthene. Therefore, we assumed that microbial degradation would play a dominant functional role in fluoranthene removal from soil. We found that earthworms significantly increased microbial biomass C and polyphenol oxidase activity (P < 0.01) in the presence of ryegrass at the end of the experiment. Furthermore, microbial biomass C and polyphenol oxidase activity were significantly (P < 0.05) and negatively related to the residual fluoranthene concentration. This implied that earthworms might promote the removal of fluoranthene from soil via stimulating microbial biomass C and polyphenol oxidase activity. |
| Key Words: microbial biomass C, microbial degradation, plant growth, polyphenol oxidase activity, residual concentration |
| Citation: Jing, Y. P., Liu, M. Q., Yin, Q. P., Li, H. X. and Hu, F. 2013. Effects of earthworms and ryegrass on the removal of fluoranthene from soil. Pedosphere. 23(4): 523-531. |
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