Toxic effect of multiple-time overlying pollution of Phe in soil on eisenia fetida

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    Phenanthrene (Phe), a typical persistent PAHs (polycyclic aromatic hydrocarbons) type organic pollutant, is accumulating step by step in low dosage, posing a potential threat to the soil environment. As one-time Phe pollution of the soil differs in process from gradual accumulation of Phe pollution in low dosage, it is very likely to overestimate environmental risk of the Phe entering the soil in the first manner. Phe entering the soil does not diffuse or translocate in the soil. Therefore, most Phe stays in aqueous phase in the soil due to short soil-Phe contact time. In this paper, a multiple-time addition method was used to simulate of the process of Phe accumulation in the soil. With the multiple-time addition approach, Phe was added into the soil in low dosage 12 times, whereas with the one-time addition method, the same quantity of Phe was added into the soil all at once. Then, bioavailability and toxic effects on enzyme activity in earthworm coelomocytes, chromosome and lysosome membrane of the earthworms exposed to the pollutant at different aging phases (1, 7, 14, 28, and 56 d) were analyzed. It was found that with soil incubation going on, content of available Phe, Phe accumulation in earthworm, activity of SOD and POD in earthworm coelomocytes, content of MDA and micronucleus rates (MNR) all dropped rapidly in the early period (1~28 d) and slowed down their drops gradually in the late period (29~56 d), but neutral red retention time (NRRT) kept rising on steadily, indicating that Phe toxicity to earthworm declined with soil incubation going on. Under the condition of multiple-time overlying pollution and one-time pollution, soil available Phe decreased by 1.12 µg kg-1 d-1 and 3.08 µg kg-1 d-1, respectively, during the early stage (1~28 d) of incubation and by 0.17 µg kg-1 d-1 and 0.39 µg kg-1 d-1, respectively, during the late stage (29~56 d) and Phe accumulation in earthworms did by 7.59 µg kg-1 d-1 and 21.46 µg kg-1 d-1, respectively, during the early stage, and by 0.63 µg kg-1 d-1 and 1.91 µg kg-1 d-1, respectively, during the late stage. Soil available Phe (Tenax-TA extractable Phe) was in highly significant positive relationship (R2=0.887 9, p<0.01) with Phe accumulation in earthworms and in highly significant relationship, too, with SOD and POD activities, MDA content, micronucleus rate and NRRT in earthworm coelomocytes with the coefficient of determination being 0.893 4, 0.870 9, 0.930 5, 0.893 3 and 0.885 1, respectively. During the 56 days of aging, soil available Phe and Phe accumulation in earthworms was 23.19%~50.15% and 12.64%~57.89% lower, respectively; SOD and POD activities in earthworm coelomocytes 3.40%~47.24% and 6.49%~38.02%, respectively; MDA content 21.30%~57.82% lower; and MNR in earthworm coelomocytes 2.48%~22.99% lower, while NRRT in earthworm coelomocytes was 1.35%~13.97% higher in the soil subjected to multiple-time overlying pollution than in the soil subjected to one-time pollution, which indicates that Phe entering into the soil through multiple-time overlying pollution is lower than that through one-time pollution in toxicity to earthworms. This finding can be cited as theoretic basis for assessment of eco-toxicity of PAHs-type organic pollutants in soil.

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Ma Jingjing, Qian Xinchun, Zhang Wei, Zheng Bin, Ge Gaofei, Gao Hongjian. Toxic effect of multiple-time overlying pollution of Phe in soil on eisenia fetida[J]. Acta Pedologica Sinica,2015,52(6):1374-1382.

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  • Received:January 23,2015
  • Revised:April 01,2015
  • Adopted:June 19,2015
  • Online: August 31,2015
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