Roles of Earthworm in Phytoremediation of Pyrene Contaminated Soil

27 Mar Roles of Earthworm in Phytoremediation of Pyrene Contaminated Soil

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Abstract

采用盆栽试验法，研究了蚯蚓( Pheretima hupeiensis) 在植物修复芘污染土壤中的作用。结果显示，试验浓度( 20． 24 321. 42 mg kg) 范围内，蚯蚓活动促进了芘污染土壤中修复植物黑麦草( Lolium multiforum) 黑麦草的生长，其根冠比明显增大。 添加蚯蚓 72 d 后，种植黑麦草的土壤中芘的去除率高达 60． 01% 86． 26% ，其平均去除率( 74． 66% ) 比无蚯蚓活动的土壤-植 物系统( 64． 55% ) 提高 10． 11% ，比无植物对照组( 18． 24% ) 提高 56． 42% 。各种生物、非生物修复因子中，植物-微生物交互作 用对芘去除的平均贡献率( 51． 75% ) 最为突出，比无蚯蚓活动时( 44． 94% ) 提高 6． 81% 。说明蚯蚓活动可强化土壤-植物系统 对土壤芘污染的修复作用

English Abstract

Soil contamination by organic compounds，especially by the petroleum-derived polycyclic aromatic hydrocarbons
( PAHs) ，is a growing problem with serious environmental consequences． To evaluate the contribution of the soil
macrofauna on the dissipation of PAHs in rhizosphere soil，a pot experiment was carried out to investigate effect of
earthworm ( Pheretima hupeiensis) on ryegrass ( Lolium multiforum) remedying soils polluted by pyrene in，and roles of
biotic ＆ abiotic factors in the process of dissipation of pyrene in soils were estimated． After washing with sterile distilled
water，eight adult earthworms ( 7 to 8 cm in length) were added on the top of sample soil of each treated pots at initial
experiments，giving ( a) unplanted microbe-inhibited pots with spiked soil ( 0． 1% NaN3 was used to inhibit the microbial
activity) ，( b) unplanted pots with spiked soil，( c) planted microbe-inhibited pots with spiked soil ( 0． 1% NaN3 was
used) ，( d) planted pots with spiked soil and ( e) planted pots with unspiked soil，and each treatment was established with
five replications． Results showed that earthworm activity promoted growth of ryegrass growing in soils at initial
concentrations of pyrene ranging from 20． 24 to 321． 42 mg kg，whose biomass per plant was 15． 65% —21． 32% larger
than those in corresponding treatments without earthworm introduced in，and apparently facilitated its root shoot ratio，
which was 20． 44% 24． 24% greater than those in corresponding non-inoculated soils at the end of the experiment．
Seventy-two days after earthworms were introduced in，residual pyrene concentrations ( 2． 78 to 128． 53 mg kg) in vegetated
soils were much lower than the respective initial values，and the values varied significantly among treatments． During the
experiment，averagely 74． 66% of pyrene was removed from the soils with plantation of grass and incubation of earthworm，
which was 10． 11% higher than those with only plantation of ryegrass，and 56． 42% higher than those without plantation of
ryegrass and earthworm inoculation． As compared to those treatments with same pollution levels，the contents of pyrene
accumulated in plant tissues growing in soils with earthworms were always lower than those without earthworm． Along with
the increments of soil pyrene concentrations from 20． 24 to 321． 42 mg kg，the extractable pyrene in roots and shoots of ryegrass growing in soils without earthworms increased from 4． 11 to 16． 79 mg kg and from 0． 87 to 3． 01 mg kg，while they
did from 2． 32 to 11． 17 mg kg and from 0． 51 to 2． 01 mg kg when earthworms were introduced in，respectively． Despite
incubation of earthworm evidently enhanced the remediation of pyrene in soils，contributions of biotic and abiotic factors to
phytoremediation process displayed distinct diversity． Of 10． 11% enhanced removal of the total pyrene，abiotic loss，
earthworm accumulation，phytodegredation and microbial degradation accounted for 0． 16% ，0． 08% ，0． 42% and 2． 64% ，
respectively． Among all the remedying factors，the plant-microbial interaction was proved to be the primary pathway for
pyrene degradation，whether the presence of earthworms or not，which accounted for 51． 75% of the total removal，and was
6． 81% higher than those in corresponding soils without earthworm activity． These findings suggest a feasible way for the
establishment of high-efficient phytoremediation of soil PAHs pollution by introducing earthworms into the soil-plant system．