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摘要: 为解决土壤重金属污染问题,纳米零价铁(nZVI)被广泛应用且备受关注, 而nZVI对土壤无脊椎动物、土壤质量、微生物群落等的潜在影响缺乏系统的研究。本文以赤子爱胜蚓(Eisenia foetida) [蚯蚓密度为0、10条∙kg−1(土)]为研究对象, 探讨不同浓度nZVI (nZVI土壤质量为0、0.05%、0.25%和0.50%) 暴露15 d、30 d和45 d后,蚯蚓-微生物-土壤生态系统的响应, 为评价nZVI的环境安全性提供参考。结果表明, 暴露45 d后, nZVI对蚯蚓存活率和生物量无显著影响, 0.50% nZVI处理的蚯蚓存活率和体内MDA含量与15 d相比分别降低27.66%和0.86 nmol∙g−1; 而蚯蚓生物量和CAT活性分别增加1.20倍和2.62倍。门或属水平下, nZVI对土壤微生物相对丰度、多样性指数和丰度指数无显著影响; 与无添加nZVI处理相比,蚯蚓介导下 0.50% nZVI处理土壤中大团聚体(>250 μm)所占比例、团聚体平均重量直径和速效磷含量分别显著升高15.69%、12.59%和21.20%。蚯蚓介导下nZVI处理中土壤大团聚体所占比例、团聚体平均重量直径显著高于无蚯蚓投加的nZVI处理, 可见, nZVI胁迫下蚯蚓活动极显著提高土壤团聚体结构的稳定性(P<0.01)。本研究发现长期暴露nZVI对土壤微生物群落特征无显著影响, 但可以促进蚯蚓的生长, 从而进一步提高了土壤营养元素的生物有效性, 为nZVI应用于污染修复与治理的环境安全性评估提供了科学依据。Abstract: Nano-zero-valent iron (nZVI) is widely used to remedy soil heavy metal pollution. However, the potential effects of nZVI on soil invertebrates, soil quality and microbial communities have not been well studied. In this study, we used Eisenia foetida (0, 10 pieces per kilogram soil) as the test species and examined the potential effects of nZVI (mass ratios of 0, 0.05%, 0.25%, and 0.50%) on the earthworm-bacteria-soil ecosystems after 15, 30, and 45 days of exposure. The results showed that after 45 days of exposure, there was no significant difference in survival rate and biomass of earthworms. The earthworm survival rate and content of malondialdehyde in the 0.50% nZVI system decreased by 27.66% and 0.86 nmol∙g−1, respectively, compared with those on day 15. However, the earthworm biomass increased by 1.20 times, and the catalase activity increased by 2.62 times. At the phylum or genus level, nZVI had no significant effects on the relative abundance, diversity index, and abundance index of soil microorganisms. Compared with the 0 nZVI system, the proportion of soil large aggregates (>250 μm), the average weight diameter of soil aggregates, and the content of available phosphorus (P) in the 0.50% nZVI system increased by 15.69%, 12.59%, and 21.20% under earthworm-mediated conditions, respectively. The proportion of soil macroaggregates and the average weight diameter of soil aggregates in the earthworm and nZVI composite systems were significantly higher than those in the corresponding single nZVI system, and earthworm activity significantly improved the stability of soil aggregates under nZVI stress (P<0.01). In this study, we found that long-term exposure to nZVI had no significant toxic effects on the community characteristics of soil microorganisms but promoted the growth of earthworms, which further improved the bioavailability of soil nutrients. This study provides a scientific basis for environmental safety assessments of nZVI in soil restoration applications.
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Keywords:
- Nano-zero-valent iron /
- Eisenia fetida /
- Toxic effects /
- Soil aggregates /
- Bacterial diversity
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表 1 纳米零价铁(nZVI)暴露45 d后蚯蚓指标间的相关分析(R值)
Table 1 Correlation analysis of earthworm indicators after 45 days of exposure to nano-zero-valent iron (nZVI) (R value)
指标
Index存活率
Survival rate生物量减少量
Reduction of biomassCAT活性
CAT activitySOD活性
SOD activityMDA含量
MDA content脯氨酸含量
Proline content存活率 Survival rate 1 生物量减少量 Reduction of biomass −0.642** 1 CAT活性 CAT activity −0.192 0.245 1 SOD活性 SOD activity 0.017 −0.102 −0.080 1 MDA含量 MDA content 0.059 −0.084 −0.143 −0.032 1 氨酸含量 Proline content 0.198 −0.266 −0.161 −0.303 −0.029 1 ** 表示在 P<0.01(双尾)显著相关。** indicates significant correlation at P<0.01 (double tails). 表 2 不同添加量纳米零价铁(nZVI)和蚯蚓对土壤细菌丰度和多样性的影响
Table 2 Effects of nano-zero-valent iron (nZVI) on abundance and diversity of soil bacteria (16S rRNA gene) (97% similarity level)
蚯蚓 Earthworm nZVI添加量 nZVI rate (%) 香农指数 Shannon 辛普森指数 Simpson Chao Ace 无 No 0 9.4873±0.3169a 0.9798±0.0010a 2915.06±545.16a 2940.93±570.35a 0.05 9.4325±0.2324a 0.9797±0.0007a 2885.51±323.55a 2916.06±337.59a 0.25 9.4387±0.3604a 0.9796±0.0012a 2771.03±523.41a 2783.71±561.79a 0.50 9.5352±0.2096a 0.9799±0.0006a 3056.69±301.52a 3090.94±320.31a 有 Exist 0 9.5499±0.0525a 0.9800±0.0002a 3157.40±104.32a 3204.63±107.87a 0.05 9.5771±0.0521a 0.9801±0.0002a 3197.37±65.50a 3242.72±64.76a 0.25 9.5796±0.0706a 0.9801±0.0001a 3113.03±91.71a 3156.79±97.9a 0.50 9.5639±0.0606a 0.9800±2.3E-05a 3056.62±154.26a 3089.67±152.81a “a”表示不同处理无显著差异(P>0.05)。“a” represents no significant difference among different treatments at P>0.05 level. 表 3 纳米零价铁(nZVI)胁迫下蚯蚓活动对土壤化学性质的影响
Table 3 Effects of earthworm activities on soil chemical properties under nano-zero-valent iron (nZVI) stress
蚯蚓
EarthwormnZVI添加量
nZVI rate (%)有机质
Organic matter
(g∙kg−1)全磷
Total phosphorus
(g∙kg−1)全氮
Total nitrogen
(g∙kg−1)碱解氮
Alkali-hydrolyzable
nitrogen (mg∙kg−1)速效磷
Available phosphorus
(mg∙kg−1)无 No 0 114.78±16.59a 1.15±0.30ab 3.55±0.2abc 395.68±48.23a 446.22±13.41c 0.05 120.64±13.44a 1.24±0.52ab 3.51±0.37abc 346.56±45.55ab 472.28±9.02bc 0.25 108.27±29.05ab 1.45±0.36a 3.70±0.45ab 368.71±62.44a 452.50±30.30bc 0.50 109.13±9.93ab 1.32±0.15ab 3.93±0.57a 292.28±51.95b 448.62±33.61c 有 Exist 0 103.76±11.52ab 1.28±0.12ab 3.16±0.22c 392.92±38.11a 491.53±23.85b 0.05 114.70±9.33a 0.98±0.40b 3.39±0.17bc 352.70±42.26ab 470.14±43.62bc 0.25 109.44±6.1ab 1.21±0.38ab 3.29±0.19bc 365.46±54.99ab 490.86±24.15b 0.50 88.29±25.41b 1.19±0.07ab 3.28±0.2bc 336.54±98.1ab 540.84±50.45a 同列不同小写字母表示不同处理(蚯蚓+nZVI添加量)间差异显著(P<0.05)。
Different lowercase letters in the same column represent significant differences among different treatments of nZVI and earthworm at P<0.05 level.表 4 纳米零价铁(nZVI)胁迫下蚯蚓活动对土壤质量的双因素方差分析
Table 4 Two factor analysis of variance of earthworm activity on soil quality under nano-zero-valent iron (nZVI) stress (P values)
指标 Index nZVI (N) df 蚯蚓 Earthworm (E) df E × N df 大团聚体质量比 Mass ratio of macroaggregates 6.998** 3 42.990** 1 1.353* 2 小团聚体质量比 Mass ratio of microaggregates 4.750** 3 12.468*** 3 0.221ns 2 黏土质量比 Mass ratio of clay 0.091ns 1 0.214ns 1 1.711ns 1 有机质含量 Organic matter 2.512ns 3 3.499ns 1 0.893ns 3 全氮含量 Total nitrogen 1.182ns 3 17.075*** 1 1.282ns 3 全磷含量 Total phosphorus 0.907ns 3 1.689ns 1 0.959ns 3 碱解氮含量 Alkali-hydrolyzable nitrogen 3.999** 3 0.440ns 1 0.453ns 3 速效磷含量 Available phosphorus 1.710ns 3 21.911*** 1 4.341** 3 平均重量直径 Average weight diameter 3.693ns 1 24.911*** 1 0.001ns 1 ns: P>0.05; *: P ≤0.05; **: P≤0.01; ***: P≤0.001. -
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