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全球每年铅消费量约为5×106 t,而回收利用的铅约占其25%,故导致大量的铅进入土壤造成污染[1]。2014年发布的《全国土壤污染状况调查公报》[2]显示,有1.5%的点位铅超标。土壤中的铅可通过食物链和接触进入人体,会对神经系统和造血系统等造成危害[3]。铅污染土壤修复技术包括化学、物理、生物和联合修复技术,其中植物修复作为一种有效、经济和绿色的修复技术,并得到了广泛的研究与应用。受植物生长和土壤中铅生物有效性的限制,植物修复存在速度缓慢的问题。铅的生物有效性与铅赋存形态相关。采用BCR连续提取法可以将土壤中铅分为:酸可溶态、可还原态、可氧化态和残渣态。酸可溶态具有生物有效性;可还原态和可氧化态在一定条件下可以转化为酸可溶态,具有潜在的生物有效性;残渣态被认为是比较稳定的状态,在自然条件下难以被植物吸收[4]。将土壤中不稳定的铅转变为酸可溶态,可以有效提高土壤铅的生物有效性,促进植物修复。
Thiobacillus(硫杆菌)是一种硫自养细菌。近年来,通过筛选Thiobacillus并促进植物修复铅污染土壤的研究逐步得到了关注[5-8]。然而,相关研究关注外源Thiobacillus的筛选以及对植物富集过程的促进,Thiobacillus对土壤微生物群落影响以及土壤铅的形态的影响机制尚不明确。
生物炭发达的孔隙结构能够为微生物提供生存位点,提高土壤微生物活性,吸附并提供微生物所需的营养物质,为微生物提供有利的生长环境[9-10]。YE等[6]于550 °C下制备改性生物炭,添加3%(质量分数)改性生物炭到铅污染土壤后,生物炭能够有效富集外源Thiobacillus,提高铅的生物有效性。因此,通过硫诱导富集土壤土著Thiobacillus,采用生物炭促进Thiobacillus调控土壤铅形态,提高铅生物有效性具有一定的可行性。
本研究基于Thiobacillus生物特性,通过单质硫诱导土壤中Thiobacillus富集,以调节土壤铅形态;以家具厂废料木屑为原料,制备生物炭,促进Thiobacillus的富集,强化Thiobacillus对土壤铅形态的调节作用。本研究旨在考察生物炭和硫对土壤微生物群落结构和土壤理化特性的影响,探明Thiobacillus对土壤重金属赋存形态作用机理,以期为促进铅污染土壤的植物修复提供参考。
生物炭促进硫诱导土著硫杆菌调控土壤铅形态
Biochar promotes the regulation of fraction distribution of soil lead by sulfur-induced indigenous Thiobacillus
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摘要: 外源硫杆菌可以促进植物修复重金属污染土壤,然而硫杆菌对土壤中铅的活化作用机理尚不明确。通过土培实验,研究了单质硫和生物炭对土著硫杆菌的诱导作用和对土壤铅形态的作用机理。结果表明,单质硫能够诱导并富集土壤中的土著硫杆菌,相对丰度从0.02%增加至6.99%。生物炭促进了诱导作用,添加生物炭和单质硫,硫杆菌相对丰度增加至13.33%。同时添加3%(质量分数)生物炭和0.5%(质量分数)单质硫培养60 d后,土壤pH从7.83降低至6.64,Eh先降低至230 mV,后逐渐增加至299 mV;有机碳从19.40 g·kg−1增加至28.29 g·kg−1;土壤中铅由可还原态向酸可溶态、可氧化态和残渣态转变,可还原态铅减少了20.13%,酸可溶态、可氧化态和残渣态分别增加了53.76%、35.29%和69.40%。单质硫和生物炭能够富集土著硫杆菌,提高铅的生物有效性,同时对部分铅起到钝化固定作用。本研究可为提高土壤中铅的生物有效性以促进植物修复铅污染土壤提供参考。Abstract: The promotion of exotic Thiobacillus on phytoremediation has attracted in recent years, however, the mobilization mechanism of Thiobacillus on soil lead is still unclear. The mechanism of sulfur and biochar on the induction of indigenous Thiobacillus and the distribution of soil lead content were studied through soil culture experiments. The relative abundance of Thiobacillus in soil was increased from 0.02% to 6.99%, which was inducted by sulfur in soil. The induction was promoted by biochar. The relative abundance of Thiobacillus was increased to 13.33% with biochar addition. With a 3% (mass fraction) of biochar and 0.5% (mass fraction) of sulfur addition in a 60 d pot experiment, the soil pH was decreased from 7.83 to 6.64. The soil Eh was decreased to 230 mV directly at the beginning of experiment, and increased to 299 mV after 60 d. The soil organic carbon was increased from 19.40 g·kg−1 to 28.29 g·kg−1. 20.13% of reducible Pb species was transformed to acid extractable, oxidizable and residual Pb species, which was increased by 53.76%, 35.29% and 69.40%, respectively. The combined of biochar and sulfur can promote the bioavailability, and immobilize Pb in soil at same time. This study can provide an approach for regulating the Pb bio-availability for phytoremediation of Pb-contaminated soil
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Key words:
- Pb-contaminated soil /
- Thiobacillus /
- biochar /
- form of heavy metal /
- bioavailability
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表 1 铅污染土壤性质
Table 1. Major physicochemical characteristics of Pb-contaminated soil
黏粒/% 粉粒/% 砂粒/% pH Eh/mV 22.93 48.94 28.13 7.83 258 全磷/(g·kg−1) 有机碳/(g·kg−1) 全氮/(g·kg−1) Pb/(mg·kg−1) 1.07 19.4 1.15 995.31 表 2 土壤微生物多样性指数
Table 2. Bacterial diversity indices of soils
实验组别 Shannon Simpson Ace Chao 1 Coverage CK 4.87 0.014 576.82 575.50 0.999 067 S 4.61 0.021 576.04 568.33 0.998 725 BCS 4.53 0.029 531.81 522.65 0.998 663 表 3 各实验组土壤养分
Table 3. Nutrient content of the soil
实验组别 TN/(g·kg−1) SOC/(g·kg−1) TP/(g·kg−1) C/N C/P CK 1.132 19.371 1.05 17.11 18.45 BC 1.254 28.315 1.15 22.58 24.62 S 1.142 20.436 0.98 17.89 20.85 BCS 1.259 28.291 1.16 22.47 24.39 -
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