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赤泥是氧化铝生产工业产生的一种固体废弃物,据统计每生产1 t氧化铝,就产生0.8~1.5 t赤泥。世界范围内的赤泥堆存量大约为5.0×109 t,并仍以每年1.2×108 t的增长速率在不断增长[1]。中国作为氧化铝生产大国,目前赤泥堆存量达6×108 t以上[2],且以每年7×107 t的速率增长[3]。赤泥强碱性、高盐分、细粒度,使其资源化综合利用面临诸多难题[4]。同时,赤泥大量堆存所造成的环境安全问题不仅严重制约着氧化铝工业的高质量发展,也给区域生态保护带来严峻挑战。
赤泥壤质化改良既可改善赤泥的理化性质,又能恢复其生态系统。因此,在赤泥规模化安全处置方面引起了国内外的广泛关注[5-6]。近年来,围绕赤泥壤质化改良,国内外学者分别以石膏、沸石等无机矿物材料,有机肥、活性污泥等有机质材料以及嗜碱微生物等生物材料为改良剂,开展了系统研究并取得了显著成效[7-10]。其中,有机材料在促进赤泥壤质化改良、维持其生态可持续性方面的功能优于其他改良材料[3,8]。如DONG等[10]的研究表明,有机材料不仅在促进赤泥颗粒团聚方面的作用优于Ca2+作用,且随着培养时间的增加显著提升了微生物群落的代谢能力及其胞外酶活性,使其基质理化环境、生物学特征逐渐趋于赤泥堆场周围自然土壤。有研究表明,增施老化生物炭可提高赤泥对氮肥的持留能力,改善赤泥的肥力条件[11-13],但鉴于赤泥的堆存量巨大,该措施的经济可行性值得商榷。而相比之下,价格低廉的堆肥、干草等有机质,既可有效降低赤泥的盐碱性、改善物理性质,还可促进赤泥有机碳积累,提高赤泥的肥力水平,进而为维持赤泥堆场的生态可持续性奠定良好的基础[14-16]。因此,选取成本低廉、环保、易得的有机材料 (如农作物秸秆) 作为改良剂,用于赤泥堆场的植被重建和生态修复,被认为是一种经济可行的方法[6,14]。作物秸秆具有来源广泛、价格低廉和环保可再生等优点,是用于赤泥壤质化改良的理想材料。前期研究表明,与有机肥和活性污泥相比,作物秸秆在改善赤泥的生物地球化学特性和肥力条件方面效果更好[10]。但目前关于农作物秸秆促进赤泥壤质化改良的过程、生物驱动机制及其地球生物化学循环特征尚缺乏深入了解,故对生物质应用于赤泥壤质化改良工程尚存在异议[6]。
本研究以玉米秸秆为改良材料,通过分析不同培育时间赤泥基质的盐碱性、颗粒团聚特征,并结合土壤酶活性和微生物群落代谢功能等生物指标分析,评估和探讨玉米秸秆对赤泥壤质化改良的促进作用及其作用机理,以明确生物质改良促进赤泥壤质化改良的有效性和可持续性,从而为赤泥规模化生态处理提供参考。
生物质对赤泥壤质化改良的促进作用
Effect of biomass on soil amelioration of red mud
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摘要: 为解决赤泥的规模化安全处置问题,以拜耳法赤泥为研究对象,选用玉米秸秆为改良剂,通过分析各改良处理的基本理化指标、土壤酶活性以及微生物群落代谢水平等指标的变化,探究了生物质改良对赤泥壤质化改良的促进作用。结果表明,生物质添加可显著降低赤泥的盐碱性。其中,pH、电导率(EC)和盐碱度(Exchangeable sodium saturation percentage, ESP)分别降至9.89、0.461 mS·cm−1和35.2%,且随添加比例的增加改良效果更佳。经生物质添加处理,赤泥基质容重显著降低、孔隙度显著增加,颗粒平均重量直径(Mean weight diameter, MWD)增加至0.38 mm。经生物质改良处理,赤泥中微生物群落的生长代谢水平、多样性以及土壤脲酶、磷酸酶和脱氢酶的活性均有显著升高。冗余分析(Redundancy analysis, RDA)结果表明,微生物群落多样性参数与pH、EC和ESP呈负相关,与MWD呈正相关。本研究结果可为赤泥规模化生态处理提供参考。Abstract: To explore the large-scale safe disposal of red mud produced by the Bayer process of bauxites, the soil amelioration of biomass on red mud was evaluated by amending the crashed cornstalk over a year of outdoor cultivation. The physico-chemical and biological properties of the amended red mud were determined regularly, including pH, EC, EPS, bulk density, aggregates distribution, soil enzyme activity and microbial indicators. The results showed that, the addition of biomass could reduce the alkalinity and salinity of red mud significantly (p<0.05), and with increase of biomass addition, the pH, EC and ESP (Exchangeable sodium saturation percentage) of red mud decreased to 9.89, 0.461 mS∙cm−1 and 35.2%, respectively. Biomass addition could significantly improve the bulk density and porosity of red mud by increasing the mean weight diameter (MWD, up to 0.38 mm) of red mud matrix particles. The microbial metabolic levels and diversity, as well as soil enzyme activities were significantly increased with the amendment of cornstalk biomass (p<0.05). The further redundancy analysis indicated that the selected biological indicators were significantly negative to the alkaline indexes (to pH, EC, and ESP) and positive to MWD. The results of this study can provide the basis for large-scale soil amelioration of red mud.
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Key words:
- red mud /
- cornstalk biomass /
- soil genesis /
- salinity /
- microbial community /
- soil enzymes
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表 1 各改良处理的微生物群落功能多样性指数
Table 1. Functional diversity indexes of soil microbial community
培养时间/d 处理组 平均颜色变化率
(AWCD)Shannon
指数(H)Simpson
指数(D)30 RM 0.059±0.022c 0.70±0.032d 0.85±0.007b 3-RM 0.145±0.032b 1.41±0.046c 0.91±0.008a 5-RM 0.143±0.021b 1.56±0.056b 0.89±0.005a 10-RM 0.185±0.017a 1.84±0.071a 0.89±0.012a 180 RM 0.149±0.015d 2.15±0.095c 0.86±0.015c 3-RM 0.274±0.013c 2.61±0.086b 0.91±0.015b 5-RM 0.334±0.035b 2.61±0.075b 0.91±0.014b 10-RM 0.399±0.014a 3.25±0.050a 0.95±0.007a 360 RM 0.599±0.012d 5.19±0.072d 0.92±0.013a 3-RM 0.766±0.017c 5.75±0.061c 0.93±0.016a 5-RM 0.933±0.032b 6.88±0.091b 0.94±0.012a 10-RM 1.080±0.012a 7.34±0.084a 0.95±0.021a 注:数据后字母不同表示同一取样时间不同处理5%差异显著水平。 -
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