沼液养分和重金属农用安全风险分析

Security Risk Analysis on the Nutrients and Heavy Metals of Biogas Slurry in Agricultural Application

[目的]对沼液养分和重金属农用安全风险进行分析,以期为沼液的安全农用提供科学依据。[方法]对秸秆及粪便中温厌氧消化的沼液进行重金属养分分析,并利用不同类型和浓度的沼液进行种子发芽试验。[结果]物料的类型及配比、碱液预处理均对沼液的成分和性质产生影响。碱液预处理可降低沼液中的重金属含量,可提高氮、磷、有机质以及速效成分的含量。沼液中重金属的最高含量分别为镉8.76μg/kg,铬52μg/kg,铅210μg/kg,汞0.512μg/kg,砷140μg/kg,铜、锌的含量较高,分别可达279和680μg/kg,但均低于城镇垃圾农用限定标准值。种子在沼液中的发芽试验验证了5%以下低浓度沼液的催芽作用,但盐胁迫作用使幼苗在沼液中的长期生长受到抑制。[结论]以粪便作为沼液发酵原料时应适当的控制其在进料中的比例或做重金属预去除;当沼液用作液肥以灌溉方式施入农田时,应经稀释或做除盐处理。

[Objective] This study was to provide scientific basis for the security application of biogas slurry in agriculture through the analysis on the security risk of nutrients and heavy metals of biogas slurry in agricultural application.[Method] The components of the slurry produced by the anaerobic digestion of straws and manures were systematically analyzed.Different types of biogas slurry with different concentrations were used to conduct the germination test.[Result] The types and proportions of raw materials,and alkali pretreatment affected the compositions and nature of the biogas slurry.Alkali pretreatment could reduce the contents of heavy metals and improved the contents of nitrogen,phosphorous,organic matter and available components.The contents of heavy metals in the biogas slurry were as follows： Cd of 8.76 μg/kg,Cr of 52 μg/kg,Pb of 210 μg/kg,Hg of 0.512 μg/kg,As of 140 μg/kg,and the contents of Cu and Zn were the highest among the heavy metals,respectively,279 μg/kg and 680 μg/kg.All the contents were under the limit standards of the urban wastes for agricultural use.The germination tests of the seeds verified that the slurry with the concentration of lower than 5% could accelerate the germination,while the salt stress could inhibit the growth of seedlings in the slurry.[Conclusion] When the dung are used as the raw materials for fermentation,appropriate control should be conducted on the feeding proportion or the heavy metals should be pre-removed;when the slurry is used as the liquid fertilizer to apply in the farmland,the dilution or desalting treatment should be conducted at first.