通风方式对牛粪堆肥氨气排放与氮素转化的影响

为揭示通风方式对好氧堆肥过程中氮素转化及损失的影响,设置连续通风T1（通风速率0.2L/（min·kg））和间歇通风T2（平均通风速率0.2L/（min·kg）,通风10min,间歇10min）2个处理,以牛粪和玉米秸秆为原料在反应器中进行好氧堆肥试验。结果表明,堆肥结束后T1和T2处理总氮（TN）损失分别占初始 TN 23.25%和21.12%, TN的损失以NH3挥发为主,分别占 TN损失的74.76%和61.84%,而以N2O排放损失的氮仅占 TN损失的1.12%和1.37%。NH3挥发主要集中在堆肥初期,主要是因为较高的温度和pH值所致,至堆肥结束时T2处理NH3累积排放量比T1处理少24.37%。不同通风方式对堆肥过程中NH+4N和NO-3N的含量变化也产生显著影响,到堆肥结束时,T2处理相比T1处理,其NH+4N含量低11%,而NO-3N含量高6.7%,T2处理酸解总有机氮含量比T1处理高12.4%,说明间歇通风有利于硝化作用和氨同化作用的进行。结构方程模型（SEM）显示,T2处理不同有机氮对NH+4N含量的总影响从大到小顺序为：酰胺态氮(1.006)、氨基糖态氮(0.485)、酸解未知态氮(0.034)、氨基酸态氮(-0.852),说明NH+4N来源于酰胺态氮、氨基糖态氮和酸解未知态氮,同时NH+4N可以通过氨同化作用生成氨基酸态氮,间歇通风能促进NH+4N向氨基酸态氮的转化。间歇通风方式通过抑制有机氮向NH+4N的转化,降低堆肥过程中由NH3排放造成的氮素损失。

Influence of Ventilation Modes on Ammonia Emission and Nitrogen Conversion in Cattle Manure Composting

To reveal the influence of different ventilation modes on nitrogen conversion and loss during the aerobic composting process, the experiment with cattle manure and corn stalk was conducted in the reactor under two different treatments of ventilation modes (continuous ventilation T1 and intermittent ventilation T2). The results showed that the losses of total nitrogen in T1 and T2 accounted for 23.25% and 21.12% of the initial total nitrogen, respectively. Total nitrogen loss was dominated by NH3 volatilization. The nitrogen loss of T1 and T2 treatment from NH3 volatilization accounted for 74.76% and 61.84% and from N2O emission accounted for 1.12% and 1.37% of the total nitrogen loss. NH3 volatilization mainly occurred in the early stage of composting. The cumulative NH3 emissions of T2 treatment was 24.37% less than that in T1 treatment. Different ventilation modes also had significant influences on the content of NH+4N and NO-3N during composting. At the end of composting, compared with T1 treatment, the content of NH+4N in T2 treatment was 11% lower, while the content of NO-3N in T2 treatment was 6.7% higher and the content of total acid-hydrolyzed organic nitrogen was 12.4% higher than that in T1 treatment. T2 treatment could promote the nitration reaction and ammonia assimilation. Structural equation modeling (SEM) indicated that the total effects of different types of organic nitrogen on the content of NH+4N during composting was decreased as follows: amine nitrogen (1.006), amino sugar nitrogen (0.485), hydrolyzable unknown nitrogen (0.034), and amino acid nitrogen (-0.852). Amino sugar nitrogen, hydrolyzable unknown nitrogen and amine nitrogen were most easily converted into NH+4N, while amino acid nitrogen was synthesized from NH+4N during composting. T2 treatment could facilitate the transformations from NH+4N to amino acid nitrogen. Intermittent ventilation could stimulate the growth and activity of microorganisms, and so increasing the accumulation of amino sugar nitrogen. Intermittent ventilation should inhibit the conversion of organic nitrogen to NH+4N, thus reducing the nitrogen loss caused by NH3 emission in the composting process.