Effects Of Different C/N Ratio On NH₃ Volatilization And Transformation Of Organonitrogen Compounds In Aerobic Composting

Aerobic composting,with many advantages such as in-situ treatment,lower cost,high degree of harmlessness and low biological risk has become one of the most widely used ways to utilize agricultural waste resources.However,NH₃ volatilization in composting process not only leads to a significant loss of nitrogen,but also causes serious air pollution.Five C/N treatments were set up in this experiment:T1?C/N=15?,T2?C/N=20?,T3?C/N=25?,T4?C/N=30?and T5?C/N=35?.Using cow dung and corn stalk as raw materials,to study the effects of different C/N ratios on NH₃ volatilization loss?volatilization rate and cumulative emissions?and transformation of organonitrogen compounds in aerobic composting under pile composting conditions.The main test results are as follows:1.The loss of total nitrogen in the compost mainly occurred 24 days before composting,accounting for 11.1%²3.1%of the total nitrogen loss.The lower the C/N ratio,the higher the total nitrogen loss rate;T1^T5 at the end of the compost The total nitrogen loss rates were 24.1%,16.8%,12.1%,12.1%,and 10.1%,respectively;2.NH₃ volatilization is the main way of total nitrogen loss.The lower the C/N ratio,the larger the nitrogen loss caused by NH₃ volatilization to the total nitrogen loss.T1^T5treatments were 40.5%,39.5%,38.6%,34.1%,and 30.9%,respectively;The lower the C/N ratio,the greater the NH₃ volatilization rate and cumulative volatility,the peaks of NH₃ volatilization rates from T1 to T5 were 19.79,11.22,7.95,7.65,and 2.47 mg·h^-1·m^-2,respectively.By the end of composting,The cumulative volatilization of NH₃ from T1^T5 was 141.5,97.2,71.7,71.6 and 54.8 g,respectively.The peak period of NH₃ volatilization is mainly concentrated in the heating period and high temperature period.The volatilization during this period accounts for more than 95%of the total volatilization;The peak of volatilization occurred on the 9th day of composting.3.The accumulation of ammonium nitrogen in the composting process reached the maximum value on the 6th day of composting?P<0.05?,the pH of the reactor increased rapidly,especiallythe pH of T1 and T2 with low C/N ratio reached 8.9 and8.8 at the 6th day of composting,0.8⁰.9 pH units higher than T3^T5,The accumulation of a large amount of ammonium nitrogen not only raised the pH value of the compost,but also caused the NH₃ volatilization directly.At the end of composting,with the volatilization of NH₃,the loss rate of ammonium nitrogen in each treatment was 72.9%,61.2%,54.8%,51.8%and 43.3%;4.More than 90%of the total nitrogen in compost material is organic nitrogen,and its degradation mainly occured 24 days before composting.The degradation rates of organic nitrogen in T1^T5 treatment were 31.8%,24.3%,14.4%,14.0%and 7.0%,respectively.The lower the initial C/N ratio of the heap,the faster the organic nitrogen mineralization;The degradation rate of different organic nitrogen components was different,mainly the degradation of amino acid nitrogen and amide nitrogen,Amino acid nitrogen has the fastest degradation rate,followed by amide nitrogen,of which amino acid nitrogen has the largest contribution to NH₃ volatilization.The results of this test showed that when the initial C/N of the reactor is lower than 25,the rapid degradation of organic nitrogen such as amino acid nitrogen and amide nitrogen in the compost material generates a large amount of ammonium nitrogen,and thus causes the reactor pH to rise rapidly It is the main reason leading to a large amount of NH₃ volatilization and nitrogen loss during the composting process.