| As a well-known method to stabilize organic wastes, composting is obtaining more researches since this biological process can convert biodegradable components into nuisance-free, sanitary and humus-like materials which can be used for organic fertilizer. Although many solid wastes are disposed economically by composting, 60 % of the total nitrogen(N) can be reduced from compost causing lower ertilizer efficiency and higher levels of harmful gases, such as nitrous oxide(N 2O) and ammonia(NH3).Denitrification plays a vital role of the cycle of nitrogen during the composting. Under the anaerobic conditions, microorganisms change the NO3- and NH4+ to NO, N2 O and N2 respectively by the enzyme catalytic reduction reaction. What is worse, N2 O can be emitted through both nitrification and denitrification processes as intermediate products and by-products, respectively. A a kind of significant trace gas in the atmosphere, N2 O as a noteworthy global warming potential by absorbing infrared adiation, which is about 298 times that of carbon dioxide according to IPCC. N2 O explains approximately 7.9 % of total anthropoge nic greenhouse gas emissions with concentration of N2 O increasing at a rate of 0.26 % per year. Another impact of N2 O is that it contributes to the depletion of stratospheric ozone layer through reacting with oxygen(O2) to generate nitric oxide(NO).In the present research, we conducted an agricultural waste compost pile under experimental conditions. It can be seen through the determination of physico-chemical parameters during the composting that the thermophilic stage started from the fourth day to the thirteen day and it lasted 10 day, the highest pile temperature is 55.6 oC, it met the requirements of killing pathogenic and making compost rotten. WSC increased slightly from 2226.8 mg kg-1 DW compost sample to 2466.7 mg kg-1 DW compost sample on day 3 and dropped to 1042.7 mg kg-1 DW compost sample at the end of composting. The moisture content during the first 4 days was adjusted to about 60%, then the moisture content during composting began to decrease from 67 to 47%. The p H increased significantly f rom 6.62 to 9.36 during the earlier 9 days, and then decreased to 8.28 gradually in the end of composting. NH4+content rose rapidly during the first 4 days and soared to the peak value of 1211.5 mg kg-1 DW compost sample on day 4. Afterwards, the value beg an to decrease gradually until the end of composting with a level of 395.8 mg kg-1 DW compost sample. NO3- content increased a little in the first 2 days and then decreased sharply to 377.6 mg kg-1 DW compost sample on day 9. Thereafter, the values increased gradually to 953.0 mg kg-1 DW compost sample at the end of composting. The results of quantitative PCR indicated that all the three genes existed in the whole composting, and the higher abundances of the three genes were detected during the cooling and the mature stages while lower abundances during the mesophilic and the thermophilic stages. The average copy numbers were in order of nos Z, nir K, and nir S.In this research, we determined the abundance of denitrifying genes nir K, nir S and nos Z by the method of real-time quantitative PCR and analyzed the relationship between physico-chemical parameters and denitrifying genes by SPSS 11.5. Firstly, we made a correlation analysis between physico-chemical parameters and denitrifying genes, and then we made curve estimations based on regression analysis between denitrifying genes and physico-chemical parameters which shared significant relations with denitrifying genes. The results suggested that the abundance of nir K only shared relationship with pile temperatur e followed by quadratic model; the abundance of nir S shared significant relationships with pile temperature(linear model), NH4+-N(linear model), NO3--N(inverse model) and p H(quadratic model); the abundance of nos Z shared significant relationships with p H(quadratic model) and water soluble carbon(linear model). |
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