Research On The Mineralization Process Of Soil Nitrogen In Coal Mining Subsidence

Coal mining subsidence wetland is formed by artificial mining activities, terrestrial environment change to the aquatic environment in a short period of time, the microbial community structure,species composition and redox conditionsare would be changed after the change, thereby affecting the migration process of elements in soil. This paper analyzes the temporal and spatial distribution of nitrogen element and three-dimensional fluorescence characteristics of dissolved organic matter(DOM) in water and soil in Panbei Mining Subsidence wetland, studied the mineralization process of soil nitrogen under waterlogged incubation, aerobic training, removing DOM culture and different p H conditions, and detecting number and variety of bacteria at different stages under the waterlogged training and aerobic training process. Through the above study, we get the following conclusions:(1)The total nitrogen, nitrate nitrogen and ammonia nitrogen are uniformly spatial distributed in coal mining subsidence water; the nitrogen element content showed obvious seasonal variation. The total nitrogen, ammonium nitrogen and nitrate nitrogen in the surface soil spatial difference. The nitrogen content of soil decreased with time in seasonal water area, while the nitrogen content of soil did not change significantly over time in the nonseasonal water area.(2)DOM in water is evenly distributed; the DOM of wetland water is mainly comprised of fulvic acid and proteins, showed that the subsidence water formed in a short time and less pollution. The soil DOM measured is not uniform, the content of soil DOM increase with the distancein increase from the collapse edge, the DOM of subsidence soil is mainly comprised of ulvic acid and proteins, were not detected with humic acid.(3)In continuously waterlogged incubation experiment, the soil mineral nitrogen content fluctuated with time early, but later stabilized. In continuous aerobic incubation experiment, however, the mineral nitrogen content was lower in the early stage, after 40 days were significantly increased. and the content is higher than that of pre training.The amount of nitrogen mineralization under flooding cultivation was significantly higher than that of aerobic culture,indicating that the soil flooding process is beneficial to soil nitrogen mineralization;The Changes of microbial diversity consistent with the content of mineral nitrogen.Ammonifying bacteria showed a rising trend in flooding early,with the accumulation of mineral nitrogen,the number of ammonifying bacteria was reduce, at the same time,the number of nitrifying bacteria was increase,the bacterial abundance and diversity index reached the maximum value in 20 days;In late culture,due to the continuous flooding makes the soil oxygen content decreased,the number of nitrifying bacteria decreased.Inaerobic process, the number of bacteria increased; The numbers of ammonification bacterial increased first and then decreased with cultured; Nitrifying bacteria showed an overall increasing trend. The number of bacteria increased in incubation, suggested that the incubation could improve soil bacterial activity, promoting the mineralization process.(4)In The condition of removal DOM, the soil mineral nitrogen content fluctuated with time early, but later stabilized The training mode of removal DOM makes the mineral nitrogen content less than that of continuous flooding, especially in the initial stage of culture is more obvious, indicating that DOM plays a more important role in themineralization of soil organic nitrogen.(5)The mineral nitrogen with time variation is similar, both showed a downward trend in volatility under p H=4,p H=7, p H=10 condition.Mineral nitrogen content under p H=7 was higher than that of p H=4,p H=10,which indicated that the neutral environment was suitable for ammonifying microorganisms survival.The p H of Coal mining subsidence soil is 6.6-6.8,which is beneficial for mineralization.