Study On The Forms And Release Feature Of Nitrogen And Phosphorus In The Sediment Of Coal Mine Subsided Water

Through the research on forms of nitrogen phosphorus in the sediment of Panyi coal mine subsided water, this article firstly analyzed the forms and components of nitrogen and phosphorus in the sediment, and also their space distribution features. Then, this article explored related factors of nitrogen and phosphorus forms, through the study of the correlation among the different forms of nitrogen or phosphorus, the correlation between forms of nitrogen or phosphorus and the organic matter, the correlation between forms of nitrogen or phosphorus and the quick-acting potassium, as well as the correlation between forms of nitrogen or phosphorus and indexes of the overlying water. Furthermore, using the core simulation experiment, this article simulated the release features of nitrogen and phosphorus in the sediment under different pH value conditions. Results show that as follows:(1)The average concentrations of total nitrogen (TN) in sediments was961.35mg/kg, in which the average concentrations of organic nitrogen (ON), ammonia nitrogen (NH4+-N), nitrate nitrogen (N03--N), and nitrite nitrogen (NO2-N), respectively were877.64mg/kg,78.89mg/kg,4.53mg/kg,0.29mg/kg. Nitrogen compounds in the sediments were dominated by organic nitrogen, which was84.65%-96.69%among nitrogen composition. The proportion of nitrogen forms in total nitrogen was in the following order:organic nitrogen> ammonia nitrogen> nitrate nitrogen> nitrite nitrogen.The mean levels of total phosphorus (TP) in sediments was275.23mg/kg, in which the mean levels of aluminum-bound phosphate (Al-P), iron-bound phosphate (Fe-P), calcium-bound phosphate (Ca-P) and closed-bound phosphate(O-P), respectively were50.29mg/kg,40.60mg/kg,83.48mg/kg,23.44mg/kg. Phosphorus compounds in the sediments were dominated by inorganic phosphorus, which was46.79%～85.41%among phosphorus composition. While organic phosphorus (OP) was14.59%-53.21%among phosphorus composition. The proportion of phosphorus forms in total phosphorus was in the following order:Ca-P> OP> Al-P> Fe-P> O-P.(2) In different sedimentary layers, the planimetric distribution feature of nitrogen forms and phosphorus forms in the sediment were varied. In0～10cm sedimentary depth, the vertical distribution characteristics of TN, ON, NH4+-N, TP and Al-P, showed a "declining" tendency from the surface to deep level, while the vertical distribution of NO3--N, NO2--N, Fe-P, Ca-P and O-P did not take on obvious regularity.(3) The correlations between nitrogen or phosphorus forms in the sediment were apparent; Moreover, in different sedimentary depths, their correlative strength was diverse. The correlations between TN, NH4+-N and ON were significant positive. The correlations between NO2--N and TN, between NO2--N and NH4+-N, between NO2--N and ON were negative. But the correlations between N03--N and TN, between N03--N and NH4+-N, between N03--N and ON, between N03--N and N02--N were weak. The correlations between TP and Al-P, between TP and Fe-P, between TP and Ca-P showed significant positive correlation, while it was weaker in the relationship between TP and O-P. In addition to the obvious relationship between Al-P and Fe-P, the correlations between other forms of inorganic phosphorus were weak.(4) The correlations between the organic matter and nitrogen forms in the sediment were apparent, while it was not obvious between the organic matter and phosphorus forms; Moreover, in different sedimentary depths, their correlative strength was diverse. Among them, the organic matter and TN, ON, NH4+-N all showed a very significant positive correlation. The organic matter and TP, Al-P, Fe-P all showed positive correlation. But the correlations between the organic matter and NO2-N, N03--N, Ca-P, O-P were weak.(5) The quick-acting potassium and nitrogen or phosphorus forms in the sediment had some correlation, but not obvious; Moreover, in different sedimentary depths, their correlative strength was diverse. Among them, the quick-acting potassium and TN, ON, NH4+-N, TP, Al-P, Fe-P all showed positive correlation. But the correlations between the quick-acting potassium and NO2--N, NO3--N, Ca-P, O-P were weak.(6) The forms of nitrogen or phosphorus in the sediment and indexes of the overlying water had certain relevance, and some was apparent. For example, the total hardness in water presented significant negative correlation with TN and NH4+-N in the sediment. The total nitrogen in water showed very significant positive correlation with NO3--N in the sediment. The total phosphorus in water rendered significant negative correlation with Fe-P in the sediment; and rendered very significant positive correlation with Ca-P in the sediment.(7) Under different pH value conditions, the releasing contents and rate of ammonia nitrogen and the total phosphorus were obviously different. Studies showed that, under different pH values, the releasing strength of nitrogen was in the following order: alkaline> neutral> weakly acidic> strong acid, and the releasing strength of phosphorus was in the following order:alkaline> acid> neutral.The study on the forms and release feature of nitrogen and phosphorus in the sediment of coal mine subsided water, contributes to the grasp of pollution characteristics of nitrogen and phosphorus in sediments. Thereby assessing the risk of nitrogen and phosphorus release in sediments, it has vital significance to the prevention and control of internal pollution.