The evaluation and influencing factors of groundwater tri-nitrogen pollution in the Ningdong coal base, exemplified by Meihuajing field

In order to study the large-scale comprehensive mechanized coal mining nitrogen pollution sources and the influence degree, the authors selected the Jurassic coalfield of Yuanyang Lake mining area of Meihuajing well field as the research object. In order to study the three nitrogen pollutants and the effect of large-scale coal mining on groundwater, the authors conducted the sampling investigation of groundwater spatial distribution, physical source and hydrogeological conditions of Ningdong coal base. Some conclusions have been reached:(1) The ranges of three nitrogen pollutants NH⁴⁺ and NO^3- and NO^2- are 0.06~0.12mg/L, 4.67~234mg/L, and < 0.01~2.01mg/L respectively in Meihuajing well field base in Yuanyang Lake mining coal area in the east of Ningxia; compared with the national underground water quality, NO^2- reaches the level of severe or very severe pollution, and is mainly distributed in unconfined aquifer; the level of NO^3- pollution is moderate and mild, and the excessive standard sample points reach 75% in all sample points, and they extend to the confined aquifer. In space, the pollution sample points are present, regardless of the range of mineral rights and out of mineral rights. (2) The NO^3- mg equivalent percentage of some water samples is more than 25%, which affects the chemical type of water. (3)The pollution of NO^3- and NO^2- in coal mine area is related first to abundant material source and second to the influence of coal mining disturbance and hydrogeochemical conditions. The results of the study provide a reference for the prevention and control of groundwater nitrogen pollution in the mining area of large mechanized coal mine.