Application of non-parametric Mann-Kendall and innovative trend method analysis to groundwater quality parameters variation: a case study from aquifers in Xinsankuang Coal mine
The change of groundwater quality is one of the restricting factors affecting mining area ecological environment, and of coal mine safety in production. It is the first priority to correctly understand the trend of water quality change. In this paper, based on the data of measured water quality parameters, pH, COD, Na++K+, Ca2+, Mg2+, Cl-, SO42- and HCO-3, for comparison purposes, Mann-Kendall test method and a new trend method recently proposed by Sen called Innovative Trend Analysis were used to investigate the evolution rules with the time of the water parameters at six different aquifers (sandstone water, Yeqing limestone water, Shanqing limestone water, Fuqing limestone water, Daqing limestone water and Ordovician limestone water) in New Three coal mine. A quantitative measurement of a trend for ITA was adopted, moreover, different ITA indicators were used for different variation ranges. By comparison, the results of the two methods are in good agreement. Results show that the quantitative ITA has more advantages than the MK detection method, and can graphically represent the analysis result, and can better analyze the water quality parameters by dividing the water quality parameter values into low, medium and high levels.Among the eight water quality parameters, Ca2+ and Mg2+ have more significant trends than other water parameters.Among the six aquifers, it is seen that while the Cl- in Daqing limestone water have a decreasing trend for low and medium values, the high values has an increasing trend. For the seam roof sandrock aquifer and floor limestone water, most water quality parameters show significant decreasing trend, and salinity has the same trend.