Spatial characteristics and controlling indicators of major hydrochemical ions in rivers within coal-grain composite areas via multivariate statistical and isotope analysis methods

Abstract

The spatial variability of river hydrochemistry in coal-grain composite areas is influenced by natural processes and human activities. However, there is little information thus far on the hydrochemical characteristics of river water and the spatial variability in coal–grain composite areas under the influence of multiple superimposed effects. In this study, river water samples (n = 31) were collected in a coal-grain composite area in the northern plain of Anhui Province (China). The main hydrochemical ions and stable isotopes (δ2H-H2O, δ18O-H2O, δ34S-SO42- and δ18O-SO42-) were then investigated. The objective was to analyze the spatial characteristics and controlling indicators of the main hydrochemical ions via multivariate statistical and isotope analysis methods. The values of δ34S-SO42- and δ18O-SO42- in river water ranged from 7.5 ‰ to 17.5 ‰ and from 4.4 ‰ to 10.7 ‰, respectively. According to the clustering analysis method, the river water samples were divided into two groups. Bayesian mixed model analysis indicated that the sources of SO42- in river water mainly included soil sulfate and mine drainage, with contribution proportions of 74.0 ± 3.1 % and 18.4 ± 4.1 % in River Group I, respectively, and 77.2 ± 3.0 % and 11.1 ± 5.1 % in River Group II, respectively. These results suggested that the controlling indicators of the spatial distribution characteristics of river hydrochemistry were natural processes (water–rock interactions) and human activities (coal mining, manure release and sewage discharge). The results could provide valuable information for regional water resource management, development, and similar coal–grain composite areas elsewhere.