Impact of phosphate mining and separation of mined materials on the hydrology and water environment of the Huangbai River basin, China

•Study of impact of phosphate mining on hydrology and water environment.•Large-scale phosphate mining (PM) reduced runoff and runoff peaks.•Pollutants of TN, SS, and TP increased with the mining scale.•PM reduced the amount of background NH4+ and TN loads into rivers.•Soluble P from dissolution of apatite is of great environmental importance.

The objective of this study was to investigate the influence of large-scale phosphate mining (PM) on hydrology and water quality in the Huangbai River basin, China. Rainfall and runoff data were used to analyze hydrological changes of the basin before (from 1978 to 2002) and during (from 2003 to 2014) the PM period. From 2009 to 2014, flow rate and concentrations of ammonia nitrogen (NH4+), nitrate (NO3−), fluoride (F−), suspended solids (SS), total nitrogen (TN), soluble phosphorus (SP), and total phosphorus (TP) were measured at the outfalls of PM as well as at outlets of sub-basins with and without PM practices. Results showed that the PM activities generally reduced runoff (i.e., the runoff coefficient and runoff peak). The sequential Mann Kendall test revealed a decrease trend of runoff during wet seasons after 2008 in the PM regions. For a mining scale of one unit of PM productivity (i.e., 108 kg phosphate ore per year or 2.74 × 105 kg d− 1), TN, SS, and TP of 0.633, 1.46 to 5.22, and 0.218 to 0.554 kg d− 1 were generated, respectively. The NH4+ and TN loads in the sub-basins with PM were significantly higher than these in the sub-basins without PM; however, the NH4+ and TN loads that discharged into rivers from the background non-point sources discharged were less in the sub-basins with PM than those without PM. The result was attributed to the reduction of runoff volume by PM. The annual mean concentrations of TN in reservoir water increased with the scales of PM, whereas the mean concentrations of SP were low. Nevertheless, the SP concentrations in the reservoirs greatly increased after 2012, mainly related to the dissolution of apatite in the sediment. The information from this study should improve the understanding of changes in hydrology and water quality in regions with large-scale PM.

Graphical abstractIn this study, we investigated the influence of large-scale phosphate mining (PM) on hydrology and water quality in the Huangbai River basin, China. Results showed that the PM activities generally reduced runoff coefficient and runoff peak. Total nitrogen (TN), soluble phosphorus (SP), and total phosphorus increased with the mining scale. Ammonia nitrogen (NH4+) and TN loads were significantly higher in the sub-basins with PM than without PM. The yearly mean TN concentrations in the reservoirs increased with the PM scales. The SP concentrations in the reservoirs greatly increased during the later stage of PM, mainly attributable to the dissolution of apatite in the sediment.Download high-res image (217KB)Download full-size image