Seasonal Stream Water Chemistry Response To Long-Term Forestry Drainage And Wildfire: A Case Study In A Part Of The Great Vasyugan Mire

Abstract

Recent research suggests that climate change is contributing to rising solute concentrations in streams. This study focuses on assessing the concentrations of major elements, nutrients, and dissolved organic carbon (DOC), and their release through the bog-river system in the taiga zone of Western Siberia. The research was carried out in the northeastern part of the Great Vasyugan Mire (GVM), the largest mire system that impacts the quality of river water in the Ob River basin. By using PCA and cluster analysis, we examined the long-term dynamics of the chemical composition of headwater streams of the GVM affected by drainage and wildfires. Our data from 2015-2022 revealed that the concentrations of Са2+, Mg2+, K+, Na+, and HCO3- in stream water from the drained area of the GVM were, on average, 1.3 times lower than those at the pristine site. Conversely, the  concentrations of NH+4, Fetotal, Cl-, SO42-, NO-3, DOC, and COD were higher, indicating the influence of forestry drainage and the pyrogenic factor. Our findings also demonstrated that the GVM significantly impacts the water chemical composition of small rivers. We observed a close correlation in the concentrations of К+, Na+, Cl-, Fetotal, NH+4, HCO3-, and COD between the GVM and the Gavrilovka River waters. PCA analysis revealed that air temperature influences the concentrations of Са2+, Mg2+, NH4+, NO3-, HCO3-, Fetotal, and DOC in the studied streams, with an inverse correlation with river discharge. The removal of major elements, nutrients, and DOC from the drained area of the GVM was most pronounced in April, being twice as high as in the pristine area. However, the total export from the drainage area of the Gavrilovka in April-September 2022 was 1.3 times lower than in the pristine area, amounting to 8487 kg/km2, with DOC removal at 42%.