Effect of freezing/thawing on microbial transformation of humic substances during groundwater-river water interaction
L. M. Kondratyeva, D. V. Andreeva
Khabarovsk Federal Research Center of the Far Eastern Branch of the Russian Academy of Sciences, Institute of Water and Ecology Problems, Khabarovsk, Russia
Keywords: microbial communities, groundwater, freezing/thawing, humic substances, river bank filtration
Abstract
The paper presents the results of the study of the role of environmental factors (abiotic and microbiological) in the formation of groundwater quality in the river bank filtration zone under cyclic freezing/thawing (CFT). Groundwater samples from the Tunguska field (Priamurye) taken in the fall period from different aquifer depths from wells located at different distances from the river bank filtration zone were used. CFT was performed in vitro in the presence of different carbon sources at two temperatures: slow thawing from -18 °C to +4 °C; rapid thawing from -18 °С to +23 °С. The activity of microbial communities (MC) from groundwater and river water after CFT was confirmed by their ability cultured on a readily available carbon source (peptone) and hard-to-mineralize sodium humate (HNa), as well as under conditions of their co-metabolism. Maximum activity after CFT at a thawing temperature of 4 °С in the presence of HNa was shown by MC from a depth of 41 m from boreholes 1500 m away from the shore. At a thawing temperature of 23 °С, microorganisms from river and groundwater from wells close to the shore were highly active regardless of the composition of carbon sources during the CFT period. MC growth activity from offshore wells at 23 °С thawing temperature was dependent on the depth of water sampling and the presence of readily available co-substrate. It was shown for the first time that after CFT, thawing temperature influenced the changes in the spectral characteristics of humic substances as a result of their microbial transformation
|
