期刊
WATER RESOURCES RESEARCH
卷 54, 期 9, 页码 5973-5985出版社
AMER GEOPHYSICAL UNION
DOI: 10.1029/2018WR023286
关键词
anthropogenic activities; river water and groundwater interactions; reactive transport; coupled hydrology and biogeochemistry; retardation capacity; hyporheic zone
资金
- National Natural Science Foundation of China [41572228, 41521001, 41330314]
- Guangdong Provincial Key Laboratory of Soil and Groundwater Pollution Control [2017B030301012]
- Fundamental Research Funds for the Central Universities [CUG170410]
- China University of Geosciences (Wuhan)
- U.S. Department of Energy (DOE), Office of Biological and Environmental Research (BER), as part of Subsurface Biogeochemical Research Program's Scientific Focus Area (SFA) at the Pacific Northwest National Laboratory (PNNL)
- Southern University of Science and Technology [G01296001]
Biogeochemical processes in the hyporheic zone (HZ) may retard the contaminants migration from groundwater to the river and vice versa. Anthropogenic activities may further complicate such processes. This study investigated the effects of dam-induced hydrodynamics on biogeochemical transformation of contaminants using Cr as an example in the HZ of the Columbia River at the U.S. Department of Energy's Hanford Site. The flow velocities in the HZ were first simulated using the measured or averaged groundwater level and river stage at hourly, daily, weekly, and monthly time scales. The flow velocities were then incorporated into a reactive transport model with independently characterized biogeochemical reactions and kinetics. Simulation results indicated that hydrodynamics can significantly influence the rate and extent of Cr (VI) biogeochemical transformation, which was mainly controlled by the kinetic reduction of Cr (VI) to sparely soluble Cr (III) by sediment-associated Fe (II) that can be regenerated by microorganisms with organic carbon as electron donor. The frequent flow direction reversals in the HZ induced by dam operations enhanced the rate of microbial consumption of bioavailable OC, which, if there was no organic carbon supply, can eventually terminate the Fe (II) regeneration mechanism and exhaust the HZ's redox capacity in reducing Cr (VI) to Cr (III). This study demonstrated the importance of hydrodynamics on biogeochemical transformation of contaminants in the HZ and of the time scales used in assessing the reactive transport of chemicals and contaminants in the HZ as the net supply of redox sensitive chemicals such as dissolved oxygen into the HZ is a function of the frequency of flow direction reversal.
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