title: Effect of Water Chemistry and Hydrodynamics on Nitrogen Transformation Activity and Microbial Community Functional Potential in Hyporheic Zone Sediment Columns.
abstract: Hyporheic zones (HZ) are active biogeochemical regions where groundwater and surface water mix. N transformations in HZ sediments were investigated in columns with a focus on understanding how the dynamic changes in groundwater and surface water mixing affect microbial community and its biogeochemical function with respect to N transformations. The results indicated that denitrification, DNRA, and nitrification rates and products changed quickly in response to changes in water and sediment chemistry, fluid residence time, and groundwater-surface water exchange. These changes were accompanied by the zonation of denitrification functional genes along a 30 cm advective flow path after a total of 6 days' elution of synthetic groundwater with fluid residence time >9.8 h. The shift of microbial functional potential toward denitrification was correlated with rapid NO3-reduction collectively affected by NO3-concentration and fluid residence time, and was resistant to short-term groundwater-surface water exchange on a daily basis. The results implied that variations in microbial functional potential and associated biogeochemical reactions in the HZ may occur at space scales where steep concentration gradients present along the flow path and the variations would respond to dynamic HZ water exchange over different time periods common to natural and managed riverine systems.
authors.affiliation: Pacific Northwest National Laboratory , Richland, Washington 99354, United States.|School of Earth Sciences and Engineering, Nanjing University , Nanjing, Jiangsu 210023, China.
authors.forename: Yuanyuan
authors.identifier: http://orcid.org/0000-0001-6076-9733
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Pacific Northwest National Laboratory , Richland, Washington 99354, United States.|School of Environmental Science and Engineering, Southern University of Science and Technology , Shenzhen, Guangzhou 518055, China.
authors.forename: Chongxuan
authors.identifier: http://orcid.org/0000-0002-7403-6001
authors.initials: C
authors.lastname: Liu
authors.affiliation: Pacific Northwest National Laboratory , Richland, Washington 99354, United States.
authors.forename: William C
authors.initials: WC
authors.lastname: Nelson
authors.affiliation: Pacific Northwest National Laboratory , Richland, Washington 99354, United States.|School of Environmental Studies, China University of Geosciences , Wuhan, Hubei 430074, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Shi
authors.affiliation: Pacific Northwest National Laboratory , Richland, Washington 99354, United States.|School of Environmental Studies, China University of Geosciences , Wuhan, Hubei 430074, China.
authors.forename: Fen
authors.initials: F
authors.lastname: Xu
authors.affiliation: Pacific Northwest National Laboratory , Richland, Washington 99354, United States.|School of Environmental Studies, China University of Geosciences , Wuhan, Hubei 430074, China.
authors.forename: Yunde
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Pacific Northwest National Laboratory , Richland, Washington 99354, United States.|Institute of Hydraulic and Environmental Engineering, Zhejiang University of Water Resources and Electric Power , Hangzhou, Zhejiang 310018, China.
authors.forename: Ailan
authors.initials: A
authors.lastname: Yan
authors.affiliation: Pacific Northwest National Laboratory , Richland, Washington 99354, United States.
authors.forename: Lirong
authors.initials: L
authors.lastname: Zhong
authors.affiliation: Pacific Northwest National Laboratory , Richland, Washington 99354, United States.
authors.forename: Christopher
authors.identifier: http://orcid.org/0000-0002-9932-3234
authors.initials: C
authors.lastname: Thompson
authors.affiliation: Pacific Northwest National Laboratory , Richland, Washington 99354, United States.
authors.forename: James K
authors.initials: JK
authors.lastname: Fredrickson
authors.affiliation: Pacific Northwest National Laboratory , Richland, Washington 99354, United States.
authors.forename: John M
authors.initials: JM
authors.lastname: Zachara
mesh_terms: D058440:Denitrification; D060587:Groundwater; D057446:Hydrodynamics; D009584:Nitrogen; D014867:Water
chemical_list: D014867:Water; D009584:Nitrogen