title: Coupled Nitrification-Denitrification Caused by Suspended Sediment (SPS) in Rivers: Importance of SPS Size and Composition.
abstract: Suspended sediment (SPS) is ubiquitous in rivers, and SPS with different particle sizes and compositions may affect coupled nitrification-denitrification (CND) occurring on SPS significantly. However, there is no related research report. In this work,15N isotope tracer technique was adopted to explore the CND in systems containing SPS (8 g L-1and 1 g L-1) collected from the Yellow River with various particle sizes, including <2, 2-20, 20-50, 50-100, and 100-200 μm. The results showed that the CND occurred on SPS and the CND rate was negatively related to particle size; both nitrification and denitrification rate constants increased with decreasing SPS particle size. For instance, SPS (8 g L-1) with a particle size below 2 μm had the highest15N2emission rate of 1.15 mg-N/(m3·d), which was 2.9 times that of 100-200 μm. This is because SPS with a smaller particle size had a larger specific surface area and a higher organic carbon content, which is beneficial for bacteria growth. Both the nitrifying and denitrifying bacteria population were positively correlated with CND rate (p < 0.05). Different from the15N2production,15N2O emission rate did not decrease with increasing SPS particle size. For the system containing 8 g L-1SPS,15N2O emission rate reached the highest of 1.05 μg-N/(m3·d) in the 50-100 μm SPS system, which was 17.5 times that of 100-200 μm. Similar results could be found from the system with 1 g L-1SPS. This is due to the fact that the oxygen concentration at the SPS-water interface increased with SPS particle size, and the oxygen conditions might be most suitable for the production of N2O in the 50-100 μm system. This study suggests that SPS size and composition play an important role in nitrogen cycle of river systems, especially for the production of N2O.
authors.affiliation: School of Environment, Beijing Normal University , State Key Laboratory of Water Environment Simulation/Key Laboratory of Water and Sediment Sciences of Ministry of Education, Beijing 100875, China.
authors.forename: Xinghui
authors.identifier: 0000-0002-8663-6346
authors.initials: X
authors.lastname: Xia
authors.affiliation: School of Environment, Beijing Normal University , State Key Laboratory of Water Environment Simulation/Key Laboratory of Water and Sediment Sciences of Ministry of Education, Beijing 100875, China.
authors.forename: Zhimei
authors.initials: Z
authors.lastname: Jia
authors.affiliation: School of Environment, Beijing Normal University , State Key Laboratory of Water Environment Simulation/Key Laboratory of Water and Sediment Sciences of Ministry of Education, Beijing 100875, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Liu
authors.affiliation: School of Environment, Beijing Normal University , State Key Laboratory of Water Environment Simulation/Key Laboratory of Water and Sediment Sciences of Ministry of Education, Beijing 100875, China.
authors.forename: Sibo
authors.initials: S
authors.lastname: Zhang
authors.affiliation: School of Environment, Beijing Normal University , State Key Laboratory of Water Environment Simulation/Key Laboratory of Water and Sediment Sciences of Ministry of Education, Beijing 100875, China.
authors.forename: Liwei
authors.initials: L
authors.lastname: Zhang
mesh_terms: D001419:Bacteria; D058440:Denitrification; D058465:Nitrification; D009584:Nitrogen; D009609:Nitrous Oxide; D010316:Particle Size; D045483:Rivers
chemical_list: D009609:Nitrous Oxide; D009584:Nitrogen