[Effects of water content on redox potential and carbon mineralization of wetland sediments].
To better understand the effect of soil water contents on redox potential (Eh), and their impacts on C mineralization in natural wetland, sediment samples from 3 types of wetlands (fen, humus marsh and marshy meadow) in the San-jiang Plate region of North China were incubated (25 degrees C) for 155 d under a range of reducing and oxidizing conditions by controlling water contents (varied from 24% to 232% of water holding capacity) (WHC). CO2-C evolved during incubation was measured at different time intervals. Results showed that Eh of sediments decreased significantly as water content increased from 24% WHC (lighted moisturized) to about 100% WHC, then decreased slightly as water content increased further to a level of submersed (about 2 cm water-depths). The accumulative amount of CO2-C evolved from the sediments indicated that the optimum water contents for mineralization of organic C are 32%, 48% and 76%-100% WHC for sediments of fen, humus marsh, and marshy meadow, respectively. The relationship between mineralization rates and redox potentials (Eh) were well fitted with second order parabola equations (p < 0.05). Mineralization rates and accumulative amount of organic C displayed a positive correlation with Eh up to 300 mV. However, a significant negative correlation was observed when Eh increased above 300 mV. Results demonstrated that low redox potential is the controlling factor of carbon accumulation of wetland in San-jiang Plate region.
Forestry College of Guangxi University, Nanning 530004, China. yanggr@gxu.edu.cn
Gai-ren
GR
Yang
Cheng-li
CL
Tong
He-ai
HA
Xiao
Jin-shui
JS
Wu
D001673:Biodegradation, Environmental; D002244:Carbon / Q000032:analysis*; D002681:China; D004579:Electron Transport; D019015:Geologic Sediments; D006812:Humic Substances / Q000032:analysis; D009930:Organic Chemicals / Q000032:analysis*; D010084:Oxidation-Reduction; D006109:Poaceae / Q000254:growth & development; D014867:Water / Q000032:analysis*; D053833:Wetlands
D006812:Humic Substances; D009930:Organic Chemicals; D014867:Water; D002244:Carbon