[Characteristics of sediments and pore water in Lake Nansi wetland].
In order to investigate the influence of sediment physical and chemical characteristics on the vertical distribution of NH4+, PO4(3-) and NO3(-) and their diffusive fluxes at sediment-water surface, pore water equilibrators (Peeper) were employed to obtain multiple pore water profiles from reed and bulrush sediments in Lake Nansihu wetland. The results showed that sediment properties in the planted reed and bulrush fields, i.e. water content, porosity, KCl-extractable NH4+ and NO3(-) were generally greater than those in seldom vegetation, and the porosity in 2-5 cm depth subsurface sediments increased by 57.5%, 34.6%, respectively. Nutrient profiles of NH4+ and PO4(3-) at sediment-water interface exhibited a nearly exponential increase with increasing depth including a concentration maximum at a 8 cm depth, where there was a spike in the NH4+ and PO4(3-) concentration. The diffusive flux (Jx) across the sediment-water interface could be calculated from Fick's first law. The flux calculations showed reed could effectively decreased NH4+ diffusive flux, and the NH4+ diffusive flux, the maximum flux 3.57-4.48 mg/(m2 x d) in reed field, was nearly three times greater than the minimum flux 0.90-1.24 mg/(m2 x d) in seldom vegetation. However, there was a narrow PO4(3-) flux range from 0.02 to 0.04 mg/(m2 x d) in three fields while NO3(-) concentration gradient showed an opposite pattern and diffusive flux occurred in one direction from the overlying bottom water to the sediment pore water. The correlative results suggested that extractable nutrient contents in sediments correlated with pore water content, therefore, controlling extractable nutrient contents appeared to a viable measure to avoid nutrient recontamination to overlying water in wetlands.
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China. guxiaozhi@163.com
Xiao-zhi
XZ
Gu
Lei
L
Zhang
Xiang
X
Bo
Cheng-xin
CX
Fan
D002681:China; D004784:Environmental Monitoring / Q000379:methods; D019015:Geologic Sediments / Q000737:chemistry*; D010758:Phosphorus / Q000032:analysis; D018521:Plant Physiological Phenomena; D010944:Plants / Q000378:metabolism*; D016062:Porosity; D000644:Quaternary Ammonium Compounds / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000032:analysis*; D053833:Wetlands
D000644:Quaternary Ammonium Compounds; D014874:Water Pollutants, Chemical; D010758:Phosphorus