Speciation of organic phosphorus in a sediment profile of Lake Taihu. II. Molecular species and their depth attenuation.
The understanding of organic phosphorus (P) dynamics in sediments requires information on their species at the molecular level, but such information in sediment profiles is scarce. A sediment profile was selected from a large eutrophic lake, Lake Taihu (China), and organic P species in the sediments were detected using solution phosphorus-31 nuclear magnetic resonance spectroscopy (31P NMR) following extraction of the sediments with a mixture of 0.25 mol/L NaOH and 50 mmol/L EDTA (NaOH-EDTA) solution. The results showed that P in the NaOH-EDTA extracts was mainly composed of orthophosphate, orthophosphate monoesters, phospholipids, DNA, and pyrophosphate. Concentrations of the major organic P compound groups and pyrophosphate showed a decreasing trend with the increase of depth. Their half-life times varied from 3 to 27 years, following the order of orthophosphate monoesters > phospholipids > or = DNA > pyrophosphate. Principal component analysis revealed that the detected organic P species had binding phases similar to those of humic acid-associated organic P (NaOH-NRP(HA)), a labile organic P pool that tends to transform to recalcitrant organic P pools as the early diagenetic processes proceed. This demonstrated that the depth attenuation of the organic P species could be partly attributed to their increasing immobilization by the sediment solids, while their degradation rates should be significantly lower than what were suggested in previous studies.
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China. smding@niglas.ac.cn
Shiming
S
Ding
Xu
X
Di
Xiuling
X
Bai
Shuchun
S
Yao
Chengxin
C
Fan
Chaosheng
C
Zhang
D002681:China; D004492:Edetic Acid / Q000737:chemistry; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000032:analysis* / Q000737:chemistry; D060106:Lakes / Q000032:analysis; D009682:Magnetic Resonance Spectroscopy; D009943:Organophosphorus Compounds / Q000032:analysis* / Q000737:chemistry; D010758:Phosphorus / Q000032:analysis* / Q000737:chemistry; D010759:Phosphorus Isotopes; D012972:Sodium Hydroxide / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry
D009943:Organophosphorus Compounds; D010759:Phosphorus Isotopes; D014874:Water Pollutants, Chemical; D010758:Phosphorus; D012972:Sodium Hydroxide; D004492:Edetic Acid