Species and environmental geochemistry characteristics of organic phosphorus in sediments of a riverine wetland measured by 31P-NMR spectroscopy

Abstract

Phosphorus species in sediment cores obtained from a representative riverine wetland were determined and organic phosphorus was distinguished with phosphorus-31 nuclear magnetic resonance (31P-NMR) spectroscopy. The concentrations and distributions of orthophosphate, orthophosphate monoester, orthophosphate diester and pyrophosphate were subsequently characterized. Total phosphorus, total inorganic phosphorus and total organic phosphorus decreased from the top to bottom layer of sediment on the whole. Organic phosphorus was primarily detected in surface sediment layers and scarce toward the bottom, and orthophosphate as a proportion of total organic phosphorus was much higher than other species which was attributed to mineralization as a result of high dissolved oxygen (DO) concentrations. Furthermore, significant positive correlation was observed between alkaline phosphatase activity (APA) and phosphorus fractions suggesting that APA could hydrolyze organic phosphorus into inorganic phosphorus even at high phosphorus concentrations. Significant correlation was also observed between Fe/Al and phosphorus species showed organic phosphorus adsorbed to Fe/Al might be released from sediments and transformed to inorganic phosphorus.