Sediment Depth Attenuation of Biogenic Phosphorus Compounds Measured by ³¹P NMR

Abstract

Being a major cause of eutrophication and subsequent loss of water quality, the turnover of phosphorus (P) in lake sediments is in need of deeper understanding. A major part of the flux of P to eutrophic lake sediments is organically bound or of biogenic origin. This P is incorporated in a poorly described mixture of autochthonous and allochthonous sediment and forms the primary storage of P available for recycling to the water column, thus regulating lake trophic status. To identify and quantify biogenic sediment P and assess its lability, we analyzed sediment cores from Lake Erken, Sweden, using traditional P fractionation, and in parallel, NaOH extracts were analyzed using 31P NMR. The surface sediments contain orthophosphates (ortho-P) and pyrophosphates (pyro-P), as well as phosphate mono- and diesters. The first group of compounds to disappear with increased sediment depth is pyrophosphate, followed by a steady decline of the different ester compounds. Estimated half-life times of these compound groups are about 10 yr for pyrophosphate and 2 decades for mono- and diesters. Probably, these compounds will be mineralized to ortho-P and is thus potentially available for recycling to the water column, supporting further growth of phytoplankton. In conclusion, 31P NMR is a useful tool to asses the bioavailability of certain P compound groups, and the combination with traditional fractionation techniques makes quantification possible.

Characteristics of phosphorus components in the sediments of main rivers into the Bohai Sea

“…OP in the sediment may be more stable than ortho-P. The half-lives of mono-P, diesters-P, and pyro-P are 23 y, 21 y, and 13 y, respectively in Lake Erken in Sweden (Ahlgren et al, 2005); and the half-lives of various OP forms, namely mono-P, lipid-P, DNA-P, and pyro-P, are 27 y, 14 y, 12 y, and 3 y, respectively in Taihu Lake in China (Ding et al, 2013). The proportion of mono-P was higher in the Liao River and Luan River, and lower in the Yongdingxin River, and it indicated that the phosphorus composition in the Liao River were more stable than in the Yongdingxin River and the Ziya River.…”

Phosphorus speciation of sediments from lakes of different tropic status in Eastern China

“…Conditions may be hypoxic at the sediment-water interface, so mono-P in lake sediments may be a key source of phosphate during algal bloom periods. DNA-P and lipid-P were the main components of diester-P, which represents labile P in the sediments and has a half-life of 21 years (Cade-Menun 2005; Ahlgren et al 2005). The significant positive relationship between pyro-P, mono-P, and diester-P indicates that pyro-P might be released from mono-P and diester-P under specific physicochemical conditions.…”

“…Biogenic-P in the sediment may be more stable than ortho-P. The half-lives of mono-P, diester-P, and pyro-P are 23, 21, and 13 years, respectively in Lake Erken in Sweden (Ahlgren et al 2005); and the half-lives of various biogenic-P forms, namely mono-P, lipid-P, DNA-P, and pyro-P, are 27, 14, 12, and 3 years, respectively, in Taihu Lake in China (Ding et al 2013). From Fig.…”

The Chemical Nature of Phosphorus in Subtropical Lake Sediments

“…Recent studies have determined the chemical nature of sediment organic P by alkaline extraction and solution 31 P nuclear magnetic resonance (NMR) spectroscopy, which classifies organic P into a series of compounds and functional groups, including phosphomonoesters, phosphodiesters (e.g., DNA, lipids), and phosphonates (e.g., Carman et al 2002;Ahlgren et al 2005;Reitzel et al 2007;Zhu et al 2013). The technique also identifies inorganic phosphates, including orthophosphate, pyrophosphate, and polyphosphate (e.g., Hupfer et al 2004).…”

“…Moreover, the relative importance of the various P forms in sediments will depend on sediment composition, sedimentation rate, diagenesis, and physicochemical conditions (Lopez and Morgui 1993;Gonsiorczyk et al 1998). Of significance is the fact that differences in the abundance of P compounds with depth in lake sediments can provide information on mineralization rates and the contribution of the various compounds to the internal P load (Ahlgren et al 2005;Reitzel et al 2007).…”