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Phosphorus adsorption and sedimentation by suspended sediments from Zhushan Bay, Taihu Lake

Author:
Wang, Peifang, Hu, Bin, Wang, Chao, Lei, Yang
Source:
Environmental science and pollution research international 2015 v.22 no.9 pp. 6559-6569
ISSN:
0944-1344
Subject:
adsorption, aluminum, ammonium oxalate, dissolved oxygen, fractionation, iron, iron oxides, lakes, oxides, particulates, phosphorus, sediments, suspended sediment, water quality
Abstract:
The process of phosphorus (P) transformation in particulate matter during sediment resuspension and sedimentation was studied. The P-binding forms in resuspended particles (RP) and settled particles (SP) were analyzed by sequential fractionation (modified Psenner method) and an extended extraction with ammonium oxalate. Water quality data and P fractions were used to estimate P release and uptake by the resuspended and settling sediment particles. Results of 8-h resuspension experiments showed increases of dissolved oxygen, pH, total phosphorus, and particulate phosphorus in overlying water, but no change in soluble reactive phosphorus (SRP). P fractions extracted with common sequential fractionation showed that the increase of total P in RP was mainly due to increases of redox-sensitive bound P BD (BD-SRP) and P bound to Al and Fe oxides (NaOH-SRP) (36–52 % and 30–36 % of total increased P, respectively). Comparisons between two sequential fractionations indicated that inorganic P extracted with ammonium oxalate consisted of P bound to amorphous Fe/Al oxy-hydroxides and partially of carbonate-bound P (HCl-SRP) and that increased P in RP was mainly caused by increases in P bound to amorphous oxides. It is concluded that the formation of amorphous oxides and subsequent adsorption of P lead to the increase of P in RP. However, P adsorbed by amorphous oxy-hydroxides in RP is unstable and may be released under sedimentation conditions. Meanwhile, increases in HCl-SRP, refractory P, and crystalline Fe-P were found in SP compared with RP. NaOH-SRP in SP increased gradually under sedimentation conditions. It is suggested that, during sedimentation, mobile P can be transformed to non-mobile P forms that provide long-term P retention. The findings contribute to the understanding of P cycling in particulate matter during sediment resuspension and sedimentation.
Agid:
1244117