Factors influencing release of phosphorus from sediments in a high productive polymictic lake system

Abstract

Phosphorus (P) release rates from bottom sediments are high (20.6 mg/m(2)/day) in Dal Lake (India), a polymictic hyper-eutrophic lake. These gross release rates occur over a period of 72 days during summer only. Likewise, a net internal load of 11.3 tons was obtained from mass balance estimates. Significant proportion i.e. approximately 80% of 287.3 tons/yr of nitrate nitrogen (NO(3)-N) load is either eliminated by denitrification or gets entrapped for a short period in high macrophyte biomass of 3.2 kg/m(2) f.w., which eventually get decomposed and nitrogen (N) is released back. These processes result in low lake water NO(3)-N concentrations which potentially influence sediment phosphorus (P) release. Especially, nitrate nitrogen (NO(3)-N) <500 microg/L in the lake waters were associated with high P concentrations. Phosphorus was also observed to increase significantly in relation to temperature and pH, and it seems likely that release of phosphorus and ammonical nitrogen (NH(4)-N) depend on decomposition of rich reserves of organic matter (893 tons d.w. in superficial 10-cm bottom sediment layer). Lake P concentrations were significantly predicted by a multivariate regression model developed for the lake. This study describes significance of various lake water variables in relation to P-release from bottom sediments.

Internal phosphorus load in a Mexican reservoir: Forecast and validation

“…Under these conditions of Eh below –200 mV and pH approximately 8, Fe probably dissolves as reduced iron (Fe 2+ ), releasing adsorbed P. This may explain the higher IPL‐MB compared with IPL‐Eh values when thermal stratification occurs. Such an increase in the release of P under alkaline conditions has been previously reported, as a result of the exchange with hydroxyl ions of the phosphate adsorbed on Fe(OH) 3 .…”

Phosphorus export across an urban to rural gradient in the Chesapeake Bay watershed

“…The pronounced seasonal changes in SRP concentration in the 2 headwater streams (GFGL and MCDN in Figure 2), with highest concentrations in summer and lowest concentrations in winter, suggest that SRP concentration in these headwater streams may be driven by changes in stream temperature. Other variables that influence SRP concentrations in aquatic ecosystems, including flow conditions, tributary‐by‐tributary “dilution,” biotically mediated changes in pH and dissolved oxygen [ Withers and Jarvie , 2008, and references within; Duan et al , 2010] may also cause such seasonal change in SRP [ James and Barko , 2004; Solim and Wanganeo , 2009]. For example, the relatively high SRP concentrations during summer could be attributed to low flow during this season, an idea supported by the trend of decreasing SRP concentrations with increasing streamflow at the urban sites (Figure 3).…”

“…However, the stimulating effects of warm water temperatures on biotically mediated biogeochemical processes in stream sediments could also be a major driver behind the seasonality observed in the incubation experiments. For example, fast oxidation of organic matter at higher temperatures [ White et al , 1991] could lead to lower dissolved oxygen concentration and formation of anoxic conditions that favor SRP fluxes from sediments [ James and Barko , 2004; Solim and Wanganeo , 2009]. The same biotic and abiotic processes could occur in soils, and soil SRP buffering is also likely important because of the wider distribution of soils than stream sediments.…”

“…Equilibrium phosphate concentrations with soil particles and the solubility of phosphorus minerals (e.g., hydroxylapatite) are temperature dependent [ Barrow , 1979; Prakash et al , 2006]. Temperature also increases the rates of SRP sorption and desorption from particles [ Froelich , 1988] and favors the formation of environmental conditions (e.g., anoxic) at which SRP fluxes from sediments and soils can be enhanced [ House and Denison , 2002; James and Barko , 2004; Solim and Wanganeo , 2009].…”

Effects of pH, Temperature, Dissolved Oxygen, and Flow Rate on Phosphorus Release Processes at the Sediment and Water Interface in Storm Sewer

“…Focusing on the latter topic, a number of studies had paid attention to P release from the sediment to various kinds of receiving natural water bodies such as coastal zones [8], lakes [9], and rivers [10]. Some researches examined P release in urban catchment [11].…”