Laboratory-determined Phosphorus Flux from Lake Sediments as a Measure of Internal Phosphorus Loading

Abstract

Eutrophication is a water quality issue in lakes worldwide, and there is a critical need to identify and control nutrient sources. Internal phosphorus (P) loading from lake sediments can account for a substantial portion of the total P load in eutrophic, and some mesotrophic, lakes. Laboratory determination of P release rates from sediment cores is one approach for determining the role of internal P loading and guiding management decisions. Two principal alternatives to experimental determination of sediment P release exist for estimating internal load: in situ measurements of changes in hypolimnetic P over time and P mass balance. The experimental approach using laboratory-based sediment incubations to quantify internal P load is a direct method, making it a valuable tool for lake management and restoration.Laboratory incubations of sediment cores can help determine the relative importance of internal vs. external P loads, as well as be used to answer a variety of lake management and research questions. We illustrate the use of sediment core incubations to assess the effectiveness of an aluminum sulfate (alum) treatment for reducing sediment P release. Other research questions that can be investigated using this approach include the effects of sediment resuspension and bioturbation on P release.The approach also has limitations. Assumptions must be made with respect to: extrapolating results from sediment cores to the entire lake; deciding over what time periods to measure nutrient release; and addressing possible core tube artifacts. A comprehensive dissolved oxygen monitoring strategy to assess temporal and spatial redox status in the lake provides greater confidence in annual P loads estimated from sediment core incubations.

Phosphorus speciation, transformation, and preservation in the coastal area of Rushan Bay

“…A conservative DRP release estimate was used to assess the DRP flux contributions from internal water column sources (Ogdahl et al, 2014). The internal DRP loading contribution rate was calculated as follows:…”

Phosphorus Flux across the Sediment-Water Interface in a Drainage Ditch Receiving Water from Livestock Farms in Kasaoka, Japan

“…Loosely-P and Fe-P fractions were the main sources of P released from sediment to overlying water in drainage sediment in Kasaoka [21]. In addition, Fe-P is considered a redox sensitive form, whereas Al-P is redox insensitive and Ca-P is stable in the environment [2]. Accordingly, under anoxic conditions, Fe 3+ is reduced to Fe 2+ as a result of the P release from sediment.…”

“…The concentrations of dissolved reactive phosphorus (DRP) and total phosphorus (TP) in a water body are dependent on internal and external loadings. Internal loading leads to a high P concentration in a water column although external loadings are curtailed [2].…”

“…Phosphorus diffusion can be estimated in situ by measuring the change in P concentration in the water column inside a benthic chamber [1,7,8] or based on the concentration gradient in the pore-water profile according to Fick's first law [5]. The maximum P flux can be measured in the laboratory by a simple regression analysis of the concentration vs. time curve during incubation of the intact sediment-water column [2,4]. It is important to understand how P diffuses across the sediment-water interface and its contribution to downstream aquatic systems.…”

“…It is important to understand how P diffuses across the sediment-water interface and its contribution to downstream aquatic systems. In this respect, there have been numerous studies that measured P flux in lakes [2,4,9,10], in river estuaries [5], and in situ wetland ditches [1]. However, measurement of P flux in drainage ditch sediment during both in situ and sediment-water column incubation has not been documented as an estimation of P internal loading.…”