Grain size distribution effects on phosphate sorption by fluvial sediment: implications for modelling sediment-phosphate transport

Stone, M.; Mulamoottil, George; Logan, L.

doi:10.1080/02626669509491391

Cited by 16 publications

(8 citation statements)

References 30 publications

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“…In theory, runoff‐derived contaminant yields should be greater in smaller streams, with a greater proportion of flow as surface runoff than larger streams. However, this does not take into account likely interactions between REC classes and scale, nor the transport of contaminants in fine particles or flocs that are unlikely to settle out under stable flows in larger streams or rivers (Droppo and Ongley, 1994; Stone et al, 1995). For example, higher‐order streams tend to have adjacent land that is characterized by lowland topography, which supports more intensive (e.g., pastoral) and diverse land covers than upland catchments (Dodds and Oakes, 2008).…”

Section: Discussionmentioning

confidence: 99%

Assessing the Yield and Load of Contaminants with Stream Order: Would Policy Requiring Livestock to Be Fenced Out of High‐Order Streams Decrease Catchment Contaminant Loads?

McDowell

Cox

Snelder³

2017

J of Env Quality

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Catchment contaminant loads vary with stream order as catchment characteristics influence inputs and in-stream processing. However, the relative influence and policy significance of these characteristics across a number of contaminants and at a national scale is unclear. We modeled the significance of catchment characteristics (e.g., climate, topography, geology, land cover), as captured by a national-scale River Environment Classification (REC) system, and stream order in the estimation of contaminant yields. We used this model to test if potential regulation in New Zealand requiring livestock to be fenced off from large (high)-order streams would substantially decrease catchment contaminant loads. Concentration and flow data for 1998 to 2009 were used to calculate catchment load and yields of nitrogen (N) and phosphorus (P) species, suspended sediment, and Escherichia coli at 728 water quality monitoring sites. On average, the yields of all contaminants increased with increasing stream order in catchments dominated by agriculture (generally lowland and pastoral REC land cover classes). Loads from low-order small streams (<1 m wide, 30 cm deep, and in flat catchments dominated by pasture) exempt from potential fencing regulations accounted for an average of 77% of the national load (varying from 73% for total N to 84% for dissolved reactive P). This means that to substantially reduce contaminant losses, other mitigations should be investigated in small streams, particularly where fencing of larger streams has low efficacy. ) to individual farms. To help meet these limits, regulators and industry promote farm-scale mitigation strategies that target areas of the farm with the greatest yield (Doody et al., 2012;McDowell et al., 2016a). However, contaminant loads and yields have been shown to vary with increasing catchment and stream size, increasing or decreasing from source to the site of impact downstream depending on flow-paths and associated processes (Bricker et al., 2014). A systematic methodology that describes contaminant losses from headwaters to the catchment outlet is lacking but is important to help policymakers and land managers decide where best to mitigate contaminant inputs or impacts within a catchment (Biggs et al., 2017;Meals, 1996).Stream orders (Horton-Strahler classification) have been used to characterize stream size and catchment area (Hughes et al., 2011) and to explain variation in contaminant concentrations, loads, and yields (Wigington et al., 1998). When focusing on contaminant concentrations, an almost equal number of studies have found no effect of stream order as those that have. The presence of a stream order effect may be caused by the examination of the effect of stream order in regions where all other significant factors such as land cover are kept equal (Turner et al., 2015). In contrast, studies that show no effect of stream order on contaminant concentrations, loads, and yields often examine one or two stream characteristics, such as stream size, but fail to take into...

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Section: Discussionmentioning

confidence: 99%

Assessing the Yield and Load of Contaminants with Stream Order: Would Policy Requiring Livestock to Be Fenced Out of High‐Order Streams Decrease Catchment Contaminant Loads?

McDowell

Cox

Snelder³

2017

J of Env Quality

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“…The supply of P has been characterized as a function of sediment size and sediment composition. For instance, although coarser sediments may not contain as much P as fine sediments, under oxic conditions, they are thought to release more P per unit mass into the water column due to a combination of lower sorption and easier exchange with interstitial water (Stone et al 1995). The amount of P available for exchange is influenced by sediment composition, which is influenced by floods that can remove or introduce new sediment of different soil types and land use (Palmer-Felgate et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Likely controls on dissolved reactive phosphorus concentrations in baseflow of an agricultural stream

2020

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Purpose High baseflow phosphorus (P) concentrations increase the likelihood of periphyton blooms. Several physical and chemical factors can control baseflow P concentrations such as hydraulic exchange with groundwater, particle size-sorting, redox chemistry and different sediment sources. We hypothesized that of these sources, anoxic sediments would allow P-rich groundwater to influence baseflow P concentrations the most and that the measurement of the equilibrium P concentration (EPC 0) of sediments under oxic conditions would not predict P release in anaerobic sediment or baseflow P concentrations. Materials and methods At four locations along an agricultural stream, we measured dissolved reactive P (DRP), pH, iron, manganese, sulphate, nitrate and dissolved oxygen in streamflow and hyporheic water at 0-200, 200-400 and 400-800 mm depths and P fractions and EPC 0 in sediment samples from the 0-200, 200-400 and 400-800 mm depths. Results and discussion Concentrations of DRP in streamflow and shallow hyporheic zone water increased downstream and were mirrored by concentrations in shallow sediment, EPC 0 measurements of oxic sediments and deeper hyporheic waters. Groundwater samples and the EPC 0 in deeper sediments did not show a pattern or residence time consistent with the supply of P to baseflow despite deeper sediment being anoxic and less likely to sorb upwelling P. There was also no change in pH or particle size downstream ruling out the degassing of groundwater or sediment size-sorting as an influence. However, the composition of sediment and underlying lithology of the catchment pointed to sediment downstream that was different to upstream sediment in that it could store and release more P. Conclusions Given the strong influence of sediment source on baseflow P concentrations, efforts to decrease the likelihood of periphyton blooms under baseflow should focus on reducing the erosion of P-rich sediment. Furthermore, the presence of oxic conditions in surface sediment meant that there was a relationship between EPC 0 and hyporheic water P concentrations. However, mixed oxic/anoxic conditions in deeper layer may require EPC 0 , or release rates, to be measured under reducing conditions.

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“…When the bed shear stress is much greater than the critical shear stress for deposition (for which τ o /τ cd > 12) no deposition occurs but when the critical shear stress is greater than the bed shear stress all the sediment is deposited. When the ratio of τ o to τ cd is between 1 and 12, part of the suspended sediment is deposited [85]. The critical shear stress for deposition is related to the grain size of the material in suspension.…”

Section: Prediction Of Sediment Depositionmentioning

confidence: 99%

Assessment of Water Flow and Sedimentation Processes in Irrigation Schemes for Decision-Support Tool Development: A Case Review for the Chókwè Irrigation Scheme, Mozambique

et al. 2019

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Water flow and sedimentation processes have been significantly erratic at the Chókwè Irrigation Scheme (CIS) and have affected its hydraulic performance. Given its expansion there is need to understand these processes taking place on-site and along the channels of the scheme. CIS being the biggest project of its kind in Mozambique requires proper management of water flow and sedimentation processes. Therefore, the effect of water flow, sediment transport and deposition parameters on the performance of the CIS is needed. In order to determine the effect of spatial and temporal water flow and sediment distribution trends along the irrigation canals, there is need to establish a correlation between these parameters. Determining the influence of water flow velocity on sediment settling rate at different depths along the canal reaches is important in managing the CIS. In addition, a developed decision-support tool to predict sediment deposition is required. For this reason, it is therefore crucial to carry out a timely assessment of water flow and sedimentation processes in CIS in a review concept. From the current review, some gaps that exist for more focused research on Chókwè Irrigation Scheme have been identified. In this regard therefore, there is need to develop an effective support tool for managing water flow and sediment deposition along the canal reaches with a view to increasing crop production in CIS.

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Grain size distribution effects on phosphate sorption by fluvial sediment: implications for modelling sediment-phosphate transport

Cited by 16 publications

References 30 publications

Assessing the Yield and Load of Contaminants with Stream Order: Would Policy Requiring Livestock to Be Fenced Out of High‐Order Streams Decrease Catchment Contaminant Loads?

Assessing the Yield and Load of Contaminants with Stream Order: Would Policy Requiring Livestock to Be Fenced Out of High‐Order Streams Decrease Catchment Contaminant Loads?

Likely controls on dissolved reactive phosphorus concentrations in baseflow of an agricultural stream

Assessment of Water Flow and Sedimentation Processes in Irrigation Schemes for Decision-Support Tool Development: A Case Review for the Chókwè Irrigation Scheme, Mozambique

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