Distribution and mass of groundwater orthophosphorus in an agricultural watershed

Schilling, Keith E.; Streeter, Matthew T.; Isenhart, Thomas M.; Beck, William J.; Tomer, Mark D.; Cole, Kevin J.; Kovar, John L.

doi:10.1016/j.scitotenv.2018.01.035

Cited by 15 publications

(7 citation statements)

References 59 publications

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“…Overall, the concentrations of dissolved P in the reactor experiment were within the range of measured dissolved P concentrations in four southern Iowa streams reported by Hongthanat et al [44] and those reported for Walnut Creek in 2015 and 2016 by Shilling et al [24]. Schilling et al .…”

Section: Resultssupporting

confidence: 84%

“…Schilling et al . [24] also reported that dissolved P concentrations in groundwater sampled over that two-year period from wells in the Walnut Creek floodplain averaged 0.11 mg P L -1 , but in groundwater sampled from upland wells averaged 0.05 mg P L -1 . Schilling et al .…”

Section: Resultsmentioning

confidence: 99%

“…Schilling et al . [24] also found that dissolved oxygen concentrations (but not Eh values) were significantly lower in floodplain than in upland groundwater, and they suggested that a greater prevalence of anaerobic microsites in the floodplain sediments could have increased dissolved P concentrations in the groundwater.…”

Section: Resultsmentioning

confidence: 99%

“…The stream is representative of many in the glaciated upper Midwest of the US that have incised sediments affected by recent agricultural practices as well as older Holocene sediments. The fate of P in the stream and its watershed have been extensively studied with respect to channel storage, stream bank erosion, and suspended sediment transport [18, 19] as well as riparian groundwater dynamics [20, 21, 22, 23, 24]. In addition, we have recently characterized the amounts and distribution of the forms of P in bank sediments, in-stream sediments, and floodplain sediments of Walnut Creek [25], and we have identified the forms of P in the sediments that are most susceptible to release to the water column under low redox conditions [26].…”

Section: Introductionmentioning

confidence: 99%

“…During much of the year, flow in Walnut Creek is derived mainly from low-redox-potential groundwater discharge that enters the channel through the Gunder Member of the Holocene DeForest Formation [22, 24]. The groundwater carries low concentrations of P (averaging about 0.05 mg L -1 ).…”

Section: Introductionmentioning

confidence: 99%

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Varying redox potential affects P release from stream bank sediments

2018

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Sediments in streams that drain agricultural watersheds may be sinks that can adsorb P from the stream or sources that can release P to the stream. Sediment characteristics and environmental factors, including the oxidation-reduction (redox) potential of the water associated with the sediment, determine whether P will be adsorbed or released by the sediment. We investigated P adsorption and release by four sediments [three Holocene-age sediments (Camp Creek, Roberts Creek and Gunder) as well as Pre-Illinoian-age Till] that occur in Walnut Creek, a second-order stream in Jasper County, Iowa, that is representative of many small streams in the glaciated upper Midwest of the US. The effects of two redox potentials on phosphorus buffering capacity (PBC) and equilibrium phosphorus concentration (EPC) were evaluated in batch adsorption experiments. We also simulated aerobic and anerobic conditions over a 24-day period and measured solution-phase P concentrations in stirred systems where the sediments were isolated from the water by dialysis tubing. The batch experiment indicated that the EPCs of the three Holocene-age sediments were similar to one another and increased with decreasing redox potential. In the stirred flow reactors, more dissolved P was released from the Camp Creek and Roberts Creek sediments under anaerobic conditions than from the other sediments. This observation suggests that these two sediments, which are younger and higher in the stratigraphic sequence, are more likely to be P sources in suboxic settings. The P buffering capacity was greatest in the till. Where it is in contact with the stream water, the till is likely to serve as an adsorbing sink for P in the water column.

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Section: Resultssupporting

confidence: 84%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Varying redox potential affects P release from stream bank sediments

2018

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Dissolved phosphate concentrations in Iowa shallow groundwater

et al. 2020

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Regional groundwater phosphorus (P) concentrations are rarely reported, and it is important to develop a better understanding of background concentrations in shallow groundwater to help develop strategies to mitigate environmental risks. In this study, results collected from 17 different Iowa‐based studies conducted from 2006 to 2019 and a total of 210 discrete locations of water table dissolved phosphate (DPO43−) measurements are summarized (a) to assess the occurrence, range, and statistical distribution of groundwater DPO43− concentrations in Iowa and (b) to evaluate statewide patterns of DPO43−concentrations related to land use or land cover and landscape position. The DPO43− concentrations ranged from 0.02 to 1.56 mg L−1 and averaged 0.15 ± 0.19 mg L−1 with a median value of 0.10 mg L−1 (95% confidence interval of 0.08–0.11 mg L−1). Although minor variations were observed among land cover class and landscape position, concentrations exhibited uniformity across the state, likely attesting to the legacy of P from historical agricultural management. Median concentrations are higher than typical water quality criteria used to assess risk to surface water systems, implying that simply discharging groundwater DPO43− to streams, rivers, and lakes would be sufficient to cause environmental degradation.

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Phosphorus transformations in stream bank sediments in Iowa, USA, at varying redox potentials

2018

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Purpose Stream bank erosion is one of the main sources of suspended sediments in stream water, and it often carries phosphorus with it. With a controlled laboratory study, we investigated the changes in different forms of P in stream bank sediments at varying redox potentials. We hypothesized that there could be increases in labile forms of solid-phase P under low redox conditions. Materials and methods Sediment samples representing four major stratigraphic units were collected from alluvial banks of Walnut Creek in Jasper County, Iowa: Camp Creek, Roberts Creek, and Gunder members of the Holocene-age De Forest Formation and pre-Illinoian till, a glacial deposit that is older than 500,000 years. We compared three treatments: no anaerobic incubation, anaerobic incubation, and anaerobic incubation with addition of glucose. After each treatment, soil P fractions were determined and classified as water-extractable P, labile P, slowly cycling P, stable P, and residual P. Labile P is extractable with 0.5 M NaHCO 3 , slowly cycling P is extractable with 0.1 M NaOH or 1 M HCl, stable P is extractable with concentrated HCl, and residual P is associated with acid-insoluble compounds in the soil. Results and discussion Redox potential of the equilibrated systems was significantly less when sediments were incubated anaerobically than when they were not incubated, especially when glucose was added to the anaerobic incubation. Variations in redox potential did not significantly affect the total P, organic or inorganic stable P, or residual P in the sediments. In contrast, we found that the amount of inorganic labile P tended to increase at the same time that slowly cycling P associated with Fe decreased. Conclusions The younger sediments, higher in the stratigraphic profile and with more organic matter, had greater labile P and slowly cycling P that was associated with Fe, reflecting a greater potential to contribute to elevated levels of P in the stream water if subjected to low redox potential in the stream environment. The forms of P in the four bank sediments were redistributed among the fractions by reducing conditions. There was an increase in the concentration of inorganic labile P, which coincided with a decrease in slowly cycling P associated with Fe, especially in the Holocene-age sediments. These sediments appear to have a greater potential to contribute to elevated levels of P in the stream water when they are subjected to low redox potential in the stream environment.

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Distribution and mass of groundwater orthophosphorus in an agricultural watershed

Cited by 15 publications

References 59 publications

Varying redox potential affects P release from stream bank sediments

Varying redox potential affects P release from stream bank sediments

Dissolved phosphate concentrations in Iowa shallow groundwater

Phosphorus transformations in stream bank sediments in Iowa, USA, at varying redox potentials

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