A small volume multiplexed pumping system for automated, high
frequency water chemistry measurements in volume-limited
applications

Maxwell, Bryan M.; Bírgand, François; Smith, Brad; Aveni-Deforge, Kyle

doi:10.5194/hess-2018-220

Cited by 5 publications

(9 citation statements)

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“…Stock tank and column outflow water chemistry were measured using a small volume multiplexed pumping system (MPS) (Maxwell et al, 2018) coupled to a high frequency spectrophotometer. The MPS sequentially pumped 25‐mL samples from each column for absorbance measurement by a field spectrophotometer (Spectro::lyser Type SP‐1‐035‐p0‐s‐NO‐075; s::can) fitted with a 4‐mm path length, 1.1‐mL flow through quartz cuvette (46‐Q‐4, Starna Cells, Inc.).…”

Section: Methodsmentioning

confidence: 99%

“…polytetrafluoroethylene tubing (0.2 mL s −1 ) through a 60‐μm plankton mesh screened intake placed in the top 3 cm of the saturated media in each column. To minimize cross‐contamination between columns, the first 5 mL of sample volume were diverted to waste, after which 20 mL of sample volume (>18 times cuvette volume) were pumped for spectrophotometric analysis, according to validated sampling procedures for the small volume MPS (Maxwell et al, 2018). Low pump rate and sample volume (25 mL every 2 h) were used to limit impact of sampling on column hydraulics (sample volume <2% of cumulative flow volume over 2 h).…”

Section: Methodsmentioning

confidence: 99%

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Drying–Rewetting Cycles Affect Nitrate Removal Rates in Woodchip Bioreactors

et al. 2019

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Woodchip bioreactors are widely used to control nitrogen export from agriculture using denitrification. There is abundant evidence that drying–rewetting (DRW) cycles can promote enhanced metabolic rates in soils. A 287‐d experiment investigated the effects of weekly DRW cycles on nitrate (NO3) removal in woodchip columns in the laboratory receiving constant flow of nitrated water. Columns were exposed to continuous saturation (SAT) or to weekly, 8‐h drying‐rewetting (8 h of aerobiosis followed by saturation) cycles (DRW). Nitrate concentrations were measured at the column outlets every 2 h using novel multiplexed sampling methods coupled to spectrophotometric analysis. Drying–rewetting columns showed greater export of total and dissolved organic carbon and increased NO3 removal rates. Nitrate removal rates in DRW columns increased by up to 80%, relative to SAT columns, although DRW removal rates decreased quickly within 3 d after rewetting. Increased NO3 removal in DRW columns continued even after 39 DRW cycles, with ∼33% higher total NO3 mass removed over each weekly DRW cycle. Data collected in this experiment provide strong evidence that DRW cycles can dramatically improve NO3 removal in woodchip bioreactors, with carbon availability being a likely driver of improved efficiency. These results have implications for hydraulic management of woodchip bioreactors and other denitrification practices. Core Ideas Weekly, 8‐h drying–rewetting (DRW) cycles increased nitrate removal in woodchip columns. Increased nitrate removal in DRW columns declined with number of days since rewetting. Nitrate removal corresponded to greater leaching of dissolved organic C in DRW columns. Effect of DRW was significant even after 39 weekly DRW cycles.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Drying–Rewetting Cycles Affect Nitrate Removal Rates in Woodchip Bioreactors

et al. 2019

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“…The accuracy of load calculations is dependent on the accuracy of flow and concentration measurements (Pinckney et al., 2001). Here, the efficacy of using DGTDGT for determining the load was modeled using nitrate concentration and flow data measured over 1 mo from a denitrifying bioreactor (Corbett et al., 2019; Maxwell et al., 2018). The bioreactor data were used because they provided a data set with pronounced variations in concentration and flow, and the high frequency of sampling enabled an accurate calculation of the load.…”

Section: Methodsmentioning

confidence: 99%

“…The bioreactor data were used because they provided a data set with pronounced variations in concentration and flow, and the high frequency of sampling enabled an accurate calculation of the load. Nitrate concentrations were determined by grab sampling at 30‐ and 60‐min intervals, and flow measurements were independently measured at the same interval (Corbett et al., 2019; Maxwell et al., 2018). Denitrifying bioreactors are anaerobic carbon‐rich systems designed to support the microbial transformation of excess nitrate to N 2 (g) (Addy et al., 2016; Rivett et al., 2008; Schipper et al., 2010).…”

Section: Methodsmentioning

confidence: 99%

The temperature and flow dependence of nitrate concentration and load estimates based on diffusive gradients in thin films

et al. 2022

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Concentrations determined using diffusive gradients in thin films (DGT) have been used to derive time‐averaged loads in streams and rivers. However, DGT provide time‐weighted average concentrations that assume the independence of concentration and flow. Additionally, dynamic and coordinated changes in temperature, flow, and concentration are potential sources of bias in concentration and load calculations. We modeled scenarios in which temperature and flow were correlated to varying degrees with concentration and evaluated the consequences for DGT concentration and load calculations. As the correlation between solution flow and concentration moved toward 1 and –1, the load determined by DGT either overestimated or underestimated the actual load by as much as 30%. In DGT‐based load estimates, the degree of potential bias should be assessed, and the concentration‐flow relation should be characterized. As the correlation of analyte concentration and temperature approached 1 and –1, the deviation of the concentration determined by DGT from the actual concentration increased. In most cases, this bias was < 2%; however, if the changes in concentration and temperature were large (∼10 mg L–1 and ∼10 °C), the bias exceeded 5%. Concentration and temperature are unlikely to be perfectly or strongly correlated or anti‐correlated in natural systems and thus should not affect the accuracy of DGT concentration calculations in most circumstances. The more solution temperature, flow, and concentration were uncorrelated, the closer DGT‐derived concentration and load were to the actual solution concentration and load.

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“…All data presented in this paper in Sects. 2.3.1, 2.3.2, 3.1, 3.2, 4.2, and 4.3 are provided in .csv files in an online Zenodo repository at https://doi.org/10.5281/zenodo.1453353 (Maxwell, 2018). The online repository also includes the R code (R Studio Ver.1.1.442 or greater) used to generate plots and calculate coefficients for NO − 3 removal kinetic equations.…”

Section: Seasonal and Spatial Variabilitymentioning

confidence: 99%

A small-volume multiplexed pumping system for automated, high-frequency water chemistry measurements in volume-limited applications

Maxwell

Bírgand

Smith

et al. 2018

Hydrol. Earth Syst. Sci.

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Abstract. An automated multiplexed pumping system (MPS) for high-frequency water chemistry measurements at multiple locations previously showed the ability to increase spatial and temporal data resolution and improve understanding of biogeochemical processes in aquatic environments and at the land–water interface. The design of the previous system precludes its use in volume-limited applications in which highly frequent measurements requiring a large sample volume would significantly affect observed processes. A small-volume MPS was designed to minimize the sample volume while still providing high-frequency data. The system was tested for cross-contamination between multiple sources, and two applications of the technology are reported. Cross-contamination from multiple sources was shown to be negligible when using recommended procedures. Short-circuiting of flow in a bioreactor was directly observed using high-frequency porewater sampling in a well network, and the small-volume MPS showed high seasonal and spatial variability of nitrate removal in stream sediments, enhancing data collected from in situ mesocosms. The results show it is possible to obtain high-frequency data in volume-limited applications. The technology is most promising at the reach or transect scale for observing porewater solute dynamics over daily timescales, with data intervals < 1 h for up to 12 locations.

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A small volume multiplexed pumping system for automated, high frequency water chemistry measurements in volume-limited applications

Cited by 5 publications

References 0 publications

Drying–Rewetting Cycles Affect Nitrate Removal Rates in Woodchip Bioreactors

Drying–Rewetting Cycles Affect Nitrate Removal Rates in Woodchip Bioreactors

The temperature and flow dependence of nitrate concentration and load estimates based on diffusive gradients in thin films

A small-volume multiplexed pumping system for automated, high-frequency water chemistry measurements in volume-limited applications

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