| 1. |
- Jaeger, Anna, et al.
(författare)
-
Transformation of organic micropollutants along hyporheic flow in bedforms of river-simulating flumes
- 2021
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- Urban streams receive increasing loads of organic micropollutants from treated wastewaters. A comprehensive understanding of the in-stream fate of micropollutants is thus of high interest for water quality management. Bedforms induce pumping effects considerably contributing to whole stream hyporheic exchange and are hotspots of biogeochemical turnover processes. However, little is known about the transformation of micropollutants in such structures. In the present study, we set up recirculating flumes to examine the transformation of a set of micropollutants along single flowpaths in two triangular bedforms. We sampled porewater from four locations in the bedforms over 78 days and analysed the resulting concentration curves using the results of a hydrodynamic model in combination with a reactive transport model accounting for advection, dispersion, first-order removal and retardation. The four porewater sampling locations were positioned on individual flowpaths with median solute travel times ranging from 11.5 to 43.3 h as shown in a hydrodynamic model previously. Highest stability was estimated for hydrochlorothiazide on all flowpaths. Lowest detectable half-lives were estimated for sotalol (0.7 h) and sitagliptin (0.2 h) along the shortest flowpath. Also, venlafaxine, acesulfame, bezafibrate, irbesartan, valsartan, ibuprofen and naproxen displayed lower half-lives at shorter flowpaths in the first bedform. However, the behavior of many compounds in the second bedform deviated from expectations, where particularly transformation products, e.g. valsartan acid, showed high concentrations. Flowpath-specific behavior as observed for metformin or flume-specific behavior as observed for metoprolol acid, for instance, was attributed to potential small-scale or flume-scale heterogeneity of microbial community compositions, respectively. The results of the study indicate that the shallow hyporheic flow field and the small-scale heterogeneity of the microbial community are major controlling factors for the transformation of relevant micropollutants in river sediments.
|
|
| 2. |
- Lewandowski, Jörg, et al.
(författare)
-
Is the Hyporheic Zone Relevant beyond the Scientific Community?
- 2019
-
Ingår i: Water. - : MDPI AG. - 2073-4441. ; 11:11
-
Tidskriftsartikel (refereegranskat)abstract
- Rivers are important ecosystems under continuous anthropogenic stresses. The hyporheic zone is a ubiquitous, reactive interface between the main channel and its surrounding sediments along the river network. We elaborate on the main physical, biological, and biogeochemical drivers and processes within the hyporheic zone that have been studied by multiple scientific disciplines for almost half a century. These previous efforts have shown that the hyporheic zone is a modulator for most metabolic stream processes and serves as a refuge and habitat for a diverse range of aquatic organisms. It also exerts a major control on river water quality by increasing the contact time with reactive environments, which in turn results in retention and transformation of nutrients, trace organic compounds, fine suspended particles, and microplastics, among others. The paper showcases the critical importance of hyporheic zones, both from a scientific and an applied perspective, and their role in ecosystem services to answer the question of the manuscript title. It identifies major research gaps in our understanding of hyporheic processes. In conclusion, we highlight the potential of hyporheic restoration to efficiently manage and reactivate ecosystem functions and services in river corridors.
|
|
| 3. |
- McCallum, James L., et al.
(författare)
-
A Numerical Stream Transport Modeling Approach Including Multiple Conceptualizations of Hyporheic Exchange and Spatial Variability to Assess Contaminant Removal
- 2020
-
Ingår i: Water resources research. - 0043-1397 .- 1944-7973. ; 56:3
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding the mechanisms and controls on contaminant removal in streams is essential in managing human and ecosystem health. The hyporheic zone (HZ) plays a key role in the removal of contaminants from streams. Often, tracer tests are implemented in conjunction with measurements of compounds to assess the removal rates of contaminants in streams. The predicted removal rates largely rely on the estimated hyporheic residence time, and hence, the chosen conceptual model of hyporheic exchange flows (HEFs) will influence the predicted removal rate. Despite this, different HEF models are generally not considered when assessing contaminant removal rates. In this paper, we present a numerical modeling approach for interpreting tracer tests to determine contaminant removal rates that allows for multiple conceptual models of HEF to be considered. We demonstrate this method by interpreting data from a conservative tracer test in conjunction with grab samples of trace organic compounds using two commonly used models of HEF: one that assumes first-order exchange between the stream and the HZ and one that considers a power law weighting of first-order exchange coefficients. For the three degrading compounds measured, guanylurea, valsartan, and diclofenac, we observed that the power law model consistently predicted higher removal rates in the stream compared to the first-order model. Variations were also observed between the removal rates estimated in the HZ. Our results highlight the importance of considering multiple conceptualizations of the HEF when assessing contaminant removal rates.
|
|
| 4. |
|
|
| 5. |
- Schaper, Jonas L., et al.
(författare)
-
Hyporheic Exchange Controls Fate of Trace Organic Compounds in an Urban Stream
- 2018
-
Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 52:21, s. 12285-12294
-
Tidskriftsartikel (refereegranskat)abstract
- First-order half-lives for 26 trace organic (TrOCs) were determined in the hyporheic zone (HZ) and along a 3 km reach of a first-order stream in m South Australia during both dry and wet seasons. Two salt in-stream tracer experiments were conducted and evaluated using a transient storage model to characterize seasonal differences in stream residence time and transient storage. Lagrangian and time-integrated surface water sampling were conducted to calculated half-lives in the surface water. Half-lives in the were calculated using porewater samples obtained from a modified mini-point sampler and hyporheic residence times measured via active heat-pulse sensing. Half of the investigated TrOCs (e.g., oxazepam, olmesartan, candesartan) were not significantly removed along both the investigated river stretch and the sampled hyporheic flow paths. The remaining TrOCs (e.g., metformin, guanylurea, valsartan) were found to be significantly removed in the HZ and along the river stretch with relative removals in the HZ correlating to reach-scale relative removals. Using the modeled transport parameters, it was estimated that wet season reach-scale removal of TrOCs was predominately caused by removal in the HZ when the intensity of hyporheic exchange was also higher. Factors that increase HZ exchange are thus likely to promote in-stream reactivity of TrOCs.
|
|
| 6. |
- Jaeger, Anna, et al.
(författare)
-
Time Series of Electrical Conductivity Fluctuations Give Insights Into Long-Term Solute Transport Dynamics of an Urban Stream
- 2023
-
Ingår i: Water resources research. - : American Geophysical Union (AGU). - 0043-1397 .- 1944-7973. ; 59:7
-
Tidskriftsartikel (refereegranskat)abstract
- Artificial tracers are often used for quantitative estimates of solute transport properties in rivers. However, single-injection tracer tests give insights in transport characteristics limited to the ecohydrological conditions at the testing time. Series of time-consuming and laborious tracer tests would be required to properly capture seasonal changes. The present study uses intrinsic diurnal fluctuations of electrical conductivity (EC) caused by discharge of treated wastewater as a tracer to evaluate solute transport processes along a 4.7-km reach of the River Erpe, Germany. By reproducing the fluctuations recorded along the river using the solute transport model one-dimensional transport with inflow and storage, this study investigated the long-term dynamics in solute transport properties. Individual 48-hr curves of EC were used in the steady state configuration of the model to gain 48-hr-integrated estimates of selected transport parameters. Using a sliding window approach in 1-hr steps along the 2,270-hr time series of EC the temporal variability of solute transport between April and June 2016 was assessed. To test the identifiability of parameters using the proposed method, sensitivity analyses and a breakthrough curve analysis of selected 48-hr windows were implemented. With time advancing into the summer, a significant rising trend (Mann-Kendall test p-value < 0.05) of the cross sectional area of the channel was observed and attributed to the growth of macrophytes and a significant slightly decreasing trend for the storage rate was found. The presented method is of high value for river management, as promoting transient storage enhances biogeochemical cycling and benefits water quality.
|
|
| 7. |
- Posselt, Malte, et al.
(författare)
-
Determination of polar organic micropollutants in surface and pore water by high-resolution sampling-direct injection-ultra high performance liquid chromatography-tandem mass spectrometry
- 2018
-
Ingår i: Environmental Science. - : Royal Society of Chemistry (RSC). - 2050-7887 .- 2050-7895. ; 20:12, s. 1716-1727
-
Tidskriftsartikel (refereegranskat)abstract
- Hyporheic zones (HZs) are dynamic and complex transition regions between rivers and aquifers which are thought to play an important role in the attenuation of environmental micropollutants. Non-steady state and small-scale hyporheic processes which affect micropollutants in the HZ are poorly characterized due to limitations in existing analytical methodologies. In this work we developed a method for high spatio-temporal resolution analysis of polar organic micropollutants (POMs) in hyporheic pore- and surface waters by combining (semi-) automatic low volume sampling techniques with direct-injection ultra-high performance liquid chromatography tandem mass spectrometry. The method is capable of quantifying 25 parent compounds and 18 transformation products (TPs) using only 0.4 mL of water and few preparation steps. Application of the method to both surface and pore water revealed significant (i.e. > an order of magnitude) differences in POM concentrations over small time and spatial scales (i.e. < a few hours and tens of cm, respectively). Guanylurea, a TP of the antidiabetic drug metformin was detected at unprecedentedly high concentrations. Collectively, this method is suitable for in situ characterization of POMs at high spatial and temporal resolution and with minimal disturbance of natural flow paths and infiltration of surface water.
|
|
| 8. |
- Schaper, Jonas L., et al.
(författare)
-
Fate of Trace Organic Compounds in the Hyporheic Zone : Influence of Retardation, the Benthic Biolayer, and Organic Carbon
- 2019
-
Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 53:8, s. 4224-4234
-
Tidskriftsartikel (refereegranskat)abstract
- The fate of 28 trace organic compounds (TrOCs) was investigated in the hyporheic zone (HZ) of an urban lowland river in Berlin, Germany. Water samples were collected hourly over 17 h in the river and in three depths in the HZ using minipoint samplers. The four relatively variable time series were subsequently used to calculate first order removal rates and retardation coefficients via a one-dimensional reactive transport model. Reversible sorption processes led to substantial retardation of many TrOCs along the investigated hyporheic flow path. Some TrOCs, such as dihydroxy-carbamazepine, O-desmethylvenlafaxine, and venlafaxine, were found to be stable in the HZ. Others were readily removed with half-lives in the first 10 cm of the HZ ranging from 0.1 +/- 0.01 h for iopromide to 3.3 +/- 0.3 h for tramadol. Removal rate constants of the majority of reactive TrOCs were highest in the first 10 cm of the HZ, where removal of biodegradable dissolved organic matter was also the highest. Because conditions were oxic along the top 30 cm of the investigated flow path, we attribute this finding to the high microbial activity typically associated with the shallow HZ. Frequent and short vertical hyporheic exchange flows could therefore be more important for reach-scale TrOC removal than long, lateral hyporheic flow paths.
|
|
