Combined Source Apportionment and Degradation Quantification of Organic Pollutants with CSIA: 1. Model Derivation

Lutz, Stefanie; Breukelen, Boris M. van

doi:10.1021/es405400w

Cited by 17 publications

(11 citation statements)

References 52 publications

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“…Further, the recent boom of promising new tracer techniques can yield such information. These range from the utilization of DNA tracers (Sharma et al ., ) to compound specific isotope tracers (Lutz and Van Breukelen, ) with many variants in between. Of course, as our ability to trace flow paths in the landscape improves, our efforts to model multiple tracers (Van der Velde et al ., ), track preferential flows through systems (Davies et al ., ; Hrachowitz et al ., ) and design tracer‐based experiments (Harman and Kim, ) need to adapt accordingly.…”

Section: Discussionmentioning

confidence: 99%

Consequences of mixing assumptions for time‐variable travel time distributions

Velde

Heidbüchel

Lyon

et al. 2014

Hydrological Processes

113

109

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The current generation of catchment travel time distribution (TTD) research, integrating nearly three decades of work since publication of Water's Journey from Rain to Stream, seeks to represent the full distribution in catchment travel times and its temporal variability. Here, we compare conceptualizations of increasing complexity with regards to mixing of water storages and evaluate how these assumptions influence time-variable TTD estimates for two catchments with contrasting climates: the Gårdsjön catchment in Sweden and the Marshall Gulch catchment in Arizona, USA. Our results highlight that, as long as catchment TTDs cannot be measured directly but need to be inferred from input-output signals of catchments, the inferred catchment TTDs depend strongly on the underlying assumptions of mixing within a catchment. Furthermore, we found that the conceptualization of the evapotranspiration flux strongly influences the inferred travel times of stream discharge. For the wet and forested Gårdsjön catchment in Sweden, we inferred that evapotranspiration most likely resembles a completely mixed sample of the water stored in the catchment; however, for the drier Marshall Gulch catchment in Arizona, evapotranspiration predominantly contained the younger water stored in the catchment. For the Marshall Gulch catchment, this higher probability for young water in evapotranspiration resulted in older water in the stream compared to travel times inferred with assumptions of complete mixing. New observations that focus on the TTD of the evapotranspiration flux and the actual travel time of water through a catchment are necessary to improve identification of mixing and consequently travel times of stream water. a a Hrachowitz et al. (2013) tested multiple different conceptualizations. The number of parameters depends on number of reservoirs and storage type.3462 Y. VAN DER VELDE ET AL.

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Section: Discussionmentioning

confidence: 99%

Consequences of mixing assumptions for time‐variable travel time distributions

Velde

Heidbüchel

Lyon

et al. 2014

Hydrological Processes

113

109

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“…Regarding assumption (ii), we postulate that the end‐member signatures are not subject to significant isotope fractionation before mixing, in agreement with end‐member mixing models that assume conservative end‐member concentrations. This yields a conservative (i.e., smaller) estimate of the extent of denitrification with the SISS‐N model in comparison to scenarios of prior denitrification before mixing (Lutz & Van Breukelen, 2014a).…”

Section: Mixing and Transformation Modelsmentioning

confidence: 99%

“…We combined two different models in the assessment of mixing between river water and groundwater and NO 3 − removal: a linear mixing model using Cl − and NO 3 − concentrations and the SISS model (Lutz & Van Breukelen, 2014a) using the δ 15 N and δ 18 O values of NO 3…”

Section: Model Assumptionsmentioning

confidence: 99%

“…The new manuscript gives the corrected equations and describes the direct application of the simplified SISS model (see Lutz and Van Breukelen, 2014a) to determine the theoretical mixing signature and derive the extent of denitrification. Equations () and () in the published paper are incorrect as they do not account for nitrate concentration differences in the mixing endmembers, which affect the isotopic mixing signature and, hence, all subsequent calculations with the SISS‐N model.…”

Section: Mixing and Transformation Modelsmentioning

confidence: 99%

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How Important is Denitrification in Riparian Zones? Combining End‐Member Mixing and Isotope Modeling to Quantify Nitrate Removal from Riparian Groundwater

Lutz

Trauth

Musolff

et al. 2020

Water Resources Research

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Riparian zones are important buffer zones for streams as they are hotspots of nitrate transformation and removal in agricultural catchments. However, mixing of water from different sources and various transformation processes can complicate the quantification of nitrate turnover in riparian zones. In this study, we analyzed nitrate concentration and isotope data in riparian groundwater along a 2-km stream section in central Germany. We developed a mathematical model combining end-member mixing and isotope modeling to account for mixing of river water and groundwater and quantify nitrate transformation in riparian groundwater. This enabled us to explicitly determine the extent of denitrification (as process leading to permanent nitrate removal from riparian groundwater) and transient nitrate removal by additional processes associated with negligible isotope fractionation (e.g., plant uptake and microbial assimilation) and to perform an extensive uncertainty analysis. Based on the nitrogen isotope data of nitrate, the simulations suggest a mean removal of up to 27% by additional processes and only about 12% by denitrification. Nitrate removal from riparian groundwater by additional processes exceeded denitrification particularly in winter and at larger distance from the river, underlining the role of the river as organic carbon source. This highlights that nitrate consumption by additional processes predominates at the field site, implying that a substantial fraction of agricultural nitrogen input is not permanently removed but rather retained in the riparian zone. Overall, our model represents a useful tool to better compare nitrogen retention to permanent nitrogen removal in riparian zones at various temporal and spatial scales. Plain Language SummaryNitrogen is an important nutrient for agricultural crops. However, excessive nitrogen input into surface water in the form of nitrate can lead to algae blooms and lack of oxygen. The riparian zones of rivers are important buffer zones where groundwater is connected to soils, which are rich in soil organisms and organic matter pools fueling reaction processes. Hence, plants and bacteria can remove nitrate from riparian groundwater before it reaches the river. Bacterial consumption of nitrate (denitrification) leads to complete removal of nitrogen via release of nitrogen gas into the atmosphere. In contrast, other biogeochemical processes such as nitrate uptake by plants merely result in nitrogen retention within riparian zones. To quantify the role of denitrification relative to other processes, we developed a novel model combining concentration and isotope data of nitrate and applied it to a groundwater study site in Central Germany. We found that nitrate removal from riparian groundwater by additional processes largely exceeded denitrification. Hence, a major fraction of nitrogen inputs was retained in the riparian zone and may eventually end up in the river. Such information is highly relevant for many river ecosystems at risk of eutrophication because of high nitr...

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“…Alvarez-Saldivar et al [ 29 ] applied mass balance to evaluate the natural attenuation of pesticides at the catchment scale. The stable isotope sources and sinks model is one of the examples developed by Lutz and Breukelen [ 112 ] using a mathematical model for two mixing sources and degradation via one reaction pathway. This model is based on a linear stable isotope mixing model and the Rayleigh equation and can cover the simultaneous occurrence of degradation processes and mixing of emission sources of organic pollutants and even inorganic compounds such as nitrate.…”

Section: Applications Of Csia For Monitor Pesticide Pollution In Environments and Agricultural Productsmentioning

confidence: 99%

Application of Compound-Specific Isotope Analysis in Environmental Forensic and Strategic Management Avenue for Pesticide Residues

et al. 2021

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Unintended pesticide pollution in soil, crops, and adjacent environments has caused several issues for both pesticide users and consumers. For users, pesticides utilized should provide higher yield and lower persistence while considering both the environment and agricultural products. Most people are concerned that agricultural products expose humans to pesticides accumulating in vegetation. Thus, many countries have guidelines for assessing and managing pesticide pollution, for farming in diverse environments, as all life forms in soil are untargeted to these pesticides. The stable isotope approach has been a useful technique to find the source of organic matter in studies relating to aquatic ecology and environmental sciences since the 1980s. In this study, we discuss commonly used analytical methods using liquid and gas chromatography coupled with isotopic ratio mass spectrometry, as well as the advanced compound-specific isotope analysis (CSIA). CSIA applications are discussed for tracing organic pollutants and understanding chemical reactions (mechanisms) in natural environments. It shows great applicability for the issues on unintended pesticide pollution in several environments with the progress history of isotope application in agricultural and environmental studies. We also suggest future study directions based on the forensic applications of stable isotope analysis to trace pesticides in the environment and crops.

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Combined Source Apportionment and Degradation Quantification of Organic Pollutants with CSIA: 1. Model Derivation

Cited by 17 publications

References 52 publications

Consequences of mixing assumptions for time‐variable travel time distributions

Consequences of mixing assumptions for time‐variable travel time distributions

How Important is Denitrification in Riparian Zones? Combining End‐Member Mixing and Isotope Modeling to Quantify Nitrate Removal from Riparian Groundwater

Application of Compound-Specific Isotope Analysis in Environmental Forensic and Strategic Management Avenue for Pesticide Residues

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