On field‐scale dispersion of strongly sorbing solutes in soils

Streck, Thilo; Piehler, Hans

doi:10.1029/98wr01734

Cited by 8 publications

(6 citation statements)

References 21 publications

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“…In case of strongly sorbing solutes, the water regime can be modeled in a simplified way because displacement of Cd in soil is insensitive to volumetric water content (Streck and Piehler, 1998; Seuntjens et al, 2002). Therefore, the model runs with constant volumetric water content with depth.…”

Section: Modelingmentioning

confidence: 99%

Modeling the Environmental Fate of Cadmium in a Large Wastewater Irrigation Area

Ingwersen

Streck

2006

J of Env Quality

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The fate of cadmium in soils is governed by spatially heterogeneous processes that proceed from decades to centuries. This study aimed at modeling the fate of Cd within the wastewater irrigation area (WIA) of Braunschweig (Germany). The sandy soils (mainly Dystric Cambisol or Typic Haplumbrept) at this site (28 km2) have received considerable loads of heavy metals by irrigation of municipal wastewater for up to 40 yr. The soils of the WIA are in agricultural use. The main crops are sugar beet (Beta vulgaris L.), potato (Solanum tuberosum L.), and wheat (Triticum aestivum L.). As a result of asparagus (Asparagus officinalis L.) cropping, about 15% of the soils have been converted to Rigosols. In 1996, we measured the vertical distribution (0 to 1.2 m) of soil pH, organic carbon content, and the EDTA-extractable content and the solution phase concentration of Cd at 153 sites. At sites not used for asparagus cultivation, Cd has migrated on average to a depth of about 0.5 m. Due to deep plowing, which accelerates migration, Cd has been displaced on average to about 0.7 m at the Rigosol sites. To model the fate of Cd at the scale of the WIA, we used different parallel soil column approaches. In each column the local model SEFAH was used to simulate both displacement and plant uptake of Cd. The model was fed with measured or randomly generated soil data. The results of retrospective simulations from 1957 to 1996 agreed well with observed Cd profiles. The better the spatial variability of sorption was described, the better the performance. Our simulation results show that Cd pollution of soil at first affects the soil-plant pathway. The breakthrough of Cd to the groundwater is dampened and is delayed for many decades.

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Section: Modelingmentioning

confidence: 99%

Modeling the Environmental Fate of Cadmium in a Large Wastewater Irrigation Area

Ingwersen

Streck

2006

J of Env Quality

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“…Sorption can increase or decrease as water content decreases because of changes in sorption site availability, solution chemistry, soil chemistry, and soil structural changes for example [Walker, 1974;Streck and Piehler, 1998;Heppell et al, 2000Heppell et al, , 2004. Additionally, the assumption of a constant water content in the retardation term was found to be satisfactory for the prediction of the transport of strongly sorbing metals [Streck and Piehler, 1998]. A constant retardation factor may occur from the trade-off between increasing sorption but with access to fewer sorption sites as a soil drys.…”

Section: Modelmentioning

confidence: 99%

Modeling the effect of rainfall intermittency on the variability of solute persistence at the soil surface

McGrath

Hinz

Sivapalan

2008

Water Resources Research

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[1] A number of processes contribute to the decrease in solute concentration in the near surface; these include leaching and degradation. The combined effect of all loss processes is termed dissipation; its converse is termed persistence. In this paper we derive analytical expressions for the statistics of the time for a chemical, which undergoes linear equilibrium sorption and first-order degradation under the influence of a random series of rainfall events, to dissipate to a specified concentration. Rainfall is characterized by a random time between events and a random storm depth, both of which are assumed to be exponentially distributed. Analytical expressions for the mean and variance of the time for dissipation to 50% (DT 50 ) and 10% (DT 90 ) of the applied concentration are derived. The model is in qualitative agreement with empirical observations of pesticide dissipation. The model results indicate that on average these solutes tend to dissipate exponentially with time. Rapid dissipation initially, followed by slower dissipation later, is more likely to occur. This may contribute to observations of apparent multirate dissipation which can be explained without recourse to sorption or biological kinetics. A larger average storm magnitude and/or more frequent storms reduce the mean and increase the coefficient of variation of dissipation times. A normal distribution, parameterized using the derived statistics, approximated the probability distribution of dissipation times reasonably well. On the basis of this we obtain a measure of the potential amount of chemical available for rapid off-site leaching at a given time since application.

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“…The choice is based on the following reasoning. First, according to Streck and Piehler (1998), the mean travel time of strongly sorbing solutes is insensitive to variations in the water content θ. Hence, instead of assessing the probability density functions (pdf) of v (e.g., by means of a tracer experiment), modeling of the transport of strongly sorbing solutes can be based on the pdf of the water flux density q and assuming constant water content.…”

Section: Theorymentioning

confidence: 99%

“…[8] Local column scale dispersion, if not available for the investigated site, may be derived from literature (for a review of dispersivity length, see Vanderborght and Vereecken, 2007). Column scale dispersion has no significant effect on trace element transport at the field scale because at this scale, solute spreading is caused to a high degree by the spatial variability of sorption (Streck and Piehler, 1998). The water content θ of the horizons is set to field capacity.…”

Section: Theorymentioning

confidence: 99%

Quantifying the Influence of Uncertainty and Variability on Groundwater Risk Assessment for Trace Elements

Altfelder

Duijnisveld

Streck

et al. 2007

Vadose Zone Journal

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The application of leaching models to predict field‐scale heavy metal transport has been successful at several sites. Past studies involved site‐specific sorption experiments to quantify the leaching process and to investigate its spatial variability. Uncertainty due to lack of knowledge was frequently ignored. Here we present a leaching model that is based on an extended Freundlich equation to describe sorption. The equation is derived on a nationwide scale and is applicable to arbitrary sites in Germany. Instead of relying on site‐specific sorption experiments, it only requires information on the spatial variability of pH, organic carbon (Corg), and clay content. In addition to accounting for spatial variability, the model also considers the major sources of uncertainty influencing a leaching prediction. These sources involve uncertainty in the spatial distribution of pH, Corg, and clay content, as well as uncertainty of the extended Freundlich equation. The modeling strategy is based on a parallel soil column approach, in which a deterministic transport model is combined with a two‐dimensional Monte Carlo method. The model's ability to predict downward movement is tested on two sites in Germany—a wastewater irrigation area and an area in the vicinity of a metal smelter—where cadmium leaching has been modeled previously using extended Freundlich equations derived from local sorption data. Without any parameter fitting involved, the predicted field‐averaged cadmium profiles agree quite well with measured profiles in both cases.

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On field‐scale dispersion of strongly sorbing solutes in soils

Cited by 8 publications

References 21 publications

Modeling the Environmental Fate of Cadmium in a Large Wastewater Irrigation Area

Modeling the Environmental Fate of Cadmium in a Large Wastewater Irrigation Area

Modeling the effect of rainfall intermittency on the variability of solute persistence at the soil surface

Quantifying the Influence of Uncertainty and Variability on Groundwater Risk Assessment for Trace Elements

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