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1

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Evaluation of Fluorobenzoate Tracers in Surface Soils (1994)

Jaynes, Dan B.

Oxford, UK : Blackwell Publishing Ltd

Ground water 32 (1994), S. 0

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ISSN: 1745-6584

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences

Notes: The availability of several conservative, noninteracting tracers is desirable for the study of water movement in porous media. Recent studies have identified a family of fluorinated benzoic acid derivatives as having transport properties similar to Br. The transport properties of 2,6-difluorobenzoate (2,6-DFBA), 2,5-difluorobenzoate (2,5-DFBA), 3,4-difluorobenzoate (3,4-DFBA), 3,5-difluorobenzoate (3,5-DFBA), o-(trifluoromethyl)benzoate (o-TFMBA), m-(trifluoromethyl)benzoate (m-TFMBA), and pentafluorobenzoate (PFBA) were compared to Br in two neutral pH, high organic soils from Iowa. Batch equilibrium studies and column transport studies showed that 2,6-DFBA, PFBA, and o-TFMBA have transport properties very similar to Br, although their behavior may deviate slightly as the organic carbon and clay fractions of the soil increase. 2,5-DFBA is retarded less and dispersed slightly more than the above tracers in these soils, but may be a useful tracer since it is still conservative. The other fluorobenzoates showed greater degrees of interaction with the soil matrix and were not conservative precluding their use as acceptable tracers. Plant growth studies using corn (Zea mays L.) and soybean (Glycine max [L] Merr.) showed significantly (P = 0.05) decreased growth for treatments using 3,4-DFBA and 3,5-DFBA, precluding their use in agronomic settings. Given the variation shown here and in earlier studies, the transport behavior of any of the fluorobenzoates should be evaluated prior to use in new environments.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1745-6584.1994.tb00887.x

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2

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Evaluation of the Root Zone Water Quality Model Using Data from the Iowa MSEA (1999)

Jaynes, Dan B. ; Miller, John G.

Springer

Semigroup forum 91 (1999), S. 192-200

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ISSN: 1432-2137

Source: Springer Online Journal Archives 1860-2000

Topics: Mathematics

Notes: Zea may L.-Glycine max (L.) Merr.] rotation. The model was calibrated and initialized using default values supplied with the model and adjusting model parameters to obtain stable organic matter and microorganism pools. The model was further calibrated to match crop yields for the first two years of measurements. For the second two years, predicted soybean yield was within 60 kg ha-1 (3%) of measured yield but predicted corn yield was underpredicted by 790 kg ha-1 (10%). Disagreements between modeled and measured yields may be due to factors not included in the model such as disease and insect damage. The model estimated total soil nitrate content well, although nitrification rates during winter were overestimated. Predicted nitrate leaching out of the root zone agreed well with measured losses to tile drainage. Predictions of herbicide residues with the one-parameter lumped dissipation model option were best after reducing the expected half-lives of metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one], or atrazine [6-chloro-N-ethyl-N′-(1-methylethyl)-1,3,5-triazine-2,4-diamine], by a factor of four. The two-parameter lumped half-life model option improved the prediction for atrazine but not for metribuzin. Predictions of herbicide losses in drainage water were overestimated in the second year following herbicide application. Neither nitrate nor herbicide concentrations in the soil profile were modeled satisfactorily. Invoking the macropore option of the model did not consistently improve model prediction of herbicide leaching. Overall, the model shows promise in predicting the interplay of climate, soil, and management on crop yield and the interplay of climate, soil, and management on crop yield and nitrate fate, but evaluation over a wider range of conditions is needed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/

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3

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Measurement of Field Soil Hydraulic and Solute Transport Parameters (1998)

Casey, Francis X.M. ; Logsdon, Sally D. ; Horton, Robert ; [et al.]

Springer

Soil Science Society of America journal 62 (1998), S. 1172-1178

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ISSN: 1435-0661

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: m ) and immobile (θim) domains, with solute exchange between the domains characterized by the mass-exchange coefficient (α). In this study a sequential tracer application technique was used and K, θ, θim, and α were estimated for a series of pressure heads (H = 10, -30, -60, and -150 mm). This method uses a tension infiltrometer to measure both hydraulic and solute transport parameters in situ. The study took place in a no-till corn (Zea mays L.) field mapped as a Harps series soil (fine-loamy, mixed, mesic Typic Calciaquoll). Unsaturated values of θ and K were distinct from the saturated values. Similarly, though less clear cut, distinctions between saturated and unsaturated values of θim immobile water fraction (θim/θ), and α were observed. The medians of θ for the sequence of decreasing H values were 0.40, 0.34, 0.34, and 0.33 m3m-3. The median K values for the same sequence of H were 108, 1.69, 1.51, and 0.72 μm s-1. The median θim/θ values for the H sequence were 0.40, 0.28, 0.25, and 0.39. the median values of α for the H sequence were 0.59, 0.015, 0.0028, and 0.0029 h-1. A strong correlation between α and H suggests a velocity dependence of α.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/

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4

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Solute Movement in Uncropped Ridge-Tilled Soil under Natural Rainfall (1999)

Jaynes, Dan B. ; Swan, J. B.

Springer

Soil Science Society of America journal 63 (1999), S. 264-269

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ISSN: 1435-0661

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Type of Medium: Electronic Resource

URL: http://dx.doi.org/

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5

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Evaluation of a Simple Method for Estimating Solute Transport Parameters (2000)

Lee, Jaehoon ; Jaynes, Dan B. ; Horton, Robert

Springer

Soil Science Society of America journal 64 (2000), S. 492-498

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ISSN: 1435-0661

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: im (immobile water content) and α (mass transfer coefficient) which must be determined for a soil before applying the transport model. A simple field method that can estimate both θim and α without measuring extensive breakthrough curves (BTCs) has been presented. The purpose of this paper was to test in laboratory soil columns the simple method of estimating parameters by comparing to the conventional BTC analysis method of parameter estimation. The experiments involved 12-cm-long and 4-cm-diam. columns packed with five different soil materials. The BTCs were performed on each column using a sequential application of four fluorobenzoate tracers. Each tracer was applied for a different length of time. The soil columns were sectioned at the end of the BTC experiments. The simple method gave results of θim and α based upon the sectioned soil samples, and the BTC analysis gave results of θim and α based upon effluent concentrations. The estimates by the two different methods were from the same experiments. Most of the estimated α values using the simple method were within the 95% confidence interval (CI) of the BTC estimates. For 7 of 10 soil columns, the estimates of immobile water fraction, θim/θ, from the simple method were within the 95% CI of the estimates of θim/θ obtained from BTC data. Breakthrough curves calculated using the θim and α values estimated by the simple method were similar to observed BTCs. The simple method provides estimation of θim and α from easy to obtain soil samples in field and can be used as a first approximation to apply the analytical BTC method.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/

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6

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Irrigation management for groundwater quality protection (1990)

Bouwer, Herman ; Dedrick, Allen R. ; Jaynes, Dan B.

Springer

Irrigation and drainage systems 4 (1990), S. 375-383

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ISSN: 1573-0654

Keywords: agricultural chemicals ; best management practices ; groundwater contamination ; irrigation ; preferential flow ; spatial variability

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract Deep percolation flow below agricultural and can transport nitrate and pesticide residues to underlying groundwater. Irrigated agriculture in dry climates can also contaminate groundwater with salt from irrigation water and with trace elements such as selenium leached from the vadose zone. Groundwater contamination by agricultural chemicals can be minimized by using best management practices (BMPs) for crop production (including low-input sustainable agriculture or other source control) and for irrigation. Irrigation systems should be designed and managed for zero or minimum deep percolation during the growing seasons to keep fertilizer and pesticides in the root zone as long as possible. At other times, irrigation efficiencies can be lower to produce enough deep percolation water for leaching salts out of the root zone. Because of spatial variability and preferential flow, however, some deep percolation and movement of chemicals may still occur, even if the irrigation efficiency is 100%. BMPs should be developed to minimize such deep percolation flow.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01103715

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