HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Figures Only Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (11) Citing Articles via Google Scholar Google Scholar Articles by Celis, R. Articles by Koskinen, W. C. Search for Related Content PubMed Articles by Celis, R. Articles by Koskinen, W. C. GeoRef GeoRef Citation Agricola Articles by Celis, R. Articles by Koskinen, W. C.

DIVISION S-2-SOIL CHEMISTRY

Characterization of Pesticide Desorption from Soil by the Isotopic Exchange Technique

^a Dep. of Soil, Water and Climate, St. Paul, MN USA
^b Soil and Water Management Research Unit, USDA-ARS, 1991 Upper Buford Circle, 439 Borlaug Hall, St. Paul, MN 55108 USA

koskinen{at}soils.umn.edu

	ABSTRACT

TOP ABSTRACT INTRODUCTION Materials and methods NOTES Results Discussion Summary REFERENCES

 
The reversibility of pesticide sorption–desorption in soil is of fundamental importance in the understanding of the fate of these agrochemicals in the environment. We used an isotopic exchange method to characterize the irreversibility of the sorption–desorption process of the insecticide imidacloprid (1-[(6-chloro-3-pyridinyl)-methyl]-Nnitro-2-imidazolidinimine) and its degradation product imidacloprid-urea (1-[(6-chloro-3-pyridinyl)-methyl]-2-imidazolidinone) on a silty clay loam (SiCL) soil, and that of the metabolite imidacloprid-guanidine (1-[6-chloro-3-pyridinyl)methyl]-4,5-dihydro-1H-imidazol-2-amine) on a loamy sand (LS) soil. The exchange between ¹²C-pesticide molecules and ¹⁴C-labeled pesticide molecules in soil suspensions preequilibrated for 24 h was monitored and indicated that a fraction of the sorbed chemicals was resistant to desorption. A two-compartment model was applied to describe the experimental sorption data points of the sorption isotherms as the sum of a reversible component and a nondesorbable, irreversible component. The quantitative estimation of the irreversible and reversible components of sorption, experimentally derived from isotopic exchange experiments, indicated degree of irreversibility (percentage irreversibly bound) in the order: imidacloprid–SiCL soil (6–32%) < imidacloprid urea–SiCL soil (15–23%) < imidacloprid guanidine–LS soil (32–51%), with greater irreversibility at lower pesticide concentration. Increasing the preequilibration time and decreasing pH in the imidacloprid–SiCL soil system resulted in increased sorption irreversibility. The irreversible component of sorption determined by the isotopic exchange technique also allowed accurate prediction of the sorption–desorption hysteretic behavior during successive desorption cycles for all three soil–pesticide systems studied. The isotopic exchange technique appears to be a suitable method to quantitatively characterize pesticide desorption from soil, allowing prediction of hysteresis during sorption–desorption experiments.

Abbreviations: LS, loamy sand • SiCL, silty clay loam

	INTRODUCTION

TOP ABSTRACT INTRODUCTION Materials and methods NOTES Results Discussion Summary REFERENCES

 
SORPTION

is a major process influencing the fate of pesticides in soil. Laboratory sorption isotherm data are used in mathematical models as indicators of pesticide mobility to predict pesticide availability and potential groundwater contamination. The sorption–desorption process is often simplified in these mathematical models by assuming that reversible, instantaneous equilibrium occurs, that is, the same isotherm applies for pesticide sorption and desorption. However, for most soil–pesticide systems, laboratory sorption–desorption experiments appear to reflect only partially reversible behavior (Di Toro and Horzempa, 1982).

Although the presence of hysteresis has been attributed to a number of experimental artifacts during the desorption experiment (Koskinen et al., 1979; Calvet, 1980, Clay et al., 1988), sufficient evidence exists to suggest that hysteretic behavior can be due to a portion of sorbed pesticide that is very strongly or irreversibly bound and does not readily desorb from soil (Karickhoff, 1980; Wauchope and Myers, 1985; Clay and Koskinen, 1990). Based on the assumption that a strongly bound pesticide would not be available for desorption, some authors have fit desorption isotherm data to equations based on two-compartment models that attributed some of the observed hysteresis to nondesorbable molecules (Di Toro and Horzempa, 1982; Barriuso et al., 1992; Benoit et al., 1996); however, direct experimental estimates of the fraction of a pesticide that is nondesorbable are scarce. Even more scarce are attempts to use these estimates to explain hysteretic behavior of desorption isotherms (Clay and Koskinen, 1990).

There is a need to account for sorption–desorption hysteresis in a quantitative and consistent way to better incorporate laboratory sorption–desorption data into models of pesticide behavior in soil. In a recent paper, we presented an isotopic exchange method combined with batch equilibration experiments to quantitatively characterize the irreversibility of pesticide sorption–desorption by soil (Celis and Koskinen, 1999). Monitoring of the exchange between ¹²C-pesticide molecules and ¹⁴C-labeled pesticide molecules in preequilibrated soil suspensions allowed characterization of pesticide exchange kinetics and estimation of amounts of sorbed pesticide that did not participate in reversible sorption–desorption equilibria.

In the present study, three soil–pesticide systems were selected and the isotopic exchange technique described by Celis and Koskinen (1999) was applied to quantify the irreversibility of the sorption–desorption process for each system. The three pesticide–soil systems selected were imidacloprid and imidacloprid-urea on a SiCL soil and imidacloprid guanidine on a LS soil. They were chosen based on previous results indicating different degrees of sorption–desorption hysteresis (Cox et al., 1997). Mechanisms responsible for irreversible sorption behavior were not investigated. Emphasis was placed on the quantitative description of the irreversibility of pesticide sorption using the isotopic exchange technique and incorporation of the information obtained to describe hysteresis of the sorption–desorption isotherms obtained in batch equilibration experiments. Detailed information about the characteristics of the chemicals used and their sorption–desorption behavior in different soils has previously been reported by Cox et al. (1997).

	Materials and methods

TOP ABSTRACT INTRODUCTION Materials and methods NOTES Results Discussion Summary REFERENCES

 
Chemicals and Soils
Pure analytical standards (chemical purity > 99%) of imidacloprid, imidacloprid-urea, imidacloprid-guanidine, and radiochemical materials (radiochemical purity > 97%) were donated by Bayer Corp. (Stilwell, KS).¹ Soils from the 0- to 15-cm depth of a Drummer (fine-silty, mixed, superactive, mesic Typic Endoaquoll) SiCL from Indiana and a LS from Michigan were used. The soils were air dried and passed through a 2-mm-diameter sieve prior to use. Physicochemical characteristics of the soils are given in Table 1 . Soil texture was determined by the hydrometer method (Gee and Bauder, 1986). Soil pH was measured in a 1:2 (w/w) soil/deionized water mixture. The organic C content was estimated by dichromate oxidation (Nelson and Sommers, 1982).

For ¹⁴C-analysis, 1-mL aliquots of the clear supernatants were mixed with 6 mL of Ecolite scintillation cocktail (ICN, Costa Mesa, CA), and the radioactivity in solution, R_e (Bq), was measured by liquid scintillation counting using a 1500 Packard Liquid Scintillation Analyzer (Packard Instruments Co., Downers Grove, IL). The radioactivity on the soil, R_s (Bq), was calculated from the difference R_i - R_e. The total amount of chemical in solution, C_e (mg L^-1), and sorbed to the soil, C_s (mg kg^-1), were calculated from R_e and R_s using the specific activity of each chemical.

Desorption
Desorption was measured after sorption by replacing the supernatant removed for the sorption analysis with the same volume of either 0.01 M CaCl₂ or soil extract. The soil extract was made by mixing 2 g of soil with 10 mL of 0.01 M CaCl₂ and equilibrating for 24 h, as described above. The soil slurry was centrifuged and the supernatant used as replacement solution. After replacement, the suspensions were shaken at 21 ± 2°C for 24 h, centrifuged, and the supernatant removed for analysis. This desorption cycle was repeated five times.

Isotopic Exchange Experiments
The isotopic exchange experiments were performed following the method described by Celis and Koskinen (1999). For every equilibrium point of the sorption experiment, additional tubes (A and B) were prepared. The amounts of soil, solution, and initial pesticide in Tubes A and B were exactly the same and identical to those used to obtain the equilibrium point in the sorption experiment; however, Tube A contained only ¹²C-pesticide, whereas Tube B contained 70 Bq mL^-1 of ¹⁴C-pesticide. Initial solutions were carefully prepared to ensure that they contained exactly the same total pesticide concentration .

The suspensions were shaken at 21 ± 2°C for 24 h, then centrifuged at 3000 g for 30 min. The supernatant of Tube A (7 g) was replaced with the supernatant of Tube B (7 g) and vice versa. Immediately after supernatant exchange, Tube A was identical to B except that Tube A contained ¹⁴C-pesticide only in solution phase, whereas tube B contained ¹⁴C-pesticide only in sorbed phase (plus the ¹⁴C remaining in the 3 g of solution that was not removed). The soil and solution were reequilibrated and the kinetics of the ¹⁴C-pesticide exchange between the solid and solution phases was monitored by measuring the decrease in ¹⁴C-pesticide in solution with time in Tube A and the increase in ¹⁴C-pesticide in solution with time in Tube B (Celis and Koskinen, 1999). Isotopic exchange kinetics for the different systems were obtained at an initial pesticide concentration of 0.3 mg L^-1. Additionally, the extent of isotopic exchange was determined after 24 h for every initial pesticide concentration used.

Data Analysis
Sorption–desorption data were fit to the linearized form of the Freundlich equation:

(1)

where K_f and 1/n_f are the empirical Freundlich constants. Hysteresis coefficients, H, for the desorption isotherms were calculated according to:

(2)

where 1/n_fd is the Freundlich constant for the desorption isotherm (O'Connor et al., 1980; Barriuso et al., 1994).

In the isotopic exchange experiments, just after supernatant exchange, ¹⁴C-molecules were present only in one of the phases, so redistribution of these ¹⁴C-molecules would occur according to:

where R^'_e and R^'_s are the amounts of ¹⁴C-pesticide (Bq) in solution and sorbed to the soil, respectively, at a given time after supernatant exchange, and is the corresponding partition constant for ¹⁴C-pesticide. R^'_e will decrease with time in Tube A and increase with time in Tube B until isotopic exchange equilibrium is reached. If sorption is a rapid, reversible process and all the pesticide sorbed on soil is in equilibrium with the pesticide in solution, then K' would agree with the equilibrium partition constant , measured in the preequilibration step, that is:

(3)

Thus, Eq. [3] can be used to predict the distribution of the ¹⁴C-pesticide during the isotopic exchange, assuming rapid, reversible behavior.

	Results

TOP ABSTRACT INTRODUCTION Materials and methods NOTES Results Discussion Summary REFERENCES

 
Sorption Kinetics
Sorption was rapid for all three soil–pesticide systems; total sorption increased by <10% between 24 and 72 h (Fig. 1) . Controls without soil showed no pesticide losses due to sorption on glass or volatilization during a 72-h period (Fig. 1), so differences between initial and equilibrium pesticide concentrations were assumed to be sorbed. Some sorption occurred at equilibration times longer than 24 h in imidacloprid urea–SiCL soil and in imidacloprid guanidine–LS soil systems (Fig. 1).

View larger version (20K): [in this window] [in a new window]   Fig. 1 Sorption kinetics for soil–pesticide systems. Controls without soil (open circles). Kinetics on soil (solid circles). Error bars are smaller than symbols

View larger version (29K): [in this window] [in a new window]   Fig. 2 Kinetics of the isotopic exchange in soil–pesticide suspensions preequilibrated for 24 h . (A–C) Kinetics of 14C-sorption on soil. (D–F) Kinetics of 14C-desorption from soil. Dashed lines are the radioactivities expected from the equilibrium partition constant, K, measured in the preequilibration step

In isotopic exchange experiments carried out at different pesticide concentrations, ¹⁴C in solution was sorbed on soil to the same extent as observed during the preequilibration step, independent of the pesticide concentration used (Table 2) . In contrast, reduced desorption of ¹⁴C-imidacloprid urea and imidacloprid-guanidine (71–90% of expected) was observed. For every concentration tested, the resistance to desorption increased in the order: imidacloprid–SiCL < imidacloprid urea–SiCL < imidacloprid guanidine–LS, with lower desorption at low pesticide concentrations (i.e., <0.5 mg L^-1). The effect of increasing the soil/solution ratio in imidacloprid guanidine–LS soil system was similar to that of decreasing the pesticide concentration, with a reduction in desorbability of the ¹⁴C-imidacloprid guanidine during the isotopic exchange (Table 2).

View larger version (18K): [in this window] [in a new window]   Fig. 3 Sorption–desorption isotherms for soil–pesticide systems. Solid lines are the Freundlich-fit sorption isotherms. Numbers beside each equilibrium sorption point indicate the percentage of nondesorbable pesticide, Rs-irr, determined in isotopic exchange experiment

View larger version (19K): [in this window] [in a new window]   Fig. 4 Imidacloprid guanidine sorption–desorption isotherm on loamy sand soil at 5 g/10 mL soil/solution ratio. The solid line is the Freundlich-fit sorption isotherm. Numbers indicate the percentage of nondesorbable pesticide, Rs-irr, determined in isotopic exchange experiment

	Discussion

TOP ABSTRACT INTRODUCTION Materials and methods NOTES Results Discussion Summary REFERENCES

The slow sorption of imidacloprid urea on SiCL soil and imidacloprid guanidine on LS soil observed in the sorption kinetic experiments can account for some of the reduced ¹⁴C-release from the soils during the isotopic exchange experiments, since accumulation of ¹⁴C would occur during the second 24 h of equilibration (Celis and Koskinen, 1999). However, preliminary sorption kinetic results showed that sorption during the second 24 h of shaking was only 2% of the imidacloprid urea and 6% of the imidacloprid guanidine sorbed within the first 24 h. Furthermore, significant additional sorption would have resulted in a decrease of the ¹⁴C in solution at increased periods of isotopic exchange, which was not observed in the isotopic desorption kinetics (Fig. 2). It seems, therefore, that other processes may have been involved in the reduced ¹⁴C release during the isotopic exchange. These processes may include slow desorption kinetics, trapping of the ¹⁴C into micropores of soil clay and organic matter, and chemical transformation (degradation) to more strongly sorbed species (Karickhoff and Morris, 1985; Xue and Selim, 1995).

Independent of the specific nature of the processes involved, ¹⁴C-desorption kinetic results revealed that, after 10 h of isotopic exchange, the amount of desorbed ¹⁴C reached a constant value that is lower than expected from partition of the chemical during the 24-h preequilibration step (Fig. 2). Therefore the systems behaved as if a fraction of the pesticide sorbed during the preequilibration step was not available for desorption and, hence, did not participate in the reversible sorption–desorption process on the time scale of the isotopic exchange experiment. Based on this assumption, Celis and Koskinen (1999) have proposed that the extent of isotopic exchange can be given by a modified form of Eq. [3] that takes into account the radioactivity in soil that is not participating in the reversible sorption equilibrium, R_s-irr:

(4)

R_s-irr can be calculated from the ¹⁴C distribution in the 24-h preequilibration (R_s and R_e) and that after isotopic exchange and R^'_e).

The values of R_s-irr calculated after 24 h of isotopic exchange using Eq. [4] and expressed as percentages of the total radioactivity sorbed in the preequilibration step (R_s) showed that at similar concentrations the sorption irreversibility increased in the order: imidacloprid–SiCL < imidacloprid urea–SiCL < imidacloprid guanidine–LS, with increased irreversibility at lower pesticide concentrations (Table 2). The decrease of R_s-irr with increased pesticide concentration suggested that the number of sites resistant to desorption is limited and progressive saturation of those sites occurs at high concentrations (Celis and Koskinen, 1999). This was supported by the increase in R_s-irr after increasing the soil/solution ratio in the imidacloprid guanidine–LS system (Table 2). At high soil/solution ratio, the relative amount of sites compared with the amount of pesticide in solution is also increased, so that the effect was similar to decreasing pesticide concentration.

It has also been pointed out that with increased residence time, the sorbed pesticide may become more resistant to release (McCall and Agin, 1985; Pignatello et al., 1993; Scheidegger and Sparks, 1996). Table 3 shows that increasing the preequilibration time from 24 to 120 h indeed resulted in a reduction in desorption of ¹⁴C-imidacloprid during the 24 h of isotopic exchange. It should be noted that no further sorption of imidacloprid during the additional 96-h preequilibration time was observed. Also, very little degradation of imidacloprid after 2 wk of incubation has been reported (Cox et al., 1998a). Therefore, it seems that the fraction of the sorbed imidacloprid that is resistant to desorption increases with increased residence time. A similar effect was observed after decreasing the pH for the sorption experiment from 5.9 to 2.1 (Table 3). In this case, contribution of a cationic-exchange mechanism to imidacloprid sorption at low pH (Cox et al., 1998b) could have contributed to reduce the desorbability of the sorbed imidacloprid on soil.

(5)

where C_sd is the amount of pesticide sorbed at the equilibrium concentration C_e during desorption, K_f-rev and 1/n_f-rev are the Freundlich coefficients for the reversible component of the sorption isotherm, and C_s-irr is the amount of irreversibly bound pesticide for the sorption equilibrium point from which desorption was carried out. Figures 3 and 4 show that, using this model, the prediction (dashed lines) of the desorption isotherms experimentally obtained for the different systems studied is excellent. It should be emphasized that, in contrast to estimations made in previous work (Barriuso et al., 1992; Benoit et al., 1996; Di Toro and Horzempa, 1982), the irreversible component of sorption here is derived from an experimental procedure that is independent of the desorption data obtained in batch equilibration experiments. The irreversible component of sorption derived from the isotopic exchange experiments thus appears as a suitable quantitative estimate of the irreversibility of pesticide sorption during successive desorption cycles.

	Summary

TOP ABSTRACT INTRODUCTION Materials and methods NOTES Results Discussion Summary REFERENCES

 
An isotopic exchange method was used to characterize the irreversibility of pesticide sorption–desorption in three soil–pesticide systems with different hysteretic behavior. The exchange between ¹²C-pesticide molecules and ¹⁴C-pesticide molecules in soil suspensions preequilibrated for 24 h was monitored and indicated that a fraction of the sorbed pesticide was resistant to desorption. A two-compartment model was applied to describe the experimental sorption data points of the sorption isotherms as the sum of a reversible component and a nondesorbable, irreversible component. A quantitative estimate of the irreversible and reversible components for each equilibrium sorption data point was experimentally derived from the isotopic exchange experiments. The two-compartment model allowed accurate prediction of the sorption–desorption hysteretic behavior during successive desorption cycles for all three soil–pesticide systems studied. The specific nature of the processes responsible for the observed hysteretic behavior remains unknown, although changes in solution composition during desorption were not a cause of the observed hysteresis. Thus, irreversible binding of the pesticide to soil particles, slow diffusion from restricted sorption sites, trapping in micropores of soil clay and organic matter, and chemical transformation to more strongly sorbed species can be speculated to contribute to the resistant component of sorption. The isotopic exchange technique used appears to be a suitable alternative method to characterize pesticide desorption from soil, allowing quantitative characterization of the irreversibility of pesticide sorption as well as prediction of hysteresis during successive desorption cycles.Scribner Benzing Sun Boyd 1992

	ACKNOWLEDGMENTS

 
We thank Bayer Corp. for kindly supplying the analytical and radioactive chemicals. R. Celis also thanks the Spanish Ministry of Education and Culture for his PFPI fellowship.

	NOTES

TOP ABSTRACT INTRODUCTION Materials and methods NOTES Results Discussion Summary REFERENCES

 
¹ Mention of a company or trade name is for information only and does not imply recommendation by USDA-ARS.

Received for publication October 5, 1998.

	REFERENCES

TOP ABSTRACT INTRODUCTION Materials and methods NOTES Results Discussion Summary REFERENCES

 

• Barriuso E., Baer U., Calvet R. Dissolved organic matter and adsorption–desorption of dimefuron, atrazine, and carbetamide by soils. J. Environ. Qual. 1992;21:359-367.[Abstract/Free Full Text]
• Barriuso E., Laird D.A., Koskinen W.C., Dowdy R.H. Atrazine desorption from smectites. Soil Sci. Soc. Am. J. 1994;58:1632-1638.[Abstract/Free Full Text]
• Benoit P., Barriuso E., Houot S., Calvet R. Influence of the nature of soil organic matter on the sorption–desorption of 4-chlorophenol, 2,4-dichlorophenol and the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Eur. J. Soil Sci. 1996;47:567-578.
• Calvet R. Adsorption–desorption phenomena. In: Hance R.J., ed. Interactions between herbicides and the soil. New York: Academic Press, 1980:1-30.
• Celis R., Koskinen W.C. An isotopic exchange method for the characterization of the irreversibility of pesticide sorption–desorption in soil. J. Agric. Food Chem. 1999;47:782-790.[Medline]
• Clay S.A., Allmaras R.R., Koskinen W.C., Wyse D.L. Desorption of atrazine and cyanazine from soil. J. Environ. Qual. 1988;17:719-723.[Abstract/Free Full Text]
• Clay S.A., Koskinen W.C. Characterization of alachlor and atrazine desorption from soils. Weed Sci. 1990;38:74-80.
• Cox L., Koskinen W.C., Yeng P.Y. Sorption–desorption of imidacloprid and its metabolites in soils. J. Agric. Food Chem. 1997;45:1468-1472.
• Cox L., Koskinen W.C., Yeng P.Y. Changes in sorption of imidacloprid with incubation time. Soil Sci. Soc. Am. J. 1998;62:342-347 a.[Abstract/Free Full Text]
• Cox L., Koskinen W.C., Celis R., Yeng P.Y., Hermosin M.C., Cornejo J. Sorption of imidacloprid on soil clay mineral and organic components. Soil Sci. Soc. Am. J. 1998;62:911-915 b.[Abstract/Free Full Text]
• Di Toro D.M., Horzempa L.M. Reversible and resistant components of PCB adsorption–desorption isothems. Environ. Sci. Technol. 1982;16:594-602.
• Gee G.W., Bauder J.W. Particle-size analysis. In: Klute A., ed. Methods of soil analysis. Madison, WI: Part 1. 2nd ed. Agron. Monogr. 9. ASA and SSSA, 1986:383-409.
• Karickhoff S.W. Sorption kinetics of hydrophobic pollutants in natural sediments. In: Baker R.A., ed. Contaminants and sediments. Ann Arbor, MI: Ann Arbor Science Publ, 1980:193-205.
• Karickhoff S.W., Morris K.R. Sorption dynamics of hydrophobic pollutants in sediment suspensions. Environ. Toxicol. Chem. 1985;4:469-479.
• Koskinen W.C., O'Connor G.A., Cheng H.H. Characterization of hysteresis in the desorption of 2,4,5-T from soils. Soil Sci. Soc. Am. J. 1979;43:871-874.[Abstract/Free Full Text]
• McCall P.J., Agin G.L. Desorption kinetics of picloram as affected by residence time in the soil. Environ. Toxicol. Chem. 1985;4:37-44.
• Nelson D.W., Sommers L.E. Total carbon, organic carbon and organic matter. In: Page A.L., ed. Methods of soil analysis. Madison, WI: Part 2. 2nd ed. Agron. Monogr. 9. ASA and SSSA, 1982:539-579.
• O'Connor G.A., Wierenga H.H., Cheng H.H., Doxtader K.G. Movement of 2,4,5-T through large soil columns. Soil Sci. 1980;130:157-162.
• Pignatello J.J., Ferrandino F.J., Huang L.Q. Elution of aged and freshly added herbicides from a soil. Environ. Sci. Technol. 1993;27:1563-1571.
• Scheidegger A.M., Sparks D.L. A critical assessment of sorption–desorption mechanisms at the soil mineral/water interface. Soil Sci. 1996;161:813-831.
• Scribner S.L., Benzing T.R., Sun S., Boyd S.A. Desorption and bioavailability of aged simazine residues in soil from a continuous corn field. J. Environ. Qual. 1992;21:115-120.
• Wauchope R.D., Myers R.S. Adsorption–desorption kinetics of atrazine and linuron in freshwater-sediment aqueous slurries. J. Environ. Qual. 1985;14:132-136.[Abstract/Free Full Text]
• Xue S.K., Selim H.M. Modeling adsorption–desorption kinetics of alachlor in a Typic Fragiudalf. J. Environ. Qual. 1995;24:896-903.[Abstract/Free Full Text]

This article has been cited by other articles:

				R. Celis, M. Real, M. C. Hermosin, and J. Cornejo Desorption, Persistence, and Leaching of Dibenzofuran in European Soils Soil Sci. Soc. Am. J., June 21, 2006; 70(4): 1310 - 1317. [Abstract] [Full Text] [PDF]

This Article Abstract Figures Only Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (11) Citing Articles via Google Scholar Google Scholar Articles by Celis, R. Articles by Koskinen, W. C. Search for Related Content PubMed Articles by Celis, R. Articles by Koskinen, W. C. GeoRef GeoRef Citation Agricola Articles by Celis, R. Articles by Koskinen, W. C.