• Title/Summary/Keyword: desorption-resistant fraction

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Desorption Characteristics and Bioavailability of Zn to Earthworm in Mine Tailings (광미내 Zn의 탈착 특성과 지렁이에 대한 생이용성)

  • Oh, Sang-Hwa;Shin, Won-Sik
    • Journal of Soil and Groundwater Environment
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    • v.16 no.4
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    • pp.38-52
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    • 2011
  • Sorption and sequential desorption experiments were conducted for Zn using a natural soil (NS) in background status by aging (1, 30 and 100 days). The sorption isotherm showed that Zn had high sorption capacity but low sorption affinity in NS. Sequential desorption was biphasic with appreciable amount of sorbed Zn residing in the desorption-resistant fraction after several desorption steps. The biphasic desorption behavior of Zn was characterized by a biphasic desorption model that includes a linear term to represent labile or easily-desorbing fraction and a Langmuirian-type term to represent desorption-resistant fraction. The biphasic desorption model indicated that the size of the maximum capacity of desorption-resistant fraction ($q^{irr}_{max}$) increased with aging in NS. Desorption kinetics and desorption-resistance of Zn in the soils collected from mine tailings (MA, MB and MC collected from surface, subsurface soils and mine waste, respectively) were investigated and compared to the bioavailability to earthworm (Eisenia fetida). Desorption kinetic data of Zn were fitted to several desorption kinetic models. The ratio ($q_{e,d}/q_0$) of remaining Zn at desorption equilibrium ($q_{e,d}$) to initial sorbed concentration ($q_0$) was in the range of 0.53~0.90 in the mine tailings which was higher than that in NS, except MA. The sequential desorption from the mine tailings with 0.01M Na$NO_3$ and 0.01M $CaCl_2$ showed that appreciable amounts of Zn are resistant to desorption due to aging or sequestration. The SM&T (Standard Measurements and Testing Programme of European Union) analysis showed that the sum of oxidizable (Step III) and residual (Step IV) fractions of Zn was linearly related with its desorption-resistance ($q^{irr}_{max}$) determined by the sequential desorption with 0.01M Na$NO_3$ ($R^2$= 0.9998) and 0.01M $CaCl_2$ ($R^2$= 0.8580). The earthworm uptake of Zn and the desorbed amount of Zn ($q_{desorbed}$ = $q_0-q_{e,d}$) in MB soil were also linearly related ($R^2$ = 0.899). Our results implicate that the ecological risk assessment of heavy metals would be possible considering the relation between desorption behaviors and bioavailability to earthworm.

Sorption and desoption behaviors of PAHs in soil and sediments

  • Wang, Qiliang;Shin, Sik;Song, Dong-Ik
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • pp.277-284
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    • 2004
  • Batch experiments were conducted to investigate the sorption and desorption behaviors of PAHs (naphthalene, phenanthrene and pyrene) in soils. Three different soils montmorillonite KSF (foc =0.14%), masato (foc =0.08%), and diatomite (foc =0.007%) were investigated. The results of sorption-desorption experiment indicate that the sorption affinity of PAHs was in the order of montmorillonite > masato > diatomite. The Freundlich model was well fitted to the sorption and desorption data. Sorption affinity increased as loc increased. Desorption of PAHs from soils was biphasic composed of reversible and irreversible compartments. Desorption-resistance of phenanthrene in soils was also determined. The biphasic desorption model was used to explain desorption-resistance of phenanthrene in soils. The linear term represents reversible sorption fraction and Langmuinian-type term represents desorption-resistant fraction.

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Desorption-Resistance of Hydrophobic Organic Compounds in Natural Soils

  • Shin, Won-Sik
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • pp.26-29
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    • 2001
  • Sorption/desorption Study was conducted to determine desorption-resistance hydrophobic organic compounds in natural soils with low organic carbon content. Sorption/desorption characteristics of chlorobenzene and phenanthrene for both PPI (Petro Processors, Inc. Superfund site) and BM (Bayou Manchac), soils were investigated. Desorption was biphasic including reversible and desorption-resistant compartments. The biphasic sorption parameters indicated the presence of appreciable size of desorption-resistant phase in these soils. A finite maximum capacity of desorption-resistant fraction (equation omitted) was observed after several desorption steps. The apparent organic carbon based Partition coefficient, K(equation omitted) was 10$^{4.92{\pm}0.27}$ for PPI soil and 10$^{4.92{\pm}0.27}$ for BM soil, respectively. The difference in K(equation omitted) was attributed to different characteristics in soil organic matter. The results suggest that desorption-resistance should be considered in remediation and risk assessments in natural soils and sediments.

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Sequestration of Organic Pollutants in the Environments: Implications on Bioavailability and Bioremediation

  • Nam, Kyoungphile
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • pp.107-118
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    • 2000
  • For the last several decades, the fate of organic pollutants has been extensively studied in natural environments with emphasis on sorption and desorption phenomena. Although the mechanisms involved are not clear yet there is a consensus about the existence of hysteresis in the sorption and desorption of organic pollutants. Furthermore, it is found that hysteresis is the outcome of slow nonequilibrium sorption of organic pollutants, which results in the formation of desorption-resistant fractions of the pollutants. Desorption-resistant fractions may increase as a function of the residence time of the pollutants in the environments. Field monitoring data show a slow but continuous decline of chemicals applied to soil, followed by little or no subsequent disappearance. One plausible explanation for such resistance to biodegradation, desorption, or extraction can be attributed the gradual movement of organic pollutants to less accessible remote sites inside the matrix with time. This phenomenon has been termed sequestration or aging. The fact that some pollutants are sequestered in soil with time may have a great impact on bioremediation and risk assessment, Some portion of the resistant pollutants may still be present in the environments after bioremediation. It requires vigorous means to completely remove the aged portion that may not be further bioavailable. However, precaution should be taken since aging is not always evident. Aging seems to be soil and chemical specific.

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