### Abstract

One of the recognized challenges in chemical extraction of mercury from soil is the diversity of procedures that are currently available in literature and that differ in terms of the extractant solution used, soil:extractant ratio and duration of extraction. Therefore, this study focused on establishing the role of operational parameters for extraction of the available and labile fractions of mercury from soils, considering different soil:extractant ratios and the kinetics of extraction. The suitability of 1.0 mol L− 1 ammonium acetate at pH 7 and 0.1 mol L− 1 HCl as extractants for the available fraction and the extraction of the labile fraction using 0.5 mol L− 1 hydrochloric acid was investigated. No statistical differences were found between ammonium acetate and 0.1 mol L− 1 HCl; therefore both extractants can be used for estimating the available fraction. It was also observed that a soil:extractant ratio of 1.5 g of soil to 100 mL of extractant favors mercury extraction. For the available fraction an extraction of 30 min seems enough, as no further significant change was observed in the quantity of mercury extracted thereafter. For the labile fraction increase the extraction duration to at least 24 h is recommended.

The data was fitted into kinetic models, and it was observed that the two first-order reactions and the diffusion models help to understand the behavior of mercury extraction from soil, clearly showing that in all cases the rate of mercury extraction was faster in the first 10 h and declined after that period. The characteristics of the soil influenced the extraction of mercury, and it was verified that pH and particle size of the soil influenced the mercury extraction process, as results suggested that an acidic soil might have a reduced ability to strongly retain metals and soils with higher porosity showed lower rates of mercury extraction.

Original language | English |
---|---|

Pages (from-to) | 213-223 |

Number of pages | 11 |

Journal | Geoderma |

Volume | 259-260 |

Early online date | 19 Jun 2015 |

DOIs | |

Publication status | Published - 1 Dec 2015 |

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### Keywords

- ammonium acetate
- available fraction
- extraction kinetics
- fractionation
- hydrochloric acid
- labile fraction
- mercury
- soil

### Cite this

*Geoderma*,

*259-260*, 213-223. https://doi.org/10.1016/j.geoderma.2015.06.004

}

*Geoderma*, vol. 259-260, pp. 213-223. https://doi.org/10.1016/j.geoderma.2015.06.004

**Extraction of available and labile fractions of mercury from contaminated soils : the role of operational parameters.** / Reis, Ana Teresa; Lopes, Cláudia B.; Davidson, Christine M.; Duarte, Armando C.; Pereira, Eduarda.

Research output: Contribution to journal › Article

TY - JOUR

T1 - Extraction of available and labile fractions of mercury from contaminated soils

T2 - the role of operational parameters

AU - Reis, Ana Teresa

AU - Lopes, Cláudia B.

AU - Davidson, Christine M.

AU - Duarte, Armando C.

AU - Pereira, Eduarda

PY - 2015/12/1

Y1 - 2015/12/1

N2 - One of the recognized challenges in chemical extraction of mercury from soil is the diversity of procedures that are currently available in literature and that differ in terms of the extractant solution used, soil:extractant ratio and duration of extraction. Therefore, this study focused on establishing the role of operational parameters for extraction of the available and labile fractions of mercury from soils, considering different soil:extractant ratios and the kinetics of extraction. The suitability of 1.0 mol L− 1 ammonium acetate at pH 7 and 0.1 mol L− 1 HCl as extractants for the available fraction and the extraction of the labile fraction using 0.5 mol L− 1 hydrochloric acid was investigated. No statistical differences were found between ammonium acetate and 0.1 mol L− 1 HCl; therefore both extractants can be used for estimating the available fraction. It was also observed that a soil:extractant ratio of 1.5 g of soil to 100 mL of extractant favors mercury extraction. For the available fraction an extraction of 30 min seems enough, as no further significant change was observed in the quantity of mercury extracted thereafter. For the labile fraction increase the extraction duration to at least 24 h is recommended.The data was fitted into kinetic models, and it was observed that the two first-order reactions and the diffusion models help to understand the behavior of mercury extraction from soil, clearly showing that in all cases the rate of mercury extraction was faster in the first 10 h and declined after that period. The characteristics of the soil influenced the extraction of mercury, and it was verified that pH and particle size of the soil influenced the mercury extraction process, as results suggested that an acidic soil might have a reduced ability to strongly retain metals and soils with higher porosity showed lower rates of mercury extraction.

AB - One of the recognized challenges in chemical extraction of mercury from soil is the diversity of procedures that are currently available in literature and that differ in terms of the extractant solution used, soil:extractant ratio and duration of extraction. Therefore, this study focused on establishing the role of operational parameters for extraction of the available and labile fractions of mercury from soils, considering different soil:extractant ratios and the kinetics of extraction. The suitability of 1.0 mol L− 1 ammonium acetate at pH 7 and 0.1 mol L− 1 HCl as extractants for the available fraction and the extraction of the labile fraction using 0.5 mol L− 1 hydrochloric acid was investigated. No statistical differences were found between ammonium acetate and 0.1 mol L− 1 HCl; therefore both extractants can be used for estimating the available fraction. It was also observed that a soil:extractant ratio of 1.5 g of soil to 100 mL of extractant favors mercury extraction. For the available fraction an extraction of 30 min seems enough, as no further significant change was observed in the quantity of mercury extracted thereafter. For the labile fraction increase the extraction duration to at least 24 h is recommended.The data was fitted into kinetic models, and it was observed that the two first-order reactions and the diffusion models help to understand the behavior of mercury extraction from soil, clearly showing that in all cases the rate of mercury extraction was faster in the first 10 h and declined after that period. The characteristics of the soil influenced the extraction of mercury, and it was verified that pH and particle size of the soil influenced the mercury extraction process, as results suggested that an acidic soil might have a reduced ability to strongly retain metals and soils with higher porosity showed lower rates of mercury extraction.

KW - ammonium acetate

KW - available fraction

KW - extraction kinetics

KW - fractionation

KW - hydrochloric acid

KW - labile fraction

KW - mercury

KW - soil

UR - http://www.scopus.com/inward/record.url?scp=84935005161&partnerID=8YFLogxK

UR - http://www.sciencedirect.com/science/journal/00167061

U2 - 10.1016/j.geoderma.2015.06.004

DO - 10.1016/j.geoderma.2015.06.004

M3 - Article

AN - SCOPUS:84935005161

VL - 259-260

SP - 213

EP - 223

JO - Geoderma

JF - Geoderma

SN - 0016-7061

ER -