Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - The effect of the ferrihydrite dissolution/transformation process on mobility of arsenic in soils
T2 - investigated by coupling a two-step sequential extraction with the diffusive gradient in the thin films (DGT) technique
AU - Zhang, T.
AU - Zeng, X.
AU - Zhang, H.
AU - Lin, Q.
AU - Su, S.
AU - Wang, Y.
AU - Bai, L.
AU - Wu, C.
PY - 2019/10/15
Y1 - 2019/10/15
N2 - Ferrihydrite has been prevalently used in soil remediation as an effective amendment for in situ immobilization of arsenic (As). However, its poorly crystalline structure is unstable and can pose the risk of re-releasing As into soil. In this study, sequential extraction was coupled with a newly-established method, chelex-metsorb diffusive gradient in thin films (DGT), to study the ferrihydrite transformation/dissolution process and its effect on the mobility of arsenic in soil. Experiments in this work found that high soil moisture (70% SWHC) with a low soil redox potential (Eh) can significantly increase the rate of the ferrihydrite transformation/dissolution process compared to 30% SWHC. Soils with low pH and high available iron (Fe) content may also accelerate ferrihydrite transformation/dissolution, while soils with high clay fraction and high soil total organic matter (STOM) may inhibit the process. The amount of arsenic adsorption can also affect ferrihydrite transformation, even exceeding the effect of soil pH and dissolved Fe. Arsenic release was clearly observed in all three soils across all treatments, and it was also affected by changes in soil redox potential. More arsenic was released at high soil moisture (70% SWHC) roughly 7–15 d after the release of Fe. In addition, a partial arsenic fraction was transformed, along with ferrihydrite, from a combined As (F1–As) amorphous phase to combined As (F2–As) well-crystallized phase. These results suggested that ferrihydrite transformation/dissolution can affect the mobility of arsenic and that this phenomenon is more extreme at higher soil moisture levels.
AB - Ferrihydrite has been prevalently used in soil remediation as an effective amendment for in situ immobilization of arsenic (As). However, its poorly crystalline structure is unstable and can pose the risk of re-releasing As into soil. In this study, sequential extraction was coupled with a newly-established method, chelex-metsorb diffusive gradient in thin films (DGT), to study the ferrihydrite transformation/dissolution process and its effect on the mobility of arsenic in soil. Experiments in this work found that high soil moisture (70% SWHC) with a low soil redox potential (Eh) can significantly increase the rate of the ferrihydrite transformation/dissolution process compared to 30% SWHC. Soils with low pH and high available iron (Fe) content may also accelerate ferrihydrite transformation/dissolution, while soils with high clay fraction and high soil total organic matter (STOM) may inhibit the process. The amount of arsenic adsorption can also affect ferrihydrite transformation, even exceeding the effect of soil pH and dissolved Fe. Arsenic release was clearly observed in all three soils across all treatments, and it was also affected by changes in soil redox potential. More arsenic was released at high soil moisture (70% SWHC) roughly 7–15 d after the release of Fe. In addition, a partial arsenic fraction was transformed, along with ferrihydrite, from a combined As (F1–As) amorphous phase to combined As (F2–As) well-crystallized phase. These results suggested that ferrihydrite transformation/dissolution can affect the mobility of arsenic and that this phenomenon is more extreme at higher soil moisture levels.
KW - As
KW - DGT
KW - Ferrihydrite
KW - pH
KW - Soils
KW - Transformation/dissolution
KW - Arsenic
KW - Extraction
KW - Positive ions
KW - Redox reactions
KW - Soil conservation
KW - Soil pollution
KW - Thin films
KW - Crystalline structure
KW - Diffusive gradients
KW - Ferrihydrites
KW - Sequential extraction
KW - Situ immobilization
KW - Soil redox potential
KW - Total organic matter
KW - Soil moisture
U2 - 10.1016/j.geoderma.2019.05.042
DO - 10.1016/j.geoderma.2019.05.042
M3 - Journal article
VL - 352
SP - 22
EP - 32
JO - Geoderma
JF - Geoderma
SN - 0016-7061
ER -