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| Effects of simulated acid rain on distribution, leachability and bioaccessibility of cadmium in a contaminated soil immobilized by hydroxyapatite |
| Received:December 28, 2015 |
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| KeyWord:simulated acid rain;hydroxyapatite;cadmium;leachability;bioaccessibility |
| Author Name | Affiliation | | CUI Hong-biao | School of Earth and Environment, Anhui University of Science and Technology, Huainan 232001, China
Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China | | MA Kai-qiang | School of Earth and Environment, Anhui University of Science and Technology, Huainan 232001, China | | FAN Yu-chao | School of Earth and Environment, Anhui University of Science and Technology, Huainan 232001, China | | SU Bin-bin | School of Earth and Environment, Anhui University of Science and Technology, Huainan 232001, China | | HU You-biao | School of Earth and Environment, Anhui University of Science and Technology, Huainan 232001, China | | ZHOU Jing | Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China |
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| Abstract: |
| A leaching experiment was conducted to study the distribution, leachability and bioaccessibility of cadmium (Cd) in soil with and without 0.5% (W/W) hydroxyapatite (HAP) amendment, under simulated acid rain (SAR) with pH at 3.5, 4.5 and 5.6. Results showed that soil pH in the control soil was decreased with leaching of SAR, but pH in HAP treated soil increased by about 1 unit compared with the con trol soil. Decreases in SAR pH increased the migration of Cd to the deeper soil column in the control soil, whereas Cd was strongly fixed in HAP treated soil and the Cd concentrations in 0~5 and 5~10 cm soil were 8.54~10.0 and 3.13~3.29 mg·kg-1 higher than those of the control soil, respectively. In the control soil, leaching of SAR increased TCLP-extractable Cd from 0.17~0.23 mg·L-1 at a depth of 0~5 cm to 0.61~0.68 mg·L-1 at a depth of 10~20 cm, whereas it ranged from 0.45 to 0.50 mg·L-1 at a depth of 0~20 cm in the HAP treated soil. Generally, bioaccessible concentrations and bioaccessibility of Cd in gastric and small intestinal phases decreased with decreasing SAR pH in all soil samples. However, the bioaccessible concentration and bioaccessibility of Cd in gastric and small intestinal phases were higher in the HAP treated soil than in the control soil, but bioaccessibility of Cd in small intestinal phase was lower. In gastric and small intestinal phases, the rates of oral ingestion soil Cd to the provisional tolerable monthly intake (PTMI) recommended by WHO in all soils decreased with de creasing of SAR pH, but were higher in the HAP treated soil than in the control soil. These findings indicate that HAP treated soil can effectively increase acid buffer capacity and decrease the leaching loss of Cd. However, the bioaccessibility and health risk from the oral ingestion of soil Cd in HAP treated soil are higher than in the control soil. Thus more attentions should be paid when HAP is used to immobilize Cd in acidic soils. |
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