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| Differences in the aging of added lead in three typical soils |
| Received:January 10, 2019 |
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| KeyWord:added lead;red earth;black soil;fluvo-aquic soil;aging;extractant |
| Author Name | Affiliation | E-mail | | SUN Shuo | Institute of Agriculture Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China | | | LI Ju-mei | Institute of Agriculture Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China | lijumei@caas.cn | | MA Yi-bing | Institute of Agriculture Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China | | | ZHAO Hui-wei | The Semi-arid Agriculture Engineering & Technology Research Center, Shijiazhuang 050051, China | |
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| Abstract: |
| To investigate the aging of added lead (Pb) in different soils, three typical soils (red earth, black soil, and fluvo-aquic soil) were dosed with soluble Pb and stored for 1, 3, 9, 30, 100, and 360 days. Three extractants (0.01 mol·L-1 CaCl2, 0.05 mol·L-1 EDTA-2Na, and 0.43 mol·L-1 HNO3) were used to extract available Pb after different incubation periods. The results indicated that the extraction efficiency of Pb added to soils was related to the type of extractant and the properties of soil. The extraction efficiencies of 0.43 mol·L-1 HNO3 (81%~99%) and 0.05 mol·L-1 EDTA-2Na (66%~99%) for Pb added to soils were much higher than that of 0.01 mol·L-1 CaCl2 (0.002%~13.8%), which was much higher in red earth (7.2%~13.8%) than in the other two soils (black soil and fluvo-aquic soil, 0.002%~0.037%). With 0.05 mol·L-1 EDTA-2Na, the extraction efficiency followed the order of black soil>red earth>fluvo-aquic soil. The dynamic aging curves of Pb extracted using 0.01 mol·L-1 CaCl2 and 0.05 mol·L-1 EDTA-2Na showed that aging occurred in the short-term in the three soils, then the aging rate decreased with time; however, there was no significant change in the extraction efficiency of 0.43 mol·L-1 HNO3 over time. The concentrations of 0.05 mol·L-1 EDTA-2Na extractable Pb in red earth and fluvo-aquic soil initially decreased rapidly for 30 days, then changed slowly between 100 and 360 days to reach a pseudo-equilibrium. In black soil, the aging process was relatively slower; the times to reach a pseudo-equilibrium for red earth, fluvo-aquic soil, and black soil were 100 days, 360 days, and longer than 360 days, respectively. The aging curve of Pb in soil fitted well to a first order exponential decay equation. The aging rates of EDTA-extractable lead showed a highly significant negative correlation with soil pH and electrical conductivity, and a significant positive correlation with the content of iron-aluminum oxide in the soil. |
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