Journal of Ecology and Rural Environment ›› 2018, Vol. 34 ›› Issue (1): 87-95.doi: 10.11934/j.issn.1673-4831.2018.01.011

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Distribution of Heavy Metals by Form for Precise Remediation of Polluted Farmland Soil

WANG Jia-jia1, LI Xiang1, LUO Nan1, HE Yue2, LIU Yong-bing1, LU Yi-fu3, MIAO Xiang-qian3, LÜ Li-guang3   

  1. 1. Beijing Key Laboratory of Industrial Contamination and Remediation, Environmental Protection Research Institute of Light Industry, Beijing 100089, China;
    2. Nanjing Institute of Environmental Sciences, Ministry of Environmental Protection, Nanjing 210042, China;
    3. Key Laboratory for Monitoring and Remediation of Heavy Metal Polluted Soils of Henan Province, Environmental Science Research Institute of Jiyuan City, Jiyuan 459001, China
  • Received:2017-06-02 Online:2018-01-25 Published:2018-01-26

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Abstract:

In-situ immobilization/stabilization of heavy metals in farmland soil is a soil remediation technology through amending the soil with certain chemical agents to reduce activity of the pollutants, inhibit their transport from soil to crops and hence mitigate their risks to crops. A total of 32 soil samples were collected from heavy metal polluted croplands in Henan Province for analysis of Cd, Pb, As, Cu, Zn, Ni and Cr for their totals and various fractions, i. e., weak-acid extractable, reducible, oxidizable and residue, using the BCR sequential extraction method, and then a precise soil remediation program formed. Results show that the concentration of Cd, Pb, As, Cu, Zn, Ni and Cr in the soil was on average 1.90, 144.91, 7.33, 32.24, 91.40, 28.80 and 19.76 mg·kg-1, respectively. Among them, Cd and Pb concentration in the soil was far beyond the criteria of the "Standard for Environmental Quality Evaluation Standards of Farmlands Producing Edible Agricultural Produce (HJ/T 332-2006)" reaching 3.17 and 1.81 times as high, respectively. The analysis using the BCR sequential extraction method shows that weak acid extractable Cd was relatively high in percentage of the total, reaching up to 24.06%; Pb existed in the soil mainly in reducible form, which accounted for 80.35% of the total in the soil, while the other 5 elements existed mainly in residual form. Regression analysis models were established based on contents of the weak acid extractables and their respective total of the heavy metal elements in the soil, indicating that the former varied with the latter exhibiting positive linear relationships between the two. According to the differences weak acid extractable Cd and Pb and their respective total in spatial distribution, the study area was partitioned. The partitioning by total Cd differed somewhat from that by weak acid extractable Cd, while the partitioning by weak acid extractable Cd was quite similar to that by weak acid extractable Pb, which may serve as a basis for formulation of a precise soil remediation program. In the end, levels and risks of the heavy metal pollution of the soil in view of the total and the content of available form of heavy metals, separately. Hakanson Potential Ecological Risk Assessment shows that Cd in the soil posed a strong potential ecological risk, but Cd in the soil was rated as moderate in risk according to the Risk Assessment Code (RAC). The difference between the two evaluations suggests that it is essential to take into account results of all various evaluation methods to program remediation of heavy metals polluted soils. This study may have laid down a foundation for evaluation and remediation of heavy metal polluted soils.

Key words: farmland soil, in-situ stabilization, fraction of heavy metal, partitioning of the study area, precise remediation, risk evaluation

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