Adsorption–Desorption Characteristics of Mercury in Paddy Soils of China
- Y. D. Jingab,
- Z. L. He *ac and
- X. E. Yanga
- a MOE Key Lab. of Environ., Remediation and Ecosystem Health, College of Natural Resource and Environment Sciences, Zhejiang Univ., Hangzhou 310029, China
b Dep. of Resources and Planning, Qufu Normal Univ., Jining 273165, China
c Univ. of Florida, Inst. of Food and Agricultural Sciences, Indian River Research and Education Center, Fort Pierce, FL 34945, USA
Mercury (Hg) has received considerable attention because of its association with various human health problems. Adsorption–desorption behavior of Hg at contaminated levels in two paddy soils was investigated. The two representative soils for rice production in China, locally referred to as a yellowish red soil (YRS) and silty loam soil (SLS) and classified as Gleyi-Stagnic Anthrosols in FAO/UNESCO nomenclature, were respectively collected from Jiaxin County and Xiasha District of Hangzhou City, Zhejiang Province. The YRS adsorbed more Hg2+ than the SLS. The characteristics of Hg adsorption could be described by the simple Langmuir adsorption equation (r 2 = 0.999 and 0.999, P < 0.01, respectively, for the SLS and YRS). The maximum adsorption values (Xm) that were obtained from the simple Langmuir model were 111 and 213 mg Hg2+ kg−1 soil, respectively, for the SLS and YRS. Adsorption of Hg2+ decreased soil pH by 0.75 unit for the SLS soil and 0.91 unit for the YRS soil at the highest loading. The distribution coefficient (kd) of Hg in the soil decreased exponentially with increasing Hg2+ loading. After five successive desorptions with 0.01 mol L−1 KCl solution (pH 5.4), 0 to 24.4% of the total adsorbed Hg2+ in the SLS soil was desorbed and the corresponding value of the YRS soil was 0 to 14.4%, indicating that the SLS soil had a lower affinity for Hg2+ than the YRS soil at the same Hg2+ loading. Different mechanisms are likely involved in Hg2+ adsorption–desorption at different levels of Hg2+ loading and between the two soils.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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