Reductions of Fe(III) and pentachlorophenol linked with geochemical properties of soils from Pearl River Delta

• Published in: Geoderma 2014-04, Vol.217-218, p.201-211
• Main Authors: Chen, Manjia, Tao, Liang, Li, Fangbai, Lan, Qing
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Bacteria; Biological and medical sciences; Brackish; Correlation; Earth sciences; Earth, ocean, space; Exact sciences and technology; Freshwater; Fundamental and applied biological sciences. Psychology; Geochemistry; Iron; Iron species; Microbial community; Reduction; Reductive dechlorination; Soil chemical properties; Soils; Subtropical soils; Surficial geology; Transformations; Vegetables
• ISSN: 0016-7061; 1872-6259
• DOI: 10.1016/j.geoderma.2013.12.003

Soils in the Pearl River Delta (PRD) of South China contain iron with a higher abundance and reactivity formed under a subtropical monsoon climate with a unique biogeochemistry. Iron cycle plays a vital role in transformation of contaminants. However, the linkage between iron cycle and contaminants transformation vs. geochemical properties of soils remains unclear. In this study, a set of experiments for reductions of Fe(III) and pentachlorophenol (PCP) were conducted to fill up the gap between Fe(III) reducibility and PCP transformation on the view of geochemistry. Fourteen soil samples were collected from the A (0 to 20cm) horizon in the PRD and were divided into three groups based on their land use types (LUTs, i.e., vegetable fields, paddy soils and mangroves). The experiments were designed and subsequently conducted at pH 7.0±0.2 (excluding pH interference) in three different conditions (i.e., soil-sterile, soil, and soil+lactate). Kinetic measurements showed that the reduction rates (μmax) of Fe(III) and PCP could be calculated using a logistic model. The stepwise regression analyses showed that oxalate-extractable iron (Feo) was likely one of the most active iron sources for soil Fe(III) reduction. Feo and dithionite-extractable iron (Fed) had close correlations with the rate of PCP reductive transformation. Moreover, parallel correlations exist between μmax-PCP and μmax-Fe(II)sorbed, illustrating the crucial effect of sorbed Fe(II) on PCP reduction in soils. The variance analysis results showed significant differences in the average μmax-PCP and μmax-Fe(II)sorbed value under different LUTs (vegetable field