Xu Shangping, Jaffé Peter R
Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ 08544, USA.
J Environ Qual. 2006 Jan 5;35(1):334-41. doi: 10.2134/jeq2005.0181. Print 2006 Jan-Feb.
The effect of two wetland plants, Typha latifolia L. (cattail) and Phragmites australis (Cav.) Trin. ex Steud (common reed), on the fate of Cr(VI) in wetland sediments was investigated using greenhouse bench-scale microcosm experiments. The removal of Cr(VI) was monitored based on the vertical profiles of aqueous Cr(VI) in the sediments. The Cr(VI) removal rates were estimated taking into account plant transpiration, which was found to significantly concentrate dissolved species in the sediments. After correcting for evapotranspiration, the actual Cr(VI) removal rates were significantly higher than would be inferred from uncorrected profiles. On average, the Cr(VI) removal rates were 0.005 to 0.017 mg L(-1) d(-1), 0.0003 to 0.08 mg L(-1) d(-1), and 0.004 to 0.13 mg L(-1) d(-1) for the control, T. latifolia, and P. australis microcosms, respectively. The fate of the removed Cr(VI) was examined by determining the quantity and chemical speciation of the Cr in the sediment and plant materials. Chromium(III) was the dominant form of Cr in both the sediment and plants, and precipitation of Cr(III) in the sediment was the major pathway responsible for the disappearance of aqueous Cr(VI) from the pore water. Incubation results showed that abiotic reduction was the primary mechanism underlying Cr(VI) removal in the microcosm sediments. Organic compounds produced by plants, including root exudates and mineralization products of dead roots, are thought to be the factor that is either directly or indirectly responsible for the gap between Cr(VI) removal efficiencies in the sediments of the vegetated and unvegetated microcosms.
利用温室盆栽微宇宙实验，研究了两种湿地植物宽叶香蒲（香蒲）和芦苇对湿地沉积物中六价铬归宿的影响。基于沉积物中六价铬的垂直分布监测六价铬的去除情况。在考虑植物蒸腾作用的情况下估算六价铬的去除率，发现蒸腾作用会显著使沉积物中的溶解态物质富集。校正蒸散作用后，实际六价铬去除率显著高于未校正分布所推断的值。平均而言，对照、宽叶香蒲和芦苇微宇宙的六价铬去除率分别为0.005至0.017mg L⁻¹ d⁻¹、0.0003至0.08mg L⁻¹ d⁻¹和0.004至0.13mg L⁻¹ d⁻¹。通过测定沉积物和植物材料中铬的含量和化学形态来研究去除的六价铬的归宿。沉积物和植物中铬的主要形态均为三价铬，沉积物中三价铬的沉淀是孔隙水中六价铬消失的主要途径。培养结果表明，非生物还原是微宇宙沉积物中六价铬去除的主要机制。植物产生的有机化合物，包括根系分泌物和死根的矿化产物，被认为是造成有植被和无植被微宇宙沉积物中六价铬去除效率差异的直接或间接因素。
