Assessment of Existing Roadside Swales with Engineered Filter Soil: II. Treatment Efficiency and in situ Mobilization in Soil Columns
- Simon T. Ingvertsen *a,
- Karin Cederkvistb,
- Marina B. Jensenc and
- Jakob Magida
- a Dep. of Agriculture and Ecology, Faculty of Life Sciences, Univ. of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark
b Dep. of Basic Sciences, Faculty of Life Sciences, Univ. of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark
c Center for Forest and Landscape, Faculty of Life Sciences, Univ. of Copenhagen, Rolighedsvej 23, 1958 Frederiksberg C, Denmark. Assigned to Associate Editor C.A. Grant
Use of roadside infiltration systems using engineered filter soil for optimized treatment has been common practice in Germany for decades, but little documentation is available regarding their long-term treatment performance. Here we present the results of laboratory leaching experiments with intact soil columns (15 cm i.d., 25–30 cm length) collected from two German roadside infiltration swales constructed in 1997. The columns were irrigated with synthetic solutions of unpolluted or polluted (dissolved heavy metals and fine suspended solids) road runoff, as well as a soluble nonreactive tracer (bromide) and a dye (brilliant blue). The experiments were performed at two irrigation rates corresponding to catchment rainfall intensities of approximately 5.1 and 34 mm/h. The bromide curves indicated that preferential flow was more pronounced at high irrigation rates, which was supported by the flow patterns revealed in the dye tracing experiment. Nonetheless, the soils seemed to be capable of retaining most of the dissolved heavy metals from the polluted road runoff at both low and high irrigation rates, except for Cr, which appears to pass through the soil as chromate. Fluorescent microspheres (diameter = 5 μm) used as surrogates for fine suspended solids were efficiently retained by the soils (>99%). However, despite promising treatment abilities, internal mobilization of heavy metals and P from the soil was observed, resulting in potentially critical effluent concentrations of Cu, Zn, and Pb. This is mainly ascribed to high concentrations of in situ mobilized dissolved organic carbon (DOC). Suggestions are provided for possible improvements and further research to minimize DOC mobilization in engineered filter soils.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © 2012. . Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.