Atrazine sorption by biochar, tire chips, and steel slag as media for blind inlets: A kinetic and isotherm sorption approach

Authors: Gonzalez, Javier; Shipitalo, Martin; Smith, Douglas; Pappas, Elizabeth; Livingston, Stanley

Submitted to: Journal of Water Resource and Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/26/2016
Publication Date: 11/29/2016
Publication URL: https://handle.nal.usda.gov/10113/6961203
Citation: Gonzalez, J.M., Shipitalo, M.J., Smith, D.R., Pappas, E.A., Livingston, S.J. 2016. Atrazine sorption by biochar, tire chips, and steel slag as media for blind inlets: A kinetic and isotherm sorption approach. Journal of Water Resource and Protection. 8:1266-1282.

Interpretive Summary: Surface inlets or tile risers are installed in subsurface drainage systems to reduce ponding duration and surface runoff, but can contribute to water quality concerns by allowing water to directly enter buried drains. Blind inlets, consist of perforated pipes covered with gravel and an overlying sand layer, have been shown to be effective in reducing losses of sediment, nutrients, and pesticides than typical tile risers. In this study, we investigated whether the effectiveness of blind inlets to remove herbicide atrazine, could be further improved by amended them with materials other than limestone. The media, shredded tires (tire chips), electric arc steel furnace slag (steel slag), and biochar (a charcoal-like material) were chosen because they are readily available, inexpensive, and do not present environmental concerns. Our data indicated that atrazine removal rate was 38 times faster for biochar than tire chips. The removal potential of atrazine by biochar was the highest, followed by tire chips, steel slag, and limestone. Test results also show no leaching of heavy metals at levels of environmental concern. The effectiveness of blind inlets, as well as other conservation practices that use filter media such as rain gardens and filter socks, could be improved by incorporating more reactive.

Technical Abstract: Surface inlets are installed in subsurface drainage systems to reduce ponding duration and surface runoff, but can contribute to water quality concerns by allowing water to directly enter buried drains. Blind inlets, consist of perforated pipes covered with gravel and are separated from an overlying sand layer by a geotextile membrane and have been shown to be more effective in reducing losses of sediment, nutrients, and pesticides than typical tile line risers. In this study, we investigated whether the effectiveness of blind inlets to sorb pollutants, with emphasis on the herbicide atrazine, could be further improved by amended them with materials other than limestone. The media, shredded tires (tire chips), electric arc steel furnace slag (steel slag), and biochar were chosen because they are readily available, inexpensive, and do not present environmental concerns. Kinetic sorption and isotherms were determined to ascertain atrazine sorption by these materials, in addition to testing for potential metal leaching using the Synthetic Precipitation Leaching Procedure (SPLP) and the Toxicity Characteristic Leaching Procedure (TCLP). The kinetic data was fitted using pseudo first- and second-order reaction equations and indicated that atrazine sorption rate was 38 times faster and equilibrium was reached 5 times earlier for biochar than tire chips. The 24-h sorption isotherm data was fitted to the Freundlich sorption equation. The sorption coefficient for biochar was higher than for tire chips, steel slag, and limestone. Per the SPLC and TLCP tests, there was no leaching of heavy metals at levels of environmental concern. Our results suggested that the effectiveness of blind inlets as well as other conservation practices such as rain gardens and filter socks that include filter media could be improved by incorporating more reactive materials than sand and gravel with biochar being a particularly effective alternative.