Electrostatic method to remove particulate organic matter from soil

Authors: Wuest, Stewart; Reardon, Catherine - Kate

Submitted to: The Journal of Visualized Experiments (JoVE)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2020
Publication Date: 2/10/2021
Citation: Wuest, S.B., Reardon, C.L. 2021. Electrostatic method to remove particulate organic matter from soil. The Journal of Visualized Experiments (JoVE). 168. Article e61915. https://doi.org/10.3791/61915.
DOI: https://doi.org/10.3791/61915

Interpretive Summary: Estimations of soil organic carbon are dependent on soil processing methods including removal of undecomposed plant material. Inadequate separation of roots and plant material from soil can result in highly variable carbon measurements. In this video we show how electrostatic attraction can be used to remove plant material from a soil sample. An electrostatically charged surface passed close to dry soil naturally attracts both undecomposed and partially decomposed plant particles. The soil sample is spread in a thin layer on a flat surface or a soil sieve. A petri dish is electrostatically charged by rubbing with a cloth. The charged dish is passed repeatedly over the soil. The dish is then brushed clean and recharged. The process removes about 1 to 5% of the soil sample, and about 2 to 3 times that proportion in organic carbon. Like other particulate removal methods, the endpoint is arbitrary and not all free particulates are removed. The process takes approximately 5 minutes and does not require a chemical process as do density flotation methods. Electrostatic attraction consistently removes material with higher than average C concentration and C:N ratio, and much of the material can be visually identified as plant or faunal material under a microscope.

Technical Abstract: Estimations of soil organic carbon are dependent on soil processing methods including removal of undecomposed plant material. Inadequate separation of roots and plant material from soil can result in highly variable carbon measurements. Methods to remove the plant material are often limited to the largest, most visible plant materials. In this video we show how electrostatic attraction can be used to remove plant material from a soil sample. An electrostatically charged surface passed close to dry soil naturally attracts both undecomposed and partially decomposed plant particles, along with a small quantity of mineral and aggregated soil. The soil sample is spread in a thin layer on a flat surface or a soil sieve. A plastic or glass petri dish is electrostatically charged by rubbing with a nylon or cotton cloth. The charged dish is passed repeatedly over the soil. The dish is then brushed clean and recharged. Re-spreading the soil and repeating the procedure eventually results in a diminishing yield of particulates. The process removes about 1 to 5% of the soil sample, and about 2 to 3 times that proportion in organic carbon. Like other particulate removal methods, the endpoint is arbitrary and not all free particulates are removed. The process takes approximately 5 minutes and does not require a chemical process as do density flotation methods. Electrostatic attraction consistently removes material with higher than average C concentration and C:N ratio, and much of the material can be visually identified as plant or faunal material under a microscope.