Roadside devegetation by microbially induced carbonate precipitation using osmosis, ammonium toxicity, and cementation effects

Abstract

Microbially induced carbonate precipitation (MICP) uses urease-producing bacteria to precipitate calcium carbonate (CaCO3), leading to soil improvement. MICP technology is directly related to the vegetation in the soil resulting from chemicals and cementation; however, only few studies have been conducted on this topic. This study aims to elucidate the application of MICP in the management of roadside vegetation using laboratory- and field-scale tests. At the laboratory scale, the effects of several chemical components of MICP, such as deionized water, growth media, bacteria, urea, and CaCl2, on seed germination and growth were explored using soil column testing in a growth chamber. A series of field tests were conducted on a highway embankment considering different initial ground conditions, such as original, cutting, and cultivated grounds. Leaf height and soil properties, such as electrical conductivity, ammonium concentration, pH, exchangeable calcium, and CaCO3 mass, were measured over time. The results showed the efficacy of devegetation by MICP and clarified that the devegetation mechanism occurs in three steps: as a short-term effect by osmosis, an intermediate-term effect by ammonium toxicity, and a long-term effect by cementation.