Abstract:
Wind erosion is one of the significant natural calamities worldwide, which degrades around one-third of
global land. The eroded and suspended soil particles in the environment may cause health hazards, i.e.
allergies and respiratory diseases, due to the presence of harmful contaminants, bacteria, and pollens.
The present study evaluates the feasibility of microbially induced calcium carbonate precipitation (MICP)
technique to mitigate wind-induced erosion of calcareous desert sand (Thar desert of Rajasthan province
in India). The temperature during biotreatment was kept at 36 C to stimulate the average temperature of
the Thar desert. The spray method was used for bioaugmentation of Sporosarcina (S.) pasteurii and
further treatment using chemical solutions. The chemical solution of 0.25 pore volume was sprayed
continuously up to 5 d, 10 d, 15 d, and 20 d, using two different concentration ratios of urea and calcium
chloride dihydrate viz 2:1 and 1:1. The biotreated samples were subjected to erosion testing (in the wind
tunnel) at different wind speeds of 10 m/s, 20 m/s, and 30 m/s. The unconfined compressive strength of
the biocemented crust was measured using a pocket penetrometer. The variation in calcite precipitation
and microstructure (including the presence of crystalline minerals) of untreated as well as biotreated
sand samples were determined through calcimeter, scanning electron microscope (SEM), and energydispersive X-ray spectroscope (EDX). The results demonstrated that the erosion of untreated sand increases with an increase in wind speeds. When compared to untreated sand, a lower erosion was
observed in all biocemented sand samples, irrespective of treatment condition and wind speed. It was
observed that the sample treated with 1:1 cementation solution for up to 5 d, was found to effectively
resist erosion at a wind speed of 10 m/s. Moreover, a significant erosion resistance was ascertained in
15 d and 20 d treated samples at higher wind speeds. The calcite content percentage, thickness of crust,
bulk density, and surface strength of biocemented sand were enhanced with the increase in treatment
duration. The 1:1 concentration ratio of cementation solution was found effective in improving crust
thickness and surface strength as compared to 2:1 concentration ratio of cementation solution. The
calcite crystals formation was observed in SEM analysis and calcium peaks were observed in EDX analysis
for biotreated sand.
