Effect analysis of biomineralization for solidifying desert sands

The sand-dust weather has become an environmental hazard in the world.However,it is still a challenge to control sandstorms and decrease sand-dust weather.The biomineralization technology for solidifying desert sands has been developed as a novel method in recent years.In this study,the wind erosion tests and verification tests of the sand solidification system were conducted via a series of laboratory experiments.The effects of sand barriers,injecting volume and concentration of the biochemical solution in the sandstorm protection were studied.Moreover,a field test of 60,000 square metres was conducted in the solidification area on both sides of the Wuma Highway in the Tengri Desert.The biomineralization technique was used to solidify sand to prevent the wind from blowing quicksand onto the newly built highway and causing accidents.Results demonstrated that the biomineralization sand solidification method had a good solidification==effect,improved the survival rate,and promoted the growth of plants in the desert.This innovative biomineralization technology is an environmentally responsible technology to control sandstorm disasters.

Bio-cementation for tidal erosion resistance improvement of foreshore slopes based on microbially induced magnesium and calcium precipitation

In most coastal and estuarine areas,tides easily cause surface erosion and even slope failure,resulting in severe land losses,deterioration of coastal infrastructure,and increased floods.The bio-cementation technique has been previously demonstrated to effectively improve the erosion resistance of slopes.Seawater contains magnesium ions(Mg^(2+))with a higher concentration than calcium ions(Ca^(2+));therefore,Mg^(2+)and Ca^(2+)were used together for bio-cementation in this study at various Mg^(2+)/Ca^(2+)ratios as the microbially induced magnesium and calcium precipitation(MIMCP)treatment.Slope angles,surface strengths,precipitation contents,major phases,and microscopic characteristics of precipitation were used to evaluate the treatment effects.Results showed that the MIMCP treatment markedly enhanced the erosion resistance of slopes.Decreased Mg^(2+)/Ca^(2+)ratios resulted in a smaller change in angles and fewer soil losses,especially the Mg^(2+)concentration below 0.2 M.The decreased Mg^(2+)/Ca^(2+)ratio achieved increased precipitation contents,which contributed to better erosion resistance and higher surface strengths.Additionally,the production of aragonite would benefit from elevated Mg^(2+)concentrations and a higher Ca^(2+)concentration led to more nesquehonite in magnesium precipitation crystals.The slopes with an initial angle of 53°had worse erosion resistance than the slopes with an initial angle of 35°,but the Mg^(2+)/Ca^(2+)ratios of 0.2:0.8,0.1:0.9,and 0:1.0 were effective for both slope stabilization and erosion mitigation to a great extent.The results are of great significance for the application of MIMCP to improve erosion resistance of foreshore slopes and the MIMCP technique has promising application potential in marine engineering.

Erosion resistance of treated dust soils based on the combined enzymatically induced carbonate precipitation and polyacrylic acid

The majority of cities worldwide are grappling with the challenge of dust pollution.Recently,the application potential of enzymatically induced carbonate precipitation(EICP),a novel environmentally friendly method,for dust control has been convincingly demonstrated.However,the long-term durability of EICP treatment is consistently a significant concern,particularly in regions prone to recurrent erosion caused by rainfall.As a result,the erosion durability of the EICP-treated dust soils requires further investigation.To address this,Polyacrylic acid(PAA)was added to the cementation solution in this study as the combined PAA and EICP treatment for dust control.The results showed that the addition of PAA slightly affected urea degradation;however,the combined PAA and EICP treatment significantly improved surface strength from 300 kPa to 500 kPa,especially for the wind-erosion resistance compared with the EICP treatment alone.The surface strength of samples treated with the combined PAA and EICP still exhibited a decrease due to repeated rainfall erosion,along with a reduction in calcium carbonate(CaCO_(3))contents.Nevertheless,the decreasing slopes of surface strength(k=13.434,14.002,or 14.186)in response to repeated rainfall for EICP-PAA-treated slopes were much smaller than those for EICP-treated samples(k=14.271),as well as the decreasing slopes of CaCO_(3)contents,which suggested the slopes with the combined treatment had significantly improved durability.By comparing the cementation effect and the influence of repeated rainfalls on treated dust samples,the EICP-PAA(50 g/L)treatment achieved better dust control effects.Overall,the combined treatment of EICP-PAA shows promising potential for effectively suppressing dust generation and enhancing erosion durability.