Effect of Co-Use of Fly Ash and Granular Polyacrylamide on Infiltration, Runoff, and Sediment Yield from Sandy Soil under Simulated Rainfall

Kai Yang,Zejun Tang,Jianzhang Feng

doi:10.3390/agronomy10030344

Kai Yang, Zejun Tang + Show 1 more

Open Access

https://doi.org/10.3390/agronomy10030344

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Abstract

Coal fly ash (FA) and polyacrylamide (PAM) are two common amendments for improving hydraulic properties of sandy soil. However, their interaction effect on infiltration-runoff processes in sandy soil has been scarcely reported. In this study, FA and anionic PAM granules were mixed thoroughly with a 0–0.2 m sandy soil layer at FA rates of 0%, 10%, and 15% (w/w soil), and PAM rates of 0%, 0.01%, and 0.02% (w/w soil) along with each FA rate. A simulated rainfall laboratory experiment (slope gradient of 10°, rainfall intensity of 1.5 mm/min) was conducted. During the rainfall, the cumulative runoff yield increased while the average infiltration rate decreased with increasing FA and PAM rates. A higher FA rate of 15% and varying PAM rates resulted in a prominent increase in cumulative sediment yield. After the rainfall, the two-dimensional distribution of water content retained in the soil profile reflected that both FA and PAM increased the water retention capacity of sandy soil, and the effect became more obvious at higher FA and PAM rates. The possible mechanism for the effect of FA and PAM on inhibiting water infiltration during the rainfall and retaining water in the soil layer after the rainfall is attributed to the filling of pores of the coarse soil particles by fine-sized FA particles and flocculation function and binding action of PAM.

Highlights

Sandy soils represent one group of problem soils
The aims of this study were (i) to investigate the relationship between infiltration, runoff, and sediment yield in sandy soil treated with fly ash (FA) and PAM under simulated rainfall, and (ii) to characterize the redistribution of water retained in the soil layer after the rainfall
Under the simulated rainfall condition, the infiltration-runoff process in the sandy soil was found to be significantly influenced by FA and anionic PAM, exhibiting an increasing trend in cumulative runoff yield and decreasing trend in average infiltration rate with increasing FA and PAM rates

Summary

Introduction

Sandy soils represent one group of problem soils. They are coarse-textured and have high hydraulic conductivities and low water holding capacity. Sandy soils are prone to water drainage, which reduces the water and nutrient use efficiency of plants grown in the soil. Among common ameliorants for improving coarse-textured soils, coal fly ash (FA) which predominates in the solid residue generated from coal combustion, has been extensively reported to be effective in retaining water in the amended sandy soil [1,2,3,4,5,6,7,8]. The underlying mechanism of improved water holding capacity of sandy soil by FA is due to change of soil texture by fine-sized FA particles [4,5,6]. PAM can stabilize soil via binding particles together in a soil aggregate and reducing repulsive force among soil particles [11,13]

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