Effects of polyacrylamide and gypsum on soil erosion and sediment transport

Abstract

This study evaluates the effectiveness of two popular soil amendments of gypsum and polyacrylamide (PAM), in minimizing soil erosion from one soil and one overburden (spoil) material of a mine rehabilitation site in North Queensland. The treatments included; untreated soil (control), gypsum application rate of 10 t/ha, anionic PAM application rate of 40 kg/ha, and combined application of both amendments (PAM+gypsum) at the same rates above, all replicated three times. Rainfall experiments were carried out in the Griffith University's rainfall-runoff simulation facility on 9% slope at the mean rainfall intensity of 120 mm/h and the duration of 30 minutes. Runoff and sediment samples were collected at specific time intervals during the experiments. Total soil loss from the treated soil and spoil were significantly lower than for control. Total soil loss for soil were reduced by 39%, 58%, and 80%, respectively for gypsum, PAM, and PAM+gypsum treatments, compared to the control. Total sediment loss for spoil was reduced by 48%, 60%, and 72%, respectively for gypsum, PAM, and PAM+gypsum treatments, compared to the control. Results indicate that the use of gypsum, PAM, and the combination of both significantly reduce erosion from the tested soil and spoil but the combination of the two gives the best results for both. The improved surface conditions on the treated soil and spoil contributed towards the reduction of soil loss. The soil amendments were effective in maintaining a well-aggregated soil surface that minimize detachment by rain and runoff and was resistant to surface sealing. The application of soil amendments on the slopes prior to the establishment of vegetation may be an effective way of reducing erosion and minimizing the offsite consequences of sediment and pollutant transport prior to the establishment of a viable vegetation cover. These amendments appear to increase soil moisture thus helping the establishment of the vegetation cover as well.