Soil Solution Changes Affected by Biosolids and Aluminum-Based Drinking Water Treatment Residuals (Al-WTRs) During Short-Term Incubation Experiment

Abstract

An incubation experiment was conducted at Southern Illinois University Edwardsville (SIUE) to investigate the effects of biosolids and WTRs application on soil solution chemistry of Troy soils during incubation time. The results indicated that equilibrium time for each element was different. In general, soil solution pH was significantly increased (p<0.05) with increasing WTRs application rates at all incubation times. Similarly, electrical conductivity of soil solution was significantly increased (p<0.05) with increasing WTRs application rates at all incubation times. Also, EC of soil solution was significantly increased with increasing WTRs application rates in 50 g.kg^-1biosolids-amended soils. Large changes in concentrations of different anions with WTRs and /or biosolids application during the incubation time. Calcium concentrations were significantly increased with increasing application rate of WTRs at all incubation times. The results also indicated that 24 hours may be enough for Cr to equilibrate with the solid phase. The value of Mg concentration at 20 days of incubation was the greatest in biosolids-untreated soils, and then Mg concentrations decreased with increasing incubation time. In biosolids-treated soil, the K concentrations were dramatically increased with increasing incubation time to 20 days at all WTRs application rates. . Na concentrations in biosolids treated and un-treated soils were much higher after 20 days incubation time with a subsequent decrease at 40 and 60 days of incubation. The P concentrations were significantly reduced with increasing WTRs application rates at all incubation times. While, the concentration was significantly increased with increasing the incubation time in both biosolids treated and untreated soils. Cu concentrations in biosolids untreated soils were small and there was a significant difference between incubation times or application rates of WTRs. Also, Ni concentrations in leachate were not detectable in biosolids untreated soils. While, in biosolids-treated soils ,Ni concentrations were significantly increased after 20 days incubation and reached to the maximum value at all treatments of WTRs after 20 days incubation time. In biosolids-treated soils, Mn concentrations in soil solution were much higher than those of un-treated soils. Also, maximum concentrations of Mn were observed after 60 days of incubation time. Mn concentrations were significantly decreased with increasing application rate of WTRs in biosolids and treated and un-treated soils. Zn concentrations were significantly decreased with increasing application rate of WTRs in biosolids treated and un-treated soils. In biosolids untreated soils, Mo, Fe and V were very small concentrations in soil solution during all incubation time. The maximum concentration of Sr was observed after 20 days of incubation, but maximum Ba concentration was recorded after one day of incubation. However, in biosolids-treated soil, Sr concentration reached to the maximum after 20 days and Ba concentration reached to the maximum value after 60 days of incubation. Al concentrations in biosolids untreated soils were very small and there was a significant difference between incubation times or application rates of WTRs. While, in biosolids-treated soils , Al concentrations were significantly increased after 40 days incubation and reached to the maximum value at all treatments of WTRs after 40 days incubation time.

Keywords: Biosolids - composition -Soil solution-WTRs