ARS | Publication request: Soil Ph and Anion Abundance Affects on Copper Adsorption

Submitted to: Journal Of Environmental Science And Health
Publication Acceptance Date: June 20, 2004
Publication Date: August 1, 2004
Citation: Alva, A.K., Baugh, T.J., Sajwan, K.S., Paramasivam, S. 2004. Soil Ph And Anion Abundance Affects On Copper Adsorption. Journal Of Environmental Science And Health.

Interpretive Summary: Copper is a heavy metal naturally occurring in soils in trace amounts. Copper is a micronutrient, hence required for plant growth and production in minute quantities. Most pesticides used in agricultural production contain copper. As a heavy metal, any input of copper tends to accumulate in the soil, mostly in the surface horizon, because of its least transport down the soil profile. At higher pH, copper exists in forms unavailable to the plants. Therefore, copper phytotoxicity is not an issue in high pH soils, regardless of high amounts of total copper. This study was conducted to evaluate the effects of either calcium chloride or calcium nitrate (0.01 M) background solution on adsorption of copper, at various concentrations (0 to 2000 mg/L), by three soils in the pH range 6.2 to 9.9. At copper concentrations in the range of 0 to 100 mg/L, 95 to 99 percent of applied copper was adsorbed by all three soils. As the copper concentration was increased in the range of 500 to 2000 mg/L, copper adsorption decreased from 60 to 24 percent in two soils in the pH range of 6.2 to 7.9, and from 77 to 34 percent in a high pH soil (pH = 9.9). Application of incinerated sewage sludge to a Palouse silt loam soil increased the copper adsorption which was, in part, due to an increase in the suspension pH.

Technical Abstract: Copper (Cu) input to agricultural soils results from Cu containing pesticides and/or that in soil amendments, such as manure or sewage sludge. Soil and soil solution properties influence the adsorption and desorption of Cu by the soil, which in turn determines its plant availability and/or phytotoxicities. Effects of different anion enrichment in the equilibrium solution on Cu adsorption by different soils (pH range of 6.2 to 9.9) were investigated in this study over a range of Cu concentrations. With Cu concentrations in the range of 0 to 100 mg L-1 in the equilibration solution, 95 to 99% of applied Cu was adsorbed by all three soils. The adsorption of Cu was similar regardless of using either 0.01M CaCl2 or Ca(NO3)2 as the equilibration solution. When the Cu concentration in the equilibration solution was further increased in the range of 500 to 2000 mg L-1, the adsorption of Cu decreased from 60 to 24% of applied Cu in two soils with pH 6.2 to 7.9. In a high pH soil (pH = 9.9), the Cu adsorption decreased from 77 to 34%. Addition of incinerated sewage sludge (ISS) to a Palouse silt loam soil (pH=6.2) increased the Cu adsorption as compared to that by unamended soil. This was, in part, due to an increase in the soil suspension pH with ISS amendment.