Bioavailability of barium to Trifolium pratense L. in soils contaminated with drill cuttings

Barium sulphate is the basic component of drilling fluids. Due to the widespread use of drilling processes there is a fear that barium will appear in the environment and that it may become available to plants in different conditions. In this study the bioavailability of barium in soil with the addition of drill cuttings was examined using red clover (Trifolium pratense L.) in a pot experiment. The barium concentration in the examined soils, determined by an inductively coupled plasma mass spectrometry method, was in the range 56-15 800 mg kg-1, depending on the dose of the drill cuttings (2.5-15% of dry weight) added to the mineral soil (control sample). The addition of drilling waste to the soil (pH 4.1, total exchangeable bases 2.1) significantly changed the physicochemical properties of the soil, increasing the pH (up to 7.1) and the concentration of alkaline cations (total exchangeable bases up to 51.2 cmol kg-1). The biomass production in the soil containing drill cuttings was higher compared to the control sample, but the maximum biomass level was found in soil with a 5% dose of the waste. Plant shoot biomass production and the concentration of barium in shoots and roots were closely related to the concentration of barium in the soil. Higher concentrations of barium were found in the roots. Red clover showed a marginal accumulation of barium (transfer factor 0.02-0.08).