Use of NH₄ HCO₃‐DTPA soil test to assess availability and toxicity of selenium to alfalfa plants

Abstract

This study was carried out to determine if ammonium bicarbonate-DTPA soil test (AB-DTPA) of Soltanpour and Schwab for simultaneous extraction of P, K, Zn, Fe, Cu and Mn can be used to determine the availability index for Se. Five Mollisols from North Dakota were treated with sodium selenate and were subjected to several wetting and drying cycles. These soils were extracted with hot water and with ammonium bicarbonate-DTPA (AB-DTPA) solution for Se analysis.Alfalfa plants were grown in these soils in a growth chamber to determine plant uptake of Se. In addition to the above experiment, coal mine soil and overburden materials from Western Colorado were extracted and analyzed as mentioned above. It was found that hot water and AB-DTPA extracted approximately equal amounts of Se from Mollisols. A high degree of correlation (r =0.96) was found between Se uptake by plants and AB-DTPA extract-1147 1148 SOLTANPOUR AND WORKMAN able Se. Extractable level of Se in treated soils was decreased with time due to change of selenate to less soluble Se forms and plant uptake of Se. An AB-DTPA extractable Se level of over 100 ppb produced alfalfa plants containing 5 ppm or higher levels of Se that can be considered toxic to animals. Soils with about 2000 ppb of extractable Se were highly toxic to alfalfa plants and resulted in plant concentrations of over 1000 ppm of Se. The high rate of selenate (4ppm Se) was less toxic to alfalfa plants in soils of high organic matter content. This lower toxicity was accompanied with lower extractable levels of Se.The AB-DTPA solution extracted on the average about 31% more Se than hot water from the mine and overburden samples and was highly correlated with the latter (r =0.92).The results indicated the presence of bicarbonate-exchangeable Se in these materials.

Understanding Selenium Mobility by Sorption and Extraction Processes in Surface Coal Mine Spoils

“…3a). The exchange-phase (phosphate extractable) Se was also found to be linearly related to AB-DTP A extractable Se, which is also indicative of plant-available Se (Soltanpour and Workman, 1980). The linear increment of AB-DTP A extractable Se with increasing phosphate extractable Se indicated that adsorbed Se would be gradually transformed into plant-available Se (Fig.…”

Remedial investigation/feasibility study of the Clinch River/Poplar Creek Operable Unit. Volume 3. Risk assessment information. Appendixes E, F

“…Wan et al (1988) measured 30 to 85% reductions in shoot weight of alfalfa grown in soils containing 1.5 ppm Se. Shoot weights of alfalfa (Soltanpour and Workman 1980) and sorghum (Carlson et al 1991) were reduced approximately 25-90% and 55% by 2 and 1 ppm Se in various soils. The benchmark for Se in soil is 1 ppm.…”

Remedial investigation/feasibility study of the Clinch River/Poplar Creek operable unit. Volume 3: Appendixes E and F -- Risk assessment information

“…Wan et al (1988) measured 30 to 85% reductions in shoot weight of alfalfa grown in soils containing 1.5 ppm Se. Shoot weights of alfalfa (Soltanpour and Workman 1980) and sorghum (Carlson et al 1991) were reduced approximately 25-90% and 55% by 2 and 1 ppm Se in various soils. The benchmark for Se in soil is 1 ppm.…”