EFFECT OF HEAT PRETREATMENTS ON ARSENIC MEASUREMENTS IN SOIL

Abstract

Coarse and finely ground samples from Chernozemic and Luvisolic soils were heated for 2 h at temperatures ranging from 150 to 1150 °C prior to analysis for total As. Thermal pretreatment at temperatures of 150 to 750 °C increased the measured levels of As in all A and B and in some C horizon samples. Heating at 550 °C caused as much as a twofold increase in levels detected in some A horizons. Initial net loss of As through volatilization occurred for all samples starting at pretreatment temperatures of 750 °C and ending at 850 to 1000 °C. Following this initial loss, measured levels of As generally increased with further heating. Heating soils at 1100 °C and higher then caused nearly complete volatilization of As from all Ah horizon samples. Samples of B and C horizons heated at 1150 °C contained from 30% more to 80% less than the content in air-dried samples. Grinding had no significant effect on As measurements. The thermal dependence of As measurements is discussed in terms of forms of the element, mineral transformations, and efficacy of the HCl digestion procedure. Key words: Arsenic analysis, soil arsenic, form of arsenic, trace elements, arsenic geochemistry, methods of analysis