Influence of temperature on cadmium, lead and uranium content in the pore water of overwetting sod-podzolic loamy soil

Abstract

Effect of soil temperature on concentration and total reserve of cadmium, lead and uranium in the interstitial (pore) water of waterlogged sod-podzolic medium loamy soil after their keeping at the definite temperature in the range of 15-40 °C was established. It was found that in the water-saturated soil samples, portions of the cadmium, lead and uranium in the soil pore solution were correlated as follows: α Cd (0.2-0.3%) >> α Pb (0.08-0.10 %) ≥ α U (0.03-0.08%). An increase in temperature leads to a change in the physicochemical state of HM in the soil and, consequently, to a change in their content in soil pore moisture, where elements are concentrated in the most mobile and biologically accessible migration-active forms. The character and extent, to which temperature affects the concentration and total reserve of heavy metal (HM) in the soil water, depended on the chemical nature of HM and peculiarities of soil. The 5 °C temperature increase in the range of 15-40 °C caused the content of Pb in the soil pore water to increase an average of 4.5 %, and Cd and U to decrease by 4.4 and 13 %, respectively. The iron content in the soil water increased with increasing temperature, which indicated a decrease in the sorption capacity of iron hydroxides of soil, which probably significantly affected the fixation of Pb in the soil. In accordance with the values of the distribution coefficients of HM in the “solid phase-soil pore solution” system, the fixation of HM in the soil increased in the following way: Cd (180-230) << Pb (480-590) ≤ U (570-1620). The degree of Pb fixation in the soil increased with increase in the temperature of the soil, and Cd and U - with its decrease. Weakening of the HM fixation in the soil leads to an increase in their mobility and bioavailability and worsens the ecological state of terrestrial ecosystems.