An attempt to study the photoreduction rate of divalent mercury in landfill cover soils using experimental control systems

Abstract

Mercury (Hg) emissions from landfill cover soils are an important source of atmospheric Hg affecting local and regional atmospheric Hg budget. To date, soil Hg emissions have been extensively studied, whereas the photoreduction rate of cover soil Hg(II) under various conditions is rarely studied. Herein, two experimental control systems were built to investigate the effect of varying soil Hg(II) concentrations, moistures, and temperature on soil Hg emission in order to obtain the photoreduction rate of soil Hg(II) under varying environmental conditions. The results showed that high soil Hg(II) concentration and high soil temperature can facilitate Hg emission; however, high moisture inhibited Hg emission. In addition, solar radiation is an extremely critical factor for Hg emission and solar radiation-driven photoreduction is an important contribution process for Hg emission; moreover, soil Hg emission is controlled by multiple environmental factors and varies with environmental factors. Through the data fitting and formula calculation, the photoreduction rates under varying conditions are in the range of 1.49–8.54 × 10⁻¹⁰ m² s⁻¹ W⁻¹, which can be helpful for the construction of a process-based model of soil Hg emission and Hg management in landfills.