Calculating carbon mass balance from unsaturated soil columns treated with CaSO₄-minerals: Test of soil carbon sequestration

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>Renewed interest in managing C balance in soils is motivated by increasing atmospheric concentrations of CO<SUB>2</SUB> and consequent climate change. Here, experiments were conducted in soil columns to determine C mass balances with and without addition of CaSO<SUB>4</SUB>-minerals (anhydrite and gypsum), which were hypothesized to promote soil organic carbon (SOC) retention and soil inorganic carbon (SIC) precipitation as calcite under slightly alkaline conditions. Changes in C contents in three phases (gas, liquid and solid) were measured in unsaturated soil columns tested for one year and comprehensive C mass balances were determined. The tested soil columns had no C inputs, and only C utilization by microbial activity and C transformations were assumed in the C chemistry. The measurements showed that changes in C inventories occurred through two processes, SOC loss and SIC gain. However, the measured SOC losses in the treated columns were lower than their corresponding control columns, indicating that the amendments promoted SOC retention. The SOC losses resulted mostly from microbial respiration and loss of CO<SUB>2</SUB> to the atmosphere rather than from chemical leaching. Microbial oxidation of SOC appears to have been suppressed by increased Ca<SUP>2+</SUP> and SO<SUB>4</SUB> <SUP>2</SUP> <SUP>−</SUP> from dissolution of CaSO<SUB>4</SUB> minerals. For the conditions tested, SIC accumulation per m<SUP>2</SUP> soil area under CaSO<SUB>4</SUB>-treatment ranged from 130 to 260gCm<SUP>−1</SUP> infiltrated water (20–120gCm<SUP>−1</SUP> infiltrated water as net C benefit). These results demonstrate the potential for increasing C sequestration in slightly alkaline soils via CaSO<SUB>4</SUB>-treatment.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Soil carbon mass balance was calculated in an unsaturated soil column. </LI> <LI> Soil amendment with CaSO<SUB>4</SUB>-minerals works for carbon sequestration. </LI> <LI> Main carbon sequestration resulted from organic carbon retention. </LI> <LI> Precipitated calcite can be considered as a carbon sink in this study. </LI> <LI> CaSO<SUB>4</SUB>-soil amendment is proved as a effective carbon sequestration method. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>