<p>Microbes have been suggested to have a strong impact on the transportation of chlorine in soils. There are speculations about environmental factors limiting microbial effect on chlorine movement and retention. For this study, a numerical hydrochemical model was built to describe microbial transformation of chlorine in a laboratory lysimeter experiment. Undisturbed soil cores used to set-up the experiment were collected from a coniferous forest soil in southeast Sweden. The lysimeters were modelled in groups depending on their different water and chloride treatments. Microbial transformation of chlorine was better described under high water residence times and high chloride loads compared to low water residence times and low chloride loads. Microbial activity was also shown to properly account for a sudden shift from net-chlorine retention to net chlorine release in most of the lysimeters. Oxygen proved to be very important in accounting for the short-term shift from chloride retention to release in all the lysimeters. Model outcome revealed that 0.02– 0.10 mg Cl- could be available per day in a coniferous soil depending on season and other soil conditions. This study shows that modeling enable a better understanding of chlorine biogeochemistry. It also confirms the speculated importance of microbial activities on chloride availability in soils.</p>

Microbes have been suggested to have a strong impact on the transportation of chlorine in soils. There are speculations about environmental factors limiting microbial effect on chlorine movement and retention. For this study, a numerical hydrochemical model was built to describe microbial transformation of chlorine in a laboratory lysimeter experiment. Undisturbed soil cores used to set-up the experiment were collected from a coniferous forest soil in southeast Sweden. The lysimeters were modelled in groups depending on their different water and chloride treatments. Microbial transformation of chlorine was better described under high water residence times and high chloride loads compared to low water residence times and low chloride loads. Microbial activity was also shown to properly account for a sudden shift from net-chlorine retention to net chlorine release in most of the lysimeters. Oxygen proved to be very important in accounting for the short-term shift from chloride retention to release in all the lysimeters. Model outcome revealed that 0.02– 0.10 mg Cl- could be available per day in a coniferous soil depending on season and other soil conditions. This study shows that modeling enable a better understanding of chlorine biogeochemistry. It also confirms the speculated importance of microbial activities on chloride availability in soils.

<p>The hypothetical assumption that chloride is conservative in the soil has been debated for the last decade. The results of the recent years of study in chlorine biogeochemistry show that chloride is non-conservative but rather participates in complex biogeochemical reactions in the soil. These interactions in nature inform the development of simplified hydrochemical model of chloride dynamics in the soil that is driven on soil routine component of HBV hydrological model. This novel attempt affords the opportunity to explore chlorine biogeochemistry further by evaluating the biological processes such as microbial biomass that predominate chlorine cycles in the same order of magnitude as earlier studied abiotic factors. Data from soil lysimeter experiment with different inputs treatments were used in the calibration and validation of both the hydrological and biogeochemical model. The results show that (1) model efficiency reduces with decreasing water residence and with increasing soil organic matter. (2) Longer water residence time (low water input), high chloride and high nitrogen input loads relatively enhance maximum biomass accumulation in a shorter time span. (3) Chloride retention time reduces with increasing chloride loads under short water residence. (4) Microbial biomass growth rate is highest under high chloride input treatments. (5) Biomass death rates shows reducing trend under short water residence (High water input). Further researches are therefore suggested for possible model expansion and to make the results of this model plausible under field conditions.</p>

The hypothetical assumption that chloride is conservative in the soil has been debated for the last decade. The results of the recent years of study in chlorine biogeochemistry show that chloride is non-conservative but rather participates in complex biogeochemical reactions in the soil. These interactions in nature inform the development of simplified hydrochemical model of chloride dynamics in the soil that is driven on soil routine component of HBV hydrological model. This novel attempt affords the opportunity to explore chlorine biogeochemistry further by evaluating the biological processes such as microbial biomass that predominate chlorine cycles in the same order of magnitude as earlier studied abiotic factors. Data from soil lysimeter experiment with different inputs treatments were used in the calibration and validation of both the hydrological and biogeochemical model. The results show that (1) model efficiency reduces with decreasing water residence and with increasing soil organic matter. (2) Longer water residence time (low water input), high chloride and high nitrogen input loads relatively enhance maximum biomass accumulation in a shorter time span. (3) Chloride retention time reduces with increasing chloride loads under short water residence. (4) Microbial biomass growth rate is highest under high chloride input treatments. (5) Biomass death rates shows reducing trend under short water residence (High water input). Further researches are therefore suggested for possible model expansion and to make the results of this model plausible under field conditions.