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[MIS14-05] Enhanced rock weathering in abandoned mines and forests, Shikabe, Hokkaido: a preliminary investigation
Keywords:enhanced rock weathering, abandoned mines, forest, basalt
Increasing concentrations of greenhouse gases (e.g., carbon dioxide) in the atmosphere and the resulting global warming is a pressing problem, threatening global food security and driving extreme climate events. Urgent examinations are underway for several techniques to reduce emission of the greenhouse gases and/or capture and storage the gases. Among them, we focused on the technique of enhanced rock weathering, that is, accelerating the natural geological process, which removes carbon dioxide from the atmosphere. This is achieved by applying crushed stone powder on agricultural fields or forested lands.
We conducted a pilot study at two sites in the Amemasu river basin, Shikabe, Hokkaido, Japan. One site was located on a dumping area of tailings from an abandoned underground mine for iron and sulfur, covered by neighboring surface soils. The other site was located in a deciduous broadleaf forest. The distance between these sites was 200–300 m. Along slopes in each site, we established 2 m × 5 m artificial small catchments (referred to as main plots), surrounded with corrugated plates and connected to tanks at the bottom of the catchments to collect surface and soil water. Soil temperature and moisture, wind speed, and rainfall intensity were also monitored. Additionally, 1.5 m × 1.5 m quadrats (referred to as subplots) were established to collect surface soils repeatedly. For both plots, we applied crushed basalt obtained from neighboring mining and quarrying companies in Hokkaido, to minimize transportation energy requirements. The grain size of crushed basalt was homogenized to be 150–250 mm powder or formed into 8 mm pellets. Application amounts of the powder/pellets were set at three levels: 0 (control), 4, and 8 kg m−2. We aimed to examine mineralization of carbon dioxide by analyzing the migration of bicarbonate, calcium, and magnesium ions, as well as the precipitation of secondary carbonate minerals. Potential co-benefits, such as cost-effective neutralization of acid mine drainage without additional carbon dioxide emissions and promoting tree growth, were also investigated.
This study commenced in April 2023. The basalt powder/pellets were applied in July, followed by continuous monitoring for three months until the winter snowfall. In this presentation, we will report preliminary results at this stage, including increased pH in the surface water in some main plots and the existence of powder/pellets trapped in the surface litter layers.
We conducted a pilot study at two sites in the Amemasu river basin, Shikabe, Hokkaido, Japan. One site was located on a dumping area of tailings from an abandoned underground mine for iron and sulfur, covered by neighboring surface soils. The other site was located in a deciduous broadleaf forest. The distance between these sites was 200–300 m. Along slopes in each site, we established 2 m × 5 m artificial small catchments (referred to as main plots), surrounded with corrugated plates and connected to tanks at the bottom of the catchments to collect surface and soil water. Soil temperature and moisture, wind speed, and rainfall intensity were also monitored. Additionally, 1.5 m × 1.5 m quadrats (referred to as subplots) were established to collect surface soils repeatedly. For both plots, we applied crushed basalt obtained from neighboring mining and quarrying companies in Hokkaido, to minimize transportation energy requirements. The grain size of crushed basalt was homogenized to be 150–250 mm powder or formed into 8 mm pellets. Application amounts of the powder/pellets were set at three levels: 0 (control), 4, and 8 kg m−2. We aimed to examine mineralization of carbon dioxide by analyzing the migration of bicarbonate, calcium, and magnesium ions, as well as the precipitation of secondary carbonate minerals. Potential co-benefits, such as cost-effective neutralization of acid mine drainage without additional carbon dioxide emissions and promoting tree growth, were also investigated.
This study commenced in April 2023. The basalt powder/pellets were applied in July, followed by continuous monitoring for three months until the winter snowfall. In this presentation, we will report preliminary results at this stage, including increased pH in the surface water in some main plots and the existence of powder/pellets trapped in the surface litter layers.