1,4-Dioxane biodegradation at low temperatures in Arctic groundwater samples.

Biodegradation of contaminants in cold environments remains poorly understood. While 1,4-dioxane is a known groundwater pollutant, its microbial degradation at low temperatures has not been thoroughly explored. Previous studies have focused on warmer regions or laboratory conditions. Arctic ecosystems face unique challenges due to low temperatures, which can slow microbial activity. It was already known that certain bacteria can degrade dioxane, but their performance in cold environments was uncertain. No prior work had resolved how dioxane degraders behave at temperatures below 10°C. This gap motivated researchers to test biostimulation and bioaugmentation strategies in Arctic conditions. Understanding these processes could help manage contamination in sensitive regions. This study addresses a critical knowledge gap in cold-climate bioremediation.

The study aimed to evaluate the biodegradation potential of 1,4-dioxane in Arctic groundwater at low temperatures. Researchers tested whether biostimulation or bioaugmentation could enhance degradation rates. They focused on two bacterial strains: one well-characterized and another isolated from Antarctica. The goal was to compare their performance at 4 and 14°C. The study also assessed natural attenuation as a baseline. By measuring degradation rates and microbial activity, the team sought to determine the feasibility of bioremediation in cold environments. This work could inform remediation strategies for Arctic regions. The results may guide future field applications in similar climates.

The researchers used microcosms containing groundwater and soil from an impacted site in Alaska. Three treatment conditions were tested: natural attenuation, biostimulation with 1-butanol and nutrients, and bioaugmentation with two bacterial strains. The microcosms were incubated at 4 and 14°C to simulate Arctic conditions. Dioxane concentrations were monitored over time. Protein content was measured to assess microbial biomass. Degradation rates were calculated based on dioxane loss and protein levels. The study compared degradation efficiency across treatments and temperatures. The experimental design allowed for direct comparisons between biostimulation and bioaugmentation. The approach focused on both source-zone and plume-edge contamination scenarios.

Biostimulation increased dioxane degradation by indigenous microbes at both 4 and 14°C. The degradation rate was about 0.01 mg dioxane per day per mg protein. At 14°C, bioaugmentation with CB1190 achieved the highest rate of 0.16 mg dioxane per day per mg protein. At 4°C, the rate dropped to 0.021 mg dioxane per day per mg protein. DVS 5a1 showed stable degradation rates at both temperatures: 0.018 and 0.015 mg dioxane per day per mg protein at 4 and 14°C, respectively. At low dioxane concentrations (500 µg L⁻¹), DVS 5a1 outperformed CB1190. Natural attenuation microcosms also showed significant degradation at 500 µg L⁻¹ over six months. These findings suggest that biostimulation and bioaugmentation can enhance dioxane degradation in cold environments.

The study demonstrates that dioxane biodegradation is feasible in Arctic groundwater under cold conditions. Biostimulation and bioaugmentation both enhanced degradation rates compared to natural attenuation. CB1190 performed best at 14°C but poorly at 4°C. DVS 5a1 maintained consistent performance at both temperatures. The strain outperformed CB1190 at low dioxane concentrations. Natural attenuation also showed promise for plume-edge conditions. These findings suggest that tailored bioremediation strategies could be effective in cold climates. The results support the potential for bioremediation in Arctic regions. The study provides a foundation for future field applications in sensitive ecosystems.