Formatted Title
Natural Attenuation of Vinyl Chloride and Butyl Acrylate Released in the East Palestine, Ohio, Train Derailment
Background/Objectives
Background/Objectives. On February 3, 2023, a freight train carrying hazardous chemicals, including vinyl chloride (VC) and butyl acrylate (BA), derailed in East Palestine, OH. To prevent the risk of explosions at the site of the accident, several cars were punctured to drain nearly 1 million pounds of VC, a human carcinogen, and BA into makeshift pits for a ‘controlled burn’. This action generated combustion byproducts of unknown amounts. Toxins from this controlled burn entered multiple streams (i.e., Sulphur Run, Leslie Run) that ultimately discharge into the Ohio River, which supplies drinking water to millions of people. Natural attenuation of environmental contaminants, primarily driven by biological processes, constitutes a significant mechanism for diminishing the concentration and toxicity of pollutants in the environment. Natural attenuation processes unfold gradually over time as the microbiology responds to the released contaminants. To assess the response creek microbiomes to the spill, surface water and streambed sediments were collected to conduct a microcosm treatability study and a survey of known biodegradation biomarker genes using molecular biological tools (MBTs).
Approach/Activities
Approach/Activities. Creek sediment and surface water were collected from 17 locations along Sulphur Run and Leslie Run and connected waterbodies in the East Palestine area on June 11, 2023, along with five residential water wells. DNA was extracted to perform 16S rRNA gene amplicon sequencing and qPCR. Specifically, the presence and abundance of known biodegradation biomarker genes for aerobic (i.e., etnC and etnE) and anaerobic (i.e., 16S rRNA genes of Dehalococcoides and Dehalogenimonas, VC reductive dehalogenases) VC biodegradation were determined using a high throughput qPCR approach (i.e., QuantArray®, Microbial Insights Inc.). In addition, microcosm treatability studies assessed VC and BA biodegradation under oxic and anoxic incubation conditions.
Results/Lessons Learned
Results/Lessons Learned. Reductive dechlorination of VC to ethene was observed in microcosms established with sediment samples collected immediately downstream of the derailment site (i.e., Sulphur Run sampling locations), which were most affected by VC spilled during the accident. Dehalococcoides (Dhc) cell numbers increased significantly during VC-to-ethene reductive dechlorination. Microcosms established with samples from non-impacted sites (e.g., Leslie Run upstream of the confluence with Sulphur Run) showed no VC to ethene reductive dechlorination activity following a 3-month incubation period. Aerobic degradation of VC was observed in all 12 sediment samples tested, suggesting a broad distribution of microorganisms catalyzing aerobic VC oxidation. Aerobic VC degradation started after a lag phase of 3 to 4 weeks in all microcosms, after which VC was rapidly degraded within 1 to 2 weeks. Repeated additions of VC resulted in the enrichment of Mycobacterium populations, which accounted for up to 35% of the microbial community, suggesting a role in aerobic VC degradation. Anerobic BA degradation occurred rapidly in all microcosms and the amended BA was completely degraded within 2 to 3 weeks associated with the formation of n-butanol and acrylate, demonstrating the breakage of the ester bond of BA. The results indicate that natural microbiomes in Sulphur Run and the connected streams possess the capacity for VC and BA degradation, suggesting strong natural attenuation potential for these toxins.