Would you buy a used couch from a smoker’s home? You can’t get the odor out. That odor isn’t the ghost of cigarettes past—it is tobacco-smoke chemicals retained in the furniture, part of what is called thirdhand smoke.
Researchers exposed cotton and polyester fabrics to cigarette smoke and found that nicotine, related alkaloids, and tobacco-specific nitrosamines were still present 19 months later.1 In a study, clean cotton pillows were placed in the homes of people who had recently stopped smoking. With no new smoking occurring, in only three weeks, each small 426-g cotton pillow accumulated an average of 21.5 µg of nicotine, not just in the pillowcase, but within the fabric and cotton filling.2 The nicotine came from thirdhand smoke reservoirs in the homes.
Aquifers behave in an analogous way.
Both chlorinated solvents and petroleum hydrocarbons partition onto aquifer solids and natural organic matter. They diffuse from transmissive sand and gravels into less-permeable silts and clays. When the primary source is removed or treated, the concentration gradient reverses. Stored contaminants begin moving back toward the cleaner groundwater. What was once a contaminant sink becomes a secondary source.
Chapman and Parker documented this at a TCE DNAPL site. After the source was hydraulically isolated, groundwater TCE concentrations initially fell dramatically but then persisted as TCE stored in an underlying aquitard diffused back into the transmissive aquifer.3, 4
The phenomenon isn’t limited to chlorinated solvents. Aelion found that petroleum contamination increased with clay content, while benzene and toluene biodegradation was lower in clay-rich sediment than in sand. Greater sorption and slower biodegradation were identified as likely contributors to the higher contaminant concentrations in the fine-grained sediments.5, 6
At RPI, we offer free laboratory analysis of groundwater and aquifer solids to help characterize the contaminant mass that groundwater sampling alone will not reveal.
Sometimes, after you’ve treated the obvious source, the source you didn’t know was there becomes the one that matters. Don’t wait until it does.
References:
Uses of Various Activated Carbons in In Situ Remediation
October 15th at 12:00 EST
Activated carbon is widely used in environmental remediation—but not all activated carbons are the same, and surface area alone does not determine how well they perform.
This webinar takes a practical look inside activated carbon: how it is manufactured, its pore structure, and how contaminants move through the carbon and become adsorbed.
We’ll compare coconut, coal, re-agglomerated coal, and wood-based carbons and examine how pore size, molecular structure, solubility, and contaminant concentration influence adsorption and selectivity.
We’ll then move from the carbon particle to the subsurface, exploring granular, powdered, and colloidal carbon; microbial colonization and biological regeneration of adsorption capacity; and why emplacement and distribution can be just as important as the carbon itself.
The goal is simple: give practitioners a better understanding of what activated carbon does in situ and the tools to ask better questions when selecting and applying it for in situ remediation.