Wildfires
have destroyed multiple residential communities in California
in recent years. After fires in 2017 and 2018, high concentrations
of benzene and other volatile organic compounds (VOCs) were found
in public drinking water systems in fire-affected areas. The sources
of the contamination and appropriate remediation have been urgent
matters of investigation. This study characterizes target and nontarget
VOCs and semivolatile organic compounds (SVOCs) in water from a highly
contaminated service line after the 2018 Camp Fire (Paradise, CA).
Ninety-five organic compounds were identified or tentatively identified
in the service line. Laboratory combustion experiments with drinking
water pipes made of polyvinyl chloride (PVC), cross-linked polyethylene,
and high-density polyethylene and a review of the literature were
used to evaluate potential sources of the detected chemicals. Among
the service line contaminants were 32 compounds associated with PVC
pyrolysis and 28 organic compounds also associated with the pyrolysis
of polyethylene. The service line sample also contained 55 compounds
associated with uncontrolled burning of biomass and waste materials.
The findings support hypotheses that wildfires can contaminate drinking
water systems both by thermal damage to plastic pipes and intrusion
of smoke. Residual chlorine disinfectants in the water system modify
the contaminant distribution observed.
Most dielectrophoretic (DEP) separations of cells, nanoparticles, and other entities are carried out on microelectrode arrays or in microfluidic device formats. Less work has been directed at designing pipette-type formats that would allow dipping into and recovering specific analytes from samples in microtiter plate formats. In order to address this important area, we have fabricated micropipette tip devices containing a 2% agarose gel plug, a buffer chamber, and platinum electrode as the DEP collection device, to be used in combination with separate sample wells that contain a circular gold electrode. We demonstrated that 200 nm fluorescent nanoparticles could be isolated into DEP high-field regions and separated from 10 μm fluorescent microbeads in high conductance buffer (1× PBS) by applying an alternating current at 10 kHz with a peak-to-peak voltage (Vpp) of 160 Vpp. The collected nanoparticles were then transferred to a new buffer solution. We also demonstrated the DEP isolation and separation of genomic DNA (>50 kbps) from the 10 μm microbeads in high conductance buffer (1× PBS) with transfer of collected DNA to another solution.
We demonstrate a DNA double-write process that uses UV to pattern a uniquely designed DNA write material, which produces two distinct binding identities for hybridizing two different complementary DNA sequences. The process requires no modification to the DNA by chemical reagents and allows programmed DNA self-assembly and further UV patterning in the UV exposed and nonexposed areas. Multilayered DNA patterning with hybridization of fluorescently labeled complementary DNA sequences, biotin probe/fluorescent streptavidin complexes, and DNA patterns with 500 nm line widths were all demonstrated.
Wildfires in California have become more frequent and intense. Along with addressing the typical consequences of these natural disasters, two drinking water utilities discovered how to handle high levels of volatile organic compounds in their distribution systems as well as the physical and public relations effects of contamination.
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