Dm. Pennise et Rm. Kamens, ATMOSPHERIC BEHAVIOR OF POLYCHLORINATED DIBENZO-P-DIOXINS AND DIBENZOFURANS AND THE EFFECT OF COMBUSTION TEMPERATURE, Environmental science & technology, 30(9), 1996, pp. 2832-2842
Emissions from the combustion of wood chips treated with pentachloroph
enol (PCP), polyvinyl chloride (PVC) plastic pipe shavings, and solid
PCP were injected into 25-m(3) outdoor Teflon film chambers and aged i
n sunlight under typical atmospheric conditions. The behavior of parti
culate and gas-phase polychlorinated dibenzo-p-dioxins and dibenzofura
ns (PCDDs and PCDFs) and polycyclic aromatic hydrocarbons (PAHs) was m
onitored over time. Only the tetra- and pentachlorinated dioxins and f
urans were shown to clearly partition at all into the gas phase in the
se experiments, perhaps due to high concentrations of TSP. Little or n
o reactivity was observed for PCDDs and PCDFs residing on particles re
sulting from high-temperature combustion (760-800 degrees C). Greater
photochemical reactivity of particle-bound PCDD/Fs resulted after low-
temperature combustion (350-380 PC), where fairly rapid photolysis com
peted with a production mechanism believed to begin with PCP. Photolys
is rates of PCD D/Fs appeared to increase with decreasing levels of ch
lorination, lending evidence to the observed enrichment of the higher
chlorinated species in the natural environment. On low-temperature com
bustion particles, model results showed that TCDD half-lives increased
from 0.4 under North Carolina summer outdoor conditions to 17 h under
wintertime conditions. For high-temperature combustion particles unde
r similar outdoor conditions, half-lives ranged from 6.8 to 62 h. For
these same conditions, model OCDD half-lives increased from 5 and 38 h
in low-temperature combustion experiments to 36 and 257 h in high-tem
perature combustion experiments. Experimental particle-phase PAH photo
lytic half-lives also increased from between 0.1 and 3.6 h in low-temp
erature combustion experiments to between 4.4 h and stability on high-
temperature combustion particles. These differ-ences may be explained
by differences in the particles generated from low- and high-temperatu
re combustion.