S. Vollmuth et al., FORMATION OF POLYCHLORINATED DIBENZO-P-DIOXINS AND POLYCHLORINATED DIBENZOFURANS DURING THE PHOTOLYSIS OF PENTACHLOROPHENOL-CONTAINING WATER, Environmental science & technology, 28(6), 1994, pp. 1145-1149
Purification of seepage water or wastewater by UV irradiation for the
destruction of organic impurities is an upcoming method for water trea
tment. Seepage water of refuse dumps contains, besides other organic c
ompounds, high concentrations of pentachlorophenol (PCP) and tetrachlo
rophenols (TCP). During the UV irradiation of PCP-containing water sam
ples, the formation of polychlorinated dibenzo-p-dioxins (PCDD) and po
lychlorinated dibenzofurans (PCDF) is possible. The toxicity equivalen
ce value (TEQ) of the PCDDs/PCDFs increased in an irradiated solution
containing purified PCP about by a factor of 150. In samples of techni
cal PCP and seepage water with high TEQ, we found a decrease of the TE
Q value, for example, the TEQ of 1931.0 pg/L of PCDD in technical PCP
is reduced to 99,0 pg/L. During the irradiation, heptachlorinated dibe
nzo-p-dioxins and heptachlorinated dibenzofurans were formed by the co
ndensation of PCP and TCPs, which were decomposition products of PCP,
and the photochemical decomposition of octachlorodibenzo-p-dioxin (OCD
D). The ratios of the formed heptachlorinated congeners point to a spe
cial decomposition way of the OCDD and OCDF in irradiated water sample
s. OCDD preferently loses a chlorine atom in the peri-position (positi
ons 1, 4, 6, and 9). OCDF preferently loses a chlorine atom only in th
e peri-position next to the C-C bridge (positions 1 and 9).