Release of Organochlorine Pollutants from Forest Fires: 1. Emission Factors and Revisiting Their Emissions in the Himalayan Regions

Worldwide
forest fires have occurred frequently in recent years,
a result of which may be the emission of so-called “legacy”
organochlorine pollutants (OCPs) accumulated in forests. However,
few studies have measured the emission factors (EFs) of the toxicity
of the OCPs from forest fires. In this study, the EFs of vegetation
burning were observed in forests along the altitudinal gradient from
1000 to 4200 m, and the EFs of ∑DDTs (dechlorodiphenylthrichloroethanes),
HCB (hexachlorobenzene), ∑HCHs (hexachlorocyclohexanes), and
∑PCBs (polychlorinated biphenyls) were 2050 ± 1175, 379
± 409, 48 ± 51, and 65 ± 59 ng/kg, respectively. Re-evaporation
was the primary mechanism of the emission of OCP from forest fires.
The masses of HCB, β-HCH, o,p′-DDD, p,p′-DDD,
and PCB-28 in smoke increased 3–7 times compared with those
in unburnt vegetation, suggesting the formation of these pollutants
by the pyrolysis of biomass or other pollutants. Based on the observed
EFs, previously estimated quantities of fire-emitted OCPs in the Himalayan
regions were revisited. The DDT emissions from the Himalayan forest
fires increased ∼70% compared with the previous estimation
(from 19 to 32 kg/year). This highlighted that the EF observations
could decrease the uncertainties of estimating OCP emissions from
forest fires, which is helpful in revealing the potential roles of
forest fires on global POP cycling.