To understand the effect of leaf-surface pesticides on emissions of
PCDD/F during biomass
burns, nine combustion experiments simulating the open burning of biomass were conducted. Needles and branches of Pinus taeda (Loblolly pine) were sprayed with the
pesticide 2,4-dichlorophenoxyacetic acid (2,4-D) at 1 and 10 times the manufacturer's recommended application concentration. The biomass was then dried overnight, burned in an open
burn test facility, and emission samples were collected, analyzed, and compared against emission samples from burning untreated biomass. Blank tests and analysis of
PCDD/F in the raw biomass were also performed. Emission results from burning a water-sprayed control show a ~20-fold increase in
PCDD/F levels above that of the raw biomass alone, implicating combustive formation versus simple volatilization. Results from
burns of pine branches sprayed with
pesticide showed a statistically significant increase in the
PCDD/F TEQ emissions when burning biomass at ten times the recommended
pesticide concentration (from 0.22 to 1.14 ng TEQ/kg
carbon burned (C(b)), both ND = 0). Similarly, a 150-fold increase in the total
PCDD/F congener mass (tetra- to octa-chlorinated D/F) above that of the control was observed (from 52 to 7800 ng/kg C(b)), confirming combustive formation of
PCDD/F from
2,4-D. More replicate testing is needed to evaluate effects at lower
pesticide concentrations.