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Biomass burning in Asia has been widely studied owing to its adverse effects on visibility, human health, and global climate. However the impact of rice straw burning on polychlorinated dibenzo-p-dioxin and dibenzofurans (PCDD/Fs) and polybrominated diphenyl ethers (PBDEs) concentrations is not known. In this study concentrations of these pollutants were measured at a farm site and two nearby sites during rice straw (open) burning and non-burning periods. During non-burning periods atmospheric PCDD/F and PBDE concentrations ranged from 0.0263 to 0.0329 pg I-TEQ/Nm 3 and 43.5 to 58.3 pg/Nm 3 respectively, and were similar at all of the sites. During rice straw burning periods PCDD/F and PBDE concentrations measured near the combustion (farm) site increased dramatically by six to twenty times. The strong correlation between the natural logarithm of PBDE and PCDD/F concentrations (r ¼ 0.949, p < 0.01) at each site indicates that the elevated PCDD/Fs and PBDEs were due to emissions from the rice straw burning. The calculated emission factors, determined using the burned carbon method and the Industrial Source Complex Short-Term Dispersion Model (ISCST3), ranged from 12.6 to 14.5 ng TEQ/kg Cburned and 11.7 to 14.5 mg/kg Cburned, for PCDD/Fs and PBDEs respectively. The PBDE emission factors were at least 38 times higher than those of PCDD/Fs, revealing that rice straw burning is an important PBDE emission source. |
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