| Persistent organic pollutants (POPs), such as polycyclic aromatic hydrocarbons (PAH) and polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF), are anthropogenic environmental contaminants. Once emitted, these compounds travel from their sources and deposit back to the earth. Three studies were devised to investigate the environmental fates of these compounds on local, regional, and global scales.; Paired atmosphere, corn kernel, and corn leaf samples from a farm in Ohio were analyzed for PCDD/F. Concentrations were below the detection limits in the corn kernels. Concentrations were 510 ± 75 fg/m3, 1300 ± 300 fg/m3, and 4.2 ± 1.2 ng/g lipids in the atmospheric gas- and particle-phases and in corn leaves, respectively. The partitioning of PCDD/F between the atmosphere and corn leaves is dependent on temperature and vapor pressure.; To investigate how far PAH travel in the northeastern region of the United States, vegetation samples were collected from urban, suburban, and rural locations. Total PAH burdens (ng/cm2) in the rural vegetation samples were 10 times lower than in the urban samples, confirming that atmospheric PAH burdens are higher near source regions. The total leaf surface area was estimated for each type of land area, and using these PAH burdens, a flow of 160 t/yr of PAH to vegetation was calculated.; Finally, we measured PCDD/F in tree bark and soil samples collected globally. These data indicated that PCDD/F do not move appreciably from warm to cold latitudes. Total concentrations in bark can be used to estimate total fluxes to soil in a particular region. The homologue profiles for each pair of bark and soil samples fell into three categories: (1) bark and soil both resembled source profiles; (2) bark and soil both resembled sink profiles; (3) bark resembled a source profile but the soil resembled a sink profile. This variation may be due to the proximity of sampling locations to sources. Anthropogenic emissions of nitrogen oxides (NOx) are highly correlated to PCDD/F soil fluxes, and we used this regression to estimate global PCDD/F fluxes to soil on the same spatial scale as the NOx data. Total PCDD/F deposition to the earth is about 3–10 t/yr. |
