Polycyclic Aromatic Hydrocarbon Accumulation in Urban, Suburban, and Rural Vegetation

Polycyclic aromatic hydrocarbons (PAH) partition from the atmosphere to vegetation, soil, water, and sediment. In an effort to quantitate vegetation's ability to scavenge PAH, we collected vegetation samples from urban, suburban, and rural locations during the summer and fall of 1995 and determined PAH burdens (ng/cm2) on a mass per total leaf surface area basis. The total PAH burdens in the rural vegetation samples were, on average, 10 times lower than in the urban samples, confirming that atmospheric PAH burdens are higher near presumed source regions. We also compared the individual PAH burden profiles for urban, suburban, and rural samples. All samples had similar profiles for fluorene, phenanthrene, fluoranthene, and pyrene, while the rural samples were depleted of anthracene, benzaanthracene, and several higher molecular weight PAH. In order to calculate a PAH to vegetation mass balance for the northeastern region of the United States, we divided this land area into rural, suburban, and urban classifications. We then identified the types of vegetation in each area and estimated the total leaf surface area. Using our PAH burdens, we calculated that about 160 t total PAH/yr flow from the atmosphere to vegetation. Vegetation in this region scavenges about 4% of the total amount of PAH emitted in this area.