Vertical Migration Characteristics and Effect Factors of BaP in Contaminated Soil Under Rainwater Infiltration

Abstract

High ring polycyclic aromatic hydrocarbons such as benzo(a)pyrene (BaP) do not easily degrade and they are highly toxic. An improved understanding of how BaP migrates through soil will enable more informed control of their soil-to-groundwater contamination. We simulated the vertical migration of BaP through soil in a column in a series of experiments and combined these with Hydrus-1D modeling to investigate the impact of organic matter concentration, vegetation cover, infiltration coefficient, rainfall interval, and rainfall duration on BaP migration over time. We report BaP mobility to decrease with increased soil organic matter content, and with a change from continuous rainfall (daily) to periodic rainfall (at 5 d intervals); and for vegetation, increased soil infiltration coefficient, and extended duration of rainfall (from 6 to 120 h) to improve BaP soil mobility. The Hydrus-1D model was used to simulate the migration of BaP through soils over a 5 y period under different infiltration coefficients and to evaluate how long-term rainfall interval and rainfall duration affected BaP migration. Simulation results were consistent with experimental findings. Based on long-term experimental simulation of rainfall data for Beijing, BaP would easily be adsorbed by soil, but it would not easily migrate through it. However, simulation results also indicate that groundwater pollution in contaminated sites may occur after 22 y. Thus, we improve understanding of the migration of BaP in soil at polluted sites, the potential for contaminating groundwater, and the time frame within which remedial action is required to prevent groundwater contamination.