VARIATION OF POLYCYCLIC AROMATIC HYDROCARBON (PAH) CONTENTS IN THE VADOSE ZONE AND GROUNDWATER UNDER LONG-TERM IRRIGATION USING RECLAIMED WATER

Using reclaimed water for agricultural irrigation is one of the most important measures for alleviating the global water crisis. The polycyclic aromatic hydrocarbon (PAH) vertical distribution characteristics in the vadose zone under long-term reclaimed water irrigation and the corresponding impact on groundwater were studied by conducting a simulation experiment in the south-east suburb of Beijing. The simulation experiment designed two different long-term reclaimed water irrigation years, which were 98 and 236 years, respectively. The results showed that both treatments had a total PAH contents close to the background values (245-253 mu g kg?(1)) and the long-term reclaimed water irrigation did not result in a considerable PAH accumulation in soil profiles, which was supposed to be largely associated with the low PAH content of reclaimed water. The sources of PAH contamination in the vadose zone were mainly the combustion of fossil fuels and biomass by analysis of PAH isomer ratios. The total PAH contents in groundwater after percolation through the reclaimed water irrigation area was no more than 0.16 mu g l?(1) and the PAH removal rate of the vadose zone reached 97.7%. We stated that the vadose zone in the study area has excellent pollution prevention properties for PAHs under long-term high-quality reclaimed water irrigation. (c) 2019 John Wiley & Sons, Ltd.