PAH Contamination of Urban Soils and Phytoremediation

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants, and some are known to be carcinogenic. PAH content of soils from three test sites including a refinery, a dismantled oil depot and a petrol filling station was analysed. Except dibenz(a,h)anthracene, 15 other PAHs were detected. Total PAH concentrations were in the order refinery > petrol filling station > oil depot. PAH levels were higher in the upper layer of soils at all sites. Three-ring and four-ring PAHs were found to be dominant at both depths. In greenhouse study, Cymbopogon jwarancusa and Helianthus annuus were screened for their ability to phytoremediate PAHs. Soil amendments to enhance their potential were also evaluated. Many C. jwarancusa treatments succumbed. In all vegetated treatments, the decline in TPAH levels was not only higher but also more rapid than the unplanted control. Total PAH degradation ranged from 95 to 99 % in C. jwarancusa at 240 DAT (days after treatment) and 75–84 % in H. annuus at 120 DAT. The final reduction of total PAHs in the unplanted control T0 was about 73 %. Rhizodegradation seemed to be the main mechanism of phytoremediation involved. Individual PAH degradation trends differed as did the efficacy of different amendments. Physiological parameters stabilised within 30–60 days of study.