[Comparative study on accumulation of Ah-receptor agonists in contaminated soil based on EROD bioassay and chemical...

The potential ecological risk by wastewater or reclaimed water for irrigation is of great concerns in recent years, but little work was done on the chronic toxicities through long term accumulation of persistent organic chemicals in soil. In present work, concentration of Ah-receptor agonists in soil organic extract was measured by an ethoxyresorfin O-deethylase (EROD) bioassay, which was calibrated and expressed by the 2, 3, 7, 8-tetrachlorodibenzo- p-dioxin (2, 3, 7, 8-TCDD) toxic equivalent (TEQbio). Simultaneously, 16 PAHs in soil were analyzed and their TEQs (total as TEQ(PAHs)) were calculated according to their toxic equivalent factors (TEFs) cited from literature. By bioassay, it was found that the concentration level of Ah-receptor agonists in soil irrigated using reclaimed water could be as high as 97.4 ng/kg, which was obviously higher than that in background soil using ground water irrigation regime (56.0 ng/kg). In comparing the results from bioassay and chemical analysis, the percentage of TEQ(PAHs) in TEQbio increased from 10.3% in background soil to 78.6% in the soil irrigated by reclaimed water. Use of reclaimed water for irrigation could result in the accumulation of Ah-receptor agonists in soil,and a major part of them in this case could be attributed to the accumulation of 16 priority PAHs in soils.