Studies On Biological Monitoring Of PAHs In The Surface Water Of The Three Gorges Reservoir Area (TGRA)

In recent years,overpopulation,rapid urbanization and industrial growth caused significant disturbance in the Three Gorges Reservoir Area(TGRA)aquatic ecosystem.Augmented anthropogenic activities and pollution heavily deteriorated the surface water quality of the TGRA,which put immense pressure on the ecological integrity and freshwater resources in this region.PAHs are ubiquitous organic compounds and highly persistent in the riverine system of China and all over the world,which are carcinogenic,deforming and mutagenic.Moreover,chronic influxes of PAHs in water can lead to bioaccumulation in the food chain and bio-magnification at various trophic levels.Exposure to PAHs can result in human health risk.Pollutant monitoring of TGRA is important to the public health,food security and sustainable development.Nonetheless,the previous studies for pollutant monitoring in the TGRA mainly focused on conventional chemical methods and rarely on biological monitoring and toxicological risk assessment.Therefore,We not only use the traditional analytical detection methods,but also use genetic biomarkers and transgenic zebrafish Tg(cyp1a:gfp)to reveal the real status of PAHs and the biological effects at the highest impounding level of 175 m in the TGRA.Our results show that:(1)Concentration of (?)PAHs in the TGRA is 23-1630ng/L.The spatial distributing changes of (?)PAHs showed that the concentration of PAHs from upstream to downstream had downward trend.In terms of composition,low molecular weight PAHs(Nap,Ace,Ant and Phe)took the priority,particularly Nap account for the largest proportion in all sample points.(2)Based on the toxicological indices(hatchability,mortality,aberration rate,body length,weight and heart rate)after exposed zebrafish experiment,we found that water of TGRA had not obvious effect on early embryos development of zebrafish.From gene expression in different sample points,we found genes response in midstream were higher than upstream and downstream,and cyp1 a gene had the highest sensitivity and the induction effect.(3)The results of transgenic zebrafish Tg(cyp1a:gfp)embryos exposure test showed the change and trend of green fluorescence value of GEP are essentially consistent with mRNA expression of cyp1 a.(4)Comprehensive analysis the concentration of (?)PAHs in the TGRA and gene expression,we found the expression of 8 genes consistent with the trend of concentration of (?)PAHs.Generally,cyp1 a has the obvious superiority to monitor PAHs as a biomarker,especially to high molecular weight PAHs.