Occurrence, removal and bioaccumulation of steroid estrogens in Dianchi Lake catchment, China

The occurrence, removal and bioaccumulation of steroid estrogens such as the natural estrone (E1), 17β-estradiol (E2) and estriol (E3), as well as the synthetic 17α-ethynylestradiol (EE2) were investigated in Dianchi Lake catchment, China. The results show that traditional secondary treatment processes in eight sewage treatment plants (STPs) of Kunming were not efficient enough to completely remove steroid estrogens, but ultraviolet (UV) photodegradation in advanced treatment displayed more effectively for the removal of the residual compounds. The amount of total steroid estrogens (∑SEs) discharged to Dianchi Lake catchment by the eight STPs was 35.8g/day, in which STP-3 was the dominant source, accounting for 50.8%. Because of the pollution input from treated and untreated sewages, estrogens were widely detected in surface water and sediment samples collected from 21 inflow rivers of Dianchi Lake, 10 National Surface Water Quality Monitoring Sites of the lake itself and its unique outflow river, with the mean concentration of ∑SEs in the range of 5.3-798.2ng/L (water) and 3.7-202.4ng/g (dry weight, sediment), 1.5-39.2ng/L (water) and 2.7-20.9ng/g (sediment), and 4.2ng/L (water) and 6.6ng/g (sediment), respectively. Due to the continuous input of estrogens to Dianchi Lake from STPs and inflow rivers, present estrogen levels in various tissues of wild fish species sampled from the lake (2013) were higher than the values detected in the previous years (2009 and 2010). The bioaccumulation of steroid estrogens in wild fish species from different sampling sites was in the order of STP-5>Dianchi Lake (2013)>Dianchi Lake (2010)≈Dianchi Lake (2009)≫field control>laboratory control, which is mainly affected by exposure concentrations. By employing risk quotient (RQ), it is found that eco-toxicological risk of steroid estrogens in Dianchi Lake catchment was in a sequence of 22 rivers>effluents of eight STPs>Dianchi Lake (2013)>Dianchi Lake (2010), and high RQs were found in EE2, which should be controlled preferentially in this catchment.