Organic Micropollutants in Rivers Downstream of the Megacity Beijing: Sources and Mass Fluxes in a Large-Scale Wastewater Irrigation System

Abstract

The Haihe River System (HRS) drains the Chinese megacities Beijing and Tianjin, forming a large-scale irrigation system severely impacted by wastewater-borne pollution. The origin, temporal magnitudes, and annual mass fluxes of a wide range of pharmaceuticals, household chemicals, and pesticides were investigated in the HRS, which drains 70% of the wastewater discharged by 20 million people living in Beijing. Based on Chinese consumption statistics and our initial screening for 268 micropollutants using high-resolution mass spectrometry, 62 compounds were examined in space and time (2009-2010). The median concentrations ranged from 3 ng/L for metolachlor to 1100 ng/L for benzotriazole and sucralose. Concentrations of carbendazim, clarithromycin, diclofenac, and diuron exceed levels of ecotoxicological concern. Mass-flux analyses revealed that pharmaceuticals (5930 kg/year) and most household chemicals (5660 kg/year) originated from urban wastewaters, while the corrosion inhibitor benzotriazole entered the rivers through other pathways. Total pesticide residues amounted to 1550 kg/year. Per capita loads of pharmaceuticals in wastewater were lower than those in Europe, but are expected to increase in the near future. As 95% of the river water is diverted to irrigate agricultural soil, the loads of polar organic micropollutants transported with the water might pose a serious threat to food safety and groundwater quality.

Depth profile of persistent and emerging organic pollutants upstream of the Three Gorges Dam gathered in 2012/2013

“…High dilution and fast metabolism of these compounds in the environment may explain the lower concentrations observed in surface water. All other pharmaceutical active compounds observed in this study have already been reported either in surface waters or in the influent/effluent of wastewater treatment plants in China (Bu et al 2013;Heeb et al 2012;Liu and Wong 2013;Qi et al 2014). Values for carbamazepine and diclofenac which were determined in this study with higher mean abundance have been reported in surface water in China with concentration ranges from nondetection to 675 and nondetection to 843 ng L −1 , respectively (Bu et al 2013).…”

“…Regarding atrazine, seasonal fluctuations in concentration could be observed downstream of Beijing originating from agricultural areas. A distinct peak in atrazine level was observed in July 2009, whereas the levels in winter were near the LOQ which is an expected pattern for agricultural appliance of the pesticide (Heeb et al 2012). Our sampling campaign near the TGD in a more rural area of Hubei Province took place in September 2013 after the period Heeb et al observed the peak level of atrazine.…”

“…Thus, the input mainly occurs diffuse rather than from point sources (Heeb et al 2012). Regarding atrazine, seasonal fluctuations in concentration could be observed downstream of Beijing originating from agricultural areas.…”

“…7). These micropollutants represent a higher fraction than pesticides originating from agriculture (Heeb et al 2012). Nevertheless, both pose a threat to groundwater resources as they survive classic wastewater treatment techniques like coagulation and flocculation by 50-70 % and thus end up in surface water (Liu and Wong 2013).…”

Organic micropollutants in the Yangtze River: Seasonal occurrence and annual loads

“…The analytical method we used for applying 44 ISs for quantification has been reported elsewhere (Singer et al, 2010;Heeb et al, 2012). For targets where no structurally identical ISs were available, the ISs with the most similar retention times were used for quantification.…”