Study On Corticosteroids In Water Environments Of The Pearl River Delta

Studies on environmental endocrine disrupting chemicals?EDCs?in aquatic environments have predominantly focused on the estrogenic effects of sex steroids that have received special attention owing to their potency.As a class of“emerging”non-sexual steroidal EDCs,corticosteroids?CSs?are received with increasing concern in recent years.CSs including glucocorticoids?GCs?and mineralocorticoids?MCs?are other groups of steroid hormones having important physiological functions.Previous research mainly focused on the occurrence of a few GCs in sewage treatment plants and other point sources.However,systematic studies on the monitoring of CSs in natural aquatic environments are relatively limited.In this study,24 kinds of natural and synthetic corticosteroids?including 21GCs and 3 MCs?were selected as the research objects.To this end,we have established a detection method of the CSs concentration in complex environmental by the technology of full-automatic solid-phase extraction and high-performance liquid chromatography tandem mass spectrometry.By using this method,the concentration level and distribution characteristics of CSs in four rivers of Pearl River Delta?including river water source and urban rivers?were investigated and researched.In addition,we also conducted an ecological risk assessment of the CSs in the study area,analyzed the main sources of pollution of CSs in urban rivers,and screened for potential indicators of CSs pollution.The results are as follows:1.Established a high-performance liquid chromatography-electrospray tandem mass spectrometry?HPLC-ESI-MS/MS?analysis method for the simultaneous determination of 24 CSs in rivers of the Pearl River Delta.The water sample was separated by full-automatic solid-phase extraction and purification,C₈ reversed-phase chromatography column,and the positive and negative ion modes?ESI±?were used for signal acquisition and measurement in the dynamic multiple reaction monitoring?DMRM?mode,and the internal standard method was used for quantification.The 24CSs have a good linear relationship within the range of 1.0-100 ng·L^-1?R²>0.99?.The limit of detection?LOD?and the limit of quantitation?LOQ?of the method is 0.09-0.46ng·L^-11 and 0.17-0.68 ng·L^-1,respectively.The average recovery of matrix spiked was 68.8%-108.7%?n=3?,and the relative standard deviation was 0.1%-8.1%.This method has the characteristics of good selectivity,high sensitivity,and good reproducibility.2.The total concentration of CSs??CSs?in the four rivers of the Pearl River Delta ranged from<LOQ to 83.3ng·L^-1,and the overall pollution level was:Guangzhou section of the Pearl River>Dongguan section of the Dongjiang River>Shiziyang Waterway>Foshan section of the Beijiang River.Showing a tendency to increase from upstream to midstream or downstream,and then decay toward the estuary.Risk assessment found that the Pearl River Delta River was generally at a medium to high ecological risk level,and the contribution mainly comes from synthetic corticosteroids,which may already pose a threat to local aquatic life.3.The concentration of?CSs in the drinking water source area of??the Pearl River Delta was between 0.29 and 8.7 ng·L-1.The main pollution is synthesized GCs.Redundancy analysis shows that most CSs in the source water has correlations with water temperature?T?,conductivity?COND?,pH,and dissolved oxygen?DO?,indicating that the changes in the above environmental factors may affect the occurrence and distribution of CSs in the source water.The hazard index?HI?of CSs in water sources is between<0.1 and 0.65,which is at a low to medium risk level.4.An in-depth investigation of the urban section of the river—the Guangzhou section of the Pearl River found that the main stream and tributary?CSs concentration ranges?average/median value?were<LOQ-94ng·L^-1(7.7/3.1 ng·L^-1)and 0.24-7.2 ng·L-1?1.0/1.6ng·L-1?.The overall performance the trend,which was increase at first then decrease,was along the upstream to the downstream.In addition,the distribution of the CSs concentration showing which in the dry season is higher than that in the wet season,and which in the tributary was higher than that in the main stream.The spatial and temporal distribution characteristics of CSs in urban rivers may be affected to the point source distribution of rivers,human activities,hydrological conditions,and water environmental parameters such as DO,Chla,and DOC.The risk assessment shows that the ecological risk of CSs in tributaries is higher than the main stream and which's risk assessment was at high level.According to statistical analysis,untreated sewage is the main source of CSs pollution in Guangzhou section of the Pearl River.In addition,COR and FLA can be used as potential indicators of natural and synthetic CSs pollution in urban water environment respectively.