| With the continuous socio-economic development,emerging contaminants such as pharmaceuticals and artificial sweeteners are widely used in people’s daily life.Due to the persistence of emerging contaminants in the environment,their environmental behavior and residual levels in water bodies have received widespread attention.The special geological structures of karst areas,such as sinkholes and cracks,allow pollutants to quickly transfer from the surface to groundwater,thereby affecting groundwater quality.Based on the particularity of groundwater in karst areas,this study selected Guiyang,a representative karst city,as the research object,systematically sampled groundwater and typical pollution sources in Guiyang,and carried out a study on the concentration levels and spatial distribution characteristics of dissolved trace elements and emerging contaminants in typical pollution sources and groundwater in Guiyang.Finally,a comparative study was conducted on the recognition effect of a comprehensive index based on conventional indicators and new pollutant indicators on groundwater samples.The main results of the study are as follows:(1)The six trace elements in the study area did not exceed the national standard limit of Class III groundwater.According to the overall concentration of target trace elements in the research area,they can be divided into three groups,high abundance element Sr(>10μg/L),medium abundance element Ni(1μg/L～10μg/L)and low abundance elements Cd,Co,Cu and Li(<1μg/L).In the samples of different typical regions,the trace elements showed obvious spatial distribution characteristics,and the six elements all showed the distribution characteristics of urban center>rural-urban area>agricultural area,indicating that urban activities are an important factor affecting the trace elements in groundwater.(2)The distribution characteristics of 4 emerging contaminants in landfill and wastewater treatment plant(WWTP)were studied.The detection rate of caffeine and saccharin in each sampling point of the landfill was 100%,the highest concentration of caffeine was 1881.49 ng/L,followed by saccharin(195.26 ng/L).The detection concentration of Carbamazepine and acesulfame is generally low,with the total detection concentration ranging from ND to 10.41 ng/L.The total detectable concentration of 4 emerging contaminants in the input and output water of WWTPs ranged from 16.02 to 7533.08 ng/L,with caffeine and acesulfame as the main detectable target substances.The removal efficiency of the three treatment processes(A~2O,FBBR and CAST)for the target emerging contaminants were different.The A~2O process has a good removal effect on caffeine and acesulfame,with a removal rate of over 90%.The removal effect of different processes for saccharin was not much different,the removal efficiency ranged from 40.58%to 79.02%,with the lowest removal efficiency for WWTP S1.(3)Five target emerging contaminants were detected in the groundwater of Guiyang.The detection rate of caffeine,saccharin and carbendazim reached 100%,the detection rate of carbamazepine was the lowest,48%.The highest detectable concentration was caffeine(6274.52ng/L)>saccharin(209.47ng/L)>acesulfame(92.65ng/L)>carbendazim(3.14 ng/L)>carbamazepine(0.26 ng/L).The spatial distribution of caffeine,carbamazepine,acesulfame and saccharin in groundwater of different regions was characterized by higher concentration levels in urban centers and urban-rural areas than in agricultural areas,while the spatial distribution of carbendazim was reversed.The results showed that urban activities were important factors affecting caffeine,carbamazepine,acesulfame and saccharin,and agricultural activities were important factors affecting polymyxin.(4)Based on traditional indicators and emerging pollutant indicators,a comprehensive index(including urban comprehensive index Wc and agricultural comprehensive index Wa)was established for urban and agricultural areas in the study area.Groundwater samples were distinguished and it was found that the urban comprehensive index of urban groundwater samples was higher than that of agricultural area samples,while the agricultural comprehensive index showed the opposite trend.The comprehensive index analysis results show that compared with traditional indicators and new pollutant indicators,the combination of traditional indicators and new pollutant indicators has a more significant classification effect on groundwater samples,indicating that combining new pollutant indicators with traditional tracer indicators is a more effective indicator method for identifying the impact of activities from different sources on the groundwater environment. |
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