| Objective: We conducted the study is to establish the ion chromatography of perchlorate in drinking water,and investigate the levels and pollution characteristics of perchlorate in 48 main water plants of 16 prefecture level cities in Anhui.Six water plants in Hefei were selected as the monitor sites.Drinking water was sampled for detecting the distribution of perchlorate,respectively during the dry season and the flood season.According to the changes of perchlorate in proximal,middle and distal segments of water supply network,we can initially evaluate the health risk of perchlorate.Finally,we expected the study can provide preference for the standard limit value and test method of perchlorate in drinking water.Methods:(1)Referring to the ion chromatography for perchlorate at home and abroad,we explored the best condition for detecting the levels of perchlorate in water by trial and error,and established a method for the determination of perchlorate in drinking water.(2)From June to July 2016,we collected 144 samples,including source water,tap water and finished water,of 48 main water plants in 16 prefecture-level cities of Anhui Province,then to find the distribution characteristics of perchlorate.Besides,we adopted t test to analysis the differences of perchlorate levels in groundwater as water supply and surfacewater as water supply.Moreover,we collected 60 samples,including source water,product water and finished water in six waterworks of Hefei in November 2016 and August 2017.Then we adopted t test to analysis distribution characteristics of perchlorate in Hefei.(3)The study adopted the water environmental health risk assessment model which is recommended by United States Environmental Protection Agency(EPA),to preliminarily assess the health risk of perchlorate on people through the drinking water pathway.Results:(1)The study set up the ion chromatography for perchlorate determination in drinking water.It had a good linear relationship in the range of 2-50 μg/L,the correlation coefficient(r)= 0.9995.The recovery rate,the RSD and the detection limit respectively were 96.7% ~104.8%,1.5%~5.0%,0.52 μg/L.(2)The detection rate of perchlorate in source water and drinking water of 48 main water plants in 16 prefecture-level cities of Anhui Province was 91.67% and 86.46% respectively.The total positive rate was 88.19%.The ranges of perchlorate levels in source water,product water and finished water were from no detection to 14.70μg/L,14.21μg/L and 12.50μg/L,respectively.And the mean were 7.33μg/L,5.88μg/L and 4.65μg/L,respectively.(3)The distribution trend of perchlorate in every water plants,was highest in source water,followed by product water and lowest in finished water.Source of different water plants is mainly divided into groundwater and surface water.Then in source water with groundwater as water supply,ranges of perchlorate levels of source water,tap water and finished water were from no detection to 13.21μg/L,8.90μg/L and 8.70μg/L,respectively.And perchlorate levels(X ±SD)(ug/L)were 6.88±4.57、4.64±2.72、4.03±2.87.Then in water plants viewed surface water as water supply,ranges of perchlorate levels of source water,tap water and finished water were from no detection to14.70μg/L,14.21μg/L,12.50μg/L respectively and perchlorate levels(X ±SD)(ug/L)were7.43±4.80、6.16±4.47、4.79±3.89 respectively.The perchlorate levels,of three water plants with groundwater as water supply in Bozhou,were obviously higher than the other three cities,more than 11μg/L in source water and 5μg/L in drinking water.The perchlorate concentrations,of the water plants viewed surface water as water supply in WH、TL、AQ、CZ,were higher than another areas,exceeding 13μg/L in source water and 9μg/L in drinking water.(4)During low water period,the perchlorate levels in source water,tap water and finished water of the six main Waterworks of Hefei were 4.09-11.60 ug/L,2.09-8.65 ug/L and nd-5.80 ug/L.And perchlorate levels in source water,plant water and tap water(in near segment,in middle segment,in distal segment)(X ±SD)(ug/L)were 6.72±2.59、4.74±2.18、3.93±1.32、2.76±1.08、1.31±1.23,respectively.The detection rate was 93.3%;During abundant water period,the perchlorate levels 2.60-8.63 ug/L、1.40-6.27 ug/L、nd-4.75 ug/L.And perchlorate levels in source water,plant water and tap water(in near segment,in middle segment,in distal segment)(X ±SD)(ug/L)were 4.95±2.13、3.39±1.67、2.61±1.33、1.75±1.53、0.81±0.93.The detection rate was 83.3%.The perchlorate level in low water period was higher than in abundant water period.(5)The detection results do not exceed 15μg/L,which is safe concentration of perchlorate recommended by US EPA.But the contents of perchlorate in four WH,TL,AQ and CZ are approximately close to 15μg/L.The non-carcinogenic risk index of perchlorate in source water,tap water and finished water in Anhui is from 0 to 1.05,partly more than 1 in source and tap water,however,lower than 1 in finished water of every plant.There is no negative effect on human health for long time to drink.Conclusions:(1)Although there are different levels of perchlorate pollution in Anhui,the detection concentrations do not exceed safe concentration of perchlorate recommended by US EPA.Overall trend is highest in source water,middle in tap water and lowest in finished water.But the detection levels were not more than 15μg/L,which is safe concentration of perchlorate recommended by US EPA(2)The northern part of Anhui mostly takes groundwater as the source of water,while the southern part of Anhui mainly takes surface water as the source water.The perchlorate content in the source water and drinking water,of water plants with groundwater as water supply,is lower than the area with surface water as water supply.The perchlorate content,with groundwater as water supply in BZ,is obviously higher than other three cities.The perchlorate contents,of the water plants viewed surface water as water supply in WH、TL、AQ、CZ,are higher than another regions,closing to 15μg/L in source water.This phenomenon should catch our attention(3)The perchlorate content in six Waterworks of Hefei carried a trend,that is highest in source water,middle in tap water and lowest in finished water,higher in dry season than in abundant water period.In addition,the perchlorate concentrations in finished water decreased with the increase of pipeline transportation distance(4)The study assesses preliminarily the acceptable non carcinogenic risk index of perchlorate in drinking water.Although there is not obvious health hazard to human,it should also cause concern. |
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