| Luoma Lake,as an important impoundment of the east route of the South-to-North Water Diversion Project,is an important source of drinking water for the cities of Xuzhou and Suqian.In order to provide a scientific basis for the qualified drinking water,this paper has analyzedthe chemical composition and distribution characteristics of lake water,the seasonal variation of fluoride and bromine ion and its health risk,the distribution of nutrient elements and the eutrophication of water.The main results are as follows:(1)The spatial and temporal distribution characteristics,health risks of fluoride ions in water bodies,sediments of Luoma Lake and the rivers entering the lake were clarified.Water samples and surface sediment samples were collected from 44 sampling points in Luoma Lake and the river into the lake in November 2019 and July 2020,respectively.The test results showed that the fluoride ion concentration in Luoma Lake and the river into the lake varied between 0.211 mg/L and 1.170mg/L,and there were 3 points greater than 1.0mg/L in all the sampling data.The exceed rate was 6.5%,and there was no exceed point in July 2020.Fluoride content in sediments varied from4.308-38.548 mg/kg,with an average value of 10.4mg/kg,higher than the average value of soil in Xuzhou area.The results of the health risk assessment of fluoride ion showed that in November 2019,there were 6 points with a risk greater than 1 for children,accounting for 35.3 %.In July 2020,the risk quotient of all children was less than 1,and there was no health risk.(2)The temporal and spatial distribution characteristics and health risks of bromide ions in water bodies and sediments of Luoma Lake and rivers entering the lake were clarified.Bromide ion concentration in the water samples at 43 effective sampling sites of Luoma Lake and the lakes was between 0.022-0.297 mg/L,and the temporal and spatial variation of bromide ion content was similar to that of fluoride ion in general.Under the influence of the inflow of lakes and the change of lake level water volume,the bromide ion concentration in July 2020 was significantly lower than that in November 2019.The bromide content in sediments varied from 0.020 to 2.230 mg/kg,with an average value of 0.426 mg/kg,and the spatial distribution was similar to that of bromide in water.The health risk of bromide ion in the lake area was low in the wet season,but the bromide ion concentration in 52 % of the sampling sites in the lake area was more than 0.2mg/L in November 2019,which was a high health risk and should be paid attention to.(3)The distribution characteristics of nutrient elements C,N and P in the water and sediments of Luoma Lake were analyzed.The contents of TOC,TN and TP in Luoma Lake sediments ranged from49.6-3670.5 mg/kg,313-2245 mg/kg and 162.951-261.364 mg/kg,respectively.The comprehensive pollution assessment results of sediment nitrogen and phosphorus showed that the FF value of Luoma Lake sediment comprehensive pollution index ranged from 0.68 to 2.69,indicating mild pollution.The average contents of TOC,TN and TP in Luoma Lake were 3.9mg/L,0.985mg/L and 0.096mg/L respectively.The nitrogen and phosphorus in most areas were in line with the Ⅲ water quality standard in Environmental Quality Standard for Surface Water(GB3838-2002),but the total phosphorus content in some sampling sites exceeded 0.1mg/L,which caused serious pollution.The comprehensive trophic state index method showed that the water quality of Luoma Lake in July 2020 was in moderate to mild eutrophication state,but the water quality near the entrance of the middle canal reached moderate eutrophication level.The paper has 39 pictures,22 tables,and 137 references. |
PDF Full Text Request