Toxicity Effect Of Coal Fly Ash Particle Size On Daphnia Magna

There is a large amount of coal fly ash produced in our country,and it is being popularized and utilized on a large scale at present.In recent years,many researches have reported the toxicity of coal fly ash to plants and aquatic organisms,and it is of great significance to carry out the environmental risk assessment of coal fly ash.However,the current research mainly focuses on the toxicity of coal fly ash lixivium solution without considering the difference of particle size and the toxicity of the particle itself.In this paper,the toxic effect of coal fly ash particle size on Daphnia magna was studied by using lignite-fired CFB boiler in a power plant in Jiangsu province as the research object and typical aquatic organism Daphnia magna as the test organism.The toxic effects of coal fly ash particles on Daphnia magna were studied,and the acute and chronic toxicity,population size and structure of Daphnia magna were analyzed by using the correlation coefficient(r)and the hazard quotients(HQ),the toxicity of coal fly ash particles and heavy metals and the risk of environmental exposure were discussed.The key toxic factors were determined.The main conclusions are as follows:(1)The test results of the physical and chemical properties of coal fly ash particles show that there are more coal fly ash particles between 28 and 150?m in size,and in non-sieved,fine(<28?m)and large(>150?m)coal fly ash particles,the content of harmful micronutrient from large to small was Zn>Cr>As>Pb>Cu>Cd,and the leaching rate of non-sieved,fine(<28?m)coal fly ash and large(>150?m)coal fly ash from large to small was As>Cr>Pb after 24 hours leaching in M7medium,the concentration of Zn,Cu and Cd in the leaching solution decreased due to the adsorption of coal fly ash,the leaching of heavy metals in fly ash is related to p H value.(2)The acute and chronic toxicity of coal fly ash to Daphnia magna showed that the 24 h-LC₅₀ values of non-sieved,fine particles(<28?m)and large particles(>150?m)coal fly ash particles were 15.25,13.74 and 14.96 g/L,respectively;When Daphnia magna was exposed to the above three levels of coal fly ash and five particles,organisms accounted delayed first brood,less number of produced neonates and reduced intrinsic rate of natural increase compared with the control group,there was significant difference(p<0.05),indicating that the toxicity of coal fly ash particles to Daphnia magna was obvious.(3)In terms of population size,the population number of Daphnia magna was significantly reduced by coal fly ash(p<0.05),which was 9?35%lower than that of the control group.The growth and reproduction ability of Daphnia magna recovered gradually after removal of coal fly ash particles,the population of Daphnia magna was increasing,and the inhibitory effect of fine particles(D<28?m)on population of Daphnia magna was significantly greater than that of unsieved and large particles(D>150?m)(p<0.05),to a certain extent,fine particles(<28?m)coal fly ash particles are more toxic.(4)The results of correlation coefficient(r)and hazard quotients(HQ)showed that the main toxic factors to Daphnia magna in coal fly ash solution were coal fly ash particles,followed by heavy metals Cr and As.The hazard quotients(HQ)show that the exposure risk of coal fly ash particles to Daphnia magna in water was much higher than that of heavy metals in coal fly ash solution,fine particles(<28?m)coal fly ash particles are more toxic and its exposure risk to the environment is higher.This paper has 27 pictures,18 tables,and 143 references.