Temporal And Spatial Distribution And Influencing Factors Of The Taste And Odor Compounds From Algae In Urban Water Of Wuhan

In recent years,domestic water odor events occur frequently,which has attracted extensive attention.2-MIB,β-cyclocitral,GSM and β-ionone is the most common and widely distributed four typical taste and odor compounds from algal.Different types of water bodies have different hydrological conditions,water quality and use functions,resulting in great differences in the distribution of algal odor substances.However,at present,the research on algal odor substances mostly focuses on a certain type of water body,and little is known about the distribution differences of algal odor substances in different types of water bodies.Therefore,this study takes four types of water bodies(lakes,rivers,ponds,Yangtze and Han rivers)in Hanyang District as the research object,and investigates and analyzes the content and distribution of algal odor substances in spring,summer,autumn and winter.On this basis,in order to further understand the source,distribution and influencing factors of algal odor substances in Hanyang District,algal biomass and community structure,water temperature,total nitrogen,total phosphorus,ammonia nitrogen,chlorophyll a and other water quality factors were detected.The specific research contents and results are as follows:(1)Headspace solid phase microextraction gas chromatography mass spectrometry was used to analyze 2-MIB,β-cyclocitral,GSM and β-ionone four odor substances were detected qualitatively and quantitatively.The results showed that four taste and odor compounds were common in Hanyang District,and the detection rates were between 72.0% and 97.2%,and at least one algal odor substance was detected in all samples.At the same time,compared with β-cyclocitral and β-ionone,the detection rate of 2-MIB and GSM,the number of samples exceeding the odor threshold and the impact on human senses are more serious.Therefore,2-MIB and GSM have a greater impact on the peculiar smell of water in Hanyang District.(2)In terms of the pollution degree of different types of water bodies by four kinds of algae source odor substances,the pollution degree of river algae source odor substances is the most serious,followed by lakes and ponds,and the odor pollution of the Yangtze River and Hanjiang River(Hanyang section)is relatively light.At the same time,high concentration of 2-MIB,β-cyclocitral and GSM are more concentrated in slow flow water bodies(such as rivers,lakes and ponds),while high concentrations β-ionone mainly appears in the Yangtze River and Han River.(3)The seasonal variation of four kinds of algae odor substances in different types of water bodies is different.The concentrations of 2-MIB and GSM in river and lake water bodies were higher in summer and autumn(June and September)than in winter and spring.However,the concentrations of 2-MIB and GSM in pond water bodies were the highest in spring,followed by winter,and the lowest in summer and autumn.The detected concentrations of 2-MIB and GSM in the Yangtze River and Hanjiang River are not high(ND ～ 5.18 ng/L and ND ～ 6.65 ng/L),the fluctuation is small,and the seasonal variation is not obvious.The seasonal variation laws ofβ-cyclocitral and β-ionone concentrations in different types of water bodies are different,but the concentration of β-cyclocitral is always the lowest in autumn andβ-ionone reaches the maximum in winter.(4)Through qualitative and quantitative analysis of planktonic algae,7 phyla and 51 genera were identified.Different water types have a great impact on algae biomass,The average biomass of phytoplankton in the Yangtze and Han rivers is lower than that of the other three water types because of their fast flow velocity,strong exchange capacity and low nitrogen and phosphorus content.In addition,the distribution of algae also has obvious seasonal characteristics.The number of algae in autumn is more than that in summer and more than that in spring and winter.At the same time,with the change of seasons,the algae community structure in Hanyang district changed,and the dominant algae species gradually changed from diatom to cyanobacteria and green algae.(5)RDA analysis showed that there was a significant and strong correlation between Oscillatoria,Aphanizomenon,Trachelomonas,Selenastrum bibraianum,Phacus,staurastrum and taste odor compounds(P < 0.05),indicating that they had a great impact on the distribution of taste and odor compounds from algae sources in Hanyang District.RDA analysis and Spearman correlation analysis showed that Oscillatoria,Oscillatoria,Aphanizomenon,Trachelomonas,Selenastrum bibraianum,Phacus were the main algae influencing factors affecting the distribution of 2-MIB and GSM in Hanyang District.The relationship between β-cyclocitral and β-ionone and algal biomass was not significant.Among them,Oscillatoria is one of the main sources of 2-MIB in Hanyang District,and Aphanizomenon may be one of the sources of GSM in Hanyang District.At the same time,T,p H,TN and TP can affect the ability of algae to produce odor substances by affecting algae biomass and community structure.Therefore,controlling the input of nutrients and organic matter and cyanobacteria biomass can effectively deal with the problem of peculiar smell in Hanyang District.