Study On The Characteristics Of Microbial Sulfate Reduction Under Different Organic Matter Conditions In Black Odorous Water

With the increasing development of China's economy and the continuous improvement of urbanization,a large number of mineral energy resources dominated by coal and petroleum,are exploited,resulting in the continuous increase of sulfate concentration in the main freshwater bodies in China.Sulfate reduction is an important condition for the formation of black odor in the water bodies.Scholars at home and abroad mostly focus on the mechanism of sulfate reduction in oceans and sediments,but few studies on the water column of freshwater lakes.The degree of black odor in water is highly correlated with the changes of organic matter and sulfate concentration.However,the characteristics of different organic matters for microbial sulfate reduction and microbial community remain still unclear in the current studies on related topics.Based on this,the experiment of microbial sulfate reduction in water column was simulated in laboratory.The characteristics of microbial sulfate reduction and microbial community composition were studied in water column under different organic matter sources(algae-derived organic matter and weed-derived organic matter),including the effects of different organic matter sources and SO₄^2-concentration gradient conditions on microbial sulfate reduction and the characteristics of microbial community structure in water column during decomposition of different organic matter(algae-derived organic matter and weed-derived organic matter);The conclusions are as follows:(1)Organic matter from different sources significantly promoted microbial sulfate reduction in water column(algae-derived organic matter or weed-derived organic matter).With the increase of SO₄^2-concentration in water column,microbial sulfate reduction had no significant effect,which indicated that sulfide accumulation was toxic to microbial sulfate reduction.(2)The decomposition of organic matter in water column has significant influence on the changes of p H value and DO content of water column.At the beginning of the experiment,microorganisms decomposed organic matter and produced organic acid by fermentation,which reduced the p H value.Microorganisms metabolized and decomposed organic matter and consumed a large amount of DO in water,resulting in anaerobic water bodies.In anaerobic environment,sulfate reducing bacteria(SRB)underwent sulfate reduction and consume H⁺in water,resulting in the gradual increase of p H value during the experiment.(3)Compared with weed-derived organic matter,the anaerobic decomposition of algae-derived organic matter also had sulfur oxidation process in water column.Sulfate reduction continued to occur in the water column under the decomposition condition of weed-derived organic matter.In the later stage of the experiment,the content of S^2-tended to be stable in the water column,but no obvious sulfur oxidation reaction occurred.In the water column under the decomposition condition of algae-derived organic matter,sulfate reduction reaction continued in the early stage of the experiment,and significant sulfur oxidation reaction took place in the later stage of the experiment,which indicated that sulfate reducing bacteria participated in the reaction process,oxidized S^2-to S,and then to SO₄^2-,which explained the periodic occurrence of black odor in water polluted by cyanobacterial bloom.(4)The results of high-throughput sequencing for microorganisms showed that there were significant differences in microbial community structure under different organic matter sources.The initial lake water was dominated by aerobic microbial community with relatively single structure.The diversity of microbial communities in water column was higher under algae-derived organic matter,including oxidizing microorganisms,such as Chlorobaculum,Thiovirga and Sulfuricurvum as well as reducing microorganisms Desulfotomaculum.The genus Chlorobaculum gradually increased with the experimental process and became the dominant genus in the later stage of the experiment.In the water column under the condition of weed-derived organic matter,sulfur-oxidizing bacteria(SOB)included Chlorobaculum and Chlorobium,sulfate-reducing bacteria(SRB)included Desulfosporosinus,Desulfovibrio,Desulfobacterium and Desulfotomaculum.In the process of experiment,green sulfur bacteria might synergistically coexist with sulfate-reducing bacteria^[1],which was due to the oxidation of HS by green sulfur bacteria to produce S⁰,and then the generated S⁰ was reduced to HS by sulfate-reducing bacteria again,thus becoming the electron donor of green sulfur bacteria again.