填埋场古细菌垂直分布格局及其与垃圾降解程度响应特征

Archaea vertical distribution in landfill and its response characteristics to waste degradation degree

研究了青岛市小涧西垃圾填埋场表层(3~12 m)、中上层(15~24 m)、中下层(27~36 m)和底层(39~45 m)古细菌的多样性、群落组成与垂直分布特征,以及垃圾降解程度与古细菌群落结构演替变化的响应关系.结果表明:垃圾有机质和凯氏氮含量随填埋深度增加呈降低趋势,而pH呈微弱升高趋势.填埋场中下层的古细菌群落多样性和丰度显著高于其他填埋层.在填埋层各深度上,广古菌门(Euryarcharota)为优势菌门,相对丰度达到90%以上,甲烷微菌纲(Methanomicrobia)和热源体纲(Thermoplasmata)为优势菌纲,二者相对丰度之和达84.69%~99.67%.属水平上,甲烷囊菌属(Methanoculleus)的占比在38.16%~64.46%之间变化,且与有机质相关性不显著,表明该类氢营养型产甲烷菌在垃圾中分布广泛,受垃圾降解程度影响较小.马赛球菌属(Methanomassiliicoccus)的相对丰度自表层的50%降至底层的20%,且与有机质呈显著正相关(r=0.95,p<0.05),表明该类甲基营养型产甲烷菌的分布受有机质降解程度影响较大.以乙酸裂解产甲烷的甲烷八叠球菌属(Methanosarcina)和甲烷丝菌属(Methanothrix)在填埋场中也占有重要地位,但二者相对丰度整体低于Methanoculleus.Methanosarcina自表层至底层所占比重逐渐升高,与有机质呈显著负相关(r=-0.96,p<0.05);而Methanothrix仅在中下层有较高的丰度,与有机质相关性不显著,主要与两种菌属对乙酸亲和性的差异有关.不同填埋深度上产甲烷菌群落结构的演替变化反映了不同类型产甲烷菌对垃圾降解产物与稳定化程度的响应.

The diversity, community composition and vertical distribution characteristics of archaea in the surface layer(3~12 m), upper middle layer(15~24 m), lower middle layer(27~36 m), and bottom layer(39~45 m) in Qingdao Xiaojianxi municipal solid waste landfill site were investigated, and the relationships between waste degradation degree and the succession of archaea community structure were also clarified. The results showed that the diversity and abundance of archaea community in the lower middle layer were significantly higher than those in other layers. At each depth of the landfill layer, Euryarcharota was the dominant phylum with a relative abundance of over 90%, and Methanomicrobia and Thermoplasmata were the dominant classes with total relative abundances of 84.69%~99.67%. At the level of genus, Methanoculleus occupied a high proportion in all landfill layers with a varying range of 38.16%~64.46%, and the variation of its proportion was not significantly correlated with the change of organic matters, which indicated that the hydrogen-utilizing methanogen was widely distributed in landfills and was less affected by the degree of waste degradation. The relative abundance of Methanomassiliicoccus decreased from 50% in the surface layer to 20% in the bottom layer, and it was significantly positively correlated with organic matters(r=0.95, p<0.05), which indicated that the distribution of methyl group-utilizing methanogen was greatly affected by the degree of organic matter degradation. Methanosarcina and Methanothrix, which produce methane by catabolizing acetic acid, also played an important role in landfills, but their relative abundances were lower than that of Methanoculleus. The proportion of Methanosarcina increased gradually from the surface layer to the bottom layer, and it was strongly negatively correlated with the change of organic matters(r =-0.96, p<0.05), while Methanothrix occupied a high proportion in the lower middle layers, and it was not significantly correlated with the change of organic matters. The difference was mainly due to the differences in the affinity of acetate between the two genera. The succession of methanogen community structure at landfill depth reflected the response of different types of methanogen to the degradation products and stabilization degree of waste.