珠江河口湿地沉积物中耐盐硝化细菌的筛选及其河口硝化特性研究

摘要

In order to alleviate the nitrogen pollution in estuarine waters, nitrifying bacteria were separated from different sediments of the Pearl River estuary, and acclimated at high salinity medium. And obtained strain with high salt tolerance and high nitrification efficiency was classified through colony morphology observation, physiological characteristics and 16S rDNA sequence analysis. The nitrification efficiencies of this strain cultured at different pH values, temperatures, inoculating rates and sediment qualities were analyzed. Its nitrification property under the environmental condition of estuarine water was also revealed by combining its cells with wetland salt-tolerant plants. The results proved a theoretical basis for alleviate the estuary nitrogen pollution especially by the salt tide intrusion as well as the repair after intrusion. The number of nitrifying bacteria contained in sediments from three typical wetlands, including phragmites wetland, spartina alterniflora wetland and mudflat wetland, were 2.1×105 cells·g-1, 1.8×105 cells·g-1 and 0.5×105 cells·g-1, respectively. The net nitrification rates were (0.41±0.02) mg·m-2·d-1, (0.35±0.03) mg·m-2·d-1 and (0.12±0.02) mg·m-2·d-1, and nitrification intensity were phragmites > spartina alterniflora> mudflat areas. A salt tolerant and high efficient nitrifying bacteria (L4), namely Nitrosomonas communi, was isolated from the sediment of phragmites. When the salinity ranged from 5‰ to 20‰, the nitrification efficiency decreased from 80.5% to 7.7%. After salinity domestication, the nitrification efficiency reached 75.6% at 20‰. The optimal pH value, temperature value and optimal inoculum wet biomass was 7.2 , 30 ℃,and 1g·L-1, respectively, whereas, the sediment was not the vital factor. When the estuary environment was simulated with different salinity and hydrodynamic conditions, strain L4 and phragmites combination system exhibited a stable nitrification efficiency within 0-20‰salinity, the nitrification efficiency in 7 days reached 80.9%-88.91%. It showed a certain degree of synergy when in the salinity of 30‰ and 40‰, the nitrification efficiencies were 52.13% and 31.89%, were all greater than the sum of the nitrification efficiencies of phragmites and strain L4 alone. The nitrification efficiency could reach 67.5% in the absence of hydrodynamics, and reached 81.5% at the ventilation volume rate of 1.5 L·h-1. Oxygen enrichment of hydrodynamic effects could promote nitrification. Strain L4 and phragmites showed a synergistic effect in nitrogen pollution remediation of estuary wetland.%为缓解河口水域氮污染,对珠江河口不同湿地类型沉积物中的硝化细菌进行分离和盐度驯化,筛选出耐盐且硝化效率较高的菌株,通过菌株形态、生理生化和16Sr DNA基因分析对其进行鉴定,分别测定菌株在不同温度、pH、接种量和不同沉积物质量下的硝化效率.将硝化细菌与湿地耐盐植物芦苇(Phragmites australis)组合,研究硝化细菌、芦苇及两者组合系统在河口不同盐分和水动力条件下的硝化特性,以期为河口水域咸潮入侵时和入侵后氮污染的修复奠定基础.结果表明,3种典型湿地芦苇、互花米草(Spartina alterniflora)和光滩沉积物中硝化细菌的数量分别为2.1×105、1.8×105和0.5×105 cells·g-1,净硝化速率分别为(0.41±0.02)、(0.35±0.03)、(0.12±0.02)mg·m-2·d-1,硝化作用强度:芦苇区>互花米草区>光滩区.从芦苇湿地沉积物中筛选出1株高效硝化细菌L4,经鉴定,为亚硝化单胞菌属(Nitrosomonas communi).菌株L4在盐度从5‰上升至20‰时,硝化效率从80.5%下降至7.7%.经盐度驯化,菌株L4在20‰以内的盐度环境下硝化效率可达到75.6%,其最适pH和温度分别为7.2和30℃,最适接种量为1 g·L-1湿菌,沉积物对菌株L4硝化作用影响不大.模拟不同盐分和水动力条件的河口环境,菌株L4-芦苇组合系统在0‰~20‰的盐度环境下均表现出稳定的硝化效率,7 d硝化效率达到80.9%~88.91%;在盐度分别为30‰和40‰时,硝化效率分别为52.13%和31.89%,均大于芦苇和菌株L4单独系统的硝化效率之和,表现出一定的协同性.菌株L4-芦苇组合系统在未曝气时硝化效率可达到67.5%,在1.5 L·h-1的曝气量时硝化效率最高达到81.5%,可见水动力的富氧作用可促进硝化作用的进行.菌株L4和芦苇的协同作用在河口氮污染修复中具有良好的应用潜力.