Dynamic of functional microbial groups during mesophilic composting of agro-industrial wastes and free-living (N2)-fixing bacteria application

Although several reports are available concerning the composition and dynamics of the microflora during the composting of municipal solid wastes, little is known about the microbial diversity during the composting of agro-industrial refuse. For this reason, the first parts of this study included the quantification of microbial generic groups and of the main functional groups of C and N cycle during composting of agro-industrial refuse. After a generalized decrease observed during the initial phases, a new bacterial growth was observed in the final phase of the process. Ammonifiers and (N₂)-fixing aerobic groups predominated outside of the piles whereas, nitrate-reducing group increased inside the piles during the first 23 days of composting. Ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), showed an opposite trend of growth since ammonia oxidation decreased with the increase of the nitrite oxidation activity. Pectinolytics, amylolytics and aerobic cellulolytic were present in greater quantities and showed an upward trend in both the internal and external part of the heaps.Several free-living (N₂)-fixing bacteria were molecularly identify as belonging especially to uncommon genera of nitrogen-fixing bacteria as Stenotrophomonas, Xanthomonas, Pseudomonas, Klebsiella, Alcaligenes, Achromobacter and Caulobacter. They were investigated for their ability to fix atmospheric nitrogen to employ as improvers of quality of compost. Some strains of Azotobacter chrococcum and Azotobacter salinestris were also tested. When different diazotrophic bacterial species were added in compost, the increase of total N ranged from 16% to 27% depending on the selected microbial strain being used. Such microorganisms may be used alone or in mixtures to provide an allocation of plant growth promoting rhizobacteria in soil.     

Elevated CO2 facilitates C and N accumulation in a rice paddy ecosystem

Elevated CO2 can stimulate wetland carbon(C) and nitrogen(N) exports through gaseous and dissolved pathways, however, the consequent influences on the C and N pools are still not fully known. Therefore, we set up a free-air CO2 enrichment experiment in a paddy field in Eastern China. After five year fumigation, we studied C and N in the plant–water–soil system. The results showed:(1) elevated CO2 stimulated rice aboveground biomass and N accumulations by 19.1% and 12.5%, respectively.(2) Elevated CO2 significantly increased paddy soil TOC and TN contents by 12.5% and 15.5%, respectively in the 0–15 cm layer, and22.7% and 26.0% in the 15–30 cm soil layer.(3) Averaged across the rice growing period,elevated CO2 greatly increased TOC and TN contents in the surface water by 7.6% and 11.4%,respectively.(4) The TOC/TN ratio and natural δ15N value in the surface soil showed a decreasing trend under elevated CO2. The above results indicate that elevated CO2 can benefit C and N accumulation in paddy fields. Given the similarity between the paddies and natural wetlands, our results also suggest a great potential for long-term C and N accumulation in natural wetlands under future climate patterns.     

序批式动态膜生物反应器处理低碳氮比废水的试验研究

以序批式动态膜反应器为研究对象,对其处理低碳氮比废水的效果进行了试验研究.试验温度为19 ～ 21℃,MLSS为3～5g/L;好氧阶段溶解氧质量浓度为2 ～4 mg/L,厌氧阶段溶解氧质量浓度为0.2～0.5 mg/L;水力停留时间共12 h,其中好氧阶段8h,厌氧阶段4h.结果表明:当进水COD、TN和NH4+-N质量浓度分别为250～300mg/L、103 ～ 156 mg/L和92～140 mg/L时,反应器对上述污染物表现出较高且稳定的去除效率,COD、TN和NH4+-N平均去除率分别达到76.15％、82.16％和90.13％.同时,反应器系统中污泥的比硝化速率与常规处理装置中的活性污泥相比较高,以NH4+-N的降解量计为0.101 d-1,以NO3--N的积累量计为0.091 d-.     

三江平原泥炭沼泽孔隙水甲烷浓度变化动态及其影响因子

湿地土壤孔隙水甲烷浓度变化动态对于揭示湿地碳循环过程具有重要作用.于2012年和2013年对三江平原毛苔草泥炭沼泽不同土壤深度孔隙水甲烷浓度的季节变化动态进行监测,并分析了其关键影响因子.结果表明:植物生长季孔隙水甲烷浓度呈单峰变化趋势,不同土层甲烷浓度峰值(80.45~490.95μmol·L-1)主要集中在湿润的生长季末,但年际间存在显著差异;从土壤剖面来看,土壤融通之后,孔隙水中甲烷浓度随着土壤深度的增加而增加;土壤表层(5 cm和10 cm)甲烷浓度主要受到株高(R2=0.6,p=0.005)和土壤充水孔隙率(R2=0.36,p=0.01)的影响,而深层(20~40 cm)甲烷浓度主要受到土壤温度等因素的综合影响.研究还表明,表层土壤孔隙水甲烷浓度能够解释生长季甲烷排放通量变化的26%~60%,而且短期的极端降雨事件可能不会对甲烷浓度以及甲烷排放产生即时影响,而是出现大约一周的延迟(time lag)现象,这主要取决于实际土壤湿度.     

小麦-玉米轮作体系农田氮素淋失特征及氮素表观平衡

连续6年采用渗漏计法研究了不同施氮处理下陕西关中小麦-玉米轮作区农田土壤90 cm深度处氮素(N)淋失特征和土壤-作物体系氮素表观平衡状况.结果表明:该地区农田氮素淋溶主要发生在降雨量较多的玉米季,且集中在8月和9月.监测期内,TN和NO-3-N年平均流失量分别为2.72~23.07 kg·hm-2和1.53~18.72 kg·hm-2,年流失率分别为0.65%~3.44%和0.82%~3.32%,且年总氮、硝态氮流失量均随年施氮量增加呈指数增加.氮素淋失形态中,NO-3-N比例较高,可占总氮淋失量的56.00%~81.00%,且随着氮肥用量的降低,其占总氮淋失量的比例也随之减小.可见,施氮量的大小在一定程度上会影响淋失液中各形态氮的比例.氮素表观平衡结果显示,随着施氮量提高,氮素在土壤中的残留和表观氮盈余均呈现指数增加趋势.长期施氮条件下,土壤-作物体系氮素表观损失率的幅度为32.60%~55.20%,土壤表观残留率为-0.17%~8.20%.多年监测结果表明,优化施氮模式下,作物不仅可以获得较高的产量和氮肥利用率,农田氮素淋失量也大幅降低,在节约肥料资源的同时减轻了潜在的环境风险.     

甲烷氧化菌在填埋场覆盖层中的工程应用(Ⅱ):基质选择性及长效性

针对已筛选获得的甲烷氧化混合菌,选取填埋场覆盖土(LCS)、矿化垃圾(AR)和塘渣(TZ)3种填埋场周边易得的材料为供试生存基质,从基质选择性及长效性角度进行了甲烷减排应用条件的探究及使用效能评估.结果表明,在TZ、LCS、AR、TZ-AR和LCS-AR这5种生存基质中,TZ-AR最适合甲烷氧化混合菌的生长,且TZ与AR的复配比例以5∶5为最佳.甲烷氧化混合菌在TZ-AR的粒径≤4 mm和含水率为20%时具有最高甲烷氧化能力.一次性接种甲烷氧化混合菌在静态体系中的最佳使用有效期为31 d.其在接种量为0.08、0.16、0.20 m L·g-1和0.25m L·g-1时甲烷氧化速率无明显差异,从工程应用角度而言,8%的接种量为最佳.     

三相生物流化床处理低C/N污水的亚硝化过程控制研究

将短程硝化与生物流化床相结合,采用低碳氮比的人工合成污水进行启动,考察进水COD、氨氮、DO、p H对硝化和亚硝化过程的影响。研究表明,较短的水力停留时间(HRT)和较少的接种污泥量有利于生物膜的生长,能够成功实现生物流化床的快速启动。高进水氨氮浓度有助于反应器实现亚硝酸盐的积累,但是这种积累并不稳定。当反应器中p H为7.5~8.1,ρ(DO)为1.5~2.5 mg/L时,最大亚硝化率达到75%左右,氨氮去除率达85%以上。出水NO-2-N和NO-3-N浓度随进水COD浓度的增加而减少;当进水COD浓度为50 mg/L时,出水硝酸盐浓度急剧减少,亚硝酸盐浓度有所降低,反应器发生同步硝化反硝化脱氮现象。     

Enhanced bio-decolorization of 1-amino-4-bromoanthraquinone-2-sulfonic acid by Sphingomonas xenophaga with nutrient amendment

Bacterial decolorization of anthraquinone dye intermediates is a slow process under aerobic conditions. To speed up the process, in the present study, effects of various nutrients on 1-amino-4-bromoanthraquinone-2-sulfonic acid (ABAS) decolorization by Sphingomonas xenophaga QYY were investigated. The results showed that peptone, yeast extract and casamino acid amendments promoted ABAS bio-decolorization. In particular, the addition of peptone and casamino acids could improve the decolorization activity of strain QYY. Further experiments showed that L-proline had a more significant accelerating effect on ABAS decolorization compared with other amino acids. L-Proline not only supported cell growth, but also significantly increased the decolorization activity of strain QYY. Membrane proteins of strain QYY exhibited ABAS decolorization activities in the presence of L-proline or reduced nicotinamide adenine dinucleotide, while this behavior was not observed in the presence of other amino acids. Moreover, the positive correlation between L-proline concentration and the decolorization activity of membrane proteins was observed, indicating that L-proline plays an important role in ABAS decolorization. The above findings provide us not only a novel insight into bacterial ABAS decolorization, but also an L-proline-supplemented bioaugmentation strategy for enhancing ABAS bio-decolorization.     

Synthesis, crystal structure, photodegradation kinetics and photocatalytic activity of novel photocatalyst ZnBiYO4

ZnBiYO₄ was synthesized by a solid-state reaction method for the first time. The structural and photocatalytic properties of ZnBiYO₄ were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and UV-Vis diffuse reflectance. ZnBiYO₄ crystallized with a tetragonal spinel structure with space group I41/A. The lattice parameters for ZnBiYO₄ were a = b = 11.176479 Å and c= 10.014323 Å. The band gap of ZnBiYO₄ was estimated to be 1.58 eV. The photocatalytic activity of ZnBiYO₄ was assessed by photodegradation of methyl orange under visible light irradiation. The results showed that ZnBiYO₄ had higher catalytic activity compared with N-doped TiO₂ under the same experimental conditions using visible light irradiation. The photocatalytic degradation of methyl orange with ZnBiYO₄ or N-doped TiO₂ as catalyst followed first-order reaction kinetics, and the first-order rate constant was 0.01575 and 0.00416 min^-1 for ZnBiYO₄ and N-doped TiO₂, respectively. After visible light irradiation for 220 min with ZnBiYO₄ as catalyst, complete removal and mineralization of methyl orange were observed. The reduction of total organic carbon, formation of inorganic products, SO₄^2- and NO₃^-, and evolution of CO₂ revealed the continuous mineralization of methyl orange during the photocatalytic process. The intermediate products were identified using liquid chromatography- mass spectrometry. The ZnBiYO₄/(visible light) photocatalysis system was found to be suitable for textile industry wastewater treatment and could be used to solve other environmental chemical pollution problems.     

Diurnal and spatial variations of soil NOx fluxes in the northern steppe of China

NO_x emissions from biogenic sources in soils play a significant role in the gaseous loss of soil nitrogen and consequent changes in tropospheric chemistry. In order to investigate the characteristics of NO_x fluxes and factors influencing these fluxes in degraded sandy grasslands in northern China, diurnal and spatial variations of NO_x fluxes were measured in situ. A dynamic flux chamber method was used at eight sites with various vegetation coverages and soil types in the northern steppe of China in the summer season of 2010. Fluxes of NO_x from soils with plant covers were generally higher than those in the corresponding bare vegetation-free soils, indicating that the canopy plays an important role in the exchange of NO_x between soil and air. The fluxes of NO_x increased in the daytime, and decreased during the nighttime, with peak emissions occurring between 12:00 and 14:00. The results of multiple linear regression analysis indicated that the diurnal variation of NO_x fluxes was positively correlated with soil temperature (P < 0.05) and negatively with soil moisture content (P < 0.05). Based on measurement over a season, the overall variation in NO_x flux was lower than that of soil nitrogen contents, suggesting that the gaseous loss of N fromthe grasslands of northern China was not a significant contributor to the high C/N in the northern steppe of China. The concentration of NO_x emitted from soils in the region did not exceed the 1-hr National Ambient Air Quality Standard (0.25 mg/m³).