Effects of bulking agent addition on odorous compounds emissions during composting of OFMSW

The effects of rice straw addition level on odorous compounds emissions in a pilot-scale organic fraction of municipal solid waste (OFMSW) composting plant were investigated. The cumulative odorous compounds emissions occurred in a descending order of 40.22, 28.71 and 27.83 mg/dry kg of OFMSW for piles with rice straw addition level at ratio of 1:10, 2:10 and 3:10 (mixing ratio of rice straw to OFMSW on a wet basis), respectively. The mixing ratio of rice straw to OFMSW had a statistically significant effect on the reduction of malodorous sulfur compounds emissions, which had no statistically significant effect on the reduction of VFAs, alcohols, aldehydes, ketones, aromatics and ammonia emissions during composting, respectively. The cumulative emissions of malodorous sulfur compounds from piles with the increasing rice straw addition level were 1.17, 1.08 and 0.88 mg/dry kg of OFMSW, respectively. The optimal mixing ratio of rice straw to OFMSW was 1:5. Using this addition level, the cumulative malodorous sulfur compounds emissions based on the organic matter degradation were the lowest during composting of OFMSW.     

Effect of wheat and rice straw biochars on pyrazosulfuron-ethyl sorption and persistence in a sandy loam soil

The objective of this research was to investigate the effect of wheat and rice biochars on pyrazosulfuron-ethyl sorption in a sandy loam soil. Pyrazosulfuron-ethyl was poorly sorbed in the soil (3.5–8.6%) but biochar amendment increased the herbicide adsorption, and the effect varied with the nature of the feedstock and pyrolysis temperature. Biochars prepared at 600°C were more effective in adsorbing pyrazosulfuron-ethyl than biochars prepared at 400°C. Rice biochars were better than wheat biochars, and higher herbicide adsorption was attributed to the biochar surface area/porosity. The Freundlich constant 1/n suggested nonlinear isotherms, and nonlinearlity increased with increase in the level of biochar amendment. Desorption results suggested sorption of pyrazosulfuron-ethyl was partially irreversible, and the irreversibility increased with increase in the level of biochar. Both sorption and desorption of pyrazosulfuron-ethyl correlated well with the content of biochars. The free energy change (ΔG) indicated that the pyrazosulfuron-ethyl sorption process was exothermic, spontaneous and physical in nature. Persistence studies indicated that biochar (0.5%) amendment did not have significant effect on herbicide degradation, and its half-life values in the control, 0.5% WBC600- and RBC600-amended rice planted soils were 7, 8.6, and 10.4 days, respectively.     

Effects of soil attributes and straw accumulation on the sorption of hexazinone and tebuthiuron in tropical soils cultivated with sugarcane

Brazil is the largest sugarcane producer in the world in which hexazinone (3-cyclohexyl-6-dimethylamino-1-methyl-1,3,5-triazine-2,4-dione) and tebuthiuron (1-(5-tert-butyl-1,3,4-thiadiazol-2-yl)-1,3-dimethylurea) are heavily used. Sugarcane harvesting is changing from the manual system with previous straw burning to the mechanized system without straw burning. The lack of burning results in soil organic carbon accumulation mainly in clayey soils, which should affect herbicides availability and fate. Therefore, we evaluated sorption of these herbicides in soil samples with and without straw burning. Both herbicides presented low apparent sorption coefficients (mean K_d,app= 0.6 and 2.4 L kg^?1 for hexazinone and tebuthiuron, respectively), suggesting that they may leach to groundwater. Moreover, their sorption correlated primarily with soil organic carbon (SOC), but iron oxide contents extracted with ammonium oxalate (Fe₂O₃^AOX) also affected it (K_d,app = ?0.228 + 0.0397 SOC + 0.117 Fe₂O₃^AOX for hexazinone and K_d,app = ?1.407 + 0.201 SOC + 0.348 Fe₂O₃^AOX for tebuthiuron). Soil organic carbon accumulation due to straw maintenance in the field positively affected sorption of both herbicides, but its effects were not enough to classify them as “non-leachers.”     

Use of fungi for the bioconversion of rice straw into cellulase enzyme

Cellulase production was carried out by solid state bioconversion (SSB) method using rice straw, a lignocellulosic material and agricultural waste, as the substrate of three Trichoderma spp. and Phanerochaete chrysosporium in lab-scale experiments. The results were compared to select the best fungi among them for the production of cellulase. Phanerochaete chrysosporium was found to be the best among these species of fungi, which produced the highest cellulase enzyme of 1.43 IU/mL of filter paper activity (FPase) and 2.40 IU/mL of carboxymethylcellulose activity (CMCase). The “glucosamine” and “reducing sugar” parameters were observed to evaluate the growth and substrate utilization in the experiments. In the case of Phanerochaete Chrysosporium, the highest glucosamine concentration was 1.60 g/L and a high concentration of the release of reducing sugar was measured as 2.58 g/L obtained on the 4th day of fermentation. The pH values were also recorded. The range of the pH was about 5.15 to 5.56 in the case of Phanerochaete Chrysosporium.     

混合水解对打捆麦秸水解产酸的影响

为研究混合水解对麦秸水解产酸的影响,以猪粪、厨余和蔬菜废物为原料,研究其分别与麦秸混合水解产酸的特性,分析了水解过程中pH值、COD、SCOD和VFAs的变化。结果表明,除麦秸＋蔬菜废物最佳出料时间为3～9d外,麦秸、麦秸＋厨余垃圾、麦秸＋猪粪水解液最佳出料时间均为3～7d,7d后水解液COD浓度下降;将蔬菜废物与麦秸混合水解,水解液pH值降低幅度最大,水解液中总有机酸浓度最高,pH值最低为5．31,有机酸浓度最高达6．46g／L,且水解液中SCOD浓度、SCOD／COD比值最大;添加猪粪明显促进了麦秸有机物的水解溶出,麦秸单位干物质水解率和产酸率较对照分别提高了43％～134％和50．53％,但对提高水解液SCOD浓度、SCOD／COD比、TVFA浓度、降低水解液pH值的效果不如蔬菜废物;添加厨余垃圾的效果介于猪粪和蔬菜废物之间。从促进麦秸水解产酸的角度,以添加猪粪的效果最好。     

几种污水处理材料对COD和Cr(Ⅵ)的去除比较研究

研究了活性炭、硅藻土、高岭土和改性玉米秸秆几种常见污水处理材料对污水中有机物(COD)和Cr(Ⅵ)的吸附效果,发现活性炭吸附污水中有机物的效果最好,经活性炭吸附的污水的COD去除率达88.8%。同时,活性炭对Cr(Ⅵ)也有很强的吸附能力。硅藻土和高岭土对有机物的吸附效果较差,对Cr(Ⅵ)具有较好的吸附效果。改性玉米秸秆对Cr(Ⅵ)表现出很强的吸附能力,在低浓度Cr(Ⅵ)的吸附实验中,可以达到比活性炭更高的吸附量,开发应用潜力巨大。     

秸秆还田少免耕对冲积土微生物多样性及微生物碳氮的影响

土壤微生物是耕地质量的重要指标,为阐明秸秆还田少免耕对土壤质量的影响及其机理,在成都平原(温江)冲积水稻土区,开展了水稻–小麦/油菜轮作秸秆还田培肥定位试验(2003～2008年),在小麦生长季节,系统研究了土壤耕层微生物数量和微生物生物量的变化特征.结果表明,秸秆还田翻耕与秸秆还田免耕的土壤耕层微生物总量分别增加了51.7%、12.8%,土壤微生物数量增加主要来自土壤细菌数量的增加;从小麦全生育期看,在小麦分蘖期的增加幅度高于小麦播种期和小麦收获后,有利于促进小麦养分吸收与生长发育.秸秆还田少免耕显著增加了微生物生物量,秸秆还田翻耕和秸秆还田免耕处理土壤微生物碳总量分别比对照提高74.1%、25.8%,土壤微生物氮分别提高60.2%和12.1%.秸秆还田循环利用显著增加了土壤微生物数量和生物量,有利于土壤养分循环与转化,有利于提高土壤有机质含量并改善有机质质量,是耕地质量建设的重要途径.     

Online single particle analysis of chemical composition and mixing state of crop straw burning particles: from laboratory study to field measurement

Fresh straw burning (SB) particles were generated in the laboratory by the combustion of rice straw and corn straw. The chemical composition and mixing state of the fresh SB particles were investigated by an Aerosol Time-of-Flight Mass Spectrometer (ATOFMS). Based on the mass spectral patterns, the SB particles were clustered into four major types: Salt, Organic Carbon (OC), Elemental Carbon (EC), and internally mixed particles of EC and OC (EC-OC). In addition, particles containing ash, polycyclic aromatic hydrocarbons, heavy metals or nicotine were also observed. Physical and chemical changes of the SB particles immediately after the emission were analyzed with highly time-resolved data. During the aging processes, the average particle size increased steadily. Freshly emitted organic compounds were gradually oxidized to more oxygenated compounds in the OC-containing particles. Meanwhile, an important displacement reaction (2KCl+ SO42−→ K₂SO₄ + 2Cl⁻) was observed. The marker ions for SB particles were optimized and applied to identify the SB particles in the ambient atmosphere. The fluctuation of the number fraction of ambient SB particles sorted by ATOFMS agrees well with that of water soluble K⁺ measured by an online ion chromatography, demonstrating that the optimized marker ions could be good tracers for SB particles in field measurements.     

麦秸与奶牛场废水高固体混合厌氧发酵产甲烷研究

在实验室条件下,以麦秸和奶牛场废水为原料,设计麦秸与奶牛场废水质量比1∶4(T1)、1∶3(T2)和1∶2(T3)以及对照(麦秸与水质量比1∶4(T4))4个处理,研究发酵过程中日产气量、甲烷含量、发酵前后麦秸理化特性和结构的变化.结果表明,奶牛场废水与麦秸在中温、高固体条件下,厌氧发酵可以正常进行,且产气期延长2周以上,对甲烷含量的影响不大;厌氧发酵初始TS浓度对系统产气的影响较大,麦秸产气量随TS浓度的增加而降低,以T1的产气效果最好,麦秸TS产气量为0.41 L.g-1,较T4提高了17.14%,平均甲烷含量为48.78%;厌氧发酵后,麦秸半纤维素含量大幅降低,纤维素含量少许降低,降低幅度均为T1>T2>T4>T3,木质素含量稍有增加,各处理间无显著差异(P>0.05);FTIR和XRD的结果表明,厌氧发酵后,麦秸纤维素结晶区的相对含量增加,混合发酵可以促进厌氧微生物对麦秸纤维素结晶区的破坏.将麦秸与奶牛场废水(质量比)1∶4混合发酵产沼气是可行的,且促进了厌氧微生物对麦秸有机物的分解破坏,提高了麦秸产气量.     

施肥及秸秆还田处理下玉米季温室气体的排放

以华北地区冬小麦-夏玉米轮作农田为研究对象,在玉米整个生长季,运用静态箱法针对正常施肥及正常施肥结合秸秆还田处理进行了为期3年N2O排放通量的连续观测,并开展了1季CO2和CH4交换通量的研究.在玉米整个生长过程中施肥阶段N2O的排放量占到了总排放量的83%—96%,表明现有化肥的使用明显导致了农田N2O排放增加.与控制地相比,施肥和耕种可导致玉米田CO2排放明显增加,且正常施肥及秸秆还田样地CO2排放主要集中在苗期至吐丝期.控制地、正常施肥样地及施肥结合秸秆还田样地CH4的累积排放量均为负值,说明旱地土壤是CH4的一个汇.秸秆还田在一定程度上增加了玉米季N2O和CO2的排放量,但对CH4的吸收有所抑制.正常施肥样地和秸秆还田样地全球净增温潜势分别为-1392.8 kg C.hm-2和-179.2 kg C.hm-2,表明华北农田在现有耕作方式下是大气温室气体的一种重要汇.