臭氧/紫外联合降解甲醛的试验研究

在臭氧单独作用、紫外光单独作用和UV/O₃ 3种条件下分别对甲醛进行降解试验,研究表明,臭氧和紫外在降解甲醛的试验中存在明显的协同促进作用。单独臭氧对甲醛降解效果并不显著。紫外单独作用时,对甲醛几乎没有降解作用。在UV/O₃条件下,甲醛的降解率大大提高,特别是在高浓度臭氧条件下,降解率高达63％。臭氧浓度增大,降解率增大;紫外光强度增大,降解效果提高;气体流量增大,降解率下降;湿度增大,降解率提高。对甲醛降解试验进行动力学研究,结果表明,光照强度和臭氧浓度增大,一级反应速率增大,提高臭氧浓度要比加强紫外强度更能促进甲醛的降解。     

臭氧氧化预处理难降解农药废水的研究

采用臭氧氧化技术预处理脲类农药生产废水,调节废水pH至弱碱,在此基础上考察废水臭氧氧化预处理的影响因素,得出最佳预处理条件：COD为200 mg/L,初始pH为11.3,臭氧投加量为14.2 mg/L。连续预处理180 min后,可生化性从0.12提高到0.58,说明该项技术可大大提高脲类农药废水的可生化性。     

Emissions of liquefied petroleum gas (LPG) from motor vehicles

Continuous on-site measurements of 50 speciated volatile organic compounds (VOCs) were conducted in downtown Guangzhou to characterize the sources and concentration profiles of ambient VOCs. The synchronicity in diurnal variation between the VOCs and NO suggests that traffic emissions were responsible for the observed VOCs in downtown Guangzhou.It was found that the three major constituent species of liquefied petroleum gas (LPG), i.e., propane, iso-butane, and n-butane, together termed LPG alkanes, contributed, on average, 24% of the total VOCs (TVOCs). Their high correlation and synchronized diurnal variations between NO and the LPG alkanes suggest that their origin lies in LPG fueled car exhaust in Guangzhou. LPG buses and taxis were likely to be responsible for the bulk of ambient LPG species. Using propane and 3-methyl pentane (3MC5A) as the indicators for the LPG and gasoline emissions, respectively, the emissions of the LPG fleet were found to increase more than those of the gasoline fleet during the morning and evening rush hours, as well the noontime break in downtown Guangzhou.Although LPG alkanes account for 24% of the TVOC, their contribution to the total ozone forming potential (OFP) is only about 7%. Ethylene and propylene contribute about 26% to the total OFP despite their lower contribution of 16% to the TVOC.     

N2O emissions at municipal solid waste landfill sites: Effects of CH4 emissions and cover soil

Municipal solid waste landfills are the significant anthropogenic sources of N₂O due to the cooxidation of ammonia by methane-oxidizing bacteria in cover soils. Such bacteria could be developed through CH₄ fumigation, as evidenced by both laboratory incubation and field measurement. During a 10-day incubation with leachate addition, the average N₂O fluxes in the soil samples, collected from the three selected landfill covers, were multiplied by 1.75 (p < 0.01), 3.56 (p < 0.01), and 2.12 (p < 0.01) from the soil samples preincubated with 5% CH₄ for three months when compared with the control, respectively. Among the three selected landfill sites, N₂O fluxes in two landfill sites were significantly correlated with the variations of the CH₄ emissions without landfill gas recovery (p < 0.001). N₂O fluxes were also elevated by the increase of the CH₄ emissions with landfill gas recovery in another landfill site (p > 0.05). The annual average N₂O flux was 176 ± 566 μg N₂O–N m^?2 h^?1 (p < 0.01) from sandy soil–covered landfill site, which was 72% (p < 0.05) and 173% (p < 0.01) lower than the other two clay soil covered landfill sites, respectively. The magnitude order of N₂O emissions in three landfill sites was also coincident by the results of laboratory incubation, suggesting the sandy soil cover could mitigate landfill N₂O emissions.     

Minimisation of N2O emissions from a plant-soil system under landfill leachate irrigation

The irrigation of a plant-soil system with landfill leachate should promote the formation of N2O due to the introduction of organic carbon and mineralized-N and the elevation of the moisture content. Laboratory incubation was performed to minimize N2O emissions from a leachate irrigated plant-soil system by manipulating leachate NH(4)(+)-N loading, moisture content, and soil type. A field investigation, consisting of three plots planted with Cynodon dactylon, Nerium indicum Mill, and Festuca arundinacea Schreb, was then conducted to select plant species. There was almost no difference in N2O emissions between soil moisture contents of 46% and 55% water-filled pore space (WFPS), while a sharp increase occurred at 70% WFPS. N2O fluxes were significantly correlated with leachate NH4(+)-N loading. Amongst the physiochemical characteristics of the selected nine soils, only soil pH was significantly correlated with N2O fluxes. Compared with fertilizers application in other ecosystems, N2O turnover rate from the plant-soil system under leachate irrigation was relatively lower. Therefore, avoiding high NH4(+)-N loadings and excessively wet conditions (<60% WFPS) and cultivating conifer plants of stronger sunlight penetration with less litter deposit on acidic sandy soil could minimize potential N2O emissions under leachate irrigation.     

Sorting efficiency and combustion properties of municipal solid waste during bio-drying

One aerobic and two combined bio-drying processes were set up to investigate the quantitative relationships of sorting efficiency and combustion properties with organics degradation and water removal during bio-drying. Results showed that the bio-drying could enhance the sorting efficiency of municipal solid waste (MSW) up to 71% from the initial of 34%. The sorting efficiency was correlated with water content negatively (correlation coefficient, r = −0.89) and organics degradation rate positively (r = 0.92). The higher heating values (HHVs) were correlated with organics degradation negatively for FP (i.e. the sum of only food and paper) (r = −0.93) but positively for the mixing waste (MW) (r = 0.90), whereas the lower heating values (LHVs) were negatively correlated with water content for both FP (r = −0.71) and MW (r = −0.96). Other combustion properties depended on organics degradation performance, except for ignition performance and combustion rate. The LHVs could be greatly enhanced by the combined process with insufficient aeration during the hydrolytic stage. Compared with FP, MW had higher LHVs and ratios of volatile matter to fixed carbon. Nevertheless, FP had higher final burnout values than MW.     

Dissolved organic matter and estrogenic potential of landfill leachate

The estrogenic potentials of leachate samples collected at Laogang Sanitary Landfill in Shanghai, China were measured together with the associated dissolved organic matter (DOM) in leachate samples. Over 99% of the DOM in fresh leachate was removed upon 3-7 years of landfill, leaving only DOM with strong fluorescent activity. Anoxic or aerobic treatment of landfill leachate can further degrade DOM of MW<300 Da and transform those with fluorescent activity of MW>10(5) Da to those of 2000-10(5) Da. Neither landfilling nor storage in anoxic pond effectively removed estrogenic potential of leachate. Fractionation test revealed that residual organic matters of MW 3000-14000 Da and of <600 Da with high UV254 contributed most of the estrogenic activities in leachate. Aerobic SBR treatment considerably reduced the estrogenic potential of these organic matters in leachate.     

N2O emissions from municipal solid waste landfills with selected infertile cover soils and leachate subsurface irrigation

This study presents the field investigations into the effects of cover soils and leachate subsurface irrigation on N₂O emissions from municipal solid waste landfills. Landfill Site A and Site B, covered with carefully chosen infertile soils, were selected to monitor their diurnal and seasonal variations of N₂O emissions. The annual average N₂O flux was 469 ± 796 μg N₂O-N m⁻² h⁻¹ in Site B with leachate subsurface irrigation, three times that of Site A without leachate irrigation. When an additional soil containing lower contents of carbon and nitrogen was introduced to cover part of Site B, its N₂O fluxes decreased by 1-2 orders of magnitude compared with the left area of Site B. This suggested that carefully selected cover soils could substantially reduce N₂O emissions even under leachate subsurface irrigation. Statistical analysis proved that the availabilities of soil moisture and mineralized nitrogen were the key parameters controlling landfill N₂O emissions.     

烟气脱硝低温选择性催化还原金属氧化物催化剂的研究进展

低温选择性催化还原(SCR)技术具有很高的脱硝效率。概述了低温SCR金属氧化物催化剂的制备方法和性能,分析了催化剂的失活原因和再生方法,探讨了催化反应的机理,并介绍了低温SCR技术在工业烟气脱硝中的应用案例。SCR催化剂未来的发展不仅要以低温下的高活性和高选择性为主要目的,还要考虑到催化剂的抗失活性能(如抗硫性和抗水稳定性)和操作温度范围,使其可广泛应用于不同的工况中,以满足我国日益提高的环保要求。     

论油气管道工程施工期环境监理工作

应用建设项目工程监理的基本原理和方法,针对油气管道工程施工特点,对油气管道工程施工环境监理的目的、任务和特点进行了探讨,提出了施工环境监理的主要依据和原则,分析了施工不同阶段的工作内容和方法,介绍了监理工作程序和制度,最后提出对开展油气管道环境监理工作的建议。