Experimental and modeling study of the effect of CH(4) and pulverized coal on selective non-catalytic reduction process

The reduction of nitric oxide using ammonia combined with methane and pulverized coal additives has been studied in a drop tube furnace reactor. Simulated flue gas with 1000ppm NO(x) and 3.4% excess oxygen was generated by cylinder gas. Experiments were performed in the temperature range of 700-1200 degrees C to investigate the effects of additives on the DeNO(x) performance. Subsequently, a kinetic mechanism was modified and validated based on experimental results, and a computational kinetic modeling with CHEMKIN was conducted to analyze the secondary pollutants. For both methane and pulverized coal additives, the temperature window is shifted towards lower temperatures. The appropriate reaction temperature is shifted to about 900 and 800 degrees C, respectively with 1000ppm methane and 0.051gmin(-1) pulverized lignite coal. The addition of methane and pulverized coal widens the temperature window towards lower temperature suggesting a low temperature application of the process. Furthermore, selective non-catalytic reduction (SNCR) reaction rate is accelerated evidently with additives and the residence time to complete the reaction is shortened distinctly. NO(x) reduction efficiency with 80% is achieved in about 0.3s without additive at 1000 degrees C. However, it is achieved in only about 0.2s with 100ppm methane as additive, and only 0.07 and 0.05s are needed respectively for the cases of 500 and 1000ppm methane. The modified kinetic modeling agrees well with the experimental results and reveals additional information about the process. Investigation on the byproducts where NO(2) and N(2)O were analyzed by modeling and the others were investigated by experimental means indicates that emissions would not increase with methane and pulverized coal additions in SNCR process and the efficacious temperature range of SNCR reaction is widened approximately with 100 degrees C.     

Population development of the invader ctenophore Mnemiopsis leidyi, in the Black Sea and in other seas of the Mediterranean basin

In the last two decades of the twentieth century, the ctenophore Mnemiopsis leidyi (A. Agassiz) has invaded the Black, Azov, Marmara and Aegean Seas, and, recently, the Caspian Sea. Here, we compare its spatial and temporal distribution, seasonal dynamics and the time and duration of reproduction. We also discuss factors that control its abundance throughout its invasive range and its effect on ecosystems. Observations are based on the long-term field data collected by three research institutes. An analysis of the effects of temperature, salinity, prey (zoo- and ichthyoplankton) availability and predation (by ctenophores of the genus Beroe) on M. leidyi population size, and the effects of M. leidyi on zoo- and ichthyoplankton, and on fish populations in the Black and Azov Seas is also provided. With the Black Sea current, M. leidyi spreads to the upper layers of the Sea of Marmara, where it now occurs around the year. At regular intervals, the Black Sea current also takes it to the northern Aegean Sea. In contrast, it has to re-invade the Sea of Azov every spring or summer, dying out during winter when the temperature drops below 4°C. The warm summer and mild winter temperatures, relatively low salinity and abundance of prey in the Black Sea are close to optimal for M. leidyi, while they are suboptimal in the northern Aegean Sea, where salinity and temperature are often too high. In the Black Sea the absence of gelatinous and other predators led to an enormous ctenophore abundance for a decade, but with the appearance of Beroe ovata in 1999, M. leidyi abundance greatly decreased. Analysis of seasonal dynamics of M. leidyi in the Black Sea and in other seas of the Mediterranean basin indicates similarities in the timing of maximum abundance and biomass, in spite of some differences in the initiation and duration of reproduction. A peak biomass and density occurred in 1989 in the Black and Azov Seas and in 1990 in the other seas. The M. leidyi invasion negatively affected the ecosystems of the Black Sea and the Sea of Azov. The zooplankton, ichthyoplankton and zooplanktivorous fish stocks all underwent profound changes. Similar effects, but less pronounced, were recorded in the Sea of Marmara. Effects on Mediterranean food chains have, so far, remained insignificant. Salinity is probably supraoptimal here, and several predators prevent M. leidyi from reaching outbreak levels.     

特尔斐—模糊综合比较法评价生态环境质量变化

根据生态系统的组成,利用特尔斐测定法选定影响环境的因子,确定其权重,现场监测调查实际资料,判定各因子的作用分值,采用模糊综合法计算出生态环境变化前后的综合分值,以判定生态环境质量变化前后的好坏。     

天津市空气污染预报方法

文章论述了空气污染预报几种理论和方法,特别详细介绍了天津市空气质量预报方法及其应用效果。     

Life cycle assessment of disposal of residues from municipal solid waste incineration: recycling of bottom ash in road construction or landfilling in Denmark evaluated in the ROAD-RES model

Two disposal methods for MSWI bottom ash were assessed in a new life cycle assessment (LCA) model for road construction and disposal of residues. The two scenarios evaluated in the model were: (i) landfilling of bottom ash in a coastal landfill in Denmark and (ii) recycling of bottom ash as subbase layer in an asphalted secondary road. The LCA included resource and energy consumption, and emissions associated with upgrading of bottom ash, transport, landfilling processes, incorporation of bottom ash in road, substitution of natural gravel as road construction material and leaching of heavy metals and salts from bottom ash in road as well as in landfill. Environmental impacts associated with emissions to air, fresh surface water, marine surface water, groundwater and soil were aggregated into 12 environmental impact categories: Global Warming, Photochemical Ozone Formation, Nutrient Enrichment, Acidification, Stratospheric Ozone Depletion, Human Toxicity via air/water/soil, Ecotoxicity in water/soil, and a new impact category, Stored Ecotoxicity to water/soil that accounts for the presence of heavy metals and very persistent organic compounds that in the long-term might leach. Leaching of heavy metals and salts from bottom ash was estimated from a series of laboratory leaching tests. For both scenarios, Ecotoxicity(water) was, when evaluated for the first 100 yr, the most important among the twelve impact categories involved in the assessment. Human Toxicity(soil) was also important, especially for the Road scenario. When the long-term leaching of heavy metals from bottom ash was evaluated, based on the total content of heavy metals in bottom ash, all impact categories became negligible compared to the potential Stored Ecotoxicity, which was two orders of magnitudes greater than Ecotoxicity(water). Copper was the constituent that gave the strongest contributions to the ecotoxicities. The most important resources consumed were clay as liner in landfill and the groundwater resource which was potentially spoiled due to leaching of salts from bottom ash in road. The difference in environmental impacts between landfilling and utilization of bottom ash in road was marginal when these alternatives were assessed in a life cycle perspective.     

Temporal variations of airborne particles concentration in the Brussels environment

We report and analyze data on the PM10 fraction of airborne particles measured at five recording stations in the Brussels region from October 2002 till September 2003. These stations are representative of the various activity sectors of the Brussels urban area. The objective was the determination of the origin of the PM10 particles (particles up to 10 μm) that are recorded in that region in order to follow the EU directives concerning tolerance level of airborne particles concentration. In order to evaluate the impacts of local and external factors that inject solid particles in the atmosphere of Brussels we compared concentration data from working and not working (holidays) periods. Moreover, we also compared concentrations from periods of agricultural activity and rest in the Brabant provinces surrounding the Brussels region for various crop types. The results lead to the conclusion that the impact or urban traffic is rather limited while that of the agricultural activities is important. Moreover, there appears a clear-cut distinction between different types of crops.     

Deterioration of water quality of Surma river

Surma River is polluted day by day by human activities, poor structured sewerage and drainage system, discharging industrial and household wastes. The charas (natural channels) are responsible for surface runoff conveyance from its urban catchments to the receiving Surma River. Water samples have been collected from a part of Surma River along different points and analyzed for various water quality parameters during dry and monsoon periods. Effects of industrial wastes, municipal sewage, and agricultural runoff on river water quality have been investigated. The study was conducted within the Chattak to Sunamganj portion of Surma River, which is significant due to the presence of two major industries – a paper mill and a cement factory. The other significant feature is the conveyors that travel from India to Chattak. The river was found to be highly turbid in the monsoon season. But BOD and fecal coliform concentration was found higher in the dry season. The water was found slightly acidic. The mean values of parameters were Conductivity 84–805 μs; DO: dry-5.52 mg/l, monsoon-5.72 mg/l; BOD: dry-1mg/l, monsoon-0.878 mg/l; Total Solid: dry-149.4 mg/l, monsoon-145.7 mg/l. In this study, an effort has been taken to investigate the status of concentration of phosphate (PO⁻⁴) and ammonia–nitrogen (NH₄–N) at four entrance points of Malnichara to the city, Guali chara, Gaviar khal and Bolramer khal. Data has been collected from March–April and September–October of 2004. Concentrations have been measured using UV Spectrophotometer. Although the phosphate concentration has been found within the limit set by DOE for fishing, irrigation and recreational purposes, however ammonia–nitrogen has been found to exceed the limit.     

Contributions of deposited particles to pine needle polycyclic aromatic hydrocarbons

The contributions of deposited particles (P) to polycyclic aromatic hydrocarbon (PAH) levels in pine (Cedrus deodar) needles sampled from the Dalian region were evaluated by washing off the particles from pine needle surfaces. P values ranged from 4.4 +/- 2.2% for fluorene to 69.9 +/- 4.0% for indeno(1,2,3-cd)pyrene, and positively correlated with the logarithm of octanol-air partition coefficients (log K OA) of each PAH significantly. P and the total levels of 14 PAHs under study ( summation PAHs), that ranged from 490 to 3241 ng g(-1) dw (dry weight) with median value of 1521 ng g(-1) dw, were high for traffic areas, and low for residential or park areas, implying the significant contributions of PAHs in both gas and particle phases emitted by vehicles. However, PAH profiles in pine needles were not significantly altered by the washing, due to the low fractions (2-5%) of the 5- and 6-ring PAHs in summation PAHs. The high wind speed and frequently alternating wind directions in the Dalian spring could quicken the depuration processes of pine needle PAHs. Thus, the local meteorological conditions and source variations should be taken into account when using pine needles to implicate seasonal variations of atmospheric semi-volatile organic compounds.     

Occurrence of organic contaminants in sewage sludges from eleven wastewater treatment plants, China

This study presents the occurrence of 43 semi-volatile organic compounds (SVOCs) listed as priority pollutants by both China and the United States Environmental Protection Agency, in sewage sludges collected from eleven wastewater treatment plants (WWTPs) of mainland and Hong Kong, China. Thirty-six SVOCs were detected by gas chromatography coupled with mass spectrometer (GC-MS) and at least 14 in each sample. The most abundant compounds were phthalic acid esters (PAEs) and polycyclic aromatic hydrocarbons (PAHs) with total concentrations ranging from 10 to 114mgkg(-1) dry weight (d.w.) (with a mean of 30mgkg(-1) d.w.) and from 1.4 to 33mgkg(-1)d.w. (with a mean of 16mgkg(-1) d.w.), respectively, followed by chlorobenzenes, nitroaromatics, haloethers and halogenated hydrocarbons which occurred generally at concentrations lower than 10mgkg(-1) d.w. Large variations were observed between the concentrations of individual compounds as well as their total concentrations in sludge samples from different WWTPs. The highest values of sum concentration of 16 PAHs and of 6 PAEs were found in sewage sludge from Beijing. The mean total concentration of each class of SVOCs in sewage sludge from mainland was remarkably higher than that from Hong Kong. The concentrations of di(2-ethylhexyl) phthalate in 91% sludge samples met the limit (100mgkg(-1)d.w.) proposed by the Europe Union for land application, whereas the PAH concentrations of 64% sludge samples exceeded the maximum permissible concentration (6.0mgkg(-1)d.w.). The occurrence of SVOCs in this study are compared with other studies and their sources are discussed.