Modified landfill gas generation rate model of first-order kinetics and two-stage reaction

This investigation was carried out to establish a new domestic landfill gas (LFG) generation rate model that takes into account the impact of leachate recirculation. The first-order kinetics and two-stage reaction (FKTSR) model of the LFG generation rate includes mechanisms of the nutrient balance for biochemical reaction in two main stages. In this study, the FKTSR model was modified by the introduction of the outflow function and the organic acid conversion coefficient in order to represent the in-situ condition of nutrient loss through leachate. Laboratory experiments were carried out to simulate the impact of leachate recirculation and verify the modified FKTSR model. The model calibration was then calculated by using the experimental data. The results suggested that the new model was in line with the experimental data. The main parameters of the modified FKTSR model, including the LFG production potential (L ₀), the reaction rate constant in the first stage (K ₁), and the reaction rate constant in the second stage (K ₂) of 64.746 L, 0.202 d⁻¹, and 0.338 d⁻¹, respectively, were comparable to the old ones of 42.069 L, 0.231 d⁻¹, and 0.231 d⁻¹. The new model is better able to explain the mechanisms involved in LFG generation.     

跨国界污染案例对处理松花江污染事件的启示

跨国界污染事件的处理或赔偿涉及国家责任、赔偿范围和赔偿主体等问题。本文介绍了与环境保护相关的国际法和国际公约的法律，并对影响较大的几起跨境污染案例作了分析，就处理此次松花江事故污染事件以及跨国污染赔偿等提出相关建议。     

真实储蓄:中国可持续发展的测量与检验

用真实储蓄进行可持续发展的跨国比较已广为采用,关于真实储蓄指标的有效性检验的研究正在开展.本文汇集两类较具代表性的检验方法,测算世界银行提供的1960至2006年中国真实储蓄率的有效性.研究发现基于相同理论的不同检验方法,得出的结论互相抵触.本文从数据构造与经济计量模型两个方面分析,得出数据构造方法的不同是造成上述现象的重要原因,而中国储蓄检验结果的不理想,则源于检验模型的假设不适于我国的数据.     

Odor compounds from different sources of landfill: characterization and source identification

This study investigated the odor compounds from different areas in a landfill site, which included the municipal solid waste (MSW)-related area, the leachate-related area and the sludge-related area. Nine sampling points were placed and 35 types of odorous substances were measured and quantified from these grabbed samples. The results showed that the main odorous substances emitted from landfill site were styrene, toluene, xylene, acetone, methanol, n-butanone, n-butylaldehyde, acetic acid, dimethyl sulfide, dimethyl disulfide and ammonia. In the MSW-related area, the highest concentrations of oxygenated compounds were observed at the gas extraction wells (GW), while sulfur compounds were rare. Ammonia in the sludge-related area was very abundant. Sludge discharge area (SD1) and sludge disposal work place (SD2) were representative points of pre- and post-drying, in which the characterizations of the emitted odorous gas were different. After chemical drying, the concentration of ammonia increased, whereas those of volatile fatty acids and sulfur compounds decreased. In the leachate-related area, relatively low concentrations of all those odorants were detected in leachate storage pool (LS), which may be due to the enclosure operation of the leachate storage pool. Using principal components analysis and cluster analysis, GW, SD1 and SD2 were distinguished from the other sampling points. The typical odorants in GW were acetaldehyde, ethyl benzene, xylene, methylamine and dimethyl formamide. The typical odorants in SD1 were methyl mercaptan, valeric acid and isovaleric acid, while those in SD2 were carbon disulfide, acetone, 3-pentanone, methanol and trimethylamine. The typical odorants in other sampling points were hydrogen sulfide, n-butylaldehyde and acetic acid.     

Low maternal host-encounter rate enhances offspring proliferation in a polyembryonic parasitoid

Mothers can epigenetically influence their progeny’s characteristics in response to environmental conditions they experience, thereby increasing offspring adaptation to anticipated future conditions. When resource shortage is anticipated, females are expected to produce larger offspring, as large body size often confers competitive and dispersal advantages. We tested this hypothesis using the polyembryonic parasitoid, Copidosoma koehleri. In this wasp, each egg proliferates into a clone of genetically identical individuals within its moth host, and body size correlates negatively with clone size. We expected females anticipating resource limitation to produce fewer and larger offspring per clone than females that anticipate abundant resources. Encounter rates of parasitoid females with hosts were manipulated to simulate varying levels of resource availability. High-encounter-rate females were introduced to ten hosts successively, while low-encounter-rate females encountered each of ten hosts at 8-h intervals. To control for female age at oviposition, we also introduced females at different ages to a single host. Contrary to our predictions, low-encounter-rate females produced larger offspring clones than high-encounter-rate females, and offspring body size did not differ between treatments. Low-encounter-rate females were shorter-lived than females that encountered hosts successively. Single-oviposition females resembled the high-encounter-rate females in longevity but produced as many offspring per clone as in the low-encounter-rate treatment. Female age, and number of previous host encounters, did not affect offspring clone size. These results suggest that offspring proliferation bears a cost to mothers, thus mothers that repeatedly induce high proliferation in their offspring pay an increased price.     

Concentrations, sources and spatial distribution of polycyclic aromatic hydrocarbons in soils from Beijing, Tianjin and surrounding areas, North China

The concentrations, profiles, sources and spatial distribution of polycyclic aromatic hydrocarbons (PAHs) were determined in 40 surface soil samples collected from Beijing, Tianjin and surrounding areas, North China in 2007, and all sampling sites were far from industrial areas, roadsides and other pollution sources, and across a range of soil types in remote, rural villages and urban areas. The total concentrations of 16 PAHs ranged from 31.6 to 1475.0 ng/g, with an arithmetic average of 336.4 ng/g. The highest PAH concentrations were measured in urban soils, followed by rural village soils and soils from remote locations. The remote-rural village-urban PAH concentration gradient was related to population density, gross domestic product (GDP), long-range atmospheric transport and different types of land use. In addition, the PAH concentration was well correlated with the total organic carbon (TOC) concentration of the soil. The PAH profile suggested that coal combustion and biomass burning were primary PAH sources.     

拟除虫菊酯农药的微波辅助无极汞灯下的降解机理研究

在水溶液中,以微波辅助无极汞灯(Microwave-Assisted Eletrodeless Discharge Mercury Lamp,MW-EDML)降解氯氰菊酯、甲氰菊酯和功夫菊酯等3种拟除虫菊酯农药(Synthetic pyrethroids,SPs),采用固相萃取(Solid Phase Extraction,SPE)富集后,用GC-MS鉴定降解产物,并根据降解产物重点探讨了SPs的降解机理。3种SPs的主要降解产物有6种,其降解途径有:酯键水解、氰基水解、脱羧、醚键断裂、氧化、苯环的羟基化以及与溶剂反应等。实验结果还表明:MW-EDML是个高效、简便的降解SPs类农药手段,可应用于其他有机污染物的降解过程。     

Na_2CO_3对超临界水氧化有机氯化物的防腐蚀作用

在间歇式超临界水氧化设备中进行有无Na2CO3参与的超临界水氧化五氯硝基苯对比实验,用分光光度法检测实验流出液中Cr3+的浓度,分析判断不锈钢反应器腐蚀状况。结果表明,Na2CO3对超临界水氧化有机氯化物具有有效的防腐蚀作用,并探讨了防腐蚀机理。     

浅论如何控制高校贷款的产生

随着高校的快速发展,财政拨款已不能满足高校发展的要求,作为不是营利机构的高校,银行贷款风险逐步增大,这就给高校今后的发展埋下隐患.而作为高校的最终责任承担者政府,应该对高校贷款进行约束和监督,并采取一系列的措施扶持,缓解高校贷款的产生,同时高校也应积极应对,从多方面、多渠道筹措资金来抑制银行贷款的产生.参5.