北京某垃圾填埋区空气细菌浓度及粒径分布特征

以北京市某垃圾填埋区中作业区和覆盖区的空气细菌为主要研究对象,研究四个季节空气细菌浓度及粒径分布特征,得出了以下结论:垃圾填埋区作业区空气细菌浓度四季变化特征较覆盖区显著,且空气细菌浓度高于覆盖区。垃圾填埋区作业区和覆盖区四季的空气细菌粒子主要分布在前4级中,且在第Ⅵ级(<1.0μm)中分布比例最小,但分布规律不完全相同。秋季作业区最易感染人体的空气细菌浓度最高。垃圾填埋区作业区和覆盖区空气细菌中值直径最小值均出现在夏季,最大值均出现在冬季。     

Influence of thermal environment on metallographic structure characteristics of the electric arc bead pattern

Electrical apparatuses are prone to arc, which generally causes a fire, even an explosion hazard, when a flammable gas mixture is present, especially during industrial processes. Terrible fire scenes are challenging for fire investigations. In this work, by performing a simultaneous thermal analysis test we simulated a fire environment and found that as the oxygen concentration decreased, the oxidation/exothermic peak temperature of ‘cause’ bead became higher, but the melting temperature was unaffected. Results indicated that the bead pattern underwent oxidation at approximately 831 °C, melting initiated at approximately 1060 °C, and the pattern then disappeared. The melted pattern grain changes were divided into three critical temperature stages: Approximately 600 °C, the onset temperature at which the melted pattern grains began to be equiaxed; approximately 831 °C, at which the grains were interspersed with oxygen-containing material; and 831–1060 °C, when the grains disappeared, which is a criterion for identifying electrical fires. However, the boundaries remained throughout the thermal environment process. Moreover, the bead pattern demonstrated three metallographic regions: Deep layer (Region I), the intermediate layer (Region Ⅱ), and surface layer (Region Ⅲ). Region I was the most thermally sensitive, in which equiaxed crystals first appeared. Region Ⅲ was the thermal reaction lag zone, in which the typical branching crystals finally disappeared, and Region Ⅱ was intermediate between Regions I and Ⅲ. The results may help fire investigators determine the fire scene temperature stages and provide support for fire evidence extraction.     

Variations in the chemical properties of landfill leachate

Landfill leachates were collected and their chemical properties analyzed once every two months over a ten-month period from the Gin Drinkers' Bay (GDB) and Junk Bay (JB) landfills. The contents of solids, and inorganic and organic components fluctuated considerably with time. In general, the chemical properties of the two leachates correlated negatively (P<0.05) with the amounts of rainfall prior to the sampling periods. However, magnesium and pH of the leachates remained relatively constant with respect to sampling time. The JB leachate contained higher average contents of solids and inorganic and organic matter than those of GDB with the exception of trace metals. Trace metals were present in the two leachates in trace quantities (<1.0 mg/liter). The concentrations of average ammoniacal nitrogen were 1040 and 549 mg/liter, while chemical oxygen demand (COD) values were 767 and 695 mg/liter for JB and GDB leachates, respectively. These results suggest that the leachates need further treatment before they can be discharged to the coastal waters.     

陈垃圾特性分析及其适用性评价

对深圳市盐田区垃圾场处置工程陈垃圾特性进行了分析，结果表明，场内陈垃圾已基本腐熟，相对附近农田土壤，陈垃圾中的营养物质较高，接近但尚未完全达到农用垃圾肥标准，且铅含量超标２～３ 倍，不宜进入食物链。但陈垃圾可用作市区绿化地带、公园、苗圃、林业等处的有机肥和垃圾填埋场封场工程的表层营养土     

垃圾填埋场垃圾堆体压实机理研究

通过填埋场现场运行实验，对生活垃圾在填埋场中的压实机理进行了研究，实验结果表明，压力是决定压实效果的最重要的外在因素，垃圾在外力下的形变大体可分为三个阶段：垃圾组分之间的大空隙被填没，垃圾体不可逆蠕变，垃圾体的范性变形；决定压实效果的内在因素有垃圾组分、垃圾含水率等。另外，作业过程中垃圾堆体的摊铺厚度、机械行程次数、行驶速度和坡向及坡度等也是影响垃圾堆体压实效果的重要因素。     

厌氧折流板反应器处理垃圾渗滤液的试验研究

试验所用废水取自于已经封场多年的广州市大田山垃圾填埋场的渗滤液,其方法是对比原有的ABR工艺与在原有的ABR工艺中加入生物接触氧化池进行可行性试验研究,以求达到更好的处理效果.研究结果表明,组合新工艺可使进水的CODCr去除41%,NH3-N去除17%,比原有单一工艺的处理效果好,从而减少了后续工艺的处理负荷.     

城市生活垃圾半好氧生物反应器填埋技术试验研究

对城市生活垃圾半好氧生物反应器填埋技术与传统垃圾填埋技术进行了对比试验,由试验结果可知,半好氧生物反应器填埋技术可缩短填埋垃圾产酸时间,净化渗滤液,加速填埋垃圾稳定化进程.城市生活垃圾半好氧生物反应器填埋技术是中国中小城市垃圾填埋处理的发展方向.     

混凝-折流式反应器对垃圾渗滤液处理的试验研究

采用混凝、三组水解池和好氧生物滤池串连组成的折流式反应器(BR)联合工艺,对处理芜湖市南郊垃圾填埋场产生的渗滤液进行了试验研究,确定了混凝剂的最佳投加量、最佳碱化脱氮pH等工艺参数.试验结果表明,经过水解反应器(HUSB)反复对垃圾渗滤液进行水解酸化后,能逐步提高废水的BOD5/COD(B/C)(约0.2～0.4),大大提高了好氧生物滤池的COD容积负荷,出水COD平均《400 mg/L,NH3-N平均《30 mg/L.     

Response of Savanna Fire Regimes to Changing Fire-Management Policies in a Large African National Park

Abstract:  Approaches to fire management in the savanna ecosystems of the 2-million ha Kruger National Park, South Africa, have changed several times over the past six decades. These approaches have included regular and flexible prescribed burning on fixed areas and a policy that sought to establish a lightning-dominated fire regime. We sought to establish whether changes in management induced the desired variability in fire regimes over a large area. We used a spatial database of information on all fires in the park between 1957 and 2002 to determine elements of the fire regime associated with each management policy. The area that burned in any given year was independent of the management approach and was strongly related to rainfall (and therefore grass fuels) in the preceding 2 years. On the other hand, management did affect the spatial heterogeneity of fires and their seasonal distribution. Heterogeneity was higher at all scales during the era of prescribed burning, compared with the lightning-fire interval. The lightning-fire interval also resulted in a greater proportion (72% vs. 38%) of the area burning in the dry season. Mean fire-return intervals varied between 5.6 and 7.3 years, and variability in fire-return intervals was strongly influenced by the sequencing of annual rainfall rather than by management. The attempt at creating a lightning-dominated fire regime failed because most fires were ignited by humans, and the policy has been replaced by a more pragmatic approach that combines flexible prescribed burning with lightning-ignited fires.