铅在湘江悬浮物上的吸附速率研究

到目前为止,研究铅在悬浮物上吸附的资料还很少,而有关铅在悬浮物上吸附速率的研究就更少了。黎秉铭、金相灿、Fumitada和Kuo等曾研究了铅在河流悬浮物上的吸附。研究结果表明,河流中的悬浮物对铅的吸附能力比对镉的吸附能力大得多,其吸附速度也比镉快。因此,在碱性环境中,天然水体对铅的自净能力很强。     

Polycyclic aromatic hydrocarbons and organochlorine pesticides in surface soils from the Qinghai-Tibetan plateau

Eighty eight surface soil samples were collected from the Qinghai-Tibetan Plateau (QTP) for determination of polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs), including dichlorodiphenyltrichloroethane and metabolites (DDXs) and hexachlorocyclohexane isomers (HCHs). The measured concentrations were 51.8 ± 38.5 ng g(-1), 0.329 ± 0.818 ng g(-1), and 0.467 ± 0.741 ng g(-1) as means and standard deviations of PAHs, DDXs, and HCHs, respectively, which were 1-2 orders of magnitude lower than those reported for eastern China. Significant differences were also revealed among four sub-areas within QTP. PAHs detected in the samples from the remote sub-areas of T'ang-ku-la/Hoh Xil Mountains and along the Qinghai-Tibet highway in the west and northwest of QTP were 1 order of magnitude lower than those from Lhasa and east Qinghai. The differences in soil OCPs among the sub-areas were 2-7 times. Soil PAHs were significantly correlated with emission density and soil organic carbon content (SOC), while OCPs were correlated significantly with the population density and SOC. Based on the calculated backward air mass trajectories and geographical distributions of emission and population, it was revealed that PAHs and OCPs accumulated in the soils in the west and northwest QTP were primarily from long-range transport and may represent the background levels of East Asia. This part of QTP can also serve as an important receptor area for regional or even global long-range transport study. The elevated concentrations of PAHs and OCPs in Lhasa and east Qinghai were mainly from local sources, while PAHs from adjacent Lanzhou area also contributed considerably to the accumulation of PAHs in east Qinghai.     

Combustion aerosols: factors governing their size and composition and implications to human health

Particulate matter (PM) emissions from stationary combustion sources burning coal, fuel oil, biomass, and waste, and PM from internal combustion (IC) engines burning gasoline and diesel, are a significant source of primary particles smaller than 2.5 microns (PM2.5) in urban areas. Combustion-generated particles are generally smaller than geologically produced dust and have unique chemical composition and morphology. The fundamental processes affecting formation of combustion PM and the emission characteristics of important applications are reviewed. Particles containing transition metals, ultrafine particles, and soot are emphasized because these types of particles have been studied extensively, and their emissions are controlled by the fuel composition and the oxidant-temperature-mixing history from the flame to the stack. There is a need for better integration of the combustion, air pollution control, atmospheric chemistry, and inhalation health research communities. Epidemiology has demonstrated that susceptible individuals are being harmed by ambient PM. Particle surface area, number of ultrafine particles, bioavailable transition metals, polycyclic aromatic hydrocarbons (PAH), and other particle-bound organic compounds are suspected to be more important than particle mass in determining the effects of air pollution. Time- and size-resolved PM measurements are needed for testing mechanistic toxicological hypotheses, for characterizing the relationship between combustion operating conditions and transient emissions, and for source apportionment studies to develop air quality plans. Citations are provided to more specialized reviews, and the concluding comments make suggestions for further research.     

Artificial acidification of a non-acidic and an acidic headwater stream in Maine, USA

Two headwater streams with low DOC and different pHs (4.5-4.8 and 5-6.5) were acidified with H2SO4 to pH 4.1 and 4.5, respectively, for 24-h periods. Neutralization of the added acid occurred by protonation of ANC (HCO3-dominated in the higher pH stream), desorption of Ca (< 15 microeq litre(-1)) and Mg (<6 microeq litre(-1)), and desorption and dissolution of AL (<250 microg litre(-1)) from the stream bed. The concentrations of dissolved organic carbon (DOC) remained constant within the experimental reaches. The concentrations of Na, K an H4SiO4 also remained constant, indicating no detectable increase in the rate of chemical weathering in the stream bed. After acid addition was stopped, concentrations of Ca, Mg and Al decreased to below background, indicating reversible ion exchange as the principal mechanism for the mobility of Ca and Mg and to a lesser extent for Al. Repeated acidifications indicated that significant regeneration of cations on the exchange surfaces of the stream substrate occurs rapidly.     

Mechanisms of episodic acidification in low-order streams in Maine, USA

Five factors contribute to episodic depressions in pH and ANC during hydrologic events in low-order streams in Maine: (1) increases of up to 50 microeq litre(-1) NO3; (2) increases of up to 75 microeq litre(-1) organic acidity; (3) increases of as much as 0.3 in the anion fraction of SO4; (4) as much as 100 microeq litre(-1) acidity generated by the salt-effect in soils; and (5) typically < or = 40% dilution by increased discharge. In conjunction with increased discharge, factors 1, 2 or 4 appear necessary to depress pH to less than 5.0. The chemistry of individual precipitation events is irrelevant to the generation of acidic episodes, except those caused by high loading of neutral salts in coastal regions. Increases in discharge, but not necessarily in dilution of solutes, in combination with the chronically high SO4 from atmospheric deposition, provide the antecedent chemical conditions for episodic acidification. Differences in antecedent moisture conditions determine the processes that control output of either ANC or acidifying agents to aquatic systems.     

遥测网络系统的抗干扰与设计

讨论了遥测网络系统的原理与设计；介绍了以可编程序控制器（ＰＬＣ）为核心的城市大气质量遥测系统的抗干扰问题；分析了网络系统的实现方法。     

噪声对不同人格类型被试者视觉功能的不同影响

采用龚耀先修订的“艾克森人格问卷”中的调查方法,将华东师范大学的３６名大学生分为外向稳定、内向稳定、外向不稳定、内向不稳定等４个人格类型组,通过噪声暴露试验,研究其对不同人格类型式者视觉功能的影响。结果表明,噪声对内向不稳定定型被试乾的视觉影响最大,对外向稳定型影响最小;噪声对视深、视长和视野的影响程序也不相同,４种人格类型被试者在视深知觉和视野上均存在显著性差异,在视长智觉上未见任何显著性差异;     

Biofiltration of gasoline vapor by compost media

Gasoline vapor was treated using a compost biofilter operated in upflow mode over 4 months. The gas velocity was 6 m/h, yielding an empty bed retention time (EBRT) of 10 min. Benzene, toluene, ethylbenzene and xylene (BTEX) and total petroleum hydrocarbon (TPH) removal efficiencies remained fairly stable approximately 15 days after biofilter start-up. The average removal efficiencies of TPH and BTEX were 80 and 85%, respectively, during 4 months of stable operation. Biodegradation portions of the treated TPH and BTEX were 60 and 64%, respectively. When the influent concentration of TPH was less than 7800 mg TPH/m3, approximately 50% of TPH in the gas stream was removed in the lower half of the biofilter. When the influent concentration of BTEX was less than 720 mg BTEX/m3, over 75% of BTEX in the gas stream was removed in the lower half of the biofilter. Benzene removal efficiency was the lowest among BTEX. A pressure drop could not be detected over a 1-m bed height at a gas velocity of 6 m/h after approximately 4 months of operation. Results demonstrated that BTEX in gasoline vapor could be treated effectively using a compost biofilter.     

Comparison of models for describing measured VOC emissions from wood-based panels under dynamic chamber test condition

Measured emission factors are the experimental data used to represent emission characteristics of volatile organic compounds (VOCs) from testing materials under dynamic chamber test conditions. A simple empirical model that describes the measured emission factors will be very useful for practical purposes. In this study, a power law model was compared with a widely used first-order exponential decay model in their ability to describe measured emission factors of wood-based panel materials. It was demonstrated that the power law model is a better choice than the first-order model for describing emission characteristics for short-term (less than 100 h) experimental data. The power law model was also more superior in predicting long-term (up to 900 h) emission factors.