Differences of the oxidation process and secondary organic aerosol formation at low and high precursor concentrations

Current atmospheric quality models usually underestimate the level of ambient secondary organic aerosol(SOA), one of the possible reasons is that the precursors at different concentrations may undergo different oxidation processes and further affect SOA formation. Therefore, there is a need to perform more chamber studies to disclose the influence. In this work, SOA formation over a wide range of initial precursor concentrations(tens of ppb to hundreds of ppb levels) was investigated in a 30 m3 indoor smog chamber,and mainly through the analysis of multiple generations of VOCs detected from HR-To FPTRMS to expound the difference in the oxidation process between low and high precursor concentrations. Compared to high initial concentrations, gas-phase intermediates formed at low concentrations had a higher intensity by about one order of magnitude, and the lowvolatility compounds also had a higher formation potential due to the competition between semi-volatile intermediates and precursors with oxidants. In addition, the formed SOA was more oxidized with higher f44 value(0.14 ± 0.02) and more relevant to real atmosphere than that formed at high concentrations. This work should help to deeply understand SOA formation and improve the performance of air quality models for SOA simulation.     

煤燃烧过程中影响NO_x转化的因素探讨

利用管式沉降炉对煤粉燃烧过程中的反应温度、初始氧浓度、反应时间、煤的挥发分及含氧量对燃料氮向NOx 转化的影响进行了试验研究 ,摸清了反应的规律 ,找出了影响转化的显著因素。     

Sexual selection,male morphology,and the efficacy of courtship signalling in two wolf spiders (Araneae: Lycosidae)

Males of the brush-legged wolf spider, Schizocosa ocreata (Araneae: Lycosidae), possess a conspicuous male secondary sexual character: dark pigmentation and tufts of bristles on the tibiae of their forelegs. We tested several hypotheses relating to the role of this conspicuous trait in sexual selection. Triad mating experiments suggest that the tufts do not play an obvious role in the operation of sexual selection by either male competition or female choice, as there were no significant differences in the mating success of intact and experimentally shaved males. However, females mated more often with males that initiated courtship first, suggesting that capture of a female’s attention by male signalling may play a critical role. In behavioral experiments that paired a single male with a female in arenas that allowed both visual and vibratory signal transmission during courtship, female receptivity did not vary significantly with the presence or absence of tufts. However, experiments that isolated the visual component of communication (by eliminating vibratory communication) revealed a significant effect of the presence of tufts: females showed receptivity less often to males with tufts removed. Female response to visual signals was much greater in S. ocreata than in its sibling congener, Schizocosa rovneri, which lacks male tufts. We hypothesize that the tufts serve to increase the efficacy of visual displays of S. ocreata, as vibratory communication is constrained by the complex leaf litter habitat of some populations. Such environmental constraints may make visual signalling over distance a critical factor for effective courtship communication, which may in turn strongly influence male fitness. Received: 30 September 1994/Accepted after revision: 4 August 1995     

Secondary imbibition in NAPL-invaded mixed-wet sediments

A previously developed pore network model is used here to study the spontaneous and forced secondary imbibition of a NAPL-invaded sediment, as in the displacement of NAPL by waterflooding a mixed-wet soil. We use a 3D disordered pore network with a realistic representation of pore geometry and connectivity, and a quasi-static displacement model that fully describes the pore-scale physics. After primary drainage (NAPL displacing water) up to a maximum capillary pressure, we simulate secondary imbibition (water displacing NAPL). We conduct a parametric study of imbibition by varying systematically the controlling parameters: the advancing contact angles, the fraction of NAPL-wet pores, the interfacial tension, and the initial water saturation. Once the secondary imbibition is completed, the controlling displacement mechanisms, capillary pressures, relative permeabilities, and trapped NAPL saturations are reported. It is assumed that NAPL migrates into an initially strongly water-wet sediment, i.e., the receding contact angles are very small. However, depending on the surface mineralogy and chemical compositions of the immiscible fluid phases, the wettability of pore interiors is altered while the neighborhoods of pore corners remain strongly water-wet-resulting in a mixed-wet sediment. Here, we compare three different levels of wettability alteration: water-wet (advancing contact angles (20 degrees to 55 degrees), intermediate-wet (55 degrees to 120 degrees), and NAPL-wet (120 degrees to 155 degrees). The range of advancing contact angles and the fraction of NAPL-wet pores have dramatic effects on the NAPL-water capillary pressures and relative permeabilities. The spatially inhomogeneous interfacial tension has a minor impact on the trapped NAPL saturation and relative permeability to NAPL, and a slight effect on the relative permeability to water. The initial water saturation has a slight effect on the two-phase flow characteristics of water-wet sediments; however, with more NAPL-wet pores in the sediment, it starts to have a profound effect on the water and NAPL relative permeabilities.     

A national critical loads framework for atmospheric deposition effects assessment: I. Method summary

The United States Environmental Protection Agency (EPA), with the assistance of the US Department of Energy (DOE) and the National Oceanographic and Atmospheric Administration (NOAA) is examining the utility of a critical loads approach for evaluating atmospheric pollutant effects on sensitive ecosystems. A critical load has been defined as, “a quantitative estimate of an exposure to one or more pollutants below which significant harmful effects on specified sensitive elements of the environment do not occur according to present knowledge.” Working in cooperation with the United Nations Economic Community for Europe’s (UN-ECE) Long Range Transboundary Air Pollution (LRTAP) Convention, the EPA has developed a flexible, six-step approach for setting critical loads for a range of ecosystem types. The framework is based on regional population characteristics of the ecosystem(s) of concern. The six steps of the approach are: (1) selection of ecosystem components, indicators, and characterization of the resource; (2) definition of functional subregions; (3) characterization of deposition within each of the subregions; (4) definition of an assessment end point; (5) selection and application of models; and (6) mapping projected ecosystem responses. The approach allows for variable ecosystem characteristics and data availability. Specific recognition of data and model uncertainties is an integral part of the process, and the use of multiple models to obtain ranges of critical loads estimates for each ecosystem component in a region is encouraged. Through this intercomparison process uncertainties in critical loads projections can be estimated. The research described in this article has been funded by the US Environmental Protection Agency. This document has been prepared at the EPA Environmental Research Laboratory in Corvallis, Oregon, through contract #68-C8-0006 with Man Tech Environmental Technology, Inc. It has been subjected to the agency’s peer and administrative review and approved for publication. Mention of trade names or commercial products does not constitute endorse ment or recommendation for use.     

1991年孟加拉湾特大台风灾害

１９９１年４月２９日孟加拉国发生一次特大台风灾害，死亡１３８０００人，损失３０亿美元。事后，孟加拉国政府组织了详细的调配分析。指出平坦低下地形、漏头状海岸线、落后的社会制度、人民极端贫穷是特大灾害的基本原因。另外，人民因过去几次错误预报而不相信台风警报；海堤很差，许多人住在海堤以外，住房很坏，通讯条件落后等等，更加剧了这次灾难。本文介绍这镒台风灾害的形成背景和灾害程度，供我国防台工作的参考。     

十四世纪以来我国地震次生水灾的研究

地震对于水利设施除直接造成堤防、堰坝等水工建筑物的破坏外,还可能形成堰塞湖,以及引发其他自然变异并形成水灾。在某些情况下,地震次生水灾所造成的损失比地震本身的损失还要大。本文在分析地震史料和重点现场查勘的基础上,将地震次生水灾从成因上和破坏机制上划分为六大类;提出了地震次生水灾的重点防范区;总结了地震次生水灾的特点;以及针对这些特点所应采取的减灾对策。     

A tool for estimating the contribution of water-soluble organic compounds to the particle mass and condensational growth in the atmosphere

In this theoretical investigation, we elucidated several factors governing the ability of organic, water-soluble vapours to participate into either the secondary organic aerosol formation or particle condensational growth in the atmosphere. The corresponding requirements for physico-chemical properties of the vapour were estimated. These estimates were also compared with the properties of several difunctional carboxylic acids identified in the atmosphere. Our analysis indicates that while many of the considered compounds are expected to contribute to the total particle mass in the atmosphere, their role in particle condensational growth process remains uncertain. This uncertainty emerges from the fact that the saturation ratio of an organic vapour does not alone determine its ability to act as a “nonvolatile” compound. Instead, the hygroscopic and chemical properties of the vapour, as well as the particle pH and size, have also to be taken into account.     

Adolescents’ attitudes towards nature and environment: Quantifying the 2-MEV model

This study identifies clearly the need for refinement of instrumentation in this area of environmental studies. A questionnaire battery designed to measure the factors Utilization (U) and Preservation (P) in the field of adolescent environmental perception was administered to 467 German secondary school pupils. Maximum likelihood factor analysis yielded the two hypothesized orthogonal factors U and P; we labelled this scale the 2-MEV model, i.e. the 2 factor Model of Environmental Values (sets of related attitudes). These analyses provide a basis for the construction of a questionnaire specifically designed to measure U and P. Confirmation of this factor structure was examined by comparing the factors extracted from two independent pseudorandom subsamples selected from the original sample.     

Women infected with parasite Toxoplasma have more sons

The boy-to-girl ratio at birth (secondary sex ratio) is around 0.51 in most populations. The sex ratio varies between societies and may be influenced by many factors, such as stress and immunosuppression, age, primiparity, the sex of the preceding siblings and the socioeconomic status of the parents. As parasite infection affects many immunological and physiological parameters of the host, we analyzed the effect of latent toxoplasmosis on sex ratios in humans. Clinical records of 1,803 infants born from 1996 to 2004 contained information regarding the mother’s age, concentration of anti-Toxoplasma antibodies, previous deliveries and abortions and the sex of the newborn. The results of our retrospective cohort study suggest that the presence of one of the most common parasites (with a worldwide prevalence from 20 to 80%), Toxoplasma gondii, can influence the secondary sex ratio in humans. Depending on the antibody concentration, the probability of the birth of a boy can increase up to a value of 0.72, C.I.₉₅ = (0.636, 0.805), which means that for every 260 boys born, 100 girls are born to women with the highest concentration of anti-Toxoplasma antibodies. The toxoplasmosis associated with immunosuppression or immunomodulation might be responsible for the enhanced survival of male embryos. In light of the high prevalence of latent toxoplasmosis in most countries, the impact of toxoplasmosis on the human population might be considerable.