三峡库区香溪河秋末至中冬CO2和CH4分压特征分析

为揭示三峡库区支流库湾表层水体秋末至中冬CH_4和CO_2的分压特征及其影响因素,于2014年相应时间段在香溪河库湾每天定点定时采取表层水样,利用顶空气相色谱技术测定水中溶解CH_4和CO_2的浓度,通过亨利定律计算CH_4和CO_2的分压,并同步监测相关环境因子.结果表明,表层水体CH_4分压变化范围0.64~4.43 Pa,平均值为(1.69±0.94)Pa,CO_2分压变化范围49.90~868.91 Pa,平均值为(328.48±251.63)Pa.水体CO_2和CH_4分压的变化呈显著负相关(r=-0.618,P0.01),p CH_4和p CO_2与溶解氧、总磷、叶绿素a、p H水温和水位相关性明显,其中p CO_2与各环境因子的相关性较p CH_4更为密切.     

Sulfur dioxide oxidation in laboratory clouds

SO₂ oxidation in the presence of NH₃ was studied in a mixing-type continuous-flow cloud chamber. NaCl and soot particles (∼5–15 μ m⁻³) were used as cloud condensation nuclei. Cloud liquid water content was varied between 0.2 and 3 g m⁻³. SO₂ and NH₃ concentrations were 0.6 and 1.1 ppm, respectively. The contact time between the SO₂ and the cloud drops was varied from 8 s to 3 min. Up to 80% of the input SO₂ can be oxidized within short contact times in the presence of NH₃ and when the water is in the condensed cloud-drop phase. Negligible sulfate formation was observed in the absence of the liquid phase regardless of the presence or absence of NH₃. No significant dependence of the oxidation on the cloud condensation nuclei type nor the contact time was found. This in-cloud SO₂ oxidation is much faster than predicted by S(IV) oxidation by molecular oxygen measured in bulk solutions.     

Volatilization of volatile organic compounds from showers—I. Analytical method and quantitative assessment

To provide data to test mathematical models developed to predict human exposure to Volatile Organic Compounds (VOCs) volatilizing from showers, an analytical method was developed to analyze the simultaneous volatilization of VOCs in the water and humid air of showers. Five VOCs with a wide range of Henry's law constants were used. Experiments, conducted in a full-scale shower, were performed at initial water concentrations nearing tap water VOC concentrations (a few μgλ⁻¹). VOCs in water and humid air samples were concentrated by purge-and-trap, thermally desorbed from a Tenax trap and analyzed with a gas chromatograph-electron capture detector. The fraction of the VOCs volatilized from showers at various water temperatures and flow rates were calculated. Mass-balane equations indicated the presence of sinks of VOCs in the experimental shower other than those due to the airflow. An experimental method to measure the residence time of the water in the shower is presented.     

Gap analysis of water governance in Northern Iran: A closer look into the water reservoirs

The amount of rainfall in Mazandaran province of Northern Iran is high. Mazandaran has man-made water reservoirs called Ab-bandan, to collect rainfall for irrigating rice farms during the growing seasons. However, rice farms face water scarcity because only a small amount of rainfall is being stored in Ab-bandans, while either the remaining water runs off into the sea, or causes water-logging or flooding. This research addresses Ab-bandans governance gaps in the Mazandaran province, using the ‘Multi-level Governance Framework’ introduced by the Organization for Economic Co-operation and Development (OECD). A modified Delphi technique with face-to-face interviews and a ranking round is used to identify Ab-bandans governance gaps. The identified gaps are classified into seven categories by applying the OECD's framework. In each of the categories there is one most important gap: the lack of a specific law for Ab-bandans, lack of long-term and strategic planning, low recognition of Ab-bandans at the national level, insufficient budget, lack of water user associations, lack of research in practice, and lack of using technology. The findings show that lack of a specific law for Ab-bandans in the country's water law is the most acute gap of all. In addition, the analysis highlights the fact that the policy category is the most critical one. The identified gaps are interlinked and exacerbate each other, therefore, a holistic perspective is needed to understand and resolve them. This study recommends a reform in the country’s water law, improved linkage between levels of government, co-operation among organizations involved in Ab-bandans management, and participation of local stakeholders in planning.     

A simplified heavy particle random-walk model for the prediction of drift from agricultural sprays

A simplified, two-dimensional random-walk model of particle dispersion that accounts for the crossing trajectories effect was proposed. The derived vertical particle velocity auto-correlation agreed adequately with the wind-tunnel measurements of Snyder and Lumley (1971, J. Fluid Mech.48, 41–71). The dispersion predictions of the model were compared with field spraying experiments using a range of drop sizes. In general, the model agreed closely with the experimental evidence, but slightly over-estimated dispersion in the far-field region.     

Smoke emission and burning rates for urban structures

Cribs, ordered arrays of sticks, were burned to mimic post-nuclear building fires. As the packing density of the cribs was increased to simulate blast damage, the smoke yield increased and the smoke changed from strongly light absorbing to whitish in color. A ventilation parameter proportional to the ratio of the crib vent area to the total fuel surface area correlated the burning rate and smoke yield data for both large (3.81 cm stick thickness) and small (0.64 cm stick thickness) scale cribs. The globally averaged smoke optical depth inferred from the burning of the wood cribs is in the low range of Penner's (1986, Nature324, 222–226) estimate. The smoke yield for freely burning cribs containing wood, gypsum, and plastic can be accounted for based on the high sooting yield of the plastic by itself.     

Numerical analysis of the role of sea breeze fronts on air quality in coastal and inland polluted areas

The role of moving sea breeze fronts on air quality in coastal and inland polluted areas was investigated by the numerical simulation of the transport/chemistry of air pollutants, using detailed structures of eddy diffusivity, temperature and flow fields associated with the moving sea breeze fronts. The eddy diffusivity field used was the output of a two-equation turbulence model (i.e. the k-ϵ model) and reasonably well expressed dynamical nature of turbulence in sea breeze, at its front and in an inland mixed layer (Kitada et al., 1987, Proc. Envir. Sani. Eng. Res.23, 103–113). The transport/chemistry of pollutants was calculated using a comprehensive Eulerian model, which adopts more than twenty chemical species advected (Kitada et al., 1983, Proc. 3rd. Int. Symp. on Numer. Methods in Engng, pp. 223–233; Carmichael et al., 1986, Atmospheric Environment20, 173–188).Several cases of numerical simulations were performed, being characterized by the locations of emission sources (i.e. coastal or inland), and the temporal activities of those. Results showed the following. In the coastal-source cases, (1) a circulation behind the sea breeze front was responsible for maintaining high concentration zone of photochemical product, just behind the front; (2) the local maximum of the product's concentration appeared at the upper part of the circulation (i.e. around a height of 500 m), where the temperature profile was stably stratified; (3) the concentration profile was vertically-uniform in the lower part of the circulation, where the thermal internal boundary layer extended over; in the inland-source cases, (4) updraft at the front swept away pollutants into the upper layer. Thus the vertical profile of the pollutant, having a peak at a higher level of 900–1000 m above ground, was formed; (5) this polluted zone at the higher layer remained for several hours after the front passed over. Finally, these indicate that the passage of the sea breeze front can result in complex layering of pollutants.     

A laboratory study of the efficiency with which aerosol particles are scavenged by snow flakes

An evaluation is made of presently available efficiencies with which aerosol particles are collected by snow crystals and aggregates of snow crystals (snow flakes). In this evaluation we incorporated our own recent experiments, carried out with naturally as well as with laboratory grown snow flakes inside a large walk-in cold chamber. Our evaluation shows that snow flakes are considerably more efficient in scavenging aerosol particles than single snow crystals. This result is supported by the recent wind tunnel studies of Lewet al. (1986,J. atmos. Sci.43, 2410–2417) on the uptake of supercooled drops by snow flakes, and by the theoretical studies of Redkin (1973,Hydrodynamics and Thermodynamics of Aerosols (edited by Voloshichok and Sedunov), pp. 220–238. Wiley, New York), who both attributed the high collection efficiency of snow flakes to a filtering effect involving the open mesh structure of the snow flakes. This conclusion can be understood on the basis of an analysis of the available collection efficiencies of aerosol particles by single snow crystals and snow flakes in terms of the Stokes number. The analysis shows that scavenging of aerosol particles of diameter larger than 0.2 μm by snow crystals larger than 1 mm in diameter is controlled by inertial capture. This mechanism plays only a very minor role in the capture of aerosol particles by snow flakes.     

Cloud chemistry at Mt Rigi,Switzerland: Dependence on drop size and relationship to precipitation chemistry

The chemical composition of winter and spring cloud water sampled at 1620 masl elevation on Mt Rigi in central Switzerland was dominated by NO₃⁻, SO₄²⁻, NH₄⁺ and H⁺. A wide range of concentration levels was observed, with maxima of 3700, 1800 and 4600 micronormal for NO₃⁻, SO₄²⁻ and NH₄⁺, respectively. Concentrations at a lower elevation (1030 masl) site on the mountain were higher due to lower cloud liquid water contents and higher pollutant levels at that site. The lowest pH observed was 2.95; large concentrations of NH₃ in the region prevented pH values from falling even lower. A comparison of simultaneously sampled cloud water and precipitation revealed much higher concentrations for most species in the cloud water, except in one case of extreme precipitation riming when the concentrations in the two phases converged. An exception to the pattern was H⁺; at times the precipitation was more acidic than the cloud water. The chemical composition of the cloud drops varied with drop size. Drops smaller than 10 μm diameter were enriched in NO₃⁻, SO₄²⁻ and NH₄⁺ relative to larger drops. Since the larger drops are the ones most effeciently captured by snow crystals, knowledge of their composition is essential to understanding the chemical implications of accretional growth of precipitation.     

The removal of sulphur dioxide in a long-lived line echo system: A numerical study

The removal of SO₂ in precipitation systems is not only a major sink of SO₂ but is also directly related to the acidity of precipitation. However the physical and chemical processes are not well understood due to their complicated characteristics. The lack of measurements also hinders us from studying those processes. In order to investigate what mechanisms are important about the removal of SO₂ in precipitation systems, an alternative approach is to examine the simulation result from a numerical cloud model.A two-dimensional version of the Klemp-Wilhelmson numerical model (1978, J. atmos. Sci.35, 1070–1096) is used to simulate a fast-moving long-lived line echo precipitation system that occurred in the Taiwan area during Mei-Yu season. The simulation model was assumed to be perpendicular to the north-south orientated line echo. In this simulation an artificial source of SO₂ is placed in front of the line echo system in the low level. As the line echo system approaches the region of SO₂, some SO₂ is brought into the line echo system through advection and diffusion effects. A simple parameterization scheme similar to Fisher's (1982, Atmospheric Environment16, 775–783) is used to represent the removal of SO₂ by cloud and rain. The model results show that the major sink of SO₂ is removed by rain below the cloud base although some is removed by cloud and rain inside the precipitation system itself.     

The oceanic source of carbonyl sulfide (COS)

Carbonyl sulfide (COS) concentrations both in sea water and in the marine atmospheric boundary layer have been measured for 2 years at Amsterdam Island, as well as during oceanographic cruises in regions of different productivity (coastal areas, upwelling areas and open ocean) in the Indian Ocean and Mediterranean Sea. Surface waters of the Indian Ocean and Mediterranean Sea were found to be supersaturated with respect to the atmosphere. The supersaturation of surface coastal sea water in COS displays a diurnal cycle with a midday/midnight ratio of approximately 4, and in addition a seasonal cycle with maximum values during summer and a summer/winter ratio of 2. The supersaturation of open ocean surface sea water is 3 times lower than that of the coastal areas. Taking into account the diurnal, seasonal and geographical variations of the sea water supersaturation in COS, along with the seasonal variation of the sea-air exchange coefficient and the Henry's law coefficient, a global oceanic flux of COS of 0.43 (0.30 to 0.60)Tg COS per year is estimated.     

Desorption of odor substances from water bodies to the atmosphere

A method is described for evaluation of odor pollution caused by waste-water. Two standard analytical procedures were applied to the determination of odor substances in water: head space analysis and purge-trap method. Henry's constants for five odor substances: hydrogen sulfide, methylmercaptan, dimethyl sulfide, ammonia and trimethylamine were measured at several conditions of pH and equilibrium temperature and were used for the estimation of odor emission from waste-water.     

Large-eddy simulation of dispersion in the convective boundary layer

Large-eddy simulation (LES) is used to study the dispersion of a passive scalar downwind of a localized source in a convective boundary layer. The LES turbulent velocity statistics are compared with laboratory data and other LES studies. Two scalar source heights at 0.25 z_i and 0.50 z_i are considered, where z_i is the inversion height, and the mean concentration fields are compared with the experimental data of Willis and Deardorf (1978, Atmospheric Environment12, 1305–1312; 1981, Atmospheric Environment15, 109–117). Emphasis is placed on the fluctuating component of the concentration field due to the random turbulent velocity fluctuations, and amplitudes, temporal and spatial scales, and probability distributions are examined. Concentration fluctuation intensity continually decreases downstream, suggesting zero intensity as the asymptotic limit. Vertical profiles of both mean concentration and fluctuation variance become well mixed downstream. Dissipation and correlation scales increase nearly in proportion to the plume width, so that time- and space-averaging the concentration is less effective in reducing the fluctuations further downstream. Concentration probability distributions show intermittency near the source but become nearly normal as the plume moves downstream. Results are compared and contrasted with the neutral flow study of Sykes and Henn (1992a, Atmospheric Environment26A, 3127–3144).     

Uncertainty-based quantitative assessment of sustainability for higher education institutions

Evaluation of sustainability in various facets of life is gaining increasing importance. Traditionally, different multi-criteria decision-making methods have been used for sustainability assessment. “Sustainability” can be a qualitative concept, and as such several researchers have attempted fuzzy logic for the quantitative assessment of sustainability. This paper outlines a new evaluation model based on fuzzy multi-criteria decision-making. The model is tested for sustainability assessment of higher education institutions (HEIs). It is based on a driving force–pressure–state–exposure–effect–action (DPSEEA) framework and is called uncertainty-based DPSEEA-Sustainability index Model (uD-SiM). The uD-SiM is a causality-based model in which the sustainability index is an outcome of nonlinear impacts of sustainability indicators in different stages of DPSEEA. The percent contribution of driving forces on the sustainability index of HEI is investigated using sensitivity analysis. The study reveals that education in sustainability and global and local research trends are the major driving forces for achieving sustainability in HEI, followed by financial and economic growth rate, social equity, energy requirements rate, and institutional enhancement, in descending order. The results of uD-SiM were found to be more realistic and rational than our earlier proposed approach, D-SiM.     

Determinations of methyl iodide in the Antarctic atmosphere and the south polar sea

Methyl iodide (CH₃I) concentrations were determined in the atmosphere and in surface sea water near the Antarctic Peninsula with a GC/ECD system during October–December 1987. The mean air concentration of methyl iodide was 2.4 pptv with a corresponding seawater concentration of 2.6 ng l⁻¹. In addition chloroiodomethane (CH₂ClI) was detected in some of the seawater samples as a second volatile organoiodine species. No relationship between methyl iodide and biogenic brominated methanes was found. From this it follows that methyl iodide has a different pathway of biogenic production in marine organisms than the brominated methanes. Based on a two-phase model a global sea-to-air flux for methyl iodide of 8 × 10¹¹ g yr⁻¹ was calculated. This is important for the balance of the global biogeochemical iodine cycle assuming that methyl iodide is by far the dominant volatile organoiodine species in the environment.     

Southern California air quality study: A search for methyl nitrate

Methyl nitrate, CH₃ONO₂, was measured by electron capture gas chromatography (EC-GC) under conditions which allowed resolution of methyl nitrate, PAN, and several chlorinated hydrocarbons. Calibrations involved both EC-GC andNO_x chemiluminescence and were in agreement with independent calibrations involving i.r. spectroscopy. The rate constant for photolysis of methyl nitrate in sunlight was< 2.3 × 10⁻⁶s⁻¹. Detection limits of field instruments were 0.1–0.4 ppb. Some 3000 EC-GC chromatograms grams of ambient air recorded between June and December 1987, during the Southern California Air Quality Study (SCAQS) at up to nine Southern California locations yielded only seven possible, but unlikely observations of methyl nitrate. Thus, methyl nitrate was only a minor component among nitrogenous air pollutants during SCAQS. The measured CH₃ONO₂/PAN ratios of<0.003–0.2 during SCAQS are discussed in terms of available kinetic data for PAN unimolecular decomposition (a major source of methyl nitrate), PAN thermal decomposition and CH₃ONO₂ photolysis.     

Aerosol formation and growth in atmospheric organic/NOχ systems—II. Aerosol dynamics

Aerosol dynamics that were observed in the outdoor smog chamber experiments described in Wang et al. (1992, Atmospheric Environment, 26A, 403–420) aresimulated by numerical solution of the aerosol general dynamic equation. The vapor source generation rate was estimated directly from the experimental measurements assuming a single surrogate condensing species for each hydrocarbon studied. Sensitivity analysis of the simulated aerosol dynamics to various input parameters revealed that the physical properties of the condensing vapor are important in determining the interplay between nucleation and condensation while the vapor source generation rate is the only factor that determines the eventual total amount of vapor converted to aerosol. The simulations suggest that over 99% of the mass of condensible vapor is converted to aerosol by condensation even when a significant burst of nucleation occurs.     

湿法炼锌高盐废水的综合回收实验研究

采用“预处理除杂—蒸发—盐分离结晶”技术对锌烟尘处理厂产出的高盐废水进行了探索实验研究.结果表明：采用该技术处理锌冶炼高盐废水,分别得到合格生产用水、无水硫酸钠和氯化钠,高盐废水实现了资源化回收利用.中和后的浓盐水加热到95~100℃进行高温蒸发浓缩,分离得到结晶盐无水硫酸钠,含量为98.79%,达到Ⅱ类优等品质量标准;蒸发得到的冷凝水电导率≤48μS/cm,水质达到生产用水标准.高温蒸发后期,氯化钠富集在少量的残余液中,保持60℃低温蒸发,分离得到结晶盐氯化钠,其中氯化钠含量为93.82%.     

基于聚合多巴胺的磁性碳材料的制备及其对甲基绿的吸附

以聚合多巴胺为碳源制备碳材料包覆的磁性纳米颗粒.通过多巴胺的自聚合反应将其包覆在Fe_3O_4纳米颗粒上,在氩气保护下高温灼烧得Fe_3O_4@C复合材料.包覆碳材料后,Fe_3O_4颗粒的稳定性和分散性提高.使用扫描电镜、透射电镜、红外光谱和振动磁强计对材料进行了表征.结果表明成功地制备了核壳结构的Fe_3O_4@C复合材料.用甲基绿来考察Fe_3O_4@C的吸附性能.研究表明,溶液pH对甲基绿的吸附有显著的影响,随溶液pH的升高,甲基绿的吸附容量显著增大.用朗格缪尔吸附等温模型拟合出在纯水、湖水和自来水中Fe_3O_4@C对甲基绿的最大吸附容量分别为490.1、442.5和389.1 mg·g~(-1).热力学研究计算出吸附的吉布斯自由能为负值,说明吸附是自发过程.动力学研究表明甲基绿在Fe_3O_4@C上的吸附过程符合拟二级反应动力学方程,吸附速率较快.