火焰原子吸收光谱法测定大气降尘中的几种重金属

本文介绍了大气降尘中铜、铅、锌、镉、铁、锰、镍、钴八种重金属的分析方法，以及共存离子对上述重金属测试时的干扰及其抑制干扰的方法。并提出了表示大气降尘中重金属量的三种浓度概念即容量浓度、重量浓度及降金属量的不同物理意义。     

Numerical Simulation of Interaction of the Heavy Gas Cloud with the Atmospheric Surface Layer

The numerical time-dependent three-dimensional model [Kovalets, I.V. and Maderich, V.S.: 2001, Int. J. Fluid Mech. Res. 30, 410–429] of the heavy gas dispersion in the atmospheric boundary layer has been improved by parameterizing momentum and heat fluxes on the surface of Earth using Monin–Obukhov similarity theory. Three parameterizations of heat exchange with the surface of Earth were considered: (A) formula of Yaglom A.M. and Kader B.A. [1974, J. Fluid Mech. 62, 601–623] for forced convection, (B) interpolation formula for mixed convection and (C) similarity relationship for mixed convection [Kader, B.A. and Yaglom, A.M.: 1990, J. Fluid Mech. 212, 637–662]. Two case studies were considered. In the first study based on experiment of Zhu et al., J. Hazard Mater 62, 161–186], the interaction of an isothermal heavy gas plume with an atmospheric surface layer was simulated. It was found that stable stratification in the cloud essentially suppresses the turbulence in the plume, reducing the turbulent momentum flux by a factor of down to 1/5 in comparison with the undisturbed value. This reduction essentially influences velocities in the atmospheric boundary layer above the cloud, increasing the mean velocity by a factor of up to 1.3 in comparison with the undisturbed value. A simulation of cold heavy gas dispersion was carried out in the second case based on field experiment BURRO 8. It was shown that both forced and free convections under moderate wind speeds significantly influence the plume. The relative rms and bias errors of prediction the plume’s height were σ_H ≈ 30% and ɛ_H = − 10%, respectively, for parameterization B, while for A and C the errors were σ_H ≈ 80% and ɛ_H ≈ − 65%. It is therefore advised to use the simple parameterization B in dense gas dispersion models.     

Size distribution in ultraphytoplankton: A comparative analysis of counting methods

Water samples taken at three depth layers from the offshore oligotrophic Cretan Sea were analyzed for ultraphytoplankton size fractionation using different methods: (a) sequential filtration on filters of pore size 5, 1 and 0.2 m, (b) separate filtration using filters 5 and 0.2 m as well as 1 and 0.2 m and (c) direct filtration on 0.2 m filters after staining of the samples with DAPI. Total abundance of photosynthetic organisms as well as the abundance of different groups such as flagellates and cyanobacteria measured by means of sizing after DAPI staining were significantly higher than those obtained by the other methods. This indicates that although there were no significant differences between the estimates provided by the separate and sequential filtration, both these methods underestimated total abundance by at least 25–50%. The estimates for the size fractions were also found to range from relatively imprecise to completely unreliable depending on the group and the size range. Although size fractionation through direct observation after staining largely depends on the expertise of the observer, this study suggests that it may provide more informative estimates than the other two methods. Although it is difficult to generalize the results of this study in a global context, the paper provides strong indications on the limitations of the sequential and separate methods for size fractionation of photosynthetic organisms and implies that their results are likely to be less accurate than is presently believed.     

A Comparison of Three Methods to Collect Submerged Aquatic Vegetation in a Shallow Lake

Two boat-based and one in-water sampling method have been used to collect submerged aquatic vegetation (SAV) as part of a long-term monitoring program in Lake Okeechobee, Florida, USA. The boat-based methods consisted of collecting SAV with a ponar dredge, used only to collect Chara, and an oyster tongs-like rake apparatus, used to collect all SAV. The in-water method involved use of a 0.5 m² PVC quadrat frame deployed by a diver. During summer 2002, SAV biomass samples were collected using all three methods at various sites in the lake to compare between-methods sampling precision. Sites used for these comparisons were selected based on plant type, plant density and sediment type. Statistical comparisons indicated that there were significant (p ≤ 0.05) biomass differences in 8 of 15 possible pairwise comparisons between sampling method biomass means. In four of the eight comparisons, significantly higher biomass mean values were obtained using the quadrat frame. In three of the remaining four comparisons, significantly higher biomass mean values were obtained with the rake apparatus. For the fourth comparison, a significantly higher biomass mean value was obtained with the ponar dredge. Three of the four relationships between SAV biomass collected by the rake and the quadrat and the rake and the quadrat/ponar dredge were statistically significant, linear and explained between 67 and 78% of the biomass variability. There were no significant differences between regression coefficients or elevations for these relationships, therefore these regressions estimated the same population regression. The population regression coefficient was 0.95, suggesting that the quadrat and ponar over-sampled relative to the rake, but the amount of this over-sampling was very small. Since there was no consistent pattern in the sampling method which yielded the significantly different biomass values and there were no significant differences in sampling precision across a range of plant species, plant densities and two sediment types, the boat-based rake method appears to be a suitable replacement for the previously used ponar dredge and quadrat methods, when in-lake measurements are not practical.     

Informing global environmental policy‐making: A plea for new methods of assessment and synthesis

Practice and research in assessment of global environmental change are dominated by two conventional assessment methods, formal models and expert panels. Models construct a representation of biophysical and socioeconomic components of a policy issue, to project future trends or consequences of interventions. Panels articulate consensus views of policyrelevant knowledge through deliberations among selected experts. These methods make valuable contributions, but are weak in addressing certain kinds of knowledge needs that are typical of globalchange issues. To address these needs, a set of novel assessment methods is proposed that combine elements of representation and deliberation. These methods, of which policy exercises, simulationgaming, and scenario exercises are examples, involve human participants in structured relevant decision and task settings. Relative to models and panels, these methods can more readily incorporate diverse perspectives, can integrate across broader collections of knowledge domains, and can both encourage creative insights and innovations, and provide tests of their relevance and practicality. Risks of bias, and of overconfident generalization from unique experiences, are effectively mitigated by critical debriefings, and appear no more severe than corresponding risks in conventional assessment methods, or in policymakers generalizations from historical experience. While serious development and implementation challenges remain, early experience suggests that these methods can offer useful ideas and insights for policymaking that are not available through other means.     

原料和制炭方式对生物炭吸附抗生素的影响

为研究原料和制炭方法对生物炭吸附抗生素性能的影响,选取芦苇、棉杆和竹柳,经限氧和曝氧法制备得到生物炭,研究其对土霉素（OTC）和磺胺甲恶唑（SMX）的吸附性能及其吸附机理.研究发现：物源特征和制炭方法共同决定了生物炭对抗生素的吸附功效.芦苇和棉秆宜采用限氧法制备成炭,竹柳宜采用曝氧法制备成炭;整体上以曝氧竹柳炭对抗生素的吸附性能最优,单一浓度（50mg/L）下,其对OTC和SMX的吸附量分别为11.98和10.12mg/g.批吸附实验和傅里叶变换红外光谱分析表明,π-π EDA相互作用是竹柳炭吸附抗生素的主要机理.静电吸引有助于高pH值下曝氧竹柳炭对OTC的吸附,而孔隙填充可能对曝氧竹柳炭吸附SMX起到促进作用.曝氧竹柳炭对抗生素的吸附性能优于其他炭品,是去除水体抗生素的优选材料.     

冷热联用对市政脱水污泥低温干燥的影响

为探究冷热联用干燥市政脱水污泥的可行性,明确冷冻对市政脱水污泥低温干燥的影响,以市政脱水污泥为试验材料,利用扫描电镜（SEM）及流式细胞仪研究了冷冻对污泥的作用.考察了不同冷冻温度和冷冻时间对脱水污泥干燥特性的影响,并对不同含水率和厚度的脱水污泥冷热联用低温干燥效果进行了分析.结果表明：冷冻使污泥的内部微小孔隙增多.当冷冻温度降到-30℃时,细胞死亡率达到15.5%,是未冷冻时的9.7倍.当干燥温度为60℃,冷冻温度分别为-10℃、-20℃和-30℃时,脱水污泥完成干燥的时间分别缩短了25.0%、33.3%和29.2%.质量为5g±0.1g,厚度为3mm,直径为50mm的污泥样品冷冻6h后达到最大强化效果.污泥含水率的下降会导致强化效果减弱,当含水率降至45%时强化效果消失.增加泥饼厚度使强化效果小幅下降,5mm、10mm和15mm厚的泥饼强化效果分别为33.3%、31.3%和30.4%.     

预曝气及提取方法对活性污泥胞外聚合物的影响

为了获得更高的胞外聚合物质（EPS）得率及其对污染物的去除效果,比较了活性污泥预曝气时间及2种提取方法（超声法和甲醛+NaOH法）对提取EPS的影响,分析了EPS的荧光组分以及与污染物去除有关的基团差异.结果表明,污泥经过4h预曝气,EPS得率最高;甲醛+NaOH法提取的EPS是超声法的1.5~1.7倍;其中蛋白质、多糖、DNA含量分别是后者的1.4~1.7、0.8~2和2.3~2.7倍.甲醛+NaOH提取法获得的EPS对高岭土的絮凝率和对Cr³⁺的去除率分别高出超声法16%和33%,絮凝率和去除率分别达到了65%和63%.三维荧光光谱分析结果表明,甲醛+NaOH法提取的EPS中芳香蛋白和溶解性微生物代谢产物含量分别是超声法的1.4~1.9倍和1.8~2.4倍;胡敏酸类物质仅大量存在于甲醛+NaOH法提取的EPS中,且腐殖质与Cr³⁺去除率呈显著相关（P<0.01,R²=0.920）.红外光谱分析表明,甲醛+NaOH法提取的EPS中有区别于超声法的特殊基团,其中-OH、-COOH、-NH₂等基团与Cr³⁺发生了配位络合作用.