高温烟气除尘滤料过滤性能检测及对比分析

对3大类不同过滤方式的高温烟气除尘滤料的压力损失、过滤速度、分级效率等性能指标进行测试对比分析,得到滤料在清洁和集尘条件下压力损失随过滤时间、粉尘负荷的变化规律.从过滤机理综合分析,集尘滤料的过滤分级效率明显高于清洁滤料过滤效率,为滤料选用提供理论依据.     

Modelling of moisture-dependent aerobic degradation of solid waste

In landfill, high temperature levels come from aerobic reactions inside the waste surface layer. They are known to make anaerobic processes more reliable, by partial removal of easily biodegradable substrates. Aerobic biodegradation of the main components of biodegradable matter (paper and cardboard waste, food and yard waste) is considered. In this paper, two models which take into account the effect of moisture on aerobic biodegradation kinetics are discussed. The first one (Model A) is a simple, first order, substrate-related model, which assumes that substrate hydrolysis is the limiting step of the process. The second one (Model B) is a biomass-dependant model, considering biological growth processes. Respirometric experiments were performed in order to evaluate the efficiency of each model. The biological oxygen demands of shredded paper and cardboard samples and of food and yard waste samples prepared at various initial water contents were measured. These experimental data were used to identify model parameters. Model A, which includes moisture dependency on the maximum amount of biodegraded matter, is relevant for paper and cardboard biodegradation. On the other hand, Model B, including moisture effect on the growth rate of biomass is suitable to describe food and yard waste biodegradation.     

Adsorption-desorption characteristics of mercury in paddy soils of China

Mercury (Hg) has received considerable attention because of its association with various human health problems. Adsorption-desorption behavior of Hg at contaminated levels in two paddy soils was investigated. The two representative soils for rice production in China, locally referred to as a yellowish red soil (YRS) and silty loam soil (SLS) and classified as Gleyi-Stagnic Anthrosols in FAO/UNESCO nomenclature, were respectively collected from Jiaxin County and Xiasha District of Hangzhou City, Zhejiang Province. The YRS adsorbed more Hg(2+) than the SLS. The characteristics of Hg adsorption could be described by the simple Langmuir adsorption equation (r2 = 0.999 and 0.999, P < 0.01, respectively, for the SLS and YRS). The maximum adsorption values (Xm) that were obtained from the simple Langmuir model were 111 and 213 mg Hg(2+) kg(-1) soil, respectively, for the SLS and YRS. Adsorption of Hg(2+) decreased soil pH by 0.75 unit for the SLS soil and 0.91 unit for the YRS soil at the highest loading. The distribution coefficient (kd) of Hg in the soil decreased exponentially with increasing Hg(2+) loading. After five successive desorptions with 0.01 mol L(-1) KCl solution (pH 5.4), 0 to 24.4% of the total adsorbed Hg(2+) in the SLS soil was desorbed and the corresponding value of the YRS soil was 0 to 14.4%, indicating that the SLS soil had a lower affinity for Hg(2+) than the YRS soil at the same Hg(2+) loading. Different mechanisms are likely involved in Hg(2+) adsorption-desorption at different levels of Hg(2+) loading and between the two soils.     

Analysis of biomagnification of persistent organic pollutants in the aquatic food web of the Mekong Delta, South Vietnam using stable carbon and nitrogen isotopes

The present study elucidated the biomagnification profiles of persistent organic pollutants (POPs) through a tropical aquatic food web of Vietnam based on trophic characterization using stable nitrogen analysis. Various biological samples collected from the main stream of the Mekong Delta were provided for the analysis for both POPs, and stable nitrogen and carbon isotope ratios. Of the POPs analyzed, dichlorodiphenyltrichloroethane and its metabolites (DDTs) were the predominant contaminants with concentrations ranging from 0.058 to 12 ng/g wet weight, followed by polychlorinated biphenyls (PCBs) at 0.017-8.9 ng/g, chlordane compounds (CHLs) at 0.0043-0.76 ng/g, tris-4-chlorophenyl methane (TCPMe) at N.D.-0.26 ng/g, hexachlorocyclohexane isomers (HCHs) at N.D.-0.20 ng/g and hexachlorobenzene (HCB) at 0.0021-0.096 ng/g. Significant positive increases of concentrations in DDTs, CHLs, and TCPMe against the stable nitrogen ratio (delta(15)N) were detected, while, concentrations of HCHs and HCB showed no significant increase. The slopes of the regression equations between the log-transformed concentrations of these POPs and delta(15)N were used as indices of biomagnification. The slopes of the POPs for which positive biomagnification was detected ranged from 0.149 to 0.177 on a wet weight basis. The slopes of DDTs and CHLs were less than those reported for a marine food web of the Arctic Ocean, indicating that less biomagnification had occurred in the tropical food web. Of the isomers of CHLs, unlike the studies of the Arctic Ocean, oxychlordane did not undergo significant biomagnification through the food web of the Mekong Delta. This difference is considered to be due to a lack of marine mammals, which might metabolize cis- and trans-chlordane to oxychlordane, in the Mekong Delta ecosystem. The biomagnification profile of TCPMe is reported for the first time in the present study.     

A directional passive air sampler for monitoring polycyclic aromatic hydrocarbons (PAHs) in air mass

A passive air sampler was developed for collecting polycyclic aromatic hydrocarbons (PAHs) in air mass from various directions. The airflow velocity within the sampler was assessed for its responses to ambient wind speed and direction. The sampler was examined for trapped particles, evaluated quantitatively for influence of airflow velocity and temperature on PAH uptake, examined for PAH uptake kinetics, calibrated against active sampling, and finally tested in the field. The airflow volume passing the sampler was linearly proportional to ambient wind speed and sensitive to wind direction. The uptake rate for an individual PAH was a function of airflow velocity, temperature and the octanol-air partitioning coefficient of the PAH. For all PAHs with more than two rings, the passive sampler operated in a linear uptake phase for three weeks. Different PAH concentrations were obtained in air masses from different directions in the field test.     

Characterizing effects of uncertainties in MSW composting process through a coupled fuzzy vertex and factorial-analysis approach

A coupled fuzzy vertex and factorial-analysis approach was developed in this study for systematically characterizing effects of uncertainties in a municipal solid waste composting process. A comprehensive composting process model was also embedded into the system framework and used to address substrate decomposition and biomass growth, as well as the interactions between moisture contents, temperatures, and oxygen concentrations. The applicability of the proposed method was verified through a custom-made pilot-scale composting system. Results from fuzzy simulation indicated that the fuzzy vertex method could effectively communicate implicit knowledge into dynamic simulations and thus provide valuable information for enhancing composting process control under uncertainty. The factorial analysis was effective in quantifying the proportion to which the uncertainty of each single or interactive effect of model parameters contributes to the overall uncertainty of the system outcomes. Thus, sensitive parameters that may lead to errors or unreasonable predictions can be determined. The proposed study system could not only be used in characterizing combined effects of uncertainties for composting processes, but was also applicable to many other environmental modelling systems.     

Organic pollutants in compost and digestate. Part 1. Polychlorinated biphenyls, polycyclic aromatic hydrocarbons and molecular markers

In Europe, 9.3 x 10(6) t(dry weight (dw)) of compost and digestate are produced per year. Most of this is applied to agricultural land, which can lead to considerable inputs of organic pollutants, such as polychlorinated biphenyls (PCB) and polycyclic aromatic hydrocarbons (PAH) to soil. This paper presents an inventory of the pollutant situation in source-separated composts, digestates and presswater in Switzerland by a detailed analysis of over 70 samples. PCB concentrations ( summation PCB 28, 52, 101, 118, 138, 153, 180) were significantly higher in urban (median: 30 microg kg(-1)dw, n = 52) than in rural samples (median: 14 microg kg(-1)dw, n = 16). Together with low concentrations in general, this points to aerial deposition on compost input material as the major contamination pathway. Enantiomeric fractions of atropisometric PCB were close to racemic. Median PAH concentration was 3010 microg kg(-1)dw( summation 15PAH, n = 69), and one quarter of the samples exhibited concentrations above the relevant Swiss guide value for compost (4000 microg kg(-1)dw). The levels were influenced by the treatment process (digestate > compost), the season of input material collection (spring-summer > winter > autumn), the particle size (coarse-grained > fine-grained), and maturity (mature > less mature). The main source of PAH in compost was pyrogenic, probably influenced mainly by liquid fossil fuel combustion and some asphalt abrasion, as suggested by multiple linear regression. This study, together with a companion paper reporting on other organic contaminates including emerging compound classes, provides a starting point for a better risk-benefit estimation of the application of compost and digestate to agricultural soil in Switzerland.     

谷氨酰胺转胺酶(MTG)分批发酵中温度对S.mobaraense生长及产酶影响的模型化

研究了2.5L小罐培养过程中控制温度为25℃～35℃时对细胞生长和MTG合成的影响.结果表明当控制相对较低的温度时,细胞生长的延滞期较长,当控制温度较高时,细胞生长的延滞期较短,达到最大DCW和最高MTG酶活的时间均较短;通过研究各种不同模型对细胞生长的影响得到最适合描述S.mobaraense生长与温度之间的关系方程为Schoolfield方程;通过对最大DCW和最大MTG酶活进行数学模拟,发现方程X(U)=-a     

中小企业化学品职业危害预防控制指南

为了帮助中小企业控制预防控制化学品职业危害,本文详细介绍了国际劳工组织所推行的中小企业化学品职业危害控制指南,包括化学职业卫生管理的主要内容和基本步骤,关键点危险区的确定方法,改进化学品职业危害管理、实施化学品管理的良好规范、制定化学品管理行动计划和编制全面的化学品清单等方法,以达到系统提高化学品管理水平和持续改进的目标和要求.     

稻鸭萍共作复合系统的主要生态效应

对稻鸭萍共作体系的主要生态效应研究结果表明,稻鸭萍共作有利于提高土壤肥力,水稻收获后的土壤有机质、碱解氮、速效磷、速效钾分别比对照增加7.95%、7.05%、6.47%和4.46%;稻鸭萍共作对杂草的控制效果达到98.94%,明显削弱了稻田优势杂草的发生与危害,稻田残存杂草为数甚少,P ielou均匀度指数显著提高;稻鸭萍共作对稻田飞虱有显著的控制效应,从而明显抑制主要由灰飞虱传毒危害的水稻条纹叶枯病的发病率;稻鸭萍共作虽然对水稻纹枯病也有明显防治效果,但不能阻止纹枯病的发生;由于绿萍吸附了稻田水体中部分有机物、腐殖质等,稻鸭萍共作区水体的化学需氧量比稻鸭共作区降低8.70%。