The enhanced oxidation of SO2 by NO2 on carbon particulates

The oxidation of SO₂ on carbon particles in dry air and in air at 65% relative humidity (RH) was found to be greatly enhanced by the presence of gaseous NO₂. Exposures of 20–80 ppm SO₂ + 10 ppm NO₂ on 1 mg samples of commercial carbon black were found to produce both sorption and desorption coverages (weight retained after desorption into N₂) of over one order of magnitude greater than for corresponding SO₂ exposures. Significant agglomeration and wetting were observed to occur progressively during exposures at 65% RH and samples, even after 150 h exposure, rarely reached steady-state weight gain. The wetting may have regenerated fresh reactive carbon surface. Sorptions conducted in nitrogen atmospheres, rather than in air, appeared to produce slightly higher sorptions and weight retentions for equivalent exposure concentrations and times, indicating that NO₂ served as the oxidizer and that molecular oxygen, or some trace constituents in air, may have weakly inhibited the oxidation by NO₂. Wet chemical analysis of the desorbed phase indicated that sulfate, presumably H₂SO₄, accounted for over half of the retained weight. Measurements of pH from water-quenched samples indicated a highly acidic surface phase and suggested the oxidation process could process in an acidic environment.     

灰霾天气与大气颗粒物的相关性研究综述

随着城市化进程的迅速发展,城市大气污染加剧,灰霾天气也随之增多。综述了灰霾天气期间大气颗粒物在时空分布和污染水平2方面的污染特征,分析了大气颗粒物与能见度相关性,介绍了国内外对灰霾天气期间大气污染物的组成及源解析方面的研究进展,并提出了今后灰霾天气的研究方向。     

Effects of driving conditions on diesel exhaust particulates

Four driving conditions were examined to characterize how speeds and loads of a medium-duty diesel engine affect resultant diesel exhaust particulates (DEPs) in terms of number concentrations (< or =400 nm), size distribution, persistent free radicals, elemental carbon (EC), and organic carbon (OC). At the medium engine load (60%), DEPs surged in number concentrations at around 40-70 nm, whereas DEPs from the full engine load (100%) showed a distinctive bimodal distribution with a large population of 30-50 nm and 100-400 nm. Under the full engine load, engine speeds insignificantly affected resultant DEP number concentrations. When the engine load decreased from 100% to the medium level (60%), DEPs of ultrafine size and 100-400 nm decreased at least 1.4 times (from 5.6 x 10(8) to 4 x 10(8) #/cm3) and more than 3 times (from 2.7 x 10(8) to 0.8 x 10(8) #/cm3), respectively. The same reduction in the engine load significantly decreased persistent free radicals in DEPs up to approximately 30 times (from 123 x 10(16) to 4 x 10(16) #spin/g). Decreasing the engine load from 100 to 60% also concurrently reduced both EC and OC in total DEPs around 2 times, from 27.3 to 13.9 mg/m3, and from 17.6 to 9.2 mg/m3, respectively. For DEPs smaller than 1 microm, under the full engine load, EC and OC consistently peaked at 170-330 nm under an engine speed of 1800 rpm or 94-170 nm under an engine speed of 3000 rpm, reflecting processes of nucleation, cluster-cluster agglomeration, and condensation. Decreasing the engine load from 100 to 60% reduced EC and OC in DEPs (smaller than 1 microm) at least 3 times (0.6 to 0.2 mg/m3) and 2 times (0.4 to 0.2 mg/m3), respectively. Taken together, decreasing the full engine load to a medium (60%) level effectively reduced the number concentrations (< or =400 nm), persistent free radicals, EC, and OC of total DEPs, as well as the concentration of EC and OC in ultrafine and accumulation-mode DEPs.     

超声波对污泥中SCFAs释放影响及作用效应研究

以剩余污泥为研究对象,考察了超声波处理过程中超声时间及声能密度对污泥中短链脂肪酸SCFAs释放的影响及其作用效应。实验结果表明,污泥中SCFAs的释放量随超声时间和声能密度的提高而提高,但当超声能量>270 J/mg MLSS后, SCFAs释放变缓甚至下降;在相同能耗下,长超声时间、低声能密度的超声波处理条件更有利于污泥SCFAs的释放,超声时间影响更显著;污泥中释放的SCFAs以乙酸及丙酸为主。在超声波释放剩余污泥SCFAs过程中自由基效应及热效应皆不显著,机械效应起最主要作用。     

Investigation of the atmospheric particulates deposited on leaves using instrumental neutron activation analysis

A method for the separation of surface contamination on plant leaves by plastic film stripping was applied. The particulate matter embedded in the film was analysed by neutron activation.The investigation was directed especially towards the determination of the trace element content of the suitable plastic matrices and of the influence of solvents.The practicability of this method is demonstrated by analysing films stripped from plant leaves with different degrees of pollution.     

Effect of typhoon on atmospheric particulates in autumn in central Taiwan

Previous studies have suggested that the ongoing global climate change will likely increase the intensity and frequency of extreme weather, such as typhoons. Since the beginning of global warming, it has become necessary to understand the influence of typhoons on air quality. Rare data, especially particulate measurements data could be used to establish the relationship between the air pollution and typhoons. One of main limiting factors is that most of the previous chemical analyses of particulates used a relatively long sampling time, which could dilute the temporal impact of particulate characteristics and their sources. This work, depending more time-resolved measurements, focus on the characteristics and sources of high particulate matter levels and the influence of typhoons and the Pacific high system. Depending on the measurements, two pollutant groups were clearly identified in this work. The first pollutant group was the emissions from neighboring riverbeds under the strong circulation of the typhoon in the driest season and characterized as high coarse particle concentrations with high mass fraction of Ca²⁺. The second pollutant group was characterized as the formation and transport of secondary particles with prevalent ions of NH₄⁺, NO₃^?, and SO₄^2? and occurred in the sea-land breeze circulation under the influence the Pacific high system.     

Fast preparation of the seawater accommodated fraction of heavy fuel oil by sonication

The seawater accommodated fraction (SWAF) of oil is widely used for the assessment of its toxicity. However, its preparation in the laboratory is time consuming, and results from different authors are difficult to compare as preparation methods vary. Here we describe a simple and fast set up, using sonication, to produce reproducible SWAF in the laboratory. The system was tested on heavy fuel oil placed on seawater at different salinity and temperature conditions. Maximum dissolution of the oil was achieved after 24 h, independently of both seawater salinity and temperature. Our findings are discussed in relation to the fate of the oil from the deep spill of the Prestige tanker. Changes in temperature in the open ocean are bound to have larger impact in the concentration of the SWAF than the corresponding values of sea water salinity. We anticipate that in this type of incident the highest SWAF, as the oil reaches the sea surface, should be expected in the warmest and less saline waters of the water column.     

Fast preparation of the seawater accommodated fraction of heavy fuel oil by sonication

The seawater accommodated fraction (SWAF) of oil is widely used for the assessment of its toxicity. However, its preparation in the laboratory is time consuming, and results from different authors are difficult to compare as preparation methods vary. Here we describe a simple and fast set up, using sonication, to produce reproducible SWAF in the laboratory. The system was tested on heavy fuel oil placed on seawater at different salinity and temperature conditions. Maximum dissolution of the oil was achieved after 24 h, independently of both seawater salinity and temperature. Our findings are discussed in relation to the fate of the oil from the deep spill of the Prestige tanker. Changes in temperature in the open ocean are bound to have larger impact in the concentration of the SWAF than the corresponding values of sea water salinity. We anticipate that in this type of incident the highest SWAF, as the oil reaches the sea surface, should be expected in the warmest and less saline waters of the water column.     

浙东沿海城市大气颗粒物污染特征及来源解析研究

对2009年夏季浙东沿海地区环境空气质量进行监测,监测大气颗粒物(TSP、PM10、PM2.5、PM1.0)浓度,分析颗粒物污染特征、水溶性离子及无机元素组成,运用化学质量平衡受体模型(CMB模型)对浙东沿海地区大气TSP来源进行解析.结果表明,浙东沿海地区的大气颗粒物主要以细颗粒物为主,颗粒物中主要的水溶性离子为SO2-4、NH+4、Ca2+,土壤尘是该地区大气TSP的主要来源,北仑、乐清和奉化TSP中土壤尘的分担率分别达到55.49%、42.52%、40.70%,各监测点TSP来源具有一定的地域特征.     

Influence of African dust on the levels of atmospheric particulates in the Canary Islands air quality network

Time series of levels of atmospheric particulate matter (TSP and PM10) were studied at 19 air quality monitoring stations in the islands of Tenerife and Gran Canaria (Canary Islands) during the period 1998–2000. After analysing seasonal variations, attention was focused on the detection of high TSP and PM10 events and on the identification of their natural or anthropogenic origins. Back-trajectory analysis and TOMS-NASA aerosol index as well as satellite imagery (SeaWIFS-NASA) were used to identify three types of African dust outbreaks differing in seasonal occurrence, source origin and impact on TSP/PM10 levels. Mean annual and daily TSP and PM10 levels were compared with the forthcoming limit values of the EU Air Quality Directive EC/30/1999, and the results showed that the annual and daily limit values established for 2010 would only be met at rural stations. PM levels at urban background, urban and industrial sites would exceed the 2010 objectives. Only the levels at the urban-background stations would meet the requirements for 2005 despite the fact that the trade winds result in lower levels of atmospheric pollutants in the Canary Islands than in continental environments. The results highlight the role of African dust contributions when implementing the limit values of the EU directive.     

The uptake of particulates by an urban woodland: site description and particulate composition

Woodlands may improve local air quality by increasing the uptake rates of gaseous, particulate and aerosol pollutants from the atmosphere and can also act as relatively permanent sinks for some pollutants. Rough Wood, Walsall was selected for a study of the material which accumulates on tree foliage because of its location in a densely populated urban area, and its proximity to a motorway with high traffic flow (the M6) and to other pollutant sources. Methods were developed for leaf washing to allow determination of the quantity of dust and the identification of the dust particles present on oak leaves. Elemental analysis of particles was also undertaken using scanning electron microscopy coupled with electron probe microanalysis. A large proportion of particles were organic in origin. Of the inorganic particles, the majority contained silicon and aluminium in varying proportions suggesting that they were soil derived. Some particles were clearly identified as the products of combustion, and sea or road salt was present on leaf surfaces. Some particles contained copper, tin and titanium which may reflect the proximity of Rough Wood to local metal workings. The number of particles counted on leaf surfaces decreased as distance from the motorway increased.     

The aqueous sulfite-nitrite system: Investigations on the mutagenicity of some known products

Some known reaction products of the two commonly used food additives, sulfite and nitrite, were examined for mutagenicity using the Salmonella/mammalian-microsome test. Potassium nitrosodisulfonate, potassium aminetrisulfonate and potassium hydroxylaminemonosulfonate were not mutagenic over a dose range of 0.01 – 10 mg/plate in the strains his G 46, TA 100 and TA 98. Potassium hydroxylaminedisulfonate showed a weak mutagenic activity in his G 46 and TA 100 with microsomal activation. Hydroxylamine-O-sulfonic acid was only weakly mutagenic in the excision-repair proficient strain his G 46 in the presence of S9.     

Assessment of particulates in the urban atmosphere of Sao Carlos, Brazil

A survey on the concentration of particulate matter in the urban atmosphere was carried out in the city of Sao Carlos, Brazil. Five sites were selected for data collection one in the city centre (high concentration of people and automotive vehicles), three in industrial areas, and one at the interface with the countryside. The particle size distribution and mass concentration, temperature, humidity and wind velocity were measured at each site. In the city centre, the concentration of the particles smaller than 10 μm (PM₁₀) was also measured. The particle size distribution was obtained with a laser scattering particle counter. The total and PM₁₀ concentrations were obtained with high volume samplers. The tests were performed for 75 consecutive weeks. The results show that the particle concentration is sensitive to seasonal conditions. During autumn and winter, which is the drier and windy period of the year, larger particles were dispersed, leading to higher concentrations, both total and PM₁₀. The relative humidity varied with the schedule of sampling and with the season the autumn and winter weeks were much drier than the other periods. Higher rainfall levels coincided with lower particle concentrations. All these results are statistically significant.     

Influence of alkaline particulates on pH of cloud and rain water in India

Cloud and rain water samples were collected on board aircraft by specially designed equipment, during three monsoon seasons, 1983, 1984 and 1985 in the Pune region in India. The samples were analyzed for major ionic components and pH, and the concentrations of all the ionic components were found to be significantly higher (35–161%) in cloud water than in rain water. In cloud water Cl contributed most (35%) to the total ionic concentration followed by Ca(21%) and Na(17%). Sulphate and nitrate concentrations, on the average, were low and were found to account for only 6% of the total ionic concentration. pH of cloud water and rain water was substantially higher than that of the CO₂-equilibrated value (5.6). The findings suggest that influence of anthropogenic sources is negligible and that of soil dust which is alkaline is substantial on the pH and chemistry of cloud/rain water in India.     

柴油车尾气碳烟颗粒物催化燃烧催化剂的最新研究进展

柴油车尾气排放的碳烟颗粒已经引起了严重的环境污染问题,必须加以净化处理.柴油车碳烟颗粒的低温燃烧离不开高活性的催化剂.针对柴油车排放的碳烟颗粒物后处理方法中的催化氧化技术,总结了近年来几种主要类型的碳烟燃烧催化剂(贵金属催化剂、碱金属催化剂、单组分过渡金属氧化物催化剂、多组分混合氧化物催化剂和固定结构复合氧化物催化剂)的最新研究进展,并对该研究方向存在的主要问题和应用前景进行了探讨.