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1.
The diffusion coefficient (D
m) and material/air partition coefficient (K) are two key parameters characterizing the formaldehyde and volatile organic compounds (VOC) sorption behavior in building materials. By virtue of the sorption process in airtight chamber, this paper proposes a novel method to measure the two key parameters, as well as the convective mass transfer coefficient (h
m). Compared to traditional methods, it has the following merits: (1) the K, D
m and h
m can be simultaneously obtained, thus is convenient to use; (2) it is time-saving, just one sorption process in airtight chamber is required; (3) the determination of h
m is based on the formaldehyde and VOC concentration data in the test chamber rather than the generally used empirical correlations obtained from the heat and mass transfer analogy, thus is more accurate and can be regarded as a significant improvement. The present method is applied to measure the three parameters by treating the experimental data in the literature, and good results are obtained, which validates the effectiveness of the method. Our new method also provides a potential pathway for measuring h
m of semi-volatile organic compounds (SVOC) by using that of VOC. 相似文献
2.
Ozone gas (O(3)) is a reactive oxidizing agent with biocidal properties. Because of the current phasing out of methyl bromide, investigations on the use of ozone gas as a soil-fumigant were conducted. Ozone gas was produced at a concentration of 1% in air by a conventional electrical discharge O(3) generator. Two O(3) dosages and three gas flow rates were tested on a sandy loam soil collected from a tomato field that had a resident population of root knot nematodes, Meloidogyne javanica. At dosages equivalent to 50 and 250 kg of O(3)/ha, M. javanica were reduced by 24% and 68%, and free-living nematodes by 19% and 52%, respectively. The reduction for both M. javanica and free-living nematodes was dosage dependent and flow rate independent. The rates of O(3) mass transfer (OMT) through three soils of different texture were greater at low and high moisture levels than at intermediate ones. At any one soil moisture level, the OMT rate varied with soil texture and soil organic matter content. Results suggest that soil texture, moisture, and organic matter content should be considered in determining O(3) dosage needed for effective nematode control. 相似文献
3.
This study investigated characteristics of a sequencing batch reactor (SBR) system which was varied with respect to sludge retention time (SRT) (5.9, 8.2, 10.5, 12.2, and 16.2 days). The removal efficiencies of chemical oxygen demand (COD) were more than 90% under all SRT conditions, and the greatest efficiency (92.2%) occurred with a SRT of 16.2 days. As the SRT increased, the denitrification rate per mixed liquor suspended solids (MLSS) during the anoxic(I) period decreased significantly from 166.3 mg NO(X)(-)-N/g MLSS d to 68.8 mg NO(X)(-)-N/g MLSS d. As the SRT increased, the phosphorus removal efficiency decreased from 47.1% (SRT of 5.9 days) to 31.0% for a SRT of 16.2 days, because active phosphate release and uptake occurred under shorter SRT conditions. The mass balance of nitrogen (with respect to nitrogen in the influent) at a SRT of 16.2 days (the highest nitrogen removal efficiency) showed 14.9% of nitrogen was removed in clarified water effluent, 49.7% was removed by the sludge waste process and 33.3% was removed by denitrification. Nitrogen processing was well accounted for in the SBR system as the nitrogen mass balance was close to 100% (97.9%). 相似文献
4.
Carbon isotope discrimination in leaves of the broad‐leaved paperbark tree,Melaleuca quinquenervia,as a tool for quantifying past tropical and subtropical rainfall
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John Tibby Cameron Barr Francesca A. McInerney Andrew C. G. Henderson Melanie J. Leng Margaret Greenway Jonathan C. Marshall Glenn B. McGregor Jonathan J. Tyler Vivienne McNeil 《Global Change Biology》2016,22(10):3474-3486
Quantitative reconstructions of terrestrial climate are highly sought after but rare, particularly in Australia. Carbon isotope discrimination in plant leaves (Δleaf) is an established indicator of past hydroclimate because the fractionation of carbon isotopes during photosynthesis is strongly influenced by water stress. Leaves of the evergreen tree Melaleuca quinquenervia have been recovered from the sediments of some perched lakes on North Stradbroke and Fraser Islands, south‐east Queensland, eastern Australia. Here, we examine the potential for using M. quinquenervia ?leaf as a tracer of past rainfall by analysing carbon isotope ratios (δ13C) of modern leaves. We firstly assess Δleaf variation at the leaf and stand scale and find no systematic pattern within leaves or between leaves due to their position on the tree. We then examine the relationships between climate and Δleaf for a 11‐year time series of leaves collected in a litter tray. M. quinquenervia retains its leaves for 1–4 years; thus, cumulative average climate data are used. There is a significant relationship between annual mean ?leaf and mean annual rainfall of the hydrological year for 1–4 years (i.e. 365–1460 days) prior to leaf fall (r2 = 0.64, P = 0.003, n = 11). This relationship is marginally improved by accounting for the effect of pCO2 on discrimination (r2 = 0.67, P = 0.002, n = 11). The correlation between rainfall and Δleaf, and the natural distribution of Melaleuca quinquenervia around wetlands of eastern Australia, Papua New Guinea and New Caledonia offers significant potential to infer past rainfall on a wide range of spatial and temporal scales. 相似文献
5.
Helen E. Jesse Tacita L. Nye Samantha McLean Jeffrey Green Brian E. Mann Robert K. Poole 《Biochimica et Biophysica Acta - Proteins and Proteomics》2013,1834(9):1693-1703
Background: CO-releasing molecules (CO-RMs) are potential therapeutic agents, able to deliver CO – a critical gasotransmitter – in biological environments. CO-RMs are also effective antimicrobial agents; although the mechanisms of action are poorly defined, haem-containing terminal oxidases are primary targets. Nevertheless, it is clear from several studies that the effects of CO-RMs on biological systems are frequently not adequately explained by the release of CO: CO-RMs are generally more potent inhibitors than is CO gas and other effects of the molecules are evident. Methods: Because sensitivity to CO-RMs cannot be predicted by sensitivity to CO gas, we assess the differential susceptibilities of strains, each expressing only one of the three terminal oxidases of E. coli — cytochrome bd-I, cytochrome bd-II and cytochrome bo′, to inhibition by CORM-3. We present the first sensitive measurement of the oxygen affinity of cytochrome bd-II (Km 0.24 μM) employing globin deoxygenation. Finally, we investigate the way(s) in which thiol compounds abolish the inhibitory effects of CORM-2 and CORM-3 on respiration, growth and viability, a phenomenon that is well documented, but poorly understood. Results: We show that a strain expressing cytochrome bd-I as the sole oxidase is least susceptible to inhibition by CORM-3 in its growth and respiration of both intact cells and membranes. Growth studies show that cytochrome bd-II has similar CORM-3 sensitivity to cytochrome bo′. Cytochromes bo′ and bd-II also have considerably lower affinities for oxygen than bd-I. We show that the ability of N-acetylcysteine to abrogate the toxic effects of CO-RMs is not attributable to its antioxidant effects, or prevention of CO targeting to the oxidases, but may be largely due to the inhibition of CO-RM uptake by bacterial cells. Conclusions: A strain expressing cytochrome bd-I as the sole terminal oxidase is least susceptible to inhibition by CORM-3. N-acetylcysteine is a potent inhibitor of CO-RM uptake by E. coli. General significance: Rational design and exploitation of CO-RMs require a fundamental understanding of their activity. CO and CO-RMs have multifaceted effects on mammalian and microbial cells; here we show that the quinol oxidases of E. coli are differentially sensitive to CORM-3. This article is part of a Special Issue entitled: Oxygen Binding and Sensing Proteins. 相似文献