A practical guide to experimental conditions such as statistical variation of signal intensity on quantitative solution state nuclear magnetic resonanace (NMR) analysis is discussed and presented. Statistical analysis showed that there is a relationship between a targeted precision and practical pulse intervals. The bandwidth of the audio filter needs to be set so that all the signals of interest fall into 80% of the centre part of the filter. When fulfilling these conditions, the relative standard deviation (RSD) of a signal area in repeated experiments can be estimated by determining the signal-to-noise ratio (SN) of a single spectrum. When the SN reached 1000, the RSD became constant with increasing SN. With such a condition, accuracy better than 1% should be obtained with quantitative NMR.

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26The Mexico City Metropolitan Area (MCMA) is one of the most polluted megacities in North 27 America. Therefore, it is an excellent benchmark city to understand atmospheric chemistry and 28 to implement pilot countermeasures. Air quality in the MCMA is not within acceptable levels, 29 mainly due to high ground levels of ozone (O 3 ). Tropospheric O 3 is a secondary pollutant formed 30 from the oxidation of volatile organic compounds (VOCs) in the presence of nitrogen oxides and 31 sunlight. To gain a better understanding of O 3 formation in megacities, evaluate the effectiveness 32 of already-implemented countermeasures, and identify new cost-effective alternatives to reduce 33 tropospheric O 3 concentrations, researchers and environmental authorities require updated 34 concentrations for a broader range of VOCs. Moreover, in an effort to protect human health and 35 the environment, it is important to understand which VOCs exceed reference safe values or most 36 contribute to O 3 formation, as well as to identify the most probable emission sources of those 37 VOCs. In this work, 64 VOCs, including 36 toxic VOCs, were measured at four sites in the 38 MCMA during 2011-2012. VOCs related to liquefied petroleum gas leakages exhibited the 39 highest concentrations. Toxic VOCs with the highest average concentrations were acetone and 40 ethanol. The toxic VOC benzene represented the highest risk to Mexican citizens, and toluene 41 contributed the most to O 3 formation. Correlation analysis indicated that the measured VOCs 42 come from vehicular emissions and solvent-related industrial sources. 43 44 Keywords: Volatile organic compound, Toxic volatile organic compound, Ozone, Ozone 45 formation potential 46 47 48 CAPSULE ABSTRACT 49 VOC measurements revealed that compounds related to liquefied petroleum gas leakages are the 50 most abundant, the toxic VOC benzene represents the highest risk to citizens, and toluene is the 51 greatest VOC contributor to O 3 formation in Mexico City. 52 53 5

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In the present work, the different sample collection, pretreatment and analytical methods for polycyclic aromatic hydrocarbons (PAHs) in airborne particulates is systematacially reviewed, and the applications of these pretreatment and analytical methods for PAHs are compared in detail. Some comments on the future expectation are also presented.

This study compared leaf gas exchange, leaf hydraulic conductance, twig hydraulic conductivity and leaf osmotic potential at full turgor between two drought-deciduous trees, Vitex peduncularis Wall. and Xylia xylocarpa (Roxb.) W. Theob., and two evergreen trees, Hopea ferrea Lanessan and Syzygium cumini (L.) Skeels, at the uppermost canopies in tropical dry forests in Thailand. The aims were to examine (i) whether leaf and twig hydraulic properties differ in relation to leaf phenology and (ii) whether xylem cavitation is a determinant of leaf shedding during the dry season. The variations in almost all hydraulic traits were more dependent on species than on leaf phenology. Evergreen Hopea exhibited the lowest leaf-area-specific twig hydraulic conductivity (leaf-area-specific K(twig)), lamina hydraulic conductance (K(lamina)) and leaf osmotic potential at full turgor (Ψ(o)) among species, whereas evergreen Syzygium exhibited the highest leaf-area-specific K(twig), K(lamina) and Ψ(o). Deciduous Xylia had the highest sapwood-area-specific K(twig), along with the lowest Huber value (sapwood area/leaf area). More negative osmotic Ψ(o) and leaf osmotic adjustment during the dry season were found in deciduous Vitex and evergreen Hopea, accompanied by low sapwood-area-specific K(twig). Regarding seasonal changes in hydraulics, no remarkable decrease in K(lamina) and K(twig) was found during the dry season in any species. Results suggest that leaf shedding during the dry season is not always associated with extensive xylem cavitation.

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