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491.
Snowmobile use in Yellowstone National Park has been shown to impact air quality, with implications for the safety and welfare
of Park staff and other Park resource values. Localized impacts have been documented at several high-use sites in the Park,
but the broader spatial variability of snowmobile emissions and air quality was not understood. Measurements of 87 volatile
organic compounds (VOCs) were made for ambient air sampled across the Park and West Yellowstone, Montana, during 2 days of
the 2002–2003 winter use season, 1 year before the implementation of a new snowmobile policy. The data were compared with
similar data from pristine West Coast sites at similar latitudes. Backward trajectories of local air masses, alkyl nitrate-parent
alkane ratios, and atmospheric soundings were used to identify the VOC sources and assess their impact. Different oversnow
vehicle types used in the Park were sampled to determine their relative influence on air mass pollutant composition. VOCs
were of local origin and demonstrated strong spatiotemporal variability that is primarily influenced by levels of snowmobile
traffic on given road segments at different times of day. High levels of snowmobile traffic in and around West Yellowstone
produced consistently high levels of benzene, toluene, and carbon monoxide. 相似文献
492.
Guoyi Zhou Ge Sun Xu Wang Chuanyan Zhou Steven G. McNulty James M. Vose Devendra M. Amatya 《Journal of the American Water Resources Association》2008,44(1):208-221
Abstract: It is critical that evapotranspiration (ET) be quantified accurately so that scientists can evaluate the effects of land management and global change on water availability, streamflow, nutrient and sediment loading, and ecosystem productivity in watersheds. The objective of this study was to derive a new semi‐empirical ET modeled using a dimension analysis method that could be used to estimate forest ET effectively at multiple temporal scales. The model developed describes ET as a function of water availability for evaporation and transpiration, potential ET demand, air humidity, and land surface characteristics. The model was tested with long‐term hydrometeorological data from five research sites with distinct forest hydrology in the United States and China. Averaged simulation error for daily ET was within 0.5 mm/day. The annual ET at each of the five study sites were within 7% of measured values. Results suggest that the model can accurately capture the temporal dynamics of ET in forest ecosystems at daily, monthly, and annual scales. The model is climate‐driven and is sensitive to topography and vegetation characteristics and thus has potential to be used to examine the compounding hydrologic responses to land cover and climate changes at multiple temporal scales. 相似文献
493.
Effects of rare earth elements on the distribution of mineral elements and heavy metals in horseradish 总被引:5,自引:0,他引:5
In order to investigate the effects of rare earth elements (REEs) on horseradish, the distribution of the mineral elements and heavy metals in different organs of horseradish have been studied by using inductively coupled plasma-atomic emission spectrometry (ICP-AES). Meanwhile, three variable major parameters, namely the concentration of REEs, the type of REEs, and the growth stage of plant were chosen. The results indicated that the test REEs, Ce(III) and Tb(III), could be accumulated in leaves, stems and roots of horseradish. In addition, we found that the content of mineral elements was increased in horseradish treated with 20mgl(-1) of Ce(III), but not those with the 20mgl(-1) of Tb(III). Moreover, the content of mineral elements in horseradish was decreased with the increasing concentration of REEs (100, 300mgl(-1)). Furthermore, we found that there were the opposite effects on the content of the heavy metals in horseradish treated with REEs. Finally, we found that the effect of REEs on the accumulation of REEs, and the content of mineral elements or heavy metals of horseradish during vigorous growth stage, no matter positive or negative, was more obvious than that of the other growth stages. These results demonstrated that the distribution behaviors of mineral elements and heavy metals in horseradish can be affected by the type and concentration of REEs, and the growth period of plant. 相似文献
494.
本文介绍了炭催化剂吸附剂标准物质的研制过程。对标准物质的制备技术、均匀性检验、稳定性考察及定值和不确定度进行了逐项分析。采用活性炭浸渍、煅烧技术制得炭催化剂吸附剂标准物质。试验结果表明,该标准物质定值结果准确,均匀性、稳定性良好。铜含量的标准值为11.06%,扩展不确定度为0.13%。 相似文献
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微波萃取技术在分析土壤中有机污染物的应用 总被引:13,自引:0,他引:13
介绍了微波萃取技术及其使用的试剂、设备和条件,对微波萃取在分析土壤中有机污染物的应用予以综述,阐述了微波萃取技术是分析土壤中有机污染物的好方法。 相似文献