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671.
The ozonation of hydroxyl compounds(e.g., sugars and alcohols) gives a broad range of products such as alcohols, aldehydes, ketones, and carboxylic acids. This study developed and optimized a two-step derivatization procedure for analyzing polar products of aldehydes and carboxylic acids from the ozonation of diethylene glycol(DEG) in a non-aqueous environment using gas chromatography–mass spectrometry. Experiments based on Central Composite Design with response surface methodology were carried out to evaluate the effects of derivatization variables and their interactions on the analysis. The most desirable derivatization conditions were reported, i.e., oximation was performed at room temperature overnight with the o-(2,3,4,5,6-pentafluorobenzyl) hydroxyl amine to analyte molar ratio of 6, silylation reaction temperature of 70°C, reaction duration of 70 min, and N,O-bis(trimethylsilyl)-trifluoroacetamide volume of 12.5 μL. The applicability of this optimized procedure was verified by analyzing DEG ozonation products in an ultrafine condensation particle counter simulation system. 相似文献
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采用毛细管柱气相色谱氢火焰离子化检测器测定环境空气中的樟脑,选择硅胶为吸附剂,甲醇/丙酮混合溶剂(体积比90∶10)为解析剂.方法在0.544 mg/L~109 mg/L范围内线性良好,检出限为0.06 mg/L,当采样体积为20 L时,最低检出质量浓度为0.003 mg/m3,标准溶液平行测定的RSD≤3.8%,空白... 相似文献
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676.
气相色谱法同时分析测定土壤中15种有机氯农药残留 总被引:3,自引:1,他引:3
采用石油醚+丙酮(3+1,V/V)作为提取溶剂、硫酸钠溶液与弗罗里藻土净化,气相色谱法同时测定贵州150个土壤背景点15种有机氯农药残留.峰面积与保留时间的精密度分别为1.14~5.15,0.01~0.09;线性关系均在0.99以上;加标回收率为84.3%~127.8%;方法检出限为0.003~0.025ng/g.该方法适用于土壤背景点有机氯农药残留量的分析. 相似文献
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678.
采用溴化衍生-液液萃取法处理地表水,用三重四极杆气相色谱质谱联用仪测定样品中α,β-二溴丙烯酰胺,再换算成丙烯酰胺的质量浓度,该方法在20.0μg/L~500μg/L范围内线性良好,相关系数r为0.998,方法检出限为0.08μg/L。实际水样2个质量浓度水平的平均加标回收率分别为87.5%和92.2%,7次测定结果的RSD分别为9.1%和6.1%。用该方法测定黄河兰州段的黄河水和实验室自来水,结果均未检出。 相似文献
679.
To assess P losses to surface water by runoff during the rice season and by drainage flow during the winter wheat season, serial field trials were conducted in different types of paddy soils in the Tai Lake Region (TLR) during 2000 and 2001. Four P application rates were set as 0 (CK), 30, 150, and 300 kg P/hm2 for flooded rice trials and 0 (CK), 20, 80, 160 kg P/hm2 for winter wheat trials respectively. Field experiments were done in two locations with a plot size of 30 m2 and four replications in a randomized complete block design. A simplified lysimeter was installed for each plot to collect all the runoff or drainage flow from each event. Total P (TP) losses to surface water during rice season by runoff flow from four treatments were 150 (CK), 220 (T30), 395 (T150), 670 (T300) g P/hm2 in year 2000, and 298, 440, 1828, 3744 g P/hm2 in year 2001 respectively in Wuxi station, here the soil is permeable paddy soil derived from loam clay deposit. While the losses were 102, 140, 210, 270 in year 2000, and 128, 165, 359, 589 g P/hm2 in year 2001 respectively in Changshu station, here the soil is waterlogged paddy soil derived from silt loam deposit. During the winter wheat season, total P lost from the fields by drainage flow in the four treatments were 253 (CK), 382 (T20), 580 (T89), 818 (T160) g P/hm2 in year 2000–2001, and 573.3, 709.4, 1123.2, 1552.4 g P/hm2 in year 2001–2002 at the Wuxi station. While these were 395.6, 539.1, 1356.8, 1972.1 g P/hm2 in year 2000–2001, and 811.5, 1184.6, 3001.2, 5333.1 g P/hm2 in year 2001–2002 at the Changshu station. Results revealed that P fertilizer application rates significantly affected the TP concentrations and TP loads in runoff during the rice season, and by drainage flow during the winter wheat season. Both TP loads were significantly increased as the P application rate increases. The data indicate that TP losses to surface water were much higher during the winter wheat season than during the rice season in two tested sites. The data also reveal that the annual precipitation and evaporation rate affected the soil P losses to surface water significantly. Year 2000 was relatively dried with higher evaporation thus P losses to water by both runoff and drainage flow were less than in year 2001 which was a relatively wet year with lower evaporation. Results indicate that texture, structure of the soil profile, and field construction (with or without ridge and deep drains) affected soil P losses to surface water dramatically. Annual possible TP lost to water at the application rate of 50 kg P/hm2 year tested in TLR were estimated from 97 to 185 tones P from permeable paddy soils and 109–218 tones P from waterlogged paddy soils. There was no significant difference of TP lost between the CK and the T50 treatments in both stations, which indicate that there is no more TP lost in field of normal P fertilizer application rate than in control field of no P fertilized. Much higher TP lost in runoff or drainage flow from those other P application rates treatments than from the T50 treatment, which suggest that P losses to surface water would be greatly increasing in the time when higher available P accumulation in plough layer soil in this region. 相似文献
680.
Steven G. McNulty James M. Vose Wayne T Swank 《Journal of the American Water Resources Association》1997,33(5):1011-1022
ABSTRACT: Large deviations in average annual air temperatures and total annual precipitation were observed across the southern United States during the last 50 years, and these fluctuations could become even larger during the next century. We used PnET-IIS, a monthly time-step forest process model that uses soil, vegetation, and climate inputs to assess the influence of changing climate on southern U.S. pine forest water use. After model predictions of historic drainage were validated, the potential influences of climate change on loblolly pine forest water use was assessed across the region using historic (1951 to 1984) monthly precipitation and air temperature which were modified by two general circulation models (GCMs). The GCMs predicted a 3.2°C to 7.2°C increase in average monthly air temperature, a -24 percent to + 31 percent change in monthly precipitation and a -1 percent to + 3 percent change in annual precipitation. As a comparison to the GCMs, a minimum climate change scenario using a constant 2°C increase in monthly air temperature and a 20 percent increase in monthly precipitation was run in conjunction with historic climate data. Predicted changes in forest water drainage were highly dependent on the GCM used. PnET-IIS predicted that along the northern range of loblolly pine, water yield would decrease with increasing leaf area, total evapotranspiration and soil water stress. However, across most of the southern U.S., PnET-IIS predicted decreased leaf area, total evapotranspiration, and soil water stress with an associated increase in water yield. Depending on the GCM and geographic location, predicted leaf area decreased to a point which would no longer sustain loblolly pine forests, and thus indicated a decrease in the southern most range of the species within the region. These results should be evaluated in relation to other changing environmental factors (i.e., CO2 and O3) which are not present in the current model. 相似文献