A study of ozone in the Colorado mountains     

F. C. Fehsenfeld  M. J. Bollinger  S. C. Liu  D. D. Parrish  M. McFarland  M. Trainer  D. Kley  P. C. Murphy  D. L. Albritton  D. H. Lenschow 《Journal of Atmospheric Chemistry》1983,1(1):87-105

The seasonal and diurnal variations of ozone mixing ratios have been observed at Niwot Ridge. Colorado. The ozone mixing ratios have been correlated with the NO _x (NO+NO₂) mixing ratios measured concurrently at the site. The seasonal and diurnal variations in O₃ can be reasonably well understood by considering photochemistry and transport. In the winter there is no apparent systematic diurnal variation in the O₃ mixing ratio because there is little diurnal change of transport and a slow photochemistry. In the summer, the O₃ levels at the site are suppressed at night due to the presence of a nocturnal inversion layer that isolated ozone near the surface, where it is destroyed. Ozone is observed to increase in the summer during the day. The increases in ozone correlate with increasing NO _x levels, as well as with the levels of other compounds of anthropogenic origin. We interpret this correlation as in-situ or in-transit photochemical production of ozone from these precursors that are transported to our site. The levels of ozone recorded approach 100 ppbv at NO _x mixing ratios of approximately 3 ppbv. Calculations made using a simple clean tropospheric chemical model are consistent with the NO _x -related trend observed for the daytime ozone mixing ratio. However, the chemistry, which does not include nonmethane hydrocarbon photochemistry, underestimates the observed O₃ production.  相似文献   

Anthropogenic nitrogen deposition induces rapid ecological changes in alpine lakes of the Colorado Front Range (USA)   总被引：10，自引：3，他引：7  

Alexander P. Wolfe  Jill S. Baron  R. Jack Cornett 《Journal of Paleolimnology》2001,25(1):1-7

Recent sediments from two alpine lakes (> 3300 m asl) in the Colorado Front Range (USA) register marked and near-synchronous changes that are believed to represent ecological responses to enhanced atmospheric deposition of fixed nitrogen from anthropogenic sources. Directional shifts in sediment proxies include greater representations of mesotrophic diatoms and increasingly depleted ¹⁵N values. These trends are particularly pronounced since ~ 1950, and appear to chronicle lake responses to excess N derived from agricultural and industrial sources to the east. The rate and magnitude of recent ecological changes far exceed the context of natural variability, as inferred from comparative analyses of a long core capturingthe entire 14,000-year postglacial history of one of the lakes. Nitrogen deposition to these seemingly pristine natural areas has resulted in subtle but detectable limnological changes that likely represent the beginning of a stronger response to nitrogen enrichment.  相似文献   

包气带土体生物地球化学特征与氮转化研究—以河北平原正定试验场剖面为例   总被引：7，自引：1，他引：6  

任福弘  孙继朝  张胜  贾秀梅  张翠云  叶思源 《地球学报》2001,22(4):324-329

为研究氮素的生物地球化学循环问题,通过对河北平原典型试验场贯穿包气带18．5m钻孔剖面土样的物理性质,地球化学指标,有机质含量的测试和微生物的培养鉴定,发现土体的氮素,可溶盐含量（TDS）,Cl^-含量以及微生物细菌的变化随深度不呈简单的线性分布。经分析认为,剖面中的粘性土层是生物的活性层,在氮素转化过程中起主导作用;剖面中多种指标的变化与地质结构呈良好 对应关系,反映环境演化的过程,同时表明,包气带存在着更多尚待提取的全球变化对比研究信息。  相似文献   

苏北潮滩湿地不同生态带碳、氮、磷分布特征^*   总被引：1，自引：0，他引：1  

高建华  白凤龙  杨桂山  欧维新 《第四纪研究》2007,27(5):756-765

通过对比苏北潮滩湿地不同生态带的表层以及柱状沉积物中总有机碳、总氮、总磷和有机磷含量,并结合不同植被不同植株部位中碳、氮、磷的含量变化,分析了潮滩沉积物中碳、氮、磷的垂向和水平分布特征与规律,探讨了不同生态带以及潮滩植被对碳、氮、磷等生源要素的富集作用。对比分析结果表明:苏北潮滩湿地各生态带对不同的测量指标有着不同的富集作用,互花米草滩的总有机碳、总氮和有机磷含量要远大于其他几个生态带,光滩沉积物中总磷的含量最高; 粒度效应是控制互花米草前缘地带以及互花米草滩沉积物中有机碳和氮分布的一个重要因素,盐蒿和芦苇滩中有机碳和氮的分布更多的是受粒度之外的其他因素影响; 不同生态带表层沉积物中的C/N比值分布,大致可反映其有机物来源的差异,而不同生态带中柱状沉积物中的C/N比值相对接近,很难根据C/N比值大小来对不同生态带中的有机物来源进行判断,这可能是埋藏在柱状沉积物中的有机物更多的受到了早期成岩作用造成的。植被对潮滩湿地中碳、氮、磷的分布有着重要影响,3种物质在互花米草、盐蒿和芦苇中的含量差别不是很大,因此潮滩植被对沉积物中上述3种物质的贡献差别主要是由不同植被的生物量和其所处环境的沉积动力差异造成的。  相似文献   

对流层氮氧化物光化学转化特征研究   总被引：10，自引：0，他引：10       下载免费PDF全文

朱彬  孙照渤  安俊岭 《大气科学》2002,26(4):487-495

应用大气光化学模式研究了日间影响NOx光化学转化率的主要物理化学因子.探讨了在不同NMHC/NOx比值时,NOx光化学特征及其转化产物的变化规律.结果表明,影响NOx转化率的主要因子是阳光辐射强度和NMHC/NOx比值.但在NMHC/NOx比值很低时,光强的增加并不能显著提高NOx转化率.温度和初始臭氧浓度对NOx转化率的影响次之.相对湿度对NOx转化率的影响较小.在不同NMHC/NOx比值下,NOx转化特征和产物有很大区别.NMHC/NOx比值高时,产物中PAN＞HNO3.NMHC/NOx比值中(低)时,产物主要是HNO3,PAN等有机氮不到10%(1%).最后初步比较了模拟和观测的NOy组成.  相似文献   

水溶性污染物在土壤中转化的原位实验方法   总被引：3，自引：0，他引：3  

杨胜科  王文科  李翔  李永涛  姜桂华 《西北地质》2002,35(2):20-23

建立了一种研究水溶性污染物在土壤中运转化的原位实验方法，该方法已成功地应用于研究黄土中氨氮的运移转化规律，克服了土柱实验存在的破坏土壤结构及氧化还原电位发生变化等所引起的实验误差。  相似文献   

临南地区石油运移方向与成藏期次研究   总被引：11，自引：0，他引：11  

陈庆春  林玉祥  唐洪三 《沉积学报》2001,19(4):611-616

根据原油及油砂抽提物中含氮化合物分析、原油生物标志成熟度参数及储层流体包裹体烃类成分分析,研究了临南地区石油运移的方向、距离、成藏期次。结果表明临南油田仅有一期油气运聚成藏过程,属中新世末形成的成熟原油,4 甲基甾烷含量较高。曲堤油田存在两期油气运聚成藏过程,早期原油成熟度低,4 甲基甾烷含量低,运移距离较远,成藏后大部分散失 ;晚期充注的原油成熟度较高,4 甲基甾烷含量也较高,并保存至今。  相似文献   

Element budgets of pine stands on lignite and pyrite containing mine soils     

Martin Gast  Wolfgang Schaaf  Joerg Scherzer  Rudolf Wilden  Bernd U. Schneider  Reinhard F. Hüttl 《Journal of Geochemical Exploration》2001,73(2):196

To analyze the development of pine ecosystems on lignite and pyrite containing mine soils, four pine stands with ages of 3–35 years were investigated in a chronosequence approach. Bulk precipitation, throughfall and soil solution in depths of 20, 40, 70 and 100 cm were studied over a three-year period to determine element fluxes in these forest ecosystems on extreme acidic and saline soils.Element budgets are controlled by the processes induced by pyrite oxidation such as intensive weathering of primary minerals, precipitation and leaching of secondary phases.Despite low water fluxes, element outputs can reach extraordinary high values due to very high concentrations in the soil solution. Although element outputs decrease drastically with stand age, respectively, site age, they exceed those of comparable pine stands on non-mine sites. Nitrogen release from the lignite fraction represents a special characteristic of the examined substrates. Nitrogen losses beneath the rooted zone can be 34 kg N ha⁻¹ yr⁻¹ in 100 cm depth. Element input and output in the examined ecosystems are far from balance. Closed cycling of nutrients seems to be recognizable in the case of potassium.  相似文献   

Processing of oxidised nitrogen compounds by passage through winter-time orographic cloud     

R. N. Colvile  T. W. Choularton  J. N. Cape  B. J. Bandy  K. N. Bower  R. A. Burgess  T. J. Davies  G. J. Dollard  M. W. Gallagher  K. J. Hargreaves  B. M. R. Jones  S. A. Penkett  R. L. Storeton-West 《Journal of Atmospheric Chemistry》1996,24(3):211-239

Four case studies are described, from a three-site field experiment in October/November 1991 using the Great Dun Fell flow-through reactor hill cap cloud in rural Northern England. Measurements of total odd-nitrogen nitrogen oxides (NO _y ) made on either side of the hill, before and after the air flowed through the cloud, showed that 10 to 50% of the NO _y , called NO _z , was neither NO nor NO₂. This NO _z failed to exhibit a diurnal variation and was often higher after passage through cloud than before. No evidence of conversion of NO _z to NO₃ ^- in cloud was found. A simple box model of gas-phase chemistry in air before it reached the cloud, including scavenging of NO₃ and N₂O₅ by aerosol of surface area proportional to the NO₂ mixing ratio, shows that NO₃ and N₂O₅ may build up in the boundary layer by night only if stable stratification insulates the air from emissions of NO. This may explain the lack of evidence for N₂O₅ forming NO₃ ^- in cloud under well-mixed conditions in 1991, in contrast with observations under stably stratified conditions during previous experiments when evidence of N₂O₅ was found. Inside the cloud, some variations in the calculated total atmospheric loading of HNO₂ and the cloud liquid water content were related to each other. Also, indications of conversion of NO _x to NO _z were found. To explain these observations, scavenging of NO _x and HNO₂ by cloud droplets and/or aqueous-phase oxidation of NO₂ ^- by nitrate radicals are considered. When cloud acidity was being produced by aqueous-phase oxidation of NO _x or SO₂, NO₃ ^- which had entered the cloud as aerosol particles was liberated as HNO₃ vapour. When no aqueous-phase production of acidity was occurring, the reverse, conversion of scavenged HNO₃ to particulate NO₃ ^-, was observed.  相似文献   

Surface NO and NO2 mixing ratios measured between 30° N and 30° S in the Atlantic region     

F. Rohrer  D. Brüning 《Journal of Atmospheric Chemistry》1992,15(3-4):253-267

Surface NO and NO₂ mixing ratios were measured aboard the research vessel Polarstern during the mission ANT VII/1 from 24 September to 5 October 1988. The measurements were taken along the meridian at 30° W in the Atlantic region covering latitudes between 30° N and 30° S. The average mixing ratios were about 12 pptv NO/30 pptv NO₂ in the Northern Hemisphere and about 7 pptv NO/22 pptv NO₂ in the Southern. Elevated mixing ratios of 20 pptv NO/70 pptv NO₂ were found at 12° N (probably due to air masses originating from the surface of West Africa) and in the region of the ITCZ between 8° N and 5° N. Because of probable contamination by the ship, the measured mixing ratios mostly represent upper limits.  相似文献