内蒙古沙地森林草原过渡带中沙地云彬种群动态

沙地云彬是我国内蒙东部沙地森林草原过渡带的特有濒危树种,沙地杉林是陆地上非常特殊的森林生态系统类型。本文研究了沙地云杉的种群动态,建立了沙地云杉种群生命表、年龄结构、存活曲线和生殖力表,同时研究了沙地云杉种群分布格局及增长动态,可为沙地治理和沙地森林生态系统研究提供科学依据。     

松花江水质因子分析及动态变化

松花江的水质一直受到各方的关注,尤其是在80年代末到90年代初.大多数的研究都关注重金属、有机有毒污染物等主要污染物的源、汇、归宿以及生态效应.然而,这些研究通常只考虑一个或几个独立的水质指标,多个指标的联合效应则很少研究.文章在监测数据的基础上,对松花江水质运用因子分析方法进行了研究.利用因子分析方法可以综合地考虑每个监测断面上的各个监测指标在不同水文期的变化.分析结果表明,松花江的主要污染物是来自非点源的氮源污染物,且其水质在不同的水文期是不同的.这一结果也表明,因子分析方法在分析水质动态变化上是综合有效的.     

20世纪80年代中期以来长三角地区货运量动态研究

以长三角地区16市为研究对象,从数量增长、空间格局变动及集装箱运输的空间竞争与格局演变等方面对长三角地区20世纪80年代中期以来货运量动态变化及其影响机制进行了分析。结果表明：随着经济的快速增长,长三角地区货运量、货运周转量及平均运距均大幅增长,货运量地域空间结构变动复杂,总体上极化特征突出,在时间演化上趋于区域均衡化,但同时货运量与生产地出现了一定的分离态势;集装箱运输竞争激烈,上海中心枢纽港地位初步确立,宁波港具明显的空间集聚优势,但集装箱港口体系总体空间集聚功能尚不突出。货运量动态变化在宏观层面主要受经济全球化与全球供应链及制造业模式转变的影响,在中微观尺度上,则主要受到区域经济系统与综合运输成本、区域分割与交通管理体制等的影响     

基于马尔可夫链的四川省产业结构时空演变

本文利用2000-21007年闻四川省158个县域的产业结构系数,基于传统和空闻马尔可夫链方法,分别构建县域产业结构的非空间和空间马尔可夫转移概率矩阵.对"西部大开发"战略实施以来四川省县域产业结构的时空动态演变特征进行初步分析.首先按照全省产业结构系数的平均水平,将所有县域划分为低、中低、中高和高4种类型,并构建其马尔可夫转移概率矩阵,考察全省县域尺度上的产业结构水平是否存在趋同现象;其次,以每个县域在初始年份的空间滞后类型为条件,构造其空闫马尔可夫转移概率矩阵,分析在不同地理背景影响下四川省县域产业结构的时空演变特征;最后,通过县域产业结构系数的遗历分布,预测四川省县域产韭结构水平的长期发展趋势.结果表明:①2000-2007年间四川省县域尺度上的产业结构存在一定程度的趋同现象,并未发生两极分化:②四川省县域产业结构系数的类型转移受地理背景的影响明显,同一类型区域在不同背景下的转移概率发生显著变化;③在不同区域背景下,四川省县域产业结构水平的长期发展趋势各有不同,以在中低水平背景下的区域发展潜力最大.     

Assessing the impact of Cross Compliance measures on nitrogen fluxes from European farmlands with DNDC-EUROPE

We investigated the effects of the agricultural Cross Compliance measures for European cultivated lands, focusing on nitrogen (N) fluxes from corn fields. Four scenarios have been designed according to some conservation farming practices, namely no-till, max manure, catch crop and N splitting. Results indicated that (1) in the no-till scenario the N₂O fluxes are decreased during the first simulated years, with a return to default fluxes in following years; no-till particularly decreased N₂O emission in the dryer and colder simulation spatial units (HSMUs); (2) the no-till and the N splitting scenarios slightly increased the N surplus because of a decrease in plant uptake; (3) introducing a rotation with alfalfa decreased the N leaching in the corn crops following the catch crops; and (4) the application of fertilizer and manure during the cold and wet seasons led to an increase of N leaching.     

Effects of nitrogen deposition and soil fertility on cover and physiology of Cladonia foliacea (Huds.) Willd., a lichen of biological soil crusts from Mediterranean Spain

We are fertilizing a thicket with 0, 10, 20 and 50 kg nitrogen (N) ha⁻¹ yr⁻¹ in central Spain. Here we report changes in cover, pigments, pigment ratios and FvFm of the N-tolerant, terricolous, lichen Cladonia foliacea after 1-2 y adding N in order to study its potential as biomarker of atmospheric pollution. Cover tended to increase. Pigments increased with fertilization independently of the dose supplied but only significantly with soil nitrate as covariate. β-carotene/chlorophylls increased with 20-50 kg N ha⁻¹ yr⁻¹ (over the background) and neoxanthin/chlorophylls also increased with N. (Neoxanthin+lutein)/carotene decreased with N when nitrate and pH seasonalities were used as covariates. FvFm showed a critical load above 40 kg N ha⁻¹ yr⁻¹. Water-stress, iron and copper also explained variables of lichen physiology. We conclude that this tolerant lichen could be used as biomarker and that responses to N are complex in heterogeneous Mediterranean-type landscapes.     

Reduced ozone by air filtration consistently improved grain yield in wheat

This study considered effects of reduced [O₃] on wheat yield. Open-top chamber charcoal filtered air treatments were compared with non-filtered treatments for field-grown wheat. 30 experiments meeting requirements were found, representing nine countries in North America, Europe and Asia. 26 experiments reported improved yield and 4 experiments reduced yield by filtration, a significant positive effect. Average yield improvement was 9%. Average daytime [O₃] was reduced by filtration from 35 to 13 nmol mol⁻¹. Filtration efficiency was 63% for O₃ and 56% for SO₂. For NO_x it was observed that NO₂ was reduced and NO increased by filtration. Thus, filters convert NO₂ to NO. Most experiments reported low or very low [SO₂] and [NO_x]. Thus, O₃ can be concluded to be the main phytotoxic component in the experiments. Elevated [NO₂] was observed in one experiment. The conclusion is that current [O₃] over large parts of the world adversely affect wheat yield.     

湿法烟气脱硫雾化喷嘴的数值模拟

用计算流体力学软件Fluent进行脱硫雾化喷嘴的内部流场的数值模拟,为喷嘴的优化设计找到一种准确、经济又快捷的方法,对加快脱硫设备国产化有一定的参考意义.     

Spatial and temporal variations in NO2 distributions over Beijing,China measured by imaging differential optical absorption spectroscopy

During the CAREBEIJING campaign in 2006, imaging differential optical absorption spectroscopy (I-DOAS) measurements were made from 08:00 to 16:00 on September 9 and 10 over Beijing, China. Detailed images of the near-surface NO₂ differential slant column density (DSCD) distribution over Beijing were obtained. Images with less than a 30-min temporal resolution showed both horizontal and vertical variations in NO₂ distributions. For DSCD to mixing ratio conversion, path length along the lines of I-DOAS lines of sight was estimated using the light-extinction coefficient and Ångstrom exponent data obtained by a transmissometer and a sunphotometer, respectively. Mixing ratios measured by an in-situ NO₂ analyzer were compared with those estimated by the I-DOAS instrument. The obtained temporal and spatial variations in NO₂ distributions measured by I-DOAS for the two days are interpreted with consideration of the locations of the major NO_x sources and local wind conditions. I-DOAS measurements have been applied in this study for estimating NO₂ distribution over an urban area with multiple and distributed emission sources. Results are obtained for estimated temporal and spatial NO₂ distributions over the urban atmosphere; demonstrating the capability of the I-DOAS technique. We discuss in this paper the use of I-DOAS measurements to estimate the NO₂ distribution over an urban area with multiple distributed emission sources.     

Ground-level ozone in the Pearl River Delta and the roles of VOC and NO(x) in its production

In many regions of China, very rapid economic growth has been accompanied by air pollution caused by vehicle emissions. In one of these regions, the Pearl River Delta, the variations of ground-level ozone and its precursors were investigated. Overall, the ambient concentrations of NO(2) increased quickly between 1995 and 1996, but then slightly decreased due to stringent nitrogen oxide (NO(x)) emission controls. Nonetheless, ambient NO(2) levels in the Pearl River Delta remained high. The regional average concentrations of volatile organic compounds (VOCs) were 290 ppbC in summer and 190 ppbC in autumn. Local emissions and long-distance transportation of pollutants play important roles in the regional distribution of VOCs. Ambient O(3) production is significant in urban areas and also downwind of cities. The relative incremental reactivities (RIRs), determined by an observation-based model, showed that ground-level ozone formation in the Guangzhou urban area is generally limited by the concentrations of VOCs, but there are also measurable impacts of NO(x).