不同坐标变换方法对城市复杂下垫面碳通量的影响

利用长沙城市森林生态站2013年1—12月的CO2通量数据,分析了三维超声风速的三种坐标变换结果的差异。结果表明:二次旋转(DR)或三次旋转(TR)变换的Pitch角和Roll角变化幅度远大于平面拟合(PF)变换,且都有明显的方向性;DR和TR变换强迫平均垂直风速为0,不符合城市热岛环流引起的平均垂直风速不为0的事实;DR和TR变换明显改变了摩擦速度的大小;TR变换增大了CO2通量的不确定性。因此,本站的倾斜校正宜采用平面拟合变换。     

农村金融对我国农业产出影响的实证研究

选取我国1990～2012年的时间序列数据,运用误差修正模型和协整分析的方法分别探究了农村金融对我国农业产出的短期与长期影响.结果表明,从长期来看,农村金融发展水平、农村金融发展效率与我国农业产出之间存在长期稳定的均衡关系.从短期来看,我国农村金融发展水平对我国农业产出的增长有一定的促进作用,但促进作用较小.整体而言,我国农村金融发展水平对我国农业产出的带动作用较弱.     

安徽省大气环境质量模糊综合评价

以二氧化硫（SO2）、二氧化氮（NO2）和可吸入颗粒物（PM10）作为评价因子,利用模糊综合评价法对安徽省大气环境质量进行了评价与分析.结果表明,可吸入颗粒物是安徽省的首要污染物,但铜陵市有所不同,首要污染物为二氧化硫.模糊综合评价显示,安徽省大气环境受到一定程度的污染,16个市中黄山市的大气环境综合质量最好.近年来,安徽省大气环境质量有所改善,但改善幅度较小.     

基于SVG的功率因数校正系统研究

为了减少感/容性负载与电网之间的无功交换,提高电网电能质量,提出和实现一种基于SVG的功率因数校正系统。该系统使用IGBT全桥电路为主电路,采用TMS320F28335作为控制器,将解耦控制算法移植到DSP中,DSP产生PWM对IGBT进行控制。实验结果表明,该系统能够快速地响应负载侧无功功率的变化,有效地对其进行补偿,减小负载和电网的无功交换。     

我国耕地保护绩效定量研究

根据修正后的耕地面积数据(1978-2012年)和耕地保护相关的经济社会因素,构建耕地数量变化的多元线性回归模型,在对耕地保护政策发展历程、现有体系分析的基础上,依据该模型对我国35年来耕地保护政策的绩效进行了分析.结果显示,我国耕地保护政策绩效显著,35年共遏制耕地减少面积250.96万hm2,遏制耕地减少贡献率达17.35％;耕地保护政策绩效有着明显的时间差异性,不同阶段政策遏制耕地减少的贡献率差异明显,但在耕地保护政策发展的4个阶段,政策遏制耕地减少的贡献率是逐渐上升的,说明耕地保护政策在不断的发展,耕地保护政策的绩效在逐渐发挥.在2003-2012年阶段,耕地减少面积逐渐稳定并降至多年来的最低点,同时政策遏制耕地减少的贡献率达到峰值,表明耕地数量保护的目标绩效显著,达到了顶峰.建议未来的耕地保护工作需要突出耕地的质量建设和生态建设两个着重点.     

Thermal deactivation of high-affinity H2 uptake activity in soils

Soils are the most important sink for atmospheric hydrogen, which is assumed to be oxidized by abiontic soil hydrogenases or by putative high-affinity hydrogenases of microbial origin. The activity of soil hydrogenases has been found to change with soil temperature as it changes during the day and the season. However, it is unclear whether and to which extent the soil hydrogenases are deactivated by increased temperature. Therefore, we incubated soils from different climates and different ecosystems (forest, agricultural, arid, hyper-arid, paddy, peat) at elevated temperature and measured the residual activity at 25 °C after different incubation times. We found that at least part of the soil hydrogenase is deactivated irreversibly already at relatively low temperatures (>30 °C) and short exposure times (>10 min) and that the deactivation was more pronounced in soil from cold versus hot climate. The deactivation kinetics could be fitted to a biexponential model, but were complex with respect to soil type and deactivation temperature. The results show that new hydrogenase activity has to be generated in the soil to compensate for activity loss by diurnal and seasonally increased temperature.     

Tree species affect atmospheric CH4 oxidation without altering community composition of soil methanotrophs

Plant species exert strong effects on ecosystem functions and one of the emerging, and difficult to test hypotheses, is that plants alter soil functions through changing the community structure of soil microorganisms. We tested the hypothesis for atmospheric CH₄ oxidation by using soil samples from a Siberian afforestation experiment and exposing them to ¹³C-CH₄. We determined the activity of the soil methanotrophs under different tree species at three levels of initial CH₄ concentration (30, 200 and 1000 ppm) thus distinguishing the activities of low- and high-affinity methanotrophs. Half of the samples were incubated with ¹³C-enriched CH₄ (99.9%) and half with ¹²C-CH₄. This allowed an estimation of the amount of ¹³C incorporated into individual PLFAs and determination of PLFAs of methanotrophs involved in CH₄ oxidation at the different CH₄ concentrations. Tree species strongly altered the activity of atmospheric CH₄ oxidation without appearing to change the composition of high-affinity methanotrophs as evidenced by PLFA ¹³C labeling. The low diversity of atmospheric CH₄ oxidizers, presumably belonging to the UCSα group, may explain the lack of tree species effects on the composition of soil methanotrophs. We submit that the observed tree species effects on atmospheric CH₄ oxidation indicate an effect on biomass or cell-specific activities rather than by a community change and this may be related to the impact of the tree species on soil N cycling.     

Influence of tree crown characteristics on the local PM10 distribution inside an urban street canyon in Antwerp (Belgium): A model and experimental approach

Apart from influencing the amount of leaf-deposited particles, tree crown morphology will influence the local distribution of atmospheric particles. Nevertheless, tree crowns are often represented very rudimentary in three-dimensional air quality models. Therefore, the influence of tree crown representation on the local ambient PM₁₀ concentration and resulting leaf-deposited PM₁₀ mass was evaluated, using the three-dimensional computational fluid dynamics (CFD) model ENVI-met^® and ground-based LiDAR imaging. The modelled leaf-deposited PM₁₀ mass was compared to gravimetric results within three different particle size fractions (0.2–3, 3–10 and >10 μm), obtained at 20 locations within the tree crown. Modelling of the LiDAR-derived tree crown resulted in altered atmospheric PM₁₀ concentrations in the vicinity of the tree crown. Although this model study was limited to a single tree and model configuration, our results demonstrate that improving tree crown characteristics (shape, dimensions and LAD) affects the resulting local PM₁₀ distribution in ENVI-met. An accurate tree crown representation seems, therefore, of great importance when aiming at modelling the local PM distribution.     

大气氟化物对植物的伤害及其测试分析方法

介绍了氟的自然分布和特性,阐述了大气氟化物对植物的伤害症状、伤害机理,并论述了其测试分析方法。     

我国近地面甲烷浓度分布及变化规律

利用我国业务使用的5个大气本底监测站的观测资料,分析了2009年1月至2013年12月不同地区近地面甲烷(CH_4)浓度的分布和变化规律。结果表明:这5年临安站CH_4浓度最高,其次是龙凤山站,上甸子站居中,而香格里拉站和瓦里关站CH_4浓度最低。上甸子站和龙凤山站CH_4浓度具有明显的双峰特征,最高值出现在夏季,次高值出现在冬季;且受人为活动的影响,CH_4浓度日变化幅度很大。而香格里拉站和瓦里关站由于海拔高,人为排放源少,只有1个峰值出现在自然源排放强烈的夏季。除上甸子站CH_4浓度呈逐年略下降趋势外,其余4个站的CH_4浓度都呈逐渐上升趋势。