多重密度布点对土壤有机质空间特性的解析

论文以张家港市耕层土壤有机质（Soil organic matter, SOM）为目标变量,通过网格布点建立11种样点密度梯度,运用经典统计学和地统计学方法研究其空间特性随布点密度变化的趋势规律。结果表明,各密度下SOM的变异系数稳定在21.70%~23.12%之间,表现出中等程度变异;随着布点密度降低,SOM的块基比和分维数分别由37.52%、1.838波动降至18.70%、1.714,Moran’s I则由0.485起伏升高至0.857,相应地其空间变异中结构变异组分增多、随机变异贡献减少,空间自相关性也逐渐增强;SOM呈现西南-东北递减分布,随着样点密度减小,其空间格局趋于简化。论文以布点密度为视窗,揭示了SOM的多重空间尺度特征,可为解析土壤属性的层级结构提供参考依据。     

江汉平原县域尺度土壤有机质空间变异特征与合理采样数研究

土壤有机质含量是衡量土壤肥力和评价耕地质量的重要指标。在县域尺度下,利用合理数量的样点反映其空间分异特征具有重要意义。论文选取位于江汉平原腹地的湖北省公安县为研究区,布设了4 045个样点并测定其有机质含量,采用半方差分析得到土壤有机质空间变异特征,基于Moran’s I揭示空间变异较大地区,并通过二分法的思想逼近最佳合理采样数值。结果表明：研究区土壤有机质分布呈中等空间相关性,有6个局部区域的空间变异明显高于邻近地区,采样点数量与插值精度呈正相关,合理采样数为598个。研究结果可以为江汉平原县域耕地质量监测和管控提供指导。     

Anthropogenic factors and their potential impacts on the sustainable development of Abu Dhabi's terrestrial biological resources

SUMMARY

Since the discovery of oil, the United Arab Emirates has undergone a process of rapid development, increasingly affecting the ecosystems of the country. Limited scientific literature dealing with these ecosystems is available, although a process of comprehensive ecological research has been initiated over the last few years. Further information on the soils, vegetation, fauna and climate are required in order to initiate a process of sustainable use of natural resources.

Abu Dhabi Emirate was surveyed for anthropogenic factors in its habitats using an off-road vehicle, a global positioning system (GPS) and satellite imagery. The emirate was divided into six geomorphological units. Livestock was found to be the most common anthropogenic factor and is believed to have caused degradation of the natural vegetation. Agriculture, silviculture and urbanization were common and caused habitat loss and fragmentation. Rubbish dumping, earth moving and car tracks were also widespread, whereas air pollution and fences were limited. Four of Abu Dhabi's geomorphological units were classified as low-impact zones, two as low- to medium-impact zones and one as a medium- to major-impact zone. Environmental Impact Assessments (EIA) and detailed ecological research were suggested as future mechanisms to implement sustainable development, and livestock control was suggested as a tool for habitat restoration.     

Using a sub-grid scale modeling approach to simulate the transport and fate of toxic air pollutants

Several air toxics are emitted from mobile sources on roadways and these emissions account for a significant fraction of the health risks to the population. In addition, health effect studies are now becoming more comprehensive and some account for the spatial heterogeneities of air pollutant concentration fields (as is the case near roadways). Standard models can simulate either the near-source concentration fields or the urban background, but no model can handle both spatial scales in the vicinity of roadways in a coherent and scientifically correct manner. Here, we present a model that provides such an integrated treatment by combining a grid-based air quality model of the urban background with a plume-in-grid representation of roadway emissions. The model is applied to simulate near-roadway concentrations due to emissions from a busy interstate highway in New York City. Qualitative comparisons with typical measured concentration profiles show that the model captures the observed features of toxic air pollutant concentrations near roadways.     

Parameterization of the roughness length over the sea in forced and free convection

In the condition of free convection, the Charnock relation is inadequate. In this paper we extend the Charnock relation to include the effect of free convection on the roughness length. As a result, the singularity in the Monin–Obukhov similarity theory can be avoided. This paper shows two approaches to derive the roughness length formula in the forced and free convections. The first approach is based on the mixing length theory and the use of the observational data of the vertical velocity variance. We introduce a new vertical velocity scale based on the vertical velocity variance; this velocity variance is well behaved in the atmospheric boundary layer and easy to obtain from field experiments. The second approach is based on the theoretical framework of Sykes et al. (Q R Met Soc, 119: 409–421). From that framework, we develop a theory to obtain the roughness length formula. The results of these two approaches are in agreement with each other. In the past, a multiplication factor associated with free convection was considered to be a constant. This paper shows that this multiplication factor is, in fact, also dependent on the depth of the mixing height. In previous studies, experimental works were often conducted without taking into account the depth of the mixing height. Not taking into account the mixing height in the estimation of the roughness length in free convection would result in an inaccurate estimate of the roughness length and hence the drag coefficient. An erratum to this article can be found at     

混凝-微滤膜组合净水工艺中膜过滤特性及其影响因素

采用混凝-微滤膜组合工艺处理微污染原水,间歇抽吸的运行方式连续运行,考察了膜组件的抽吸时间,抽/停时间比和曝气量对膜过滤性能的影响.采用膜通透性J/p作为膜过滤性能的评价指标.结果表明,在各操作条件下,膜通透性J/p由于膜污染的发生均先快速降低,随后随时间缓慢下降.但J/p的初期下降速度和缓慢下降阶段的相对稳定值因操作条件的不同而不同.抽吸时间对膜通透性影响较大,其次为抽/停时间比.在一定的条件下,抽吸时间缩短1/2,产水率可提高2倍;抽/停时间比缩短,产水率可提高50%.当抽吸时间和抽/停时间比分别为15min和3.8时,J/p值较高.曝气量在一定范围内的增加有利于提高膜通透性.本试验中,曝气量由2m³/h增加至4m³/h时,膜通透性可提高约15%,但当曝气量增加到6m3/h时,膜通透性并无显著改善.膜面污染物分析表明,在本研究使用的原水条件下,Si和Ca是主要的无机污染元素.     

城市家庭规模与结构对生活污水排放特征影响分析

以北京、上海、广州、兰州、昆明等5个城市30个中等收入城市家庭为研究对象,探讨了家庭规模、家庭结构对生活污水排放特征的影响.结果表明,城市家庭生活污水中各污染物排放量随家庭规模增大而增大,其中受家庭规模经济影响,COD、BOD的排放强度呈现出较为明显的边际递减规律,而TN、TP主要受家庭居民个体因素影响;综合考虑家庭规模、家庭结构的影响,首次提出家庭污染等效因子,把所考察的家庭转换成“等价(参照)家庭”,相对于参照家庭而言,所考察的家庭的污染排放状况与家庭污染等效因子成正比,由此反映不同家庭类型与生活污水排放之间的特定关系.     

An empirical investigation of returns to scale: The Welsh coal industry

This article attempts to study both returns to scale and optimal size of production. Specifically, the authors estimate a ray-homothetic production function which allows the returns to scale to vary with ouput size and input mix. The production model is estimated using data from the Welsh coal industry for the period 1961–1976. Findings showed that, first, the Welsh coal industry suffers from a level of production which is either too small or below its optimal level and, second, this discrepancy between actual and optimal production worsened over the period considered.     

Examining Landscape Dynamics at a Watershed Scale Using Landsat TM Imagery for Detection of Wintering Hooded Crane Decline in Yashiro,Japan

It is usually inappropriate to define rectangular land areas or administrative units as the extent for quantifying landscapes that possess hierarchical structure. As a functional unit established by geophysical relationships, the watershed is one of many natural scales in the hierarchical landscape. We examined the dynamics of the Yashiro watershed of Japan at the landscape level using pattern metrics based on Landsat thematic mapper (TM) imagery from 1985 to 1998. This watershed provides important habitats for the hooded crane (Grus monachus), a vulnerable species. While its world population has remained stable, the number wintering at Yashiro has declined in recent years. Changes in landscape metrics reveal that the spatial pattern within the watershed underwent homogenization due to depopulation of local people and shifts in local energy requirements and forest management policy at Yashiro. Specific changes include: a decrease in bare land area from 6.2% to 1.0% of the landscape, increased forest cover from 69.2% to 76.1%, reduction in patch number from 1194 to 616 and enlarged mean patch size, and a decrease in total edge from 223,740 m to 158,040 m. The rate of change in landscape metrics indicates a rapid change towards homogeneity in the landscape since 1990. The temporal changes in hooded crane populations corresponded to the changes in landscape. An alternative explanation has been proposed that decline of the species is influenced by landscape dynamics affecting both habitat selection and food resources. Conservation at the watershed scale is suggested to be complementary to the current conservation measures of the species.     

Coping with Change: The Small Experiment as a Strategic Approach to Environmental Sustainability

The patterns of living, planning, and resource utilization as practiced in Western countries for decades are not sustainable; change of some sort is essential. But what changes are appropriate, and, perhaps more important, will people accept them? The small experiment framework provides a strategy for meeting the challenge of change. By encouraging participation, limiting the scale of initial change, and incorporating some aspects of the familiar, many of the difficulties that make change so problematic can be mitigated or even eliminated. An exploration, from a psychological perspective, of the characteristic difficulties surrounding potential change provides the context for a discussion of the components of the small experiment and an analysis of how these elements address these characteristic challenges. A comparison to adaptive management is drawn, and several concrete examples illustrate how the strategy has been used successfully to address a variety of environmental problems.