基于Landsat数据的关中盆地腹地AOD时空格局及城市化对其影响

气溶胶光学厚度（aerosol optical depth,AOD）是气溶胶最基本的光学特性之一,表征气溶胶对光的消减作用,对区域大气污染有一定的指示作用.首先,以2000~2019年长时间序列MOD09A1产品数据为基础,利用ASTER波谱数据库,构建了Landsat TM/OLI蓝光波段地表反射率数据集,利用深蓝算法（deep blue algorithm,DB）对关中盆地腹地AOD进行了反演估算.其次,通过测算2000~2019多年平均/各年平均AOD和季节AOD值,研究分析了AOD空间分布特征和时间变化趋势;利用经验正交函数分析方法（empirical orthogonal function,EOF）剖析了AOD主要的空间分布模式.最后,探索分析了城市化对AOD时空分布特征的影响.结果表明：①研究区多年平均AOD空间分布受地形和人类活动影响显著,低海拔且人类活动强度大的盆地内部AOD值和变化幅度均高于周围山系.AOD呈现出明显的季节差异性：春季（0.34） > 夏季（0.33） > 秋季（0.23） > 冬季（0.12）,夏季AOD区域差异性最大.②年均AOD呈先增大后减小再增大的变化趋势,2005年达到最大值;春夏两季AOD数值分布离散,而冬季则表现为低值集聚的状态.③EOF分析结果表明,研究区AOD存在3种主要的空间分布模态：第一,AOD空间分布模式表现为区域一致型,特征向量空间分布与海拔梯度一致,反映了不同海拔下AOD变化程度的差异;第二,以秦岭山脉为界,大致呈现南北反相的分布特征,反映出关中盆地地域发展的独特性和与南部秦岭山区的差异性;第三,"东南-西北"的分布格局,表明了AOD在"城镇-乡村"呈反相变化趋势;④研究区AOD值与常住人口密度（R²=0.707,P<0.05）、不透水面密度（R²=0.377,P<0.05）以及工业POI密度（R²=0.727,P<0.5）呈正相关关系,说明城市化对AOD时空分布有一定影响.本研究对加强关中盆地空气质量监测和城市生态环境建设具有重要的意义.     

快速城市化地区的土地利用时空动态变化研究 --以南京市为例

20年来,在中国城市化快速发展的过程中,一系列与城市化相关的环境问题随之产生。六朝古都——南京,作为我国经济最发达的长江流域四大中心城市之一,其快速的城市化过程也不可避免地带来了同样的环境问题。为了研究南京市的城市化和土地利用变化规律及其对水文过程的影响,利用1987、1998、2000年的三期遥感数据,通过分层分类的方法对各土地利用类型进行专题信息提取,结合GIS技术,获得研究区1987~1998,1998~2000年两个时段的土地利用变化转移矩阵。据此全面分析了南京市的土地利用时空变化特征。结果表明：南京市13年来,城乡居民及建设用地以大量蚕食耕地而显著增加,年均增幅达到1.92％;耕地和未利用地则明显减少,年均减幅分别为0.62％ 和1.21％;林地和水域有所增加,主要来自未利用地的转变,剩余12.35％的未利用地则转化为城乡居民及建设用地。引起这一土地利用变化的主要驱动力是人口的增长和经济的发展以及政策制度的激励和导向作用。     

环鄱阳湖浅层地下水水化学特征的时空变化

系统采集了鄱阳湖周边地下水,分析测定各单元的水化学参数.结果表明,环鄱阳湖浅层地下水整体偏酸性,呈低矿化度,局部地区出现微咸水.环鄱阳湖浅层地下水丰、枯水期的优势阴离子为HCO3-,阳离子为Ca2+和Mg2+.运用SPSS软件做离子相关性分析,各离子间均呈正相关性,说明可能有相同的来源.地下水的水化学类型整体表现为HCO3-Ca-Mg型,丰水期相对于枯水期出现较多的NO3-型和SO24-型水体,局部区域优势阴离子改变,出现了NO3-型、Cl-型地下水,可能受到农业化肥和工业废水排放的影响.整体上地下水的水化学类型受当地岩石类型的影响比较大,个别地区受人为的活动干扰较为强烈.     

Extreme events and environmental changes: Tracing sedimentary processes in Central Vietnam coastal lagoons

Sediment cores, obtained in 2004–2005 and in 2008 from seven coastal lagoons of Central Vietnam (Lang Co, Nuoc Man, Nuoc Ngot, Thi Nai, O Loan, Thuy Trieu and Dam Nai), were analysed to assess changes in ²¹⁰Pb, porosity, grain size, and depth distributions of selected major and trace elements (Al, As, Ni, and Zn). The aim was to trace sedimentary processes in areas periodically subject to extreme events. The occurrence of lateral sedimentary inhomogeneities has been hypothesised to explain the differences observed at depth for some tracer profiles, whereas topmost levels present evidence that accounts for the loss of a sediment layer (from 2.0 to 7.5 cm thick) between the two samplings. These losses might be attributed to major typhoons that impacted the coasts of Central Vietnam during the study period.     

Historical evidence of climatic variability and changes,and its effect on high-altitude regions: insights from Rara and Langtang,Nepal

ABSTRACT

Climatic variability and its effects have been experienced in the high-altitude regions of Nepal for some considerable time. Most of the studies on local people’s perception available so far in Nepal on climate include with respect to weather changes, and almost none have been verified with satellite imagery. This study thus attempts to combine meteorological and satellite imagery for comparing local people’s perception so that a more robust validation can be established. Both qualitative (transect walk, key informant interview, focus group discussion and institutional visit) and quantitative (meteorological and satellite image) data and techniques were employed. Local people from Rara and Langtang in Nepal shared their observations and perceptions on the changing climate for the last three decades and the effects on them and their local microclimate. Apart from temperature, rainfall and snowfall anomalies, locals observed changes in the water sources and increasing drought along with alteration in the phenology of tree and agricultural crops as well as vegetation range migration. Satellite image analysis also confirms a change in snow cover as notified by the local people. This study shows that local people’s knowledge could be considered as a complement to the observed scientific evidences of climate change science and their perceptions can be used reliably where scientific data are lacking. Finally, perceived climatic risks, current gaps and future opportunities are discussed and some recommendations are suggested.     

The temporal changes of the concentration level of typical toxic organics in the river sediments around Beijing

In this study, the current situation of five types of toxic organics and endocrine disrupters in the sediments of rivers around Beijing, i.e., polycyclic aromatic hydrocarbons (PAHs), phthalic acid esters (PAEs), organic chlorinated pesticides (OCPs), estrogens (Es), and bisphenol A (BPA), which included 56 contaminants, was analyzed and compared with that registered by the historical literatures. The ecological risks were also assessed. The total concentration of PAHs, PAEs, OCPs, Es, and BPA ranged from 232.5 ng·g^–1 to 5429.7 ng·g^–1, 2047.2 ng·g^–1 to 18051.5 ng·g^–1, 4.5 ng·g^–1 to 11.7 ng·g^–1, 18.1 ng·g^–1 to 105.2 ng·g^–1, and 36.3 ng·g^–1 to 69.6 ng·g^–1, respectively. Among these five types of organic compounds, the concentration levels of PAHs and OCPs have decreased significantly in the last ten years, while those of PAEs and Es had an upward trend compared with the previous studies. BPA still remained at a moderately high level, as it was ten years ago. The risks of the PAEs in all of the sample sites, and fluoranthene, benzo[a]anthrene, and benzo[a]pyrene in the Wenyu River sediment, were relatively high. These results supplemented the database of toxic organics’ concentration levels in the sediments of Beijing rivers.

Open image in new window

     

Estimating the influence of overhead transmission power lines and landscape context on the density of little bustard Tetrax tetrax breeding populations

Collision with conductors and earth cables is a known impact generated by transmission power lines, however there is virtually no information on how these infrastructures might affect bird distribution in a landscape context. With this work we specifically hypothesise that transmission power lines may affect the occurrence of a threatened bird, the little bustard (Tetrax tetrax). To test this hypothesis we used a Stochastic Dynamic Methodology (StDM), analysing the effects of power lines in a landscape perspective and simulating population trends as a response to power line installation and habitat changes induced by agricultural shifts in southern Portugal. The data used in the dynamic model construction included relevant gradients of environmental conditions and was sampled during the breeding seasons of 2003-2006. Transmission power lines were significantly avoided by the little bustard and the developed StDM model showed that the distance to these utility structures is the most important factor determining breeding densities in sites with suitable habitat for the species, which possibly leads to displacement of populations and habitat fragmentation. The model simulations also provided the base to analyse the cumulative effects caused by the habitat degradation that can ultimately lead to the extinction of local populations. Within priority conservation sites, the dismantling of existing transmission lines should be considered whenever possible, in order to ensure adequate breeding habitat. The model is considered useful as an auxiliary tool to be used in environmental impact assessments, management and conservation studies.     

Analysis of the global warming dynamics from temperature time series

Global warming is the observed increase of the average temperature of the Earth. The primary cause of this phenomenon is the release of the greenhouse gases by burning of fossil fuels, land cleaning, agriculture, among others, leading to the increase of the so-called greenhouse effect. An approach to deal with this important problem is the time series analysis. In this regard, different techniques can be applied to evaluate the global warming dynamics. This kind of analysis allows one to make better predictions increasing our comprehension of the phenomenon. This article applies nonlinear tools to analyze temperature time series establishing state space reconstruction and prediction. Since noise contamination is unavoidable in data acquisition, it is important to employ robust techniques. The method of delay coordinates is employed for state space reconstruction and delay parameters are evaluated using the method of average mutual information and the method of false nearest neighbors. Afterwards, the simple nonlinear prediction method is employed to estimate temperatures of the future. Temperature time series from different places of the planet are used. Initially, the approach is verified considering known parts of the time series and afterwards, results are extrapolated for future values estimating temperature until 2028. Results show that these techniques are interesting to estimate temperature time history, presenting coherent estimations.     

科尔沁沙地土地利用变化对土壤特性的影响

在中国科学院奈曼沙漠化研究站放牧试验场周围,选取了不同利用方式和类型的草地（封育和放牧）、林地（乔木和灌木）和农田（灌溉和非灌溉）为研究样地,调查了0～30cm土层每隔10cm的土壤水分质量分数和有机养分（有机碳和全氮）,分析了土地利用变化对土壤水分质量分数和有机养分的影响。结果发现,垂直空间分布上,无论哪种土地类型样地,土壤水分质量分数和有机养分各土层间均无显著差异性（P〉0.05）,土层垂直变化对土壤特性影响均较小。在不同土地利用方式水平空间分布上,土壤水分质量分数和有机养分（土壤有机碳和全氮）灌木林地均显著高于乔木林地（P〈0.05）,而封育草地和放牧草地间以及灌溉农田与非灌溉农田间土壤水分质量分数和有机养分均无显著差异性（P〉0.05）。不同土地利用类型水平分布上,草地土壤水分质量分数显著低于林地和农田（P〈0.05）,而土壤养分质量分数草地显著高于林地和农田（P〈0.05）。分析表明,对沙质草地进行围栏封育和旱作农田退耕还林还草的同时,对水浇农田实行保护性耕作和精细管理,有利于沙地土壤环境改善与生态系统恢复。     

Changes in forest biomass carbon stock in the Pearl River Delta between 1989 and 2003

Forest ecosystems play a significant role in maintaining climate stability at the regional and global scales as an important carbon sink.Regional forest carbon storage and its dynamic changes in the Pearl River Delta have been estimated using the continuous biomass expansion factor(BEF)method based on field measurements of forests plots in different age classes and forest inventory data of three periods(1989–1993,1994–1998,1999–2003).The results show that regional carbon storage increased by 16.76%,from 48....