水体叶绿素a和硅藻群落时空分布及影响因子的对比分析——以云贵高原异龙湖为例

藻类是湖泊生态系统中重要的初级生产者,物种多样性高且对水环境变化敏感,其生产力水平与群落构建模式是反映湖泊环境梯度和生态系统特征的可靠指标。其中硅藻优势属种的演替模式及其环境条件识别,是开展湖泊生态健康和环境质量评价的重要内容。本文选择亚热带地区浅水湖泊异龙湖开展季节调查,对20个采样点的叶绿素a和硅藻群落组成等指标开展分布特征及其驱动因子的定量评价,系统分析藻类变化的时空模式、驱动因子及其指标异同。2020年12月一2021年9月,异龙湖水环境特征的季节波动明显,综合营养指数TSI平均为74.76,总体处于富营养水平。在80个水体样品中共发现硅藻21属68种,群落结构以浮游类型(平均占比79.33%±20.69%)的耐中富营养种为主;在4个季节的调查中,膜糊直链藻Aulacoseira ambigua(61.62%±20.26%)为优势种。主成分分析显示,硅藻群落组成存在明显的空间差异和季节变化。冗余分析和方差分解等结果表明,水体营养因子(TN、TP和N:P)是影响叶绿素a浓度空间变化的重要因子(解释方差为19.08%±11.4%),水温和水深梯度的影响较小(9.63%±11.31%...     

基于总体最小二乘的相似变换模型及其在地图扫描数字化中的应用

在地图扫描数字化中,图纸定向的精度直接影响后续地图要素数字化的精度,而在图纸定向中较为常用的相似变换模型未能周全考虑地图定向点的采集误差以及原始地理坐标的测量误差。引进总体最小二乘方法,建立基于总体最小二乘的相似变换模型,结合地图扫描数字化实验,分析基于总体最小二乘方法的相似变换模型的适用性及优越性。     

2000–2010年中国不同地区人口密度变化及其影响因素分析(英文)

Studying the change in population distribution and density can provide important basis for regional development and planning. The spatial patterns and driving factors of the change in population density in China were not clear yet. Therefore, using the population census data in 2000 and 2010, this study firstly analyzed the change of population density in China and divided the change in all 2353 counties into 4 types, consisting of rapid increase, slow increase, slow decrease and rapid decrease. Subsequently, based on the partial least square(PLS) regression method, we recognized the significant factors(among 11 natural and social-economic factors) impacting population density change for the whole country and counties with different types of population change. The results showed that:(1) compared to the population density in 2000, in 2010, the population density in most of the counties(over 60%) increased by 21 persons per km2 on average, while the population density in other counties decreased by 13 persons per km2. Of all the 2353 counties, 860 and 589 counties respectively showed rapid and slow increase in population density, while 458 and 446 counties showed slow and rapid decrease in population density, respectively.(2) Among the 11 factors, social-economic factors impacted population density change more significantly than natural factors. The higher economic development level, better medical condition and stronger communication capability were the main pull factors of population increase. The dense population density was the main push factor of population decrease. These conclusions clarified the spatial pattern of population change and its influencing factors in China over the past 10 years and could provide helpful reference for the future population planning.     

不同温度条件下氨氮在砂土中的吸附实验研究

温度的变化能够改变水体的环境,引起周围环境中的离子吸附解吸作用的变化。不同于其他土壤,砂土的保水保肥能力更差,砂土地区一旦发生氨氮(NH₄⁺-N)污染,情况会更加严重和突出。为防治砂土地区N H₄⁺-N污染提供理论依据与技术支持,通过N H₄⁺-N的静态吸附试验,研究不同温度条件下N H₄⁺N在粗砂、中砂、细砂中的吸附转化特征,得到如下结论: 在试验设置的温度区间内,总的趋势是温度越低,砂土对N H₄⁺-N的吸附量越高,表明温度升高对N H₄⁺-N的吸附有抑制作用,这主要是因为吸附过程中会产生弱放热效应,进而降低渗滤介质对N H₄⁺N的平衡吸附量; 在25~30 ℃区间内存在硝化与反硝化作用的临界温度,当温度低于临界温度时,N H₄⁺-N吸附量的减少主要是由于发生了硝化反应,当温度高于临界温度时,N H₄⁺-N的吸附量减少主要是由于发生了反硝化反应。