宁夏土壤水文参数空间分布及干旱指标改进研究

土壤相对湿度是干旱监测和评估中最常用的指标之一,但这一指标的有效水下限较为模糊,实际应用中会将一部分土壤有效水排出在外,从而高估干旱的程度,因此有必要对其进行改进。利用2016-2019年宁夏回族自治区气象局122个土壤湿度观测站0-50 cm土壤田间持水量(%)和凋萎湿度(%)的测定数据,分析了宁夏境内土壤水文参数空间分布特征,并引入土壤相对凋萎湿度,以改善当前干旱监测评估中最旱等级土壤水下限模糊的问题。结果表明:宁夏0-20 cm和20-50 cm土壤水文参数的空间分布特征较为相似,田间持水量、凋萎湿度、有效水和相对凋萎湿度的波动范围均呈南低北高的特点;数值大小上,田间持水量、凋萎湿度、有效水整体呈南大北小,而相对凋萎湿度南小北大;分布区间上,田间持水量、凋萎湿度、有效水、相对凋萎湿度集中在15.0%-25.0%、3.0%-6.0%、10.0%-20.0%、10.0%-30.0%之间。基于相对凋萎湿度改进的干旱指标,在宁夏除特旱上限对应的土壤相对湿度波动范围较大外,轻旱、中旱和重旱对应的土壤相对湿度空间波动范围均较小;轻旱、中旱、重旱和特旱的上限对应的土壤相对湿度分别主要介于82.1%-90.0%、64.2%-80.0%、46.3%-60.0%、28.4%-50.0%之间。改进后的干旱指标其物理意义更加明确,能客观反映较低土壤水分对植物有效性真实情况,研究对提高干旱监测评估的准确性有一定现实意义。     

Estimating Root Zone Soil Moisture at Continental Scale Using Neural Networks

This study investigates the feasibility of artificial neural networks (ANNs) to retrieve root zone soil moisture (RZSM) at the depths of 20 cm (SM20) and 50 cm (SM50) at a continental scale, using surface information. To train the ANNs to capture interactions between land surface and various climatic patterns, data of 557 stations over the continental United States were collected. A sensitivity analysis revealed that the ANNs were able to identify input variables that directly affect the water and energy balance in root zone. The data important for RZSM retrieval in a large area included soil texture, surface soil moisture, and the cumulative values of air temperature, surface soil temperature, rainfall, and snowfall. The results showed that the ANNs had high skill in retrieving SM20 with a correlation coefficient above 0.7 in most cases, but were less effective at estimating SM50. The comparison of the ANNs showed that using soil texture data improved the model performance, especially for the estimation of SM50. It was demonstrated that the ANNs had high flexibility for applications in different climatic regions. The method was used to generate RZSM in North America using Soil Moisture and Ocean Salinity (SMOS) soil moisture data, and achieved a spatial soil moisture pattern comparable to that of Global Land Data Assimilation System Noah model with comparable performance to the SMOS surface soil moisture retrievals. The models can be efficient alternatives to assimilate remote sensing soil moisture data for shallow RZSM retrieval.     

长江流域土壤相对湿度变化及其影响因素

以1992~2012年长江流域196个土壤观测站的旬土壤相对湿度资料为基础,通过线性趋势和Kriging插值等方法分析0~50 cm土层土壤相对湿度年际、年内时空分异和季节变化特征,并从气候和NDVI要素探寻其变化原因。结果表明:(1)长江流域年均土壤相对湿度自1992年以来整体上呈波动增加趋势,年际变化倾向率为0.26%/a。江源地区土壤相对湿度增幅大于其他地区。(2)土壤相对湿度表现为东南和西南部较高,东北和西北部较低的空间分布特点。(3)四季土壤相对湿度增加的强烈程度由大到小依次是秋季、冬季、夏季、春季。(4)土壤相对湿度增加的主要原因是潜在蒸发减少和NDVI增加。     

温度控制对蔬菜废物和花卉秸秆共堆肥的影响

以农业蔬菜和花卉废物为原料,进行了不同堆肥控制温度水平的共堆肥.试验在2m3的静态好氧床中试装置中,采用静态好氧工艺进行,研究分析了55℃,60℃,65℃3个温度控制水平下的废物减量化、底物降解、水分去除等的随时间的变化特征:总废物减量率分别为45.8%,63%和58.1%;有机质的降解率分别为23.4%、41.4%和23.8%;水分去除率分别为59.9%、79.1%和78%.60℃控温工艺的废物减量化效果最好,65℃次之,55℃最差;60℃控温工艺的底物降解能力最强,65℃和55℃工艺的底物降解效果相差不大;60℃和65℃控温工艺的水分去除能力最强,55℃条件下的水分去除能力较弱.     

滇池东南岸农业和富磷区入湖河流地表径流及污染特征

应用聚类分析与因子分析方法,通过8次常规监测,对滇池东南岸10条以农业面源和受磷矿开采区影响的入湖河流的地表径流及其水质污染特征进行了分析,并探讨了其空间差异性。在南岸选取降雨过程相同的3条河流,开展暴雨径流监测,探讨污染物在降雨过程中的流失特征。结果表明,新宝象河的平均流量为2.6 m3/s,占总入湖流量的26.5%;总氮、总磷、化学需氧量、悬浮物是滇池的主要污染指标,许多河流均已严重超标。河流水质在空间上可分为3类,具有明显的空间差异性。总氮、总磷、溶解磷、硝态氮对水质污染的贡献率达到了53.636%,氮、磷含量是河流水质污染的主要贡献因子。降雨条件下化学需氧量、悬浮物浓度增长迅速,流量、悬浮物与大多数水质指标均有相关性,磷矿开采对河流水质的影响在降雨条件下更加明显,其悬浮物浓度在降雨条件下比只受农业面源影响的河流最高高出1.9倍。     

土壤残留塑料的热降解脱附研究

针对土壤的塑料污染问题,提出一种采用热脱附降解技术修复污染土壤的方法.选取4种土壤中常见的残留塑料(聚乙烯(PE)、聚氯乙烯(PVC)、聚对苯二甲酸乙二酯(PET)、聚丙烯(PP))为研究对象,通过控制热解温度和土壤含水率对各污染土壤的修复效果进行探究.实验结果表明:在500℃的最佳热解温度下处理60 min,PE、P...     

基于LMDZ模型的西南地区水汽来源及水汽再循环率的分析

研究基于LMDZ模型对我国西南地区9个站点的同位素数据进行空间插值,利用同位素混合模型对不同来源水汽对降水的贡献率进行时空分析.结果表明,我国西南地区外来水汽对降水的贡献率除部分站点外,均在90％以上;其次为植物蒸腾水汽,占比为0.3％～21.3％,地表蒸发水汽对降水贡献率最小,介于0.1％～8.1％之间,同时外来水汽...     

Impact of climate change on soil moisture dynamics in Brandenburg with a focus on nature conservation areas

Global warming impacts the water cycle not only by changing regional precipitation levels and temporal variability, but also by affecting water flows and soil moisture dynamics. In Brandenburg, increasing average annual temperature and decreasing precipitation in summer have already been observed. For this study, past trends and future effects of climate change on soil moisture dynamics in Brandenburg were investigated, considering regional and specific spatial impacts. Special Areas of Conservation (SACs) were focused on in particular. A decreasing trend in soil water content was shown for the past by analyzing simulation results from 1951 to 2003 using the integrated ecohydrological model SWIM [Krysanova, V., Müller-Wohlfeil, D.-I., Becker, A., 1998. Development and test of a spatially distributed hydrological/water quality model for mesoscale watersheds. Ecol. Model. 106, 261–289]. The trend was statistically significant for some areas, but not for the entire region. Simulated soil water content was particularly low in the extremely dry year 2003. Comparisons of simulated trends in soil moisture dynamics with trends in the average annual Palmer Drought Severity Index for the region showed largely congruent patterns, though the modeled soil moisture trends are characterized by a much higher spatial resolution. Regionally downscaled climate change projections representing the range between wetter and drier realizations were used to evaluate future trends of available soil water. A further decrease of average available soil water ranging from −4% to −15% was projected for all climate realizations up to the middle of the 21st century. An average decrease of more than 25 mm was simulated for 34% of the total area in the dry realization. Available soil water contents in SACs were generally higher and trends in soil moisture dynamics were lower mainly due to their favorable edaphic conditions. Stronger absolute and relative changes in the simulated trends for the past and future were shown for SACs within Brandenburg than for the state as a whole, indicating a high level of risk for many wetland areas. Nonetheless, soil water content in SACs is expected to remain higher than average under climate change conditions as well, and SACs therefore have an important buffer function under the projected climate change. They are thus essential for local climate and water regulation and their status as protected areas in Brandenburg should be preserved.     

Biosynthetic origin of carbon-based secondary compounds: cause of variable responses of woody plants to fertilization?

Summary. We propose that variation in the responses of carbon-based secondary compounds to fertilization in woody plants has a biosynthetic cause. The synthesis of phenylpropanoids and derived compounds (e.g., condensed tannins) competes directly with the synthesis of proteins, and therefore with plant growth, because of a common precursor, phenylalanine. In contrast, the biosynthesis of terpenoids and of hydrolyzable tannins proceeds presumably without direct competition with protein synthesis. Therefore, accelerated plant growth induced by fertilization may cause a reduction in concentrations of phenylpropanoids but may affect less or not at all the levels of other classes of secondary compounds. A meta-analysis based on fertilization experiments with 35 woody plant species supported the predicted differences fertilizing significantly decreased concentrations of phenylpropanoids but not of terpenoids or hydrolyzable tannins. Received 14 May 1998; accepted 23 June 1998.     

新生代农民工市民化进程与空间分异研究

农民工市民化问题是当今城市地理学研究的一个重大课题.基于大连市300名新生代农民工的问卷调查,从外部环境和新生代农民工自身情况两方面,构建了市民化指标体系,修正了基于C-D函数的市民化进程模型,采用SPSS软件对问卷结果进行统计分析,定量分析了大连市新生代农民工市民化进程的特点,运用Maplnfo作出空间分异图,得出大连市新生代农民工市民化进程的空间分异特征:①市内四个主城区的市民化水平低于副城区;②市中心及其辐射地带市民化水平较低,城乡结合部市民化水平较高;③市民化指标与市民化水平空间分异不匹配.目前新生代农民工市民化的相关制度环境处于阻碍阶段,城市居民对新生代农民工的社会认同和接纳程度较好,新生代农民工自身已经具备市民化的能力,城乡结合部和副城区(郊区)是其定居城市的最佳区域,农民工市民化进程是一个任重而道远的任务,国家、社会应为新生代农民工提供一个平台,加快农民工到市民的转化进程.