大气气溶胶酸度和酸化缓冲能力研究

为了掌握大气气溶胶与酸性降水的关系 ,分析和研究了中国北方和南方不同观测点可吸入颗粒物 (PM10 )的酸度 ,并利用微量酸碱滴定的方法测定了其酸化缓冲能力。结果表明大气气溶胶具有一定的酸度 ,同时对酸化的缓冲能力非常低 ,甚至可以促进降水的酸化 ,这种污染特征也是上述观测点发生酸性降水的重要原因之一。     

2014年北京市CO浓度水平和时空分布

对北京市地面监测站点的CO浓度进行分析,探讨其浓度水平、变化趋势和时空分布特征。2014年春、夏、秋、冬四季北京市CO平均浓度分别为1.06、0.87、1.34、2.17 mg/m³。CO浓度均呈双峰型变化,第一个峰值出现在07：00-09：00,主要由交通早高峰的排放引起;第二个峰值出现在23：00左右,主要受交通晚高峰排放和夜间边界层高度降低的挤压效应的共同影响。从空间分布来看,全年整体呈现南高北低的分布特征,尤其是秋、冬季较为明显,体现了工业布局和区域传输对CO的影响。从全年来看,湿度对CO浓度的影响最大。对2014年冬季北京市的一次高CO浓度分析结果表明,此次过程是由本地排放和区域传输共同造成的,气象要素中地面气压对CO浓度影响最大。     

北京城区降水对PM2.5和PM10清除作用分析

基于北京市PM_2.5和PM₁₀质量浓度、组分浓度以及降水数据,利用数理统计、相关性分析等方法分别从降水总量、降水时长和降水前颗粒物浓度3个角度研究降水对PM_2.5、PM₁₀的清除作用,同时以一次典型降水过程为例,具体分析降水对颗粒物的影响。结果表明：降水总量的增加有助于促进PM_2.5、PM₁₀的清除,随着降水总量增加,PM_2.5、PM₁₀的平均清除率提高,有效清除的比例增加;连续降水可增强对大气颗粒物的湿清除作用,连续降水达3d可有效降低PM_2.5、PM₁₀浓度;降水对PM_2.5、PM₁₀浓度的清除率和大气颗粒物前一日的平均浓度有较好的正相关性。降水对大气颗粒物的清除可分为清除、回升和平稳3个阶段,各个阶段大气颗粒物的变化趋势不同。降水对于大气气溶胶化学组分和酸碱性的改变具有明显作用,对于大气颗粒物各种组分的清除效果不完全相同。对于大气中OC、NO₃^-、SO₄^2-和NH₄⁺去除率较高,且这4种组分主要以颗粒态形式被冲刷进入降水中,加剧了北京市降水酸化程度。     

2010—2019年台州市市区降水化学组成特征及变化趋势

为了解台州市市区大气降水化学成分组成特征及变化规律,对2010—2019年台州市市区降水监测数据进行了统计分析。结果表明:2010—2019年降水样品pH为4.20～4.84夏高冬低,强酸性降水频率下降显著,电导率平均值为3.16 mS/cm。SO₄^2-和NO₃^-是降水中最主要的阴离子,NH₄⁺和Ca²⁺是降水中最主要的阳离子。Ca²⁺浓度在2018年开始有所抬升,SO₄^2-和NO₃^-浓度整体呈波动下降趋势。SO₄^2-与NO₃^-浓度比均值为1.50,呈下降趋势,同大气中SO₂与NO₂的质量浓度比变化趋势基本一致。SO₄^2-和NO₃<...     

乌鞘岭南、北坡降水稳定同位素特征及水汽来源对比

为了揭示季风边缘区降水中稳定同位素特征及水汽来源,利用2016年10月至2017年10月采集的97个降水样品,采用相关分析和HYSPLIT模型,对乌鞘岭南、北坡降水稳定同位素的特征、大气水线方程、温度和降水量效应、水汽来源进行了对比分析.结果表明,南坡大气降水线的斜率与截距低于全球大气水线(GMWL)和北坡大气降水线;南、北坡的同位素温度效应和季节效应明显,但北坡的温度效应比南坡更为明显;除北坡夏季和南坡降水量小于5 mm时降水稳定同位素表现出微弱的降水量效应,南、北坡其它季节或其它降水量级均无明显的降水量效应;来自西北和北方的水汽占90%以上,北坡受季风水汽影响极少,南坡夏季会受到东南季风影响,局地水汽再循环对乌鞘岭南、北坡水汽也有贡献.本研究可提高对高寒山区降水同位素演化的认知,为寒旱区同位素水文学的进一步研究奠定基础.     

降水空间异质性对非点源关键源区识别面积变化的影响

针对地形起伏和降水空间差异较大的农业区非点源污染问题,基于SWAT模型评估了阿什河流域在异质性降水和均匀降水两种情景下总氮、总磷关键源区空间变化规律,统计了两种情景下识别的关键源区面积变化,并分析其与降水特征参数的关系.结果表明,降水量一定时,两种情景下识别的总氮、总磷关键源区面积变化趋势大致相同,且总磷关键源区面积不易受降水空间异质性的影响,但总氮关键源区面积却明显受到其影响.对各年份总氮和总磷关键源区面积与降水特征参数的相关分析表明,总磷关键源区面积与当年降水量呈显著正相关,而总氮关键源区面积却与前一年降水量呈显著正相关.研究结果对进一步探讨降水这一重要驱动因子的不确定性对非点源污染关键源区的影响,以及农业非点源污染的治理具有重要意义.     

构建农民收入增长的长效机制

“三农问题”是关系国家经济和社会发展全局的问题，其核心是农民收入增长，农民收入增长的关键是构建收入增长的长效机制。本文通过分析中国农民收入的现状，从制度视角分析农民收入增长缓慢的土地制度、税费制度、金融体制、公共品供给体制以硬社会保障制度等方面原因．在此基础上提出构建中国农民收入增长长效机制的制度框架。     

VISUALIZATION OF TRENDS AND FLUCTUATIONS IN CLIMATIC RECORDS1

ABSTRACT: Small systematic changes in climatic records are often poorly visualized by standard time series plots because they are usually hidden by the magnitude and variability of the data values themselves. A visualization approach based on the rescaled adjusted partial sums (RAPS) which overcomes the above-stated shortcomings is presented. This visualization highlights trends, shifts, data clustering, irregular fluctuations, and periodicities in the record. Additional information on the number, magnitude, shape, frequency, and timing of fluctuations and trends can also be inferred. The visualization approach can be used for preliminary visual inspection of a time series, to gain a feel for the data, and/or to guide and focus subsequent statistical tests and analyses. It is not intended as a substitute for standard statistical analysis. Alternatively, the visualization approach can be used to display findings of a time series analysis. The capabilities and limitations of the approach are discussed and illustrated for two time series of annual rainfall values.     

APPLICATION OF THE GREEN-AMPT INFILTRATION EQUATION TO WATERSHED MODELING1

ABSTRACT: A computer model was developed, based on the Green-Ampt infiltration equation, to computed rainfall excess for a single precipitation event. The model requires an estimate of parameters related to hydraulic conductivity, wetting front section, and fillable porosity of the soil layers. Values of parameters were estimated from soil textural averages or regression equations based on percent sand, percent clay, and porosity. Average values of effective porosity and wetting front suction were largely acceptable due to the relatively low variability and low model sensitivity to the parameters. Hydraulic conductivity was the most erratic constituent of the loss rate computation due to the high variability and the high sensitivity of the computed infiltration to the parameter. The performance of the Green-Ampt infiltration model was tested through a comparison with the SCS curve number procedure. Seven watersheds and 23 storms with precipitation of one inch or greater were used in the comparison. For storms with less than one inch of rainfall excess, the SCS curve number procedure generally gave the best results; however, for six of the seven storms with precipitation excess greater than one inch, the Green-Ampt procedure delivered better results. In this comparison, both procedures used the same initial abstractions. The separation of rainfall losses into infiltration, interception, and surface retention is, in theory, an accurate method of estimating precipitation excess. In the second phase of the study using nine watersheds and 39 storms, interception and surface retention losses were computed by the Horton equations. Green-Ampt and interception parameters were estimated from value sin the literature, while the surface retention parameter was calibrated so that the computed runoff volumes matched observed volumes. A relationship was found between the surface retention storage capacity and the 15-day antecedent precipitation index, month of year, and precipitation amount.     

HYDROLOGICAL ASPECTS OF THE 1988 DROUGHT IN ILLINOIS1

ABSTRACT: Drought is evaluated in terms of the magnitude and duration of the 1988 spring and summer precipitation shortfall, and according to various components of the hydrologic budget, both surface and sub-surface. The response time of some of these components is investigated, relative to the time of precipitation. Individual water users perceived a beginning and ending of the drought at different times relative to their activities. Some statistics better describe some components of a drought to some users, and better answer some questions, than do others.