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11.
ABSTRACT: A method is presented for determining low discharge periods of rivers based on threshold values defined in terms of MEAN OF MINIMUM SUMMER (WINTER) DISCHARGES. The method is used to determine summer low flow periods in the Vistula River basin in Poland. Analysis is based on daily discharge data for 84 basins of the Upper Vistula River which was collected by the Polish Institute of Meteorology and Water Economy. 相似文献
12.
ABSTRACT: First order drainage channels originate when the tractive force exerted by flowing water is sufficient to move surface sediment. The amount of runoff available to move sediment is a function of geologic and climatic characteristics. An experimental analysis showed that soils derived from fine grained rocks had lower infiltration rates and higher runoff volume than soils derived from coarser grained rocks in a semi-arid climate. Root density and penetration increased in a more humid climate and increased infiltration rates. The number of first order channels was inversely proportional to the infiltration capacity of the soil. Each first order channel acts as a source area for surface runoff. The distribution of first order channel distances from the gage determines the timing of the delivery of water to the gage. A comparison of the frequency histogram of first order channel distances for drainage basins in Pennsylvania and their hydxographs of runoff from general storms showed marked similarity. This close correspondence indicated the shape of the surface runoff hydrograph and was largely controlled by the distribution of first order channel distances. 相似文献
13.
Woon Leong Lin Siong Hook Law W. N. W. Azman‐Saini 《Corporate Social Responsibility and Environmental Management》2020,27(3):1279-1293
This study assesses the impact of corporate social responsibility (CSR) on corporate financial performance (CFP) by using an innovative threshold estimation technique. We examine whether the CSR effect on CFP is varied with the distinct levels of market differentiation. The empirical analysis is based on a world automotive panel dataset for the period of 2011–2017. We unveil an inverted V‐shaped relationship between CSR and CFP and confirm that the increasing nonparametric regression line up to a certain threshold level indicates a positive effect on CFP, whereas a decreasing line indicates a negative effect. Hence, these findings support the idea that engagement in CSR can boost firm performance by incorporating with market differentiation, since higher firm performance is associated with strong differentiation (i.e., less substitutability), but CSR may not provide large benefits in firms with too high market differentiation. 相似文献
14.
Pengwei Qiao Mei Lei Sucai Yang Jun Yang Xiaoyong Zhou Nan Dong Guanghui Guo 《环境科学学报(英文版)》2019,31(3):115-129
Lateral transportation of soil heavy metals in rainfall events could significantly increase the scope of pollution. Therefore, it is necessary to develop a model with high accuracy to simulate the migration quantity of heavy metals. A model for heavy metal migration simulation was developed based on the SWAT(Soil and Water Assessment Tool) model. This model took into consideration the influence of soil p H value, soil particle size, runoff volume, sediment amount,concentration of water-soluble heavy metals dissolved in runoff and insoluble absorbed to the soil particles. This model was reasonable in Huanjiang watershed, Guangxi Zhuang Autonomous Region, south China, covering an area of 273 km~2. The optimal drainage area threshold was determined by analyzing the effects of watershed subdivision on the simulation results to ensure the simulation accuracy. The main conclusions of this paper were:(1) watershed subdivision could affect simulation migration quantity of heavy metals;(2) the quantity of heavy metals transported by sediment accounted for 97%–99% of the total migration quantity in the study watershed. Therefore, sediment played the most important role in heavy metal migration;(3) the optimal drainage area threshold percentage to ensure high simulation accuracy was determined to be 2.01% of the total watershed;(4) with the optimal threshold percentage, this model could simulate the migration quantity of As, Pb and Cd accurately at the total watershed and subwatershed level. The results of this paper were useful for identifying the key regions with heavy metal migration. 相似文献
15.
中国政府提出要力争在2030年前实现碳达峰,因此积极探索不同发展模式下典型地区的碳达峰时间和峰值十分必要.将门限回归模型与STIRPAT模型相结合,构建门限-STIRPAT扩展模型,分析华东地区7个省市2005-2019年的碳排放,结合情景分析法,分别预测华东地区各省市2020-2040年的碳排放.结果表明:在基准情景的发展模式下,华东地区各省市均可在2030年实现碳达峰目标;在节能发展情景和绿色发展情景的模式下,各省市可以提前4～5年实现碳达峰目标.对于华东地区的7个省份,建议上海、江苏和浙江应以节能发展情景为标准进行产业发展规划;安徽、福建、江西和山东适合选择基准情景,并力争以节能发展情景为标准,布局产业发展. 相似文献
16.
为研究咸潮预警,上海某饮用水源地安装了蓝色卫士水质综合预警系统。采用实验室配制人工海水模拟减潮,通过动态实验研究蓝色卫士的成潮预警值。试验证明,成潮预警值设定范围为1．6～1．8较好。经过连续1a自动监测,蓝色卫士共准确预警预报两次成潮,成功保障了该水源地的饮水安全。 相似文献
17.
为探讨空气中ρ（PM2.5）的空间集聚特征和气候、大气成分变量对空气中ρ（PM2.5）的影响,利用首批纳入PM2.5监测的74个城市的ρ（PM2.5）数据计算Moran's I指数,并选取其中38个典型城市进行计量分析.在基于引力模型的空间权重矩阵基础上,构建面板数据SDM（空间面板杜宾模型）.结果表明:ρ（PM10）、ρ（SO2）、ρ（CO）、ρ（O3）、RH（relative humidity,相对湿度）与城市ρ（PM2.5）呈正相关,而T（temperature,温度）和WS（wind speed,风速）与城市ρ（PM2.5）呈负相关;ρ（PM10）、ρ（CO）、RH是位于前3位影响城市ρ（PM2.5）的关键性因素,其总效应分别为0.720 1、0.241 7、0.133 9.地理上邻近城市ρ（PM2.5）具有明显的外部空间溢出效应,即邻近城市ρ（PM2.5）每增加10百分点,将导致该地区ρ（PM2.5）增长6.12百分点.300 km左右是保证PM2.5区域\"联防联控\"最佳效果的最大门槛距离,超过该门槛距离,区域\"联防联控\"的力度和效果会随着距离的增加而逐渐减弱;当门槛距离大于500 km时,ρ（PM2.5）的空间自相关性不显著.气候变量中,RH和ρ（PM2.5）呈同方向变化,而T、WS与ρ（PM2.5）呈反方向变化.研究显示,关注单一地区或单一因素（气候或大气成分）均不能有效控制PM2.5污染,在保持经济稳定增长的前提下,各地治理PM2.5应从调整产业结构、优化能源结构、完善防控机制等多个维度共同推进,促使经济增长方式早日从\"粗放型\"向\"集约型\"转变. 相似文献
18.
工艺安全管理系统的适用范围——危险化学品目录及临界量的确定 总被引：1，自引：0，他引：1
从工艺安全管理（PSM）的角度,对美国、欧盟等的工艺安全管理系统适用范围的定义进行分析,结合目前国内《重大危险源辨识》中给出的部分危险化学品的临界量,以此为基础制定适合我国国情的危险化学品目录并确定各物质的临界量,提出在我国推行工艺安全管理系统的建议。 相似文献
19.
CHENG Song 《环境科学学报(英文版)》2007,19(4):502-507
To demonstrate the existence of light thresholds in plant growth and to examine the effects of elevated CO2 on the shade tolerance of a tree species, an experiment consisting of a completely randomized design for a total of 96 yellow birch (Betula alleghaniensis Britton) seedlings was conducted with 3 light levels (2.9%, 7.7%, 26.1% of full sunlight)×2 CO2 levels (350 and 700±10 ppm) with 4 replications in a phytotron. The study proved that thresholds exist and they vary in different plant organs. In ambient CO2, the thresholds were 13.3%, 18.7%, 15.0%, 15.2%, and 15.6% of full sunlight for stem, leaf, root, total plant biomass, and the averaged value, respectively. In 700 ppm CO2, the corresponding thresholds were 16.7%, 21.3%, 18.1%, 21.7% and 19.5% for stem, leaf, root, total plant biomass, and the averaged value, respectively. The lowest threshold in the stem is an indicator of the minimal light intensity for regular growth for seedlings of this species. Below this threshold, light-stressful growth occurs. The result of a paired t-test indicated that the thresholds in elevated CO2 were significantly higher than in ambient CO2. This suggests that yellow birch will lose its moderate shade tolerance, evolutionally becoming a shade-intolerant species, and that it may become more difficult to naturally regenerate in the future. 相似文献
20.
随着人民对美好生活需求的日益增长,政府空气污染治理的效率问题日益得到重视。本文从地方政府空气污染治理效率及其影响因素的视角入手,以全国30个省份为研究对象,运用超效率SBM模型测算2003—2015年各省级区域的空气污染治理效率。在此基础上,运用门槛回归模型分析政府空气污染治理效率的影响机制。研究表明:①地区间空气污染治理效率差异性较为显著。中部、西部空气污染治理效率整体呈下降趋势。东部和东北地区空气污染治理效率则上升比较平稳。②政策规划、碳源、污染物排放和环境治理投入表现出双重门槛特征,其中碳源对空气污染治理效率影响显著,而以碳为首的能源消费结构则主要对中部和西部空气污染治理效率产生影响。落后地区政府应注重产业升级,财政上应对碳税等税目进行征收,产业上应鼓励企业创新,并对落后企业进行倒逼升级。 相似文献