Assessment of grate sag inlets in a residential area based on return period and clogging factor

Storm in-sag inlets, which typically have inflow capture efficiency of 100%, can violate the allowable water spread criterion of roadways, thus slowing the traffic movement and contributing to accidents. This is especially evident during severe storms of high return periods and when a storm sewer inlet of grate type is adopted, because it is subject to debris and trash clogging factors. In this study, the water spread on pavement for in-sag grates located in a residential area in Kuwait is analyzed in terms of return period and clogging factor. It is found that for a single grate inlet with a return period of 10 years, a clogging factor of 50% can lead to a water spread value exceeding the local design constraint assigned for residential areas, which is one traffic lane of 4m width. It is also shown that for in-sag locations, a double-grate inlet is more preferable than the single one, because the former tends to reduce the adverse hydraulic effect of total inflow on water spread width. The effect of clogging factor on a multiple-grate inlet located in sag is determined from a simple expression suggested in this study.     

库房火灾事故中弹药热安全性研究

为研究不同火灾条件下弹药发生慢速烤燃的升温速率,以典型地面仓库和舰船舱室火灾为研究对象,建立仿真模型,模拟计算发生火灾时弹药贮存环境的热激源强度及其演化规律,针对发动机在此类环境下的热安全性开展仿真计算,分析其响应规律。研究结果表明：不同火灾条件下弹药慢速烤燃的升温速率有很大区别且往往高于标准慢速烤燃试验常用的升温速率3.3 K/h。随着慢速烤燃升温速率的提高,发动机烤燃点火时间提前,点火时刻发动机中间位置温度下降,两端温度升高,且点火位置向发动机喉部移动。研究结果可以指导弹药库房的设计及弹药安全性增强设计。     

寻求解决乌鲁木齐市空气污染的途径

针对乌鲁木齐市最突出的环境问题——冬季采暖期空气污染,从主客观二方面进行了原因分析,并结合“十一五”和2020年环境保护目标,从7个方面分析论述了解决乌鲁木齐市空气污染的途径,使多年困扰乌鲁木齐市的空气污染问题有望从根本上得到解决。     

基于地理探测器的湖南新石器时期聚落遗址人居环境适宜度评价

湖南地区是长江中游新石器时期文化发源地之一,为了更有效地了解新石器时期的人地关系,以高程、坡度、坡向、水体、地貌、土壤和植被类型这7个指标构建新石器时期聚落遗址人居环境模糊指数综合评价体系,运用地理探测器的因子探测法确定各要素的权重,在ArcGIS中将各因子的权重值进行加权叠加和综合等级类型分类,最终得到湖南新石器时期聚落遗址人居环境适宜度评价结果:宜居度中等以上的区域面积最大,总面积为18.59万km2,占湖南省总面积的87.77％;水体权重值占比最高;古人偏爱聚水而居,且集中分布在洞庭湖区域,湘、资、沅、澧周边沿干流分布或在河流的交汇区域分布;适宜度等级较高的遗址类型偏向于丘陵型、台地型和平原型;宜居度中等及以上的遗址多分布在地形较低、朝南、微斜坡、地貌、土壤和植被类型最为丰富的区域.本文可为今后史前聚落遗址分布与自然环境分析提供借鉴意义.     

Combination of steam-enhanced extraction and electrical resistance heating for efficient remediation of perchloroethylene-contaminated soil: Coupling merits and energy consumption

● Coupling merits of SEE and ERH were explored by a laboratory-scale device. ● SEE promotes the soil electrical conductivity and ERH process. ● Preheating soil by ERH improves the soil permeability and SEE. ● Combined method is more energy-efficient for perchloroethylene extraction. In situ thermal desorption (ISTD) technology effectively remediates soil contaminated by dense nonaqueous phase liquids (DNAPLs). However, more efforts are required to minimize the energy consumption of ISTD technology. This study developed a laboratory-scale experimental device to explore the coupling merits of two traditional desorption technologies: steam-enhanced extraction (SEE) and electrical resistance heating (ERH). The results showed that injecting high-density steam (> 1 g/min) into loam or clay with relatively high moisture content (> 13.3%) could fracture the soil matrix and lead to the occurrence of the preferential flow of steam. For ERH alone, the electrical resistance and soil moisture loss were critical factors influencing heating power. When ERH and SEE were combined, preheating soil by ERH could increase soil permeability, effectively alleviating the problem of preferential flow of SEE. Meanwhile, steam injection heated the soil and provided moisture for maintaining soil electrical conductivity, thereby ensuring power stability in the ERH process. Compared with ERH alone (8 V/cm) and SEE alone (1 g/min steam), the energy consumption of combined method in remediating perchloroethylene-contaminated soil was reduced by 39.3% and 52.9%, respectively. These findings indicate that the combined method is more favorable than ERH or SEE alone for remediating DNAPL-contaminated subsurfaces when considering ISTD technology.     

Reduction of the movement and persistence of pesticides in soil through common agronomic practices

Laboratory and field studies were conducted in order to determine the leaching potential of eight pesticides commonly used during pepper cultivation by use of disturbed soil columns and field lysimeters, respectively. Two soils with different organic matter content (soils A and B) were used. Additionally, soil B was amended with compost (sheep manure). The tested compounds were cypermethrin, chlorpyrifos-methyl, bifenthrin, chlorpyrifos, cyfluthrin, endosulfan, malathion and tolclofos-methyl. In soil B (lower organic matter content), only endosulfan sulphate, malathion and tolclofos-methyl were found in leachates. For the soil A (higher organic matter content) and amended soil B, pesticide residues were not found in the leachates. In addition, this paper reports on the use of common agronomic practices (solarization and biosolarization) to enhance degradation of these pesticides from polluted soil A. The results showed that both solarization and biosolarization enhanced the degradation rates of endosulfan, bifenthrin and tolclofos-methyl compared with the control. Most of the studied pesticides showed similar behavior under solarization and biosolarization conditions. However, chlorpyrifos was degraded to a greater extent in the solarization than in biosolarization treatment. The results obtained point to the interest in the use of organic amendment in reducing the pollution of groundwater by pesticide drainage and in the use of solarization and biosolarization in reducing the persistence of pesticides in soil.     

近场长周期强地震动幅值谱研究

本文研究了近场长周期强地震动加速度的傅氏谱和功率谱模型及其参数估计方法,基于强地震动参数统计上的无向性,提出了一种结合地震学模拟模型和工程学统计回归模型的综合方法。文中定义了强地震动平稳段均方根加速度的计算方法,并通过均方根加速度建立了震源力学参数和强地震动工程参数间的关系。通过对目前使用的主观持时定义的应用分析,指出主观持时定义使得估计的地震动过程的峰值加速度的变异性与实际地震动过程的峰值加速度的变异性有显著不同,明显偏小,这对于结构抗震可靠度分析可能会得到失效概度偏小的结果,应引起工程界的重视。     

湿烟羽消散技术对污染物扩散特性的影响

湿法脱硫出口的饱和湿烟气直接由烟囱排入环境会形成湿烟羽,产生视觉污染。分析了湿烟羽的形成和消散过程,重点考察直接加热、降温再热和直接降温等湿烟羽消散技术对颗粒物、SO₂和NO₂扩散特性的影响。结果表明:湿烟羽消散技术对环境颗粒物浓度影响很小,颗粒物最大落地浓度占标率小于1.5%,颗粒物最大落地浓度远低于GB 3095—2012《环境空气质量标准》的浓度限值;降温再热和直接加热可以促进SO₂和NO₂在环境中的扩散,2种技术分别使SO₂和NO₂最大落地浓度占标率降低了31.5%和15.1%;采用直接降温技术消散湿烟羽后,SO₂和NO₂最大落地浓度占标率分别小于20%和70%,SO₂和NO₂最大落地浓度仍低于GB 3095—2012的浓度限值。     

苏州大气颗粒物PM2.5和PM10质量浓度异常“倒挂”现象的成因及影响分析

为深入研究PM_2.5和PM₁₀质量浓度异常“倒挂”现象的成因及影响,在苏州市相城区国控点开展比对监测分析,回顾性分析了2016—2020年苏州全部国控点颗粒物浓度数据。苏州市相城区国控点PM_2.5浓度的比对分析结果表明：该国控点频繁出现PM_2.5浓度高于其他国控点PM_2.5浓度和高于该站点PM₁₀浓度(“倒挂”率高达34%)的“双高”现象,PM_2.5平均浓度比其他9个国控点高12.5%～37.2%,比位于同一站点的备用监测仪器(“倒挂”率为0)高38.1%。2016—2020年,苏州全部国控点“倒挂”时间的总体趋势都是逐年递增,且集中发生在相对湿度较高的20:00至次日07:00。这5年间各国控点PM_2.5浓度异常偏高导致的异常“倒挂”现象对全市年均浓度产生的正误差分别为1.6%、2.8%、6.0%、6.2%和4.1%,基本呈现出逐年递增的趋势。上述结果表明：苏州PM_2.5浓度偏高是由动态加...     

2020年春节期间京津冀及周边地区2次大气重污染过程分析

基于环境空气质量监测数据、天气实况资料、能源与主要大气污染物排放量数据,分析了2000年以来我国主要大气污染物的排放量和能源结构的演变,讨论了我国申请排污许可证企业主要污染物允许排放量空间分布,揭示了2020年1月下旬—2月中旬京津冀及周边地区发生的2次大气重度污染过程的形成原因。结果显示:全国取得排污许可证的企业中,73%的VOCs排放企业、62%的NO_x排放企业、48%的颗粒物排放企业聚集在京津冀及周边地区,密集的排放源为重污染形成提供了充分的污染物和前体物;气象条件对2次典型大气重度污染过程起着至关重要的作用,第一次(1月25—28日)是高压主导型的污染过程,高压抑制了污染物水平扩散,同时大气低层有逆温,抑制了污染物垂直扩散;第二次(2月9—13日)是低压前部型污染过程,由于地面伴有弱低压,并有较强逆温,抑制了污染物扩散;烟花爆竹燃放对PM_2.5浓度的影响基本只有5~10 h,对2次重度污染过程的影响有限。京津冀及周边地区改善环境空气质量任重道远,提出科学的大气污染防治政策,研发适宜的污染防治技术,采取可持续的措施与行动,完善相关标准体系等是真正实现大气环境质量改善的关键。