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141.
While the numerical simulation of moisture transfer inside building components is currently undergoing standardisation, the modelling of the atmospheric boundary conditions has received far less attention. 相似文献
142.
Ian A. Wright Rhiannon Khoury Michelle M. Ryan Nakia Belmer Jason K. Reynolds 《Urban Water Journal》2018,15(1):61-67
This study investigated the effects of urban concrete materials, of different particle sizes, immersed in water through a laboratory-based experiment. Water was sourced from a high conservation-value wetland (Blue Mountains upland swamp). Prior to the experiment, wetland water was dilute (32.5 μS/cm), acidic (pH 5.3) and had detectable major ion concentrations of only sodium and chloride. Water was exposed to three treatments of different concrete fragment sizes (whole, crushed and fine). All treatments increased conductivity and pH and also resulted in modified ionic composition where calcium, potassium, hydroxide, carbonate and sulphate were recorded at much high levels. The extent and speed of water chemistry changes was linked to the particle size of the concrete. The results of this study support the hypothesis that concrete can be an environmentally hazardous material influencing water quality in urban catchments. 相似文献
143.
基于酸雨循环侵蚀试验,探究了在不同pH值酸雨溶液与钢纤维掺量条件下,钢纤维增强煤矸石混凝土质量、劈裂抗拉强度及碳化深度等耐久性指标的变化特性。结果表明:第1次酸雨循环时,pH值为2.0酸雨溶液中钢纤维煤矸石混凝土达到最大质量,其增加率为0.25%,随后骤降到最小质量,其质量损失率峰值2.37%;钢纤维煤矸石混凝土劈裂抗拉强度损失率与循环数呈近似线性关系,其最大损失率为21.91%;不同pH值酸溶液中钢纤维煤矸石混凝土碳化深度与酸雨循环数呈正相关,显著性表现为pH=2.0>pH=3.0>pH=4.0;1.0%钢纤维掺量是钢纤维煤矸石混凝土的最优掺量,可优化其空隙结构,有效抑制酸雨溶液的侵蚀。 相似文献
144.
Groundwater salinisation on atoll islands after storm‐surge flooding: modelling the influence of central topographic depressions
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Fresh groundwater lenses (FGLs) are of utmost importance for human survival on small and isolated atolls. This article examines saline damage to atoll FGLs from wave washover caused by storm surge and studies the particular influence of central topographic depressions (CTDs). We model storm surge over atoll islets of contrasting widths (400 and 800 m), both with and without CTDs of various sizes. Three key findings emerge. First, under equilibrium undisturbed conditions, the CTD slightly reduces the size of the FGL compared to atoll islets without this feature. Second, during marine flooding, prior saturated conditions at the base of a CTD impede seawater infiltration into the substrate, thereby limiting saline damage in that location. Third and most crucial, however, the amount of salt accumulated within the CTD is significant, ranging from 2 to 10 times higher than the net subsurface infiltration during the period of the storm inundation. 相似文献
145.
随着我国环境质量的不断下降,环境保护和水资源保护工作引起了广州市政府的高度重视,尤其是当前复杂的广州市排水现状十分不利于当前排水系统的重新设计与改造。市政排水管道建设不能适应当前小区建设发展速度,导致老城区管道混接情况十分严重,各排水分区内合流制、分流制交替存在、排水系统错综复杂。本文主要解析广州市广州市黄埔区石化路以西片区雨污分流改造工程的设计思路及设计创新点。 相似文献
146.
147.
在简述了Ka-波段星-地链路雨衰的特点及诸多抗雨衰对策的基础上,选取了两种常用的调制方式:MQAM(M维正交幅度调制)和MPSK(M维载波相位调制)分别进行研究比较,以获得不同的衰耗门限和雨衰条件下的相对较好的调制方式适应抗雨衰的要求。 相似文献
148.
Congyan Wang 《The Science of the total environment》2010,408(13):2706-2713
With the continuing increase in human activities, ecologists are increasingly interested in understanding the effects of acid rain on litter decomposition. Two dominant litters were chosen from Zijin Mountain in China: Quercus acutissima from a broad-leaved forest and Pinus massoniana from a coniferous forest. The litters were incubated in microcosms and treated with simulated acid rain (gradient pH levels). During a six-month incubation, changes in chemical composition (i.e., lignin, total carbohydrate, and nitrogen), litter mass losses, soil pH values, and activities of degradative enzymes were determined. Results showed that litter mass losses were depressed after exposure to acid rain and the effects of acid rain on the litter decomposition rates of needles were higher than on those of leaves. Results also revealed that simulated acid rain restrained the activities of cellulase, invertase, nitrate reductase, acid phosphatase, alkaline phosphatase, polyphenol oxidase, and urease, while it enhanced the activities of catalase in most cases during the six-month decomposition process. Catalase and polyphenol oxidase were primarily responsible for litter decomposition in the broad-leaved forest, while invertase, nitrate reductase, and urease were primarily responsible for litter decomposition in the coniferous forest. The results suggest acid rain-restrained litter decomposition may be due to the depressed enzymatic activities. According to the results of this study, soil carbon in subtropical forests would accumulate as a long-term consequence of continued acid rain. This may presumably alter the balance of ecosystem carbon flux, nutrient cycling, and humus formation, which may, in turn, have multiple effects on forest ecosystems. 相似文献
149.
针对东北某地待开发的2号钻孔煤、820℃灼烧底灰及煤矸石为淋滤实验对象,详细研究了酸雨类型、酸雨酸度、酸雨降雨量对砷、汞的淋出特征及分布规律。结果表明:砷由于其惰性,在原煤及底灰中均淋不出,矸石中淋出率也不高。汞在原煤中淋出率不大于l%,但在底灰中活性很强,在10h内,去离子水的淋出率为54.58%,硫酸型和硝酸型酸雨可将底灰中汞全部淋出;砷、汞在煤矸石中淋滤规律为:洗矸〉矸石山〉顶板,酸雨强度表现为低酸雨强度时对砷、汞有最大淋出;酸雨雨量的增大会导致矸石中汞的淋出成倍增加。 相似文献
150.