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Precipitation Processes01:12

Precipitation Processes

5.3K
The experimental conditions in a gravimetric analysis should be optimized to maximize the particle size and purity of the obtained precipitate. Ideally, the concentration of the precipitating reagent should be low with effective stirring to maintain low relative supersaturation for the growth of large crystals. In homogeneous precipitation, the precipitant is slowly generated by a chemical reaction in the solution to avoid local reagent excesses. For example, urea decomposes gradually to...
5.3K
Precipitation and Co-precipitation01:17

Precipitation and Co-precipitation

4.0K
Precipitation and coprecipitation methods can be used to separate a mixture of ions in a solution. In qualitative inorganic analysis, ions that form sparingly soluble precipitates with the same reagent are separated based on the differences in solubility products. For example, consider the separation of Cu(II) and Fe(II) ions by precipitation as insoluble sulfides. First, copper(II) sulfide is precipitated by the addition of acidic H2S, where the dissociation of H2S is suppressed. Adding H2S...
4.0K
Precipitation Gravimetry01:03

Precipitation Gravimetry

14.4K
Precipitation gravimetry is based on converting an analyte into a sparingly soluble precipitate, which is separated by filtration and weighed. An ideal precipitate should be pure, insoluble, of known composition, and easily filtered from the reaction mixture.
In determining nickel by gravimetric analysis, a precipitant of ethanolic dimethylglyoxime is added to a hot nickel salt solution. This is quickly followed by the dropwise addition of dilute ammonia solution until precipitation occurs. A...
14.4K
Precipitation Titration: Overview01:26

Precipitation Titration: Overview

9.6K
Precipitation titration involves the reaction of a titrant and an analyte to generate an insoluble precipitate. While precipitation titration uses various precipitating agents, silver nitrate is the most common precipitating reagent; titrations involving Ag+ are called argentometric titrations. Usually, the endpoint in a precipitation titration can be detected by visual indicators.
A precipitation titration curve demonstrates the change in concentration of the titrant or analyte upon adding the...
9.6K
Influence of Earth's Curvature and Atmospheric Refraction on Leveling01:26

Influence of Earth's Curvature and Atmospheric Refraction on Leveling

881
During leveling, the Earth's curvature and atmospheric refraction introduce deviations in the line of sight from a true horizontal reference. When the line of sight is leveled, it remains perpendicular to the plumb line only at a single point. Beyond this, it deviates due to the Earth’s curvature, represented by the correction C. For a sight distance D, the deviation can be derived using the relationship:This relationship shows that the deviation increases quadratically with distance. Over a...
881

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相关实验视频

Updated: Jan 17, 2026

Surface Renewal: An Advanced Micrometeorological Method for Measuring and Processing Field-Scale Energy Flux Density Data
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使用高分辨率快速更新 (HRRR) 数据准备分散模型表面气象输入.

Xueying Zhang1,2, Elaine Symanski1,2, Hannah Renee Paduch2

  • 1Department of Medicine, Section of Epidemiology and Population Sciences, Baylor College of Medicine, Houston, TX, USA.

Research square
|September 18, 2025
PubMed
概括
此摘要是机器生成的。

高分辨率快速更新 (HRRR) 数据通过提供比传统气象站更准确的气象输入来改善空气污染分散模型. 这种新的框架增强了预测,特别是在观测数据稀少的领域.

关键词:
分散模型是一种分散模型.HRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR空气污染 空气污染气象数据 气象数据

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科学领域:

  • 大气科学 大气科学
  • 环境科学 环境科学
  • 空气质量建模空气质量模型

背景情况:

  • 准确的气象数据对于空气污染分散模型至关重要.
  • 传统模型使用固定位置的气象站数据,由于分布稀疏,在捕捉微尺度变化方面存在局限性.
  • 观测数据中的差距阻碍了准确的污染预测,特别是在偏远或数据稀疏的地区.

研究的目的:

  • 开发和评估一个新的框架,用于生成美国气象学会/环境保护局 (EPA) 监管模型 (AERMOD) 兼容的地表气象数据,使用高分辨率快速更新 (HRRR) 数据集.
  • 评估HRRR衍生的气象数据在预测与交通相关的二氧化 (NO2) 度的性能,使用研究线源 (R-LINE) 分散模型.
  • 将HRRR数据的预测精度与传统的观测气象数据进行比较.

主要方法:

  • 从3公里的每小时HRRR数据集生成了AERMOD兼容的地表气象数据 (.sfc).
  • 创建了HRRR气象数据的三个场景,包括对对流动和稳定的行星边界层条件的调整.
  • 在R-LINE模型中应用HRRR衍生和AERMET处理的观测气象数据来预测美国443个监测地点的NO2度.
  • 使用确定系数 (R2) 和协议指数 (IOA) 评估模型性能,通过将预测的NO2与测量数据进行比较.

主要成果:

  • HRRR衍生的气象数据场景与观察数据 (R2=0.16) 相比,平均R2 (0.26) 更高,表明解释变异增加了60%以上.
  • 在预测NO2度方面,HRRR数据通常优于观测数据,特别是在离气象站更远的地方,交通量不同的地方.
  • 网站特定的协议指数分析显示,HRRR输入在美国大陆的大部分地区表现更好,但与观察数据相比,在密集的城市地区效果较差.

结论:

  • 高分辨率快速更新 (HRRR) 数据集为空气污染分散模型的传统观测数据提供了可行且潜在的优越替代方案.
  • 开发的框架证明了HRRR数据在提高分散模型的准确性方面的潜力,特别是在数据稀缺的环境中.
  • HRRR数据显示,对二氧化等污染物的预测能力得到了增强,这突显了其对空气质量管理和研究的实用性.