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791.
Particulate matter (PM), a component of ambient air pollution, has been the subject of United States Environmental Protection Agency regulation in part due to many epidemiological studies examining its connection with health. Better understanding the PM measurement process and its dependence on location, time, and other factors is important for both modifying regulations and better understanding its effects on health. In light of this, in this paper, we will explore sources of variability in measuring PM including spatial, temporal and meteorological effects. In addition, we will assess the degree to which there is heterogeneity in the variability of the micro‐scale processes, which may suggest important unmeasured processes, and the degree to which there is unexplained heterogeneity in space and time. We use Bayesian hierarchical models and restrict attention to the greater Pittsburgh (USA) area in 1996. The analyses indicated no spatial dependence after accounting for other sources of variability and also indicated heterogeneity in the variability of the micro‐scale processes over time and space. Weather and temporal effects were very important and there was substantial heterogeneity in these effects across sites. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
792.
Due to the increased availability of measurements of various geophysical processes, a need has arisen for statistical methods suitable for the analysis of very large nonstationary spatial data sets. The nearest‐neighbor Gaussian process (NNGP) models are one of the latest and most popular Gaussian process‐based models, which reduce computational complexity and memory storage. The Bayesian inference is based on the assumption of a parametric covariance function that is often assumed stationary or known. Given that NNGP models are sensitive in the stationary assumption in comparison to other reduction methods, there is a need to build nonstationary covariance functions within the NNGP models. However, the construction of a nonstationary covariance function and/or matrix may be computationally expensive by itself in the presence of big data. In this paper, we develop an efficient two‐stage approach that deals with nonstationarity and the computational complexity in the presence of a big spatial data set. We propose a new low‐cost data‐driven tree‐structured partitioning technique to divide the spatial region into distinct subregions. Given the partitions, we construct computationally efficient nonstationary covariance functions for NNGP models. We demonstrate the performance of our approach through simulation experiments and an application to the global Total Ozone Matrix Spectrometer (TOMS) data set, in which the proposed approach performs well in terms of both prediction accuracy and computational complexity. 相似文献
793.
This paper reviews the Bayesian melding approach while a companion technical report cited in the paper gives technical details about the Gibbs sampling algorithm used to implement the model and software developed for the research reported in this paper and available online can enable the method's use in other applications. This paper critically assesses the use of melding for mapping ozone concentration fields for possible future use in setting regulatory standards. This assessment has two stages. First a simulation study validates the computer code and goes on to investigate properties of the melding approach in situation where the “truth” is known. Then it is critically tested on a ozone mapping application using ozone data from the air quality system (AQS) database and simulated data from the multiscale air quality simulation platform (MAQSIP) chemical transportation model for ozone. In all cases, the melding is testing against Kriging, a simpler and more traditional way of mapping spatial fields. Conclusions and recommendations for future work are provided. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
794.
795.
基于地理信息系统GIS和土地利用回归LUR模型,模拟西安市PM2.5浓度空间动态分布,结果表明:与PM2.5浓度相关性最高的分别为缓冲区为2 km的水域面积、人口密度和距离水域距离,R 2分别为0.501,0.393和0.280;与PM2.5浓度相关性最低的分别为缓冲区为4 km的水域面积、未利用地面积和耕地面积,R 2分别为0.039、0.021和0.017.未考虑风速建立的LUR模型多元回归的相关系数为0.856,R 2为0.733,考虑风速的相关系数为0.892,R 2为0.796,表明风速对于污染物的分布影响较大,LUR模型模拟效果较好.模拟的PM2.5年均浓度高风险区分布于中部,中风险区分布于中西部,低风险区分布于东南部和西部. 相似文献
796.
Offshore wind power plants (OWPPs), which are not yet installed in Turkey, are becoming a popular method of energy production around the world because of their environmentally friendly nature. Thus, the installation of OWPPs should be an important agenda item in terms of Turkey's renewable energy policies as a contribution to the global greenhouse gas emission targets. This study proposes a model for installing OWPPs in a suitable part of the Black Sea region of Turkey and simulates the results. The suitable locations for OWPP installation were evaluated according to the technical and geographical conditions of this region and site criteria. Meteorological data from these locations were analyzed in the Wind Atlas Analysis and Application Program (WAsP) to determine the best location. In this study, an OWPP model with a 204.6 MW installed power capacity was proposed for the identified location, which has a wind speed of 8.77 m s−1 and a wind power density of 348 W m−2. Then, an OWPP model and regional energy transmission system was modeled using DigSilent software. The load flow analysis was performed using this model, and the results show that 7616 tons of toxic gas and 1.527 million tons of greenhouse gas could be reduced in the region in a year if the proposed OWPP were put into operation. Thus, with the installation of OWPP, this study shows that annual CO2 emissions can be reduced by 7.63% for the entire Black Sea region. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd. 相似文献
797.
氮氧化物（NOx）是大气中的一类重要空气污染物,二氧化氮（NO2）是其主要组成部分之一,NO2浓度的监测和估算对于环境保护和公共健康至关重要. 使用Sentinel-5P大气污染监测卫星提供的近实时二氧化氮浓度数据（NRTI NO2）、ERA5气象再分析数据和DEM数据作为估算变量,基于Catboost模型,对广东省近地面NO2浓度进行估算. 结果表明：①Catboost模型估算的近地面NO2浓度精度最高,其模型拟合的决定系数（R2）、均方根误差（RMSE）和平均绝对误差（MAE）分别达到0.91、4.89 μg·m-3和3.45 μg·m-3,交叉验证R2、RMSE和MAE分别达到0.90、4.91 μg·m-3和3.43 μg·m-3,同时在月尺度和季尺度也具有良好的稳定性. ②广东省近地面NO2月均浓度总体上呈先降后升的“U”型趋势,1月的NO2浓度最高,最高值为43.8 μg·m-3,7月达到最低点,最低值为14.37 μg·m-3. 近地面NO2季均浓度存在“冬高夏低,春秋过渡”的季节分布特征,各季节NO2浓度大小依次为：冬季（27.53 μg·m-3）>春季（20.77 μg·m-3）>秋季（18.77 μg·m-3）>夏季（14.85 μg·m-3）. ③从空间分布角度看,广东省近地面NO2高值地区主要位于发展迅速且人口密集的地区,而低值地区主要分布在注重港口经济、农业和新能源等领域的地区. 相似文献
798.
Zhou Zai zhi 《环境科学学报(英文版)》1999,11(2):174-180
１ＩｎｔｒｏｄｕｃｔｉｏｎＨｉｇｈｌｙｐｒｏｄｕｃｔｉｖｅｌａｎｄｕｓｅｒｅｓｕｌｔｓｉｎａｃｏｎｔｉｎｕｏｕｓｃｈａｎｇｅｏｆｌａｎｄｓｃａｐｅｓｉｎｒｕｒａｌａｒｅａｓ．Ｕｎｄｅｒｔｈｅｉｍｐａｃｔｏｆｃｒｏｐｐｒｏｄｕｃｔｍａｒｋｅｔｓ,ｌａｎ... 相似文献
799.
通过回顾国内生态环境预警研究历程,系统分析、总结了生态环境预警研究基本原理、研究内容与研究方法,指出国内生态环境预警研究视野涵盖生态环境要素与生态系统、人居生活与产业经济、流域与不同级别行政区等众多领域,但由于基础理论及关键技术研究成果积累有限,研究内容设置欠合理、研究技术方法体系不健全,难以支撑国家及地方生态安全保障需求;提出今后生态环境预警研究亟须强化基础理论建设,补充生态安全问题辨识、诊断及其产生发展、驱动机制等重要研究内容,重视不同类型生态风险在时间上延续、空间上扩展的发展特征,并采用多尺度研究技术获取全面的数据信息充实研究细节、提高生态环境预警精准度,进而健全生态环境预警研究体系,切实为区域生态环境管理提供支撑。 相似文献
800.