The effects of missing data on the calculation of precipitation-weighted-mean concentrations in wet deposition

Uncertainties in the calculation of monthly, seasonal and annual precipitation-weighted-mean concentrations due to missing data are addressed. An algorithm is presented to estimate the effects of missing samples through the use of a simulation technique. Quantitative estimates of uncertainty due to missing data are given for monthly, seasonal and annual precipitation-weighted-mean sulphate and nitrate concentrations at six monitoring sites where daily precipitation samples were taken. It is found that the expected value of the precipitation-weighted-mean concentration estimator is biased if the percentage of missing samples (% MN), and the percentage (% MP) of the precipitation amount associated with the missing samples, are different. The absolute value of the bias becomes larger as the difference increases. The standard deviation of the estimator increases with increasing values of % MP. For a given value of % MP, its a minimum when % MN is equal to % MP, and increases with increasing differences between % MN and % MP. These results indicate that % MN of about 10%, which is not uncommon in precipitation networks data, gives an uncertainty of about 10, 5 and 2 % for monthly, seasonal and annual averaging periods, respectively. Procedures to estimate confidence intervals for the true values from observed precipitation-weighted-mean concentrations are presented.     

大规模空气质量监测数据缺失处理方法实证研究

基于2016年1月至2021年7月的全国1654个国控监测点小时级的6种污染物空气质量监测数据,研究缺失值处理方法、效果及其影响.模拟实验表明交替最小二乘下的低秩矩阵插补算法相比于其他缺失值处理方法拥有更小的均方根误差、平均百分比误差,更高的相关系数和更快的运算速度,在大规模数据集上性能更优.实证分析表明应用文本方法得到的插补值是有效且合理的,缺失值插补前后污染物浓度评估值会有±10%以内的变化,插补后的数据集更加准确和完备.本文建议在基于空气质量监测数据研究时应先采用本文中的缺失数据处理方法,对监测数据中存在的缺失数据进行插补,提高研究所使用监测数据的完整性,保证相关计算结果的准确性和有效性.     

突发型大气污染源位置识别反演问题的数值模拟

在突发型大气污染事件中,能否根据临时监测数据对污染源的位置进行快速识别,对于城市大气污染源的控制管理以及改善城市空气质量意义重大.为了构建突发型大气污染源位置识别的空间反演算法,本文通过分析大气应急污染监测的临时采样数据,结合污染物浓度扩散模型,随机生成污染源和计算污染物浓度的空间分布,对突发型大气污染源进行定位并与实际测量结果进行对比分析,采用蒙特卡洛模拟(Monte Carlo simulation)对相关参数进行讨论,最终构建能对突发型大气污染源进行快速估计定位的空间反演算法.研究结果表明,本文构建的空间反演算法输出的污染源坐标与实际情况相符.因此,该算法可用于突发型大气污染源位置的快速识别.     

缺失烟囱参数估算及其应用对空气质量模拟结果的改进

针对源清单中部分点源烟囱参数缺失而采用源排放模型SMOKE(Sparse Matrix Operator Kernel Emissions)默认的烟囱参数对空气质量模型模拟结果造成的不利影响,综合考虑气象观测数据、空气质量监测数据、源排放强度以及相关标准和规范对烟囱设计的要求,分别基于最大落地浓度法和基于统计方法对2009年珠三角地区源清单中缺失烟囱参数点源的烟囱参数进行了估算,并将估算烟囱参数用在WRF/SMOKE-PRD/CMAQ空气质量模型系统分析其对模型模拟的改善情况.相比于采用SMOKE默认烟囱参数,基于最大落地浓度估算烟囱参数对NO2、NOx、SO2、PM10及O3的模拟结果均具有一定改善作用,而基于统计方法估算烟囱参数仅对SO2、O3的模拟结果有所提高.结果表明,使用基于最大落地浓度法估算得到的烟囱参数更为合理,使污染物的垂直排放分配更加合理,可以应用于空气质量模型输入源清单中缺失烟囱参数点源的估算,从而一定程度上改善空气质量模型的模拟效果.     

气温遥感估算方法研究综述

气温作为重要的气候资源之一,在植被长势、农业灾害和气候变化研究中发挥着举足轻重的作用。目前大尺度农业、气候模型都需要空间分布的气温作为输入参数。除了用有限的台站数据空间插值获取气温栅格化数据外,遥感技术更为连贯精细的气温空间观测提供了有力的数据支持。为服务区域尺度气温相关的科研及业务工作,论文首先介绍了目前国内外气温遥感估算的主要方法,包括简单统计法、高级统计法、温度-植被指数分析法（TVX法）、地表能量平衡法及大气温度廓线外推法。再根据实际应用需要,重点总结比较了最高、最低和平均气温及不同时空尺度气温的遥感估算特点。最后讨论了气温遥感估算在实际应用中存在的问题并探讨了未来的研究趋势。     

GPRS在环境空气质量自动监测中的应用

针对目前采用电话拨号方式进行数据通信的空气质量自动监测系统所存在的实时性差等问题,通过分析比较目前环境监控系统常用的几种通信方式的优缺点,提出了一种基于GPRS技术的空气质量监测数据通信系统,此系统主要由监测子站、传输网络和监控中心等部分组成,采用GPRS无线网络和Internet网络为通道来实现监测数据的远程传输和状态监控,以达到实时监控的目的。采用GPRS进行数据通信具有经济适用、永远在线、实时性好等优点。     

立木地上部分生物量模型的建立及其应用研究

根据杉木、马尾松、阔叶树３个树种（组）的样本资料，研究提出了一套建立立木生物量模型及其在区域性森林生物量资源清查中应用的有效方法，解决了总量与各维量间相兼容和生物量估计与森林蓄积量清查的立木材积估计相兼容的问题，而且使模型的精度和适用性相对于传统的二元立木生物量模型有明显提高。     

立木地上部分生物量模型的建立及其应用研究

根据杉木、马尾松、阔叶树３个树种（组）的样本资料,研究提出了一套建立立木生物量模型及其在区域性森林生物量资源清查中应用的有效方法,解决了总量与各维量间相兼容和生物量估计与森林蓄积量清查的立木材积估计相兼容的问题,而且使模型的精度和适用性相对于传统的二元立木生物量模型有明显提高。     

广州市环境空气监测与预警体系在亚运会中的应用

本文以2010年广州亚运会空气质量监测保障为例,从广州市环境空气质量监测网络、空气质量预报、预警体系和环境质量会商及信息发布管理机制等方面,介绍了广州市环境空气监测与预警体系。通过2010年广州亚运会空气质量保障监测实践,证明广州市环境空气监测与预警体系是适应广州环境保护工作发展,并能满足特殊环境空气质量保障目标需求,具有示范作用和可供全国中心城市借鉴的先进的环境空气质量监测与预警体系。     

基于GA-ANN改进的空气质量预测模型

基于人工神经网络的空气质量预测模型优于传统的逐步回归模型,但由于性能差异不明显而较少在空气质量预报中应用. 设计了将遗传算法和神经网络算法相结合的基于GA_-ANN的空气质量预测模型,并利用天津市2003—2007年气象和污染物监测资料对该模型进行验证. 对2007年全年的ρ(SO₂),ρ(NO₂)和ρ(PM₁₀₎进行预测,预测值与实测值的相关系数分别为0.899 6,0.828 3和0.600 0. 与一般的人工神经网络预测模型相比较,GA_-ANN模型将空气质量等级预报的准确率从77.57%提高到79.67%. GA_-ANN模型可结合其他方法进行日常空气质量预报.      

哈尔滨市燃煤期PM10和PM2.5比对测试研究

哈尔滨市的地域性决定了气候非常具有代表性。以冬季特为明显,气温早晚温差大,气温低。再加上正是采暖期间,空气质量受供暖期等影响较大,空气质量不稳定。2013年冬季选择哈尔滨市燃煤期PM10和PM2.5比对测试研究分析,对市区内3个监测点位进行的颗粒物（PM10和PM2.5）手工采样与自动仪器的比对监测,以手工监测方法为基准,分析自动监测与手工监测的一致性,并对PM10和PM2.5浓度的比值关系进行了分析,结果表明：监测3个点位的PM10和PM2.5的浓度趋势具有很高的一致性,且以手工和自动数据进行线性回归的各项参数均符合技术规范（HJ 653-2013）的要求。     

南京市环境空气质量与气象条件的关系分析

统计了2005年10月至2006年10月13个月的空气质量监测数据以及相关的气象参数（风向、风速）进行分析,找出南京市环境空气污染物的来源与重点工业区污染源的关系。     

Unified wet deposition data summaries for North America: Data summary procedures and results for 1980–1986

This paper presents a framework for data quality assessment of annual and seasonal precipitation chemistry data summaries. Consideration has been to (i) using data from regional or national networks with established quality assurance/quality control programs and well documented network operation protocols, (ii) assessing regional representativeness of each sites, (iii) determining quantitative measures to define data completeness levels, and (iv) documenting the calculation procedures used to compute precipitation-weighted mean concentrations and wet deposition amount. The procedures described here are applied to data collected from 1980 to 1986 by five major acid deposition monitoring networks in North America and examples of annual sulfate deposition summaries are reported. It is recommended that the concepts of site representativeness, data completeness and overall data quality levels be adopted by the user community and routinely be reported along with a data summary. Further work on assesing accuracy and precision to accompany the data quality levels is recommended.     

关中地区城市空气质量特征及影响因素分析

本文对陕西省关中地区33个城市环境空气质量自动监测站点2015年全年的监测数据进行统计和研究,讨论了关中城市空气质量特征和主要影响因素。结果表明,关中地区城市间空气质量具有密切的相关性和整体性,影响关中城市群全年空气质量最主要的污染因子是可吸入颗粒物(PM10)和细颗粒物(PM2.5),首要污染物呈现出显著的季节变化规律。人类活动、气象因素以及地形特征是造成关中地区空气质量现状的主要原因。     

Trends analysis of vegetation exposure indices in rural areas of the U.S.

In this work, statistical models based on a linear time term are tested to determine if they can adequately represent the behavior over time of indices that relate vegetation exposure to air pollutants at a large number of monitoring sites in the rural U.S. Three pollutants are addressed: ozone (O₃), sulfur dioxide (SO₂)and nitrogen dioxide (NO₂. The formulations selected to generate the values of the exposure indices were the sum of all hourly average concentrations (SUM0); in addition, for O₃, the sum of all hourly average concentrations weighted with a sigmoidal function, which assigned larger weights to the higher concentrations. The basic hourly average concentration data were selected from routine air monitoring stations of existing networks that met minimum criteria for quality assurance and data completeness. The statistical methodology used was based on a linear regression model which accounted for seasonality and changes in experimental procedures. An additional lag-one autoregressive term was added to the model for those stations which exhibited significant autocorrelation in the data, based on the Durbin-Watson statistic. Long-term analyses included data for 7 to 10 years; short-term analyses included data for 4 to 5 years. Results show that over rural areas of the U.S., these models do not adequately represent the behavior of vegetation exposure indices, both in the long-term and the short-term analyses; the majority of stations did not have statistically significant (5% level) coefficients for the term representing linear dependence on time. Emissions data for SO₂, NO_x and volatile organic compounds (VOC) over the same time period are also presented. Over the contiguous U.S., emissions between 1979 and 1987 have decreased by a maximum of 3%; emission changes for individual states have generally decreased between 1979 and 1987, but between 1983 and 1987 both increases and decreases have occurred.     

AQI vs API——新老空气质量标准之对比

对昆明市空气质量监测数据分别用空气质量污染指数（API）和空气质量指数（AQI）做评价,并进行比较。叙述了测点小时数据、测点日均数据和城市日均数据对应的空气质量及区别。环保部和云南省环保厅分别发布的昆明市空气质量差别是由于评价空气质量的标准不同所致。     

基于PM2.5监测点空间聚类的关中五市空气污染区域识别

区域大气污染联防联控是空气质量管理的重要举措,准确识别空气污染区域对联防联控措施有重大意义.本研究采用陕西省关中五市（西安、咸阳、宝鸡、渭南、铜川）国控和省控全部90个监测点的小时级PM_2.5浓度监测数据,运用邻接约束层次聚类方法对监测点进行空间聚类,并利用泰森多边形和曲线平滑等技术识别空气污染区域.结果表明：1关中五市空气污染存在跨行政区划的区域性特征,本研究识别出2个特征显著不同的空气污染区域（区域1和区域2）;2区域2的PM_2.5浓度在统计上显著高于区域1,且重度和严重污染天数也显著高于区域1;3空气污染区域与地形特征关系密切,区域1均为高海拔区县,而区域2均为低海拔区县.依据空气污染区域的不同特征,在区域污染程度存在显著差异时,应当采取不同等级的污染防控措施,以减少对关中五市43%的国土面积、23个区县、639万人及3355亿元国内生产总值的影响,使区域空气污染防控措施更加科学、合理与精准.同时,空气污染区域的划分对缺失数据和不同空气污染等级表现稳健.     

An analysis of the long-term trend in ozone data from two Houston,Texas monitoring sites

This paper uses the theory of extreme values to estimate the long-term trend in the probability that ozone measurements made at two monitoring sites in Houston, TX exceed a threshold level specified by the U.S. Environmental Protection Agency (EPA). In addition, a bootstrap testing procedure is used to test if the trend is statistically significant. The analysis takes into account the correlation in the series of daily ozone readings, seasonality in the data, and missing values in the ozone series. The empirical results indicate a downward trend in the probability of exceeding the EPA's specified threshold level at both sites. However, the magnitude of the downward trend is much greater at one site than at the other, even though both sites are in Houston. In fact, hypothesis testing results suggest that only one site has a statistically significant trend in the long-term probability of an exceedance.     

An optimized approach for estimating benzene in ambient air within an air quality monitoring network

Benzene is a carcinogenic air pollutant for which European legislation has set an annual limit and criteria for the number of fixed monitoring sites within air quality networks（AQMN）. However, due to the limited number of fixed sites for benzene measurement, exposure data are lacking. Considering the relationship between benzene levels and other variables monitored within an AQMN, such as NO₂, O₃, temperature, solar radiation, and accumulated precipitation, this study propo...     

Diversity trends in Neogene European ungulates and rodents: large-scale comparisons and perspectives

The ungulate and rodent fossil records are often used independently to understand mammalian evolutionary history. Few studies have directly compared both records over long time periods and large geographic areas. Here, we compiled two datasets of European fossil localities containing rodents and/or ungulates over 20 My (Early Miocene–Early Pliocene) and processed the data with the same methodology. We counted the raw diversity and calculated a measure of evenness (Pielou’s index). After controlling for potential biases on diversity estimators, we identify the evenness index as a more reliable estimator bringing interesting insights into the way both mammal groups are structured by biotic or abiotic factors. In this study, we consider that an uneven distribution of the species richness among families, when only some families successfully diversify within the “continental-scale community”, represents a lower adaptability of this community to the environmental context. Pielou’s index is used to estimate this adaptability through time. The responses of ungulates and rodents to environmental changes are very divergent, especially facing the climatic changes known since the Middle Miocene. The general patterns suggest that rodent broad-scale assemblages are affected by all kinds of perturbations, even short biotic and abiotic events, but show a better adaptability when facing long-term abiotic changes. Unlike rodents, the ungulate assemblages show more stability in periods of relative environmental stability but show less adaptability to long-term climatic changes. Life-history traits of mammals can help explain patterns of diversity and biogeography at different spatial scales and may probably partly explain the opposite patterns evidenced here.