An on-line instrument for mobile measurements of the spatial variability of hexavalent and trivalent chromium in urban air

The Steam-Jet Aerosol Collector-long Pathlength Absorbance Spectroscopy (SJAC-LPAS), an on-line continuous instrument for mobile measurements of spatial distribution of water-soluble hexavalent and trivalent chromium in ambient aerosols, has been developed and is presented here. The system collects particles with the SJAC and analyzes the collected sample on-line using the diphenycarbazide (DPC) colorimetric method. By using a Teflon AF (Amorphous Fluoropolymer) liquid core wave guide, the limit of detection has been significantly improved, allowing on-line measurements at ambient concentrations. The limit of detection for Cr(VI) is 0.2 ng m⁻³. Water-soluble Cr(III) can also be measured by oxidizing it to Cr(VI) in a parallel line using hydrogen peroxide before the detection with the DPC method. The concentration of Cr(III) is then determined as the difference between the two lines (Cr(VI) and Cr(VI) plus Cr(III)). The instrument was specifically designed to be used on a mobile platform to study spatial distribution of the pollutant within a city on a scale of 100 m. Special attention was given to the time resolution and the stability of the instrument performance under driving conditions. The time resolution of the instrument is 15 s. At a typical driving speed of 30 km h⁻¹ the instrument can detect variations in chromium concentration (“hot spots”) on the scale of about 150 m. The instrument has proven to operate reliably and capture temporal and spatial variability of Cr(VI) concentration during four mobile measurement campaigns in Wilmington, DE.     

城市水环境空间规划体系与方法研究

水环境空间规划是城市环境总体规划的一个重要组成部分,文章基于试点城市实践经验和发达国家先进经验,将水环境空间规划按照"控制单元划分-空间分级管控-质量改善策略"三步走的战略进行了梳理。基于控制单元划分结果,对水环境的重要性和敏感性进行评价,划定分级管控方案,以期保护良好的水生态状况。基于大量的控制单元数据分析,明确空间差异化的控制单元质量改善策略。     

Managing the rural–urban transformation in East Asia in the 21st century

This article explores the special features of the rural–urban transformation in East Asia in the last 30 years within the broader context of the development strategies of Asian governments. Despite an ongoing commitment to the rhetoric of concern with rural development, food security and the alleviation of rural poverty, these policies have emphasised the important role of urbanisation as the prime process influencing economic growth. This is supported by the economic argument that the economies of scale, the creation of mass urban markets and the higher productivity that occur in urban places make them crucial to development. This paper argues that this approach creates a false dichotomy between rural and urban areas, whereas development should aim to increase the linkages between rural and urban areas aimed at producing societal transformations rather than separate rural and urban transitions. The paper then explores the empirical evidence of rural–urban transitions in East Asia with a more detailed case study of China, which is considered to be a crucial example because of the size of its population, the special conditions of market socialism and its institutional capacity to manage the rural–urban transformation. The final section focusses on the importance of developing spatial sensitivity to the management of the rural–urban transformation in the 21st century. Old divisions between rural and urban sectors must be replaced by planning that integrates urban and rural activities so that they adopt sustainable management strategies which utilise concepts of eco-systems in which rural and urban activities are linked, so as to create sustainable urban regions, cities and societies.

The effect of motorcyclists’ age on injury severities in single-motorcycle crashes with unobserved heterogeneity

Introduction: Due to the myriad of unique characteristics associated with motorcycle operation, motorcycle safety is a public health concern as complex as it is serious. National crash data suggest motorcyclists are 28 times more likely to be killed when compared to passenger car occupants. In the state of Florida, motorcycle crashes are 1.5 times more likely to result in the death of the rider, placing Florida among the top deadliest states for motorcyclists in the nation. Using police-reported data from 2016, this study addresses the complex and interconnected nature of the many characteristics associated with motorcycle operation by investigating the effect of age on motorcyclists’ riding behavior as it relates to injury severity for single-motorcycle crashes in the state of Florida. Method: To account for unobserved heterogeneity in the crash data, mixed logit models with heterogeneity in means and variances were estimated to model three injury severity outcomes (non-visible, severe, and fatal) for three age groups (under 30, 30–49, and 50 and above). Results: Model results indicate that age affects motorcyclists’ safety perception and ability to assess risks, thereby influencing their involvement in risky behaviors. Characteristics unique to motorcycle operation—spatial characteristics, speed, motorcycle type, time of day, helmet usage, alcohol consumption, ejection from motorcycle, passenger presence, endorsement status, and lighting—are further complicated by their dependency on the characteristics of the individual motorcyclist. Age of motorcyclist indicates a relationship between motorcyclists’ behavior and perceived safety. Conclusion: The model results indicated that statistically significant parameters constituted different models and they were not equal across the age groups of motorcyclists: aged under 30, aged 30–49, and aged 50 and above. Through advanced econometric modeling, this study fills a gap in the existing literature and assists the safety professionals, motorcycle trainers, policymakers, law enforcement agencies, and roadway designers in developing countermeasures.     

Highway safety assessment and improvement through crash prediction by injury severity and vehicle damage using Multivariate Poisson-Lognormal model and Joint Negative Binomial-Generalized Ordered Probit Fractional Split model

Introduction: Predicting crash counts by severity plays a dominant role in identifying roadway sites that experience overrepresented crashes, or an increase in the potential for crashes with higher severity levels. Valid and reliable methodologies for predicting highway accidents by severity are necessary in assessing contributing factors to severe highway crashes, and assisting the practitioners in allocating safety improvement resources. Methods: This paper uses urban and suburban intersection data in Connecticut, along with two sophisticated modeling approaches, i.e. a Multivariate Poisson-Lognormal (MVPLN) model and a Joint Negative Binomial-Generalized Ordered Probit Fractional Split (NB-GOPFS) model to assess the methodological rationality and accuracy by accommodating for the unobserved factors in predicting crash counts by severity level. Furthermore, crash prediction models based on vehicle damage level are estimated using the same two methodologies to supplement the injury severity in estimating crashes by severity when the sample mean of severe injury crashes (e.g., fatal crashes) is very low. Results: The model estimation results highlight the presence of correlations of crash counts among severity levels, as well as the crash counts in total and crash proportions by different severity levels. A comparison of results indicates that injury severity and vehicle damage are highly consistent. Conclusions: Crash severity counts are significantly correlated and should be accommodated in crash prediction models. Practical application: The findings of this research could help select sound and reliable methodologies for predicting highway accidents by injury severity. When crash data samples have challenges associated with the low observed sampling rates for severe injury crashes, this research also confirmed that vehicle damage can be appropriate as an alternative to injury severity in crash prediction by severity.     

Biomonitoring airborne parent and alkylated three-ring PAHs in the Greater Cologne Conurbation II: Regional distribution patterns

The spatial distribution of an important air pollutant class, three-ring polycyclic aromatic hydrocarbons and their derivatives (PAH-3), has been monitored for the Greater Cologne Conurbation (GCC) using pine needle as passive samplers. The GCC comprises one of the most heavily populated, trafficked, and industrialized regions in Germany. Here, 71 locations covering 3600 km² were sampled and, for the first time, isopleths maps constructed to investigate the regional variability in PAH-3 concentration and composition. The highest PAH-3 loads on needles (1000-1500 ng g⁻¹) were detected downwind of three lignite fuelled power plants, followed by Cologne City (600-700 ng g⁻¹) and smaller towns (400-600 ng g⁻¹), whereas rural and forest regions yielded PAH-3 loads of 60-300 ng g⁻¹. PAH-3 ratios facilitated source reconciliation, with high dibenzothiophene versus retene values indicating lignite combustion and high 9/(9 + 1)-methylphenanthrene ratios depicting traffic emissions in inner cities. PAH-3 ratios depended on topography and outlined the heavily industrialized Rhine Valley, demonstrating atmospheric dispersal of PAH-3.     

中国城市人口规模、产业集聚与碳排放

基于2009~2018年中国286个地级市面板数据，构建空间计量模型，从城市人口规模和产业集聚的综合视角探讨对于人均碳排放的影响机制.结果显示：不同城市的人均CO₂排放具有显著的空间溢出效应；城市人口规模和产业集聚与人均CO₂排放之间均呈“倒U型”关系，且影响机制各不相同；产业集聚与城市人口规模在影响碳排放上具有协同效应；中国东中西地区及南北地区在碳排放及其影响机制上具有显著差异；地区差异、经济发展程度差异等一系列稳健性检验均验证了上述结论的可靠性.因此各地政府在制定可持续发展政策时要针对城市人口规模、产业集聚和低碳统筹发展，合理制定人口、产业和节能减排政策.     

Criminal directionality and the structure of urban form

Spatial criminology has three interrelated elements: place, distance, and direction. Though directionality has had theoretical support for many years, very few empirical verifications of this component of crime have emerged. In this article, we investigate the strength of directionality by comparing a simulated randomized dataset and a large incident-based dataset of repeat offenders. We find strong evidence for a strong presence of directionality in criminal spatial decision-making. This aspect of the spatiality of crime must be considered in any attempts to understand the aetiology of crime.     

地球磁场大面积短暂异常与灾害性天气相关性初探

本文利用全国88个磁观测站提供的1990年10月1日～1991年8月31日期间地球磁场绝对强度值,进行空间线性相关分析,发现1990年11月～1991年1月,部分地区发生地磁异常,即相关系数|r_2|值(乘以因子100后)由正常值明显下降至10～40左右。而4～8个月后,地磁异常区与该地区发生的气象灾害有很好的对应关系.     

Effects of interpolation and data resolution on methane emission estimates from rice paddies

Rice paddies are an important source of the greenhouse gas methane (CH₄). Global methane emission estimates are highly uncertain and do not account for effects of interpolation or data resolution errors. This paper determines such scaling effects for the influence of soil properties on calculated CH₄ emissions for the island of Java, Indonesia. The effects of different interpolation techniques, variograms and neighbor optimization were tested for soil properties by cross-validation. Interpolated organic carbon values were not significantly different from the original soil samples, in contrast to interpolated soil iron contents. Interpolation of soil properties coupled to a process-based model on CH₄emissions led to a significant change in distribution of calculated CH₄ emissions, i.e., the variance decreased. Effects of data resolution were examined by interpolating soil properties to derive data at different data resolutions and then calculating CH₄ emissions by applying the process-based model at these resolutions. The soil properties did not differ significantly for different data resolutions, in contrast to calculated CH₄ emissions. These scaling effects were caused by the combination of interpolation and a non-linear model. Real scaling effects may even be larger because small-scale variability was not accounted for. Scaling effects, including those caused by small-scale variability, have to be considered to achieve unbiased and less uncertain global CH₄emissions estimates from rice paddies.