Integration of air pollution data collected by mobile sensors and ground-based stations to derive a spatiotemporal air pollution profile of a city

ABSTRACT

Air pollution has become a serious environmental problem causing severe consequences in our ecology, climate, health, and urban development. Effective and efficient monitoring and mitigation of air pollution require a comprehensive understanding of the air pollution process through a reliable database carrying important information about the spatiotemporal variations of air pollutant concentrations at various spatial and temporal scales. Traditional analysis suffers from the severe insufficiency of data collected by only a few stations. In this study, we propose a rigorous framework for the integration of air pollutant concentration data coming from the ground-based stations, which are spatially sparse but temporally dense, and mobile sensors, which are spatially dense but temporally sparse. Based on the integrated database which is relatively dense in space and time, we then estimate air pollutant concentrations for given location and time by applying a two-step local regression model to the data. This study advances the frontier of basic research in air pollution monitoring via the integration of station and mobile sensors and sets up the stage for further research on other spatiotemporal problems involving multi-source and multi-scale information.     

The role of the sediment budget in understanding debris flow susceptibility

This study proposes a sediment‐budget model to predict the temporal variation of debris volume stored in a debris‐flow prone watershed. The sediment‐budget is dominated by shallow landslides and debris outflow. The basin topography and the debris volume stored in the source area of the debris‐flow prone watershed help evaluating its debris‐flow susceptibility. The susceptibility model is applied to the Tungshih area of central western Taiwan. The importance of the debris volume in predicting debris‐flow susceptibility is reflected in the standardized coefficients of the proposed statistical discriminant model. The high prediction rate (0·874) for the occurrence of debris flows justifies the capability of the proposed susceptibility models to predict the occurrence of debris flows. This model is then used to evaluate the temporal evolution of the debris‐flow susceptibility index. The analysis results show that the numbers of watershed which are classified as a debris‐flow group correspond well to storage of sediment at different time periods. These numbers are 10 before the occurrence of Chi‐Chi earthquake, 13 after the occurrence of Chi‐Chi earthquake, 16 after the occurrence of landslides induced by Typhoon Mindulle (Typhoon M), and 14 after the occurrence of debris flows induced by Typhoon M. It indicates that the occurrence of 7·6 Chi‐Chi earthquake had significant impact on the debris flow occurrence during subsequent typhoons. Copyright © 2009 John Wiley & Sons, Ltd.     

Assessment of design rainfall uncertainty for hydrologic engineering applications in Hong Kong

Hydrologic engineering designs and analyses often require the specification of design storm which involves rainfall amount, duration and hyetograph. In practice, the determination of design rainfall in hydrologic engineering applications involves the frequency analysis of extreme rainfalls of different durations and the establishment of rainfall hyetograph for the design event under consideration. Sampling errors exist in the estimation of rainfall depth (or intensity) quantiles from frequency analysis, which will be transmitted in the process of determining the design rainfall hyetograph. This paper presents a practical methodological framework based on the bootstrap resampling scheme to assess the uncertainty features associated with the magnitude of estimated rainfall depth/intensity quantiles and the corresponding design hyetographs. The procedure is implemented to quantify uncertainty of design rainfall hyetograph following the Stormwater Drainage Manual of Hong Kong involving the use of rainfall intensity–duration–frequency (IDF) model. Of particular interesting is that the bootstrap resampling scheme implemented herein is modified to handle unequal record period of annual maximum rainfall data series of different durations and to account for their intrinsic correlations. According to the adopted rainfall IDF model, the design rainfall hyetograph is a function of the IDF model coefficients. Due to the correlation among rainfall quantiles of different durations, the IDF coefficients are found to be strongly related in a nonlinear fashion which should not be ignored in the establishment of the design hyetographs.     

Multi-criteria decision making under uncertainty for flood mitigation

Designs of flood mitigation infrastructural systems are decision-making which are often made under various uncertainties involving multiple criteria. Under the condition of uncertainties, any chosen design alternative has the likelihood to perform inferior to other unselected designs in terms of the adopted performance indicators. This paper introduces a quantitative risk measure based on the concept of expected opportunity loss (EOL) for evaluating the consequence of making the wrong decision. The EOL can be used to assess the relative performance of multiple decision alternatives and is extended to deal with decision problems involving multiple criteria. In particular, the probabilistic features of the consequences associated with a design alternative is considered and used in the Preference Ranking Organization Method of Enrichment Evaluation (PROMETHEE) MCDM technique. The integration of PROMETHEE and decision making under uncertainty is demonstrated through an example of flood damage mitigation planning.     

Variations of Microbial Communities and the Contents and Isotopic Compositions of Total Organic Carbon and Total Nitrogen in Soil Samples during Their Preservation

Semi-sealed preservation of soil samples at different moisture of 4% and 23%, respectively, was simulated to observe the variations of soil microbial communities and determine the contents and isotopic compositions of the total organic carbon and total nitrogen on the 7th and 30th day, respectively. The results show that during preservation, the quantity of microbial communities tended to increase first and then decrease, with a wider variation range at higher moisture (23%). At the moisture content of 23%, the microbial communities became more active on the 7th day, but less after 30 days, and their activity was stable with little fluctuation at the moisture content of 4%. However, there were no significant changes in the contents and isotopic compositions of the total organic carbon and total nitrogen. During preservation, the responses of soil microbes to the environment are more sensitive to changes in the total nitrogen and organic carbon contents. It is thus suggested that the variations of microbial communities have not exerted remarkable impacts on the isotope compositions of the total nitrogen and total organic carbon.     

Development of high‐performance shake tables using the hierarchical control strategy and nonlinear control techniques

Conventional shake tables employ linear controllers such as proportional‐integral‐derivative or loop shaping to regulate the movement. However, it is difficult to tune a linear controller to achieve accurate and robust tracking of different reference signals under payloads. The challenges are mainly due to the nonlinearity in hydraulic actuator dynamics and specimen behavior. Moreover, tracking a high‐frequency reference signal using a linear controller tends to cause actuator saturation and instability. In this paper, a hierarchical control strategy is proposed to develop a high‐performance shake table. A unidirectional shake table is constructed at the University of British Columbia to implement and evaluate the proposed control framework, which consists of a high‐level controller and one or multiple low‐level controller(s). The high‐level controller utilizes the sliding mode control (SMC) technique to provide robustness to compensate for model nonlinearity and uncertainties experienced in experimental tests. The performance of the proposed controller is compared with a state‐of‐the‐art loop‐shaping displacement‐based controller. The experimental results show that the proposed hierarchical shake table control system with SMC can provide superior displacement, velocity and acceleration tracking performance and improved robustness against modeling uncertainty and nonlinearities. Copyright © 2015 John Wiley & Sons, Ltd.     

Analysis of space–time patterns of rainfall events during 1996–2008 in Yilan County (Taiwan)

Stochastic Environmental Research and Risk Assessment - Understanding local precipitation patterns is essential to water resource management and flood mitigation. Precipitation patterns can vary in...     

The Badia programme:: defining and overcoming constraints on sustainable development

Since 1992 research on the Badia Programme, in north-east Jordan, has begun the process of identifying constraints on development and is suggesting where developmental potential still exists. Still, there are no proven development options to set alongside the traditional pastoralism. Perhaps in the future, service industries will provide the main additional employment opportunities, especially those serving the needs of international trade to and from Iraq and further east.     

Lacustrine sedimentological and geochemical records for the last 170 years of climate and environmental changes in southeastern China

Reconstruction of modern climate and environmental changes in east Asia using inland natural climate archives can provide valuable insights on decadal–multidecadal climate and environmental patterns that are probably related to both natural and anthropogenic forcing. Here we investigated an 89‐cm‐long sediment core (TH1) from Tian Lake, southeastern China, for sedimentological, physical and geochemical parameters in order to understand climate and environmental changes for the latest two centuries. ¹³⁷Cs‐ and ²¹⁰Pb‐based age models show that the fine sand–coarse silt‐dominated core contains ~170 years (c. AD 1842–2011) of continuous sedimentation. Sediments with fine sands, low MS values, high water content, high TOC content and a high C:N ratio from c. AD 1842 to 1897 suggest intense hydrological conditions and strong runoff in the catchment, probably because of a humid climate. From AD 1897 to 1990, sediments with very fine sand and coarse silt, high MS values, low water content and unchanged TOC and C:N ratios indicate normal hydrological conditions and in‐lake algae‐derived organic matter. During this interval, the chemical weathering indicators show stronger weathering conditions compared with sediments deposited during AD 1842–1897, supporting the dominance of weathered surface soil input in the earlier interval and physical erosion dominance in the later period, respectively. Since AD 1990, the continuous decrease of geochemical proxies suggests human‐interacted Earth surface processes in the catchment of Tian Lake. A PCA revealed four dominant geochemical controlling factors – detrital input, trophic status, grain size and early diagenesis –, accounting for 26, 20, 18 and 16% of total variance, respectively. This study for the first time provides lacustrine geochemical evidence for the most recent two centuries of climate and environmental changes in coastal southeastern China, a region that is currently undergoing an inversion of critical zone, i.e. an overturning of its soil profile, owing to swift modernization.