对环境水体中目标化合物——杀虫剂的快速、灵敏的飞行时间（TOF）筛查

飞行时间（TOF）筛查方式技术以其特有的优势,如全扫描数据采集、非预期化合物历史数据再查询等在环境监测领域的应用已经取得了稳步增长.满足全球食品需求,杀虫剂、除草剂和杀真菌剂使用泛滥.这些化学物质施用到庄稼上,将不可避免地污染土壤和河道.因此需要执行严格的环境监察,以保护环境、植物和野生动物     

Options for Managing Hypoxic Blackwater in River Systems: Case Studies and Framework

Hypoxic blackwater events occur when large amounts of organic material are leached into a water body (e.g., during floodplain inundation) and rapid metabolism of this carbon depletes oxygen from the water column, often with catastrophic effects on the aquatic environment. River regulation may have increased the frequency and severity of hypoxic blackwater events in lowland river systems, necessitating management intervention to mitigate the impacts of these events on aquatic biota. We examine the effectiveness of a range of mitigation interventions that have been used during large-scale hypoxic blackwater events in the Murray–Darling Basin, Australia and that may be applicable in other environments at risk from hypoxic blackwater. Strategies for hypoxia mitigation include: delivery of dilution flows; enhancement of physical re-aeration rates by increasing surface turbulence; and diversion of blackwater into shallow off-channel storages. We show that the impact of dilution water delivery is determined by relative volumes and water quality and can be predicted using simple models. At the dilution water inflow point, localized oxygenated plumes may also act as refuges. Physical re-aeration strategies generally result in only a small increase in dissolved oxygen but may be beneficial for local refuge protection. Dilution and natural re-aeration processes in large, shallow lake systems can be sufficient to compensate for hypoxic inflows and water processed in off-channel lakes may be able to be returned to the river channel as dilution flows. We provide a set of predictive models (as electronic supplementary material) for estimation of the re-aeration potential of intervention activities and a framework to guide the adaptive management of future hypoxic blackwater events.     

ACCURACY AND CONSISTENCY OF WATER‐CURRENT MIETERS1

ABSTRACT: The measurement of discharge in natural streams requires hydrographers to use accurate meters that have consistent performance among meters of the same model. This paper presents the results of an investigation into the accuracy and consistency of four models of current meters‐Price Type‐AA, Price Pygmy, Marsh McBirney 2000, and Swoffer 2100. Test results for six meters of each model are presented. Variation of meter performance within a model is used as an indicator of consistency, and percent velocity error that is computed from a measured reference velocity is used as an indicator of meter accuracy. Velocities measured by each meter are also compared to the manufacturer's published or advertised accuracy limits. The investigation found the Price models to be more accurate and consistent than the other models. The Price models met their respective accuracy limits over the range of test velocities better than the other models. The Marsh McBirney model usually measured within its accuracy specification. The Swoffer meters did not meet the stringent Swoffer accuracy limits for all the velocities tested. The Swoffer model had accuracies similar to the Price Type‐AA model when individual meter rating equations were computed and used. Every model tested had meters that did not meet manufacturer accuracy limits. Because current meters are not consistently accurate within a model, hydrographers should periodically check meters against a velocity standard.     

Driver injury severity related to inclement weather at highway–rail grade crossings in the United States

Objective: Previous studies on crash modeling at highway–rail grade crossings were aimed at exploring the factors that are likely to increase the crash frequencies at highway–rail grade crossings. In recent years, modeling driver's injury severity at highway–rail grade crossings has received interest. Because there were substantial differences among different weather conditions for driver's injury severity, this study attempts to explore the impact of weather influence on driver injury at highway–rail grade crossing.

Method: Utilizing the most recent 10 years (2002–2011) of highway–rail grade crossing accident data, this study applied a mixed logit model to explore the determinants of driver injury severity under different weather conditions at highway–rail grade crossing.

Results: Analysis results indicate that drivers' injury severity at highway–rail grade crossings is strongly different for different weather conditions. It was found that the factors significantly impacting driver injury severity at highway–rail grade crossings include motor vehicle speed, train speed, driver's age, gender, area type, lighting condition, highway pavement, traffic volume, and time of day.

Conclusions: The findings of this study indicate that crashes are more prevalent if vehicle drivers are driving at high speed or the oncoming trains are high speed. Hence, a reduction in speed limit during inclement weather conditions could be particularly effective in moderating injury severity, allowing more reaction time for last-minute maneuvering and braking in moments before impacts. In addition, inclement weather-related crashes were more likely to occur in open areas and highway–rail grade crossings without pavement and lighting. Paved highway–rail grade crossings with installation of lights could be particularly effective in moderating injury severity.     

Effects of macrophyte functional group richness on emergent freshwater wetland functions

Most plant diversity-function studies have been conducted in terrestrial ecosystems and have focused on plant productivity and nutrient uptake/retention, with a notable lack of attention paid to belowground processes (e.g., root dynamics, decomposition, trace gas fluxes). Here we present results from a mesocosm experiment in which we assessed how the richness of emergent macrophyte functional groups influences aboveground and belowground plant growth and microbial-mediated functions related to carbon and nitrogen cycling, with an emphasis on methane (CH4) efflux and potential denitrification rates. We found that an increase in the richness of wetland plant functional groups enhanced belowground plant biomass, altered rooting patterns, and decreased methane efflux, while having no effect on aboveground plant production or denitrification potential. We hypothesize that the greater root production and increased rooting depth in the highest diversity treatments enhanced CH4 oxidation to a relatively greater degree than methane production, leading to an overall decrease in CH4 efflux across our plant functional group richness gradient.