Large-scale turbulent structure of uniform shallow free-surface flows

The hydrodynamics of super- and sub-critical shallow uniform free-surface flows are assessed using laboratory experiments aimed at identifying and quantifying flow structure at scales larger than the flow depth. In particular, we provide information on probability distributions of horizontal velocity components, their correlation functions, velocity spectra, and structure functions for the near-water-surface flow region. The data suggest that for the high Froude number flows the structure of the near-surface layer resembles that of two-dimensional turbulence with an inverse energy cascade. In contrast, although large-scale velocity fluctuations were also present in low Froude number flow its behaviour was different, with a direct energy cascade. Based on our results and some published data we suggest a physical explanation for the observed behaviours. The experiments support Jirka’s [Jirka GH (2001) J Hydraul Res 39(6):567–573] hypothesis that secondary instabilities of the base flow may generate large-scale two-dimensional eddies, even in the absence of transverse gradients in the time-averaged flow properties.     

A Hierarchical Model for Estimating Long‐Term Trend of Atrazine Concentration in the Surface Water of the Contiguous U.S.

Atrazine is a herbicide frequently detected in both surface and groundwater in the United States (U.S.), but its spatiotemporal distribution and concentration trends have only been analyzed recently at regional or local scales. We employed a Bayesian hierarchical modeling approach to assess spatial and seasonal variation in atrazine concentration trends between 1990 and 2010 for the contiguous U.S. A Markov chain Monte Carlo simulation algorithm was used to address the problem of left‐censored data (i.e., atrazine concentration values below method reporting levels). We observed opposing temporal trends in the northern (flat or decreasing) and southern (increasing) regions of the U.S. This spatial variation in temporal trends can be partially explained by the relative amount of cropland in the region. Flat or decreasing trends in the north are more likely in regions with high cropland coverage while positive trends in the south are more likely in regions with low cropland coverage.     

利用PUF大气被动采样技术监测中国城市大气中的多环芳烃

利用PUF大气被动采样技术,分冬、春2个季度,对中国32个城市大气中的多环芳烃（PAHs）进行了观测.结果表明,除主要存在于气相中的2～3环PAHs与部分4环PAHs外,PUF被动采样器也可一定程度地采集大气颗粒物中的5～7环PAHs.中国城市大气PAHs的浓度与组成,主要受城市所处的地理位置、气候条件以及能源消费结构的影响.西北、华北、西南和华中地区部分城市大气中PAH总量和高环PAH浓度均较高,华南和东南沿海一带城市则相对较低.在季节变化上,表现为冬季浓度高、春季低.可能是陆源有机质在土壤中早期成岩作用的产物,春季浓度升高反映了土壤颗粒物对大气颗粒物的贡献,与扬尘天气相对应;而芴的浓度在燃煤较多的城市大气中显著增加,与其主要属燃煤成因相一致.研究表明,PUF大气被动器可很好地运用于区域大气PAH污染分布与特征对比研究.     

被动采样法观测研究京津冀区域大气中气态污染物

为了对京津冀区域的大气污染物进行观测,揭示污染物浓度和组分的时空分布和变化规律,深入了解区域复合型污染,从2007年12月开始使用造价低、操作简捷的被动采样方法对区域10个站点大气中的SO2、NO2、O3和NH3等主要污染物进行了监测,对被动采样方法的区域适用性进行了比较全面的评估并根据监测结果对污染物的浓度水平和区域分布进行了研究.方法适用性评估表明被动采样方法在污染较严重的京津冀区域能进行长时间采样,采样频率设定为每月1次;平行采样结果显示,SO2、NO2、O3和NH3的变异系数分别为6.4%、7.1%、4.2%和3.9%,方法表现出良好的稳定性;每月1次的被动采样浓度结果与主动采样仪器观测结果月平均值相比具有较好的一致性,SO2、NO2和O3这2种方法监测结果的相关系数达到0.91、0.88和0.93,拟合曲线斜率分别为1.25、0.98和0.93,平均相对标准偏差分别为23.3%、14.9%和8.5%,能基本满足大气采样的要求,NH3的短时监测也表明2种方法具有可比性.评估结果说明被动采样方法是一种可靠的大气污染监测方法,可用于区域污染的监测.2008年夏季京津冀区域10个站点SO2、NO2、O3和NH3的被动采样平均浓度分别(12.3±6.3)×10-9、(13.2±7.0)×10-9、(40.5±9.5)×10-9和(24.0±13.7)×10-9.浓度区域分布显示SO2和NO2在城市站点具有较高浓度,而NH3在农业站点的浓度较高,SO2、NO2和NH3的大气浓度水平明显受局地排放影响,浓度分布较直观的反应了站点的局地源排放;而O3除了背景站兴隆,在北京和天津周边的大小城市,平均浓度都在40×10-9左右,表现出区域协同污染特征.     

Inferring Hydrograph Components from Rainfall and Streamflow Records Using a Kriging Method-Based Linear Cascade Reservoir Model1

Cheng, Shin-jen, 2010. Inferring Hydrograph Components From Rainfall and Streamflow Records Using a Kriging Method-Based Linear Cascade Reservoir Model. Journal of the American Water Resources Association (JAWRA) 46(6):1171–1191. DOI: 10.1111/j.1752-1688.2010.00484.x Abstract: This study investigates the characteristics of hydrograph components in a Taiwan watershed to determine their shapes based on observations. Hydrographs were modeled by a conceptual model of three linear cascade reservoirs. Mean rainfall was calculated using the block Kriging method. The optimal parameters for 42 events from 1966-2008 were calibrated using an optimal algorithm. Rationality of generated runoffs was well compared with a trusty model. Model efficacy was verified using seven averaged parameters with 25 other events. Hydrograph components were characterized based on 42 calibration results. The following conclusions were obtained: (1) except for multipeak storms, a correlation between base time of the surface runoff and soil antecedent moisture is a decreasing power relationship; (2) a correlation between time lag of the surface flow and soil antecedent moisture for single-peak storms is an increasing power relationship; (3) for single-peak events, times to peak of hydrograph components are an increasing power correlation corresponding to the peak time of rainfall; (4) the peak flows of hydrograph components are linearly proportional to that of total runoff, and the peak ratio for the surface runoff to total runoff is approximately 78 and 13% for subsurface runoff to total runoff; and (5) the relationships of total discharges have direct ratios between hydrograph components and observations of total runoffs, and a surface runoff is 60 and 32% for a subsurface runoff.     

环境水体中油的采样工具的设计及其可行性研究

由于油在水中呈不均匀分布的特性,所以有关环境水体中油的采样工具,一直是环保部门关注的焦点。为此提出了“理想（或称假想）水柱”的概念,并依此设计出一种在环境监测工作中使用的便携式测水中油用采样器,适用于工业废水、生活污水及污染的地表水的采取。其特点是,一个底部可开闭的采样器,采样器中的采样瓶（包括瓶底衬盖、瓶底盖）与内拉杆、外套管通过螺纹联接,移动内拉杆、外套管,便可以方便地采取一定面积下的含油水柱。采样瓶装卸简单,运输方便,在实验室中可将其直接用作操作瓶。用这种采样器,计算结果将更接近真实情况。本装置已于９２ 年１２ 月３０日获国家发明专利,专利号：８９１０２４７１．９,证书号：１６３８１。     

无线遥控水质自动采样系统的研发与应用

针对现行废水污染源采样中存在的问题,综合应用无线通信、自动控制、信息处理等现代技术,研发无线遥控水质自动采样系统。该系统集常规采样、质控采样、比对采样、超标采样等功能于一体,并可实现采样全程的远程无线遥控,大大增强废水采样的客观性、代表性、公正性,提高工作效率和快速反应能力。     

基于标准雨量计的降水采样方法比较

对太原市2013年7—11月的大气降水使用标准雨量计、国产A型和进口B型自动降水采样设备进行同步记录,分析国产A型和进口B型设备采集降水样品的p H、电导率和无机阴阳离子。结果表明,进口B型设备采集降水样品的降雨量(155.35 mm)比标准雨量计记录值(117.50 mm)高32.21%,而国产A型设备采集降水样品的降雨量(107.12mm)比标准雨量计记录值低8.83%。7—9月的15场降水,国产A型设备采集大多数降水样品的电导率和离子加权浓度均值基本上低于进口B型设备,差异程度分别达65.51%和62.52%;而p H则基本上高于进口B型,酸雨比例差异程度为61.53%。     

树皮在大气有机氯农药监测中应用的研究进展

有机氯农药(Organochlorine pesticides,OCPs)曾在全世界被大量使用,即使禁用多年,仍能在各种环境介质中被广泛检出,对生态环境和人体健康存在着潜在的威胁。因此OCPs的环境迁移和归趋一直是该领域的研究热点。树皮是一种天然的被动采样器,能够很好的反映出大气有机物长期的污染程度。本文简要论述了树皮作为被动采样器在大气污染物监测研究中应用的优势,并对OCPs在树皮中的残留浓度、特征及影响其富集的因素进行了探讨,最后特别针对具有手性的OCPs在树皮中的对映体选择性特征进行了评述。