EPISODIC SUSPENDED SEDIMENT TRANSPORT AND ELEVATED POLYCYCLIC AROMATIC HYDROCARBON CONCENTRATIONS IN A SMALL,MOUNTAINOUS RIVER IN COASTAL CALIFORNIA

Suspended sediment and organic contaminants were measured during a period of 2 years in the San Lorenzo River, central California, which discharges into the Pacific Ocean within the Monterey Bay National Marine Sanctuary, in an effort to quantify the potential environmental effects of storm events from a steep, mountainous coastal urban watershed. Most suspended sediment transport occurred during flooding caused by winter storms; 56% of the total sediment load for the 2‐year study was transported by the river during one storm event in January 2010. Concentrations of polycyclic aromatic hydrocarbons can exceed regulatory criteria during high‐flow events in the San Lorenzo River, and total annual polycyclic aromatic hydrocarbon load was on the order of 10 kg in water year 2010. These results highlight the importance of episodic sediment and contaminant transport in steep, mountainous coastal watersheds and emphasize the importance of understanding physical processes and quantifying chemical constituents in discharge from coastal watersheds on event‐scale terms. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.     

Anthropogenic and climatic influences over the past three centuries on characteristics of an Adirondack lake,Eastern North America

Fourth Lake is a drainage lake at 43°N, 74°W, from which a 37‐cm long mud‐water interface core was recovered. ²¹⁰Pb dating indicates the core spans ≈340 years, from the Little Ice Age through modern global warming. Diatom accumulation responds to anthropogenic watershed disturbances, declining slightly up‐core until a peak in the late‐1800s attributable to sediment and nutrient influx from logging and enlargement of the outlet dam. A dramatic decrease occurs ≈1900 as logging and lake filling ceased, and a smaller peak ≈1960 accompanies residential development. Similar changes occur in organic carbon accumulation, which ranges from 0.0038–0.024 mg cm^?2 year^?1, with generally decreasing values up‐core, punctuated by maximum values in the late‐1800s. Expressing diatoms as concentration, however, reveals a doubling up‐core that positively correlates with changes extending beyond the watershed, including Northern Hemisphere temperature, atmospheric CO₂ concentration and solar irradiance (R = 0.627, 0.675 and 0.400, respectively). A >50% increase in % organic carbon, from 3.8% to 5.9%, also positively correlates with these larger‐scale environmental conditions (R = 0.828, 0.830 and 0.832), while negative correlations with the extrabasinal records are exhibited by magnetic susceptibility (R = ?0.654, ?0.496, and ?0.660) and clay (R = ?0.770, ?0.762, and ?0.737). These changes are consistent with decreased sediment influx and reduced dilution of biogenous sedimentary components. In contrast to total diatoms, the accumulation of planktonic genus Asterionella displays a long‐term increase up‐core. Potential explanations include increasing duration of the ice‐free season or a shift in the timing of the spring bloom and a mismatch with abundance of predator(s). Asterionella also increases as a percentage of total diatoms, being positively correlated with extrabasinal conditions (R = 0.827, 0.774 and 0.674). This change occurs at the expense of many benthic genera and, over the past century, at the expense of tychoplanktonic genus, Aulacosiera. Heavily silicified, Aulacosiera requires strong mixing to remain within the epilimnion. Thus, its decline might result from increasing stratification caused by warming.     

梭锥管混浊流体分离装置流场PIV 测试及分析

利用粒子图像测速技术,测试了两种工况下梭锥管混浊流体分离装置（简称梭锥管）内的水沙两相流的速度场,给出了梭锥管内泥沙运动的流速矢量分布及流速大小云图。对测试结果的分析表明,实测结果与理论分析结果一致。含沙水流进入梭锥管后,其内设置的多层锥圈把泥沙沉降区域分割成若干个沉降距离较短且相互独立的沉降空间,缩短了泥沙的自由沉降距离。相邻锥圈组成的水沙分离空间内,形成了沿锥圈上表面向下运动的泥沙流和沿锥圈下表面向上运动的清水流,使分离后的泥沙流和清水流沿各自独立路径流动,泥沙流流入排沙装置中心的排沙通道,而清水流流入装置边壁处的清水流通道,相互之间无混掺和干扰,加快了水沙分离速度。     

Evaluation of suspended load transport rate using transport formulas and artificial neural network models （Case study： Chelchay Catchment）＊

Accurate estimation of sediment load or transport rate is very important to a wide range of water resources projects. This study was undertaken to determine the most appropriate model to predict suspended load in the Chelchay Watershed, northeast of Iran. In total, 59 data series were collected from four gravel bed-rivers and a sand bed river and two depth integrating suspended load samplers to evaluate nine suspended load formulas and feed forward backpropagation Artificial Neural Network (ANN) structures. Although the Chang formula with higher correlation coefficient (r = 0.69) and lower Root Mean Square Error (RMSE = 0.013) is the best suspended load predictor among the nine studied formulas, the ANN models significantly outperform traditional suspended load formulas and show their superior performance for all statistical parameters. Among different ANN structures two models including 4 inputs, 4 hidden and one output neurons, and 4 inputs, 4 and one hidden and one output neurons provide the best simulation with the RMSE values of 0.0009 and 0.001, respectively.     

Modeling and analysis of effects of precipitation and vegetation coverage on runoff and sediment yield in Jinsha River Basin

This paper focuses on the effects of precipitation and vegetation coverage on runoff and sediment yield in the Jinsha River Basin. Results of regression analysis were taken as input variables to investigate the applicability of the adaptive network-based fuzzy inference system (ANFIS) to simulating annual runoff and sediment yield. Correlation analysis indicates that runoff and sediment yield are positively correlated with the precipitation indices, while negatively correlated with the vegetation indices. Furthermore, the results of stepwise regression show that annual precipitation is the most important factor influencing the variation of runoff, followed by forest coverage, and their contributions to the variation of runoff are 69.8% and 17.3%, respectively. For sediment yield, rainfall erosivity is the most important factor, followed by forest coverage, and their contributions to the variation of sediment yield are 49.3% and 24.2%, respectively. The ANFIS model is of high precision in runoff forecasting, with a relative error of less than 5%, but of poor precision in sediment yield forecasting, indicating that precipitation and vegetation coverage can explain only part of the variation of sediment yield, and that other impact factors, such as human activities, should be sufficiently considered as well.     

基于虚拟仪器的底质声学测试系统设计

为解决在不具备海洋远洋原位测试的情况下仍然需要对沉积物进行还原海底环境声学测试的问题,将虚拟仪器技术应用于沉积物测试中,建立可以在实验室中还原海底环境的声学测试系统。采用虚拟仪器智能判断首波的方法测试沉积物在相应环境的声速,应用虚拟仪器频谱分析技术实现对超声波信号的滤波及分析,利用Labview工具编写软件实现超声测试与温度和压力的测量与控制同步。建立小尺度地质物理模型可以通过对海洋底质沉积物样品施以温度、压力控制,在实验室内还原海底特殊环境,同时对沉积物样品进行超声无损探测。在测试系统平台上对远洋获取的沉积物进行声速测试实验,对比传统方法测试实验,实验结果表明测试系统操作简单、可还原样品环境、实用性强。     

湖泊沉积物对17β雌二醇的降解效能

沿湖泊沉积物垂直高度取表层（SL,0～2cm）、中层（ML,14～16cm）、底层（BL,28～30cm）3层底泥微生物为对象,研究了湖泊沉积物对17β-雌二醇（17β-estradiol,E2）的生物降解效能。结果表明：无论在好氧还是厌氧条件下,E2及其副产物雌激素酮（estrone,E1）的降解行为与沉积物沉积深度和环境温度有密切关系：底泥沉积深度愈深,E2降解速率愈低;在微生物活性温度范围内,环境温度愈高,E2降解速率愈高。好氧条件下,湖泊沉积物中E2降解反应的k值为0.002～0.120h^-1·g^-1·L;厌氧条件下,k值为0.002～0.057h^-1·g^-1·L。由于诱导驯化及有机物竞争关系减小等原因,向反应体系中再次添加E2后,其k值增大约34%。湖泊沉积物中硝化细菌的存在对E2降解具有促进作用。     

水流含沙量和流速对水轮机磨蚀性能的影响

水流含沙量和流速是影响水轮机磨蚀性能的非常重要的两大因素,其影响规律对水轮机磨蚀的防治有很重要的理论意义和参考价值.采用黄河原型沙,通过试验研究不同泥沙含量和不同水流流速条件下水轮机材料的磨蚀外貌、磨蚀失重量和磨蚀失重率.通过对试验结果进行定性和定量分析,得到水轮机磨蚀与水流含沙量、磨蚀与水流流速之间的关系,并得到数学回归式,找出水轮机磨蚀的基本规律,为多泥沙河流水轮机的参数选择与磨蚀防治提供了依据.     

冲积河流稳定平衡条件与断面几何形态的数理分析

冲积河流稳定平衡条件长期以来被认为无闭合解,致使众多经验假说得以应用。本文通过将两个无量纲断面形态参数宽深比和边坡角度引入到冲积河流三大基本运动方程中,详细分析了推移质输沙率与这两个变量之间的复杂关系,从数学上推导得出冲积河流达到稳定平衡的水动力学条件是推移质输沙率最大。河流达到稳定平衡时的过水断面形态数学表达式表明,天然冲积河流在平滩水位时所展现的水力几何关系是河流通过调整过水断面形态达到的稳定平衡的结果。