农业非点源污染国内外研究进展

农业非点源污染正日益成为水体富营养化最主要的污染源,并已成为当前限制我国经济可持续发展的重要因素。笔者从农业非点源污染物迁移转化机制、非点源污染物的防控机制、非点源污染模型模拟、农业非点源污染研究中的尺度问题等方面对国内外研究进展进行了论述。提出我国非点源污染研究需在以下方面有所加强：（1）非点源污染物耦合作用下的运移;（2）转化机理及其界面行为过程机制研究;（3）不同空间尺度和格局农业非点源污染物的迁移转化规律;（4）适合我国不同区域特色的非点源污染机理模型研究。     

Temporal variability in water quality of agricultural tailwaters: Implications for water quality monitoring

Accurate assessments of non-point source pollution and the associated evaluation of mitigation strategies depend on effective water quality monitoring programs. Intensive irrigation season water quality monitoring was conducted on three agricultural drains (6 h to daily sampling) along with analysis of decade long records from two larger agricultural drains (biweekly to monthly sampling) in the San Joaquin Valley, California. Analyses revealed significant temporal variability in concentrations of nutrients, salts, and turbidity over short time-scales (<1 day), as well as significant differences in monthly and annual mean concentrations. Statistical techniques were used to evaluate the sampling intensity required to meet rigorous confidence and accuracy criteria, as well as to evaluate the efficacy of different sampling strategies (e.g. grab samples versus composite samples). The number of samples required to determine mean constituent concentrations within 20% of the mean at a 95% confidence level ranged from 2 to 39 samples per month (SPM) for total phosphorus, 1-16 SPM for total nitrogen, 5-25 SPM for turbidity, and 1-3 SPM for electrical conductivity. Using a daily composite sample (4 subsamples per composite) instead of discrete samples was shown to maintain the same accuracy and confidence standards, while reducing the required sample number by up to 50%. This study emphasizes the value of a statistical approach for evaluating water quality monitoring strategies, and provides a framework through which cost-benefit analysis can be implemented in the development of monitoring plans.     

Water production functions of wheat (Triticum aestivum L.) irrigated with saline and alkali waters using double-line source sprinkler system

Expected yield losses as a function of quality and quantity of water applied for irrigation are required to formulate guidelines for the effective utilisation of marginal quality waters. In an experiment conducted during 2004-2006, double-line source sprinklers were used to determine the separate and interactive effects of saline and alkali irrigation waters on wheat (Triticum aestivum L.). The study included three water qualities: groundwater (GW; electrical conductivity of water, ECw 3.5 dS m⁻¹; sodium adsorption ratio, SAR 9.8 mmol L⁻¹; residual sodium carbonate, RSC, nil) available at the site, and two synthesized waters, saline (SW; ECw 9.4 dS m⁻¹, SAR 10.3 mmol L⁻¹; RSC nil) and alkali (AW; ECw 3.7 dS m⁻¹, SAR 15.1 mmol L⁻¹; RSC 9.6 meq. L⁻¹). The depths of applied SW, AW, and GW per irrigation ranged from 0.7 to 3.5 cm; the depths of applied mixtures of GW with either SW (MSW) or AW (MAW) ranged from 3.2 to 5 cm. Thereby, the water applied for post-plant irrigations using either of GW, SW or AW ranged between 15.2 and 34.6 cm and 17.1 and 48.1 cm during 2004-2005 and 2005-2006, respectively and the range was 32.1-37.0 and 53.1-60.0 cm for MSW or MAW. Grain yields, when averaged for two years, ranged between 3.08 and 4.36 Mg ha⁻¹, 2.57 and 3.70 Mg ha⁻¹ and 2.73 and 3.74 Mg ha⁻¹ with various quantities of water applied using GW, SW and AW, respectively, and between 3.47 and 3.75 Mg ha⁻¹ and 3.63 and 3.77 Mg ha⁻¹ for MSW and MAW, respectively. The water production functions developed for the two sets of water quality treatments could be represented as: RY = 0.528 + 0.843(WA/OPE) − 0.359(WA/OPE)² − 0.027ECw + 0.44 × 10⁻²(WA/OPE) × ECw for SW (R² = 0.63); RY = 0.446 + 0.816(OPE/WA) − 0.326(WA/OPE)² − 0.0124RSC − 0.55 × 10⁻⁴(WA/OPE) × RSC for AW (R² = 0.56). Here, RY, WA and OPE are the relative yields in reference to the maximum yield obtained with GW, water applied for pre- and post-plant irrigations (cm), and open pan evaporation, respectively. Crop yield increased with increasing amount of applied water for all of the irrigation waters but the maximum yields as obtained with GW, could not be attained even with increased quantities of SW and AW. Increased frequency of irrigation with sprinklers reduced the rate of yield decline with increasing salinity in irrigation water. The sodium contents of plants increased with salinity/alkalinity of sprinkled waters as also with their quantities. Simultaneous decrease in potassium contents resulted in remarkable increase in Na:K ratio.     

车内噪声分析与控制研

利用互易性原理,提出了一种空气声传播路径实验方法.首先测得各声源对于车内噪声的传递函数,进而得到各声源对于车内噪声的贡献度.根据声源识别结果,对汽车车身进行吸声、隔声设计,结果表明,车内地板隔声量从前向后分别提高了1.83～9.74 dB(A),汽车车内噪声下降了4.7 dB(A).     

无线传感器网络技术在养殖业污染监测上的应用

综述了国际上无线传感器网络技术发展的特点和趋势,提出无线传感器网络技术在畜禽和水产养殖业污染监测上应用需要解决的2个技术问题:一是选择合理的IP无线传输方式;二是选择合理的系统结构,达到较高的性价比。设计出适合不同地域、不同生态环境的无线传感器网络的拓扑结构,实现在户外或野外环境下对畜禽和水产养殖业污染的监测。     

辽东湾北部近海海域表层沉积物类型及分布特征

对2004年采自辽东湾北部近海海域的16个表层沉积物样品作了粒度分析和粒度参数计算,并进行了沉积物分类和分布特征的研究,结果表明,辽东湾北部近海的表层沉积物粒度主要由粉砂组成,平均含量65.15%,平均粒径5.031。总的特征是在5~10 m等深线,沉积物粒度的平均粒径由东部的4.530、中部的5.050逐渐增大到西部的6.236。沉积物粒度的组成类型由东向西按粉砂质砂→砂质粉砂→粉砂→砂-粉砂-黏土→黏土质粉砂由粗至细排列。     

小型自排沉沙池沉沙工况的水力学特性试验研究

首先介绍了小型自排沉沙池的工作原理与工作过程,然后以物理模型对小型自排沉沙的水力学特性进行试验研究,通过试验资料深入分析了小型自排沉沙池内水流的流态特征,流速分布等水力特性。试验研究旨在为进一步研究小型自排沉沙池沉沙工况提供依据。     

基于改进欧拉算法的双吸离心泵泥沙磨损特性研究

固液两相流算法对双吸离心泵泥沙磨损模拟精度有直接影响。采用改进的固液两相流欧拉算法,考虑了相间阻力和泥沙扩散系数两方面因素,对典型悬移质泥沙粒径条件下的双吸离心泵流场进行了数值计算。研究发现,叶片表面湍流强度在头部和尾部较大,可达6%~10%;叶片头部和尾部的颗粒动态尺度大于中部。由湍流强度和颗粒动态尺度组成的湍动尺度效应,在叶片头部和尾部表现强烈,湍动尺度效应使固液相间阻力增大,更有利于颗粒的扩散,避免了颗粒聚集,对大颗粒的作用强于小颗粒。湍动尺度效应导致叶片表面固相体积分数分布范围减小,大颗粒的变化值大于小颗粒,叶片头部和尾部的改变值大于中部,叶片表面的严重磨损部位为叶片工作面尾部的块状磨损区,这比采用传统算法得到的带状磨损区和偏磨区计算结果,更符合离心泵实际磨损情况,考虑湍动尺度效应后得到的磨损率也有所增大。在此基础上,提出了双吸离心泵叶片水力设计和表面喷涂防护原则,为提高双吸离心泵抵抗泥沙磨损能力奠定了基础。     

温室作业机具室内定位方法研究

针对农机具在温室大棚内的定位、作业轨迹跟踪及作业面积核算需求,提出一种基于多源数据融合理论的温室机具室内定位优化算法。首先根据惯性导航测量技术预估被测目标定位初值,再利用无线RSSI测距技术使用加权质心算法获得定位测量结果,利用卡尔曼滤波算法进行定位信息最优化计算,以消除基于单一测量技术存在数据漂移、测试信号受遮挡、电磁干扰造成的误差,获得准确的定位信息,进而实现作业轨迹的实时跟踪以及作业面积的有效核算。在Matlab仿真分析中,首先建立定位算法评价指标以便于定位效果评估,通过仿真计算得出:基于多源数据融合的优化定位算法的定位精度及稳定性均优于单一无线RSSI室内定位算法。温室大棚田间试验的实际测试结果表明,室内定位精度不大于0.125 m,定位误差小于0.4%,能够较好地满足温室内作业机具的定位及作业轨迹实时获取与监测的需求。     

国内湿地重金属污染评价的研究进展

湿地作为地球上重要的生态系统之一,具有稳定环境、物种基因保护及资源利用功能,被誉为自然之肾、生物基因库和人类摇篮。随着近年来湿地面临着面积萎缩、功能下降、污染日趋严重等危机,国内外学者对湿地保持着持续关注与研究,其中对湿地重金属的污染评价就是湿地科学研究领域的重要内容之一。笔者通过对国内十多年来有关重金属污染方面的报道进行整理分析,回顾总结了湖泊、河流、三角洲以及滨海等类型湿地的底泥、水体及土壤中重金属的污染现状与迁移特征,重点对重金属的种类、空间分布以及分析方法等进行总结归纳。在众多研究成果中,对污染物评价的方法以地累积指数法和潜在生态风险指数法使用最多。