2,4-D Mineralization in soil profiles of a cultivated hummocky landscape in Manitoba,Canada

The objective of this study was to quantify 2,4-D (2,4-dichlorophenoxyacetic acid) mineralization in soil profiles characteristic of hummocky, calcareous-soil landscapes in western Canada. Twenty-five soil cores (8 cm inner diameter, 50 to 125 cm length) were collected along a 360 m transect running west to east in an agricultural field and then segmented by soil-landscape position (upper slopes, mid slopes, lower slopes and depressions) and soil horizon (A, B, and C horizons). In the A horizon, 2,4-D mineralization commenced instantaneously and the mineralization rate followed first-order kinetics. In both the B and C horizons, 2,4-D mineralization only commenced after a lag period of typically 5 to 7 days and the mineralization rate was biphasic. In the A horizon, 2,4-D mineralization parameters including the first-order mineralization rate constant (k ₁), the growth-linked mineralization rate constant (k ₂) and total 2,4-D mineralization at the end of the experiment at 56 days, were most strongly correlated to parameters describing 2,4-D sorption by soil, but were also adequately correlated to soil organic carbon content, soil pH, and carbonate content. In both B and C horizons, there was no significant correlation between 2,4-D mineralization and 2,4-D sorption parameters, and the correlation between soil properties and 2,4-D mineralization parameters was very poor. The k ₁ significantly decreased in sequence of A horizon (0.113% day^?1) > B horizon (0.024% day^?1) = C horizon (0.026% day^?1) and in each soil horizon was greater than k ₂. Total 2,4-D mineralization at 56 days also significantly decreased in sequence of A horizon (42%) > B horizon (31%) = C horizon (27%). In the A horizon, slope position had little influence on k ₁ or k ₂, except that k ₁ was significantly greater in upper slopes (0.170% day^?1) than in lower slopes (0.080% day^?1). Neither k ₁ nor k ₂ was significantly influenced by slope position in the B or C horizons. Total 2,4-D mineralization at 56 days was not influenced by slope positions in any horizon. Our results suggest that, when predicting 2,4-D transport at the field scale, pesticide fate models should consider the strong differences in 2,4-D mineralization between surface and subsurface horizons. This suggests that 2,4-D mineralization is best predicted using a model that has the ability to describe a range of non-linear mineralization curves. We also conclude that the horizontal variations in 2,4-D mineralization at the field scale will be difficult to consider in predictions of 2,4-D transport at the field scale because, within each horizon, 2,4-D mineralization was highly variable across the twenty-five soil cores, and this variability was poorly correlated to soil properties or soil-landscape position.     

活性污泥中细微沙浓度的预测模型

悬浮在污泥混合液中的细微沙会导致活性污泥混合液挥发性悬浮固体与混合液悬浮固体比值（ratio of mixed liquor volatile suspended solids to mixed liquor suspended solids,MLVSS/MLSS）降低。通过向生化池进水中连续投加体积平均粒径分别为14、33、50、66和107 μm的石英砂,研究不同粒径细微沙对活性污泥MLVSS/MLSS的影响,探讨不同粒径细微沙的悬浮特性,构建活性污泥中细微沙浓度的预测模型,以为污水厂运行调控提供理论基础。研究结果表明,细微沙粒径越小,悬浮比（悬浮在污泥混合液中的细微沙占生化池进水中细微沙总量的比例）越大,悬浮比与细微沙粒径呈显著的相关关系。通过预测模型得到的细微沙浓度的预测值与实测值差异较小,说明构建的活性污泥中细微沙浓度的预测模型是合理的。污水厂可在维持活性污泥MLVSS稳定的条件下,结合活性污泥中细微沙的浓度,调控污泥MLSS,保证污水处理系统的稳定运行。     

降雨条件下冰碛土滑坡模型试验研究

实践指出降雨是引发边坡破坏的重要外部因素之一。为研究降雨作用下冰碛土滑坡规律和导致滑坡的内在因素,本次研究制作了 3 种坡度的冰碛土边坡模型,进行了 3 种降雨强度下的共 9 组降雨作用下的冰碛土滑坡试验, 通过试验观测边坡土含水率、土压力变化及边坡变形数据,从而揭示降雨条件下冰碛土边坡破坏的机制。通过对冰碛土边坡降雨试验过程的观测发现,边坡模型坡脚位置的含水率最先稳定,各观测点的土压力没有观测到明显变化规律。实验过程中降雨入渗导致的滑坡变形大致可以划分为 4 个阶段,首先为局部性土颗粒滑落,其次为边坡表面形成冲蚀沟,然后小范围的冲沟逐渐扩展为中部和上部连片滑动,最后冰碛土边坡浅层形成贯通性滑动体,滑动的泥水混合物流动一段距离后在坡脚处形成堆积体。3 种暴雨工况下各坡度边坡主要特征表现为边坡表层土体产生小范围坡面径流,径流逐渐增强形成冲蚀沟,其后发生滑坡破坏。3 种大雨工况下坡度超过 45°的边坡发生了滑坡破坏。3 种中雨工况下仅 60°边坡产生了滑坡破坏。结果表明降雨强度和边坡坡度是影响冰碛土滑坡发生的主要因素。     

A multiple criteria evaluation of sustainable agricultural development models using AHP

Selection of the appropriate agricultural development model has become an important issue in Iran. Using data from Fars province of Iran, the purpose of this paper is to use analytic hierarchy process (AHP) for selecting between the two competing sustainable agricultural development models, which have been developed based on the general tenets of Ecological Modernization (EM) and De-Modernization (DM) theories. Farmers, environmentalists, board members of rural cooperative, rural women and experts from Fars Agricultural (Jehad-e-Keshavarzi) Organization participated in application of AHP to this study. They applied AHP to determine the priority of DM and EM based sustainable agricultural development models. Each group determined the priority of the two models for sustainable agricultural development. The findings indicated that ecological criteria i.e. wise use of resources, environmental protection and product quality are the most important criteria for sustainable agriculture of Iran, followed by economic criterion employment and social criterion participation. A sensitivity analysis was carried out to determine the critical factors that affected the priority of alternatives. The results indicated that EM-based sustainable agricultural development model has a higher priority as the theoretical base of agricultural development of Iran. Readers should send their comments on this paper to BhaskarNath@aol.com within 3 months of publication of this issue     

水泥土桩复合地基场地地震效应分析

将复合地基加固区视为均质体,采用课题组提出的基于Davidenkov骨架曲线的土体动弹塑性模型描述复合地基加固区和非加固区土体的动应力-应变关系,基于大型有限元软件ABAQUS的操作平台,开发了土体动粘弹塑性模型的子程序。选择南京某典型软弱场地为研究对象,采用ABAQUS软件进行了复合地基二维弹塑性地震反应分析,研究了输入地震动强度和频谱特性、水泥土桩加固宽度和深度、复合地基模量对复合地基场地地震效应的影响。结果表明:输入地震动强度和频谱特性对复合地基地震效应影响较大;复合地基加固区地表的峰值加速度反应较自由场的反应明显减小,而加固体区外侧地表的峰值加速度反应较之自由场的反应可能增大;复合地基地表的峰值加速度反应随着水泥土桩加固深度和复合模量的增加而减小,而与加固宽度无关。     

卡鲁塞尔氧化沟水力学特性的大涡模拟

本文基于大涡模拟中的Smagorinsky-Lilly模型,对Carrousel氧化沟模型进行了水力学特性模拟,并研究了沟内流速和涡量分布规律.速度与压力耦合求解使用了压力隐式算子分裂PISO (Pressure-Implicit with Splitting of Operators)算法,采用VOF(Volume of fluid)方法追踪自由液面.模拟结果表明,回流现象主要出现在上中层混合液中,逆流现象主要出现于上层混合液中;转轮与转刷的推流作用是造成水面变化剧烈的原因;距转轮与转刷较近的区域、转速较快的转轮与转刷区域及直道段转刷下游水面较高一侧中上层区域的涡量较大.根据实验验证,本次模拟结果和实验值吻合度较好,Smagorinsky-Lilly模型可以准确模拟氧化沟水力学特性.     

森林合理年伐量分析确定方法研究

森林合理年伐分析确定是年森林采伐限额编制的关键技术之一,也是森林经理学的重要内容之一。本文从森林永续利用理论出发,以消长比度、成熟林采伐度、龄级结构改善度、流量均衡度、需要满足度５个指标建立了分析确定的综合评价模型,提出了森林合理年伐量分析确定的精确化方法,从而有效地保证了结果的科学性和准确性。     

硬化路面与温度场响应模型研究

硬化路面是城市热环境效应影响因素中较为重要的一个因素.笔者在研究了深圳市城市热效应的基础上,建立了一个三维动态模型对硬化路面条件下的温度场进行模拟.通过将模型的计算结果和在深圳的实测结果进行对比,发现2条曲线吻合较好,模拟结果十分接近实测结果.模型模拟结果还证明了硬化路面由于铺筑的材料具有较大蓄热、导热的能力,而且透水性差,因此温度升降都很快,对城市的热效应贡献大;城市绿化隔离带对城市温度场具有很好的调节作用,因此合理配置城市中的绿地对城市区域微热环境的改善能够起到很好的作用.      

综合福利视角下中国生态文明建设绩效评价及国际比较

基于强可持续研究范式,以生态经济学和可持续发展理论为基础,运用两阶段网络Super-EBM模型进行绩效测算和评价,打开生态福利转化过程的“黑箱”,基于综合福利视角将生态文明建设绩效进一步分解为生态经济效率和经济福利效率,实证研究部分选取2006-2015年的时间序列数据对中国“十一五”和“十二五”期间的生态文明建设绩效水平进行纵向分析,与此同时,选取42个国家2014年的截面数据进行横向的国际对比研究。研究表明：（1）“十一五”到“十二五”期间,中国生态文明建设绩效（0.986）整体水平一般,均未实现DEA有效,但“十二五”期间已呈现出逐年改善的利好趋势。国际比较层面,瑞士（1.647）、印度尼西亚（1.365）、爱尔兰（1.039）依次排名前三位,中国（0.297）排名相对靠后,位列倒数第二。各国之间差异较大,总体上呈现出“OECD国家（0.677）最高、G20国家（0.611）次之、金砖国家（0.417）最低”的态势。（2）从分阶段效率来看,无论是纵向分析还是横向对比,均发现第一阶段的生态经济效率明显低于第二阶段的经济福利效率,生态经济效率偏低是导致生态文明建设绩效总体水平偏低的主要原因。（3）与传统的单阶段、径向或非径向DEA模型相比,两阶段网络Super-EBM模型综合考虑了径向和松弛变量问题,测算出来的效率值更为精确,能够更为客观地反映现实。同时,对于其他领域涉及两阶段或多阶段生产系统的效率或绩效评估具有较好的借鉴价值。最后,根据上述结论提出相应的政策建议。