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Contents volume     

Energy flow through an organic agroecosystem in China

The energy flow in a traditional organic agroecosystem located in Hailun county of Northeastern China was analyzed for the years 1952–1954. For this energy analysis of the Hailun agroecosystem and human society, energy production was divided into 3 systems: crops, livestock and forestry.In terms of energy, this agroecosystem was self-sustaining. Human and horse power provided the major energy inputs. In the crop system, the energy input/output ratio was about 1:2. Fossil energy input into the total agroecosystem was less than 2% of the total. Based on only fossil energy inputs and crop outputs, the ratio was 1:107. The sources of food and household energy for human society came from the crop, livestock and forestry systems. The crop system provided more than 80% of the energy for this society.In addition to natural additions of N and P, legumes, other crop rotations and the application of human and livestock wastes to the land provided the nutrients for crop production. However, the agroecosystem was not self-sustaining in terms of some soil nutrients. Quantities of both nitrogen and phosphorus were calculated to be declining because of losses due to composting, storage, burning crop residues, exporting some harvests and soil erosion.     

物质流分析视角下北京市物质代谢研究

作为"重大国家战略"的"京津冀一体化"日益引起社会各界的高度重视,推动其进程的加快,首先要解决的就是该区域的资源环境问题,而北京作为该经济圈的核心,其资源环境问题的解决更是起着关键性的作用.在提高城市环境质量、改善人们生存环境方面,北京市仍任重而道远.运用物质流分析方法(EW-MFA)可以深入探讨社会经济发展与资源消耗及环境污染之间的关系,从而为社会经济发展过程中资源环境问题的解决提供科学依据.因此,本文采用欧盟物质流核算框架(EW-MFA)建立了北京市"吞吐"状态的物质代谢模型.结果表明:1992—2014年北京市的物质输入与输出总体呈上升趋势,矿物和化石燃料是北京市物质输入的主要组成部分;受社会经济发展水平的影响,北京市的物质投入强度表现出先上升后下降的趋势;研究期间内物质代谢效率不断提高.针对北京市的资源环境问题,应转变传统发展理念,不能一味地追求物质财富的增加而忽略生态环境的影响,且不断推动技术的革新和产业结构的调整应成为实现社会经济可持续发展的有效路径.     

Simulation of boundary layer flow in Hong Kong

A three-dimensional hydrostatic numerical model using level-two turbulence closure was employed to simulate typical local wind phenomena in subtropical Hong Kong. Simulations for light wind, strong wind, sea breeze and stable flows were made and the model results compare favourably with observations.