Water chemistry in 179 randomly selected Swedish headwater streams related to forest production,clear-felling and climate

From a policy perspective, it is important to understand forestry effects on surface waters from a landscape perspective. The EU Water Framework Directive demands remedial actions if not achieving good ecological status. In Sweden, 44 % of the surface water bodies have moderate ecological status or worse. Many of these drain catchments with a mosaic of managed forests. It is important for the forestry sector and water authorities to be able to identify where, in the forested landscape, special precautions are necessary. The aim of this study was to quantify the relations between forestry parameters and headwater stream concentrations of nutrients, organic matter and acid-base chemistry. The results are put into the context of regional climate, sulphur and nitrogen deposition, as well as marine influences. Water chemistry was measured in 179 randomly selected headwater streams from two regions in southwest and central Sweden, corresponding to 10 % of the Swedish land area. Forest status was determined from satellite images and Swedish National Forest Inventory data using the probabilistic classifier method, which was used to model stream water chemistry with Bayesian model averaging. The results indicate that concentrations of e.g. nitrogen, phosphorus and organic matter are related to factors associated with forest production but that it is not forestry per se that causes the excess losses. Instead, factors simultaneously affecting forest production and stream water chemistry, such as climate, extensive soil pools and nitrogen deposition, are the most likely candidates The relationships with clear-felled and wetland areas are likely to be direct effects.     

不同天气型下武汉城市圈PM2.5污染及大气层结特征分析

利用2015—2019年PM_2.5和气象要素观测资料、NCEP和ERA5再分析资料,分析不同天气型下武汉城市圈PM_2.5区域污染时空分布、天气尺度环流和大气层结特征.结果表明,城市圈污染以武汉为中心,多为轻度-中度污染,西部重于东部.造成武汉城市圈区域污染增长的天气形势包括4类,分别为冷高压底前部型、高压后部型、均压场型和低压倒槽型.4类污染天气型均有较低的混合层高度和地表通风系数,且边界层存在弱下沉运动和逆温,抑制污染垂直扩散.但气象要素影响PM_2.5污染的机理各异：冷高压底前部型主要为大气压梯度引导偏北大风带来污染物远程输送,边界层冷平流导致低温、锋面逆温和浅薄高湿层(65%～80%),强输入性污染配合吸湿性累积增长造成严重污染,逆温厚度对PM_2.5增幅作用明显;低压倒槽型东南风输入污染弱,但高温、低压引起气流辐合导致本地污染汇积,边界层暖平流带来平流逆温和深厚湿层(1000～750 hPa),逆温层底高偏低、厚度偏厚,促进污染物在近地面吸湿增长;高压后部和均压场型均为浅薄湿层(1000～975...     

中国人口集疏格局与形成机制研究

人口集聚和疏散是人口空间分布格局最直观和最集中的体现,基于人口集聚度的中国人口集疏的空间格局和形成机制的研究,有助于准确把握中国人口空间分布的基本脉络,具有重要的学术价值和实践意义。研究采用了人口集聚度分级评价的方法,依据人口集聚度的不同,将各个地区划分为不同等级的人口集聚区,并对其分别讨论。在此基础上,结合中国人口分布格局、自然条件的空间分布格局、人居环境自然适宜性评价结果以及经济发展格局和城市化格局,对中国的人口集疏的空间格局进行了归纳,并进一步对相应的形成机制进行了探讨,得出了我国人口分布的空间不平衡日益加剧,并呈现沿海、沿江、沿线集聚的态势的基本结论,并对我国人口分布集疏格局的形成进行了探讨,提出了自然因素奠定我国人口分布的基本格局,而经济发展不平衡与城市化成为人口集聚的动力的观点。     

提高建设项目环境影响评价质量的对策建议

针对目前我国环评机构鱼龙混杂,环评从业人员素质良莠不齐,建设项目环评质量亟待提高等问题,本文就环评过程中存在的问题和不足进行剖析,并就如何提高建设项目环评质量提出对策建议。     

基于物元模型的煤自燃危险性分析

为探索判断煤自燃的危险性新方法,在煤低温氧化试验的基础上,基于可拓理论构建了煤自燃危险性熵权和经验权的物元综合分析模型。采用该方法对4个不同煤样低温氧化试验数据进行自燃危险性分析,得出各煤样自燃危险性的等级及差异程度,并提出相应的防范对策。结果表明:4号煤样比其他煤样更具自燃危险性,需要重点防范。该方法的预测结果与实际情况相吻合。     

企业安全法规符合性评估方法

在安全法制建设逐步完善,安全法规数量逐年增多的背景下,为能有效落实企业安全生产主体责任,系统提出一种企业安全法规符合性评估方法:通过安全法规适用性辨识明确企业应满足的法规清单,对法规要求归纳汇总形成安全法规符合性定量评估指标体系,并以体系为依据对企业落实安全法规的程度进行科学评估、做好符合性保持.以某专业测井公司为例,构建了符合其生产经营特点的安全法规符合性评估体系,开发了基于B/S构架的辅助评估软件,并已应用于企业日常安全管理.结果表明:通过对安全法规要求分类归纳汇总形成的符合性评估指标体系,可有效评估企业安全法规落实程度,提高企业安全法规符合性评估效率.     

NOx reburning in oxy-fuel combustion: A comparison between solid and gaseous fuels

In the development of oxy-fuel combustion, reburning of nitrogen oxides, recycled with the flue gases, has been investigated for primary NO_x control. Reduction of between 50 and 80% of the recycled nitrogen oxides has been measured. The present work evaluates the performance of gaseous and solid fuels as agents for reduction of nitrogen oxides by comparing experimental and modelling work performed at Chalmers University of Technology with different fuels. It is shown that the reduction is similar during propane and lignite firing, but that the lignite has slightly higher reduction efficiency. Differences in combustion temperature and heterogeneous effects are possible explanations.     

A New Approach of BioCO2 Fixation by Thermoplastic Processing of Microalgae

Effective sequestration of carbon dioxide (CO₂) by algae reduces greenhouse gases effect on global warming. Algae biomass or residual such as biomeal from algae biofuel processing can be judiciously used for industrial applications such as fertilizer, animal feed, and plastics. Conversion of algae into useful plastic materials can be accomplished by extrusion technology. During algal plastic manufacturing, up to 20% thermoplastic algal blends can be fixated into or encapsulated by a non-biodegradable polymer such as polyolefin, which is known to be resistant to abiotic or biotic degradation. As a result, CO₂ that is captured by algae through photosynthesis is permanently stored in a form of biomass and will not be released back into the atmosphere. The extrusion of microalgae reported in this article is a novel process to sequester CO₂ and at the same time it makes a good use of the algae biomass in plastic manufacturing. Mechanical properties of the thin plastic films containing microalgae are comparable to the neat polyurethane or polyethylene films. Injection molded articles containing microalgae are dimensionally stable. However, a lower tensile strength, especially elongation at break, is observed in comparison to the neat polypropylene.     

陕西关中地区城市灾害评价

本文在详细分析关中地区六个大中城市的主要自然灾害和城市地质灾害的基础上，分别评价了各种灾害造成的经济损失，各个城市的灾害危险性、易损性和抗灾能力，并结合防灾对策对城市进行了综合分类。