我国区域空气污染治理效率及其影响机制——基于超效率SBM模型和门槛回归模型

随着人民对美好生活需求的日益增长,政府空气污染治理的效率问题日益得到重视。本文从地方政府空气污染治理效率及其影响因素的视角入手,以全国30个省份为研究对象,运用超效率SBM模型测算2003—2015年各省级区域的空气污染治理效率。在此基础上,运用门槛回归模型分析政府空气污染治理效率的影响机制。研究表明:①地区间空气污染治理效率差异性较为显著。中部、西部空气污染治理效率整体呈下降趋势。东部和东北地区空气污染治理效率则上升比较平稳。②政策规划、碳源、污染物排放和环境治理投入表现出双重门槛特征,其中碳源对空气污染治理效率影响显著,而以碳为首的能源消费结构则主要对中部和西部空气污染治理效率产生影响。落后地区政府应注重产业升级,财政上应对碳税等税目进行征收,产业上应鼓励企业创新,并对落后企业进行倒逼升级。     

不同喷雾方式下低阻文丘里振弦栅除尘配置优化实验研究

为了对比径向外喷和轴向喷雾下的低阻文丘里振弦栅耦合除尘效果，以除尘效率和系统阻力为参照，选定喉管气速、振弦栅数、纤维丝间隙和喉管液气比进行单因素实验。结果表明2种喷雾方式的除尘效率和系统阻力的变化趋势相同。利用SPSS软件进行4因素3水平正交实验设计，在特定参数条件下，2种喷雾方式的因素影响排序相同，除尘效率为纤维栅数＞纤维丝间隙＞喉管气速＞喷雾量；系统阻力为喉管气速＞纤维栅数＞纤维丝间隙＞喷雾量；径向外喷最佳配置为喉管气速24 m/s、喷雾量2.3 L/min、2块间隙为0.8 mm纤维栅板；轴向喷雾为喉管气速28 m/s、喷雾量2.4 L/min、2块间隙为0.8 mm纤维栅板；在最优配置下的除尘性能为径向外喷＞轴向喷雾。     

液氮泡沫发生器内流动特性研究

低温液氮与泡沫混合液直接接触产生氮气泡沫是一种新型的掺混形式,利用液氮高汽化比的特点,搭建液氮泡沫可视化实验装置,进行氮气-水两相流及液氮泡沫流动特性的研究。结果表明,液氮相变产生大量氮气,其与泡沫液混合产生泡沫,温度有所回升,最终趋于泡沫混合液温度;管路沿程压降较小;液氮射流破碎及流动过程可分为6个区域:低温液氮区、向上循环翻滚区、滞留区、泡沫与泡沫混合液混合区、致密泡沫区、泡沫混合液区。流体向下游流动过程中持续发泡;为防止管路结冰,需合理控制泡沫混合液与液氮流量。     

Nitrogen budget and its environmental loading in an urban ecosystem with the rapid urbanisation of China

A detailed nitrogen (N) budget has been developed for an urban ecosystem based on the method of material flow analysis. How increased human activity and urbanisation influences N cycling have also been analysed. Total N input and output in the urban ecosystem of Zhengzhou City (ZUE) was calculated at 304.8?Gg was 275.3?Gg year^?1, resulting in an N accumulation of 29.5?Gg year^?1. Industry and human life activities, which respectively accounted for 43.8% and 34.2% of total N inputs and 52.6% and 29.1% of total N outputs, were the core of N flow in the urban ecosystem. Humans activities mediated more than 98% N inputs into the ZUE, 73.2% of N was released into the atmosphere and 11.7% into hydrosphere. This very large volume of released N could contribute to regional problems. High energy consumption, insufficient wastewater treatment facility practices, and low N use efficiency are the primary causes of pollution. The major challenge ahead for the urban ecosystem is how to manage high-intensity N pollutant inputs to the urban ecosystems coupled with incomplete N cycling and removal. Based on the analysis of the N budget and loading, this study also proposes an N management strategy for the ZUE.     

Carbon trading thickness and market efficiency in a socialist market economy

Unlike the European Union emission trade system (EU ETS), China’s pilot ETSs implemented diversified policy designs instead of using a uniform framework. Variance ratio test is used to evaluate the Efficient Market Hypothesis (EMH) in China’s carbon trading markets. The results of two versions of variance ratio tests indicate that the carbon trading market in Hubei is considered weak form efficient, and the socialist market economy does not necessarily lead to market inefficiency in carbon trading markets. Thin trading activities generate market frictions and bias the Efficient Market Hypothesis (EMH) tests.     

Exogenously applied oxalic acid assists in the phytoremediation of Mn by Polygonum pubescens Blume cultivated in three Mn-contaminated soils

• The OA supply significantly increased the water-extractable Mn in all soils. • All OA supply levels promoted plant growth in unexplored soil. • Low OA supply level promoted plant growth in explored and tailing soils. • OA amendment increased the Mn concentrations and total Mn in P. pubescens. • P. pubescens experienced less Mn stress in unexplored soil than in the other two soils. The current study evaluated the effects of oxalic acid (OA) application on the growth and Mn phytoremediation efficiency of Polygonum pubescens Blume cultivated in three different manganese (Mn)-contaminated soils sampled from an unexplored area (US), an explored area (ES) and a tailing area (TS) of the Ertang Mn mine, South China. The supplied levels of OA were 0 (control), 1 (low level), 3 (medium level), and 9 (high level) mmol/kg, referred to as CK, OA1, OA3 and OA9, respectively. The results revealed that the average water-extractable Mn concentrations US, ES and TS amended with OA increased by 214.13, 363.77 and 266.85%, respectively. All OA supply levels increased plant growth and Mn concentrations in US. The low OA supply level increased plant growth in ES and TS; however, contrasting results were found for the medium and high OA supply levels. Plant Mn concentrations and total Mn increased in ES and TS in response to all OA supply levels. Total Mn in the aerial parts increased by 81.18, 44.17 and 83.17% in US, ES and TS, respectively; the corresponding percentages for the whole plants were 81.53, 108.98 and 77.91%, respectively. The rate of ·O₂⁻ production and malondialdehyde (MDA) concentrations increased in response to OA amendment, especially the medium and high OA supply levels in ES and TS. In general, antioxidant enzymes might play a vital role in alleviating Mn stress in plants cultivated in US, while non-enzymatic antioxidants might be the main factor for plants cultivated in ES and TS.     

北京城区降水对PM2.5和PM10清除作用分析

基于北京市PM_2.5和PM₁₀质量浓度、组分浓度以及降水数据，利用数理统计、相关性分析等方法分别从降水总量、降水时长和降水前颗粒物浓度3个角度研究降水对PM_2.5、PM₁₀的清除作用，同时以一次典型降水过程为例，具体分析降水对颗粒物的影响。结果表明：降水总量的增加有助于促进PM_2.5、PM₁₀的清除，随着降水总量增加，PM_2.5、PM₁₀的平均清除率提高，有效清除的比例增加；连续降水可增强对大气颗粒物的湿清除作用，连续降水达3d可有效降低PM_2.5、PM₁₀浓度；降水对PM_2.5、PM₁₀浓度的清除率和大气颗粒物前一日的平均浓度有较好的正相关性。降水对大气颗粒物的清除可分为清除、回升和平稳3个阶段，各个阶段大气颗粒物的变化趋势不同。降水对于大气气溶胶化学组分和酸碱性的改变具有明显作用，对于大气颗粒物各种组分的清除效果不完全相同。对于大气中OC、NO₃^-、SO₄^2-和NH₄⁺去除率较高，且这4种组分主要以颗粒态形式被冲刷进入降水中，加剧了北京市降水酸化程度。     

Wetland Flowpaths Mediate Nitrogen and Phosphorus Concentrations across the Upper Mississippi River Basin

Eutrophication, harmful algal blooms, and human health impacts are critical environmental challenges resulting from excess nitrogen and phosphorus in surface waters. Yet we have limited information regarding how wetland characteristics mediate water quality across watershed scales. We developed a large, novel set of spatial variables characterizing hydrological flowpaths from wetlands to streams, that is, “wetland hydrological transport variables,” to explore how wetlands statistically explain the variability in total nitrogen (TN) and total phosphorus (TP) concentrations across the Upper Mississippi River Basin (UMRB) in the United States. We found that wetland flowpath variables improved landscape-to-aquatic nutrient multilinear regression models (from R² = 0.89 to 0.91 for TN; R² = 0.53 to 0.84 for TP) and provided insights into potential processes governing how wetlands influence watershed-scale TN and TP concentrations. Specifically, flowpath variables describing flow-attenuating environments, for example, subsurface transport compared to overland flowpaths, were related to lower TN and TP concentrations. Frequent hydrological connections from wetlands to streams were also linked to low TP concentrations, which likely suggests a nutrient source limitation in some areas of the UMRB. Consideration of wetland flowpaths could inform management and conservation activities designed to reduce nutrient export to downstream waters.     

旋流气浮除油装置预处理含油污水

在河南油田开展旋流气浮除油装置的现场试验,考察进水流量和曝气量对旋流气浮除油装置除油效果的影响。试验结果表明:在进水流量为1.8 m³/h、曝气量为0.5 L/min时,除油率最高达到96.03%;在不添加任何药剂的条件下,装置处理效果稳定;连续运行6 d内,进水含油量为174.57~1 193.15 mg/L时,出水含油量可以保持在137.38 mg/L以下,除油率为58.58%~94.53%。     

Experimental and theoretical investigation of dry-water containing phosphoric acid for new fire suppressant

To overcome the shortcomings of phosphorus-containing compounds (PCCs, not widely used) in fire suppression, the dry water powder containing phosphoric acid was analyzed for a new fire suppressant (SiO₂-P). First, the fine conditions (solid-to-liquid ratio, stirring time and stirring speed) were determined to prepare the new powder. The particle size distributions and XPS of SiO₂-P powder were analyzed. The TG tests were conducted to study the decomposition of powder, and there was a major decomposition peak. Second, the extinguishing time of SiO₂-P powder was tested, which showed that the SiO₂-P powder containing phosphorus species could significantly improve the fire suppression ability. In addition, the kinetic parameters of powder decomposition reaction were determined by genetic algorithm based on TG results. Last, based on the decomposition products and kinetic parameters, the burning velocity and mass fraction of free radicals of CH₄/air flame with SiO₂-P powder addition were studied theoretically. The results indicated that SiO₂-P powder had great ability of reducing the burning velocity and scavenging free radicals. Furthermore, the suppression effects were analyzed, which indicated that the cooperation of H₂O and P suppression effect dominated the suppression mechanism and resulted in the good suppression efficiency.