中国CO_2地质封存与可持续发展

在全球气候变暖的自然趋势下,推行CO2地质封存项目对减缓气候变暖进程和我国实施可持续发展战略具有重要意义。本文概述了CO2在地质储层-盖层系统中的两种捕获机制:一是通过地层构造压力、地下水动力、流体密度差、盖层岩石毛细管压力及矿物(煤层)吸附等共同作用的物理捕获机制,另一种是通过水岩化学反应进行固碳的化学捕获机制。归纳了有利于长期安全封存CO2的地质条件和水文特征,结合文献资料指出我国CO2有效地质封存总容量可供中国CO2地质埋存使用1 000年以上。并从科学技术能力、人才储备、经济成本及效益预算、管理和运营体制等方面进行论证,认为我国实施CO2地质封存项目是切实可行的。结合我国不合理的能源消费结构及全球气候变暖、环境恶化可能产生的后果,阐述了CO2地质封存对我国实现节能减排、低碳经济等可持续发展战略的深远意义。建议我国尽快组织开展CO2地质封存相关科学理论、封存技术及基本框架和配套政策、法规研究,为我国应对全球气候变化提供足够的技术和人才储备。     

Organic Farming and Soil Carbon Sequestration: What Do We Really Know About the Benefits?

Organic farming is believed to improve soil fertility by enhancing soil organic matter (SOM) contents. An important co-benefit would be the sequestration of carbon from atmospheric CO₂. Such a positive effect has been suggested based on data from field experiments though many studies were not designed to address the issue of carbon sequestration. The aim of our study was to examine published data in order to identify possible flaws such as missing a proper baseline, carbon mass measurements, or lack of a clear distinction between conventional and organic farming practices, thereby attributing effects of specific practices to organic farming, which are not uniquely organic. A total of 68 data sets were analyzed from 32 peer-reviewed publications aiming to compare conventional with organic farming. The analysis revealed that after conversion, soil C content (SOC) in organic systems increased annually by 2.2% on average, whereas in conventional systems SOC did not change significantly. The majority of publications reported SOC concentrations rather than amounts thus neglecting possible changes in soil bulk density. 34 out of 68 data sets missed a true control with well-defined starting conditions. In 37 out of 50 cases, the amount of organic fertilizer in the organic system exceeded that applied in the compared conventional system, and in half of the cases crop rotations differed between systems. In the few studies where crop rotation and organic fertilization were comparable in both systems no consistent difference in SOC was found. From this data analysis, we conclude that the claim for beneficial effects of organic farming on SOC is premature and that reported advantages of organic farming for SOC are largely determined by higher and often disproportionate application of organic fertilizer compared to conventional farming.     

Analytical solution to evaluate salt precipitation during CO2 injection in saline aquifers

Carbon dioxide sequestration in deep saline aquifers is a means of reducing anthropogenic atmospheric emissions of CO₂. Among various mechanisms, CO₂ can be trapped in saline aquifers by dissolution in the formation water. Vaporization of water occurs along with the dissolution of CO₂. Vaporization can cause salt precipitation, which reduces porosity and impairs permeability of the reservoir in the vicinity of the wellbore, and can lead to reduction in injectivity. The amount of salt precipitation and the region in which it occurs may be important in CO₂ storage operations if salt precipitation significantly reduces injectivity. Here we develop an analytical model, as a simple and efficient tool to predict the amount of salt precipitation over time and space. This model is particularly useful at high injection velocities, when viscous forces dominate.First, we develop a model which treats the vaporization of water and dissolution of CO₂ in radial geometry. Next, the model is used to predict salt precipitation. The combined model is then extended to evaluate the effect of salt precipitation on permeability in terms of a time-dependent skin factor. Finally, the analytical model is corroborated by application to a specific problem with an available numerical solution, where a close agreement between the solutions is observed. We use the results to examine the effect of assumptions and approximations made in the development of the analytical solution. For cases studied, salt saturation was a few percent. The loss in injectivity depends on the degree of reduction of formation permeability with increased salt saturation. For permeability-reduction models considered in this work, the loss in injectivity was not severe. However, one limitation of the model is that it neglects capillary and gravity forces, and these forces might increase salt precipitation at the bottom of formation particularly when injection rate is low.     

城市屋面雨水绿地水平流渗透净化研究

把城区屋面汇集的雨水径流通过绿地或人工土层净化后收集利用或渗透地下,既可涵养地下水,又截留处置了部分雨水,减轻了雨洪负荷和雨水径流对受纳水体的污染,是一种经济有效的雨水利用方案。但为保证雨水渗入地下后不污染土层和地下水源,本文研究了屋面雨水在天然和人工配制的两种土壤中水平流动的净化作用及其规律。为屋面雨水绿地渗透方案的工程实施提供技术依据。     

质谱直接测量法解析盐城市大气细颗粒物来源

为全面了解盐城市大气颗粒物的组成,摸清以PM2.5为首要污染物的来源,说清其化学组分和源贡献率,于2014年12月16日00:00—2014年12月21日09:00,利用在线单颗粒气溶胶质谱仪,对盐城市细颗粒物进行实时在线源解析。结果表明,盐城首要污染物为燃煤,占比为23.7%,其次是机动车尾气,占比为18.3%,第三位是扬尘,占总颗粒数的15.7%,生物质燃烧占比为14.8%位列第四,工业工艺源、二次无机源和其他源贡献率相对较小。     

水中消毒副产物的监测方法研究进展

含氯、含氧等杀菌类消毒剂在饮用水生产、废水排放、再生水利用等环节应用广泛,会与水中的前驱物通过取代、氧化还原、水解、加成等反应形成种类繁多的消毒副产物(DBPs).DBPs的靶标监测基于已知DBPs的特性如挥发性、半挥发性、不挥发性等,采取相应的前处理和仪器分析方法;非靶标鉴别可对大量未知的DBPs进行筛查.综述了三卤...     

偶氮二甲酰胺发泡剂清洁生产评价模型

提出了针对不同工艺的偶氮二甲酰胺（ADC）发泡剂生产企业的清洁生产综合评价方案。利用逐层序关系分析法确定各指标的影响因子,采用极差标准化法对正逆向指标数据进行初步处理,使用主成分分析法对ADC发泡剂生产企业进行排名。该研究为ADC发泡剂清洁生产评价提供了一个更加客观和精确的方案。     

浆固碎石桩成桩注浆渗透影响分析

浆固碎石桩作为一种新型软土地基处理技术,其主要通过注浆改善桩体的加固效果,同时通过浆体渗透来改善桩周土体的物理力学性质,从而减小浆固碎石桩复合地基沉降。针对浆体对桩周土体的渗透作用,按照平面轴对称问题,推导出注浆渗透影响范围的计算方法和浆固区压缩模量计算公式,并通过室内模型试验研究,验证了浆固区压缩模量计算公式的正确性。随后,利用数值计算分析,对浆固区影响范围进行量化分析,并通过数值拟合得到了考虑注浆渗透影响的桩体等效半径计算公式。所得结果对工程设计具有重要的指导意义。     

污水厂出水回用于污泥焚烧烟气的净化

开展了污水处理厂出水回用于污泥焚烧烟气净化的实验研究。生化出水净化吸收污泥焚烧烟气的效果与气水比、进气浓度、进水pH、进水碱度和水温等因素有关。研究结果表明,气水比10∶1,进水pH为7条件下,生化出水能够有效吸收污泥焚烧烟气中的各种污染物质,出气中气体污染物低于《生活垃圾焚烧污染控制标准》（GB18485-2001）的排放限值要求,吸收后出水各指标均低于《污水综合排放标准》（GB8978-1996）中污染物排放限值的要求。该工艺脱硫效率可达90%,具有系统简单可靠、以废治废、不产生二次污染等优点。