面向高质量发展的海岸带资源型城市空间治理——基于跨系统影响的视角

海岸带资源型城市是陆海资源高度交错的空间载体,以跨系统影响的视角对其进行空间治理,有助于突破资源型城市转型发展的局限性,实现资源综合效益最大化。首先,本文厘清了跨系统影响的复杂性与海岸带资源的多样性,并以空间资源作为研究的核心要素。其次,强调陆海全系统生态—经济—社会的“综合效益”,以“陆海统筹”作为指引,深化海岸带资源型城市高质量发展的内涵。再次,探索了“关键资源识别—空间效益评价—空间资源调控”的高质量发展空间治理路径。即通过识别跨系统影响范围、开展资源空间调查、明确资源组合模式来甄别关键资源,进而构建包含“综合效益评估”和“跨系统影响修正”的资源空间效益评价框架,明晰各资源空间效益的差异,为空间治理提供决策依据。最后,根据空间效益评价结果,结合国土空间规划要求,在资源空间优化、区域资源统筹、空间总量分配、开发模式引导等方面提出海岸带资源型城市高质量发展的有效调控方式。     

山地平原过渡带耕地土壤重金属空间特征及潜在生态风险因素探析

为探讨典型山地平原过渡带地区耕地土壤重金属空间分布特征及其潜在生态风险因素.本文以拥有成都平原-龙门山脉过渡带这一典型过渡地形的四川省某县域为研究区,采用地统计法和潜在生态风险指数法分析研究区耕地土壤Cd、Cr、Cu、Pb和Zn的空间分布情况并进行潜在生态风险评价,结合地理探测器进一步发掘导致其潜在生态风险空间差异的主...     

西北干旱区作物灌溉技术效率及影响因素

水资源短缺是制约西北干旱区可持续发展的硬约束,提高作物灌溉技术效率、压缩农业灌溉用水是缓解水资源供需矛盾的可能途径之一。基于2014年张掖市农户调研数据,采用DEA-Tobit模型,分析了黑河流域中段不同类型灌区作物灌溉技术效率及其影响因素。结果表明：（1）典型灌区主要作物灌溉技术效率均存在改进空间,节水潜力较大。在其他投入保持不变的情况下,如果典型灌区主要作物灌溉技术效率达到目前的最高水平,平原灌区生产同样产量的制种玉米和大田玉米,灌溉用水可分别减少34.47%和38.15%;北部荒漠灌区生产同样产量的棉花、制种西瓜和玉米套小麦,灌溉用水可分别减少48.42%、34.82%和22.99%;沿山灌区生产同样产量的小麦、马铃薯、大麦和大田玉米,灌溉用水可分别减少14.48%、30.75%、25.50%和35.96%。（2）不同灌区之间作物灌溉技术效率的变异系数与作物种植面积占比呈负向关系,同一灌区内部种植相同作物的农户生产管理水平存在明显差异。（3）农地细碎化程度和农户耕地面积扩大会降低作物灌溉技术效率,改善耕地质量能提高北部荒漠灌区作物灌溉技术效率,增加井水灌溉会提高平原灌区大田玉米和沿山灌区作物灌溉技术效率,灌溉次数与多数作物灌溉技术效率呈“倒U型”关系,而农户耕作需求及其对风险态度的影响需结合具体情况进行判断。合理确定种植规模、加快农地空间优化,因地制宜地改善耕地质量,完善水利设施、合理使用井灌、增强河水灌溉放水的灵活性,是提升黑河流域作物灌溉技术效率的主要途径。     

Application of powdered activated carbon coating to fabrics in a hybrid filter to enhance mercury removal

Elemental mercury(Hg0) is predominant constituent of flue gas emitted from coal-fired power plants. Adsorption has been considered the best available technology for removal of Hg0 from flue gas. However, adsorbent injection increases the amount of ash generated. In the present study, powdered activated carbon(PAC) was coated on polytetrafluoroethylene/glass fiber filters to increase Hg0 removal while concurrently reducing the amount of ash generated. The optimal PAC coating rate was determined in laboratory experiments to ensure better Hg0 removal with low pressure drop. When PAC of particle size less than 45 μm was used, and the areal density was 50 g/m2, the pressure drop remained under 30 Pa while the Hg0 removal efficiency increased to 15.8% from4.3%. The Hg0 removal efficiency also increased with decrease in filtration velocity. The optimal PAC coating rate was applied on a hybrid filter(HF), which was combined with a bag filter and an electrostatic precipitator in a single chamber. Originally designed to remove fine particulates matter, it was retrofitted to the flue gas control device for simultaneous Hg0 removal. By employing the PAC coating, the Hg removal efficiency of the HF increased to 79.79% from 66.35%. Also, a temporary reduction in Hg removal was seen but this was resolved following a cleaning cycle in which the dust layer was removed.     

南海岛礁海洋环境中典型不锈钢浪花飞溅区腐蚀规律

目的 研究南海岛礁环境浪花飞溅区中典型不锈钢的腐蚀规律.方法 在南海岛礁进行现场腐蚀试验,利用表面微观形貌观测、腐蚀产物分析及失重测试等手段,对比分析了304、316L和2205不锈钢在浪花飞溅区中的腐蚀形貌、腐蚀速率和腐蚀深度.结果 在浪花飞溅区,304不锈钢的腐蚀速率最大,316L不锈钢次之,2205不锈钢最小;在浪花飞溅区304不锈钢和316L不锈钢局部腐蚀主要以点蚀和缝隙腐蚀为主,2205不锈钢耐腐蚀性良好,局部腐蚀不明显;三种不锈钢的腐蚀产物主要包括 α-FeOOH、γ-FeOOH、γ-Fe2O3.结论 三种不锈钢的腐蚀产物基本相同,但2205不锈钢腐蚀速率变化趋势与另外两种不锈钢明显不同.     

某焦化场地非均质包气带中多环芳烃(PAHs)来源及垂向分布特征

利用某废弃焦化场地内6眼深层采样孔,样品最大采集深度9. 5～42 m不等,分析包气带剖面上16种PAHs分布特征、污染来源以及影响迁移的因素.结果表明,各钻孔ΣPAHs最大含量介于134. 79～11 266. 81 mg·kg~(-1)之间,主要分布层位为地表以下1～5 m,含量以低环(2+3环)为主,单体以萘含量最高.场地污染主要来自于煤的燃烧源.焦油、沥青及其深加工产物的污染对场地ΣPAHs含量起控制作用.包气带砂卵砾石层作为污染物良好的下渗通道,砂层透镜体通过吸附及截留作用成为PAHs的主要富集层.化产区排放或泄漏的各类油液通过混溶、竞争性吸附等作用增强了PAHs垂向迁移能力,并致使深部包气带受到污染.地表0～1 m土壤受人为扰动、降雨淋滤、降解作用,30 m以下岩层受到地下水溶滤作用,导致低环/高环比例随深度增加呈现先升高后降低的趋势.污染来源、包气带理化指标及水文地质条件等共同作用控制PAHs垂向分布及迁移.     

大气氮沉降对三峡库区消落带土壤呼吸的影响

以三峡库区消落带落干期土壤为研究对象,采用室内模拟培养的方法,探讨了大气氮沉降通量及其组成对土壤呼吸的影响.结果表明,土壤呼吸速率对氮添加的响应为短期效应.1倍当前大气氮沉降添加下,无机氮和有机氮对土壤累积CO₂释放分别表现为无影响和抑制作用.除NH₄⁺-N在2倍氮沉降添加下表现为抑制作用外,2、3倍氮沉降添加均促进了土壤累积CO₂释放.与硝态氮相比,2、3倍氮沉降添加的铵态氮对土壤累积CO₂释放具有抑制作用.     

饱和多孔介质中DNAPL污染源区结构及质量溶出

为探究重非水相液体（DNAPL）在地下水中的运移和溶出行为,选取四氯乙烯（PCE）为代表,采用透射光法动态监测PCE在二维砂箱中的运移和分布,并以顶空气相色谱法监测其质量溶出,在此基础上通过乙醇冲洗来改变PCE分布,对比分析相应源区结构和溶出浓度的变化.结果表明：PCE的运移以垂向入渗为主,并伴随由毛细管力引起的横向迁移;污染源区面积和溶出浓度的变化具有明显一致性,均先迅速增大而后趋于平稳,由于泄露量小,70.7%的PCE以ganglia态残留在运移路径上.乙醇主要通过增溶作用改变污染源区结构,对PCE的空间展布影响弱,乙醇冲洗后ganglia态PCE占比增至99.6%,GTP值从2.4增至257.随着乙醇冲洗体积的增加,PCE源区面积从100cm²减至50cm²,对应溶出浓度从114mg/L减至12mg/L,二者呈较好的线性关系（R²=0.76）.此外,连续监测结果显示,在本研究的实验条件下,无论是否经过乙醇冲洗,PCE污染源区结构和其相应的质量溶出可以在一定时间内（至少16PVs）保持稳定.     

复杂DNAPL污染源区溶解相污染通量的升尺度计算

重非水相液体(DNAPL)污染场地中NAPL相污染物会持续溶解于地下水中,释放出溶解相污染羽,对人体健康产生威胁.准确评估DNAPL污染场地源区下游的溶解相污染通量至关重要.由于介质的非均质性常形成复杂DNAPL污染源区,其溶解相污染通量往往呈现出阶段性变化.目前溶解相污染通量计算普遍采用Christ等提出的双域升尺度模型,但该模型仅适用于弱非均质性的污染源区.本文基于大量强非均质性条件下的污染源区数值算例,修正了Christ双域模型中污染源区衰减指数的经验公式,将该模型的适用范围推广至强非均质性的复杂污染源区.通过蒙特卡罗数值算例及两个二维砂箱试验数据验证了修正模型的适用性和精度.对比结果表明:修正模型可广泛适用于不同结构的复杂DNAPL污染源区,与以往的计算方法相比,修正模型计算的溶解相污染通量精度提高了约35%.     

Theoretical evaluation of lower explosion limit of hybrid mixtures

Lower explosion limits of hybrid fuel mixtures are usually determined through time consuming and expensive experiments. Although, mathematical expressions like Le-Chatelier's Law and Bartknecht curve have been used by many researchers to predict the LEL of hybrid mixtures, significant deviations remain unexplained. This research work, presents a more sophisticated and general approach for the determination of LEL of hybrid mixtures.Assuming that the combustion kinetics of pure species are independent and unchanged by the presence of other combustible species, complete conversion of the reactants and no heat losses, a simple mathematical model has been derived from the enthalpy balance of the whole system. For the experimental validation of the modelled values, modified version of 20L sphere has been employed, following the European standard (EN 14034-3: 2011) as experimental protocol. Hybrid mixtures of three dusts with two gases were selected for the scope of this publication. By analyzing the modelled as well as the experimental values, it can be concluded that the LEL values of the individual components in the hybrid mixture set the upper and lower limit for the LEL of the hybrid mixture provided the total amount of fuel in the system is considered as the concentration of the hybrid mixture. Moreover, the amount of dust or gas required to render the hybrid mixture flammable mainly depends on the energy contribution upon combustion of the individual species to raise the temperature of the whole system from ambient to the flame temperature.Le-Chatelier's Law and Bartknecht curve are empirical relations, which might hold true for a first-order approximation of LEL of hybrid mixtures, but do not represent the most conservative values of LEL reported in literature. This implies that there is a non-zero probability of occurrence of an explosible mixture in the non-explosible concentrations ranges defined by these relations. Considering these arguments, the authors suggest to employ the model presented in this paper – which presents reasonably conservative values of LEL of hybrid mixtures – for theoretical calculation of LEL of hybrid mixtures, when no precise experimental data is available.