桂林市城区大气VOCs污染特征及对O3和SOA的生成潜势

对桂林市城区大气中挥发性有机物(VOCs)的污染特征,以及VOCs对臭氧(O3)和二次有机气溶胶(SOA)的生成潜势进行了研究。结果显示,研究期间,共检出VOCs物种78种,平均体积分数为21.32×10-9,表现为芳香烃(67.82%)烷烃(19.56%)卤代烃(7.50%)烯烃(2.86%)含氧挥发性有机物(1.41%)。VOCs体积分数空间分布呈现市中心和下风向郊区两个高值区。通过苯与甲苯的浓度比值发现,林科所VOCs主要来自交通源和生物源,师专甲山校区VOCs主要是来自交通源,其余测点VOCs主要来自交通源、工业源和外来传输源。分析乙苯和间/对二甲苯的浓度比值发现,电子科大尧山校区气团光化学年龄较大,光化学反应活性相对较强烈;旅游学院、华侨旅游经开区、大埠中心校气团光化学年龄较小,光化学反应活性相对较弱。VOCs对O3生成潜势最大的为芳香烃(93.81%),其次是烷烃(7.22%)和烯烃(4.75%);对SOA生成潜势最大的为芳香烃(97.45%),其次是烷烃(2.55%)。     

侧向风速作用下聚氨酯泡沫双火源火蔓延研究

为探究环境风作用下逆向双点火源聚氨酯泡沫火蔓延及融合行为，开展多组对照实验并从材料传热机理角度分析侧向风速对火蔓延行为中火羽流形态、质量损失和辐射热流场等特征参数的影响。结果表明:风速与上述参数之间存在非线性关系。环境风效应使火焰被拉长且敷贴于预热区表面，增大预热区面积和热反馈；侧向风速的增加对FPU板材质量损失的影响逐渐弱化，且板材的熔滴率与风速呈正相关；无论侧向风是否存在，两侧逆向火焰融合后均达到整个蔓延过程中的峰值温度；风速的存在限制了火焰温度与辐射热通量峰值，也缩短了温度和辐射峰值出现的时间。     

Explosion suppression of porous materials in a pipe-connected spherical vessel

To study the suppression of different porous materials on the explosion of combustible gas, some experiments were implemented. The porous materials were categorized into three kinds, including six subcategories, and the explosion suppression characteristics of the thin iron hoop, one-layer porous materials, two-layer composite porous materials, and three-layer composite porous materials were studied and analyzed. The results show that a rarefaction wave appears in the spherical vessel during the rapid development stage of combustion explosion. Further, the thin iron hoop could enhance the gas explosion intensity. And the explosion intensity suppression effect of the porous materials is obvious, the best effects of one-layer, two-layer and three-layer porous materials are from Fe–Ni 10 mm/40 PPI, Fe–Ni 10 mm/90 PPI + Al₂O₃ 10 mm/30 PPI, and Al₂O₃ 10 mm/50 PPI + Fe–Ni 10 mm/40 PPI + SiC 20 mm/20 PPI, respectively. According to the surface morphology of the porous materials, the anti-sintering ability of the three categories of porous materials follows the order of Al₂O₃ > SiC > Fe–Ni. Besides, the thickness and pore size of the combined porous material was changed, which has a great influence on the explosion pressure and the explosion intensity.     

The role of agri‐environment schemes in conservation and environmental management

Over half of the European landscape is under agricultural management and has been for millennia. Many species and ecosystems of conservation concern in Europe depend on agricultural management and are showing ongoing declines. Agri‐environment schemes (AES) are designed partly to address this. They are a major source of nature conservation funding within the European Union (EU) and the highest conservation expenditure in Europe. We reviewed the structure of current AES across Europe. Since a 2003 review questioned the overall effectiveness of AES for biodiversity, there has been a plethora of case studies and meta‐analyses examining their effectiveness. Most syntheses demonstrate general increases in farmland biodiversity in response to AES, with the size of the effect depending on the structure and management of the surrounding landscape. This is important in the light of successive EU enlargement and ongoing reforms of AES. We examined the change in effect size over time by merging the data sets of 3 recent meta‐analyses and found that schemes implemented after revision of the EU's agri‐environmental programs in 2007 were not more effective than schemes implemented before revision. Furthermore, schemes aimed at areas out of production (such as field margins and hedgerows) are more effective at enhancing species richness than those aimed at productive areas (such as arable crops or grasslands). Outstanding research questions include whether AES enhance ecosystem services, whether they are more effective in agriculturally marginal areas than in intensively farmed areas, whether they are more or less cost‐effective for farmland biodiversity than protected areas, and how much their effectiveness is influenced by farmer training and advice? The general lesson from the European experience is that AES can be effective for conserving wildlife on farmland, but they are expensive and need to be carefully designed and targeted.     

A method to estimate the impact of clear-cutting on nutrient concentrations in boreal headwater streams

Large-scale forestry operations, like clear-cutting, may impair surface water quality if not done with environmental considerations in mind. Catchment and country level estimates of nutrient loads from forestry are generally based on specific export values, i.e., changes in annual exports due to the implemented forestry operations expressed in kg ha⁻¹. We introduce here a specific concentration approach as a method to estimate the impact of clear-cutting on nutrient concentrations and export in headwater streams. This new method is potentially a more dynamic and flexible tool to estimate nutrient loads caused by forestry, because variation in annual runoff can be taken into account in load assessments. We combined water quality data from eight boreal headwater catchment pairs located in Finland and Sweden, where the effect of clear-cutting on stream water quality has been studied experimentally. Statistically significant specific concentration values could be produced for total nitrogen, nitrate, ammonium, and phosphate. The significant increases in the concentrations of these nutrients occurred between 2 and 6 years after clear-cutting. Significant specific concentration values could not be produced for total phosphorus and total organic carbon with the whole dataset, although in some single studies significant increases in their concentrations after clear-cutting were observed. The presented method enables taking into account variation in runoff, temporal dynamics of effects, and the proportional size of the treated area in load calculations. The number of existing studies considering large site-specific variation in responses to clear-cutting is small, and therefore further empirical studies are needed to improve predictive capabilities of the specific concentration values.     

过硫酸盐缓释材料释放过程模型构建

为预测评估过硫酸盐缓释材料的释放性能,对释放过程模型的构建以及模型的验证进行了研究。借助微积分思想,从材料体的概化分割、初始条件设定、每个小单元的状态标定、各个小单元中过硫酸钾的迁移变化量以及材料最外层释放过硫酸盐的量5个方面构建过硫酸盐缓释材料释放模型,利用Excel-VBA编程实现其释放过程模拟。采用欧盟标准NEN7375测试过硫酸盐缓释材料释放性能并获得模型参数。通过输入相关模型参数得到过硫酸盐动态迁移过程及其释放特征曲线,并利用实测数据与模拟数据进行拟合校验。结果表明,模型模拟值与实测值拟合较好,平均误差为1.88%,表明该模型设计合理,能够准确模拟过硫酸盐缓释材料释放过程,可作为缓释材料优化设计工具。     

快腐剂对畜禽粪便堆肥过程中腐熟度的影响

以牛粪、菌糠和鸡粪等为材料按照两种比例调配为混合基质,在添加或不添加快腐剂的条件下在发酵桶中进行为期38 d的堆肥发酵实验,通过对发酵产物的温度、p H值、总有机碳、C/N、硝铵态氮含量和种子发芽指数等指标变化的研究,揭示了快腐剂对发酵过程的影响。结果表明,虽然快腐剂对有机物料的温度、C/N比无显著的影响,但可以促进铵态氮向硝态氮的转化,在16 d时使发酵产物NH+4-N/NO-3-N比值降为0.15,达到腐熟标准(0.16);提升种子发芽指数,在腐解29 d时使种子发芽指数达到82.76%,达到完全腐熟指标(0.8),比不添加快腐剂的处理提前了4 d左右。快腐剂的作用效果受腐解物料配比的影响。     

高岭土对不同污染物微滤过程的影响

本研究采用原子力显微镜(AFM)结合自制的膜探针以及Zeta电位仪通过分别测量不同有机污染物,即腐殖酸(HA)、牛血清蛋白(BSA)和海藻酸钠(SA)与微滤膜之间的粘附力以及相应污染物的Zeta电位,对高岭土在不同有机物微滤过程的影响进行了系统性研究。结果表明,高岭土对污染膜通量衰减的影响主要发生在膜过滤的初期阶段,其存在使HA污染膜的初期通量衰减幅度增加,BSA和SA污染膜的初期通量衰减幅度减缓;清洗后HA污染膜的通量恢复率降低,而BSA和SA污染膜的通量恢复率增大。而且,高岭土的存在使膜-HA之间的粘附力变大以及HA溶液的Zeta电位变小,膜-BSA、SA之间的粘附力变小以及相应污染物的Zeta电位都增大。因此,膜-污染物之间粘附力以及溶液的Zeta电位的变化可以指示膜污染的变化趋势。     

Effects of organic matter on Leymus chinensis germination,growth, and urease activity and available nitrogen in coastal saline soil

ABSTRACT

The present study was carried out to investigate the effect of three organic matters (stalk powder, microbial fertilizer, and manure) on Leymus chinensis germination, growth, and urease activity and available nitrogen (N) in coastal saline soil. The study was conducted in a completely randomized design with eight treatments: J₀V₀Y₀, J₁V₀Y₀, J₀V₁Y₀, J₀V₀Y₁, J₁V₁Y₀, J₁V₀Y₁, J₀V₁Y₁, J₁V₁Y₁. The notations were based on the quantities of each agent added to 1 kg of coastal saline soil: J₀ – no straw powder, J₁ – 0.2 kg straw powder, Y₀ – no manure, Y₁ – 0.3 kg manure, V₀ – no microbial fertilizer, V₁ – 0.2 L microbial fertilizer, each in quantic repeat. L. chinensis was sown as 50 seeds per pot. Results indicated that addition of organic agents exerted a significantly enhanced germination, increase in fresh weight and elevated soil urease activity. Soil available N levels were significantly positively correlated with soil urease activity and fresh weight, but not with germination rate. It is noteworthy that the halophyte L. chinensis showed improved characteristics when grown in coastal saline soil with addition of organic amendments.     

The determination and matching analysis of pinch point temperature difference in evaporator and condenser of organic rankine cycle for mixed working fluid

Exergo-economic analysis of the pinch point temperature difference (PPTD) in both evaporator and condenser of sub-critical organic Rankine cycle system (ORCs) are performed based on the first and second laws of thermodynamics. Taking mixture R13I1/R601a as a working fluid and the annual total cost per net output power Z as exergo-economic performance evaluation criterion, the effects of PPTD in evaporator ΔT_e, and the PPTD ratio of condenser to evaporator y, on the exergo-economic performance of ORCs are analyzed. Moreover, how some other parameters influence the optimal PPTD in evaporator ΔT_e,opt and the optimal PPTD ratio of condenser to evaporator y_opt are also discussed. It has been found that the exergo-economic performance of ORCs is remarkably influenced by ΔT_e and y, and there exists ΔT_e,opt and y_opt. In addition, ΔT_e,opt and y_opt are affected by heat transfer coefficient ratio of condenser to evaporator ß, the temperature of working fluid at dew point in condenser T_1a, and composition of R13I1/R601a: larger ß and T_1a lead to lower ΔT_e,opt and y_opt; by contraries, larger mass fraction of R13I1 makes ΔT_e,opt and y_opt increase, and y_opt increases linearly. The effects of the temperature of working fluid at bubble point in evaporator T_3a, mass flow rate of exhaust flue gas m_g, and inlet temperature of exhaust flue gas T_gi on ΔT_e,opt and y_opt are very slight. For comparison, three additional working fluids, namely R601a, R245fa, and 0.32R245fa/0.68R601a, are also taken into account.