Concentrations and chemical compositions of PM10 during hazy and non-hazy days in Beijing

In order to study the concentrations of major components,characteristics and comparison in hazy and non-hazy days of PM_(10) in Beijing,aerosol samples were collected at urban site in Beijing from December 29,2014 to January 22,2015.Heavy metals like Zn,Pb,Mn,Cu,As,V,Cr and Cd were deeply studied considering their toxic effects on human being;nine water-soluble inorganic ions(SO_4~(2-),NO_3~-,NH_4~+,Na~+,K~+,Cl~-,Ca~(2+) and Mg~(2+)) and carbon fractions(OC and EC) were also analyzed.The concentrations of heavy metals were 1.03–1.98 times higher in hazy days than those in non-hazy days,mainly due to biomass burning and coal burning.The trends in total heavy metals concentrations were basically consistent with the trends in PM concentrations except for two obvious periods(12.29–12.30;1.14–1.15);but when air masses accumulated locally or around Beijing,trends in PM concentrations and heavy metals were opposite.The proportion for NO_3~-/SO_4~(2-) indicated that mobile sources such as automobiles were important reasons for haze in Beijing.Correlation between OC and EC during non-hazy days was strong(R~2= 0.95) but it was low(R~2= 0.67) during hazy days,and large variations for OC/EC values occurred in hazy days.The calculated mass concentration of SOC is 2.58 μg/m~3,which only accounted for 10.1% of the OC concentration.When air masses from the far north-west,they decreased PM concentration in Beijing and they were relatively clean;however,those from the near east,south-east and south of the mainland increased PM concentration and they were dirty.     

轻质高强多功能点阵夹层结构研究进展

根据材料类型和点阵结构,对点阵夹层结构进行了分类简述,并从静态、动态力学性能上,分析了各类点阵夹层结构的优缺点。简要叙述了设计过程中,综合考虑材料、结构以及功能等影响因素,针对不同使用工况的要求,可对各影响因素进行匹配设计,以实现传热特性、电磁波屏蔽特性、声学特性等不同的功能性需求。然后介绍了复合点阵夹层结构(嵌锁组装、模具热压成形、穿插编织)和金属点阵夹层结构(冲压成形、挤压线切割、拉伸网折叠、搭接拼装、熔模铸造以及增材制造)的主要制造工艺。最后提出如何将设计因子与多目标进行匹配及优化设计,是轻质高强点阵夹层结构的重点研究方向,轻质高强点阵夹层结构将朝多材料及多结构复合方向发展,开发新的制造工艺,提高费效比,是点阵夹层结构材料需解决的问题。     

内饰材料发射率对密封舱室热防护效率的影响

目的探究密封舱室热防护效率与其内饰材料表面发射率的关系,分析内饰材料发射率对其表面温度、舱室内温度的影响规律。方法采用自行设计的小型密封舱室和加热测量装置,对内饰材料表面及舱室内温度进行测量。结果当内饰材料发射率为0.09时,内饰表面温度为141.2℃,舱室内平均温度仅为90.8℃;内饰材料发射率为0.91时,内饰表面温度为124.4℃,舱室内平均温度为109.1℃。结论试样表面温度随材料发射率的提高而降低,舱室内部空气平均温度随材料发射率的提高而升高;试样表面温度与舱室空气平均温度的温度差随材料发射率的提高而减小;同时,相同试样表面温度与舱室平均温度的温度差随加热温度的提高而增加。     

京津冀西北典型流域地下水化学特征及补给源分析

为揭示京津冀西北典型流域地下水循环特征,运用环境同位素和水化学技术等方法分析张家口市不同流域水体氢氧同位素特征、水化学特征及时空变化特征、地表地下水转化关系。结果表明：地表水化学类型主要为HCO₃-Mg·Na和HCO₃·Cl-Na型;地下水化学类型不同时期表现出不同的类型,水化学类型更为多样,主要以HCO₃-Mg·Na型、HCO₃·Cl-Na型、HCO₃·Cl-Na·Mg为主。地表河水和地下水中离子均主要来源于岩石风化作用;张北和桑干河流域地下水中离子偏向于蒸发浓缩作用控制。张家口市各流域地表地下水δ¹⁸O、δD组成较为接近,表明了当地地表水和地下水均受到大气降水的补给。大气降水和地表河水对地下水的补给比例均值分别为37.74%和62.26%,以地表河水的补给为主要方式。     

京津冀地区钢铁行业协同减排成本-效益分析

京津冀地区是我国钢铁行业布局最集中的区域,也是大气污染治理的重点区域之一.分析京津冀地区钢铁行业各类治污手段中长期减排的成本-效益,对于选择最经济有效的减排路径、加快推动该地区大气环境质量达标意义重大.基于能源环境、环境分布、人群健康效益评价等模块构建多模型耦合方法,以2015年为基准年,以每5 a为时间节点,设计了京津冀地区钢铁行业规模-结构、规模-技术、规模-末端治理、综合减排4种协同减排情景,计算各情景下2015—2030年京津冀地区钢铁行业主要污染物(SO₂、NO_x、PM₁₀、PM_2.5、CO₂)的减排成本与效益,比较获取治污减排的最优路径方案.结果表明:①基于减排成本计算,规模-末端治理减排情景成本最低,分别为规模-结构、规模-技术减排情景投入的15.18%、23.94%;综合减排情景下治污减排潜力最大,但综合成本最高.②基于环境税效益评价方法、人群健康效益评价方法计算显示,人群健康效益评价方法计算的减排效益高于环境税效益评价方法,表明污染减排的潜在人群健康效益更高;基于两种减排效益方法,4种协同减排情景中综合减排效益分别为10.78×108、76.14×108元,高于规模-结构、规模-技术、规模-末端治理减排情景效益.③基于环境税效益评价方法,4种协同减排情景的效益-成本比表现为规模-末端治理减排情景(0.46) >规模-技术减排情景(0.24) >综合减排情景(0.15) >规模-结构减排情景(0.10);基于人群健康效益评价方法4种协同减排情景的效益-成本比依次为规模-末端治理减排情景(8.35) >综合减排情景(1.07) >规模-结构减排情景(0.57) >规模-技术减排情景(0.65),表明规模-末端治理减排情景的减排路径最优.研究显示,京津冀地区钢铁行业应基于环境质量底线目标要求,综合考虑减排潜力、减排成本与收益,以规模-末端治理为主要途径,选取协同减排的最优路径.      

黄河流域水污染排放特征及污染集聚格局分析

掌握污染源排放特征及其空间差异,是在流域尺度提升水污染治理水平的重要基础.该研究分别从污染源的活动水平（简称“活动水平”）、污染物产生、污染物去除和污染物排放4个方面选取了28个指标,对黄河流域60个市州主要水污染物排放特征开展了现状评价和聚类分析.采用污染分布的地理集中度指数表征各市州污染集聚格局,并利用空间分析模型Global Moran's I和G_i*指数判断污染排放的空间集聚趋势与冷热点地区.结果表明:按照水污染排放特征的差异,黄河流域不同地区在水污染格局上可划分为高排放强度区、高排放绩效区、污染集聚区和低排放绩效区;水污染物排放与经济发展格局分布一致,上游、中游到下游地区呈现明显的阶梯型分布,上游地区单位水资源利用效率和排放绩效低,下游地区区域性污染集聚效应明显;山西省、河南省和山东省沿黄城市在空间上表现为区域性连片污染集聚,集中分布在晋中城市群和中原城市群.针对当前黄河流域水污染排放特征和空间集聚格局,建议制定统一的生态环境保护与治理策略,加强中下游城市群的污染协同控制.      

Adjusting sowing date and cultivar shift improve maize adaption to climate change in China

Mitigation and Adaptation Strategies for Global Change - This study investigates the impact of climate change on spring and summer maize (Zea mays) yield and evaluates several adaptation measures...     

MgO低温催化臭氧降解氨氮的机制研究

研究了低温条件下单独臭氧及MgO催化臭氧化降解水中氨氮的效率和特征,并对其反应机制分别进行了探讨.结果表明,pH是影响臭氧和催化臭氧化除氨的重要因素,不仅影响溶液中NH_3与NH~+_4的比例和臭氧氧化氨氮的速率,还影响氧化产物种类,从而影响脱氮效果.10℃时,单独臭氧对水中氨氮的氧化降解效率随pH的升高而增大,pH≤9时整体降解效率不高,pH=9时仅为16.39%,而pH=10时达到41.77%.臭氧和·OH共同参与降解氨氮的过程.单独臭氧氧化氨氮生成氮气的选择性具有pH依赖性,并与Cl~-密切相关.pH低(≤9)时,氨氮多以NH~+_4形态存在,O_3与Cl~-反应生成ClO~-_x(x=1、3),再氧化NH~+_4,从而生成气态产物N_2或N_2O.MgO在低温条件下具有很强的催化臭氧化降解氨氮的能力且温度升高有利于反应的进行,0、10、20℃时,MgO催化臭氧化氨氮的效率分别为77.53%、80.17%、91.26%.此过程中,·OH参与反应的程度低,一部分氨氮降解依靠ClO~-_x氧化NH~+_4,而氨氮降解的主要途径为O_3对NH_3的直接氧化.     

基于高精度清单的京津冀机动车控污政策研究

为研究京津冀机动车污染控制政策对CO、HC、NO_x、PM_2.5、PM₁₀等污染物的减排效果,建立了2014年高精度机动车排放清单,选取过去已经实施,未来规划实施及优化/劣化后的若干政策,设置4类共13种政策情景,与实际清单基准情景进行对比,识别各政策情景的排放变化,并对其中由政府给予补贴的政策进行成本收益核算.结果显示,淘汰低排放标准机动车带来的污染减排效果最好,在天津和河北对CO和HC的排放削减分别为53.19%,49.75%和51.28%,50.87%,达半数及以上;升级机动车发动机和燃油标准也能显著削减排放,在天津和河北对PM_2.5、PM₁₀的削减分别为17.01%,17.00%和21.95%,21.93%.政府补贴政策存在明显边际效应特征,排放标准高,重污染车少的北京单位成本的减排收益明显低于天津和河北,.河北和天津在考虑成本因素的基础上,应当逐步采纳北京的高标准减排政策;北京则可在一定条件下,将一部分低效的政府补贴通过合理方式转移支付给天津和河北,以提高政府投入的减排效率.     

Potential of secondary aerosol formation from Chinese gasoline engine exhaust

Light-duty gasoline vehicles have drawn public attention in China due to their significant primary emissions of particulate matter and volatile organic compounds(VOCs). However,little information on secondary aerosol formation from exhaust for Chinese vehicles and fuel conditions is available. In this study, chamber experiments were conducted to quantify the potential of secondary aerosol formation from the exhaust of a port fuel injection gasoline engine. The engine and fuel used are common in the Chinese market, and the fuel satisfies the China V gasoline fuel standard. Substantial secondary aerosol formation was observed during a 4–5 hr simulation, which was estimated to represent more than 10 days of equivalent atmospheric photo-oxidation in Beijing. As a consequence, the extreme case secondary organic aerosol(SOA) production was 426 ± 85 mg/kg-fuel, with high levels of precursors and OH exposure. The low hygroscopicity of the aerosols formed inside the chamber suggests that SOA was the dominant chemical composition. Fourteen percent of SOA measured in the chamber experiments could be explained through the oxidation of speciated single-ring aromatics. Unspeciated precursors, such as intermediate-volatility organic compounds and semi-volatile organic compounds, might be significant for SOA formation from gasoline VOCs. We concluded that reductions of emissions of aerosol precursor gases from vehicles are essential to mediate pollution in China.